Novel pathways modulating Raf-mediated cardiac hypertrophy

描述（由申请人提供）：心脏肥厚和进展为明显的心力衰竭与显著的发病率和死亡率相关。然而，心血管疾病的哺乳动物模型对心脏生理学和信号通路的研究非常有帮助；这些模型不容易适应大规模的基因筛选。因此，利用果蝇作为模型来识别引起或修饰心肌病的新基因的策略被开发出来，以规避与哺乳动物心血管疾病模型相关的一些复杂性。表皮生长因子受体（EGFR）是维持成年果蝇正常发育后心脏功能所必需的。此外，EGFR的激活和随后的小GTPase Ras、激酶Raf和MEK1的信号会导致果蝇和哺乳动物的心脏肥大。通过Hippo激酶发出的信号改变了共转录激活因子yorkie的活性，并在果蝇中产生类似于EGFR/Ras/Raf途径的心脏肥大。长期目标是利用果蝇遗传学作为发现平台，了解调节心脏肥厚和扩张型心肌病发生和发展的分子信号，并将这些发现转化为人类。本应用程序的总体目标是检查Raf-MEK1途径和yorkie在心肌肥厚中的激活。核心假设是Raf-MEK1和hippop - yap1通路之间的串扰驱动心肌细胞决定肥厚或增生。以下具体目标将被检验以检验中心假设：(1)确定raf - mek1介导的心脏肥厚是否通过果蝇Hippo- yorkie通路的调节发生，并确定yorkie下游的信号通路；(2)确定哺乳动物YAP1中驱动心肌细胞肥大或增殖的特定模块结构域；(3)确定在tac诱导的压力过载后，降低YAP-1是否能改变RafL613V/+敲入小鼠或野生型小鼠心脏肥大或心力衰竭的严重程度。这项研究的创新之处在于，它利用果蝇来快速识别两种进化上保守的信号通路中的新分子，并将这些发现转化为哺乳动物。该提案有望确定先前未知的修饰raf依赖性心脏肥厚的成分，并导致更好地理解驱动人类病理性肥厚的途径。

DESCRIPTION (provided by applicant): Cardiac hypertrophy and progression to overt heart failure is associated with significant morbidity and mortality. Mammalian models of cardiovascular disease are tremendously helpful to study cardiac physiology and signaling pathways, however; these models are not readily amenable to large genetic screens. Therefore, strategies using Drosophila as model to identify new genes that cause or modify cardiomyopathies were developed to circumvent some of the complexities associated with mammalian models of cardiovascular disease. The epidermal growth factor receptor (EGFR) is necessary to maintain normal post- developmental cardiac function in adult Drosophila. Moreover, the activation of EGFR and subsequent signals to the small GTPase, Ras, and the kinases, Raf and MEK1, cause cardiac hypertrophy in flies and mammals. Signaling through the kinase, Hippo, alters the activity of the co-transcriptional activator, yorkie, and also produces cardiac hypertrophy similar to the EGFR/Ras/Raf pathway in flies. The long-term goal is understand the molecular signals that modulate the development and progression of cardiac hypertrophy and dilated cardiomyopathy using Drosophila genetics as a discovery platform and translate the findings to humans. The overall objective for this application is to examine the Raf-MEK1 pathway and the activation of yorkie in cardiac hypertrophy. The central hypothesis is that crosstalk between the Raf-MEK1 and Hippo-YAP1 pathways drives cardiomyocyte decisions towards hypertrophy or hyperplasia. The following Specific Aims will be examined to test the central hypothesis: (1) Determine whether Raf-MEK1-mediated cardiac hypertrophy occurs via regulation of the Hippo- yorkie pathway in flies and identify signaling pathways that function downstream of yorkie.; (2) Identify the specific modular domains in mammalian YAP1 that drive cardiomyocyte hypertrophy or proliferation; and (3) Determine whether a reduction in YAP-1 modifies the severity of cardiac hypertrophy or heart failure in RafL613V/+ knock-in mice or wild-type mice after TAC-induced pressure overload. This proposal is innovative in its use of Drosophila to rapidly identify novel molecules in two evolutionarily conserved signaling pathways and translate these findings to mammals. The proposal is expected to identify previously unknown components that modify Raf-dependent cardiac hypertrophy and lead to better understanding of pathways that drive pathologic hypertrophy in humans.