RHOA KINASES IN CARDIAC HYPERTROPHY

由血流动力学超负荷和/或结构性心脏病引发的心脏肥大的机制仍不完全清楚。阐明心肌细胞如何将机械应力相关信号从膜转录到核转录，将有助于我们对心肌肥厚临床问题的理解。RhoA是一种小分子量的GTP结合蛋白，作为一种分子开关，控制各种细胞功能，是一种潜在的肥大信号介导剂。我们假设RhoA作为一个关键的传感器的功能，在诱导级联，链接拉伸依赖性信号传导的诱导心脏基因表达在体内。此外，我们建议，丝氨酸/苏氨酸激酶P160 rock，最近被确定为Rho 1A的下游效应器，是主要的信号分子介导的RhoA的肥大效应。我们的初步研究结果表明，RhoA和p160 ROCK，连同β 1整合素及其粘附依赖的行动，作为一种新的信号通路，在激活心肌细胞中的心脏富集血清反应因子（SRF）依赖的基因，如骨骼α-肌动蛋白，通过p160 ROCK依赖磷酸化的SRF。我们还观察到，p160 ROCK mRNA转录的水平显着诱导在超载的心脏，这表明该分子在心肌肥厚的发展中的重要作用。我们的研究结果表明，磷酸化SRF的160 ROCK可能是一个关键步骤，激活胎儿心脏基因的表达在心肌肥厚。本研究的具体目的是：1）确定RhoA、p160 ROCK和SRF在牵张诱导的心肌细胞肥大反应中的作用; 2）确定RhoA信号通路是否通过160 ROCK磷酸化SRF来调节SRF依赖的肥大基因表达; 3）在基因操作的小鼠模型中确定RhoA和p160 ROCK在介导压力超负荷诱导的心脏肥大反应中的作用。总体目标是确定RhoA，β 1整合素，p160 ROCK和SRF是否是一个潜在的重要的新的信号通路，有助于心肌细胞基因表达的重编程在牵张诱导的心脏肥大的主要介质。

The mechanisms directing cardiac hypertrophy, triggered by hemodynamic overload and/or structural heart disease, are still not completely understood. Delineating how cardiac myocytes transduce mechanical stress related signaling from the membrane to nuclear transcription will greatly contribute to our understanding of the clinical problems of cardiac hypertrophy. RhoA, a small molecular weight GTP- binding protein, acts as a molecular switch that controls various cell functions, and is a potential mediator of hypertrophic signals. We hypothesize that RhoA functions as a key transducer in the induction cascade that links stretch dependent signaling to the induction of cardiac gene expression in vivo. In addition, we propose that the Ser/Thr kinase P160rock, recently identified as a downstream effector of Rho1A, is the primary signaling molecule mediating hypertrophic effects of RhoA. Our preliminary results indicate that RhoA and p160ROCK, together with beta1 integrin and its adhesion dependent actions, serve as a novel signal pathway in activating the cardiac enriched serum response factor (SRF) dependent genes in cardiomyocytes, such as skeletal alpha-actin, through the p160ROCK dependent phosphorylation of SRF. We have also observed that the level of p160ROCK mRNA transcripts is markedly induced in the overloaded heart, suggesting an important role for this molecule in the development of cardiac hypertrophy. Our results suggest that phosphorylation of SRF by 160ROCK might be a critical step for the activation of fetal cardiac gene expression during cardiac hypertrophy. The Specific Aims of this proposal are: 1) to determine the role of RhoA, p160ROCK and SRF in mediating hypertrophic responses induced by stretch in cultured cardiomyocytes; 2) to determine if the RhoA signaling pathways regulates SRF-dependent hypertrophic gene expression via phosphorylation of SRF by 160ROCK; 3) to determine the role of RhoA and p160ROCK in mediating cardiac hypertrophic responses induced by pressure overload in genetically manipulated mouse models. The overall objective is to determine if RhoA, beta1 integrin, p160ROCK and SRF are primary mediators of a potentially important novel signal pathway that contributes to reprogramming of cardiomyocyte gene expression in stretch induced cardiac hypertrophy.