Role of Von Willebrand Factor in Platelet Thrombosis Formation

在本应用中，我们建议继续努力，旨在阐明VWF的结构和功能，重点关注四个目标。在目标1中，我们将测试VWFA1结构域（VWFA1）中的结构元素是否可以不同地调节特定的粘合性能。初步数据表明，与可溶性VWF结合介导血小板聚集相比，糖蛋白（GP） Iba与固定在表面的VWFA1相互作用导致血小板粘附可能通过不同的机制发生。我们的目标是确定特定VWF活动启动和调节的独特结构要素，并建立它们在血管损伤模型中的功能相关性。在目的2中，我们打算确定a-凝血酶是否可以作为VWF粘附性能的生理调节剂。我们假设VWFA1和a-凝血酶在结合到相同的GPIba受体时建立了分子间接触，这可能独立于剪切应力影响VWFA1-GPIba键的稳定性。我们建议鉴定支持与GPIba结合的a-凝血酶相互作用的VWFA1残基，从而确定血栓形成过程中VWF功能调节的新机制。在目标3中，我们建议评估在人群中发现的特定IgG是否是VWF活性的调节剂。我们已经在人和小鼠血液中发现了一种特异性的IgG，可以选择性地与VWFA1结合，并获得了初步证据，表明该IgG可能在血栓形成中起作用。我们的目标是表征特异性IgG的结构，确定与VWFA1相互作用的模式，并获得其生理病理意义的确切体内证据。在目标4中，我们将定义导致血小板活化的胶原结合VWF的信号功能。我们发现在流动条件下血小板粘附到固定的VWFA1或胶原蛋白后，胞浆内ca2 ++信号明显增强，当血小板与胶原结合的VWF相互作用时，ca2 ++信号增强。我们建议详细分析胶原- vwf复合物支持的血小板活化机制以及水动力对该过程的影响。这项研究的结果将提高我们影响动脉粥样硬化血栓中血小板的疾病过程的能力。

In this application we propose to continue efforts aimed at elucidating von Willebrand factor (VWF) structure and function focusing on four aims. In aim 1 we will test whether structural elements in the VWF A1 domain (VWFA1) can differentially regulate specific adhesive properties. Preliminary data indicate that the interaction of glycoprotein (GP) Iba with VWFA1 immobilized onto a surface, leading to platelet adhesion, may occur through different mechanisms as compared to binding of soluble VWF mediating platelet aggregation. Our goal is to define the distinctive structural elements underlying the initiation and regulation of specific VWF activities and establish their functional relevance in models of vascular injury. In aim 2 we intend to ascertain whether a-thrombin can act as a physiologic modulator of VWF adhesive properties. We hypothesize that VWFA1 and a-thrombin establish inter-molecular contacts when bound to the same GPIba receptor, and this may influence the stability of the VWFA1-GPIba bond independently of shear stress. We propose to identify the VWFA1 residues that support the interaction with a-thrombin bound to GPIba, thus defining a novel mechanism for the regulation of VWF function during thrombogenesis. In aim 3 we propose to evaluate whether a specific IgG found in the human population is a modulator of VWF activity. We have identified in human and mouse blood a specific IgG that binds selectively to VWFA1, and obtained preliminary evidence that this IgG may play a role in thrombus formation. Our goal is to characterize the structure of the specific IgG, define the mode of interaction with VWFA1 and obtain definitive in vivo evidence for its physiopathological significance. In aim 4 we will define the signaling function of collagen-bound VWF leading to platelet activation. We have characterized distinct intracytoplasmic Ca++ signals that follow platelet adhesion to immobilized VWFA1 or collagen under flow conditions, and found that they are enhanced when platelets interact with collagen-bound VWF. We propose to dissect the mechanisms of platelet activation supported by the collagen-VWF complex and the effects of hydrodynamic force on the process. The results of this research will improve our ability to influence disease processes that involve platelets in atherothrombosis.