The Role of RhoA in the Molecular Pathogenesis of Heart Disease

描述（由申请人提供）：特发性扩张型心肌病（IDC），导致心脏增大，不能正常泵血，是一种常见病（约1:2500），每年死亡人数超过10000人。这些统计数据强调了开发新的治疗策略的重要性，旨在了解、预防、阻止或逆转进行性心功能障碍。然而，迄今为止，IDC的病因尚不清楚，IDC中异常调节的分子信号机制在很大程度上是未知的。我们的研究将确定酪氨酸磷酸酶Shp2对小GTPase RhoA的异常调节是否直接参与了IDC的发病机制。我们最近发表的研究表明，心肌细胞特异性缺失Shp2的小鼠心脏会发展为严重的扩张型心肌病（DCM）， Shp2是大多数（如果不是全部的话）受体酪氨酸激酶（RTK）信号通路的关键正调节因子。Shp2的缺失也揭示了RhoA信号通路的超激活，暗示了心脏中Shp2和RhoA信号通路之间的一种新的但尚未明确的联系。我们假设，通过Shp2抑制RhoA活性具有心脏保护作用，因此，从生物化学角度来看，这是预防IDC和心力衰竭所必需的。RhoA是一种小的GTP结合蛋白，参与细胞增殖、迁移和细胞骨架重组等重要细胞功能。最近的翻译工作已经证明RhoA在心血管疾病，包括高血压和动脉粥样硬化中的重要作用；然而，在这里，潜在的机制也不清楚。在本提案中，我们将阐明Shp2调控RhoA的机制。这一建议解决了几个关于RhoA在心肌细胞疾病中的功能的有趣和关键问题。采用综合的生化、细胞生物学、蛋白质组学和遗传学方法，我们计划(1)确定成人心肌中RhoA活性丧失的生理意义(2)确定RhoA表达和/或活性丧失是否可以在体内挽救Shp2缺失小鼠的功能性心脏缺陷。(3)利用蛋白质组学和体外生化方法研究Shp2调控RhoA影响心肌RTK信号的机制。本研究的结果将阐明成人心肌中RhoA活性的调节机制，揭示Shp2调节RhoA活性可能具有心脏保护作用的方式，并有助于产生新的、基于分子的药物靶点，用于治疗IDC患者的心力衰竭。

DESCRIPTION (provided by applicant): Idiopathic dilated cardiomyopathy (IDC), resulting in an enlarged heart that does not pump properly, is a common disease (~ 1:2500) associated with an annual mortality rate of greater than 10000 deaths. These statistics underscore the significance for developing new therapeutic strategies aimed at understanding, preventing, arresting or reversing progressive cardiac dysfunction. However, to date, the cause(s) of IDC is (are) unclear and the molecular signaling mechanisms that are aberrantly regulated in IDC are largely unknown. Our proposal will determine whether aberrant regulation of the small GTPase RhoA by the protein tyrosine phosphatase Shp2 is directly involved in mediating IDC pathogenesis. Our recently published work shows that hearts from mice with cardiomyocyte-specific deletion of Shp2, a key positive regulator in most, if not all, receptor tyrosine kinase (RTK) signaling pathways, develop a severe dilated cardiomyopathy (DCM). This loss of Shp2 also revealed a hyper-activation in the RhoA signaling pathway, implicating a novel, yet undefined, connection between Shp2 and the RhoA signaling pathway in the heart. We hypothesize that suppression of RhoA activity, via Shp2, is cardioprotective and, as such, is biochemically required to prevent IDC and heart failure. RhoA is a small GTP binding protein involved in important cellular functions including cell proliferation, migration and cytoskeletal reorganization. Recent translational work has demonstrated a significant role for RhoA in cardiovascular disease, including hypertension and atherosclerosis; however, here too, the underlying mechanisms are unclear. In this proposal, we will elucidate the mechanisms by which RhoA is regulated by Shp2. This proposal addresses several interesting and key questions with regards to the function of RhoA in cardiomyocyte disease. Using a combined, comprehensive set of biochemical, cell biological, proteomic and genetic approaches, we plan to (1) determine the physiological significance of loss of RhoA activity in the adult myocardium (2) determine whether loss of RhoA expression and/or activity can rescue the functional cardiac defects in Shp2 deleted mice in vivo, and (3) utilize proteomic and in vitro and ex vivo biochemical approaches to examine the mechanism by which Shp2 regulation of RhoA affects RTK signaling in the myocardium. Results of this proposal will elucidate the mechanism(s) by which RhoA activity is regulated in the adult myocardium, reveal the manner in which Shp2 regulation of RhoA activity may be cardioprotective, and assist in the generation of novel, molecular-based pharmacological targets for the treatment of heart failure in patients with IDC.