Compartmental PKA and Pathological Cardiac Hypertrophy

项目摘要/摘要： 病理性心肌肥厚(PCH)是致死性室性心律失常的独立危险因素 心力衰竭。临床上对预防或治疗PCH的更有效疗法的需求尚未得到满足。而PKA 刺激交感神经/β-肾上腺素能系统后的激活对心率的正常调节是必不可少的 和心肌收缩功能，交感/β-肾上腺素能系统/蛋白激酶A的持续激活 高血压等心血管疾病会导致PCH和收缩功能障碍。然而，它仍然 尚不清楚PKA是如何促进PCH的，以及操纵PKA激活是否可以用于治疗或预防PCH。 心脏内源性PKA抑制肽(PKI)对PKA活性具有负性调节作用。我们发现了 首次将pki亚型之一pkiα集中在成年心肌细胞的细胞核中，并 胞质PKA比胞质PKA对刺激不敏感，激活速度较慢。 此外，压力超负荷降低了pkiα的表达，特别是在细胞核中，并降低了它的抑制能力。 PKA.当pkiα在小鼠中被基因消融时，核pkA活性增强，导致令人惊讶的降低。 压力过载后的PCH。另一方面，当仅通过PKA抑制来抑制心肌细胞PKA时 在压力超负荷作用下，α的结构域被钝化。我们培养的心肌细胞研究表明 这种PCH的减少与胞质PKA的抑制有关。因此，我们认为，PKA的本土化 活化在PCH的发生发展中起着至关重要的作用。取决于蜂窝位置(隔间) 在PKA激活中，PKA既可促进压力超负荷所致PCH，也可钝化压力超负荷所致PCH。 基于这些初步研究，我们假设：虽然胞浆PKA的激活是促肥大的， 核蛋白激酶A的激活具有抗肥厚性，内源性蛋白激酶Iα对核蛋白激酶A的激活具有抑制作用。我们 进一步预测，胞质PKA抑制与增强的核PKA将是预防或 治疗PCH。我们将在三个目标上检验这一假说：1)确定基因剂量依赖效应和 心肌细胞特异性蛋白激酶A抑制(PKAi)对心脏结构和功能的影响机制 肥厚性应激反应的重塑。2)确定抑制胞浆PKA的效果(用 细胞溶胶靶向PKAi)对PCH的发展。3)检测pkiα对核内pkA活性的影响 基因敲除或核PKA过表达或核PKA抑制PCH的发生发展。 拟议研究的完成将提供对分隔PKA的作用的新见解 以及pkiα在多氯联苯发展过程中的调控。从这个项目中产生的新知识将有助于 为预防和治疗PCH患者开发新的治疗策略。

Project Summary/Abstract: Pathological cardiac hypertrophy (PCH) is an independent risk factor for lethal ventricular arrhythmias and heart failure. There is an unmet clinical need for more effective therapies to prevent or treat PCH. While PKA activation after sympathetic/β-adrenergic system stimulation is essential for the normal regulation of heart rate and cardiac contractility, persistent activation of sympathetic/β-adrenergic system/protein kinase A (PKA) in cardiovascular diseases such as hypertension leads to PCH and contractile dysfunction. However, it remains unclear how PKA promotes PCH and if manipulating PKA activation can be used to treat or prevent PCH. PKA activity is negatively regulated by endogenous PKA inhibitor peptides (PKI) in the heart. We found for the first time that one of the PKI isoform, PKIα, is concentrated in the nucleus of adult cardiomyocytes and keeps nuclear PKA activation less sensitive to stimulation and activated at a slower rate than cytosolic PKA. Furthermore, pressure overload reduces PKIα expression, especially in the nucleus, and its capability to inhibit PKA. When PKIα is genetically ablated in mice, nuclear PKA activity is enhanced, leading to surprisingly reduced PCH after pressure overload. On the other hand, when myocyte PKA is inhibited by only the PKA inhibition domain of PKIα (PKAi), PCH induced by pressure overload is blunted. Our cultured myocyte study suggest that this PCH reduction is related to cytosolic PKA inhibition. Therefore, we propose that the localization of PKA activation is crucial for its effect on the development of PCH. Depending on the cellular location (compartment) of PKA activation, PKA can either promote or blunt PCH induced by pressure overload. Based on these preliminary studies, we hypothesize that: while cytosolic PKA activation is prohypertrophic, nuclear PKA activation is antihypertrophic; endogenous PKIα exerts inhibition on nuclear PKA activation. We further predict that cytosolic PKA inhibition with enhanced nuclear PKA will be a desired strategy to prevent or treat PCH. We’ll test the hypothesis in three aims: 1) To determine the gene dose-dependent effects and mechanisms of global cardiomyocyte-specific PKA inhibition (PKAi) on cardiac structural and functional remodeling in response to hypertrophic stress. 2) To determine the effects of inhibiting cytosol PKA (with a cytosol-targeted PKAi) on PCH development. 3) To determine the effects of nuclear PKA activation by PKIα knockout or nuclear PKA overexpression or nuclear PKA inhibition on the development of PCH. The accomplishment of the proposed studies will provide novel insights into the roles of compartmental PKA and its regulation by PKIα in the development of PCH. New knowledge generated from this project will shed light into developing novel therapeutic strategy for the prevention and treatment of PCH in patients.