Specific G alpha(11)beta(3)gamma(5) protein involvement in endothelin receptor-induced phosphatidylinositol hydrolysis and Ca2+ release in rat portalvein myocytes
N. Macrez et al., Specific G alpha(11)beta(3)gamma(5) protein involvement in endothelin receptor-induced phosphatidylinositol hydrolysis and Ca2+ release in rat portalvein myocytes, MOLEC PHARM, 55(4), 1999, pp. 684-692
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.