Calsequestrin in Ventricular Arrhythmia and Sudden Death

Calsequestrin 治疗室性心律失常和猝死

• 批准号: 8600965
• 负责人: Bjorn C Knollmann
• 金额: $ 38.22万
• 依托单位: VANDERBILT UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-15 至 2015-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8600965
• 关键词: Adult; Animal Model; Arrhythmia; Binding; Binding Proteins; Biochemical; Calsequestrin; Cardiac; Catecholamines; Cells; Cessation of life; Coronary; Data; Defect; Disease; Electron Microscopy; Exercise; Exhibits; Functional disorder; Funding; Heart; Heart Diseases; Human; Infusion procedures; Inherited; Injury; Knockout Mice; Ligation; Link; Mouse Protein; Mus; Muscle Cells; Mutation; Myocardial Infarction; Myocardial Ischemia; Myocardium; Patients; Phenotype; Predisposition; Proteins; Publishing; Purkinje Cells; Role; RyR2; Sarcoplasmic Reticulum; Sudden Death; Syndrome; System; Tamoxifen; Testing; Tissues; Ventricular; Ventricular Arrhythmia; Ventricular Tachycardia; Wild Type Mouse; Work; gene therapy; high risk; in vivo; mouse junctate protein; mouse model; mutant mouse model; novel; novel strategies; premature; prevent; research study; restoration; sudden cardiac death; trafficking; triadin

ABSTRACT Cardiac calsequestrin (CASQ2), and its binding partners junctin and triadin-1 (TRDN), are key regulators of sarcoplasmic reticulum (SR) Ca storage and release. In humans, CASQ2 mutations cause the syndrome of catecholaminergic polymorphic ventricular tachycardia (CPVT) and sudden cardiac death. During the previous funding period, we have generated and studied Casq2 null (Casq2-/-) mice to determine the mechanisms whereby CASQ2 mutations cause electrophysiological instability. We found that despite a lack of Casq2 protein, these mice maintain near normal SR Ca storage, Ca release and contractile function, likely as a result of an expansion of SR volume and drastic reductions in the Casq2 binding proteins triadin-1 and junctin. Casq2-/- mice exhibit the CPVT phenotype, i.e. they develop polymorphic ventricular tachycardia with catecholamine infusion or exercise. Our current concept is that the loss of Ca release refractoriness and premature SR Ca release under conditions of high SR Ca load, results in delayed after-depolarizations, triggered beats and polymorphic ventricular tachycardia. However, if the trigger originates from ventricular myocytes or from specialized cells of the conduction system, the Purkinje cells, is unresolved. Experimental data from a RyR2 mutant mouse model and theoretical considerations favor the Purkinje network. Furthermore, biochemical, electron microscopy and confocal studies show that Casq2 is only found in the terminal cisternae of the junctional SR in close contact with RyR2 Ca release channels. Thus, we hypothesize that the reduced presence of Casq2 near the RyR2 in ventricular myocytes and/or Purkinje cells is a fundamental defect that causes premature SR Ca release and increases arrhythmia susceptibility. This is applicable to inherited syndromes (e.g., Casq2-linked CPVT; Aims 1+2) and potentially acquired heart disease due to defects in the trafficking to and/or retention of Casq2 near the RyR2 (Aim 3). Aim 1. To test the hypothesis that restoration of Casq2 rescues the CPVT phenotype of Casq2-/- mice. Aim 2. To test the hypothesis that loss of Casq2 in Purkinje cells is both necessary and sufficient to cause CPVT Aim 3. To test the hypothesis that Casq2 is reduced near RyR2 Ca release channels in cardiac muscle surviving after myocardial infarction

抽象的 心脏钙螯合蛋白 (CASQ2) 及其结合伙伴 Junctin 和 Triadin-1 (TRDN) 是心脏功能的关键调节因子 肌浆网 (SR) Ca 储存和释放。在人类中，CASQ2 突变会导致以下综合征： 儿茶酚胺能多形性室性心动过速（CPVT）和心源性猝死。此前期间 资助期间，我们生成并研究了 Casq2 null (Casq2-/-) 小鼠以确定其机制 CASQ2 突变导致电生理不稳定。我们发现尽管缺乏 Casq2 蛋白， 这些小鼠维持接近正常的 SR Ca 储存、Ca 释放和收缩功能，可能是由于 SR 体积扩大，Casq2 结合蛋白 triadin-1 和junctin 急剧减少。 Casq2-/- 小鼠表现出 CPVT 表型，即它们因儿茶酚胺而出现多形性室性心动过速 输液或运动。我们目前的概念是Ca释放不应期的丧失和过早的SR Ca 在高 SR Ca 负荷条件下释放，导致延迟后除极、触发搏动和 多形性室性心动过速。然而，如果触发因素源自心室肌细胞或 传导系统的特殊细胞，浦肯野细胞，尚未解决。来自 RyR2 的实验数据 突变小鼠模型和理论考虑有利于浦肯野网络。此外，生化、 电子显微镜和共聚焦研究表明 Casq2 仅存在于末端池中 连接SR与RyR2 Ca释放通道紧密接触。因此，我们假设减少的 心室肌细胞和/或浦肯野细胞中 RyR2 附近存在 Casq2 是一种基本缺陷 导致 SR Ca 过早释放并增加心律失常的易感性。这适用于 遗传综合征（例如 Casq2 相关 CPVT；目标 1+2）和潜在的后天性心脏病 Casq2 运输到 RyR2 附近和/或保留在 RyR2 附近的缺陷（目标 3）。 目标 1. 检验 Casq2 恢复可挽救 Casq2-/- 小鼠 CPVT 表型的假设。 目标 2. 检验以下假设：浦肯野细胞中 Casq2 的缺失对于 引起CPVT 目标 3. 检验心肌中 RyR2 Ca 释放通道附近 Casq2 减少的假设 心肌梗塞后存活