The Prevalence, Maintenance, and Relevance of G Protein–Coupled Receptor Oligomerization

Abstract

Over the past decade, ideas and experimental support for the hypothesis that G protein-coupled receptors may exist as dimeric or oligomeric complexes moved initially from heresy to orthodoxy, to the current situation in which the capacity of such receptors to interact is generally accepted but the prevalence, maintenance, and relevance of such interactions to both pharmacology and function remain unclear. A vast body of data obtained following transfection of cultured cells is still to be translated to native systems and, even where this has been attempted, results often remain controversial and contradictory. This review will consider approaches that are currently being applied and why these might be challenging to interpret, and will suggest means to overcome these limitations.

The Molecular Basis of Oligomeric Organization of the Human M3Muscarinic Acetylcholine Receptor

“…1E). As also shown previously for a related hM 3 R construct (Milligan, 2013), these oligomeric forms were separated into differentially N-glycosylated forms of monomeric VSV-SNAP-hM 3 R when SDS [1% (w/v)] was added to the samples prior to addition to the Blue Native gel (Fig. 1E).…”

“…The implications of such protein-protein interactions for regulating receptor trafficking and ligand pharmacology have been widely considered in recent times (Milligan, 2009;Lohse, 2010). Despite this, identification of the structural elements governing the dimerization/oligomerization of this class of receptors has been challenging (Milligan, 2013;Ferre et al, 2014). An understanding of the basis of such interactions is essential to better understand how GPCRs function at the molecular level.…”

“…However, evidence accumulated over the past two decades indicates that they may also form and function, at least in part, as dimers or higher order oligomers (Milligan, 2004(Milligan, , 2013Ferre et al, 2014). The implications of such protein-protein interactions for regulating receptor trafficking and ligand pharmacology have been widely considered in recent times (Milligan, 2009;Lohse, 2010).…”

Coupling of G Proteins to Reconstituted Monomers and Tetramers of the M2 Muscarinic Receptor

“…Oligomers (9 -15) and monomers (16 -18) have been detected in live cells by means of receptors labeled with fluorescent or bioluminescent probes. Evidence for the existence of both species, therefore, is persuasive (8,19), but their prevalence and biological roles remain unclear, and their relevance to signaling in particular has become a vexed question.…”

Phage display and hybridoma generation of antibodies to human CXCR2 yields antibodies with distinct mechanisms and epitopes

“…29,30 Furthermore, they undergo post-translational modifications, and there is increasing evidence that they may form oligomers, with both homo and hetero-oligomerisation of GPCRs reported. 31,32 To address these challenges a variety of different antigen presentation methods have been employed for use in both immunization and antibody library display approaches with varying degrees of success. These include whole cells, purified proteins and linear peptides or constrained peptides that mimic extracellular loops to represent a more native structure.…”