title: Characterization of the G protein involved in the muscarinic stimulation of adenylyl cyclase of rat olfactory bulb.
abstract: We investigated the identity of the G protein mediating the muscarinic stimulation of adenylyl cyclase in rat olfactory bulb membranes by examining the sensitivity of this response to selective anti-G protein antisera. Preincubation of tissue membranes with the antisera AS/7 (anti-Gi1/2 alpha), EC/2 (anti-Gi3 alpha/Go alpha), and GO/1 (anti-G(o) alpha) but not with the antiserum QL (anti-Gq/11 alpha) significantly attenuated the carbachol-stimulated adenylyl cyclase activity. These antisera had no effect on the enzyme activity stimulated by the beta-adrenergic agonist L-isoproterenol. On the other hand, the anti-Gs alpha antiserum RM/1 markedly depressed both carbachol- and L-isoproterenol-stimulated adenylyl cyclase activities. This antiserum also reduced the basal enzyme activity to a similar extent. However, different than the anti-Gi/Go antisera, the RM/1 antiserum failed to affect the carbachol-stimulated [35S]guanosine 5'-O-(3-thiotriphosphate) binding to membrane G proteins, whereas it curtailed the [35S]guanosine 5'-O-(3-thiotriphosphate) binding stimulated by pituitary adenylate cyclase-activating peptide. Exposure to either pertussis toxin or the anti-Go alpha antiserum 9072 but not to cholera toxin or the anti-Gs alpha antiserum 1191 reduced the high-affinity binding of oxotremorine M to muscarinic receptors. Moreover, the labeling of a 45-kDa protein catalyzed by cholera toxin was markedly stimulated by pituitary adenylate cyclase-activating peptide but not by carbachol. These data indicate that in rat olfactory bulb membranes, muscarinic receptors interact with both Gi and Go and that these G proteins mediate the stimulation of adenylyl cyclase. Although this response appears to require Gs activity, no evidence was found for the direct coupling of muscarinic receptors to Gs.
authors.affiliation: Department of Neurosciences, University of Cagliari, Italy.
authors.forename: M C
authors.initials: MC
authors.lastname: Olianas
authors.forename: P
authors.initials: P
authors.lastname: Onali
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D002217:Carbachol / Q000494:pharmacology*; D002772:Cholera Toxin / Q000494:pharmacology; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000276:immunology / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007106:Immune Sera; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology*; D019832:N-Methylscopolamine; D009479:Neuropeptides / Q000494:pharmacology; D009830:Olfactory Bulb / Q000201:enzymology*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051381:Rats; D017207:Rats, Sprague-Dawley; D012602:Scopolamine Derivatives / Q000378:metabolism; D014316:Tritium
chemical_list: C495403:Adcyap1 protein, rat; D007106:Immune Sera; D018721:Muscarinic Agonists; D009479:Neuropeptides; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D012602:Scopolamine Derivatives; D014316:Tritium; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002217:Carbachol; D002772:Cholera Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D019832:N-Methylscopolamine