title: Antibodies directed against transducin beta subunits interfere with the regulation of adenylate cyclase activity in brain membranes.
abstract: In an attempt to study the mechanisms of action of membrane-bound adenylate cyclase, we have applied to rat brain synaptosomal membranes antibodies raised against purified bovine transducin (T) beta gamma subunits. The antibodies recognized one 36-kDa protein in Western blots of the membranes. Adenylate cyclase activation by GTP non-hydrolyzable analogues was greatly decreased in immune, as compared to preimmune, antibody-treated membranes, whereas the enzyme basal activity was unaffected by both types of antibodies. The inhibition of forskolin-stimulated adenylate cyclase by guanine 5'-(beta, gamma-imino)triphosphate (Gpp-(NH)p) was decreased in membranes preincubated with immune, but not preimmune, antibodies. Anti-T beta antibodies moderately decreased the extent of subsequent adenylate cyclase activation by forskolin, while not affecting activation by Al3+/F-. The enzyme activation by Gpp(NH)p in untreated membranes remained the same upon further incubation in the presence of either type of antibodies. Such results were consistent with the decreased exchange of guanine nucleotides which occurred in membrane treated with immune, but not preimmune antibodies, upon addition of GTP. The blockade of the regulation of adenylate cyclase by Gpp(NH)p observed in membranes pretreated by anti-T beta antibodies thus appears to be caused by the impairment of the guanine nucleotide exchange occurring on Gs alpha subunits. The G beta subunits in the adenylate cyclase complex seem to be instrumental in the guanine nucleotide exchange on G alpha subunits, just as T beta subunits are in the transducin complex.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007425:Intracellular Membranes / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D008565:Membrane Proteins / Q000378:metabolism*; D051381:Rats; D013574:Synaptosomes / Q000201:enzymology; D015293:Transducin
chemical_list: D000906:Antibodies; D000936:Antigen-Antibody Complex; D046911:Macromolecular Substances; D008565:Membrane Proteins; D019204:GTP-Binding Proteins; D015293:Transducin; D000262:Adenylyl Cyclases