PHOSPHOINOSITIDE METABOLISM AND PLATELET SECRETION

被称为释放反应的储存颗粒成分的分泌是一种 血小板功能的中心事件。 该反应是响应于 各种刺激和导致，在适当的条件下，形成 血小板聚集体。 因此，血小板的分泌有助于 止血的主要方法。 血小板，像许多其他分泌细胞一样， 当受到攻击时， 与适当的激动剂，如凝血酶。 PI在 分泌过程尚未阐明。 然而，PI中的扰动 血小板中的代谢是必要的。 PI代谢缺陷可能是 人类止血和血栓形成的某些异常。 为了剖析PI代谢的各个方面，我们建议检查 调节血小板PI合成和周转的因素，特别是那些 1）控制PI特异性磷脂酶C（PI-PLC）的因素，其存在 已经被这个实验室报道，2）调节分支点酶， 进而控制PI合成。 关于第一个目标，我们将 进一步纯化PI-PLC，并检测钙调素、Ca+2、凝血酶和 cAMP对这种酶的活性的影响。 甘油二酯的命运， 观察到PI响应分泌刺激而快速产生， 也要调查。 在相关研究中，我们打算通过 磷脂酶A（PLA）抑制剂的使用，PI是否也被 PLA，以及PI-PLC或PLA对前列腺素的贡献程度 生产 我们还将分析PI的量在外部的 血小板膜，人血小板合成肌醇的程度， 以及PI和血小板膜蛋白之间是否存在关联 成分 在这项工作的同时，我们计划研究 血小板磷酸肌醇代谢显示血小板分泌缺陷， 有公认的功能缺陷的患者。

The secretion of stored granular components, known as the release reaction, is a central event in platelet function. The reaction occurs in response to a variety of stimuli and leads, under appropriate conditions, to the formation of platelet aggregates. Consequently, secretion by platelets contributes in a major way to hemostasis. Platelets, like numerous other secretory cells, display a striking shift in phosphoinositide (PI) metabolism when challenged with appropriate agonists, such as thrombin. The role played by PI in the secretory process has yet to be elucidated. However, perturbations in PI metabolism in platelets is warranted. Defects in PI metabolism may underlie certain abnormalities in human hemostasis and thrombosis. To dissect the various aspects of PI metabolism we propose to examine the factors regulating the synthesis and turnover of platelet PI, particularly those factors which 1) control a PI-specific phospholipase C (PI-PLC), whose existence has been reported by this laboratory, and 2) regulate branch-point enzymes which in turn control PI synthesis. With regard to the first objective, we will purify PI-PLC further and examine the effects of calmodulin, Ca+2, thrombin, and cAMP upon the activity of this enzyme. The fate of diglyceride, which we have observed to be generated rapidly from PI in response to secretory stimuli, will be investigated as well. In related studies, we intend to determine, through the use of phospholipase A (PLA) inhibitors, whether PI is hydrolyzed as well by PLA, and the extent to which PI-PLC or PLA contribute to prostaglandin production. We will also analyze the amount of PI at the exterior of the platelet membrane, the extent of synthesis of myoinositol by human platelets, and whether an association exists between PI and a platelet membrane protein component. In conjunction with this work, we plan to examine the phosphoinositide metabolism of platelets displaying defective secretion from patients with recognized functional defects.