Modulation of AKAP12 signalosome

Abstract

Described herein are compositions and methods for maintaining or rescuing cardiac function in a cell or a subject. Also described herein are compositions and methods for treating or preventing cardiovascular disease in a subject. In some embodiments, the compositions and methods comprise a therapeutic agent targeting AKAP12, PDE8, or a combination thereof. In some embodiments, the therapeutic agent modulates or inhibits the expression and / or activity of AKAP12, PDE8, or a combination thereof in a cell or a subject. In some embodiments, the therapeutic agent targets both AKAP12 and PDE8.

Description

[0001] MODULATION OF AKAP12 SIGNALOSOME CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No.63 / 621,310, filed January 16, 2024, which is incorporated by reference herein in its entirety. FEDERALLY SPONSORED RESEARCH This invention was made with government support under grant number HL141963 awarded by the National Institutes of Health. The government has certain rights in the invention. REFERENCE TO SEQUENCE LISTING This application was filed with a Sequence Listing XML in ST.26 XML format accordance with 37 C.F.R § 1.831 and PCT Rule 13ter. The Sequence Listing XML file submitted in the USPTO Patent Center, “891014-0002-WO01_sequence_listing_xml_13-JAN-2025.xml,” was created on January 13, 2025, contains 60 sequences, has a file size of 56.0 kilobytes (57,344 bytes), and is incorporated by reference in its entirety into the specification. BACKGROUND Heart failure (HF) is a chronic disease in which the heart cannot pump enough blood to meet the body’s demands. This impaired pumping of blood is due to insufficient contraction, which is highly regulated by G-Protein Coupled Receptors (GPCRs); -Adrenergic Receptors( ARs). Downstream of ARs, cAMP is a second messenger that plays a major role in cardiacexcitation-contraction (EC) coupling. The intracellular levels of cAMP are finely tuned based on the activities of adenylyl cyclases (AC; enzymes that increase cAMP levels) and phosphodiesterases (PDEs; enzymes that reduce cAMP levels). To further ensure a more specific cellular response to distinct stimuli, spatial and temporal localization of cAMP is associated with A-kinase anchoring proteins (AKAPs). AKAPs belong to a family of scaffolding proteins that organize complex signal transduction events from the cell membrane stimulated receptors through recruiting protein kinases, phosphatases, and other signal regulation molecules. The structural diversity of AKAPs dictates their scaffolding partners. However, all AKAPs have a highly conserved binding domain associated with the regulatory subunit of protein kinase A (PKA). So far, several AKAPs have been characterized in the heart, and are associated with cardiac contractility, development, and hypertrophy. Two AKAPs are known to bind directly to 2AR in the heart, namely AKAP5 and AKAP12 (also known as “Gravin”). The role of AKAP5 in cardiac function has previously been delineated, where AKAP5 was found to be required for sympathetic stimulation of the calcium transient in cardiomyocytes through scaffolding caveolin-3. On the other hand, the importance of AKAP12 and the AKAP12 signalosome in cardiac function remains unclear. What is needed are new compositions and methods for modulating the AKAP12 signalosome. Such compositions and methods would be useful in a variety of research and clinical applications related to cardiac function and cardiovascular disease. SUMMARY One embodiment described herein is a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. In one aspect, the therapeutic agent modulates expression and / or activity of AKAP12 and PDE8 in the cell or the subject. In another aspect, the therapeutic agent inhibits expression and / or activity of AKAP12 and PDE8 in the cell or the subject. In another aspect, PDE8 is PDE8A. In another aspect, the therapeutic agent comprises a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof. In another aspect, the therapeutic agent is a nucleic acid comprising a siRNA, a shRNA, or an antisense oligonucleotide. In another aspect, the therapeutic agent is a cardiac-specific therapeutic agent. In another aspect, the pharmaceutical composition further comprises one or more pharmaceutically acceptable buffers, salts, carriers, or diluents. Another embodiment described herein is a kit comprising: a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8; and optionally, one or more of packaging, a label, or instructions for use. Another embodiment described herein is a method of maintaining or rescuing cardiac function in a cell or a subject, the method comprising: administering to the cell or the subject a therapeutically effective amount of a pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. In one aspect, the cell or the subject has increased expression of AKAP12 relative to a control cell or subject. In another aspect, the subject has, or is at risk of developing, heart failure. In another aspect, the method maintains or rescues cardiac contractility in the cell or the subject. Another embodiment described herein is a method of treating or preventing cardiovascular disease in a subject, the method comprising: administering to the subject a therapeutically effective amount of a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. In one aspect, the subject has increased expression of AKAP12 relative to a control subject. In another aspect, the subject has, or is at risk of developing, heart failure. In another aspect, the method maintains or rescues cardiac contractility in the subject. Another embodiment described herein is the use of a pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8 as a medicament for maintaining or rescuing cardiac function in a cell or a subject. Another embodiment described herein is the use of a pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8 as a medicament for treating or preventing cardiovascular disease in a subject. DESCRIPTION OF THE DRAWINGS The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. FIG.1 shows a schematic of the animal grouping method. FIG.2 shows a schematic of the subcutaneous osmotic pump insertion procedure. FIG.3 shows a schematic of the calcium and contractility experiments using the IonOptix MultiCell Lite System. FIG. 4A–H shows that AKAP12 upregulation in vitro reduces intracellular cAMP levels. FIG.4A shows RTqPCR quantitative analysis of AKAP12 gene expression in AC16 cells stably transfected with human AKAP12 plasmid (AKAP12-OX) (Hygromycin selection; Sino Biologicals, HG18215-UT) and non-transfected AC16 cells (Ctrl); n = 3 in each group. FIG. 4B shows representative western blot comparing AKAP12 expression in AC16 cells stably transfected with human AKAP12 plasmid (AKAP12-OX) and non-transfected AC16 cells (Ctrl). FIG. 4C shows quantification of AKAP12 protein expression using ImageLab, n = 3 in each group. Intracellular cAMP levels in AC16 cells were detected using the Glosensor Luciferase assay under different pre-treatments followed by 10 μM EPI: 10 μM EPI (FIG.4D), pre-treatment for 30 mins with 0.1 mM IBMX (FIG.4E), pre-treatment for 30 mins with 10 μM Rolipram (FIG.4G), or pre-treatment for 30 mins with 200 nM PF-04957325 (FIG.4H). FIG.4F shows the quantification of RTqPCR for PDEs in the AC16 cells. Data are represented as % intracellular cAMP (normalized data; each sub-column was normalized separately, with 0% defined as y = 0 and 100% defined as the maximum value identified in all sub-columns for that graph). The arrow indicates the start of EPI treatment or vehicle (Optimem) addition. Veh: Vehicle, EPI: Epinephrine. All data represented as average Mean ± S.E.M.; FIG.4D–E, n = 6; FIG.4G–H, n = 3. All experiments were performed as technical duplicates. Data were determined to have a parametric distribution by the Shapiro- Wilk test and were analyzed using an unpaired 2-tailed Student t-test at the point of max response for all panels except FIG.4G. Data in FIG.4G had a nonparametric distribution, and data were compared with the Mann-Whitney U test, at the point of max response. The point of max response has black borders. FIG.5A–D shows reduced intracellular cAMP levels in the AKAP12-OX group are not dueto impaired G s pathway or higher G i pathway activity. FIG.5A shows that G s pathway activitywas assessed using Forskolin (FSK) 25 M, showing a significantly lower response in the AKAP12-OX group as compared to controls. FIG.5B shows pre-treatment with Pertussis Toxin(overnight), a G i inhibitor, showed significantly lower intracellular cAMP levels in AKAP12-OXAC16 cells as compared to controls; cells were normalized to the vehicle. FIG.5C shows westernblots of G i protein expression level in AKAP12-OX AC16 cells and controls treated with 10 MEpinephrine (Epi; Sigma Aldrich, E4250-10G); non-selective ARs. FIG.5D shows pre-treatment with 10 M IBMX for 30 minutes showed significantly lower intracellular cAMP levels in AKAP12- OX AC16 cells as compared to controls. All data represented as average Mean ± S.E.M. FIG. 5A; N = 5, FIG.5B; N = 3, FIG.5D; N = 5. All experiments were performed as technical duplicates. Data were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using an unpaired 2-tailed Student t-test at the point of max response for FIG.5A–B. Data in FIG.5D had a nonparametric distribution, and was compared with the Mann-Whitney U test, at the point of max response. The point of max response has black borders. The arrow indicates the start of EPI treatment or vehicle (Optimem) addition. Veh: Vehicle; EPI: Epinephrine. FIG.6A–F shows that PDE8A is in the vicinity of the AKAP12 signalosome in primary adult cardiomyocytes. FIG. 6A shows a representative western blot of LV extracts from mice overexpressing AKAP12 (AKAP12OX) compared to Wild Type littermates (WTs). FIG.6B shows quantification of AKAP12 protein levels using ImageLab, n = 4 in each group. FIG.6C–D shows an ELISA assay comparing baseline cAMP levels in primary cardiomyocytes extracted from LVs of AKAP12OXmale and female mice respectively compared to WTs, n = 3 in each group. FIG.6E shows cardiomyocytes representative immunocytochemistry images of primary adult and their scatter plot for colocalization using Pearson’s R test. FIG. 6F shows quantification of PDE8A colocalization with AKAP12 in the absence of ISO; n = 24 WT, n = 7 AKAP12OXand in the presence of ISO; n = 26 WT and n = 8 AKAP12OX. All data represented as average Mean ± S.E.M. Data were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using unpaired 2-tailed Student t-test for all panels except for the AKAP12OXgroup in FIG.6F, which had a nonparametric distribution, and data were compared within the AKAP12OXgroup using the Mann-Whitney U test. NG = Negative controls. FIG.7A–E show AKAP12OXin mouse hearts upregulates PDE8A gene expression without affecting PDE8A protein expression levels. FIG.7A–B shows quantification of gene expression levels from RTqPCR data of several PDEs and ACs in AKAP12OXand WT males, n = 4 in each group. FIG. 7B shows quantification of gene expression levels from RTqPCR data of several PDEs and ACs in AKAP12OXand WT males, n = 4 in each group. FIG.7C shows a heat map of PDE gene expression (average fold change), assessed in LV extracts from AKAP12OXand WT male and female mice (8–12 weeks old) in the absence of ISO treatment (Sham) and after 14 days post-ISO treatment (ISO); n = 3 in each group. FIG. 7D shows a representative PDE8A western blot from LV extracts from WT and AKAP12OXmice. FIG. 7E shows quantification of PDE8A protein levels using ImageLab; fold change. All data represented as average Mean ± S.E.M. Data were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using unpaired 2-tailed Student t-test for FIG.7A–B, except FIG.7A; PDE8A group had nonparametric distribution, and data were compared with the Mann-Whitney U test. In FIG.7A– B, gene expression was normalized to RPL4 and yellow rectangles are excluded outliers, detected using the ROUT method; Q = 2%. 2-way ANOVA followed by Tukey multiple comparisons post hoc test was used to compare data in FIG.7E. FIG. 8A–B shows cardiac AKAP12OXdoes not affect the phosphorylation of cardiac troponin-I. FIG.8A shows total troponin (cTnI) and phospho-troponin-I (P-cTnI) expression levels in left ventricular extracts from AKAP12OXand WT male and female mice; sham (no ISO treatment) vs. ISO (60 mg / kg / day for 14 days). FIG. 8B shows the quantification of analysis of (P-cTnI) represented as the ratio of P-cTnI / cTnI after normalizing each protein to the total protein for each blot. All data represented as average Mean ± S.E.M. n = 3 in each group. Statistical analysis was performed using 2-way ANOVA followed by Tukey multiple comparisons post hoc test. FIG. 9A–P shows overexpressing AKAP12 in cardiomyocytes reduces their contractility post acute ISO treatment. FIG.9A shows average tracings of sarcomere length from all primary adult cardiomyocytes isolated from male mice (8–12 weeks old) and treated acutely with ISO. FIG. 9B–H shows quantification of contractility parameters using CytoSolver 3.0 among the AKAP12OXand WT males, n = 47 in WT and n = 12 in AKAP12OX. Comparison of paced cellparameters measured in FIG. 9B–H includes diastolic sarcomere length ( m), systolic sarcomerelength, sarcomere shortening (%), contraction velocity ( m / sec), time to 90% peak (sec),relaxation velocity ( m / sec), and time to 90% baseline (sec). FIG. 9I shows average tracings of sarcomere length from all primary adult cardiomyocytes isolated from female mice (8–12 weeks old) and treated acutely with ISO. FIG. 9J–P show quantification of contractility parameters among the AKAP12OXand WT females, n = 40 in WT and n = 26 in AKAP12OX. Comparison ofpaced cell parameters measured in FIG. 9J–P includes diastolic sarcomere length ( m), systolicsarcomere length, sarcomere shortening (%), contraction velocity ( m / sec), time to 90% peak(sec), relaxation velocity ( m / sec), and time to 90% baseline (sec). All data are represented asaverage Mean ± S.E.M. Data in FIG.9E, 9K, 9L, and 9N were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using an unpaired 2-tailed Student t-test. Data in FIG. 9C, D, G, M, and O had nonparametric distribution, and data were compared with the Mann-Whitney U test. Cells were isolated from 3–4 mice / group and experiments were performed immediately after cell isolation at 37 °C using perfusion. FIG. 10A–P show overexpressing AKAP12 in primary adult cardiomyocytes does not affect sarcomere shortening (%) at basal levels. FIG.10A shows average tracings of sarcomere length from all primary adult cardiomyocytes isolated from male mice (8–12 weeks old) and treated acutely with ISO. FIG. 10B–H shows quantification of contractility parameters using CytoSolver 3.0 among the AKAP12OXand WT males, n = 50 in WT and n = 21 in AKAP12OX. Comparison of paced cell parameters measured in FIG. 10B–H includes diastolic sarcomerelength ( m), systolic sarcomere length, sarcomere shortening (%), contraction velocity ( m / sec),time to 90% peak (sec), relaxation velocity ( m / sec), and time to 90% baseline (sec). FIG. 10Ishows average tracings of sarcomere length from all primary adult cardiomyocytes isolated from female mice (8–12 weeks old) and treated acutely with ISO. FIG.10J–P show quantification of contractility parameters among the AKAP12OXand WT females, n = 50–56 in WT and n = 60–61 in AKAP12OX. Comparison of paced cell parameters measured in FIG.10J–P includes diastolicsarcomere length ( m), systolic sarcomere length, sarcomere shortening (%), contraction velocity( m / sec), time to 90% peak (sec), relaxation velocity ( m / sec), and time to 90% baseline (sec).All data represented as average Mean ± S.E.M. Data in FIG. 10F, 10J, 10K, and 10N were determined to have a nonparametric distribution by the Shapiro-Wilk test and were compared with the Mann-Whitney U test. Cells were isolated from 3–4 mice / group and experiments were performed immediately after cell isolation at 37 °C using perfusion. FIG.11A–N show overexpressing AKAP12 in primary adult cardiomyocytes significantly increases intracellular calcium post-ISO treatment. FIG. 11A shows average tracings of [Ca2+]irepresented by Fura-2 fluorescence ratio (340 nm / 380 nm) from all primary adult cardiomyocytes isolated from male mice (8–12 weeks old) and treated acutely with ISO. FIG. 11B–F show quantification of [Ca2+]iand calcium kinetics using CytoSolver 3.0 among the AKAP12OXand WT males; n = 50–54 in WT and n = 20–25 in AKAP12OX. Comparison of paced cell parameters measured in FIG. 11B–F includes diastolic [Ca2+]i(F340 / F380), systolic [Ca2+]i(F340 / F380), [Ca2+]ichange (%), time to 90% baseline (sec), and time to 90% peak (sec). FIG. 11G shows a correlation plot of [Ca2+]ichange (%) and sarcomere shortening (%). FIG. 11H shows average tracings of [Ca2+]irepresented by Fura-2 fluorescence ratio (340 nm / 380 nm) from all primary adult cardiomyocytes isolated from female mice (8–12 weeks old) and treated acutely with ISO. FIG. 11I–M show quantification of [Ca2+]iand calcium kinetics among the AKAP12OXand WT females; n = 50–59 in WT and n = 60–65 in AKAP12OX. Comparison of paced cell parameters measured in FIG. 11I–M includes diastolic [Ca2+]i(F340 / F380), systolic [Ca2+]i(F340 / F380), [Ca2+]ichange (%), time to 90% baseline (sec), and time to 90% peak (sec). FIG. 11N shows a correlation plot of [Ca2+]ichange (%) and sarcomere shortening (%). All data are represented as average Mean ± S.E.M. Data in FIG. 11C and 11J were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using an unpaired 2-tailed Student t-test. Data in FIG. 11B, 11E, 11F, and 11I had nonparametric distribution, and data were compared with the Mann-Whitney U test. Cells were isolated from 3–4 mice / group and experiments were performed immediately after cell isolation at 37 °C using perfusion. FIG.12A–N show overexpressing AKAP12 in primary adult cardiomyocytes significantly increases intracellular calcium at basal levels. FIG. 12A shows average tracings of [Ca2+]irepresented by Fura-2 fluorescence ratio (340 nm / 380 nm) from all primary adult cardiomyocytes isolated from male mice (8–12 weeks old) and treated acutely with ISO. FIG. 12B–F show quantification of [Ca2+]iand calcium kinetics using CytoSolver 3.0 among the AKAP12OXand WT males; n = 51 in WT and n = 26 in AKAP12OX. Comparison of paced cell parameters measured in FIG. 12B–F includes diastolic [Ca2+]i(F340 / F380), systolic [Ca2+]i(F340 / F380), [Ca2+]ichange (%), time to 90% baseline (sec), and time to 90% peak (sec). FIG.12G shows a correlation plot of [Ca2+]ichange (%) and sarcomere shortening (%). FIG. 12H shows average tracings of [Ca2+]irepresented by Fura-2 fluorescence ratio (340 nm / 380 nm) from all primary adult cardiomyocytes isolated from female mice (8–12 weeks old) and treated acutely with ISO. FIG. 12I–M show quantification of [Ca2+]iand calcium kinetics among the AKAP12OXand WT females; n = 50–55 in WT and n = 80–81 in AKAP12OX. Comparison of paced cell parameters measured in FIG.12I–M includes diastolic [Ca2+]i(F340 / F380), systolic [Ca2+]i(F340 / F380), [Ca2+]ichange (%), time to 90% baseline (sec), time to 90% peak (sec). FIG.12N shows a correlation plot of [Ca2+]ichange (%) and sarcomere shortening (%). All data represented as average Mean ± S.E.M. Data in FIG.12J was determined to have a parametric distribution by the Shapiro-Wilk test and was analyzed using the unpaired 2-tailed Student t-test. Data in FIG. 12B–D, 12I, and 12K had nonparametric distribution, and data were compared with the Mann-Whitney U test. Cells were isolated from 3– 4 mice / group and experiments were performed immediately after cell isolation at 37 °C using perfusion. FIG. 13A–L show adult primary cardiomyocytes from AKAP12OXmice have impaired contractility in response to higher intracellular calcium levels downstream of 2AR. FIG.13A–C show quantification of selective 1AR stimulation (50 nM ICI + 100 nM ISO) on cardiomyocytes calcium and contractility and their correlation among the AKAP12OXand WT males; n = 71 in WT and n = 9 in AKAP12OX. FIG.13D–F show quantification of selective 2AR stimulation (100 nM CGP + 100 nM ISO) on cardiomyocytes calcium and contractility and their correlation among the AKAP12OXand WT males; n = 48 in WT and n = 17 in AKAP12OX. FIG.13G–I show quantification of selective 1AR stimulation (50 nM ICI + 100 nM ISO) on cardiomyocytes calcium and contractility and their correlation among the AKAP12OXand WT females; n = 52 in WT and n = 18 in AKAP12OX. FIG.13J–L shows quantification of selective 2AR stimulation (100 nM CGP + 100 nM ISO) on cardiomyocytes calcium and contractility and their correlation among the AKAP12OXand WT females; n = 35 in WT and n = 19 in AKAP12OX. All data represented as average Mean ± S.E.M. Data were determined to have a nonparametric distribution by the Shapiro-Wilk test and were compared with the Mann-Whitney U test. Cells were isolated from 3–4 mice / group and experiments were performed immediately after cell isolation at 37 °C using perfusion. FIG. 14A–F show that the PDE8 inhibitor (PF-04957325) reverses the AKAP12OXeffect on [Ca2+]iand contractility in primary adult mice cardiomyocytes. FIG.14A–C shows quantification of the PDE8 inhibition effects on cardiomyocyte calcium and contractility and their correlation among the AKAP12OXand WT males; n = 35 in WT and n = 13 in AKAP12OX. FIG.14D–F shows quantification of the PDE8 inhibition effects on cardiomyocyte calcium and contractility and their correlation among the AKAP12OXand WT females; n = 29 in WT and n = 21 in AKAP12OX. When data were determined to have a parametric distribution by the Shapiro-Wilk test, AKAP12OXgroups in FIG.14B and 14D, 1-way ANOVA was used to assess data within each group. Other data with nonparametric distribution were compared within each group using the Friedman test. Mann-Whitney U test was used to compare PF-04957325 + ISO effects between groups in all panels, except FIG.14A (unpaired 2-tailed Student t-test). PF = PF-04957325. FIG. 15 shows cardiomyocytes AKAP12OXupregulates maladaptive genes in the left ventricle (LV). FIG.15 shows a heat map of maladaptive and adaptive gene expression (FPKM), assessed in LV extracts from AKAP12OXand WT male and female mice (8–12 weeks old) in the absence of ISO treatment (Sham) and after 14 days post-ISO treatment (ISO); n = 3 in each group. FIG.16 shows that cardiomyocytes AKAP12OXupregulate several maladaptive genes in the left ventricle post 14 days of ISO treatment. FIG.16 shows a heat map of maladaptive and adaptive gene expression (Average FPKM), assessed in LV extracts from AKAP12OXand WT male and female mice (8–12 weeks old) in the absence of ISO treatment (Sham) and after 14 days post-ISO treatment (ISO); n = 3 in each group. FIG. 17A–L shows cardiac AKAP12OXworsens systolic function and promotes left ventricular hypertrophy. FIG.17A–C shows echocardiographic measurements of systolic cardiac function before and after 14 days of ISO treatment in AKAP12OXand WT males (8–12 weeks old); n = 8 in WT and n = 6 in AKAP12OX. Comparison of parameters measured in FIG.17A–C includes ejection fraction (%), fractional shortening (%), and global circumferential strain (%); n = 5 in each group. FIG.17D shows LV hypertrophy measurement represented by LV mass / body weight ratio before and after ISO treatment; n = 6 in each group. FIG. 17E–G shows echocardiographic measurements of systolic cardiac function before and after 14 days of ISO treatment in AKAP12OXand WT females (8–12 weeks old); n = 8 in WT and n = 9 in AKAP12OX. Comparison of parameters measured in FIG.17E–G includes ejection fraction (%), fractional shortening (%), and global circumferential strain (%); n = 5 in each group. FIG. 17H shows LV hypertrophy measurement represented by LV mass / body weight ratio before and after ISO treatment; n = 8 in WT and n = 9 in AKAP12OX. FIG.17I shows representative immunocytochemistry images of WGA staining in cardiac slices before and after ISO treatment to assess cardiac hypertrophy through a cross-sectional area. FIG. 17J–K shows quantification of the cross-sectional area of cells in males' and females' cardiac slices, respectively; n = 90 in each group. FIG. 17L shows representative echocardiogram images. All data are represented as average Mean ± S.E.M. Data were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using unpaired 2-tailed Student t-test for all panels. 2-way ANOVA was used for data comparison in all panels except FIG.17C and 17G, which were evaluated using the unpaired 2- tailed Student t-test. FIG.17C, red circle without filling is an excluded outlier, detected using the ROUT method; Q = 2% and was not used in the statistical analysis. FIG. 18A–H shows systolic function is not different between AKAP12OXand WT mice sham groups or vehicle treated groups. FIG. 18A–H show echocardiographic data showing systolic cardiac function parameters; EF% and FS% in sham groups (FIG. 18A–B; males and FIG.18E–F; females) and vehicle treated groups (FIG.18C–D; males and FIG.18G–H; females). All data represented as average Mean ± S.E.M.; N 5 / group for all panels. Statistical analysis was performed using 2-way ANOVA followed by Sidak multi comparisons post hoc test. FIG. 19A–D shows that the AKAP12 gene and protein expression are upregulated in human failing hearts. FIG.19A shows a summary plot of AKAP12 gene expression data adapted from a previous report of 16 meta-studies (see Flores et al., “Consensus transcriptional landscapeof human end stage heart failure,” J. Amer. Heart. Assoc.10(7): e019667 (2021)), with each pointrepresenting the average expression from one study. FIG.19B shows quantification of AKAP12 gene expression in LV samples collected from patients with failing hearts (n = 6) and non-failing hearts (n = 8). FIG. 19C shows a Western blot of AKAP12 including all LV samples collected from patient failing and non-failing hearts. FIG.19D shows the quantification of the western blot using ImageLab. All data are represented as average Mean ± S.E.M. Data were determined to have a parametric distribution by the Shapiro-Wilk test and were analyzed using unpaired 2-tailed Student t-test for all panels. FIG.20 shows the action potential (AP) shape at baseline in female mice cardiomyocytes from the AKAP12-OX group (AKAP12 overexpressed in mouse hearts) and the AKAP12-WT group (AKAP12 normally expressed in mouse hearts). At the AP baseline, the peak shape (depolarization stage) of AKAP12-OX and AKAP12-WT was similar. However, the resting potential in AKAP12-OX was higher than AKAP12-WT, and at the end of the repolarization stage, AKAP12-OX took a longer time to recover to the resting potential. FIG. 21 shows the AP shape with isoproterenol (ISO) treatment in female mice cardiomyocytes from the AKAP12-OX group and the AKAP12-WT group. At the AP with ISO treatment, the peak shape (depolarization stage) and recovery shape (repolarization stage) of AKAP12-OX and AKAP12-WT were similar. However, the resting potential in AKAP12-OX remained higher than in AKAP12-WT. FIG.22 shows action potential duration 90% (APD90) in female mice cardiomyocytes from the AKAP12-OX group and the AKAP12-WT group, with or without ISO treatment. In alignment with AP shape data, at the end of the repolarization stage as the representative point, APD90 showed that the AKAP12-OX group was significantly higher than the AKAP12-WT group. After treatment with ISO, the AKAP12-WT group remained similar to AKAP12-WT with no ISO treatment (baseline). However, the AKAP12-OX with ISO treatment APD90 decreased significantly compared to AKAP12-OX with no ISO treatment (baseline). FIG. 23 shows APD90 in female mice cardiomyocytes from the AKAP12-OX group and the AKAP12-WT group, with the treatment of PF-04957325 (PDE8 inhibitor) or PF-04957325 and ISO. In alignment with AP shape data, at the end of the repolarization stage as the representative point, APD90 showed that the AKAP12-OX group was significantly higher than the AKAP12-WT group. After treatment with PF-04957325, the AKAP12-WT group remained similar to AKAP12- WT with no PF-04957325 treatment (baseline). However, the AKAP12-OX with PF-04957325 treatment APD90 decreased significantly compared to AKAP12-OX with no PF-04957325 treatment (baseline). In addition, the AKAP12-OX with PF-04957325 and ISO treatment APD90 also decreased compared to AKAP12-OX with no treatment. FIG. 24 shows AP duration shape in male mice cardiomyocytes from the AKAP12-OX group, with the treatment of PF-04957325 or PF-04957325 and ISO. After treatment with PF- 04957325, the AKAP12-OX with PF treatment APD90 decreased significantly compared to AKAP12-OX with no treatment (baseline). In addition, the AKAP12-OX with PF and ISO treatment APD90 also decreased compared to AKAP12-OX with no treatment. The shapes of AKAP12-OX with PF or PF and ISO treatment were similar. FIG.25A–C show whole-heart pictures and H&E staining from female and male AKAP12- WT and AKAP12-OX mice. FIG.25A shows whole-heart pictures from female AKAP12-WT and AKAP12-OX mice. FIG.25B shows whole-heart pictures from male AKAP12-WT and AKAP12- OX mice. FIG.25C shows H&E staining images from AKAP12-WT and AKAP12-OX mice. FIG.26A–E show cardiac slice data from female AKAP12OXtransgenic and wild-type (WT) mice. FIG.26A shows stress-strain loops. FIG.26B shows force-time traces. FIG.26C shows developed stress. FIG.26D shows departure velocity. FIG.26E shows return velocity. FIG.27A–E show cardiac slice data from male AKAP12OXtransgenic and wild-type (WT) mice. FIG.27A shows stress-strain loops. FIG.27B shows force-time traces. FIG.27C shows developed stress. FIG.27D shows departure velocity. FIG.27E shows return velocity. DETAILED DESCRIPTION Compositions and methods are described herein for maintaining or rescuing cardiac function in a cell or a subject by targeting and modulating the AKAP12 signalosome. Also described herein are compositions and methods for treating or preventing cardiovascular disease in a subject by targeting and modulating the AKAP12 signalosome. In some embodiments, the compositions and methods may comprise one or more therapeutic agents targeting AKAP12, PDE8, or a combination thereof for modulation of the AKAP12 signalosome. One or more therapeutic agents targeting AKAP12, PDE8, or a combination thereof may comprise a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof. The therapeutic agents may modulate the expression and / or activity of AKAP12, PDE8, or a combination thereof in the cell or the subject. For example, the therapeutic agents may inhibit the expression and / or activity of AKAP12, PDE8, or a combination thereof in the cell or the subject. In the following description, various embodiments and individual features are disclosed. As will be apparent to a person having ordinary skill in the art, all combinations of such embodiments and features are possible and can result in preferred embodiments. Definitions Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. For example, any nomenclatures used in connection with, and techniques of biochemistry, molecular biology, immunology, microbiology, genetics, cell and tissue culture, and protein and nucleic acid chemistry described herein are well known and commonly used in the art. In case of conflict, the present disclosure, including definitions, will control. Exemplary methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the embodiments and aspects described herein. As used herein, the terms “amino acid,” “nucleotide,” “polynucleotide,” “vector,” “polypeptide,” and “protein” have their common meanings as would be understood by a biochemist of ordinary skill in the art. Standard single letter nucleotides (A, C, G, T, U) and standard single letter amino acids (A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y) are used herein. As used herein, terms such as “include,” “including,” “contain,” “containing,” “having,” and the like mean “comprising.” The present disclosure also contemplates other embodiments “comprising,” “consisting essentially of,” and “consisting of” the embodiments or elements presented herein, whether explicitly set forth or not. As used herein, “comprising,” is an “open- ended” term that does not exclude additional, unrecited elements or method steps. As used herein, “consisting essentially of” limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristics of the claimed invention. As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim. As used herein, the terms “a,” “an,” “the” and similar terms used in the context of the disclosure (especially in the context of the claims) are to be construed to cover both the singular and plural unless otherwise indicated herein or clearly contradicted by the context. In addition, “a,” “an,” or “the” means “one or more” unless otherwise specified. As used herein, the term “or” can be conjunctive or disjunctive. As used herein, the term “and / or” refers to both the conjunctive and disjunctive. As used herein, the term “substantially” means to a great or significant extent, but not completely. As used herein, the term “about” or “approximately” as applied to one or more values of interest, refers to a value that is similar to a stated reference value, or within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, such as the limitations of the measurement system. In one aspect, the term “about” refers to any values, including both integers and fractional components that are within a variation of up to ± 10% of the value modified by the term “about.” Alternatively, “about” can mean within 3 or more standard deviations, per the practice in the art. Alternatively, such as with respect to biological systems or processes, the term “about” can mean within an order of magnitude, in some embodiments within 5-fold, and in some embodiments within 2-fold, of a value. As used herein, the symbol “~” means “about” or “approximately.” All ranges disclosed herein include both end points as discrete values as well as all integers and fractions specified within the range. For example, a range of 0.1–2.0 includes 0.1, 0.2, 0.3, 0.4. . . 