Regulation and function of cGMP dependent protein kinase in cardiac hypertrophy

描述（由申请人提供）：心脏肥大性重塑是心脏病发病率和死亡率的重要组成部分。环鸟苷酸（cGMP）是一种细胞内第二信使，控制多种细胞的生理功能。越来越多的证据表明，一氧化氮或利钠肽促进cGMP合成对心肌肥厚的发展具有负性调节作用。我们最近发现用磷酸二酯酶5A（PDE 5A）抑制剂阻断cGMP降解具有有效的抗肥大和抗重塑作用。cGMP的一个主要下游介质是cGMP依赖性蛋白激酶（cGK）。目前尚不清楚cGMP及其下游cGK如何调节细胞内信号网络，从而对心脏产生这种生理影响。PDE 5A抑制剂目前广泛用于治疗勃起功能障碍和肺动脉高压。我们和其他人的报告支持PDE 5A抑制剂增强cGMP的心脏益处，这引起了人们对这些药物治疗人类心脏病的极大兴趣。为了阐明这种信号传导的潜在机制，现在NIH预计将在心力衰竭患者中启动PDE 5A抑制剂的临床试验。我们的初步数据表明，cGMP激活的CGKI 1（CGKI 1）靶向两种不同的分子，对应激或患病的心脏发挥有益的作用，这取决于其在心脏重塑的不同阶段的细胞内位置。cGKI 1通过在肥大发展的早期阶段激活其抑制性蛋白（称为G蛋白偶联信号传导调节因子2（RGS 2））来减弱Gq信号传导，而在晚期阶段（衰竭），它上调PGC-1 - 1（过氧化物酶体增殖物激活受体3共激活因子1-1），这是一种可能在细胞核中线粒体生物发生和功能的主要调节因子。本提案中的研究旨在通过利用RGS 2缺陷动物（常规和诱导型条件性）和携带突变型cGKI 1的动物（其中关键蛋白质-蛋白质相互作用位点（亮氨酸拉链基序）被破坏），在两个目标中提供有关该调节机制的关键信息。第一个目的是研究GKI 1在早期肥大发展阶段的心脏保护机制。第二个目标将研究cGKI 1调节PGC-11的作用和机制，以及其对心力衰竭晚期线粒体生物发生/功能的影响。这些研究的成功完成将大大扩展我们对cGMP信号在患病心脏中作用的理解，并为测试cGMP信号增强药物（如PDE 5A抑制剂）治疗心脏病的临床试验提供信息。公共卫生相关性：世界上近10%的人口患有心脏肥大，这增加了他们患心脏病和猝死的风险。我们发现，心脏肥大/重塑是通过西地那非（万艾可），目前广泛用于治疗勃起功能障碍的药物，增强内在的cGMP途径得到改善。该项目将阐明心脏中增强cGMP信号通路的这种有益影响的潜在机制，重点关注主要下游分子及其与其他关键调控因子的相互作用。

DESCRIPTION (provided by applicant): Cardiac hypertrophic remodeling underlies a large component of the morbidity and mortality of heart disease. It affects nearly 10% of the world's population given the high prevalence of hypertension and hypertrophy that evolves with it. Cyclic guanosine-3', 5'-monophosphate (cGMP) is an intracellular second messenger which controls diverse cell physiology. Accumulating evidence shows that enhanced synthesis of cGMP by nitric oxide or natriuretic peptides negatively regulate cardiac hypertrophy development. We recently found that blocking cGMP degradation with phospho- diesterase5A (PDE5A) inhibitor have potent anti-hypertrophic and anti-remodeling effects. One major downstream mediator of cGMP is cGMP-dependent protein kinase (cGK). It remains unclear how cGMP and its downstream cGK regulate intra-cellular signaling network, resulting in such physiological impact on the heart. PDE5A inhibitors are currently widely used to treat erectile dysfunction and pulmonary hypertension. Reports from us and others supporting cardiac benefits from cGMP enhancement by PDE5A inhibitors have raised substantial interest for these drugs in treatment of human heart disease. To clarify the underlying mechanism of this signaling takes on more prominence now that the NIH is expected to initiate a clinical trial of PDE5A inhibitor in heart failure patients. Our preliminary data suggest that cGMP- activated cGK type I1 (cGKI1) targets two different molecules to exert beneficial effects over stressed or diseased heart, depending on its intracellular location at different stages of cardiac remodeling. cGKI1 blunts Gq signaling by activating its inhibitory protein named regulator of G-protein coupled signaling 2 (RGS2) at the sarcolemmal membrane in the early phase of hypertrophy development, whereas in the late phase (failure), it up-regulates PGC-11 (peroxisome proliferators-activated receptor 3 coactivator 1-1), a master regulator of mitochondrial biogenesis and function possibly in the nucleus. The research in this proposal aims to provide critical information on the mechanisms of this regulation in two aims by utilizing animals deficient in RGS2 (conventional and inducible conditional) and animals harboring mutant cGKI1 in which critical protein- protein interaction site (leucine zipper motif) is disrupted. The first aim will examine the cardio- protective mechanism of GKI1 in the early hypertrophy development phase. The second aim will examine the role and the mechanism of PGC-11 regulation by cGKI1, and its impact on mitochondrial biogenesis/ function in the late phase of cardiac failure. The successful completion of these studies will greatly expand our understanding of the role for cGMP signaling in diseased hearts, and inform clinical trials testing cGMP signaling-enhancing drugs such as PDE5A inhibitors for treating heart disease. PUBLIC HEALTH RELEVANCE: Nearly 10% of the world's population develops cardiac hypertrophy which increases their risk of suffering from heart disease, and sudden death. We discovered that cardiac hypertrophy/ remodeling is ameliorated by enhancing intrinsic cGMP pathway with sildenafil (Viagra), the drug currently widely used for treating erectile dysfunction. This project will clarify the underlying mechanisms for this beneficial impact from enhanced cGMP signaling pathway in the heart, focusing on a major downstream molecule and its interaction with other key regulators.