Specific G alpha(11)beta(3)gamma(5) protein involvement in endothelin receptor-induced phosphatidylinositol hydrolysis and Ca2+ release in rat portalvein myocytes

In this study, we identified the receptor subtype activated by endothelin-1 (ET-1) and the subunit composition of the G protein coupling this receptor to increase in cytosolic Ca2+ concentration in rat portal vein myocytes. W e used intranuclear antisense oligonucleotide injection to selectively inhi bit the expression of G protein subunits. We show here that the endothelin receptor subtype A (ETA)-mediated increase in cytosolic Ca2+ concentration was mainly dependent on Ca2+ release from the intracellular store. ETA rece ptor-mediated Ca2+ release was selectively inhibited by antisense oligonucl eotides that inhibited the expression of alpha(11), beta(3), and gamma(5) s ubunits, as checked by immunocytochemistry. Intracellular dialysis of a car boxyl terminal anti-beta(com) antibody and a peptide corresponding to the G beta gamma binding region of the beta-adrenergic receptor kinase-1 had no effect on the ETA receptor-mediated Ca2+ release. In contrast, a synthetic peptide corresponding to the carboxyl terminus of the alpha(q)/alpha(11) su bunit, heparin (an inhibitor of inositol 1,4,5-trisphosphate receptors), an d U73122 (an inhibitor of phosphatidylinositol-phospholipase G) inhibited, in a concentration-dependent manner, the ETA receptor-mediated Ca2+ respons es. Accumulation of [H-3]inositol trisphosphate evoked by norepinephrine pe aked at similar to 15 s, whereas that evoked by ET-1 progressively increase d within 2 min. In myocytes injected with anti-alpha(q) antisense oligonucl eotides, both amplitude and time course of the norepinephrine-induced Ca2release became similar to those of the ET-1-induced Ca2+ response. We concl ude that the ETA receptor-mediated Ca2+ release is selectively transduced b y the heterotrimeric G(11) protein composed of alpha(11), beta(3), and gamm a(5) subunits, and that a delayed stimulation of phospholipase C occurs via the alpha(11) subunit.