Chen F, Van Dop C, Wetzel G T, Lee R H, Friedman W F, Klitzner T S
Department of Pediatrics, University of California, Los Angeles 90095-1742.
Biochem Biophys Res Commun. 1995 Nov 2;216(1):190-7. doi: 10.1006/bbrc.1995.2609.
We investigated the effects of added beta gamma subunits of G proteins (G beta gamma) on beta-adrenergic responsiveness of transmembrane Ca2+ currents (ICa) in ventricular myocytes from neonatal rabbits. G beta 1 gamma 1 purified from retinal rods was dialyzed into cells via the voltage clamp micro-electrode. Stimulation of ICa by isoproterenol was not affected by added intracellular G beta 1 gamma 1 or by carbachol alone but was completely blocked by combined G beta 1 gamma 1 and carbachol. Pretreatment of cells with pertussis toxin or temporal separation of carbachol and isoproterenol allowed stimulation of ICa by isoproterenol in cells dialyzed with G beta 1 gamma 1. Carbachol and G beta 1 gamma 1 together also did not prevent stimulation of ICa by dibutyryl-cyclic AMP. Thus, rather than simply inactivating Gs alpha by mass action, G beta 1 gamma 1 acts in concert with carbachol to inhibit isoproterenol stimulation of ICa.
我们研究了添加G蛋白的βγ亚基（Gβγ）对新生兔心室肌细胞跨膜Ca2+电流（ICa）的β-肾上腺素能反应性的影响。从视网膜杆状细胞纯化的Gβ1γ1通过电压钳微电极透析到细胞中。异丙肾上腺素对ICa的刺激不受细胞内添加的Gβ1γ1或单独的卡巴胆碱的影响，但被Gβ1γ1和卡巴胆碱联合使用完全阻断。用百日咳毒素预处理细胞或使卡巴胆碱和异丙肾上腺素暂时分开，可使在用Gβ1γ1透析的细胞中异丙肾上腺素刺激ICa。卡巴胆碱和Gβ1γ1共同作用也不能阻止二丁酰环磷酸腺苷对ICa的刺激。因此，Gβ1γ1并非简单地通过质量作用使Gsα失活，而是与卡巴胆碱协同作用，抑制异丙肾上腺素对ICa的刺激。
