Chimeric GPCR Phosphopeptide Ligation for Allosteric Modulator Screening
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Solution Overview
Problem
Current methods for selecting allosteric modulators for G protein-coupled receptors (GPCRs) are laborious and prone to artifacts, with limited compound throughput, and there is a need for compositions and methods to uniformly phosphorylate receptors for identifying compounds that modulate GPCR activity, particularly for the β2-adrenergic receptor.
Innovation Solution
A chimeric GPCR comprising the amino acid sequence LPETGGG with a synthetic phosphopeptide ligated to its C-terminus and bound to β-arrestin, used in affinity-based screening to identify positive allosteric small molecules that enhance orthosteric agonist binding and stabilize active receptor states, specifically for the β2AR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cell-based functional assays are used to select allosteric modulators, then the method is established and widely used, but the process is laborious, prone to artifacts, and has limited compound throughput
Solution Approach 1:
The patent replaces conventional cell-based functional assays with an affinity-based screening method using purified phosphorylated GPCR and β-arrestin proteins. This substitution eliminates the complexity and artifacts inherent in cellular systems while enabling high-throughput screening of compound libraries, directly resolving the contradiction between assay reliability and compound throughput.
Solution Approach 2:
The patent extracts the essential components (phosphorylated GPCR and β-arrestin) from the complex cellular environment to create a simplified in vitro system. This extraction removes confounding variables present in cell-based assays while preserving the core interaction mechanism, enabling both high reliability and high throughput in modulator selection.
2Stability of the object's composition
If GPCRs are phosphorylated heterogeneously in cellular contexts, then natural phosphorylation patterns are maintained, but uniform phosphorylation for consistent β-arrestin binding cannot be achieved
Solution Approach 1:
The patent performs preliminary phosphorylation of the GPCR C-terminus using sortase-mediated ligation of synthetic phosphopeptides before conducting affinity screening. This pre-phosphorylation ensures uniform and consistent phosphorylation states across all receptor molecules, which is essential for reliable and reproducible β-arrestin binding interactions in the screening assay.
3Adaptability or versatility
If orthosteric binding site is targeted for drug development, then vast array of ligands can be recognized, but competitive inhibition mechanisms limit therapeutic innovation
Solution Approach 1:
The patent uses β-arrestin as an intermediary to identify allosteric modulators that bind to sites distinct from the orthosteric binding pocket. These modulators can enhance or inhibit GPCR signaling without competing with endogenous ligands for the orthosteric site, thereby avoiding competitive inhibition side effects while maintaining ligand recognition versatility through allosteric mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach allows for the identification of compounds that exhibit positive cooperativity with orthosteric agonists and β-arrestin, potentiating downstream cAMP production and β-arrestin recruitment, while being specific to the β2AR compared to its closely related subtype β1AR, thereby offering a more precise and efficient method for developing therapeutic agents.
Implementation Method 1
sortase-mediated ligation of a synthetic phosphopeptide to the C-terminus of GPCRs
Implementation Method 2
βarr binds to receptors through a two-step process, initially interacting with GRK-phosphorylated residues
Implementation Method 3
allosteric compounds exert their effects by modulating receptor responsiveness to endogenous agonists
Implementation Method 4
stabilize active receptor states
Implementation Method 5
affinity-based screening of over 500 million distinct library compounds
Data Source
AI summary
The disclosure is directed to a G-protein coupled receptor complex. The complex includes (i) a chimeric G protein-coupled receptor (GPCR) comprising a non-native amino acid sequence located within the C-terminus of the GPCR and a synthetic phosphopeptide ligated to the non-native amino acid sequence; and (ii) a β-arrestin (βarr) protein bound to the C-terminus of the GPCR. The disclosure also provides an in vitro method for producing the aforementioned complex, as well as methods for identifying compounds or ligands which bind to and modulate the activity of the complex. Positive allosteric modulators of the β2 adrenergic receptor identified by screening a DNA-encoded library potentiate the activity of β2 agonists and have application in the treatment of obstructive airway disease, bronchospasm, or pre-term labor.