Distinct functions of G sub(q) and G sub(11) proteins in coupling alpha sub(1)-adrenoreceptors to Ca super(2+) release and Ca super(2+) entry in rat portal vein myocytes

• Published in: The Journal of biological chemistry 1997-02, Vol.272 (8), p.5261-5268
• Main Authors: Macrez-Lepretre, N, Kalkbrenner, F, Schultz, G, Mironneau, J
• Format: Article
• Language: English
• ISSN: 0021-9258

In this study, we identified the subunit composition of G sub(q) and G sub(11) proteins coupling alpha sub(1)-adrenoreceptors to increase in cytoplasmic Ca super(2+) concentration ([Ca super(2+)] sub(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 [Ca super(2+)] sub(i) were measured in response to activation of alpha sub(1)-adrenoreceptors, angiotensin AT sub(1) receptors, and caffeine. Antisense oligonucleotides directed against the mRNAs coding for alpha sub(q), alpha sub(11), beta sub(1), beta sub(3), gamma sub(2), and gamma sub(3) subunits selectively inhibited the increase in [Ca super(2+)] sub(i) activated by alpha sub(1)-adrenoreceptors. A corresponding reduction of the expression of these G protein subunits was immunochemically confirmed. In experiments performed in Ca super(2+)-free solution only cells injected with anti- alpha sub(q) antisense oligonucleotides displayed a reduction of the alpha sub(1)-adrenoreceptor-induced Ca super(2+) release. In contrast, in Ca super(2+)-containing solution, injection of anti- alpha sub(11) antisense oligonucleotides suppressed the alpha sub(1)-adrenoreceptor-induced stimulation of the store-operated Ca super(2+) influx. Agents that specifically bound G beta gamma subunits (anti- beta sub(com) antibody and overexpression of a beta -adrenergic receptor kinase carboxyl-terminal fragment) had no effect on the alpha sub(1)-adrenoreceptor-induced signal transduction. Taken together, these results suggest that alpha sub(1)-adrenoreceptors utilize two different G alpha subunits to increase [Ca super(2+)] sub(i). G alpha sub(q) may activate phosphatidylinositol 4,5-bisphosphate hydrolysis and induce release of Ca super(2+) from intracellular stores. G alpha sub(11) may enhance the Ca super(2+)-activated Ca super(2+) influx that replenishes intracellular Ca super(2+) stores.