PHOSPHOINOSITIDE METABOLISM AND PLATELET SECRETION

储存的颗粒成分的分泌，称为释放反应，是一种 血小板功能的中心事件。该反应发生在对 在适当的条件下，各种刺激和引导形成 血小板聚集物。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， 当受到挑战时，显示出磷脂酰肌醇(PI)代谢的显著变化 使用适当的激动剂，如凝血酶。PI在社会变革中的作用 分泌过程尚未阐明。然而，PI中的扰动 血小板中的新陈代谢是有保证的。PI代谢缺陷可能是基础 人类止血和血栓形成中的某些异常。 为了剖析PI代谢的各个方面，我们建议研究 调节血小板PI合成和周转的因素，特别是那些 控制PI专一性磷脂酶C(PI-PLC)存在的因素 2)调节分支点酶，这些分支点酶 进而控制PI的合成。关于第一个目标，我们将 进一步纯化PI-PLC，检测钙调素、钙离子、凝血酶和 CAMP依赖于这种酶的活性。甘油二酯的命运，我们有 被观察到对分泌刺激的反应从PI迅速产生，将 也被调查。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 以及PI-PLC或PLA对前列腺素的贡献程度 制作。我们还将分析在外部的PI的数量 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 组件。为配合这项工作，我们计划研究 分泌缺陷的血小板的磷脂酰肌醇代谢 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.