Functional Complementation and the Analysis of GPCR Dimerization

摘要: Cloning of complementary DNAs (cDNAs), which are predicted to encode G protein-coupled receptors (GPCRs), required a mechanism ascertain if the single polypeptide encoded by such cDNAs was sufficient generate pharmacology and function anticipated for receptor in question. Because this generally case—and despite evidence greater complexity (reviewed ref. 1)—it became axiomatic that GPCRs were single, seven-transmembrane-span polypeptides. However, series immunoblotting studies has suggested fraction cellular might exist as dimers or higher order species both transfected cell lines native tissues (2, 3, 4). The known propensity hydrophobic proteins aggregate—particularly when samples heated prior separation sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)—meant it possible disregard these data. differentially epitope-tagged forms GPCR could be co-immunoprecipitated following their co-expression heterologous provided considerable presence dimeric or, indeed, oligomeric complexes (2,5). This not observed two expressed separate populations mixed membrane solubilization immunoprecipitation. These results indicate co-immunoprecipitation did result simply from aggregation transmembrane elements polypeptides removal lipid treatment with detergents. Equivalent then began examine proclivity different, co-expressed co-immunoprecipitated. have produced large body supporting capacity heterodimers/-oligomers (for review, see refs. 6 7). reported very broad particular allow (8) questioned relevance data is accompanied similar alternative strategies.