The role of protease activated receptors on platelets

项目总结/摘要 静脉血栓形成（VT）及其主要并发症肺栓塞（PE）通常被归为一类， 静脉血栓栓塞症（VTE）。静脉血栓栓塞是一个主要的健康问题，影响近60万人， 年VTE的历史驱动因素是血瘀、内皮功能障碍和高凝状态（Virchow的 三和弦）。现在认识到血小板和中性粒细胞具有关键的启动作用。的分子机制 只是被发现了。鉴于高凝是一个危险因素，凝血酶激活的蛋白酶激活 受体4（PAR 4）促进促凝血血小板、磷脂酰丝氨酸（PS）暴露和随后的血小板聚集。 凝血酶生成，我们认为PAR 4是VTE的重要贡献者。长期目标是 研究计划是在分子水平上揭示PAR 4激活的机制，并测试这些机制。 在体内的机制，告知疾病的过程和潜在的药物开发。科学的前提是 该提议基于我们的初步数据，该数据显示PAR 4的细胞外环3（ECL 3）与 配体结合位点（LBS）。此外，ECL 3或LBS中的突变破坏PAR 4 在相同的程度上发出信号。这表明ECL 3在PAR 4活化中的重要作用。总体目标 该建议的目的是：1）确定PAR 4如何促进静脉血栓形成的发生和传播 使用小鼠模型，2）使用PAR 4拮抗剂治疗VT进行概念验证研究，3）将我们的 PAR 4激活机制的最新结构见解PAR 4在体内的功能。我们将通过采取 在人血小板中的PAR 4变体和新的小鼠模型中的优势。我们的总体假设是 血小板上来自PAR 4的持续信号传导是VTE的驱动因素，而来自低反应性血小板的减少的PAR 4信号传导是VTE的驱动因素。 变体或药理学抑制剂将导致对VTE的保护。我们的创新方法将 这是一个新的小鼠模型的优势，它重建了ECL 3的多态性，并使我们能够确定 这种多态性如何有助于血小板功能和血栓形成的机制。的完成 拟议的研究将取得两项重大进展。1)我们将首先具体研究 静脉血栓形成中的PAR 4。2)我们将继续推进我们对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，以确定这些机制在体内是如何运作的。 生理和病理生理背景。

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.