Subtype‐Selective Immunoprecipitation of the β2‐Adrenergic Receptor

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Abstract
Most antibodies known to interact with β‐adren‐ergic 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 β2‐adrenergic receptor of hamster, is selective for the β2 subtype. G27.1 provides nearly quantitative immunoprecipitation of the β2‐acjrenergic 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 β2‐adrenergic receptors from three rodent species, but not with those from humans. When C6 glioma cells, which contain both β1 ‐ and β2‐adrenergic receptors, are photoaffinity‐labeled in the absence or presence of subtype‐selective antagonists, subtype‐selective photoaffinity‐labeling results. G27.1 can immunoprecipitate β‐, but not β1‐, adrenergic receptors from these cells. Similar results were obtained following subtype‐selective photoaffinity‐labeling of membranes from rat cerebellum and cerebral cortex. The β‐adrenergic receptors from C6 glioma cells and rat cerebral cortex exist as a mixture of two molecular weight species. These species differ in glycos‐ylation, as shown by endoglycosidase F digestion of crude and immunoprecipitated receptors.