2.0. If the end points are modified by the term “about,” the range specified is expanded by a variation of up to ±10% of any value within the range or within 3 or more standard deviations, including the end points, or as described above in the definition of “about.” As used herein, the terms “active ingredient” or “active pharmaceutical ingredient” refer to a pharmaceutical agent, active ingredient, compound, or substance, compositions, or mixtures thereof, that provide a pharmacological, often beneficial, effect. As used herein, the terms “control,” or “reference” are used herein interchangeably. A “reference” or “control” level may be a predetermined value or range, which is employed as a baseline or benchmark against which to assess a measured result. “Control” also refers to control experiments or control cells. As used herein, the term “dose” denotes any form of an active ingredient formulation or composition, including cells, that contains an amount sufficient to initiate or produce a therapeutic effect with at least one or more administrations. “Formulation” and “composition” are used interchangeably herein. As used herein, the term “prophylaxis” refers to preventing or reducing the progression of a disorder, either to a statistically significant degree or to a degree detectable by a person of ordinary skill in the art. As used herein, the terms “effective amount” or “therapeutically effective amount,” refer to a substantially non-toxic, but sufficient amount of an action, agent, composition, or cell(s) being administered to a subject that will prevent, treat, or ameliorate to some extent one or more of the symptoms of the disease or condition being experienced or that the subject is susceptible to contracting. The result can be the reduction or alleviation of the signs, symptoms, or causes of a disease, or any other desired alteration of a biological system. An effective amount may be based on factors individual to each subject, including, but not limited to, the subject’s age, size, type or extent of disease, stage of the disease, route of administration, the type or extent of supplemental therapy used, ongoing disease process, and type of treatment desired. In some embodiments, “effective amount” may also refer to a dosage of the compounds or compositions effective for eliciting a desired effect. This term as used herein may also refer to an amount effective at bringing about a desired in vivo effect in an animal, mammal, or human. As used herein, the term “subject” refers to an animal. Typically, the subject is a mammal. A subject also refers to primates (e.g., humans, male or female; infant, adolescent, or adult), non- human primates, rats, mice, rabbits, pigs, cows, sheep, goats, horses, dogs, cats, fish, birds, and the like. In one embodiment, the subject is a primate. In one embodiment, the subject is a human. As used herein, a subject is “in need of treatment” if such subject would benefit biologically, medically, or in quality of life from such treatment. A subject in need of treatment does not necessarily present symptoms, particularly in the case of preventative or prophylaxis treatments. As used herein, the terms “inhibit,” “inhibition,” or “inhibiting” refer to the reduction or suppression of a given biological process, condition, symptom, disorder, or disease, or a significant decrease in the baseline activity of a biological activity or process. As used herein, “treatment” or “treating” refers to prophylaxis of, preventing, suppressing, repressing, reversing, alleviating, ameliorating, or inhibiting the progress of a biological process including a disorder or disease, or completely eliminating a disease. A treatment may be either performed in an acute or chronic way. The term “treatment” also refers to reducing the severity of a disease or symptoms associated with such disease prior to affliction with the disease. “Repressing” or “ameliorating” a disease, disorder, or the symptoms thereof involves administering a cell, composition, or compound described herein to a subject after the clinical appearance of such disease, disorder, or its symptoms. “Prophylaxis of” or “preventing” a disease, disorder, or the symptoms thereof involves administering a cell, composition, or compound described herein to a subject prior to the onset of the disease, disorder, or the symptoms thereof. “Suppressing” a disease or disorder involves administering a cell, composition, or compound described herein to a subject after induction of the disease or disorder thereof but before its clinical appearance or symptoms thereof have manifested. “Administration” or “administering,” as used herein, refers to providing, contacting, and / or delivery of an action, agent, composition, or cell(s) by any appropriate route to achieve a desired effect. In some embodiments, the term “administering” may also refer to the placement of a compound or a composition as disclosed herein into a subject by a method or route that results in at least partial localization of the compound or composition at a desired site in the subject. Administration may include, but is not limited to, oral, sublingual, parenteral (e.g., intravenous, intracardiac, infusion (e.g., cardiac catheter infusion), subcutaneous, intracutaneous, intramuscular, intraarticular, intraarterial, intrasynovial, intrasternal, intrathecal, intralesional or intracranial injection), enteral, transdermal, topical, buccal, rectal, vaginal, nasal, ophthalmic, via inhalation, and implants. Via the parenteral route, the compound or composition may be in the form of solutions or suspensions for infusion or injection, or as lyophilized powders. Via the enteral route, the compound or composition may be in the form of capsules, gel capsules, tablets, sugar-coated tablets, syrups, suspensions, solutions, powders, granules, emulsions, or microspheres, nanospheres, lipid vesicles, or polymer vesicles allowing for controlled release. Via the topical route, the compound or composition may be in the form of an aerosol, spray, powder, lotion, cream, paste, gel, ointment, oil, suspensions, solutions, or emulsions. As used herein, “signalosome” refers to a specific multimolecular signaling complex that regulates the association of upstream signals with downstream effector molecules for the compartmentalization of cell signaling pathways. Compounds or Combinations In some embodiments, this disclosure relates to compounds (i.e., therapeutic agents) for maintaining or rescuing cardiac function in a cell or a subject by targeting and modulating the AKAP12 signalosome. In other embodiments, this disclosure relates to compounds for treating or preventing cardiovascular disease in a subject by targeting and modulating the AKAP12 signalosome. In certain embodiments, the compound(s) may comprise one or more therapeutic agents targeting AKAP12, PDE8, or a combination thereof. One or more therapeutic agents targeting AKAP12, PDE8, or a combination thereof may comprise a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof. In one particular embodiment, the compound may be a therapeutic agent that inhibits the expression and / or activity of AKAP12. For example, the compound may be a nucleic acid comprising a siRNA, a shRNA, or an antisense oligonucleotide that inhibits or reduces the RNA and protein expression levels of AKAP12 in a cell or a subject, or that maintains the RNA and protein expression levels of AKAP12 at normal healthy levels in a cell or a subject. In another example, the compound may be a small molecule that inhibits or prevents the binding of AKAP12with one or more beta-adrenergic receptors ( ARs) of the AKAP12 signalosome, including, butnot limited to, type-1 ( 1AR) and type-2 ( 2AR). In another example, the compound may be a small molecule that inhibits or prevents the binding of AKAP12 with one or more other proteins of the AKAP12 signalosome, including, but not limited to, PKA, PDE4D, and PDE8. In another particular embodiment, the compound may be a therapeutic agent that inhibits the expression and / or activity of PDE8. For example, the compound may be a small molecule that inhibits or prevents the binding or association of PDE8 with AKAP12 or with the AKAP12 signalosome in general. In certain preferred embodiments, the disclosed compounds may comprise cardiac- specific therapeutic agents for targeting AKAP12, PDE8, or a combination thereof specifically in heart cells or heart tissue. For example, the compound may be a cardiac-specific siRNA targeting AKAP12 to inhibit or reduce RNA and protein expression levels of AKAP12 specifically in a subject’s heart. The disclosed compounds can be used as single therapeutic agents or in combination with one or more other drugs in the treatment, prevention, control, amelioration, or reduction of risk of the aforementioned diseases, disorders, and conditions for which the compound or the other drugs have utility, where the combination of drugs together are safer or more effective than either drug alone. The other drug(s) can be administered by a route and in an amount commonly used therefor, contemporaneously or sequentially with a disclosed compound. When a disclosed compound is used contemporaneously with one or more other drugs, a pharmaceutical composition in unit dosage form containing such drugs and the disclosed compound may be used. However, the combination therapy can also be administered on overlapping schedules. It is also envisioned that the combination of one or more active ingredients and a disclosed compound can be more efficacious than as a single agent. Thus, when used in combination with one or more other active ingredients, the disclosed compounds and the other active ingredients can be used in lower doses than when each is used singly. The pharmaceutical compositions and methods of the present invention can further comprise other therapeutically active compounds as noted herein which are usually applied in the treatment of the above-mentioned pathological conditions. The above combinations include combinations of a disclosed compound not only with one other active compound but also with two or more other active compounds. Likewise, disclosed compounds can be used in combination with other drugs that are used in the prevention, treatment, control, amelioration, or reduction of risk of the diseases or conditions for which disclosed compounds are useful. Such other drugs can be administered, by a route and in an amount commonly used therefor, contemporaneously, or sequentially with a compound of the present invention. When a compound of the present invention is used contemporaneously with one or more other drugs, a pharmaceutical composition containing such other drugs in addition to a disclosed compound is preferred. Accordingly, the pharmaceutical compositions include those that also contain one or more other active ingredients, in addition to a compound of the present invention. The weight ratio of a disclosed compound to a second active ingredient can be varied and will depend upon the effective dose of each ingredient. Generally, an effective dose of each will be used. Thus, for example, when a compound of the present invention is combined with another agent, the weight ratio of a disclosed compound to the other agent will generally range from about 10000:1 to about 1:10000, preferably 5000:1 to 1:5000. Combinations of a compound of the present invention and other active ingredients will generally also be within the aforementioned range, but in each case, an effective dose of each active ingredient should be used. Accordingly, the disclosed compounds can be used alone or in combination with other agents that are known to be beneficial in the subject indications or other drugs that affect receptors or enzymes that either increase the efficacy, safety, and convenience or reduce unwanted side effects or toxicity of the disclosed compounds. The subject compound and the other agent can be co-administered, either in concomitant therapy or in a fixed combination. A compound or composition described herein may be used in combination with other known therapies. Administered “in combination,” as used herein, means that two (or more) different treatments are delivered to a cell or a subject during the course of the cell or subject’s affliction with the disorder, e.g., the two or more treatments are delivered after a subject has been diagnosed with the disorder and before the disorder has been cured or eliminated or treatment has ceased for other reasons. In some embodiments, the delivery of one treatment is still occurring when the delivery of the second begins, so there is overlap in terms of administration. This is sometimes referred to herein as “simultaneous” or “concurrent delivery.” In other embodiments, the delivery of one treatment ends before the delivery of the other treatment begins. In some embodiments of either case, the treatment is more effective because of combined administration. For example, the second treatment is more effective, e.g., an equivalent effect is seen with less of the second treatment, or the second treatment reduces symptoms to a greater extent, than would be seen if the second treatment were administered in the absence of the first treatment, or the analogous situation is seen with the first treatment. In some embodiments, delivery is such that the reduction in a symptom, or other parameter related to the disorder is greater than what would be observed with one treatment delivered in the absence of the other. The effect of the two treatments can be partially additive, wholly additive, or greater than additive. The delivery can be such that the effect of the first treatment delivered is still detectable when the second is delivered. A compound described herein and at least one additional therapeutic agent can be administered simultaneously, in the same or in separate compositions, or sequentially. For sequential administration, a compound or composition described herein can be administered first, and the additional agent can be administered subsequently, or the order of administration can be reversed. When formulating the pharmaceutical compositions described herein, the clinician may utilize preferred dosages as warranted by the condition of the subject being treated. For example, in one embodiment, a compound or composition described herein may be administered at a dosing schedule described herein, e.g., once every one, two, three, four, five, or six weeks. Also, in general, a compound or composition described herein, and an optional additional therapeutic agent do not have to be administered in the same pharmaceutical composition, and may, because of different physical and chemical characteristics, have to be administered by different routes. The determination of the mode of administration and the advisability of administration, where possible, in the same pharmaceutical composition, is well within the knowledge of the skilled clinician. The initial administration can be made according to established protocols known in the art, and then, based on the observed effects, the dosage, modes of administration, and times of administration can be modified by the skilled clinician. The actual dosage of a compound or composition described herein and / or any additional therapeutic agent employed may be varied depending on the requirements of the subject and the severity of the condition being treated. Determination of the proper dosage for a particular situation is within the skill of the art. Generally, treatment is initiated with smaller dosages which are less than the optimum dose of the compound. Thereafter, the dosage is increased by small amounts until the optimum effect under the circumstances is reached. In some embodiments, when a compound or composition described herein is administered in combination with one or more additional therapeutic agents, the additional therapeutic agent(s) is administered at a standard dose. If a compound or composition described herein and the additional therapeutic agent(s) are not administered simultaneously or essentially simultaneously, then the initial order of administration of a compound or composition described herein, and the additional therapeutic agent(s), may be varied. Thus, for example, a compound or composition described herein may be administered first followed by the administration of the additional therapeutic agent(s); or the additional therapeutic agent(s) may be administered first followed by the administration of a compound or composition described herein. This alternate administration may be repeated during a single treatment protocol. The determination of the order of administration, and the number of repetitions of administration of each therapeutic agent during a treatment protocol, is well within the knowledge of the skilled physician after evaluation of the disease being treated and the condition of the subject. Thus, in accordance with experience and knowledge, the practicing physician can modify each protocol for the administration of a component (a compound or composition described herein) of the treatment according to the individual subject’s needs, as the treatment proceeds. The attending clinician, in judging whether treatment is effective at the dosage administered, will consider the general well-being of the subject as well as more definite signs such as relief of disease-related symptoms. Pharmaceutical Compositions and Formulations The disclosed compounds (i.e., therapeutic agents) may be incorporated into pharmaceutical compositions suitable for administration to a cell or a subject (such as a patient, which may be a human or non-human). The disclosed compounds may also be provided as formulations. Such pharmaceutical compositions can be administered in dosages and by techniques well known to those skilled in the medical and pharmaceutical arts taking into consideration such factors as the age, sex, weight, and condition of the particular subject, and the route of administration. The pharmaceutical compositions and formulations may include a “therapeutically effective amount” or a “prophylactically effective amount” of the therapeutic agent. A “therapeutically effective amount” refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired therapeutic result. A therapeutically effective amount of the composition may be determined by a person skilled in the art and may vary according to factors such as the disease state, age, sex, and weight of the individual, and the ability of the composition to elicit a desired response in the individual. A therapeutically effective amount is also one in which any toxic or detrimental effects of a compound of the invention are outweighed by the therapeutically beneficial effects. A “prophylactically effective amount” refers to an amount effective, at dosages and for periods of time necessary, to achieve the desired prophylactic result. Typically, since a prophylactic dose is used in subjects prior to or at an earlier stage of disease, the prophylactically effective amount will be less than the therapeutically effective amount. For example, a therapeutically effective amount of a compound disclosed herein may be about 0.1 mg / kg to about 1000 mg / kg, about 5 mg / kg to about 950 mg / kg, about 10 mg / kg to about 900 mg / kg, about 15 mg / kg to about 850 mg / kg, about 20 mg / kg to about 800 mg / kg, about 25 mg / kg to about 750 mg / kg, about 30 mg / kg to about 700 mg / kg, about 35 mg / kg to about 650 mg / kg, about 40 mg / kg to about 600 mg / kg, about 45 mg / kg to about 550 mg / kg, about 50 mg / kg to about 500 mg / kg, about 55 mg / kg to about 450 mg / kg, about 60 mg / kg to about 400 mg / kg, about 65 mg / kg to about 350 mg / kg, about 70 mg / kg to about 300 mg / kg, about 75 mg / kg to about 250 mg / kg, about 80 mg / kg to about 200 mg / kg, about 85 mg / kg to about 150 mg / kg, and about 90 mg / kg to about 100 mg / kg. While a compound described herein may be administered alone in the methods described herein, it may also be presented as one or more pharmaceutical compositions (e.g., formulations). A compound described herein may be formulated with one or more pharmaceutically acceptable carriers, salts, adjuvants, excipients, diluents, fillers, buffers, stabilizers, preservatives, lubricants, or other materials well known to those skilled in the art, and optionally other therapeutic or prophylactic agents. Accordingly, the methods described herein include the administration of one or more pharmaceutical compositions, as discussed herein, in which a compound described herein is admixed together with one or more pharmaceutically acceptable carriers, excipients, buffers, adjuvants, stabilizers, or other materials, as described herein. Suitable carriers, excipients, etc. can be found in standard pharmaceutical texts, for example, Remington’s Pharmaceutical Sciences, 18thed, Mack Publishing Company, Easton, Pa., 1990. The formulations may conveniently be presented in unit dosage form and may be prepared by any methods known in the art of pharmacy. Such methods include the step of bringing into association the active compound(s) with the carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the active compound with liquid carriers or finely divided solid carriers or both, and then if necessary, shaping the product. Formulations may be in the form of liquids, solutions, suspensions, emulsions, elixirs, syrups, tablets, lozenges, granules, powders, capsules, cachets, pills, ampoules, suppositories, pessaries, ointments, gels, pastes, creams, sprays, mists, foams, lotions, oils, boluses, electuaries, or aerosols. Formulations suitable for oral administration (e.g., by ingestion) may be presented as discrete units such as capsules, cachets, or tablets, each containing a predetermined amount of the active compound; as a powder or granules; as a solution or suspension in an aqueous or nonaqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion; as a bolus; as an electuary; or as a paste. A tablet may be made by conventional means, e.g., compression or molding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active compound in a free-flowing form such as a powder or granules, optionally mixed with one or more binders (e.g., povidone, gelatin, acacia, sorbitol, tragacanth, hydroxypropylmethyl cellulose); fillers or diluents (e.g., lactose, microcrystalline cellulose, calcium hydrogen phosphate); lubricants (e.g., magnesium stearate, talc, silica); disintegrants (e.g., sodium starch glycolate, cross-linked povidone, cross-linked sodium carboxymethyl cellulose); surface-active or dispersing or wetting agents (e.g., sodium lauryl sulfate); and preservatives (e.g., methyl p-hydroxybenzoate, propyl p-hydroxybenzoate, sorbic acid). Molded tablets may be made by molding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated to provide slow or controlled release of the active compound therein using, for example, hydroxypropylmethyl cellulose in varying proportions to provide the desired release profile. Tablets may optionally be provided with an enteric coating, to provide release in parts of the gut other than the stomach. Formulations suitable for parenteral administration (e.g., by injection, including cutaneous, subcutaneous, intramuscular, intravenous, and intradermal), include aqueous and nonaqueous isotonic, pyrogen-free, sterile injection solutions which may contain anti-oxidants, buffers, preservatives, stabilizers, bacteriostats, and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspensions which may include suspending agents and thickening agents, and liposomes or other microparticulate systems which are designed to target the compound to blood components or one or more organs. Examples of suitable isotonic vehicles for use in such formulations include Sodium Chloride Injection, Ringer’s Solution, or Lactated Ringer’s Injection. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid carrier, for example, water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets. Formulations may be in the form of liposomes or other microparticulate systems which are designed to target the active compound to blood components or one or more organs. Formulations suitable for topical administration (e.g., transdermal, intranasal, ocular, buccal, and sublingual) may be formulated as an ointment, cream, suspension, lotion, powder, solution, paste, gel, spray, aerosol, or oil. Alternatively, a formulation may comprise a patch or a dressing such as a bandage or adhesive plaster impregnated with active compounds and optionally one or more excipients or diluents. Formulations suitable for topical administration in the mouth include lozenges comprising the active compound in a flavored basis, usually sucrose and acacia or tragacanth; pastilles comprising the active compound in an inert basis such as gelatin and glycerin, or sucrose and acacia; and mouthwashes comprising the active compound in a suitable liquid carrier. Formulations suitable for topical administration to the eye also include eye drops wherein the active compound is dissolved or suspended in a suitable carrier, especially an aqueous solvent for the active compound. Formulations suitable for nasal administration, wherein the carrier is a solid, include a coarse powder having a particle size, for example, in the range of about 20 to about 500 microns which is administered in the manner in which snuff is taken, i.e., by rapid inhalation through the nasal passage from a container of the powder held close up to the nose. Suitable formulations wherein the carrier is a liquid for administration as, for example, nasal spray, nasal drops, or by aerosol administration by a nebulizer, include aqueous or oily solutions of the active compound. Formulations suitable for administration by inhalation include those presented as an aerosol spray from a pressurized pack, with the use of a suitable propellant, such as dichlorodifluoromethane, trichlorofluoromethane, dichoro-tetrafluoroethane, carbon dioxide, or other suitable gases. Further formulations suitable for inhalation include those presented as a nebulizer. Formulations suitable for topical administration via the skin include ointments, creams, and emulsions. When formulated in an ointment, the active compound may optionally be employed with either a paraffinic or a water-miscible ointment base. Alternatively, the active compounds may be formulated in a cream with an oil-in-water cream base. If desired, the aqueous phase of the cream base may include, for example, at least about 30% w / w of polyhydric alcohol, i.e., an alcohol having two or more hydroxyl groups such as propylene glycol, butane- 1,3-diol, mannitol, sorbitol, glycerol and polyethylene glycol and mixtures thereof. The topical formulations may desirably include a compound that enhances absorption or penetration of the active compound through the skin or other affected areas. Examples of such dermal penetration enhancers include dimethylsulfoxide and related analogs. When formulated as a topical emulsion, the oily phase may optionally comprise merely an emulsifier (otherwise known as an emulgent), or it may comprise a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil. Preferably, a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabilizer. It is also preferred to include both an oil and a fat. Together, the emulsifier(s) with or without stabilizer(s) make up the so-called emulsifying wax, and the wax together with the oil and / or fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations. Suitable emulgents and emulsion stabilizers include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate, and sodium lauryl sulfate. The choice of suitable oils or fats for the formulation is based on achieving the desired cosmetic properties, since the solubility of the active compound in most oils likely to be used in pharmaceutical emulsion formulations may be very low. The cream should preferably be a non-greasy, non-staining, and washable product with suitable consistency to avoid leakage from tubes or other containers. Straight or branched chain, mono- or dibasic alkyl esters such as diisoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a blend of branched chain esters known as Crodamol CAP may be used, the last three being preferred esters. