title: Single amino acid of an octopamine receptor as a molecular switch for distinct G protein couplings.
abstract: Octopamine (OA) is thought to be the invertebrate counterpart of noradrenaline and regulates various behavioral patterns of invertebrates by activating OA receptors. As a typical G protein-coupled receptor, BmOAR1, a Bombyx mori alpha-adrenergic-like OA receptor, is coupled to both G(s) and G(q) proteins to induce the release of the intracellular second messengers cAMP and Ca(2+). In this study, we examined the pharmacological and functional properties of the cloned OA receptor, using OA enantiomers. The wild-type OA receptor exhibited significant stereoselectivity for OA enantiomers in cAMP production and binding affinity, but not in calcium signaling response. On the contrary, the Y412F mutant abolished the discrimination between OA enantiomers in the binding affinity and did not evoke any cAMP signaling response. This mutant exhibited levels of potency and efficacy similar to those of the wild-type receptor in the calcium assays. Taken together, these results suggest that Tyr412 might act as a molecular switch to regulate distinct G protein couplings, and a sequential activation model is proposed for such specific-residue-dependent, selective activation in receptors that are coupled to multiple G proteins.
authors.affiliation: Department of Life Science and Biotechnology, Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan.
authors.forename: Jia
authors.initials: J
authors.lastname: Huang
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Hamasaki
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Ozoe
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Ozoe
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D012831:Bombyx; D002460:Cell Line; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D009655:Octopamine / Q000494:pharmacology; D011487:Protein Conformation; D017982:Receptors, Biogenic Amine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017982:Receptors, Biogenic Amine; C027604:norsynephrine receptor; D009655:Octopamine; D014443:Tyrosine; D019204:GTP-Binding Proteins