Molecular Mechanisms of Platelet Activation and Adhesion

人类的血小板质膜含有数百种不同的蛋白质，这些蛋白质控制着至关重要的功能， 包括与细胞外基质的黏附、信号转导、血小板聚集和凝块回缩。中心到 血小板相互黏附和黏附细胞外基质的能力是细胞表面的丰富供应。 黏附分子，包括整合素家族的成员，以不同的激活状态存在。这些细胞 黏附受体反过来将信号传递到细胞内部，并对来自细胞内部的信号做出反应。分子 然而，调节血小板活化和黏附的信号通路的细节仍然不完全。 明白了。因此，这个项目的目标是研究分子机制的四个相互关联的方面。 潜在的血小板活化和黏附。特定目标1试图通过以下方式了解分子机制 哪些抗血小板膜糖蛋白(GP)VI的抗体导致手术切除这一重要的 来自血小板表面的黏附和信号复合体，使血小板对细胞外无反应 基质成分、胶原蛋白，不太可能参与血栓形成。希望这些研究可以 能够合理设计未来治疗心肌梗死和中风的GPVI特异性疗法。 特定目标2建议测试最近提出的一个有吸引力的假说，即体内的特定氨基酸 整合素β3亚单位的膜近端β末端结构域控制着大分子配体如 纤维蛋白原和von Willebrand因子与整合素头部结构域中的配体接触部位。这些研究应该 提供了关于细胞外域内细微的变构变化如何使 整合素从低亲和力状态到高亲和力状态的转变。具体目标3建议探索这一假设 PECAM-1通过隔离蛋白酪氨酸磷酸酶SHP-2作为抑制性受体发挥作用 来自调节Src家族激酶激活的蛋白质。这些研究将为我们提供重要的新线索 PECAM-1，可能还有其他SHP-2结合蛋白，调节细胞功能的机制 激活。最后，具体目标4是一个生成假设的翻译研究目标，它试图确定 PECAM-1在人群中的表达是否存在差异，以及可变PECAM-1的表达是否存在差异 易患动脉血栓形成或出血。这些研究有可能将PECAM-1添加到 越来越多的细胞黏附和信号受体的表达与出血和凝血有关 从而提高我们诊断、治疗和预防临床血栓形成的能力 人类。总而言之，这些研究代表了一系列协调一致的调查，旨在推动我们的 对血小板生理学的了解，并在输血治疗、血小板储存和 治疗血小板功能和免疫紊乱。

The human platelet plasma membrane contains several hundred different proteins that control crucial functions, including adhesion to extracellular matrix, signal transduction, platelet aggregation, and clot retraction. Central to the ability of platelets to adhere to each other and to extracellular matrix is an abundant supply of cell surface adhesion molecules, including members of the integrin family, that exist in varying states of activation. These cell adhesion receptors, in turn, transmit signals into, and respond to signals from, the cell interior. The molecular details of the signaling pathways that regulate platelet activation and adhesion, however, remain incompletely understood. The goal of this project, therefore, is to examine four interrelated aspects of the molecular mechanisms underlying platelet activation and adhesion. Specific Aim 1 seeks to understand the molecular mechanism by which antibodies to platelet membrane glycoprotein (GP) VI result in the surgical removal of this important adhesion and signaling complex from the platelet surface, rendering platelets unresponsive to the extracellular matrix component, collagen, and less likely to participate in thrombus formation. It is hoped that these studies may enable rational design of future GPVI-specific therapeutics for the treatment of myocardial infarction and stroke. Specific Aim 2 proposes to test a recently-proposed and attractive hypothesis that specific amino acids within the membrane proximal beta-terminal domain of the integrin beta3 subunit control access of macromolecular ligands like fibrinogen and von Willebrand factor to ligand contact sites within the integrin head domain. These studies should provide important insights into how subtle allosteric changes within the extracellular domain might enable transformation of integrins from a low- to high-affinity state. Specific Aim 3 proposes to explore the hypothesis that PECAM-1 functions as an inhibitory receptor by sequestering the protein-tyrosine phosphatase, SHP-2, away from proteins that regulate the activation of Src family kinases. These studies will shed important new light on the mechanism by which PECAM-1, and perhaps other SHP-2 binding proteins, function to modulate cellular activation. Finally, Specific Aim 4 is a hypothesis-generating, translational research aim that seeks to determine whether PECAM-1 expression varies in the human population, and whether variable PECAM-1 expression might predispose individuals to arterial thrombosis or hemorrhage. These studies have the potential to add PECAM-1 to the growing list of cell adhesion and signaling receptors whose expression is linked to bleeding and clotting disorders in humans, and may thereby improve our ability to diagnose, treat, and prevent clinical thrombosis in humans. Together, these studies represent a coordinated line of investigation designed to advance our understanding of platelet physiology and lead to improvements in transfusion therapy, platelet storage, and management of platelet functional and immunological disorders.