HUMAN PLATELET ACTIVATION AND PHOSPHOLIPID METABOLISM

血小板的活化对于止血过程是重要的， 因为血小板由此成为形成的完全参与者 病变导向的聚集体，血管收缩和 促有丝分裂物质和用于产生促凝血剂的表面 蛋白质因素 现在公认的是， 定量的少量磷脂，磷脂酰肌醇（PI）， 磷酸肌醇酶C（PIC）是一种主要的初始事件， 将细胞表面定向激动剂与完整的细胞反应偶联。 另一个激动剂诱导的血小板PI代谢的变化描述 最近发现的是通过β-激酶（PI-3 K）磷酸化PI种类。 这 在有核细胞中，似乎需要有丝分裂反应， 应答 所得到的PI的功能还不清楚， 尤其是在无核血小板中。 由于PI-3 K产品较差， 作为PIC的底物，它们可能直接起作用，而不是作为 信号的前兆。 主要磷脂，如磷脂酰胆碱 （PtdCho），用作血栓烷A2前体的储备， 花生四烯酸（C20：4），其在活化的血小板中通过 磷脂酶A（PLA）。 所有这些变化似乎都是由 G蛋白 在血小板活化过程中，无定形胞浆 前体被分解成有组织的细胞骨架和糖蛋白 改变它们与膜细胞骨架的连接。 我们打算探索 由PIC和PI-3 K催化的PI的代谢变化以及 C20：4的动员与血小板的变化相协调 细胞骨架结构，时间上和功能上。 四个附加 可活化血小板成分：酪氨酸激酶、巯基蛋白酶 将研究钙蛋白酶、G蛋白和整合素GPIIb/IIIa 关于PIC、PI-3 K和PIA法规。 技术监测 血小板PIC和PI-3 K放射性同位素和质量分析联合 薄层色谱法（TLC）和高效液相色谱法是开创性的，并在 在这个实验室里很常见 我们还展示了以下方面的专业知识： 通过TLC和HPLC测量C20：4动员和PLA活化。 这些 技术，部分，将适用于不溶于Triton的细胞骨架， 膜骨架制剂以及免疫沉淀 含磷酸酪氨酸的蛋白质。 两种PI-3 K产品的效果 对凝溶胶蛋白和profilin功能（调节肌动蛋白聚合）的影响将 被衡量。 酪氨酸激酶、G蛋白和钙蛋白酶的激活将 通过免疫印迹技术及其功能进行监测，以及 GPIIb/IIIa的活性将被适当的抑制剂干扰， 激动剂，并与PIC，PI-3 K和PLA活性的改变进行比较。

The activation of the platelet is important for the hemostatic process, since the platelet thereby becomes a full participant in the formation of lesion-directed aggregates, a secretor of vasoconstricting and mitogenic substances, and a surface for the generation of pro-coagulant protein factors. It is now well recognized that the hydrolysis of a quantitatively minor species of phospholipid, phosphoinositide (PI), by phosphoinositidase C (PIC) is one of the major initial events that couples a cell surface-directed agonist to a full cellular response. Another agonist-induced change in platelet PI metabolism described recently is phosphorylation of PI species by a 3-kinase (PI-3K). This reaction, in nucleated cells, appears to be required for mitogenic responses. The function of the resulting PI's is as yet unknown, especially in the anucleate platelet. Since PI-3K products are poor substrates for PIC, they probably function directly, rather than as precursors for signals. Major phospholipid, such as phosphatidylcholine (PtdCho), serves as a reserve for the thromboxane A2 precursor, arachidonic acid (C20:4), which is liberated in activated platelets via phospholipase A (PLA). All of these changes appear to be controlled by G-proteins. In the course of platelet activation, amorphous cytoplasmic precursors polymerize into organized cytoskeleton, and glycoproteins change their linkage to membrane cytoskeleton. We intend to explore how the metabolic changes in PI's catalyzed by PIC and PI-3K and the mobilization of C20:4 are coordinated with alterations in the platelet cytoskeletal apparatus, temporally and functionally. Four additional activatable platelet components: tyrosine kinase, the thiol protease calpain, G-protein(s), and the integrin GPIIb/IIIa, will be investigated with respect to PIC, PI-3K and PIA regulation. Techniques for monitoring platelet PIC and PI-3K by radioisotopic and mass analysis in conjunction with thin layer chromatography (TLC) and HPLC were pioneered, and are in common use in, this lab. We also have demonstrated expertise in measuring C20:4 mobilization and PLA activation by TLC and HPLC. These techniques, in part, will be applied to triton-insoluble cytoskeletal and membrane skeletal preparations as well as to immunoprecipitated phosphotyrosine-containing protein. The effects of two PI-3K products on gelsolin and profilin function (modulating actin polymerization) will be measured. Activation of tyrosine kinase, G-protein, and calpain will be monitored by immunoblotting techniques and their function, as well as that of GPIIb/IIIa, will be perturbed with appropriate inhibitors and agonists and compared with alterations in PIC, PI-3K, and PLA activities.