Halenda S P, Volpi M, Zavoico G B, Sha'afi R I, Feinstein M B
FEBS Lett. 1986 Aug 18;204(2):341-6. doi: 10.1016/0014-5793(86)80840-7.
Intact platelets were stimulated with thrombin and the amount of GTP-binding protein (G-protein) oligomers was assessed by measuring ADP ribosylation of 40-41 kDa protein by pertussis toxin in isolated membranes. The toxin substrate fell by 57-62% in 10-60 s, but then returned towards normal over 5 min. Recovery was greatly enhanced by removal of thrombin from receptors with hirudin. Phorbol myristate acetate increased ADP-ribosylatable protein, but only back to initial levels prior to PMA. In contrast prostaglandin D2 plus theophylline (which increase cyclic AMP) did not increase ADP ribosylation, but could completely block the fall of the toxin substrate caused by thrombin. These results indicate that activation of thrombin receptors promotes the dissociation of G-protein oligomers to release free alpha-subunits, and this effect can be modulated by protein kinase C and cyclic AMP-dependent protein kinase. The possible relationships of these findings to the regulation of stimulus-response coupling in platelets is discussed.
用凝血酶刺激完整血小板，通过测量百日咳毒素在分离膜中对40 - 41 kDa蛋白的ADP核糖基化来评估GTP结合蛋白（G蛋白）寡聚体的量。毒素底物在10 - 60秒内下降了57 - 62%，但随后在5分钟内恢复到正常水平。用水蛭素从受体上去除凝血酶可大大增强恢复。佛波酯肉豆蔻酸酯增加了ADP核糖基化蛋白，但仅回到PMA处理前的初始水平。相比之下，前列腺素D2加茶碱（可增加环磷酸腺苷）并未增加ADP核糖基化，但可完全阻断凝血酶引起的毒素底物下降。这些结果表明，凝血酶受体的激活促进了G蛋白寡聚体的解离以释放游离的α亚基，并且这种效应可被蛋白激酶C和环磷酸腺苷依赖性蛋白激酶调节。本文讨论了这些发现与血小板中刺激 - 反应偶联调节的可能关系。
