Agonist-induced release of splice variants of the α subunit of the stimulatory G-protein from rat cardiac membranes

• Verfasst von: Witte, Klaus [VerfasserIn]
• Verfasst von: Schnecko, Anke [VerfasserIn]
• Verfasst von: Lemmer, Björn [VerfasserIn]
• Titel: Agonist-induced release of splice variants of the α subunit of the stimulatory G-protein from rat cardiac membranes
• Verf.angabe: Klaus Witte, Anke Schnecko and Björn Lemmer
• E-Jahr: 1999
• Jahr: 28 January 1999
• Umfang: 5 S.
• Fussnoten: Gesehen am 28.04.2022
• Titel Quelle: Enthalten in: Biochemical pharmacology
• Ort Quelle: Amsterdam [u.a.] : Elsevier Science, 1958
• Jahr Quelle: 1999
• Band/Heft Quelle: 57(1999), 5, Seite 539-543
• ISSN Quelle: 1873-2968
• DOI: doi:10.1016/S0006-2952(98)00335-9
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: adenylyl cyclase
• Sach-SW: Gα isoforms
• Sach-SW: immunoblotting
• Sach-SW: rat heart ventricle
• Sach-SW: signal transduction
• Sach-SW: subunit release
• K10plus-PPN: 1800495234

Abstract

It was the aim of the present study to evaluate whether, in physiological cardiac tissue, long and short splice variants of Gsα (the alpha subunit of the stimulatory G-protein) differ in their susceptibility to guanine nucleotide-mediated activation. As a measure of Gsα activation, we determined the proportion of Gsα subunits which were released from the plasma membrane upon stimulation. Membrane preparations from heart ventricles of Wistar rats were incubated with increasing concentrations of the non-hydrolyzable GTP analogue guanylyl-imidodiphosphate (GppNHp, 0-100 μmol/L) in the absence or presence of the β-adrenoceptor agonist isoprenaline (1 μmol/L). The 45 and 52 kDa forms of Gsα (Gsα-S and -L, respectively) were measured in the supernatant of the incubation mixture by immunoblotting and densitometry. The increase in cyclic AMP induced by GppNHp was measured in the same supernatant. In the absence of isoprenaline, GppNHp increased cyclic AMP formation and the concentration-dependent release of Gsα-L (Friedman test, P < 0.05), whereas the amount of soluble Gsα-S was not affected. After addition of isoprenaline, the redistribution of Gsα-S into the soluble fraction could be stimulated by GppNHp in a concentration-dependent manner (P < 0.05). Kinetic experiments revealed that activation of Gsα-S by GppNHp was rather slow, but could be markedly enhanced by isoprenaline. Thus, it is likely that the different susceptibilities of Gsα-S and -L towards GppNHp reflects differences in the rate of spontaneous GDP release.