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and / or liquid paraffin or other mineral oils can be used. Formulations suitable for rectal administration may be presented as a suppository with a suitable base comprising, for example, cocoa butter or a salicylate. Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams, or spray formulations containing in addition to the active compound, such carriers as are known in the art to be appropriate. Thus, the compounds and their pharmaceutically acceptable salts may be formulated for administration by, for example, solid dosing, eye drop, in a topical oil-based formulation, injection, inhalation (either through the mouth or the nose), implants, or oral, buccal, parenteral, or rectal administration. Techniques and formulations may generally be found in Remington’s Pharmaceutical Sciences, (Meade Publishing Co., Easton, Pa.). Therapeutic compositions must typically be sterile and stable under the conditions of manufacture and storage. The route by which the disclosed compounds are administered, and the form of the composition will dictate the type of carrier to be used. The composition may be in a variety of forms, suitable, for example, for systemic administration (e.g., oral, rectal, nasal, sublingual, buccal, implants, or parenteral) or topical administration (e.g., dermal, pulmonary, nasal, aural, ocular, liposome delivery systems, or iontophoresis). Carriers for systemic administration typically include at least one of diluents, lubricants, binders, disintegrants, colorants, flavors, sweeteners, antioxidants, preservatives, glidants, solvents, suspending agents, wetting agents, surfactants, combinations thereof, and others. All carriers are optional in the compositions. Suitable diluents include sugars such as glucose, lactose, dextrose, and sucrose; diols such as propylene glycol; calcium carbonate; sodium carbonate; sugar alcohols, such as glycerin; mannitol; and sorbitol. The amount of diluent(s) in a systemic or topical composition is typically about 50 to about 90%. Suitable lubricants include silica, talc, stearic acid and its magnesium salts and calcium salts, calcium sulfate; and liquid lubricants such as polyethylene glycol and vegetable oils such as peanut oil, cottonseed oil, sesame oil, olive oil, corn oil, and oil of theobroma. The amount of lubricant(s) in a systemic or topical composition is typically about 5 to about 10%. Suitable binders include polyvinyl pyrrolidone; magnesium aluminum silicate; starches such as corn starch and potato starch; gelatin; tragacanth; and cellulose and its derivatives, such as sodium carboxymethylcellulose, ethyl cellulose, methylcellulose, microcrystalline cellulose, and sodium carboxymethylcellulose. The amount of binder(s) in a systemic composition is typically about 5 to about 50%. Suitable disintegrants include agar, alginic acid and the sodium salt thereof, effervescent mixtures, croscarmellose, crospovidone, sodium carboxymethyl starch, sodium starch glycolate, clays, and ion exchange resins. The amount of disintegrant(s) in a systemic or topical composition is typically about 0.1 to about 10%. Suitable colorants include a colorant such as an FD&C dye. When used, the amount of colorant in a systemic or topical composition is typically about 0.005 to about 0.1%. Suitable flavors include menthol, peppermint, and fruit flavors. The amount of flavor(s), when used, in a systemic or topical composition is typically about 0.1 to about 1.0%. Suitable sweeteners include aspartame and saccharin. The amount of sweetener(s) in a systemic or topical composition is typically about 0.001 to about 1%. Suitable antioxidants include butylated hydroxyanisole (“BHA”), butylated hydroxytoluene (“BHT”), and vitamin E. The amount of antioxidant(s) in a systemic or topical composition is typically about 0.1 to about 5%. Suitable preservatives include benzalkonium chloride, methyl paraben, and sodium benzoate. The amount of preservative(s) in a systemic or topical composition is typically about 0.01 to about 5%. Suitable glidants include silicon dioxide. The amount of glidant(s) in a systemic or topical composition is typically about 1 to about 5%. Suitable solvents include water, isotonic saline, ethyl oleate, glycerine, hydroxylated castor oils, alcohols such as ethanol, and phosphate buffer solutions. The amount of solvent(s) in a systemic or topical composition is typically from about 0 to about 100%. Suitable suspending agents include AVICEL RC-591 (from FMC Corporation of Philadelphia, PA) and sodium alginate. The amount of suspending agent(s) in a systemic or topical composition is typically about 1 to about 8%. Suitable surfactants include lecithin, Polysorbate 80, sodium lauryl sulfate, and the TWEENS from Atlas Powder Company of Wilmington, Delaware. Suitable surfactants include those disclosed in the C.T.F.A. Cosmetic Ingredient Handbook, 587-592 (1992); Remington’s Pharmaceutical Sciences, 15thed., 335-337 (1975); and McCutcheon’s Volume 1, Emulsifiers & Detergents, North American ed, 236-239 (1994). The amount of surfactant(s) in the systemic or topical composition is typically about 0.1% to about 5%. Although the amounts of components in the systemic compositions may vary depending on the type of systemic composition prepared, in general, systemic compositions include 0.01% to 50% of an active compound and 50% to 99.99% of one or more carriers. Compositions for parenteral administration typically include 0.1% to 10% of actives and 90% to 99.9% of a carrier including a diluent and a solvent. Compositions for oral administration can have various dosage forms. For example, solid forms include tablets, capsules, granules, and bulk powders. These oral dosage forms include a safe and effective amount, usually at least about 5%, and more particularly from about 25% to about 50% of actives. The oral dosage compositions include about 50% to about 95% of carriers, and more particularly, from about 50% to about 75%. Tablets can be compressed, tablet triturates, enteric-coated, sugar-coated, film-coated, or multiple-compressed. Tablets typically include an active component, and a carrier comprising ingredients selected from diluents, lubricants, binders, disintegrants, colorants, flavors, sweeteners, glidants, and combinations thereof. Specific diluents include calcium carbonate, sodium carbonate, mannitol, lactose, and cellulose. Specific binders include starch, gelatin, and sucrose. Specific disintegrants include alginic acid and croscarmellose. Specific lubricants include magnesium stearate, stearic acid, and talc. Specific colorants are the FD&C dyes, which can be added for appearance. Chewable tablets preferably contain sweeteners such as aspartame and saccharin, or flavors such as menthol, peppermint, fruit flavors, or a combination thereof. Capsules (including implants, time release, and sustained release formulations) typically include an active compound and a carrier including one or more diluents disclosed above in a capsule comprising gelatin. Granules typically comprise a disclosed compound, and preferably glidants such as silicon dioxide to improve flow characteristics. Implants can be of the biodegradable or non-biodegradable type. The selection of ingredients in the carrier for oral compositions depends on secondary considerations like taste, cost, and shelf stability, which are not critical for the purposes of this invention. Solid compositions may be coated by conventional methods, typically with pH or time- dependent coatings, such that a disclosed compound is released in the gastrointestinal tract in the vicinity of the desired application, or at various points and times to extend the desired action. The coatings typically include one or more components selected from the group consisting of cellulose acetate phthalate, polyvinyl acetate phthalate, hydroxypropyl methyl cellulose phthalate, ethyl cellulose, EUDRAGIT® coatings (available from Evonik Industries of Essen, Germany), waxes and shellac. Compositions for oral administration can have liquid forms. For example, suitable liquid forms include aqueous solutions, emulsions, suspensions, solutions reconstituted from non- effervescent granules, suspensions reconstituted from non-effervescent granules, effervescent preparations reconstituted from effervescent granules, elixirs, tinctures, syrups, and the like. Liquid orally administered compositions typically include a disclosed compound and a carrier, namely, a carrier selected from diluents, colorants, flavors, sweeteners, preservatives, solvents, suspending agents, and surfactants. Peroral liquid compositions preferably include one or more ingredients selected from colorants, flavors, and sweeteners. Other compositions useful for attaining systemic delivery of the subject compounds include sublingual, buccal, and nasal dosage forms. Such compositions typically include one or more soluble filler substances such as diluents including sucrose, sorbitol, and mannitol; and binders such as acacia, microcrystalline cellulose, carboxymethyl cellulose, and hydroxypropyl methylcellulose. Such compositions may further include lubricants, colorants, flavors, sweeteners, antioxidants, and glidants. The disclosed compounds can be topically administered. Topical compositions that can be applied locally to the skin may be in any form including solids, solutions, oils, creams, ointments, gels, lotions, shampoos, leave-on and rinse-out hair conditioners, milks, cleansers, moisturizers, sprays, skin patches, and the like. Topical compositions include: a disclosed compound, and a carrier. The carrier of the topical composition preferably aids penetration of the compounds into the skin. The carrier may further include one or more optional components. The amount of the carrier employed in conjunction with a disclosed compound is sufficient to provide a practical quantity of composition for administration per unit dose of the compound. Techniques and compositions for making dosage forms useful in the methods of this invention are described in the following references: Modern Pharmaceutics, Chapters 9 and 10, Banker & Rhodes, eds. (1979); Lieberman et al., Pharmaceutical Dosage Forms: Tablets (1981); and Ansel, Introduction to Pharmaceutical Dosage Forms, 2nd Ed., (1976). A carrier may include a single ingredient or a combination of two or more ingredients. In the topical compositions, the carrier includes a topical carrier. Suitable topical carriers include one or more ingredients selected from phosphate buffered saline, isotonic water, deionized water, monofunctional alcohols, symmetrical alcohols, aloe vera gel, allantoin, glycerin, vitamin A and E oils, mineral oil, propylene glycol, PPG-2 myristyl propionate, dimethyl isosorbide, castor oil, combinations thereof, and the like. More particularly, carriers for skin applications include propylene glycol, dimethyl isosorbide, and water, and even more particularly, phosphate buffered saline, isotonic water, deionized water, monofunctional alcohols, and symmetrical alcohols. The carrier of a topical composition may further include one or more ingredients selected from emollients, propellants, solvents, humectants, thickeners, powders, fragrances, pigments, and preservatives, all of which are optional. Suitable emollients include stearyl alcohol, glyceryl monoricinoleate, glyceryl monostearate, propane-1,2-diol, butane-1,3-diol, mink oil, cetyl alcohol, isopropyl isostearate, stearic acid, isobutyl palmitate, isocetyl stearate, oleyl alcohol, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol, isocetyl alcohol, cetyl palmitate, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polyethylene glycol, triethylene glycol, lanolin, sesame oil, coconut oil, arachis oil, castor oil, acetylated lanolin alcohols, petroleum, mineral oil, butyl myristate, isostearic acid, palmitic acid, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate, myristyl myristate, and combinations thereof. Specific emollients for skin include stearyl alcohol and polydimethylsiloxane. The amount of emollient(s) in a skin-based topical composition is typically about 5% to about 95%. Suitable propellants include propane, butane, isobutane, dimethyl ether, carbon dioxide, nitrous oxide, and combinations thereof. The amount of propellant(s) in a topical composition is typically about 0% to about 95%. Suitable solvents include water, ethyl alcohol, methylene chloride, isopropanol, castor oil, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, dimethylsulfoxide, dimethyl formamide, tetrahydrofuran, and combinations thereof. Specific solvents include ethyl alcohol and homotopic alcohols. The amount of solvent(s) in a topical composition is typically about 0% to about 95%. Suitable humectants include glycerin, sorbitol, sodium 2-pyrrolidone-5-carboxylate, soluble collagen, dibutyl phthalate, gelatin, and combinations thereof. Specific humectants include glycerin. The amount of humectant(s) in a topical composition is typically 0% to 95%. The amount of thickener(s) in a topical composition is typically about 0% to about 95%. Suitable powders include beta-cyclodextrins, hydroxypropyl cyclodextrins, chalk, talc, fullers earth, kaolin, starch, gums, colloidal silicon dioxide, sodium polyacrylate, tetra alkyl ammonium smectites, trialkyl aryl ammonium smectites, chemically-modified magnesium aluminum silicate, organically-modified montmorillonite clay, hydrated aluminum silicate, fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose, ethylene glycol monostearate, and combinations thereof. The amount of powder(s) in a topical composition is typically 0% to 95%. The amount of fragrance in a topical composition is typically about 0% to about 0.5%, particularly, about 0.001% to about 0.1%. Suitable pH adjusting additives include HCl or NaOH in amounts sufficient to adjust the pH of a topical pharmaceutical composition. Methods of Treatment In some embodiments, this disclosure further relates to methods for maintaining or rescuing cardiac function in a cell or a subject by targeting and modulating the AKAP12 signalosome. In other embodiments, this disclosure further relates to methods for treating or preventing cardiovascular disease in a subject by targeting and modulating the AKAP12 signalosome. The methods comprise administering to a cell or a subject a therapeutically effective amount of any of the compounds or pharmaceutical compositions disclosed herein. In some embodiments, the cell or the subject being treated with the disclosed compounds or pharmaceutical compositions may have increased RNA and / or protein expression of AKAP12 relative to a control cell or subject. In certain embodiments, the increased expression of AKAP12 may be cardiac-specific overexpression of AKAP12 in the cell or the subject relative to a control cell or subject. In some embodiments, a subject being treated with the disclosed compounds or pharmaceutical compositions may have, or be at risk of developing heart failure. In some embodiments, the methods may maintain or rescue cardiac contractility in the cell or the subject. It will be appreciated that appropriate dosages of the active compounds and compositions comprising the active compounds can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of therapeutic benefit against any risk or deleterious side effects of the treatments described herein. The selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and / or materials used in combination, and the age, sex, weight, condition, general health, and prior medical history of the patient. The amount of compound or composition and the route of administration will ultimately be at the discretion of a trained physician, although generally, the dosage will be to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects. The actual dosage can also depend on the determined experimental effectiveness of the specific compound or composition that is administered. For example, the dosage may be determined based on in vitro responsiveness of relevant cultured cells, or in vivo responses observed in appropriate animal models or human studies. Administration in vivo can be effected in one dose, continuously or intermittently (e.g., in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of the therapy, the target cell being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician. In some embodiments, a subject may be administered a single dose of the disclosed compounds or compositions. In other embodiments, a subject may be administered a plurality of doses over a period of time. For example, in various embodiments, a compound or composition as described herein may be administered to a subject once a day (SID / QD), twice a day (BID), three times a day (TID), four times a day (QID), or more, so as to administer a therapeutically effective amount to the subject, where the therapeutically effective amount is any one or more of the doses described herein. In some embodiments, a compound or composition as described herein is administered to a subject 1–3 times per day, 1–7 times per week, 1–9 times per month, 1–12 times per year, or more. In other embodiments, a compound or composition as described herein is administered for about 1–10 days, 10–20 days, 20–30 days, 30–40 days, 40–50 days, 50–60 days, 60–70 days, 70–80 days, 80–90 days, 90–100 days, 1–6 months, 6–12 months, 1– 5 years, or more. In various embodiments, a compound or composition as described herein is administered at about 0.001–0.01, 0.01–0.1, 0.1–0.5, 0.5–5, 5–10, 10–20, 20–50, 50–100, 100– 200, 200–300, 300–400, 400–500, 500–600, 600–700, 700–800, 800–900, 900–1000 mg / kg, or a combination thereof. In general, a suitable dose of the active compound may be in the range of about 100 g to about 250 mg per kilogram body weight of the subject per day. Modes of Administration Methods of treatment may include any number of modes of administering a disclosed compound or composition. Modes of administration may include tablets, pills, dragees, hard and soft gel capsules, granules, pellets, aqueous, lipid, oily, or other solutions, emulsions such as oil- in-water emulsions, liposomes, aqueous or oily suspensions, syrups, elixirs, solid emulsions, solid dispersions or dispersible powders. For the preparation of pharmaceutical compositions for oral administration, the agent may be admixed with commonly known and used adjuvants and excipients such as for example, gum arabic, talcum, starch, sugars (such as, e.g., mannitose, methyl cellulose, lactose), gelatin, surface-active agents, magnesium stearate, aqueous or non- aqueous solvents, paraffin derivatives, cross-linking agents, dispersants, emulsifiers, lubricants, conserving agents, flavoring agents (e.g., ethereal oils), solubility enhancers (e.g., benzyl benzoate or benzyl alcohol) or bioavailability enhancers (e.g., Gelucire™). In the pharmaceutical composition, the agent may also be dispersed in a microparticle, e.g., a nanoparticulate composition. For parenteral administration, the agent can be dissolved or suspended in a physiologically acceptable diluent, such as, e.g., water, buffer, oils with or without solubilizers, surface-active agents, dispersants, or emulsifiers. As oils for example and without limitation, olive oil, peanut oil, cottonseed oil, soybean oil, castor oil, and sesame oil may be used. More generally spoken, for parenteral administration, the agent can be in the form of an aqueous, lipid, oily, or other kind of solution or suspension or even administered in the form of liposomes or nano- suspensions. The term “parenterally,” as used herein, refers to modes of administration which include intravenous, intracardiac, infusion (e.g., cardiac catheter infusion), intramuscular, intraperitoneal, intrasternal, subcutaneous, and intraarticular injection and infusion. Kits In some embodiments, this disclosure further relates to kits comprising any of the compounds or pharmaceutical compositions disclosed herein and, optionally, one or more of packaging, a label, information, or instructions for use. In certain embodiments, the use of the disclosed kits will maintain or rescue cardiac function in a cell or a subject. In certain embodiments, the use of the disclosed kits will provide treatment or prevention for cardiovascular diseases in a subject. The information and instructions of the disclosed kits may be in the form of words, pictures, or both, and the like. In addition, or in the alternative, the disclosed kits may provide information and instructions for methods of administering any one of the compounds or pharmaceutical compositions disclosed herein, preferably with the benefit of maintaining or rescuing cardiac function, and / or treating or preventing cardiovascular disease. Embodiments One embodiment described herein is a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. In one aspect, the therapeutic agent modulates expression and / or activity of AKAP12 and PDE8 in the cell or the subject. In another aspect, the therapeutic agent inhibits expression and / or activity of AKAP12 and PDE8 in the cell or the subject. In another aspect, PDE8 is PDE8A. In another aspect, the therapeutic agent comprises a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof. In another aspect, the therapeutic agent is a nucleic acid comprising a siRNA, a shRNA, or an antisense oligonucleotide. In another aspect, the therapeutic agent is a cardiac-specific therapeutic agent. In another aspect, the pharmaceutical composition further comprises one or more pharmaceutically acceptable buffers, salts, carriers, or diluents. Another embodiment described herein is a kit comprising: a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8; and optionally, one or more of packaging, a label, or instructions for use. Another embodiment described herein is a method of maintaining or rescuing cardiac function in a cell or a subject, the method comprising: administering to the cell or the subject a therapeutically effective amount of a pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. In one aspect, the cell or the subject has increased expression of AKAP12 relative to a control cell or subject. In another aspect, the subject has, or is at risk of developing, heart failure. In another aspect, the method maintains or rescues cardiac contractility in the cell or the subject. Another embodiment described herein is a method of treating or preventing cardiovascular disease in a subject, the method comprising: administering to the subject a therapeutically effective amount of a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. In one aspect, the subject has increased expression of AKAP12 relative to a control subject. In another aspect, the subject has, or is at risk of developing, heart failure. In another aspect, the method maintains or rescues cardiac contractility in the subject. Another embodiment described herein is the use of a pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8 as a medicament for maintaining or rescuing cardiac function in a cell or a subject. Another embodiment described herein is the use of a pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8 as a medicament for treating or preventing cardiovascular disease in a subject. Another embodiment described herein is a pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12, PDE8, or a combination thereof. In one aspect, the therapeutic agent modulates the expression and / or activity of AKAP12, PDE8, or a combination thereof in the cell or the subject. In another aspect, the therapeutic agent inhibits the expression and / or activity of AKAP12, PDE8, or a combination thereof in the cell or the subject. In another aspect, the therapeutic agent comprises a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof. In another aspect, the therapeutic agent is a nucleic acid comprising a siRNA, an shRNA, or an antisense oligonucleotide. In another aspect, the therapeutic agent is a cardiac-specific therapeutic agent. In another aspect, the pharmaceutical composition further comprises one or more pharmaceutically acceptable buffers, salts, carriers, or diluents. It will be apparent to one of ordinary skill in the relevant art that suitable modifications and adaptations to the compositions, formulations, methods, processes, and applications described herein can be made without departing from the scope of any embodiments or aspects thereof. The compositions and methods provided are exemplary and are not intended to limit the scope of any of the specified embodiments. All of the various embodiments, aspects, and options disclosed herein can be combined in any variations or iterations. The scope of the compositions, formulations, methods, and processes described herein include all actual or potential combinations of embodiments, aspects, options, examples, and preferences herein described. The exemplary compositions and formulations described herein may omit any component, substitute any component disclosed herein, or include any component disclosed elsewhere herein. The ratios of the mass of any component of any of the compositions or formulations disclosed herein to the mass of any other component in the formulation or to the total mass of the other components in the formulation are hereby disclosed as if they were expressly disclosed. Should the meaning of any terms in any of the patents or publications incorporated by reference conflict with the meaning of the terms used in this disclosure, the meanings of the terms or phrases in this disclosure are controlling. Furthermore, the foregoing discussion discloses and describes merely exemplary embodiments. All patents and publications cited herein are incorporated by reference herein for the specific teachings thereof. Various embodiments and aspects of the inventions described herein are summarized by the following clauses: Clause 1. A pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8. Clause 2. The pharmaceutical composition of clause 1, wherein the therapeutic agent modulates expression and / or activity of AKAP12 and PDE8 in the cell or the subject. Clause 3. The pharmaceutical composition of clause 1 or 2, wherein the therapeutic agent inhibits expression and / or activity of AKAP12 and PDE8 in the cell or the subject. Clause 4. The pharmaceutical composition of any one of clauses 1–3, wherein PDE8 is PDE8A. Clause 5. The pharmaceutical composition of any one of clauses 1–4, wherein the therapeutic agent comprises a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof. Clause 6. The pharmaceutical composition of any one of clauses 1–5, wherein the therapeutic agent is a nucleic acid comprising a siRNA, a shRNA, or an antisense oligonucleotide. Clause 7. The pharmaceutical composition of any one of clauses 1–6, wherein the therapeutic agent is a cardiac-specific therapeutic agent. Clause 8. The pharmaceutical composition of any one of clauses 1–7, further comprising one or more pharmaceutically acceptable buffers, salts, carriers, or diluents. Clause 9. A kit comprising: the pharmaceutical composition of any one of clauses 1–8; and optionally, one or more of packaging, a label, or instructions for use. Clause 10. A method of maintaining or rescuing cardiac function in a cell or a subject, the method comprising: administering to the cell or the subject a therapeutically effective amount of the pharmaceutical composition of any one of clauses 1–8. Clause 11. The method of clause 10, wherein the cell or the subject has increased expression of AKAP12 relative to a control cell or subject. Clause 12. The method of clause 10 or 11, wherein the subject has, or is at risk of developing, heart failure. Clause 13. The method of any one of clauses 10–12, wherein the method maintains or rescues cardiac contractility in the cell or the subject. Clause 14. A method of treating or preventing cardiovascular disease in a subject, the method comprising: administering to the subject a therapeutically effective amount of the pharmaceutical composition of any one of clauses 1–8. Clause 15. The method of clause 14, wherein the subject has increased expression of AKAP12 relative to a control subject. Clause 16. The method of clause 14 or 15, wherein the subject has, or is at risk of developing, heart failure. Clause 17. The method of any one of clauses 14–16, wherein the method maintains or rescues cardiac contractility in the subject. Clause 18. Use of the pharmaceutical composition of any one of clauses 1–8 as a medicament for maintaining or rescuing cardiac function in a cell or a subject. Clause 19. Use of the pharmaceutical composition of any one of clauses 1–8 as a medicament for treating or preventing cardiovascular disease in a subject.

