Regulation and function of cGMP dependent protein kinase in cardiac hypertrophy

描述（由申请人提供）：心脏肥厚重塑是心脏病发病率和死亡率的重要组成部分。由于高血压和肥胖的高患病率，它影响了世界上近10%的人口。环鸟苷-3′，5′-单磷酸（cGMP）是细胞内的第二信使，控制着多种细胞生理。越来越多的证据表明，一氧化氮或利钠肽增强cGMP的合成对心肌肥厚的发展有负性调节。我们最近发现用磷酸二酯酶5a （PDE5A）抑制剂阻断cGMP降解具有有效的抗肥厚和抗重塑作用。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。PDE5A抑制剂目前广泛用于治疗勃起功能障碍和肺动脉高压。我们和其他支持PDE5A抑制剂增强cGMP对心脏有益的报道，引起了人们对这些药物治疗人类心脏病的极大兴趣。为了阐明这一信号传导的潜在机制，NIH预计将在心力衰竭患者中开展PDE5A抑制剂的临床试验。我们的初步数据表明，cGMP激活的cGKI1型（cGKI1）针对两种不同的分子对受压或患病心脏发挥有益作用，这取决于其在心脏重塑不同阶段的细胞内位置。在肥大发育早期，cGKI1通过激活肌层膜上的g蛋白偶联信号2 （regulatory of G-protein coupled signaling 2, RGS2）抑制Gq信号，而在肥大发育晚期（失败），cGKI1上调PGC-11（过氧化物酶体增殖物活化受体3共激活因子1-1），PGC-11是线粒体生物发生的主要调节因子，可能在细胞核中起作用。本研究旨在利用RGS2缺陷动物（常规和诱导条件）和含有关键蛋白-蛋白相互作用位点（亮氨酸拉链基序）被破坏的突变体cGKI1的动物，在两个目标上提供这种调节机制的关键信息。第一个目的是研究GKI1在早期肥厚发育阶段的心脏保护机制。第二个目的是研究cGKI1调控PGC-11的作用和机制，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信号在病变心脏中的作用的认识，并为临床试验检测cGMP信号增强药物（如PDE5A抑制剂）治疗心脏病提供信息。

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.