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，无法正常泵血，是一种常见疾病（约1：2500），年死亡率超过10000例。这些统计数据强调了开发旨在了解、预防、阻止或逆转进行性心功能不全的新治疗策略的重要性。然而，迄今为止，IDC的原因尚不清楚，并且在IDC中异常调节的分子信号传导机制在很大程度上是未知的。我们的建议将确定蛋白酪氨酸磷酸酶Shp 2是否直接参与介导IDC发病机制的小GTdR RhoA的异常调节。我们最近发表的工作表明，来自心肌细胞特异性缺失Shp 2的小鼠的心脏，Shp 2是大多数（如果不是全部）受体酪氨酸激酶（RTK）信号通路中的关键正调节因子，会发展为严重的扩张型心肌病（DCM）。Shp 2的这种丢失也揭示了RhoA信号通路的过度激活，暗示了Shp 2和心脏中RhoA信号通路之间的一种新的但未定义的联系。我们假设通过Shp 2抑制RhoA活性是心脏保护性的，因此，在生物化学上是预防IDC和心力衰竭所必需的。RhoA是一种小GTP结合蛋白，参与重要的细胞功能，包括细胞增殖、迁移和细胞骨架重组。最近的翻译工作已经证明了RhoA在心血管疾病中的重要作用，包括高血压和动脉粥样硬化;然而，在这里，潜在的机制也不清楚。在这个提议中，我们将阐明RhoA受Shp 2调控的机制。该提案解决了RhoA在心肌细胞疾病中的功能方面的几个有趣和关键问题。使用一组综合的生物化学、细胞生物学、蛋白质组学和遗传学方法，我们计划（1）确定成年心肌中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挽救体内Shp 2缺失小鼠的功能性心脏缺陷，以及（3）利用蛋白质组学以及体外和离体生物化学方法来检查RhoA的Shp 2调节影响心肌中RTK信号传导的机制。该提案的结果将阐明成年心肌中RhoA活性调节的机制，揭示Shp 2调节RhoA活性可能具有心脏保护作用的方式，并有助于产生用于治疗IDC患者心力衰竭的新型分子基础药理学靶点。

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.