THE ROLE OF MEMBRANE PROTEINS IN PLATELET FUNCTION

动脉血栓形成是疾病和死亡的主要原因。 部位的 在血管疾病中，血小板聚集并形成血管疾病的主要成分 这些血栓 血栓外围的血小板可能破裂 然后再回到循环系统中，这种可逆的活化反应 可能会导致细胞膜发生重大变化 这项建议的目的是 检查血小板可能引起的四种特异性膜变化， 活化：肌动蛋白聚合导致膜可变形性降低， 这种不易变形的膜的碎片导致 膜微粒，内源性分泌蛋白的表面结合， 和膜结合免疫球蛋白的变化。 我们的实验将测量 这些变化（a）在凝血酶激活后和（B）在 自发的全血凝结，我们将在体外将这些 结果与研究的血小板和血浆从病人 血栓性疾病 将测量血小板肌动蛋白的聚合 通过脱氧核糖核酸酶抑制。 血小板膜微粒 将使用单克隆抗体通过放射免疫测定在血浆中定量 抗内在膜糖蛋白的抗体。 的结合位点 膜表面的内源性分泌蛋白及其在 将定义血小板粘附。 激活对 血小板IgG浓度及其亚细胞分布 研究，特别是研究唾液酸损失的可能性， 在血小板活化过程中可能导致IgG与去唾液酸糖蛋白结合 Ib是天然存在的自体免疫的“衰老抗原”， 抗体的 可能导致多次可逆的血小板接触相互作用 在聚合肌动蛋白的增加中， 材料，和免疫球蛋白的积累。 这可能发生在 正常循环作为内皮支持的功能， 衰老血小板的结构和功能变化。 这些循环 可逆的相互作用可能会加速血栓形成患者， 疾病，以及测量循环血小板的这些膜变化 应允许识别风险增加的患者， 血栓形成

Arterial thrombosis is a major cause of illness and death. At the site of the vessel disease, blood platelets aggregate and form a major component of these thrombi. The platelets on the periphery of the thrombus may break away and return to the circulation, and this reversible activation reaction could result in significant membrane changes. The aim of this proposal is to examine four specific membrane changes which may result from platelet activation: actin polymerization causing decreased membrane deformability, fragmentation of this less deformable membrane to cause the loss of membrane microparticles, surface binding of endogenous secreted proteins, and changes of membrane-bound immunoglobulin. Our experiments will measure these changes (a) following activation by thrombin and (b) during the spontaneous clotting of whole blood, and we will correlate these in vitro results with studies of the platelets and plasma from patients with thrombotic disease. The polymerization of platelet actin will be measured by dexoyribonuclease inhibition. Microparticles of the platelet membrane will be quantified in plasma by a radioimmunoassay using a monoclonal antibody to an intrinsic membrane glycoprotein. The binding sites of endogenous secreted proteins on the membrane surface and their role in platelet adhesion will be defined. The effect of activation on the platelet IgG concentration and its subcellular distribution will be studied, specifically investigating the possibility that sialic acid loss during platelet activation may lead to IgG binding, with asialoglycoprotein Ib being a "senescent antigen" for naturally occurring autologous antibodies. Multiple reversible platelet contact interactions may result in an increase of polymerized actin, a progressive loss of membrane material, and the accumulation of immunoglobulin. This could occur in the normal circulation as a function of endothelial support causing the structural and functional changes of senescent platelets. These cycles of reversible interactions could be accelerated in patients with thrombotic disease, and measurement of these membrane changes of circulating platelets should allow the recognition of patients who have an increased risk for thrombosis.