Mechanisms of calcium-induced arrhythmias in arrhythmogenic right ventricular cardiomyopathy

项目摘要/摘要 致心律失常性右室心肌病是一种复杂的遗传性心脏疾病 通过桥粒蛋白质的突变，如蛋白亲和素-2(PKP2)。心律失常，以及潜在的 猝死，通常发生在ARVC患者的疾病早期阶段，这是一种“隐匿期”， 在结构性心肌病发病前出现。它们的分子和细胞机制 心律失常事件仍不清楚，阻碍了寻找有效的治疗患者的策略。我的长期生活 目的是描述ARVC中心律失常的机制，并确定潜在的药物靶点以预防 心源性猝死。用三苯氧胺()诱导的PKP2(PKP2cKO)消融小鼠形成表型 人类ARVC的诱发：心律失常发生率高但无结构重构的隐匿期 14日龄右室优势型心肌病，21日龄右室优势型心肌病，心脏双室型心肌病 失败和死亡在术后约42天。我们报道了PKP2cKO心脏表现出明显的 在疾病进展的不同阶段，但最显著的是，在疾病发展的隐藏阶段 疾病。本研究旨在阐明PKP2缺陷性心脏心律失常的机制。 聚焦于发生钙离子调节的微域。我假设心脏功能不全 Ryanodine受体(RyR2)，细胞内主要的钙释放通道，以及随之而来的钙错误处理 在PKP2cKO小鼠和ARVC中，心律失常的关键触发因素。这些目标将考验我的 假设：1)确定蛋白激酶C(PKC)磷酸化在RyR2通道调节中的作用 功能和钙稳态。初步数据表明，RyR2正在经历磷酸化 PKP2cKO心脏在2810岁。这个先前未知的位点是一个预测的PKC底物。我假设 RyR2在Thr2810处的PKC磷酸化调节通道功能并参与心律失常的发生 病变心脏组织中钙离子的释放。2)明确RyR2功能障碍在发病和进展中的作用 在PKP2cKO小鼠中发现心脏病的可能性。初步数据显示RyR2在Thr2810和Ser2030处的磷酸化 在ARVC中增加。我假设在这些位点抑制RyR2的磷酸化可以防止心律失常 和PKP2cKO小鼠猝死。3)检测RyR2调节剂预防心律失常的效果 在PKP2缺乏的心脏中。我推测RyR2的药理调节有益于预防 PKP2cKO小鼠和心脏的心律失常。这些目标的完成将为我们提供对 PKP2cKO缺乏症模型中RyR2功能的调节及其机制 基础ARVC。我预计这些结果将推动RyR2作为潜在治疗靶点的地位 减少心律失常的风险，延长ARVC患者的预期寿命。

PROJECT SUMMARY / ABSTRACT Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a complex inherited disorder of the heart produced by mutation in proteins of the desmosome, such as plakophilin-2 (PKP2). Cardiac arrhythmias, and potentially sudden death, often occur in ARVC patients during the early stages of the disease, a “concealed phase” that presents before the onset of structural cardiomyopathy. The molecular and cellular mechanisms of these arrhythmic events remain unclear, hindering the search for effective strategies to treat patients. My long-term goal is to delineate the mechanisms of arrhythmia in ARVC and to identify potential drug targets to prevent sudden cardiac death. Mice with tamoxifen (TAM)-induced ablation of PKP2 (PKP2cKO) develop a phenotype evocative of human ARVC: a concealed stage with high incidence of arrhythmia but without structural remodeling at 14 days, cardiomyopathy of right ventricle dominance at 21 days, and biventricular cardiomyopathy, heart failure and death at ~42 days post-TAM. We reported that PKP2cKO hearts show significant dysregulation of Ca2+ handling at different stages of disease progression but, most remarkably, during the concealed stage of the disease. This proposal aims to elucidate the mechanisms underlying cardiac arrhythmia in PKP2-deficient hearts focusing on the microdomain where Ca2+ regulation takes place. I hypothesize that dysfunction of the cardiac ryanodine receptor (RyR2), a major intracellular Ca2+ release channel, and the ensuing Ca2+ mishandling are critical triggers of cardiac arrhythmia in the PKP2cKO mouse and, hence, in ARVC. These aims will test my hypothesis: 1) Determine the role of protein kinase C (PKC) phosphorylation in the regulation of RyR2 channel function and calcium homeostasis. Preliminary data suggest that RyR2 is undergoing phosphorylation in PKP2cKO hearts at Thr2810. This previously uncharacterized site is a predicted PKC substrate. I hypothesize that PKC phosphorylation of RyR2 at Thr2810 regulates channel function and contributes to arrhythmogenic Ca2+ release in the diseased heart. 2) Define the contribution of RyR2 dysfunction in the onset and progression of heart disease in PKP2cKO mice. Preliminary data suggest that RyR2 phosphorylation at Thr2810 and Ser2030 is increased in ARVC. I hypothesize that inhibition of RyR2 phosphorylation at these sites prevents arrhythmia and sudden death in PKP2cKO mice. 3) Test the efficacy of RyR2 modulators for the prevention of arrhythmia in PKP2-deficient hearts. I hypothesize that pharmacological modulation of RyR2 is beneficial to prevent arrhythmia in PKP2cKO mice and hearts. The completion of these aims will provide significant insight into the regulation of RyR2 function in a model of PKP2cKO deficiency and hence shed light on the mechanisms underlying ARVC. I anticipate these results will advance the status of RyR2 as a potential therapeutic target to reduce the risk of arrhythmias and increase life-expectancy of patients with ARVC.