Subtype-selective immunoprecipitation of the beta 2-adrenergic receptor

Most antibodies known to interact with beta-adrenergic receptors do not exhibit subtype selectivity, nor do they provide quantitative immunoprecipitation. A monoclonal antibody, G27.1 raised against a synthetic peptide corresponding to the C-terminus of the beta 2-adrenergic receptor of hamster, is selective for the beta 2 subtype. G27.1 provides nearly quantitative immunoprecipitation of the beta 2-adrenergic receptor from hamster lung that has been photoaffinity-labeled and solubilized with sodium dodecyl sulfate. Immunoprecipitation is completely blocked by nanomolar concentrations of the immunizing peptide. This antibody interacts with beta 2-adrenergic receptors from three rodent species, but not with those from humans. When C6 glioma cells, which contain both beta 1- and beta 2-adrenergic receptors, are photoaffinity-labeled in the absence or presence of subtype-selective antagonists, subtype-selective photoaffinity-labeling results. G27.1 can immunoprecipitate beta 2-, but not beta 1-, adrenergic receptors from these cells. Similar results were obtained following subtype-selective photoaffinity-labeling of membranes from rat cerebellum and cerebral cortex. The beta-adrenergic receptors from C6 glioma cells and rat cerebral cortex exist as a mixture of two molecular weight species. These species differ in glycosylation, as shown by endoglycosidase F digestion of crude and immunoprecipitated receptors.