Carroll A G, Rhoads A R, Wagner P D
Lombardi Cancer Research Center, Georgetown University Medical Center, Washington, DC.
J Neurochem. 1990 Sep;55(3):930-6. doi: 10.1111/j.1471-4159.1990.tb04580.x.
The effect of the hydrolysis-resistant GTP analogs, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) and guanylyl imidodiphosphate (GMPPNP), on norepinephrine (NE) secretion from digitonin-permeabilized rat pheochromocytoma cells, PC12, was examined. Although secretion in the presence of saturating Ca2+ (10 microM) was not affected by GTP gamma S or GMPPNP, secretion in the absence of Ca2+ was stimulated by these GTP analogs. Secretion induced by saturating concentrations of GTP gamma S or GMPPNP was approximately 80% of that induced by 10 microM Ca2+. Half-maximum stimulation was induced by 30 microM GTP gamma S or GMPPNP. Both Ca2(+)-stimulated and GTP gamma S-stimulated secretion were ATP dependent and inhibited by N-ethylmaleimide. The GTP gamma S-stimulated secretion of NE from permeabilized PC12 cells does not appear to result from either the release of Ca2+ or the activation of protein kinase C. Activation of protein kinase C by pretreatment of intact cells with 12-O-tetradecanoylphorbol 13-acetate caused a 50% increase in both Ca2(+)-stimulated and GTP gamma S-stimulated secretion. Cholera and pertussis toxins did not affect Ca2(+)-stimulated or GTP gamma S-stimulated NE secretion. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S) and GTP inhibited GTP gamma S-stimulated secretion but not Ca2(+)-stimulated secretion. The inability of GDP beta S to inhibit Ca2(+)-stimulated secretion indicates that the process affected by GTP gamma S is not an essential step in the Ca2(+)-stimulated pathway.
研究了抗水解的GTP类似物鸟苷5'-O-(3-硫代三磷酸)(GTPγS)和鸟苷亚氨二磷酸(GMPPNP)对经洋地黄皂苷通透处理的大鼠嗜铬细胞瘤细胞PC12去甲肾上腺素(NE)分泌的影响。尽管在饱和Ca2+(10μM)存在下的分泌不受GTPγS或GMPPNP的影响，但在无Ca2+时这些GTP类似物可刺激分泌。饱和浓度的GTPγS或GMPPNP诱导的分泌约为10μM Ca2+诱导分泌的80%。30μM GTPγS或GMPPNP可诱导半数最大刺激。Ca2+刺激的和GTPγS刺激的分泌均依赖ATP并被N-乙基马来酰亚胺抑制。通透的PC12细胞中GTPγS刺激的NE分泌似乎不是由Ca2+释放或蛋白激酶C激活所致。用12-O-十四烷酰佛波醇13-乙酸酯预处理完整细胞激活蛋白激酶C后，Ca2+刺激的和GTPγS刺激的分泌均增加50%。霍乱毒素和百日咳毒素不影响Ca2+刺激的或GTPγS刺激的NE分泌。鸟苷5'-O-(2-硫代二磷酸)(GDPβS)和GTP抑制GTPγS刺激的分泌，但不抑制Ca2+刺激的分泌。GDPβS不能抑制Ca2+刺激的分泌表明GTPγS影响的过程不是Ca2+刺激途径中的必需步骤。
