RGS Protein Function in Cardiac Physiology

描述（由申请人提供）：人类心脏肥厚通常与不良预后相关。在培养的大鼠心肌细胞中，配体如苯肾上腺素、内皮素-1、血管紧张素II和前列腺素f2 - α促进肥厚反应。有证据表明，这些配体在培养细胞上的作用类似于人类的心脏肥大。大多数引起培养心肌细胞肥大的激动剂通过异源三聚体G蛋白发出信号。G蛋白信号调节因子（RGS）蛋白是GTPase激活蛋白（gap），它使异源三聚体G蛋白的亚基失活。本研究的主要目的是研究RGS蛋白在心脏肥厚生长调控中的生理作用。核心假设是RGS蛋白决定心肌细胞对细胞外刺激的反应性，RGS基因表达的增加是一种限制g蛋白介导的信号转导的适应性机制。在最初的资助时期，我们证明了RGS蛋白存在于心脏中，RGS3和RGS4基因表达对外部刺激有反应，小鼠心脏特异性的RGS4过表达可阻断压力过载和运动诱导的心脏肥厚，RGS4是体内心脏Gq的GAP。尽管有这些发现，关于RGS蛋白在心脏病中的作用仍然存在许多问题。在该项目的下一阶段，我们建议通过在培养细胞中使用“敲除”策略来研究RGS2、RGS3和RGS4在心肌细胞肥大中的具体作用。其次，我们研究了RGS4在压力过载和运动诱导的心脏肥大中的具体作用，通过使用全身和心脏特异性靶向破坏RGS4基因的小鼠。第三，我们通过使用全身靶向破坏RGS3基因的小鼠，研究RGS3在压力过载和运动诱导的心脏肥厚中的具体作用。这些实验将有助于明确RGS蛋白在心肌肥厚和收缩功能障碍发病机制中的作用，并可能为开发新的治疗药物提供重要信息。

DESCRIPTION (provided by applicant): Cardiac hypertrophy in humans is frequently associated with a poor prognosis. In cultured rat cardiac myocytes, ligands such as phenylephrine, endothelin-1, angiotensin II, and prostaglandin F2alpha promote a hypertrophic response. There is evidence that the action of these ligands on cultured cells mimics cardiac hypertrophy in humans. Most agonists that cause cultured cardiomyocytes to hypertrophy signal via heterotrimeric G proteins. Regulator of G protein signaling (RGS) proteins are GTPase activating proteins (GAPs) that deactivate asubunits of heterotrimeric G proteins. The main aim of this proposal is to investigate the physiologic role of RGS proteins in the regulation of cardiac hypertrophic growth program. The central hypothesis is that RGS proteins determine the responsiveness of cardiac myocytes to extracellular stimuli, and that RGS gene expression is increased as an adaptive mechanism to limit Gprotein- mediated signal transduction. In the original funding period, we demonstrated that RGS proteins are present in heart, that RGS3 and RGS4 gene expression is responsive to external stimuli, that cardiacspecific overexpression of RGS4 in mice blocks pressure overload- and exercise-induced cardiac hypertrophy, and that RGS4 is a GAP for Gq in the in vivo heart. Despite these findings, many questions remain about the role of RGS proteins in heart disease. In the next phase of this project, we propose to investigate the specific role of RGS2, RGS3, and RGS4, in cardiac myocyte hypertrophy by use of a "knock-down" strategy in cultured cells. Second, we investigate the specific role of RGS4 in pressure overload- and exercise-induced cardiac hypertrophy by use of mice with both whole-body and cardiacspecific targeted disruption of this gene. Third, we investigate the specific role of RGS3 in pressure overload- and exercise-induced cardiac hypertrophy by use of mice with whole-body targeted disruption of this gene. These experiments will help define the role of RGS proteins in the pathogenesis of cardiac hypertrophy and contractile dysfunction and may provide important information for the development of novel therapeutic agents.