Compartmental PKA and Pathological Cardiac Hypertrophy

项目概要/摘要： 病理性心脏肥大（PCH）是致死性室性心律失常的独立危险因素， 心衰对于预防或治疗PCH的更有效疗法存在未满足的临床需求。虽然PKA 交感神经/β-肾上腺素能系统刺激后的激活对于心率的正常调节是必需的 和心肌收缩力，交感神经/β-肾上腺素能系统/蛋白激酶A（PKA）的持续激活， 诸如高血压的心血管疾病导致PCH和收缩功能障碍。但委员会仍 目前尚不清楚PKA如何促进PCH，以及操纵PKA活化是否可用于治疗或预防PCH。 PKA活性受心脏内源性PKA抑制肽（PKI）负调节。我们发现， PKI亚型之一PKIα第一次集中在成年心肌细胞的细胞核中， 核PKA活化对刺激不太敏感，活化速率比胞质PKA慢。 此外，压力超负荷降低了PKIα的表达，特别是在细胞核中，并降低了其抑制细胞凋亡的能力。 PKA。当在小鼠中基因消除PKIα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，当肌细胞PKA仅被PKA抑制时， PKIα结构域（PKAi），压力超负荷诱导的PCH被钝化。我们培养的肌细胞研究表明， 这种PCH减少与胞质PKA抑制有关。因此，我们建议PKA的本地化 活化对于其对PCH发展的影响至关重要。取决于蜂窝位置（隔室） 在PKA激活过程中，PKA既可促进压力超负荷引起的PCH，也可抑制压力超负荷引起的PCH。 基于这些初步研究，我们假设：虽然胞浆PKA活化是促肥大的， 核PKA活化具有抗肥大作用，内源性PKIα对核PKA活化具有抑制作用。我们 进一步预测胞质PKA抑制与增强的核PKA将是一个理想的策略，以防止或 治疗PCH。我们将从三个方面检验这一假设：1）确定基因剂量依赖效应， 整体心肌细胞特异性PKA抑制（PKAi）对心脏结构和功能影响的机制 响应肥大应激的重塑。2)为了确定抑制胞浆PKA的作用（用 细胞溶质靶向PKAi）对PCH发育的影响。3)探讨PKIα对核PKA的激活作用 敲除或核PKA过表达或核PKA抑制对PCH的发展的影响。 这些研究的完成将为房室PKA的作用提供新的见解 以及PKIα在PCH发展中的调控作用。从这个项目中产生的新知识将揭示 开发新的治疗策略，用于预防和治疗患者的PCH。

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.