[0002] EXAMPLES Example 1 Cell Culture AC16 cells were obtained from Millipore Sigma Aldrich (32011203, Cat. #SCC109, Temecula, CA, USA). Cells were maintained in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 100 IU / mL penicillin G, 100 g / mL streptomycin (Invitrogen, Carlsbad, CA, USA), and 12.5% fetal bovine serum (FBS). Cell Grouping AC16 cells were grouped into two groups: Controls (AC16 cells without any transfections – Ctrls) and AKAP12-OX (AC16 cells stably transfected with human AKAP12 plasmid – Hygromycin selection). To be consistent, transient transfections of GloSensor and 2AR were always carried out for 48 hours. Animal Studies All animal studies have been approved by the Institutional Animal Care and Use Committee (IACUC Protocol No.17-017) and the ethics committee at the University of Houston (UH-ACP-11-032). Animal care was provided for in AAALAC accredited animal barrier facilities at the University of Houston and has therefore been performed in accordance with the ethical standards in the 1964 Declaration of Helsinki and its later amendments. Animal studies were performed in both males and females 8–12 weeks old. Generating Transgenic Mice Mice with cardiac-specific AKAP12 (also known as “Gravin”) overexpression were generated (AKAP12OX; using the mouse strain C57Bl6 / J) which specifically overexpressed AKAP12 in their cardiomyocytes. The transgene consists of the MHC promoter driving transcription of a mouse AKAP12 cDNA fused to a C-terminal Myc epitope tag, obtained from GeneCopoeia (OmicsLink expression clone EX-Mm12276-M09). The AKAP12-Myc fragment was PCR-amplified from EX-Mm12276-M09 with extended primers and inserted between the SalIand HindIII sites of the pJG / MHC plasmid by recombination. After BamHI excision, the fragmentcontaining the MHC-Gravin-Myc-bGH-polyA sequence was gel purified for pronuclear injection into mouse zygotes. Genotyping using primers specific for this transgene identified transgenic founders. Animal Grouping Animals were grouped as shown in FIG.1. Subcutaneous Osmotic Pump Insertion Eight- to twelve-week-old mice were anesthetized using 3% isoflurane before and during the procedure. A small incision in the area behind the neck was made followed by the insertion of Alzet Osmotic pumps (model 1002) with an infusion rate of 0.2 μL / hr. Isoproterenol (ISO) was dissolved in 0.002% ascorbic acid to prevent oxidation during pump priming. ISO dose was 60 mg / kg / day for 14 days. Pumps were primed at 37 °C overnight before insertion. For the vehicle group, pumps were filled with 0.002% ascorbic acid alone and also primed overnight at 37 °C. See FIG.2. Echocardiography Measurements Baseline measurements by echocardiography were obtained at least one day prior to subcutaneous osmotic pump insertion. Each pump released 60 mg / kg / day of isoproterenol (ISO; a AR agonist) or vehicle (0.002% ascorbic acid) for 14-days with a release rate of 0.2 μL / hr. Cardiac morphology and function were assessed by serial M-mode echocardiography with a VisualSonics Vevo 3100 High-Resolution In-Vivo Micro-Imaging System (VisualSonics In, Ontario, Canada) equipped with a 550× probe. Ventricular measurements in M-mode were taken at baseline, 7-days, and 14-days after ISO treatment with at least three readings per mouse. B- mode echocardiography was used for strain analysis. Mice that had a Heart Rate (HR) below 400 bpm or above 550 bpm were excluded from the analysis. All measurements and analyses were performed by the same investigator. Isolation of Adult Ventricular Mouse Cardiomyocytes for Measurement of Cell Shortening and Intracellular Calcium Levels Downstream 1AR and 2AR Isolation of ventricular cardiomyocytes from the hearts of mice 8–12 weeks old; AKAP12OX, WT was performed by a modified non-Langendorff approach (see below). Following incremental calcium restoration, freshly isolated cardiomyocytes were resuspended in plating medium (M199 medium containing 5% FBS, 10 mmol / L BDM and 100 U / mL penicillin G, and 100 g / mL streptomycin) and plated onto Geltrex-coated wells and allowed to adhere for 1 hour in the incubator at 37 °C. Only rod-shaped cells that showed clear striations and no spontaneous contractions were used for measurements. Cardiomyocyte calcium and contractility measurements were collected using a Multi-Cell Lite® system (IonOptix LLC, Westwood, MA, USA) that allowed repeated measurements on the same cells with different treatments. Cells were paced at 1 Hz; 20 Volts at 37 °C, unless otherwise specified. Basal and post-treatment measurements were recorded for 10 sec. Data collected from the Multi-Cell Lite® system was analyzed using CytoSolver 3.0 automated analysis system (IonOptix LLC, Westwood, MA, USA). See FIG.3. Primary Cardiomyocyte Extraction (Non-Langendorff Protocol) The buffers used were the same buffers that were previously used (see Ackers-Johnson et al., “A simplified, Langendorff-free method for concomitant isolation of viable cardiac myocytes and nonmyocytes from the adult mouse heart,” Circulation Research 119: 909–920 (2016)), except for specific cases where 1 mM Blebbistatin was utilized in the buffers instead of BDM. Pre-digestion buffer administration The EDTA and perfusion buffers used were identical to the original protocol (see Ackers- Johnson et al., “A simplified, Langendorff-free method for concomitant isolation of viable cardiac myocytes and nonmyocytes from the adult mouse heart,” Circulation Research 119: 909–920 (2016)). Initially, 7 mL of the EDTA buffer was administered into the right ventricle, ensuring that the entire volume was delivered within a one-minute timeframe. It is imperative to inflate the heart during the injection process, observing the onset of a subtle pallor. To achieve optimal results, the syringe was positioned just 1–2 mm inside the heart. Subsequently, a clamp was applied to the aorta and the heart was carefully excised from its cavity by cutting above the clamp. Following this, the excised heart was placed into a dish containing 5 mL of EDTA buffer, ensuring complete coverage of the organ with the buffer solution. Proceeding to the left ventricle, 7 mL of EDTA buffer was injected at the apex, employing a gradual administration over approximately 6 minutes. The heart should remain inflated throughout this procedure. Notably, the left ventricle may exhibit resistance to the syringe, necessitating unhurried insertion. In the subsequent step, the heart was transferred into an alternative dish filled with 5 mL of perfusion buffer, ensuring consistent immersion in the buffers. Concluding this part, 3 mL of perfusion buffer was injected into the left ventricle through the same opening, taking care to execute the process slowly over a 5-minute duration to facilitate optimal circulation. Cardiac digestion For the digestion buffer, 50 mL perfusion buffer was mixed with 225 μL of Liberase (5 mg / mL stock solution). The heart was placed in a dish containing 5 mL of Liberase buffer. Subsequently, a controlled volume of 20–30 mL of Liberase buffer was slowly injected into the heart through two or three 10 mL injections, each administered over a 5–7-minute period per injection. Variability in required volume across mice necessitates vigilance to prevent over- digestion. Needles containing Liberase buffer were kept on a heat pad. Following the removal of the clamp, the heart was sectioned using forceps, with minimal force applied. The designated heart chamber (left ventricle in this case) was transferred to another plate containing 3 mL of Liberase buffer. Muscle separation was carried out until fragments were of a size suitable for passage through a 1 mL pipette tip with a wide opening. Subsequent digestion of the heart gently for an additional 2–3 minutes using the pipette tip was performed to emphasize a gentle approach to ensure procedural integrity. To stop digestion, a stop buffer containing 10% FBS in perfusion buffer (kept at room temperature) was utilized. Heart digestion was stopped by adding a volume of the stop buffer to achieve a 1:1 ratio of digestion-buffer : stop-buffer in the plate. The additional pipetting step was performed for an additional 2 minutes. Isolation of healthy rod-shaped cells A 70 m cell strainer was placed on top of a sterile 50 mL tube, through which the entire cell volume was passed. While keeping the strainer in place, an additional stop buffer was introduced; volume added = total volume passed through the strainer. The resulting volume was distributed into two 15 mL tubes and the cells were allowed to settle by gravity for 15–20 minutes, or as brief as 10 minutes. Healthy cells sedimented more rapidly, with dead cells remaining at the top. Calcium reintroduction steps were identical to the original protocol (see Ackers-Johnson et al., “A simplified, Langendorff-free method for concomitant isolation of viable cardiac myocytes and nonmyocytes from the adult mouse heart,” Circulation Research 119: 909–920 (2016)); however, all steps were performed at 37 °C rather than room temperature. RNA Extraction, Real-Time qPCR, and RNA Sequencing AC16 Cells Total RNA was extracted from AC16 cells using PureLink® RNA Mini Kit according to the manufacturer’s instructions. RNA Integrity and quality were assessed, and samples with 260 / 230 and / or 260 / 280 ratios < 2.0 were excluded. 1 μg of total RNA was used for cDNA synthesis using the SuperScript IV VILO (SSIV VILO) kit. For the 10 μL reaction, 5 μL PowerUp™ SYBR™ Green was combined with a 5 μL mix containing cDNA (5 ng / reaction), 500 nM forward and reverse primers diluted in water. The manufacturer’s recommendations were followed for the thermal cycling conditions; UDG activation: 50 °C, 2 min; Dual-Lock DNA polymerase: 95° C, 2 min; Denaturation: 95 °C, 15 sec; Anneal / Extend: 60 °C, 1 min; a total of 40 cycles. Real-time qPCR was carried out using the BioRad CFX-Maestro system (BioRad, Hercules, CA). Primer sequences are provided in Table 1. Expression data were normalized to mean GAPDH. Table 1. Primer Sequences (DNA, 5 3 )Name Sequence SEQ ID NO Human RTqPCR Primers AKAP12 Forward PrimerGCTGGACAGGAAACGGAGAASEQ ID NO: 1AKAP12 Reverse PrimerCACTGCGGTTGACTCTGACTSEQ ID NO: 2GAPDH Forward PrimerGTCTCCTCTGACTTCAACAGCGSEQ ID NO: 3GAPDH Reverse PrimerACCACCCTGTTGCTGTAGCCAASEQ ID NO: 4HPRT1 Forward PrimerCTTGAGCACACAGAGGGCTACASEQ ID NO: 5HPRT1 Reverse PrimerCATTATGCTGAGGATTTGGAAAGSEQ ID NO: 6PDE1A Forward PrimerAGGTCACTTCCAGCAAATTASEQ ID NO: 7PDE1A Reverse PrimerCCACATAGGAAGAAGTTTCGSEQ ID NO: 8PDE1C Forward PrimerAGATATTAGCCATCCAGCAASEQ ID NO: 9PDE1C Reverse PrimerCAACGGAGATGACAGAATSEQ ID NO: 10PDE2A Forward PrimerCCTTCAACAAGCTAGAAGGASEQ ID NO: 11PDE2A Reverse PrimerCGGATCTCATAGCTCTCATCSEQ ID NO: 12PDE3A Forward PrimerCAACACTGTGTGTGTGTGTGSEQ ID NO: 13PDE3A Reverse PrimerCAAGTGGTGCATAGCAGTAASEQ ID NO: 14PDE4A Forward PrimerGCTGAAGACCTCATCGTAACSEQ ID NO: 15PDE4A Reverse PrimerATTCTGTTTGTCCAGGAATGSEQ ID NO: 16PDE4C Forward PrimerAGAGTGGTACCAGAGCAAGASEQ ID NO: 17PDE4C Reverse PrimerTGGGAGCCACCTATAACTAASEQ ID NO: 18PDE4D Forward PrimerCACCAAATGACCTTACCTGTSEQ ID NO: 19PDE4D Reverse PrimerAGCTCCACTGTTACCTTTCASEQ ID NO: 20PDE5A Forward PrimerGAAAAGGACTTTGCTGCTTASEQ ID NO: 21PDE5A Reverse PrimerTGATTTTGTTTGCATCATGTSEQ ID NO: 22PDE7A Forward PrimerGCAATATGAATTTGGCTTTCSEQ ID NO: 23PDE7A Reverse PrimerGGAAAGAGCTGCAGTCTAAASEQ ID NO: 24PDE7B Forward PrimerTCTTCAATACCCATGGACTCSEQ ID NO: 25PDE7B Reverse PrimerATCCTGTGTCATTTCCTTTGSEQ ID NO: 26PDE8A Forward PrimerACCAATGTAATGGATTCTGCSEQ ID NO: 27PDE8A Reverse PrimerTGAGTTACAAGCCCTGAGTTSEQ ID NO: 28PDE8B Forward PrimerAGAACAGGAGGAAAGAGTCCSEQ ID NO: 29PDE8B Reverse PrimerCGTTTCCTGACAGTCTTCTCSEQ ID NO: 30Mouse RTqPCR Primers HPRT1 Forward PrimerGCTTGCTGGTGAAAAGGACCTCTCGAAGSEQ ID NO: 31HPRT1 Reverse PrimerCCCTGAAGTACTCATTATAGTCAAGGGCATSEQ ID NO: 32RPL4 Forward PrimerGCCGCTGGTGGTTGAAGATAASEQ ID NO: 33RPL4 Reverse PrimerCGTCGGTTTCTCATTTTGCCCSEQ ID NO: 34AKAP12 Forward PrimerGTCCAAGAGGAAAGCCAGGATGSEQ ID NO: 35AKAP12 Reverse PrimerCTGTGGAACTGGCTGCCATTTCSEQ ID NO: 36PDE8A Forward PrimerTCAGAGTGTGCAATGGCAACSEQ ID NO: 37PDE8A Reverse PrimerGTCCATCGAATGTTTCCTCCSEQ ID NO: 38PDE1A Forward PrimerTGACGTCACTCAAACTGTGCATTSEQ ID NO: 39PDE1A Reverse PrimerCCATGGCTAAAATTTCCAGTTCASEQ ID NO: 40PDE1C Forward PrimerGAAGACAGCCCTGCAGCAASEQ ID NO: 41PDE1C Reverse PrimerGTGTAACATGAGGGATAAGGCTTTCSEQ ID NO: 42PDE2A Forward PrimerATGAGCTGCCACAGGAAGGASEQ ID NO: 43PDE2A Reverse PrimerATTGCAACTCAGCCGCTTCTSEQ ID NO: 44PDE3A Forward PrimerTTCAGAATGGGACCACAAGAGASEQ ID NO: 45PDE3A Reverse PrimerTCACCCATCACAGCAATATCCASEQ ID NO: 46PDE3B Forward PrimerGGGACTTGAAGCAGTGGTGTAAASEQ ID NO: 47PDE3B Reverse PrimerAGCACTGAAAGATCAACTCCATTTCSEQ ID NO: 48PDE4D Forward PrimerCCTAACTAATTCATGTATCCCCAGGTTSEQ ID NO: 49PDE4D Reverse PrimerGGCCCCACTTGTTCACATCTSEQ ID NO: 50PDE5A Forward PrimerAATACCACCCCTGGAGCACCSEQ ID NO: 51PDE5A Reverse PrimerTTCAAGGGCTCGCCAAAAGCSEQ ID NO: 52AC5 Forward PrimerCACCGCCAATGCCATAGACSEQ ID NO: 53AC5 Reverse PrimerCTTCAGCGCCACCTTGGTSEQ ID NO: 54AC6 Forward PrimerCTTCATCTGTTTTATCCAGCTCCTTSEQ ID NO: 55AC6 Reverse PrimerCGGCATAAATCCCGAGTATCASEQ ID NO: 56AC8 Forward PrimerGGATCTACATCCATCGCTATGAGASEQ ID NO: 57AC8 Reverse PrimerCGTGGAGAGGTTGGTAAATCCTSEQ ID NO: 58Genotyping Primers (Mouse) AKAP12-Ox Forward PrimerACTTGCGGTTTCTGATAGTTCTGASEQ ID NO: 59AKAP12-Ox Reverse PrimerCAGAGATGAGTTTCTGCTCGCTAGSEQ ID NO: 60Left-Ventricular Extracts (Mouse Tissue) Total RNA was extracted from sections of mouse left ventricles using Qiagen – Rneasy Fibrous Tissue Mini Kit according to the manufacturer’s instructions. RNA Integrity and quality were assessed, and samples with 260 / 230 and / or 260 / 280 ratios < 2.0 were excluded. 1 μg of total RNA was used for cDNA synthesis using the SuperScript IV VILO (SSIV VILO) kit. For the 10 μL reaction, 5 μL PowerUp™ SYBR™ Green was combined with a 5 μL mix containing cDNA (5 ng / reaction), 500 nM forward and reverse primers diluted in water. The manufacturer’s recommendations were used for the thermal cycling conditions; UDG activation: 50 °C, 2 min; Dual-Lock DNA polymerase: 95 °C, 2 min; Denaturation: 95 °C, 15 sec; Anneal / Extend: 60 °C, 1 min; a total of 40 cycles. Real-time qPCR was carried out using the BioRad CFX-Maestro system (BioRad, Hercules, CA). Primer sequences are provided in Table 1. Expression data were normalized to the geometric means of two housekeeping genes: RPL4 and HPRT1, unless otherwise specified, analyzed using: Relative gene expression where E represents Primer Efficiency calculated from standard curves using one of the control samples. Part of the samples was processed and analyzed by Novogene for RNA sequencing. Left-Ventricular Extracts (Human Tissue) Human left ventricular tissues were crushed using liquid nitrogen to make powdered samples. TRIzol™ was added to the powdered tissue for further homogenization and RNA extraction. Total RNA was isolated using a Direct-zol RNA MiniPrep kit (Zymo Research 11-331) following the user’s protocol. Dnase treatment step was excluded. Total RNA was eluted in nuclease free water and concentration was measured using a nanodrop. Then 500 ng of total RNA was used to construct cDNA using reverse-transcriptase (iScript™ Reverse Transcription mix, BIO-RAD #1708841). Protein Extraction AC16 Cells Whole-cell extracts were isolated using a mixture containing a final concentration of 1× RIPA Lysis Buffer supplemented with 1× Protease and Phosphatase Inhibitor Cocktail. After the cells were lysed, they were incubated for 30 min on a tube rotator at 4 °C. The cells were then centrifuged at 16000 RCF for 20 min at 4 °C and the supernatant was collected. The concentration of the isolated proteins was determined using Pierce™ BCA Protein Assay Kit. Left-Ventricular Extracts (Mouse Tissue) Total protein from mouse left ventricular sections was isolated using a mixture containing a final concentration of 1× RIPA Lysis Buffer supplemented with 1× Protease and Phosphatase Inhibitor Cocktail. After the cells were lysed, they were then incubated for 120 min on a tube rotator at 4 °C. The concentration of the isolated proteins was determined using Pierce™ BCA Protein Assay Kit. Left-Ventricular Extracts (Human Tissue) Human left ventricular tissues were crushed using liquid nitrogen and further resuspended in freshly prepared lysis buffer (RIPA buffer with 1% CHAPS, a phosphatase inhibitor, complete mini protease inhibitor cocktail, 20 mM sodium fluoride, and 1 mM sodium orthovanadate). These homogenized samples in lysis buffer were sonicated 3 times for 1 sec each at 4 °C followed by centrifugation at 18,000 × g for 20 min to collect the supernatants as total lysates. The concentration of these lysates was measured using a nanodrop. Immunoblotting 6–10 g of protein were separated on Stain Free Mini-PROTEAN® TGX™ Precast Gels for 40–45 min at 180 V. Afterward, the gels were imaged to assess protein integrity and concentration using the stain-free gel option on BioRad ChemiDoc MP Imaging System (BioRad, Hercules, CA). Electrophoretic transfer to 0.2 μm low fluorescence PVDF membranes was performed using the Trans-Blot® Turbo™ Transfer System (BioRad, Hercules, CA). For high molecular weight proteins (AKAP12), the high-molecular transfer option was used (10 min) while for other proteins turbo option was used (7 min). Membranes were then blocked with 5% BSA in Tris Buffered Saline containing 0.1% Tween-20 (0.1% TBST) for 1 hour at room temperature. Subsequently, the membranes were incubated overnight at 4 °C with primary antibodies diluted in 5% BSA in 0.1% TBST, unless otherwise stated. Prior to secondary antibodies incubation, membranes were washed 3 times with 0.1% TBST, each wash for 5 min, shaking at room temperature. Secondary antibodies were freshly prepared at 1:1000, 5% BSA in 0.1% TBST, and membranes were incubated for 1 hour shaking at room temperature. Next, the membranes were washed 3 times with 0.1% TBST, each washed for 5 min, shaking at room temperature. Total protein levels were visualized using the stain-free blot feature on BioRad ChemiDoc MP Imaging System (Auto optimal with membrane activation time 45 sec). Finally, membranes were developed using the SuperSignal West Pico PLUS Chemiluminescent Substrate, by incubating it for 2 min in the dark. BioRad ImageLab software was used for the band intensity analysis and was normalized to total protein expression levels. Glosensor cAMP Assays AC16 cells were seeded into 96-well microplates at a density of 2.0 × 104 cells / well. Thenext day, cells were transfected with 50 ng of 2AR plasmid and 50 ng of pGlo22F plasmid. Forty- eight hours post-transfection, cells were incubated in an equilibration medium (Optimem) with a 1% v / v Glosensor cAMP reagent. After 2 hours of incubation, baseline readings were performed at 37 °C once every minute for 10 min. Next, cells were treated with a vehicle or agonist (10 M EPI or 25 M FSK) in the presence or absence of one of the PDE inhibitors: Rolipram; selective PDE4 inhibitor (Sigma Aldrich, R6520), PF-04957325; selective PDE8 inhibitor (Thermo Fisher, 50-202-9122-1MG), or IBMX; non-selective PDE inhibitor (Sigma Aldrich, I5879). All pretreatments with PDE inhibitors were 30 minutes prior to measuring baseline values. Luminescence measurements were performed once every minute or every 2 min for an additional 60 min using Synergy H1 Multi-Mode Microplate Reader (BioTek, Winooski, VT, USA). Immunocytochemistry Isolated cardiomyocytes were fixed in 4% formaldehyde for 20 min at room temperature and then washed with 1× PBS three times for 5 min each. Cells were overlaid with