Abstract
The regulators of G protein signaling (RGS) proteins are a large family of evolutionarily conserved proteins that function as negative regulators of GTP-binding proteins, and we previously reported that they also function as kinetic accelerators of turning -on and -off of G protein mediated responses. We isolated RGS related cDNA clones from medaka fish skin with a view to seeking RGSs related to actual physiological phenomena, i.e. changes of the skin color. MeRGS2, homologous to mammalian RGS2, was primarily localized in the heart and the skin of medaka fish. MeRGS2 exhibited uniform subcellular distribution under basal conditions, and it translocated to cell membrane when constitutively active mutant of Gαo was co-expressed. MeRGS2 was co-immunoprecipitated with an activated Gαq and Gαi/o protein. We next analyzed electrophysiologically the effects of MeRGS2 on Gq- and Gi/o- mediated responses under the two-electrode voltage clamp in Xenopus oocytes. When MeRGS2 was co-expressed with Gq-coupled muscarinic acetylcholine (mACh) type 1 receptor, it strongly suppressed Gq-mediated Ca2+ activated Cl− current in an expression level dependent manner. By co-expressing MeRGS2 with G protein-gated inwardly rectifying K+ (GIRK) 1/2 channels and Gi/o-coupled mACh type 2 receptor, it accelerated the turning -on and -off of Gi/o-mediated modulation of GIRK current. These biochemical and electrophysiological results show that MeRGS2 serves as RGS for both Gq and Gi/o proteins. [Jpn J Physiol 54 Suppl:S129 (2004)]
