Oligomerization of G-protein-coupled receptors shown by selective co-immunoprecipitation

Abstract

Recent studies have shown that G-protein-coupled receptors (GPCRs) can assemble as high molecular weight homo- and hetero-oligomeric complexes. This can result in altered receptor-ligand binding, signaling, or intracellular trafficking. We have co-transfected HEK-293 cells with differentially epitope-tagged GPCRs from different subfamilies and determined whether oligomeric complexes were formed by co-immunoprecipitation and immunoblot analysis. This gave the surprising result that the 5HT1A receptor was capable of forming hetero-oligomers with all GPCRs tested including the 5HT1B, 5HT1D, EDG1, EDG3, GPR26, and GABAB2 receptors. The testing of other GPCR combinations showed similar results with hetero-oligomer formation occurring for the 5HT1D with the 5HT1B and EDG1 receptor. Control studies showed that these complexes were present in cotransfected cells before the time of lysis and that the hetero-oligomers were comprised of GPCRs at discrete stoichiometries. These findings suggest that GPCRs have a natural tendency to form oligomers when cotransfected into cells. Future studies should therefore investigate the presence and physiological role of GPCR hetero-oligomers in cells in which they are endogenously expressed.