Distinct functions of Gq and G11 proteins in coupling alpha1-adrenoreceptors to Ca2+ release and Ca2+ entry in rat portal vein myocytes.
In this study, we identified the subunit composition of Gq and G11 proteins coupling alpha1-adrenoreceptors to increase in cytoplasmic Ca2+ concentration ([Ca2+]i) in rat portal vein myocytes maintained in short-term primary culture. We used intranuclear antisense oligonucleotide injection to inhibit selectively the expression of subunits of G protein. Increases in [Ca2+]i were measured in response to activation of alpha1-adrenoreceptors, angiotensin AT1 receptors, and caffeine. Antisense oligonucleotides directed against the mRNAs coding for alphaq, alpha11, beta1, beta3, gamma2, and gamma3 subunits selectively inhibited the increase in [Ca2+]i activated by alpha1-adrenoreceptors. A corresponding reduction of the expression of these G protein subunits was immunochemically confirmed. In experiments performed in Ca2+-free solution only cells injected with anti-alphaq antisense oligonucleotides displayed a reduction of the alpha1-adrenoreceptor-induced Ca2+ release. In contrast, in Ca2+-containing solution, injection of anti-alpha11 antisense oligonucleotides suppressed the alpha1-adrenoreceptor-induced stimulation of the store-operated Ca2+ influx. Agents that specifically bound Gbetagamma subunits (anti-betacom antibody and overexpression of a beta-adrenergic receptor kinase carboxyl-terminal fragment) had no effect on the alpha1-adrenoreceptor-induced signal transduction. Taken together, these results suggest that alpha1-adrenoreceptors utilize two different Galpha subunits to increase [Ca2+]i. Galphaq may activate phosphatidylinositol 4,5-bisphosphate hydrolysis and induce release of Ca2+ from intracellular stores. Galpha11 may enhance the Ca2+-activated Ca2+ influx that replenishes intracellular Ca2+ stores.
Macrez-Leprêtre
N
N
Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, CNRS ESA 5017, Université de Bordeaux II, 146 rue Léo Saignat, 33076 Bordeaux Cedex, France.
Kalkbrenner
F
F
Schultz
G
G
Mironneau
J
J
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000378:metabolism*; D017136:Ion Transport; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011169:Portal Vein / Q000378:metabolism*; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*
D018340:Receptors, Adrenergic, alpha-1; D019204:GTP-Binding Proteins; D002118:Calcium