Involvement of G protein betagamma-subunits in diverse signaling induced by G(i/o)-coupled receptors: study using the Xenopus oocyte expression system.
We studied the functions of betagamma-subunits of G(i/o) protein using the Xenopus oocyte expression system. Isoproterenol (ISO) elicited cAMP production and slowly activating Cl(-) currents in oocytes expressing beta(2)-adrenoceptor and the protein kinase A-dependent Cl(-) channel encoded by the cystic fibrosis transmembrane conductance regulator (CFTR) gene. 5-Hydroxytryptamine (5-HT), [d-Ala(2), d-Leu(5)]-enkephalin (DADLE), and baclofen enhanced ISO-induced cAMP levels and CFTR currents in oocytes expressing beta(2)-adrenoceptor-CFTR and 5-HT(1A) receptor (5-HT(1A)R), delta-opioid receptor, or GABA(B) receptor, respectively. 5-HT also enhanced pituitary adenylate cyclase activating peptide (PACAP) 38-induced cAMP levels and CFTR currents in oocytes expressing PACAP receptor, CFTR and 5-HT(1A)R. The 5-HT-induced enhancement of G(s)-coupled receptor-mediated currents was abrogated by pretreatment with pertussis toxin (PTX) and coexpression of G transducin alpha (G(t)alpha). The 5-HT-induced enhancement was further augmented by coexpression of the Gbetagamma-activated form of adenylate cyclase (AC) type II but not AC type III. Thus betagamma-subunits of G(i/o) protein contribute to the enhancement of G(s)-coupled receptor-mediated responses. 5-HT and DADLE did not elicit any currents in oocytes expressing 5-HT(1A)R or delta-opioid receptor alone. They elicited Ca(2+)-activated Cl(-) currents in oocytes coexpressing these receptors with the Gbetagamma-activated form of phospholipase C (PLC)-beta2 but not with PLC-beta1. These currents were inhibited by pretreatment with PTX and coexpression of G(t)alpha, suggesting that betagamma-subunits of G(i/o) protein activate PLC-beta2 and then cause intracellular Ca(2+) mobilization. Our results indicate that betagamma-subunits of G(i/o) protein participate in diverse intracellular signals, enhancement of G(s)-coupled receptor-mediated responses, and intracellular Ca(2+) mobilization.
Uezono
Yasuhito
Y
Department of Pharmacology, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki 852-8523, Japan. uezonoy@alpha.med.nagasaki-u.ac.jp
Kaibara
Muneshige
M
Murasaki
Osamu
O
Taniyama
Kohtaro
K
D000818:Animals; D020013:Calcium Signaling / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000502:physiology; D004594:Electrophysiology; D044387:GTP-Binding Protein beta Subunits / Q000502:physiology*; D006801:Humans; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D014981:Xenopus
C505032:CFTR protein, human; D044387:GTP-Binding Protein beta Subunits; D043562:Receptors, G-Protein-Coupled; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D000242:Cyclic AMP