Compositions and methods for regulating receptor clustering

Abstract

The invention relates to isolated complexes comprising one or more galectin associated with a Mgat5 modified glycan or polylactosamine modified glycan, and isolated lectin-Mgt5 modified glycan lattice comprising an array of mulitvalent interactions among lectins, Mgat5 modified glycans, polylactosamine modified glycans, and / or glycoproteins. Methods for evaluating a test compound for its ability to regulate receptor clustering through glycans on cell surfaces; and methods for regulating receptor clustering on cell surfaces comprising altering glycans on the cell surface associated with receptor clustering are also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. patent application Ser. No. 10 / 250,935, filed Dec. 15, 2003, which is a US national stage of International Patent Application No. PCT / CA02 / 00002, filed Jan. 11, 2002, which claims the benefit of the priority of U.S. Provisional Patent Application No. 60 / 261,516, filed Jan. 12, 2001, now abandoned.FIELD OF THE INVENTION[0002]The invention relates to complexes, lattices, compositions and methods for regulating receptor clustering on cell surfaces.BACKGROUND OF THE INVENTION[0003]N- and O-linked glycans are found on both cell-surface and secreted proteins, many of which control proliferation and cell fate decisions in animals. Tissue-specific expression of glycosyltransferases is a significant factor controlling the glycan profiles observed in differentiated cells (Paulson, Jc and Colley K J, J Biol Chem 1989, 264:17615-17618). In addition, many glycosyltransferases compete for acceptor intermediates ...

AI Technical Summary

Benefits of technology

[0005]Applicants have demonstrated that differential receptor glycosylation effects ligand-dependent clustering of receptors. Applicants illustrated the effects of differential receptor glycosylation with T cell receptors (TCR). T cell activation requires clustering of a threshold number of T cell receptors (TCR) at the site of antigen presentation, a number that is reduced by CD28 co-receptor recruitment of signaling proteins to TCR (1-5). Applicants demonstrate that a deficiency in β1,6N-acetylglucosaminyltransferase V (Mgat5), an enzyme in the N-glycosylation pathway, lowers T cell activation thresholds by directly enhancing TCR clustering. MGat5-deficient mice displayed kidney autoimmune disease, enhanced delayed type hypersensitivity, and increased susceptibility to experimental autoimmune encephalomyelitis. Thus, dysregulation of Mgat5 in humans may increase susceptibility to autoimmune diseases such as multiple sclerosis.

[0006]Recruitment of TCR to agonist-coated beads, TCR signaling, actin microfilament reorganization and agonist-induced proliferation were enhanced in Mgat5− / − T cells. Mgat5 initiates GlcNAc β1,6 branching on N-glycans, thereby increasing N-acetyllactosamine (6), the lectin for galectins (7, 8) proteins known to modulate T cell proliferation and apoptosis (9, 10). Indeed, galectin-3 was associated with the TCR complex at the cell surface, an interaction dependent on Mgat5. Pre-treatment of wild type T cells with lactose to compete for galectin binding produced a phenocopy of Mgat5− / − TCR clustering. These data indicate that a galectin-glycoprotein lattice strengthened by Mgat5-modified glycans restricts TCR recruitment to the site of antigen presentation.

Problems solved by technology

In addition, many glycosyltransferases compete for acceptor intermediates causing bifurcations of the pathways and additional structural complexity (Schachter H, Biochem Cell Biol 1986, 64:163-181).

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