ERK5 and CD36 link oxidative stress to platelet dysfunction and ischemic injury

动脉血栓形成的风险，包括心肌梗死（MI）和中风，在系统性心脏病的情况下增加。 与慢性炎症相关的疾病状态，包括癌症、糖尿病、动脉粥样硬化和肥胖症。 不适当的血小板活化是血栓形成的驱动机制，在这些设置和最近的研究 提示疾病状态下血小板活化机制可能不同于正常健康者 条件剖析这些新的机制是这个多PI提案的中心目标。近期刊发 初步研究表明，众所周知，在疾病发生期间， 状态，包括氧化低密度脂蛋白、晚期糖化蛋白、细胞衍生的微粒，以及 S100 A肽都与特异性血小板受体CD 36相互作用，以启动细胞内信号， 血小板活化和血栓形成。进一步发现血小板表达MAP激酶ERK 5，这是一种已知的 活性氧（ROS）传感器。然后显示血小板ERK 5作为氧化还原开关响应于 缺血条件下的细胞外ROS，促进血小板活化和增强心肌损伤 在心肌梗死期间;发现ERK 5在CD 36下游被激活，以响应oxLDL介导的ROS 一代血小板特异性ERK 5缺失可改善血小板活化和血栓前状态 与高血脂氧化应激有关。因此，我们假设ERK 5作为一个中心“节点”， 病理性血小板活化，响应由CD 36和非CD 38触发的受体介导的细胞内信号， 受体介导的细胞外信号（ROS）通过其信号和蛋白介导的组织缺血， 监管活动。特异性目的1将检验CD 36信号传导产生的特异性ROS 通过激活ERK 5维持血小板处于促活化状态。人类体外和小鼠体内研究将 使用遗传模型、饮食诱导的疾病模型和高度特异性的CD 36配体来识别关键细胞 CD 36介导的ERK 5活化所必需的膜伴侣，以及ROS的下游效应物 和血小板中的ERK 5;并确定ERK 5信号传导如何与血小板的“经典”途径整合， 激活以促进血栓形成。目的2验证ERK 5调节血小板蛋白表达的假说 通过调节血小板蛋白翻译和/或蛋白泛素化。体外和体内模型将用于 确定响应ROS的血小板蛋白表达的变化是否依赖于蛋白质 合成、降解或两者。目的3将确定血小板ERK 5激活的机制， 组织缺血和细胞外活性氧增加组织和器官功能障碍。遗传学和药理学 将使用MI和氧化应激的方法和体内模型。通过了解血小板的机制 ERK 5激活和下游通路这些研究将为“失调”的血小板功能提供见解 在病理条件和缺血环境中，可能导致新的治疗靶点， 了解为什么目前基于健康条件下血小板功能的治疗是不够的。

Risk of arterial thrombosis, including myocardial infarction (MI) and stroke, is increased in the setting of systemic disease states associated with chronic inflammation, including cancer, diabetes, atherosclerosis and obesity. Inappropriate platelet activation is a driving mechanism of thrombosis in these settings and recent studies suggest that mechanisms of platelet activation in diseased states may be different from those in normal healthy conditions. Dissecting these novel mechanisms is the central goal of this multi-PI proposal. Recent published and preliminary studies showed that endogenous danger signals well known to be generated during diseased states, including oxidized low density lipoprotein, advanced glycated proteins, cell-derived microparticles, and S100A peptides all interact with a specific platelet receptor, CD36, to initiate intracellular signals that promote platelet activation and thrombosis. Furthemore platelets were found to express the MAP kinase ERK5, a known sensor of reactive oxygen species (ROS). Platelet ERK5 was then shown to act as a redox switch responsive to extracellular ROS under ischemic conditions, promoting platelet activation and enhancing myocardial damage during MI; and ERK5 was found to be activated downstream of CD36 in response to oxLDL-mediated ROS generation. Platelet specific deletion of ERK5 ameliorated platelet activation and the pro-thrombotic state associated with hyperlipidemic oxidant stress. We thus hypothesize that ERK5 serves as a central “node” in pathologic platelet activation, responding to receptor-mediated intracellular signals triggered by CD36 and non- receptor mediated extracellular signals (ROS) mediated by tissue ischemia, through both its signaling and protein regulation activities. Specific aim 1 will test the hypothesis that specific ROS generated by CD36 signaling maintains platelets in a pro-activated state via activation of ERK5. Human In vitro and mouse in vivo studies will use genetic models, diet-induced disease models, and highly specific CD36 ligands to identify critical cell membrane partners necessary for CD36-mediated ERK5 activation, as well as downstream effectors of ROS and ERK5 in platelets; and to determine how ERK5 signaling integrates with “classic” pathways of platelet activation to promote thrombosis. Aim 2 will test the hypothesis that ERK5 regulates platelet protein expression by modulating platelet protein translation and/or protein ubiquitination. In vitro and in vivo models will be used to determine whether changes in platelet protein expression in response to ROS are dependent on protein synthesis, degradation, or both. Aim 3 will determine mechanisms by which platelet ERK5 activation in the setting of tissue ischemia and extracellular ROS increases tissue and organ dysfunction. Genetic and pharmacologic approaches and in vivo models of MI and oxidant stress will be used. By understanding mechanisms of platelet ERK5 activation and downstream pathways these studies will provide insights into `dysregulated' platelet function in pathologic conditions and ischemic environments that may lead to new therapeutic targets and better understanding of why current therapies based on platelet function in healthy conditions are inadequate.