permeabilization reagent PBST (1× PBS + 0.2% Tween) for 30 min at 37 °C then kept at room temperature for 10 min. Cells were blocked with blocking buffer (TNB) for 30 min at room temperature (Perkin Elmer, FP1020, Waltham, MA, USA) then they were incubated in primary antibodies at concentration 1:100 overnight at 4 °C (anti-AKAP12(Gravin), Sigma Aldrich #G3795, PDE8A, Proteintech # 13956-1AP). The next day cells were washed with 1× PBS 3 times 5 min each then incubated with secondary antibodies at concentration 1:500 (antimouse Alexa Fluor 488 conjugate to detect AKAP12 and antirabbit Alexa Fluor 568 conjugate to detect PDE8A signal, life technologies # A11001, A10042) for one hour. Finally, cells were counterstained and then mounted using mounting media (Vectashield, H-1000-10, Burlingame, CA, USA). Confocal images were obtained using the Leica TCS SP8 confocal system. Colocalization analysis was performed using the ImageJ plugin; Colocalization Finder. Mouse hearts were washed with 1× PBS and subsequently fixed in 4% PFA for 48 hours at 4 °C. Before embedding in the OTC compound and storage at 80 °C, hearts underwent five washes in 1× PBS for 30 minutes each on a shaker at room temperature. Thin sections of 10 m were prepared using a LEICA CM 1950 cryostat and stored at 80 °C. For immunostaining, samples were thawed from 80 °C and allowed to equilibrate at room temperature for 30 minutes. They were then subjected to a 55 °C baking step for 30 minutes, cooled to room temperature, and washed twice in 1× PBS for 5 minutes each. Permeabilization was achieved using 0.1% PBST (1× PBS + 0.2% Tween) for 10 minutes, followed by blocking with TNB for 45 minutes. The primary antibody (AKAP12) was diluted 1:100 in TNB and applied to the samples, which were then incubated overnight at 4 °C. After antibody incubation, the primary antibody was removed, and samples were subjected to three 5-minute washes with PBST. A secondary antibody, Alexa 647, was prepared at a 1:500 dilution in TNB, and samples were incubated at room temperature for 1 hour. Following this, samples underwent three washes with PBST, and DAPI was introduced for nuclear staining. WGA Staining Adult hearts were harvested and then fixed in 4% PFA overnight at 4 °C. Samples were washed with 1× PBS 3 times for 10 mins each. Samples were embedded in OCT and then kept at 80 °C overnight. Sectioning was done using cryostat at 10 m thickness and then kept at 80 °C overnight before staining. The sections were washed with 1× PBS to remove OCT and then incubated for one hour at room temperature with WGA (wheat germ agglutinin) Alexa Fluor 488 conjugate (Molecular Probe, Life Technology, Cat. #W11261). The sections were then counterstained and mounted using mounting media (Vectashield, H-1000-10, Burlingame, CA, USA). ImageJ software was used to measure the cross-sectional area of cells. Graph-Pad Prism software was used for statistical analysis. Competitive ELISA cAMP Assay Intracellular basal cAMP levels in isolated primary cardiomyocytes were assessed using the cAMP Assay Kit (Competitive ELISA, Colorimetric – ab290713) in technical duplicates. Isolated cardiomyocytes were promptly flash frozen before storage at 80 °C immediately following isolation. To facilitate further analysis, the frozen tissue samples were ground into a fine powder under liquid nitrogen in a stainless steel mortar. After evaporating the liquid nitrogen, the powdered samples were weighed in Eppendorf tubes and homogenized in 10 volumes of 0.1 M HCl, with the volume determined by the sample weight (e.g., Sample 1 with a weight of 0.01758 g was mixed with 0.1758 mL of 0.1 M HCl). The homogenization step aimed to ensure uniformity across the samples. Subsequently, the homogenized samples underwent centrifugation at 12,000 × g, allowing debris to be pelted while collecting the supernatant for further analysis using the acetylation format protocol. Considering the possibility of low concentration due to the continued activity of endogenous phosphodiesterases during tissue digestion, the acetylation format was chosen for its enhanced sensitivity over the non-acetylation protocol. As per the protocol’s requirements, the supernatant was diluted at a ratio of 1:32 in 0.1 M HCl to boost assay sensitivity. This involved adding 10 L of supernatant to 320 L of 0.1 M HCl, resulting in a total volume of 330 L for each sample. Statistical Analysis Data were processed using Microsoft Excel (RRID: SCR_016137), Vevo LAB 5.6.1, Image Lab, CytoSolver 3.0, ImageJ, and GraphPad Prism 8.2.1. (RRID: SCR_002798). All values are reported as the Mean ± S.E.M. Numeric data were first analyzed for normality using a Shapiro- Wilk test. Data with parametric distribution were analyzed by unpaired two-tailed Student’s T- test, and 1-way ANOVA and Holm-Sidak or Tukey post hoc multiple comparisons test were used. When significant departures from normality were observed by the Shapiro-Wilk test, nonparametric tests were used. For echocardiograms, 2-way ANOVA and Sidak post hoc multiple comparisons test were used. P values of less than 0.05 were considered significant. Representative images and figures were chosen based on their proximity to the mean / average for each group. Blinding Mice genotypes were blinded during echocardiography acquisition and analysis. Human samples were blinded until both RT-qPCR and Western Blot analysis were completed. Example 2 AKAP12 Upregulation Reduces Intracellular cAMP Levels Post -Adrenergic Receptor Stimulation AC16 cells were grouped into cells stably overexpressing AKAP12 (AKAP12-OX), using Hygromycin-B selection, or controls (endogenous levels of AKAP12). AKAP12 gene expression levels were significantly higher in the AKAP12-OX group (13.16 ± 2.42, fold-change) as compared to controls (0.99 ± 0.04, fold-change; p = 0.0073) (FIG.4A). Protein expression levels were also increased (15.25 ± 1.19, fold change) in the AKAP12-OX group as compared to controls (1.00 ± 0.16, fold change; p = 0.0003) (FIG.4B–C). In mammalian cells, increased intracellular cAMP levels in cardiomyocytes enhance both the speed (chronotropy) and force (inotropy) of contraction by activating Protein Kinase-A (PKA).cAMP production is catalyzed by adenylyl cyclases (AC) which can be activated by the G spathway downstream of stimulated ARs. On the other hand, decreased intracellular cAMP levelscan be attributed to either heightened G i activity, which inhibits AC, or due to increaseddegradation of cAMP being catalyzed by phosphodiesterases (PDE). AKAP12 is proposed to scaffold PDE4D and recruit it near the 2AR. Consequently, lower intracellular cAMP levels were expected in the AKAP12-OX group. To assess this, the GloSensor-cAMP assay was utilized, a luciferase-based biosensor capable of detecting signaling events in real-time. As expected, AKAP12-OX had significantly lower maximum intracellular cAMP accumulation (40.52 ± 9.24, %) compared to controls (68.65 ± 8.31, %; p = 0.0339) downstream the stimulated 2AR when treated with 10 M EPI (FIG.4D).To investigate if impaired G s signaling contributes to the reduced cAMP levels, adenylylcyclase (AC) was targeted using 25 M Forskolin (FSK; Sigma Aldrich, F3917-10MG). Results showed that AKAP12-OX had significantly lower maximum intracellular cAMP (26.65 ± 7.76, %) compared to controls (54.26 ± 8.67, %; p = 0.0290) (FIG. 5A). This suggests that the reducedcAMP levels in the AKAP12-OX group are not correlated to impaired G s pathway activation ofadenylyl cyclases. However, this does not exclude the possibility of reduced AC levels in the AKAP12-OX group that could contribute to reduced cAMP downstream FSK. Higher G i activity arises from a combination of increased G i protein levels and / orincreased activation of the pathway. Therefore, cells were pre-treated with 50 nM Pertussis Toxin (PTX; Thermo Fisher, PHZ1174) overnight before adding 10 M EPI. PTX pre-treatment resulted in significantly lower intracellular cAMP in the AKAP12-OX group (25.53 ± 2.34, %) compared tocontrols (54.01 ± 6.33, %; p = 0.0018) (FIG.5B). Western blot analysis indicated comparable G iprotein expression between the AKAP12-OX and control groups in the absence of AR agonists (1.00 ± 0.15 vs 0.64 ± 0.02, fold change; p = 0.0790) and there was no discernible difference when cells were treated with the non-selective AR agonist ISO (0.901 ± 0.176 vs 1.02 ± 0.10, fold-change; p = 0.5727) or EPI (1.00 ± 0.03 vs 0.92 ± 0.08, fold-change; p = 0.4386) (FIG.5D).These findings suggest that factors other than increased G i activity are likely responsible fordecreased cAMP levels observed in the AKAP12-OX group. To investigate the potential impact of phosphodiesterases (PDEs) on intracellular cAMP levels, both groups were pretreated with 10 M or 0.1 mM IBMX, a non-selective PDE inhibitor, for 30 minutes. Interestingly, only pre-treatment with 0.1 mM IBMX followed by 10 M EPI showed no significant difference in maximum intracellular cAMP levels between groups; AKAP12-OX (70.42 ± 12.61, %) compared to controls (84.65 ± 14.04, %; p = 0.4588) (FIG.4E). While pre- treatment with 10 M IBMX showed a significantly lower intracellular cAMP level in the AKAP12- OX group (83.93 ± 13.60, %) compared to controls (48.19 ± 9.98, %; p = 0.0484) (FIG.5D). This indicates that decreased intracellular cAMP levels observed in the AKAP12-OX group could be attributed to elevated PDE activity or increased PDE expression. Furthermore, the absence of notable variations in intracellular cAMP levels among the groups during vehicle treatment and / or before the administration of AR agonists suggests that the difference in response to the agonist is unlikely due to differences in the baseline cAMP levels. Gene expression analysis in the AKAP12-OX group revealed significant upregulation of several phosphodiesterases (PDEs) including PDE1A, PDE2A, PDE3A, PDE4D, PDE7A, and PDE8A (FIG.4F). Experiments were directed toward PDE4D and PDE8A among the upregulated PDEs. These two enzymes were of interest due to their specificity for cAMP and their potential significance. PDE4D is known for its association with AKAP12, while PDE8A contributes to regulating excitation-contraction coupling in cardiomyocytes and was reported to be IBMX resistant PDE (up to 100 M IBMX). To investigate the influence of AKAP12-PDE4 scaffolding on cAMP levels, cells were treated with the selective PDE4 inhibitor Rolipram (10 M) for 30 minutes before adding EPI (10 M). Under Rolipram treatment, the AKAP12-OX group exhibited significantly lower cAMP levels (22.29 ± 7.00, %) compared to the controls (71.77 ± 7.61, %; p = 0.0007) (FIG.4G). This data excludes PDE4 as the main cause of reduced cAMP in the AKAP12-OX group. Subsequently, cells were treated with the selective PDE8 inhibitor PF-04957325 (200 nM) for 30 minutes before adding EPI (10 M). Notably, there was no significant difference in max intracellular cAMP between the AKAP12-OX group (54.22 ± 5.33, %) and the controls (63.51 ± 9.70, %; p = 0.4212) (FIG. 4H). Based on these findings, it appears that PDE8A might directly contribute to the reduction of intracellular cAMP levels in AKAP12-OX groups. Example 3 PDE8A is in the Vicinity of the AKAP12 Signalosome in Primary Adult Mouse Cardiomyocytes To extend the findings to a more physiologically relevant model, a transgenic mouse line was generated that specifically overexpresses AKAP12 in cardiomyocytes (AKAP12OX) using an MHC promoter. The expression levels of AKAP12 protein were assessed in LV extracts, which confirmed significant upregulation of AKAP12 protein in both male mice, with an average expression of (17.25 ± 3.52, fold-change) compared to WT male mice (0.99 ± 0.36, fold-change; p = 0.0037), as well as in female mice, with an average expression of (18.33 ± 3.36, fold-change) compared to WT female mice (1.00 ± 0.53, fold-change; p = 0.0022) (FIG.6A–B). After validating the animal model, baseline cAMP levels (without ISO) were investigated in primary cardiomyocytes isolated from the LV of WT and AKAP12OXmice. ELISA results revealed no significant differences in baseline intracellular cAMP levels between AKAP12OXmales (54.78 ± 3.50 pmol / mL) and WTs (93.51 ± 19.53 pmol / mL; p = 0.1226), as well as between AKAP12OXfemales (63.12 ± 18.75 pmol / mL) and WTs (74.17 ± 22.72 pmol / mL; p = 0.7266), (FIG. 6C–D). Gene expression levels of several PDEs and ACs from LV extracts were altered including a significantly upregulated PDE8A in both AKAP12OXmales and females compared to WT littermates as well as a significantly downregulated AC8 (FIG. 7A–B). RNAseq data further supported the elevated PDE8A levels (FIG.7C). As such, higher PDE8A protein expression in AKAP12-OX cardiomyocytes was expected. However, western blot analysis showed comparable levels in adult cardiomyocytes from both AKAP12OXand WT groups (FIG.7D–E). Colocalization analysis of AKAP12 and PDE8A showed that Pearson’s Correlation Coefficient (PCC) in the absence of ISO was similar between AKAP12OXcardiomyocytes (0.59 ±0.05) as compared to WT cardiomyocytes (0.05 ± 0.05; P = 2.7 × 10 1) (FIG. 6E–F). In responseto acute AR stimulation with ISO, PDE8A was colocalized near the cell membrane and AKAP12 to a higher extent in the AKAP12OXcardiomyocytes (0.73 ± 0.04) as compared to WTcardiomyocytes (0.53 ± 0.04; P = 7.2 × 10 3). Also, ISO treatment significantly increasedAKAP12-PDE8A interaction when compared to no ISO treatment only in the AKAP12OXcardiomyocytes (P = 9.3 × 10 3) (FIG. 6E–F). This indicated that PDE8A is in the vicinity of theAKAP12 signalosome, and that higher levels of AKAP12 in cardiomyocytes enhance this interaction in response to acute AR stimulation. Therefore, PDE8A is potentially stabilized within the signalosome which contributes to the reduced cAMP levels. The presence of cAMP is essential for PKA activity, which plays a crucial role in regulating the contraction and relaxation of cardiomyocytes. PKA activity was assessed by examining the levels of cardiac troponin-I (cTnI) phosphorylation in both male and female groups post 14 days of ISO treatment. The results indicated that neither male nor female AKAP12OXmice showed significantly lower levels of cTnI phosphorylation compared to their WT littermates, regardless ofthe presence (P = 4.1 × 10 1 and P = 3.5 × 10 1) or absence (P > 9.9 × 10 1 and P = 9.9 × 10 1,respectively) of ISO (FIG. 8A–B). Although no significant differences in PKA activity were observed between the groups, cardiomyocyte contractility is a multifaceted process controlled by various signaling pathways and cellular components, such as AR responsiveness, calcium handling, and myofilament sensitivity. Subsequent detailed studies will be conducted to investigate the molecular interplay between AKAP12 and PDE8A, including the role of AC8 in this context, calcium handling machineries, and myofilament sensitivity. Example 4 Primary Cardiomyocytes from AKAP12OXMice have Reduced Contractility with Acute Isoproterenol (ISO) Treatment Primary cardiomyocytes extracted from male and female AKAP12OXLV showed no significant difference in diastolic sarcomere length compared to cardiomyocytes extracted from WT LV after treatment with 100 nM ISO, indicating that diastolic function is not compromised in AKAP12OXLV cardiomyocytes (FIG.9A–B, I–J). However, AKAP12OXmale cardiomyocytes had significantly lower systolic sarcomere length (1.645 ± 0.03, m) and percent sarcomere shortening (5.86 ± 1.07, %) as compared to WT male cardiomyocytes (1.55 ± 0.01, m; p = 0.0020) and (12.02 ± 0.71, %; p = 0.0001), respectively (FIG. 9A, C–D). Similarly, AKAP12OXfemale cardiomyocytes had significantly lower systolic sarcomere length (1.59 ± 0.01, m) and percent sarcomere shortening (9.20 ± 0.73, %) as compared to WT female cardiomyocytes (1.48 ± 0.01 m; p < 0.0001) and (16.30 ± 0.68, %; p<0.0001), respectively, indicating a compromised systolic function of the AKAP12OXcardiomyocytes, (FIG.9I, K–L). In the absence of ISO, AKAP12OXmale cardiomyocytes required a longer time to fully contract, however, there were no notable variations observed in systolic, diastolic sarcomere lengths or percent shortening as compared to WT. Similarly, a significantly longer time was observed in AKAP12OXfemale cardiomyocytes to fully contract in addition to significantly lower systolic and diastolic sarcomere length compared to WT, however, no significant differences were observed in percent shortening (FIG.10A–D, I–L). Furthermore, in the presence of ISO, significantly reduced contraction and relaxation rates were observed in AKAP12OXmale cardiomyocytes (2.70 ± 0.55 m / sec and 2.07 ± 0.51 m / sec) as compared to WT males (6.22 ± 0.46 m / sec; p = 0.0006 and 3.95 ± 0.32 m / sec; p = 0.0055) (FIG.9E, G). A similar pattern was observed in AKAP12OXfemales with contraction and relaxation rates of (4.23 ± 0.60 m / sec and 3.08 ± 0.34 m / sec) as compared to WT females (8.26 ± 0.37 m / sec; p < 0.0001 and 5.41 ± 0.37 m / sec; p < 0.0001) (FIG. 9M, O). On the contrary, there were no significant differences in contraction and relaxation kinetics between groups in the absence of ISO (FIG.10E, G, M, O). This suggests that AKAP12OXcardiomyocytes experience compromised contractility when exposed to acute ISO treatment, potentially due to disruptions in the downstream AR signaling pathways that affect calcium handling. Example 5 Primary Cardiomyocytes from AKAP12OXMice have Significantly Higher Basal Intracellular Calcium Levels Variations in intracellular calcium concentration [Ca2+]iregulate the optimal performance of cardiac contractility by maintaining a sufficiently high [Ca2+]iduring systole and a low [Ca2+]iduring diastole. Simultaneous to contractility measurements, [Ca2+]ilevels, were investigated and were to observe significantly lower [Ca2+]ilevels in the AKAP12OXcardiomyocytes. Surprisingly, significantly higher systolic and diastolic [Ca2+]iwere observed in AKAP12OXmale and female cardiomyocytes post-acute ISO treatment compared to WT cardiomyocytes (FIG.11A–C, H–J). Regardless, [Ca2+]i% change was not significantly different between the groups, and the elevated systolic calcium did not correlate to better contractility in AKAP12OXcardiomyocytes (FIG.11G, N). This implies the possibility of different basal [Ca2+]ibetween the two groups. Indeed, in the absence of ISO, AKAP12OXmale, and female cardiomyocytes had significantly higher systolic, diastolic, and % change [Ca2+]iwhen electrically stimulated (FIG.12B–D, I–K). Another distinct difference was the spontaneous calcium release pattern observed only in AKAP12OXcardiomyocytes (FIG.11A, H; squared area), which was absent without ISO treatment (FIG. 12A, H). This indicates irregular calcium handling in the AKAP12OXcardiomyocytes downstream of the ARs. Next, [Ca2+]iand contractility were investigated in cardiomyocytes downstream 1AR vs 2AR separately, which showed different patterns in response to ISO. 1AR stimulation with ISO while blocking 2AR with 50 nM ICI-118,551 (Sigma Aldrich, I127-25MG) in primary cardiomyocytes showed significantly lower % shortening in AKAP12OXmales (2.41 ± 0.96,%) ascompared to the WT cardiomyocytes (3.86 ± 0.25,%; P = 2 × 10 2). [Ca2+]i % change was lowerin the AKAP12OXmales (29.79 ± 5.17,%) as compared to the WT cardiomyocytes (41.40 ± 2.25,%; P = 2.1 × 10 1), but it was not statistically significant (FIG. 13A–C). AKAP12OX females hadsignificantly higher % shortening (6.71 ± 0.97,%) as compared to the WT cardiomyocytes (4.04 ±0.32,%; P = 9.2 × 10 3), and significantly higher [Ca2+]i % change (54.62 ± 5.27,%) as comparedto the WT cardiomyocytes (31.52 ± 2.21,%; P < 1.0 × 10 4) (FIG. 12G–I).During 2AR stimulation with ISO, while blocking 1AR with 100nM CGP-20712A (Sigma Aldrich, C231-10MG) in primary cardiomyocytes, the % shortening in AKAP12OXmales (2.48 ± 0.41,%) was significantly lower as compared to the WT cardiomyocytes (4.61 ± 0.44,%; P =5.7 × 10 3). This was observed despite the [Ca2+]i % change being significantly higher in theAKAP12OXgroup (34.47 ± 3.53,%) as compared to WT cardiomyocytes (22.19 ± 1.59,%; P =4.0 × 10 4) (FIG. 13D–F). AKAP12OX females had a comparable % shortening (6.52 ± 0.97, %)to WTs (6.42 ± 0.71, %, P = 8.8 × 10 1) despite the significantly higher [Ca2+]i % change in theAKAP12OX group (39.60 ± 5.54, %) as compared to WTs (20.44 ± 1.35, %; P = 2.0 × 10 4) (FIG.12J–L). Together, this indicates that downstream 1AR signaling in AKAP12OXand WT cardiomyocytes respond similarly to higher [Ca2+]ilevels by enhancing cardiac contractility; whereas, downstream 2AR signaling AKAP12OXcardiomyocytes unlike WTs do not show enhanced contractility in response to higher [Ca2+]i. Example 6 PDE8 Inhibitor (PF-04957325) Reverses AKAP12OXEffect on [Ca2+]iand Contractility in Primary Adult Mouse Cardiomyocytes In the absence of ISO, sarcomere shortening % in AKAP12OXmales and females cardiomyocytes (3.24 ± 0.80 and 4.50 ± 0.56, %) was comparable to WT cardiomyocytes (2.86 ±0.28 and 3.72 ± 0.46, %; P = 5.70 × 10 1 and P = 2.3 × 10 1), respectively. The addition of 30 nMPF-04957325 increased sarcomere shortening %, but the difference was not statistically significant compared to the baseline in any of the groups (FIG. 14A, D). The subsequent introduction of 100 nM ISO, alongside 30 nM PF-04957325, resulted in a significant increase in sarcomere shortening % within each group compared to their baseline and / or 30 nM PF- 04957325 alone; FIG. 14A (males), FIG. 14D (females). Notably, in the presence of both PF- 04957325 and ISO, both male and female AKAP12OXcardiomyocytes exhibited significantly higher contractility (10.31 ± 1.18 and 11.79 ± 1.10, %) compared to WT cardiomyocytes (7.66 ±0.66 and 6.39 ± 0.56, %; P = 4.8 × 10 2 and P < 1.0 × 10 4) (FIG. 14A, D).While 30 nM PF-04957325 alone did not significantly impact [Ca2+]iin either male or female AKAP12OXor WT cardiomyocytes compared to their baseline [Ca2+]i, the combination of 30 nM PF-04957325 and 100 nM ISO led to a significant increase in [Ca2+]iwithin each group compared to their baseline and / or 30 nM PF-04957325 alone (FIG.14B, E). In the presence of both PF-04957325 and ISO, both male and female AKAP12OXcardiomyocytes had a significantly higher % [Ca2+]ichange (59.21 ± 7.12 and 72.65 ± 8.25, %) compared to WT cardiomyocytes(39.26 ± 3.88 and 19.76 ± 2.70, %; P = 1.6 × 10 2 and P < 1.0 × 10 4) (FIG.14B, E). The enhanced[Ca2+]iin the AKAP12OXgroup was correlated with better contractility (FIG.14C, F). This unique response further strengthens the evidence supporting the hypothesis of the AKAP12OX-PDE8 axis. Example 7 Cardiomyocytes AKAP12OXUpregulates Maladaptive Genes in the Left Ventricle Following 14 Days of ISO Treatment To address how cardiac AKAP12OXwould affect cardiac function post chronic ISO treatment, RNAseq analyses were performed on LV extracts from AKAP12OXand WT mice exposed to ISO for 14 days as well as from sham mice (no exposure to ISO). RNAseq data showed that treatment with ISO significantly upregulated 9 of the known maladaptive genes in males (NPPA, GRK5, CTGF, THBS4, POSTN, LOXL4, TGFB2, NOX4, and SFRP1) and 12 maladaptive genes in females (NPPA, NPPB, GRK5, CTGF, THBS4, POSTN, LOXL4, TGFB2, NOX4, SFRP1, P4HA1, and FBLN2) as compared to WT littermates exposed to ISO (FIG.15). Furthermore, AKAP12OXsham mice (not treated with ISO) had also upregulation in some maladaptive genes, such as NPPA, CTGF, THBS4, and TGFB2 (FIG. 15). Notably, AKAP12OXmice upregulated some adaptive genes as well, such as WISP2, FRZB, and FSTL1 as compared to WT littermates (FIG.15). However, the extent of upregulation observed for the maladaptive genes was significantly higher compared to the average upregulation seen for adaptive genes in the AKAP12OXgroup (FIG.16). This suggests that AKAP12OXmight predispose LV tissue to faster remodeling, lower contractility, and systolic malfunction with prolonged ISO treatment. Example 8 Cardiac AKAP12OXWorsens Cardiac Systolic Function and Promotes Left Ventricular Hypertrophy Post 14 Days of Isoproterenol Treatment To confirm that AKAP12OXmight impair ventricular contractility, cardiac function was assessed in AKAP12OXmales and females, compared to WT controls, after treatment with 60 mg / kg / day of ISO for 14 days. In the WT groups, the EF% and FS% showed divergent responses after 14-days of treatment with 60 mg / kg / day of ISO; where some mice exhibited an increase in EF% and FS% while others experienced a decrease, which aligns with prior findings. However, all male and female AKAP12OXmice demonstrated reduced EF% and FS% after the 14-days treatment period (FIG.17A–B; E–F). Precisely, both male and female AKAP12OXmice had significantly lower EF% (42.97 ± 5.78 and 43.89 ± 3.61, %) as compared to WT littermates post ISO treatment (65.22 ± 4.07 and 57.39 ± 3.95, %; p = 0.0100 and 0.0357), respectively. Furthermore, male AKAP12OXmice had significantly lower FS% (21.38 ± 3.53, %) as compared to WT littermates (37.01 ± 3.75, %; p = 0.0262) post 14-days ISO treatment (Table 2 and FIG.17). Global Circumferential Strain (GCS) showed significantly lower LV systolic shortening in both AKAP12OXmales and females post ISOtreatment ( 7.81 ± 0.76 and 14.45 ± 2.22) as compared to WT males and females ( 19.27 ±2.12 and 23.24 ± 2.79; P = 2.5 × 10 3 and P = 3.9 × 10 2), respectively (FIG.17C, G). Importantly,neither 14-days of vehicle (0.002% Ascorbic Acid) treatment, nor sham conditions showed a significant difference in systolic cardiac parameters; EF% and FS% between AKAP12OXand WT groups (FIG.18 and Tables 3–6). LV hypertrophy was assessed using corrected LV mass to Body Weight (BW) ratio, and Wheat Germ Agglutinin (WGA) to determine Cross Sectional Area (CSA) of cardiomyocytes in cardiac sections. AKAP12OXmales and females post 14-days of ISO treatment had higher LV mass / BW (7.12 ± 0.52 and 10.51 ± 1.09, mg / g) as compared to WT littermates (5.49 ± 0.59 and6.40 ± 0.77, mg / g; P = 7.48 × 10 2 and P = 8.6 × 10 3), respectively (Table 2 and FIG. 17D, H).WGA staining further confirmed that 14-days post ISO treatment AKAP12OXcardiomyocytes from both males and females had significantly higher CSA (546.90 ± 20.95 and 463.0 ± 15.81, m2) ascompared to WT cardiomyocytes (241.40 ± 9.59 and 260.5 ± 7.81, m2; P < 1.0 × 10 4 and P <1.0 × 10 4), respectively (FIG. 17I–K). In the absence of ISO, male and female AKAP12OXcardiomyocytes still had significantly higher CSA (227.0 ± 9.79 and 193.7 ± 7.20, m2) ascompared to WT cardiomyocytes (137.6 ± 3.80 and 121.8 ± 4.33, m2; P < 1.0 × 10 4 and P <1.0 × 10 4), which suggests that AKAP12OX cardiomyocytes are predisposed to hypertrophyindependently of ISO stimulation, and are potentially more susceptible to hypertrophic stimuli, such as ISO. Table 2. Echocardiographic Parameters of WT and AKAP12OXMales and Females Group / Echo AKAP12OXmeterWT M ISO NM Para= 9ISO N = 6WT IVS; d 1.23 ± 0.15 1.42 ± 0.11 1.2 ± 0.13 1.64 ± 0.15 IVS; s 1.70 ± 0.15 1.75 ± 0.12 1.58 ± 0.11 1.92 ± 0.16 HR 496.55 ± 10.36 539.51 ± 12.54 487.33 ± 12.14 493.96 ± 16.74 Diameter;s 2.39 ± 0.21 3.16 ± 0.21 2.62 ± 0.13 2.92 ± 0.12 Diameter;d 3.68 ± 0.17 4.01 ± 0.13 3.75 ± 0.11 3.71 ± 0.09 Volume;s 22.38 ± 3.82 41.43 ± 6.40 25.8 ± 2.99 33.65 ± 3.34 Volume;d 58.95 ± 5.82 71.14 ± 5.53 60.52 ± 4.31 59.13 ± 3.35 SV 36.57 ± 2.29 29.7 ± 3.45 34.73 ± 3.77 25.48 ± 2.20 EF% 65.22 ± 4.07 42.97 ± 5.78 ** 57.39 ± 3.95 43.89 ± 3.61 * FS% 36.21 ± 3.40 21.38 ± 3.53 * 30.17 ± 2.78 21.54 ± 2.00 CO 18.02 ± 0.89 16 ± 2.01 16.7 ± 1.49 12.80 ± 1.48 LVID;d 3.65 ± 0.17 4.03 ± 0.15 3.73 ± 0.12 3.60 ± 0.09 LVID;s 2.41 ± 0.22 3.2 ± 0.23 2.65 ± 0.12 2.88 ± 0.11 LVPW;d 1.04 ± 0.13 1.10 ± 0.08 1.00 ± 0.14 1.51 ± 0.09 LVPW;s 1.55 ± 0.16 1.44 ± 0.10 1.46 ± 0.17 1.75 ± 0.10 LV Mass 134.63 ± 13.14 181.21 ± 11.95 * 132.75 ± 12.14 227.8 ± 27.38 ** ISO; Isoproterenol, HR; heart rate, IVS; intraventricular septum, LVID; LV internal dimensions, LVPW; LV posterior wall, SV; stroke volume, EF; ejection fraction, FS; Fractional Shortening, CO; cardiac output, LV; LV, s; systole, d; diastole, M; male, F; female, WT; wild-type, OX; AKAP12OX. All values are expressed as Mean ± S.E.M. Statistical analysis was performed using 2-way ANOVA followed by Sidak multiple comparison post hoc test. * P < 0.05, ** P < 0.01, *** P < 0.001, and **** P < 0.0001. Table 3. Echocardiographic Parameters of WT and AKAP12OXMice; Males-Sham OXWT BSL WT Sham AKAP12OXBSLAKAP12Sham Parameter N = 10 N = 10 N = 7 N = 7 IVS;d 1.41 ± 0.11 1.12 ± 0.07* 1.44 ± 0.13 1.47 ± 0.07* IVS;s 1.84 ± 0.1 1.52 ± 0.07 1.9 ± 0.15 1.84 ± 0.08 HR 485.68 ± 16.39 509.14 ± 15.74 507.18 ± 20.05 462.77 ± 29.85 Diameter;s 2.23 ± 0.21 2.86 ± 0.14 2.19 ± 0.12 2.29 ± 0.16 Diameter;d 3.45 ± 0.18 3.94 ± 0.12* 3.26 ± 0.17 3.38 ± 0.15* Volume;s 19.43 ± 4.43 32.41 ± 3.6* 16.82 ± 2.3 19.02 ± 2.87* Volume;d 51.48 ± 6.41 68.46 ± 4.87* 44.27 ± 6.06 47.61 ± 4.73* SV 32.05 ± 2.95 36.05 ± 1.91 27.46 ± 4.59 28.59 ± 2.22 EF 66.21 ± 4.43 54.01 ± 2.77 61.69 ± 3.43 61.64 ± 3.51 FS 36.75 ± 3.19 27.81 ± 1.82 32.65 ± 2.44 32.81 ± 2.6 CO (LV Trace) 15.6 ± 1.49 18.32 ± 1.05* 13.79 ± 2.29 12.92 ± 0.75* LVID;d 3.39 ± 0.2 3.94 ± 0.12* 3.23 ± 0.17 3.31 ± 0.16* LVID;s 2.25 ± 0.21 2.9 ± 0.14 2.2 ± 0.12 2.33 ± 0.16 LVPW;d 1.19 ± 0.11 0.86 ± 0.08* 1.52 ± 0.1 1.23 ± 0.09* LVPW;s 1.63 ± 0.13 1.21 ± 0.1 1.84 ± 0.14 1.54 ± 0.09 LV Mass(Corrected)151.08 ± 14.47 126.09 ± 11.43 173.81 ± 16.84 152.19 ± 10.21*: Significant difference between WT and AKAP12OXSham Table 4. Echocardiographic Parameters of WT and AKAP12OXMice; Females-Sham WT Sham AKAP12 BSLAKAP12OXWT BSLOXSham Parameter N = 9 N = 9 N = 6 N = 6 IVS;d 1.31 ± 0.13 1.41 ± 0.12 1.2 ± 0.14 1.66 ± 0.12 IVS;s 1.62 ± 0.11 1.79 ± 0.14 1.66 ± 0.14 1.99 ± 0.13 HR 477.49 ± 9.82 499.65 ± 18.63 499.14 ± 13.86 498.43 ± 24.61 Diameter;s 1.76 ± 0.14 2.15 ± 0.13 1.93 ± 0.15 1.91 ± 0.19 Diameter;d 2.95 ± 0.14 3.3 ± 0.09 3.14 ± 0.16 2.98 ± 0.15 Volume;s 10.28 ± 1.83 16.17 ± 2.47 12.31 ± 2.66 12.54 ± 3.41 Volume;d 34.78 ± 3.66 44.68 ± 2.91 40.04 ± 5.06 35.41 ± 4.5 SV 24.5 ± 1.96 28.51 ± 1.8 27.73 ± 2.69 22.87 ± 1.16 EF 72.75 ± 2.85 64.78 ± 3.76 70.3 ± 2.66 67.18 ± 4.27 FS 41.25 ± 2.63 35.15 ± 2.74 38.93 ± 2.07 36.54 ± 3.1 CO (LV Trace) 11.8 ± 1.1 14.1 ± 0.73 13.73 ± 1.23 11.3 ± 0.41 LVID;d 2.84 ± 0.16 3.27 ± 0.09 3.17 ± 0.15 2.96 ± 0.11 LVID;s 1.79 ± 0.15 2.16 ± 0.12 1.95 ± 0.16 1.96 ± 0.21 LVPW;d 1.21 ± 0.13 1.1 ± 0.1 1.26 ± 0.08 1.28 ± 0.14 LVPW;s 1.55 ± 0.14 1.49 ± 0.15 1.7 ± 0.06 1.66 ± 0.16 LV Mass (Corrected) 112 ± 11.8 134.31 ± 10.67 123.84 ± 8.96 152.39 ± 15.34 *: Significant difference between WT and AKAP12OXSham Table 5. Echocardiographic Parameters of WT and AKAP12OXMice; Males-Vehicle WT BSL WT Veh AKAP12OXBSL AKAP12OXVeh Parameter N = 6 N = 6 N = 4 N = 4 IVS;d 1.46 ± 0.17 1.09 ± 0.1 1.42 ± 0.18 1.56 ± 0.14 IVS;s 1.91 ± 0.14 1.61 ± 0.09 1.81 ± 0.22 1.91 ± 0.17 HR 486.84 ± 17.1 507.62 ± 20.87 477.77 ± 26.18 521.23 ± 6.54 Diameter;s 1.91 ± 0.14 2.3 ± 0.22 2.4 ± 0.16 2.81 ± 0.3 Diameter;d 3.08 ± 0.14 3.63 ± 0.18 3.51 ± 0.18 3.79 ± 0.19 Volume;s 12.13 ± 2.27 19.78 ± 3.6 21.1 ± 3.18 31.67 ± 8.32 Volume;d 38.11 ± 4.11 56.77 ± 5.87 52.65 ± 6.26 62.56 ± 6.84 SV 25.98 ± 2.77 36.99 ± 2.53 31.55 ± 4.54 30.89 ± 3.56 EF 68.79 ± 3.98 67.33 ± 4.26 60.69 ± 4.26 51.65 ± 8 FS 38.07 ± 3.42 37.5 ± 3.74 31.96 ± 2.98 26.49 ± 4.65 CO (LV Trace) 12.68 ± 1.48 18.85 ± 1.71 15.04 ± 2.25 16.13 ± 1.94 LVID;d 3.03 ± 0.14 3.63 ± 0.15 3.46 ± 0.2 3.79 ± 0.19 LVID;s 1.93 ± 0.14 2.31 ± 0.21 2.4 ± 0.14 2.83 ± 0.34 LVPW;d 1.28 ± 0.19 0.91 ± 0.14 1.51 ± 0.08 1.39 ± 0.11 LVPW;s 1.68 ± 0.17 1.49 ± 0.17 1.81 ± 0.09 1.63 ± 0.07 LV Mass (Corrected)124.42 ±117.93 ± 211.45 ± 16.88 20.21**186.62 ± 22.9212.24** *: Significant difference between WT and AKAP12OXgroups post vehicle treatment Table 6. Echocardiographic Parameters of WT and AKAP12OXMice; Females-Vehicle WT BSL WT Veh AKAP12OXBSL AKAP12OXVeh Parameter N = 8 N = 8 N = 5 N = 5 IVS;d 1.38 ± 0.17 1.28 ± 0.14 1.58 ± 0.09 1.38 ± 0.08 IVS;s 1.79 ± 0.14 1.79 ± 0.22 1.96 ± 0.1 1.75 ± 0.13 HR 485.56 ± 9.31 511.11 ± 17.35 510.59 ± 11.15 501.82 ± 18.51 Diameter;s 1.89 ± 0.11 2.13 ± 0.18 1.93 ± 0.24 1.77 ± 0.18 Diameter;d 2.96 ± 0.13 3.29 ± 0.17 3.02 ± 0.2 2.9 ± 0.2 Volume;s 11.6 ± 1.59 16.59 ± 3.1 13.02 ± 3.44 10.12 ± 2.63 Volume;d 34.69 ± 3.5 45.16 ± 5.21 36.73 ± 5.34 33.54 ± 5.34 SV 23.09 ± 1.99 28.57 ± 2.19 23.71 ± 2.26 23.43 ± 3.31 EF 67.36 ± 1.6 66.01 ± 3.31 67.65 ± 5.53 70.85 ± 3.65 FS 36.29 ± 1.2 36.01 ± 2.53 37.37 ± 4.4 39.26 ± 2.82 CO (LV Trace) 11.22 ± 0.98 14.6 ± 1.26 12.13 ± 1.22 11.93 ± 1.95 LVID;d 2.98 ± 0.13 3.27 ± 0.18 3 ± 0.2 2.85 ± 0.2 LVID;s 1.91 ± 0.12 2.08 ± 0.18 1.93 ± 0.22 1.79 ± 0.2 LVPW;d 1.17 ± 0.12 1.06 ± 0.14 1.43 ± 0.18 1.2 ± 0.17 LVPW;s 1.54 ± 0.1 1.6 ± 0.15 1.88 ± 0.17 1.61 ± 0.16 LV Mass (Corrected)125.02 ±17.09 121.87 ± 16.62 163.64 ± 20.37 115.63 ± 12.39*: Significant difference between WT and AKAP12OXgroups post vehicle treatment Example 9 AKAP12 is Upregulated in the Left Ventricles of Patients with End-Stage Heart Failure Based on in vivo studies, and previous transcriptomic studies reported in the ReHEAT database showing altered levels of AKAP12 in heart failure (HF) patients (FIG.19A), a goal was to evaluate whether AKAP12 is upregulated in patients with end-stage HF (Table 7). In failing hearts (F, n = 8), AKAP12 gene expression was 2.94 ± 0.55 as compared to non-failing hearts(NF, n = 6) at 1.02 ± 0.13 (fold change; P = 1.3 × 10 2) (FIG. 19B). AKAP12 protein expressionhad a similar pattern in failing hearts (2.01 ± 0.14) compared to non-failing hearts (1.00 ± 0.02, P= 1.6 × 10 3) (FIG. 19C–D). Collectively, these data strongly suggest that AKAP12 upregulation is associated with impaired cardiac function. Table 7. Human Heart Failure Patient Information S4 S5 S8 S9 S10 S13 S14 S15 S17 Age (Y) 28.1 42.3 71.4 28.2 43.6 44 18 53 51 Sex M M M F M M M F F Beta Metopr ockerololNoMetopr blololCoreg CoregDiuretic BumexBumeBume xLasix No xAce Li itorNo No Nsinopr Lisinio InhiboilprilARB No No No No No CaC BlockerNo No No No NoStatin No No Yes No No Hyperten sionNo No Yes No NoPrior MI No No Yes No No Diabetes No No Yes No No IschemiNon- Non- Non- Non- Non- Non- N Ische I Peripart on- HF Type cschemi Ische Ische Ische Ische Ische mic c um mic mic mic mic mic LVEF (%) 30 <20 <20 <20 <20 Cardiac function is mainly mediated by the -adrenoceptor stimulation and subsequentproduction of the second messenger cyclic adenosine 3 ,5 -monophosphate (cAMP). cAMPregulates cardiomyocyte contractile function through activating Protein Kinase-A (PKA). Constant high levels of cAMP in cardiomyocytes can induce cardiac remodeling and hypertrophy. On the other hand, persistent lower cAMP levels are considered a hallmark of maladaptive cardiac remodeling. Thus, for optimal cardiac function cAMP levels are tightly controlled by balancing cAMP production and degradation. Briefly, lower cAMP levels are due to either lower G s pathway activity, higher G ipathway activity, and / or due to increased degradation of cAMP by a family of enzymes known as phosphodiesterases (PDE). Even though both ARs stimulate cAMP production, cells differently interpret the signal produced by the two receptor subtypes, 1AR, and 2AR. These differences are partially attributed to the variable cAMP distribution patterns, which historically were associated with the receptor expression patterns; global cAMP increase downstream 1AR (globally expressed on cardiomyocyte’s surface), and localized cAMP increase downstream the 2AR (localized to the caveola). Currently, it is recognized that A Kinase Anchoring Proteins (AKAPs) compartmentalize cAMP signals forming “microdomains” of the second messenger within the cell in a stimulus- induced manner, assuring some level of specificity. So far, several AKAPs have been associated with cardiac development, contractility, cardiac morphology, and rhythm. AKAP12 is known to scaffold PKA, PDE4D3, PDE4D5, and 2AR; hence, it assembles a signalosome that can regulate cAMP levels downstream or near the 2AR. However, AKAP12’s role in cardiac contractility post chronic and acute stimulation of AR is still unclear. Considering the importance of intracellular cAMP levels for cardiac contractility, how AKAP12 upregulation in vitro affected the intracellular cAMP levels in real-time post 2AR stimulation was investigated. Molecular modeling using human ventricular cell lines (AC16 cells) indicated that AKAP12 upregulation significantly reduced maximum intracellular cAMP levels compared to controls when treated with EPI. In mammalian cells, cAMP production is catalyzed by adenylyl cyclase (AC).AC can be stimulated using ARs ligands that activate the G s pathway downstream of thestimulated 1AR or 2ARs, or directly (bypassing the ARs) using Forskolin. The possibility ofreduced G s activity downstream of the 2AR was excluded based on the results that showedsignificantly lower cAMP in the AKAP12-OX group compared to controls when treated with FSK, a direct activator of AC. Based on this, reduced intracellular cAMP can be associated with the inhibition of AC bythe G i pathway or increased PDE activity because pre-treatment with PTX also showedsignificantly lower cAMP in the AKAP12-OX group compared to controls. The PDE family includes 11 members out of which 6 are expressed in cardiomyocytes and can be divided into (1) cAMP-specific: PDE4 and PDE8 (2) cGMP specific: PDE5, and (3) dual-specificity: PDE1, PDE2, and PDE3. Pre-treatments with Rolipram (a selective PDE4 inhibitor) or Milrinone (a selective PDE3 inhibitor) showed significantly lower intracellular cAMP in the AKAP12-OX group compared to controls. Interestingly, only when using 0.1 mM IBMX (a non-selective PDE inhibitor) were intracellular cAMP levels not significantly different between AKAP12-OX and controls. Additionally, pre-treatment with 10 M IBMX resulted in significantly lower cAMP levels in the AKAP12-OX group as compared to controls. The higher IBMX concentration effectively inhibits cAMP degradation by PDEs, masking the cAMP differences between AKAP12-OX and controls. In contrast, at lower IBMX concentrations, the impact of AKAP12-OX on cAMP levels becomes discernible due to less pronounced PDE inhibition. Additionally, the presence of comparable intracellular cAMP levels in AKAP12-OX groups and controls due to the selective PDE8 inhibitor PF-04957325 strongly implies a central role played by PDE8 in the reduction of cAMP levels observed in AKAP12-OX. This underscores the significance of PDE8 as a potential regulatory target influenced by AKAP12-OX, substantiating the intricate interplay between these factors in cAMP modulation. Therefore, in AC16 cells, stable AKAP12-OX reduces cAMP levels through PDE8. AKAP12 regulates cAMP levels near 2AR by stabilizing PDE8A within the signalosome. In fact,a previous study has proposed that PDE8A directly binds PKA-RI subunit. Most AKAPsincluding AKAP12 preferentially bind to PKA-RII. However, there is a possibility that AKAP12 also binds to the PKA-RI subunit, hence AKAP12 might bind to or be in proximity to PDE8A. In the absence of ISO, immunocytochemistry results from AKAP12OXand WT primary cardiomyocytes showed a similar pattern of PDE8A distribution in the cytoplasm while treatment with 100 nM ISO recruited PDE8A to the cell membrane, a pattern reported in other PDEs. PDE8A