The role of protease activated receptors on platelets

项目摘要/摘要 静脉血栓形成(VT)及其主要并发症肺栓塞(PE)通常被归类为 称为静脉血栓栓塞症(VTE)。VTE是一个主要的健康问题，每个人都有近60万人受到影响 年。VTE的历史驱动因素是血瘀证、内皮功能障碍和高凝状态(Virchow‘s 三合会)。现在人们认识到，血小板和中性粒细胞具有关键的启动作用。分子机制 只是被揭开了。鉴于高凝状态是一个危险因素，而且凝血酶激活的蛋白酶被激活 受体4(PAR4)促进促凝血血小板、磷脂酰丝氨酸(PS)暴露及随后的 凝血酶的产生，我们认为PAR4是VTE的重要贡献者。这样做的长期目标是 研究计划是在分子水平上揭示PAR4激活的机制并对其进行测试 体内机制，以告知疾病过程和潜在的药物开发。这其中的科学前提是 建议是基于我们的初步数据显示，PAR4的胞外环3(ECL3)与 PAR4激活过程中的配体结合位点(LBS)。此外，ECL3或LBS中的任何一个突变都会破坏PAR4 发出相同程度的信号。这表明ECL3在PAR4激活中起着至关重要的作用。总体目标 这项建议的目的是：1)确定PAR4如何在静脉血栓形成的启动和传播中起作用 使用小鼠模型，2)使用PAR4拮抗剂治疗VT进行概念验证研究，3)翻译我们的 关于体内PAR4激活机制对PAR4功能的最新结构见解。我们将通过以下方式做到这一点 人类血小板中的PAR4变种和新的小鼠模型的优势。我们的总体假设是 来自血小板上PAR4的持续信号是VTE和低反应性PAR4信号减少的驱动因素 变异体或药物抑制剂将导致对VTE的保护。我们的创新方法将需要 利用一种新的小鼠模型重建ECL3的多态，并将使我们能够确定 该基因多态如何影响血小板功能和血栓形成的机制。该计划的完成 拟议的研究将实现两个主要进展。1)我们将第一个具体研究 PAR4在静脉血栓形成中的作用2)我们将继续推动我们对PAR激活机制的基本理解 通过测试我们在体内结构研究中的观察结果，以确定这些机制如何在 生理和病理生理学背景。

PROJECT SUMMARY/ABSTRACT Venous thrombosis (VT) and its major complication, pulmonary embolism (PE), are often grouped together and called venous thromboembolism (VTE). VTE is a major health problem that affect nearly 600,000 people each year. The historical drivers of VTE are blood stasis, endothelial dysfunction, and hypercoagulation (Virchow’s triad). It is now recognized that platelets and neutrophils have a critical initiating role. The molecular mechanisms are only being uncovered. Given that hypercoagulation is a risk factor and thrombin activated protease activated receptor 4 (PAR4) promotes procoagulant platelets, phosphatidyl serine (PS) exposure and subsequent thrombin generation, we propose that PAR4 is an important contributor to VTE. The long-term goals of this research program are to uncover the mechanisms of PAR4 activation at the molecular level and test these mechanism in vivo to inform disease processes and potential drug development. The scientific premise of this proposal is based our preliminary data showing that extracellular loop 3 (ECL3) of PAR4 coordinates with the ligand binding site (LBS) during PAR4 activation. Further, mutations in either ECL3 or the LBS disrupt PAR4 signaling to the same degree. This points to an essential role for ECL3 in PAR4 activation. The overall objective of this proposal is to 1) to determine how PAR4 contributes to the initiation and propagation of venous thrombosis using mouse models, 2) conduct proof-of-concept studies using PAR4 antagonist to treat VT, 3) to translate our recent structural insights on the PAR4 activation mechanism to PAR4 function in vivo. We will do this by taking advantage a PAR4 variant in human platelets and a new mouse model. Our overall hypothesis is that the sustained signaling from PAR4 on platelets is a driver of VTE and reduced PAR4 signaling from hypo-reactive variants or pharmacological inhibitors will lead to protection from VTE. Our innovative approach will take advantage of a new mouse model that recreates a polymorphism in ECL3 and will allow us to determine the mechanism of how this polymorphism contributes to platelet function and thrombosis. The completion of the proposed studies will accomplish two major advances. 1) we will be the first to specifically examine the role of PAR4 in venous thrombosis. 2) we will continue to push our basic understanding of PAR activation mechanisms by testing the observations from our structural studies in vivo to determine how these mechanisms operate in physiological and pathophysiological contexts.