was found to colocalize with AKAP12 near the cell membrane regardless of the presence or absence of AR stimulation with ISO, however, the colocalization was notably higher in the AKAP12OXcardiomyocytes specifically when stimulated with ISO, which implies that AKAP12 potentially stabilizes PDE8A in a microenvironment that regulates cAMP levels when AR is stimulated. The present findings show a significantly enhanced % change in [Ca2+]ilevels and contractility in AKAP12OXcardiomyocytes compared to WT cardiomyocytes only observed in the presence of the PDE8A inhibitor PF-04957325 and ISO stimulation. Even though the present study investigated the PDE8A isoform, the findings also showed altered Ca2+handling in AKAP12OXcardiomyocytes proposing that AKAP12OX-PDE8A interplay is partially regulating cardiomyocytes [Ca2+]iand contractility and it can be reversed by inhibiting PDE8A. ARs regulate EC coupling through cAMP, 1AR is the main regulator of cardiac contractility, its stimulation elicits global elevation in cAMP levels while 2AR stimulation is known to increase local cAMP levels. The majority of research suggests that 1AR regulation of contractility is cAMP-dependent while 2AR regulation is cAMP-independent. In agreement with this study, under 1AR selective stimulation, AKAP12OXand WT cardiomyocytes showed increased contractility in response to increased [Ca2+]i. In contrast, selective 2AR stimulation showed that AKAP12OXcardiomyocytes had irregular calcium handling as depicted by notably lower contractility in the presence of significantly higher [Ca2+]ias compared to WT. This pattern was also observed when both ARs were stimulated with a non-selective AR agonist. This potentially shows that AKAP12OX, which scaffolds 2AR, augments 2AR’s regulation of contractility in cardiomyocytes by reducing intracellular cAMP which is pivotal for 1AR regulation of contractility. Cardiomyocyte contraction kinetics further show a pattern of augmented 2AR signaling. This was observed by a significantly slower contraction and relaxation in the ISO- treated AKAP12OX, as compared to ISO-treated WTs, in addition to observing a lower change in kinetics compared to AKAP12OXcontrols. However, further research needs to support this especially because a lot of speculations exist on whether 2AR cardiomyocyte regulation is truly cAMP-independent. As cardiomyocytes are the contractile force of the heart, a deteriorated cardiac function in AKAP12OXmice was expected compared to the WT mice post chronic ISO treatment. To promote cardiac remodeling, subcutaneous osmotic pumps were used to deliver 60 mg / kg / day of ISO for 14-days. ISO-treated WT males and females underwent cardiac remodeling as observed by the significant increase in LV mass compared to sham groups; however, the EF% and FS% were not significantly different between WT sham and ISO-treated groups. In fact, some WT males and females showed elevation in EF% and FS% while others showed reduced EF% and FS%. These observations where both patterns of response have also been reported by others in previous studies with this model and dose of ISO treatment. In contrast, ISO-treated AKAP12OXmales and females had undergone significantly higher cardiac remodeling compared to sham and WT ISO- treated groups. Additionally, all AKAP12OXmice showed significantly reduced EF% and FS% compared to sham groups. Considering that 60 mg / kg / day ISO dose did not deteriorate cardiac function in WT mice, both this study and others dictate that AKAP12OXmice indeed are more prone to cardiac dysfunction with chronic ISO treatment. Further support of this notion is the upregulation of maladaptive genes to a higher extent in the AKAP12OXmice. If AKAP12OXenhances downstream signaling of 2AR in cardiomyocytes, one might initially anticipate an improvement in cardiac function due to the well-established cardioprotective effects of 2AR, as previously suggested. However, it appears that the impact of the 2AR subtype on cardiotoxic versus cardioprotective signaling is heavily influenced by the type, duration, and intensity of cardiac stress. This observation stems from a study indicating that ablation of 2AR had a cardioprotective effect in TAC-induced heart failure, leading to the restoration of Ca2+handling and improved contractility. This finding supports the results where 2AR stimulation in AKAP12OXmice had a negative influence on contractility, and blocking 2AR results in increased responsiveness to calcium-induced contractions in females. The difference in response to 1AR blocking between male and female cardiomyocytes could be attributed to the known differences in their AR distribution. Current therapeutics have many off-target pharmacological effects, which could be reduced by subcellular drug delivery. Hence, AKAPs that form microdomains within the cells have been suggested as targets for precision pharmacology. Consequently, a goal was to evaluate the AKAP12 gene and protein expression in LV extracts from patients with cardiac injury. Remarkably, AKAP12 was significantly upregulated in the failing hearts compared to non-failing hearts. One limitation of this study was the low number of samples; therefore, correlation of confounding diseases, gender, and drug therapies with AKAP12 expression was not possible. Further studies with a larger cohort would address this limitation. Nonetheless, these data are in line with several transcriptomic studies that have been conducted on LV extracts from patients with end-stage HF. Thus, AKAP12 may be a good candidate for precision pharmacology in ameliorating HF. For instance, AKAP12 can be inhibited by small molecules, however, this approach is challenging because the AKAP12 crystal structure is unknown, and whether cardiac AKAP12 knockdown enhances cardiac function has not been assessed. One alternative approach to inhibiting AKAP12 would be maintaining optimal levels of AKAP12 by modifying promoter methylation (epigenetic editing system) using the CRISPR / Cas9 system. In conclusion, AKAP12 makes an appealing target for precision pharmacology, offering potential as a therapeutic target in addressing the complexities of heart failure treatment. Example 10 Action Potential Measurements of Adult Ventricular Mouse Cardiomyocytes with Treatment of ISO, PF, and ISO + PF Isolation of ventricular cardiomyocytes from the hearts of 8-12-week-old AKAP12-OX and AKAP12-WT mice was performed by a modified non-Langendorf approach. Following incremental calcium restoration, freshly isolated cardiomyocytes were resuspended in plating medium (M199 medium containing 5% FBS, 10 mM BDM and 100 U / mL penicillin G, and 100 g / mL streptomycin) and plated onto Geltrex-coated wells and allowed to adhere for 1 hour in the incubator at 37 °C. Only rod-shaped cells that showed clear striations and no spontaneous contractions were used for measurements. Cardiomyocyte action potential measurements were collected using a Multi-Cell Lite® system (IonOptix LLC, Westwood, MA, USA) that allowed repeated measurements on the same cells with different treatments. Cells were paced at 1 Hz and 20 Volts at 37 °C, unless otherwise specified. Baseline and post-treatment measurements were recorded for 10 sec. Data collected from the Multi-Cell Lite® system were analyzed using CytoSolver 3.0 automated analysis system (IonOptix LLC, Westwood, MA, USA). The cardiac action potential results from the sequential opening and closing of ion channel proteins that span the plasma membrane of individual myocytes. Its conduction through the heart depends on electrical coupling between these cells, which is mediated by gap junctions. Differences in the expression and properties of ion channels result in heterogeneities in action potential waveforms in different cardiac regions and cell types, and the normal unidirectional spread of the action potentials through the heart. The cardiac action potential in humans has five different phases (from 0 to 4). Depolarization from the SA node brings the membrane potential to the threshold, opening the voltage-activated sodium channels. This allows the sodium ions to diffuse down their electrochemical gradient from the extracellular space, across the membrane, and into the cell. The resulting sodium current, INa, produces a positive feedback loop that causes further sodium channels to open, and depolarization of the membrane proceeds until the sodium Nernst potential is reached or when the channels are inactivated. This is responsible for the rapid upstroke, termed phase 0, of the action potential. Action potential duration (APD) prolongation is recognized as an indicator of failing hearts or arrhythmia. When at baseline, the cardiomyocytes from AKAP12-OX mice had the highest APD90 compared to AKAP12-OX mice with any treatment or any AKAP12-WT mice groups (FIG. 20–24). This indicated that AKAP12-OX mice cardiomyocytes have the worst action potential profile and the worst cell function. PF-04957325 (PF) treatment inhibits PDE8 and the AKAP12-PDE8 axis. The AKAP12- PDE8 axis signaling is initiated from -adrenergic receptors. Therefore, it was expected that AKAP12-OX mice with either PF-04957325 or PF-04957325 and ISO treatment would decrease the APD prolongation. Aligned with APD90 data in female mice with treatment of PF or PF + ISO, the APD90 was significantly shortened in the AKAP12-OX group compared to baseline (no treatment) (FIG. 22–23). Since APD prolongation is an indicator of heart failure or arrhythmia, the shortened APD represents the improvement of the cardiomyocyte action potential profile. The improvement with PF treatment further indicates that the AKAP12-PDE8 axis is a useful drug target for heart diseases such as heart failure or arrhythmia. Example 11 Heart Disease Evaluation AKAP12-OX mice cardiomyopathy was investigated by evaluating heart shape and H&E staining. Whole-heart shape analyses showed that AKAP12-OX female and male mice had dilated heart sizes, which was due to increased wall thickness of the chambers and not dilated chambers (FIG. 25A–C). This indicated hypertrophic cardiomyopathy in the AKAP12-OX mice rather than dilated cardiomyopathy. Example 12 Cardiac Slice Preparation Cardiac tissue slices were prepared from 8–12-week-old male and female mice. Animals were anesthetized with 3% isoflurane, and hearts were rapidly excised and placed in a cold (4 °C)oxygenated (100% O ) dissection buffer to minimize ischemic injury. The dissection buffercontained 140 mM NaCl, 5.4 mM KCl, 10 mM HEPES (pH 7.4), 1.8 mM CaCl , 0.6 mM MgCl ,10 mM glucose, and 30 mM 2,3-butanedione monoxime (BDM) to prevent contraction during preparation. The heart was then dissected to remove the atria and the right ventricle. The left ventricle (LV) was cut down the septum, the LV free wall was mounted with the epicardial side down onto a magnetic metal base using Histoacryl glue (Tissue Seal, Ann Arbor, MI) at room temperature. The mounted tissue was placed in the slicing chamber of a Vibrating Microtome 7000SMZ- 2 (Camden Instruments, Loughborough, Leicestershire, UK) filled with oxygenated dissection buffer, which was maintained at 4 °C with a cold plate to preserve tissue integrity. Before each slicing procedure, the stainless-steel blade was replaced, and the Z-axis deflection was recalibrated to ensure a precision of less than 1 m. The vibratome settings were optimized for cardiac tissue, with parameters set to a vibrational frequency of 70 Hz, amplitude of 2.00 mm, slice thickness of 150 m, and an advance speed of 0.07 mm / s. The left ventricular slices were then mounted on custom laser-cut plastic cassettes (5 mm length × 3 mm width) with myofibrils aligned lengthwise to ensure consistent contractile orientation. Data Collection Slices were mounted in a recording chamber, and the sides of the scaffolds were cut to allow contraction. Slices were continuously perfused with DMEM-F12, 0.5 M PF, or 0.5 M PF + 1 M isoproterenol (ISO) (100% oxygenated). Initially, slices were paced at 1 Hz to find a spot with a good calcium signal. Following that, the pacing was increased to 2 Hz for most of the experimental procedures. In some cases, the frequency was increased to 3 Hz to see if alternans would form. Pacing conditions were biphasic 5 ms pulse waveform, 25 V, and 2 Hz frequencies. To standardize the procedure, all slices were stretched to a diastolic sarcomere length of 2.1 m. Fresh vials of DMEM F-12 were used for each slice, or ISO were added to the media 1 minute before perfusion. Slice Viability All slices were contracting after pacing. Experiment 1 – Female Mice Cardiac slices from female AKAP12OXtransgenic mice and wild-type (WT) littermates were analyzed to evaluate baseline contractility and -adrenergic responses. Slices were exposed to control media (DMEM-F12) followed by 1 μM isoproterenol (ISO). Stress-strain loops (FIG. 26A), force-time traces (FIG. 26B), and quantitative parameters; developed stress (FIG. 26C), departure velocity (FIG. 26D), and return velocity (FIG. 26E) were compared between groups. Under control conditions, AKAP12OXslices exhibited significantly higher baseline contractile parameters than WT slices. Developed stress was elevated in AKAP12OXslices compared to WT (2.23 ± 0.33, N = 5 vs.1.39 ± 0.26, N = 3), as were departure velocity (2.67 ±0.52, N = 5 vs. 1.60 ± 0.51, N = 3) and return velocity ( 1.71 ± 0.25, N = 5 vs. 0.75 ± 0.20, N =3). These findings suggest that AKAP12 overexpression enhances basal myocardial contractility, potentially through increased myofilament sensitivity or altered calcium cycling. Stress-strain loops confirmed this, with AKAP12OXloops being consistently larger than WT under DMEM-F12, indicating enhanced baseline force development. Interestingly, mechanical alternans were observed in the stress-strain loops of AKAP12OXslices in DMEM-F12, marked by beat-to-beat variability in contractile performance, marked with arrows. Alternans likely reflect dysregulated calcium handling, potentially due to altered compartmentalized signaling by AKAP12. This instability in excitation-contraction coupling may arise from imbalances in calcium release / reuptake or sarcomeric tension variability. Alternans are often precursors to arrhythmias or myocardial dysfunction, highlighting a potential vulnerability of AKAP12OXmyocardium, even under baseline conditions. ISO treatment markedly increased contractile parameters in WT slices. Developed stress(3.09 ± 0.92), departure velocity (4.13 ± 1.73), and return velocity ( 2.47 ± 0.90) were allsignificantly elevated compared to baseline (p = 0.03275, p = 0.04787, and p = 0.01975, respectively). In contrast, AKAP12OXslices showed no significant changes in any parameter following ISO treatment, despite maintaining higher absolute values compared to WT. The stress- strain loops and force-time traces demonstrated robust ISO-induced enhancements in WT slices, whereas AKAP12OXloops and force amplitudes showed only marginal changes. These findings suggest blunted -adrenergic responsiveness in AKAP12OXslices. The enhanced baseline contractility observed in AKAP12OXslices may reflect increased energetic demand or altered calcium-handling proteins, consistent with AKAP12's role in organizing compartmentalized cAMP signaling. The reduced responsiveness to ISO indicates potential saturation or desensitization of -adrenergic signaling pathways in the transgenic model. This could imply that AKAP12 overexpression promotes a hypercontractile phenotype at rest but limits the myocardium's ability to further augment contractile performance under stress. These results have implications for pathological conditions such as heart failure, where impaired - adrenergic signaling and altered baseline contractility coexist. Furthermore, mechanical alternans in AKAP12OXslices emphasize an additional level of contractile instability. Alternans, often caused by calcium-handling abnormalities, are a hallmark of myocardial dysfunction and a precursor to arrhythmias. The combined observations of alternans and diminished -adrenergic responsiveness suggest a reduced contractile reserve and heightened arrhythmogenic potential in AKAP12OXhearts. These findings could have implications for conditions such as heart failure, where altered baseline contractility, calcium dysregulation, and impaired -adrenergic signaling coexist. Experiment 2 – Male Mice Cardiac slices from male AKAP12OXtransgenic mice and wild-type (WT) littermates were analyzed to evaluate baseline contractility and -adrenergic responses. Slices were exposed to control media (DMEM-F12) followed by 1 μM isoproterenol (ISO). Stress-strain loops (FIG.27A), force-time traces (FIG.27B), and quantitative parameters; developed stress (FIG.27C), departure velocity (FIG.27D), and return velocity (FIG.27E) were compared between groups. Under DMEM-F12 conditions, AKAP12OXmale cardiac slices displayed slightly elevated baseline developed stress compared to WT slices (1.49 ± 0.53, N = 3 vs.1.17 ± 0.16, N = 4), but this difference was not statistically significant. Similarly, departure velocity was higher in AKAP12OXslices (1.76 ± 0.63, N = 3 vs. 1.25 ± 0.29, N = 4), whereas return velocity showedminor differences ( 0.99 ± 0.44, N = 3 vs. 0.80 ± 0.19, N = 4). These observations align withthe trends seen in females, where AKAP12 overexpression enhances baseline contractility. Stress-strain loops and force-time traces confirmed these findings, with larger loops in AKAP12OXslices indicative of higher basal force generation. The variability in baseline data suggests a potential heterogeneity in how AKAP12 overexpression affects male myocardium. ISO treatment significantly increased developed stress in WT slices (1.17 ± 0.16 to 1.68 ± 0.19, p = 0.03921), while no significant change was observed in AKAP12OXslices (1.49 ± 0.53 to 1.83 ± 0.36). Departure velocity also increased significantly in WT slices following ISO (1.25 ± 0.29 to 3.02 ± 0.62, p = 0.01791), but AKAP12OXslices showed a more modest increase (1.76 ± 0.63 to 2.49 ± 0.29). Return velocity followed a similar trend, with WT slices showing an increase( 0.80 ± 0.19 vs 1.79 ± 0.53) and AKAP12OX slices showing only a minor enhancement ( 0.99± 0.44 vs 1.59 ± 0.29), though neither group reached statistical significance for this parameter. Stress-strain loops and force-time traces further demonstrated a robust -adrenergic response in WT slices, with more pronounced enhancements in force and loop size compared to AKAP12OXslices, which showed blunted responses. This pattern mirrors the results seen in females and suggests impaired -adrenergic signaling in AKAP12OXmyocardium. The results highlight sex-specific differences in the impact of AKAP12 overexpression on cardiac function. Male AKAP12OXslices exhibited trends similar to females, with enhanced baseline contractility but attenuated -adrenergic responsiveness. The blunted ISO response in AKAP12-OX myocardium suggests saturation or desensitization of -adrenergic pathways, consistent with AKAP12's role in regulating compartmentalized cAMP signaling. The lack of significant alternans in male AKAP12OXslices under control conditions, as opposed to the alternans seen in females, may reflect sex-specific differences in calcium handling or sarcomeric organization. This raises the possibility of distinct susceptibilities to arrhythmogenesis or maladaptive remodeling between sexes. The findings from males reinforce the concept that AKAP12 overexpression enhances baseline contractile performance but compromises adaptability under physiological stress, posing risks for arrhythmias or heart failure.

Claims

CLAIMS What is claimed:

1. A pharmaceutical composition for maintaining or rescuing cardiac function in a cell or a subject, the pharmaceutical composition comprising a therapeutic agent targeting AKAP12 and PDE8.

2. The pharmaceutical composition of claim 1, wherein the therapeutic agent modulates expression and / or activity of AKAP12 and PDE8 in the cell or the subject.

3. The pharmaceutical composition of claim 1, wherein the therapeutic agent inhibits expression and / or activity of AKAP12 and PDE8 in the cell or the subject.

4. The pharmaceutical composition of claim 1, wherein PDE8 is PDE8A.

5. The pharmaceutical composition of claim 1, wherein the therapeutic agent comprises a nucleic acid, a polypeptide, an antibody, a small molecule, or combinations thereof.

6. The pharmaceutical composition of claim 5, wherein the therapeutic agent is a nucleic acid comprising a siRNA, a shRNA, or an antisense oligonucleotide.

7. The pharmaceutical composition of claim 1, wherein the therapeutic agent is a cardiac- specific therapeutic agent.

8. The pharmaceutical composition of claim 1, further comprising one or more pharmaceutically acceptable buffers, salts, carriers, or diluents.

9. A kit comprising: the pharmaceutical composition of claim 1; and optionally, one or more of packaging, a label, or instructions for use.

10. A method of maintaining or rescuing cardiac function in a cell or a subject, the method comprising:administering to the cell or the subject a therapeutically effective amount of the pharmaceutical composition of claim 1.

11. The method of claim 10, wherein the cell or the subject has increased expression of AKAP12 relative to a control cell or subject.

12. The method of claim 10, wherein the subject has, or is at risk of developing, heart failure.

13. The method of claim 10, wherein the method maintains or rescues cardiac contractility in the cell or the subject.

14. A method of treating or preventing cardiovascular disease in a subject, the method comprising: administering to the subject a therapeutically effective amount of the pharmaceutical composition of claim 1.

15. The method of claim 14, wherein the subject has increased expression of AKAP12 relative to a control subject.

16. The method of claim 14, wherein the subject has, or is at risk of developing, heart failure.

17. The method of claim 14, wherein the method maintains or rescues cardiac contractility in the subject.

18. Use of the pharmaceutical composition of claim 1 as a medicament for maintaining or rescuing cardiac function in a cell or a subject.

19. Use of the pharmaceutical composition of claim 1 as a medicament for treating or preventing cardiovascular disease in a subject.

Images