Molecular Mechanisms of RyR2-triggered Arrhythmias

RyR2 触发心律失常的分子机制

• 批准号: 8056061
• 负责人: Hector H Valdivia
• 金额: $ 36.74万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-03-08 至 2011-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8056061
• 关键词: A Mouse; Acute; Adrenergic Agents; Adrenergic beta-Antagonists; Affect; Agonist; Amino Acids; Arrhythmia; Binding; Calcium Signaling; Cardiac; Cardiac Myocytes; Cell physiology; Cells; Clinical; Coupling; Dependence; Development; Diastole; Disease; Echocardiography; Electrocardiogram; Emotional Stress; Engineering; Environment; Exercise; Experimental Designs; Experimental Models; FKBP1B gene; Frequencies; Functional disorder; Genes; Health; Heart; Homeostasis; Hot Spot; Human; Image; Individual; Injection of therapeutic agent; Ion Channel; Ion Channel Protein; Kinetics; Knock-in Mouse; Laser Scanning Confocal Microscopy; Lasers; Lead; Link; Mediating; Membrane Potentials; Molecular; Mus; Muscle Cells; Mutation; Output; Pattern; Perfusion; Phenotype; Phosphorylation; Physiology; Point Mutation; Potassium Channel; Propranolol; Proteins; Regulation; Role; RyR2; Ryanodine; Ryanodine Receptor Calcium Release Channel; Ryanodine Receptors; Sarcoplasmic Reticulum; Severities; Signal Transduction; Site; Speed; Stimulus; Sudden Death; Syndrome; Tachyarrhythmias; Tachycardia; Techniques; Telemetry; Testing; Therapeutic; Ventricular; Ventricular Arrhythmia; Ventricular Tachycardia; Wild Type Mouse; adrenergic; falls; gain of function; homologous recombination; mouse model; mutant; photolysis; premature; prevent; research study

DESCRIPTION (provided by applicant): Ryanodine receptors (RyRs) are the Ca2+ release channels of sarcoplasmic reticulum that provide the majority of Ca2+ necessary to induce contraction of cardiac cells. In their intracellular environment, RyRs are regulated by a variety of cytosolic and luminal factors so that their output signal (Ca2+) induces finely graded cell contraction without igniting cellular processes that may lead to aberrant electrical activity (ventricular arrhythmias), the main cause of sudden death (SD). The importance of RyR dysfunction has been recently highlighted with the demonstration that point mutations in the cardiac RyR gene (hRYR2) are associated with Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT), an arrhythmogenic syndrome characterized by the development of adrenergically-mediated ventricular tachycardia in individuals with an apparently normal heart. The vast majority of CPVT mutations have been localized to three loci ("hot spots") of the RyR2 protein that affect different aspects of RyR function, however, the molecular mechanism that links a mutation in the RyR2 protein and the development of tachyarrhythmias remains incompletely understood. Our general hypothesis is that CPVT mutations cause multiple forms of RyR2 dysfunction, with the severity of the phenotype determined by the hierarchy of the affected domain in the control of Ca2+ release. To test this hypothesis, we will use single RyR2 channels, isolated ventricular myocytes and whole hearts from wild-type mice and knock-in mouse models of CPVT to: (1) determine whether distinct patterns of RyR2 dysfunction emerge from each of the three "hot spots" altered by CPVT mutations; (2) determine whether the presumably diverse RyR2 dysfunctions elicited by mutations in each of the three "hot spots" converge into a preponderant cellular mechanism of aberrant electrical activity; and (3) determine if the knock-in mouse models of CPVT develop similar phenotype and respond equally to 2-adrenergic stimulation and 2-blockers. We will use an array of state-of-the-art techniques including kinetic analysis of single channel activity by laser photolysis of "caged" Ca2+, high-speed Ca2+ imaging with laser scanning confocal microscopy, and recording of aberrant electrical activity in whole, beating hearts. The proposed experimental design will therefore combine molecular, cellular, and whole heart studies to elucidate the molecular mechanisms of RyR-initiated tachyarrhythmias with an unprecedented level of integrative physiology. PUBLIC HEALTH RELEVANCE: Mutations in ion channels, the proteins that are responsible for generating electrical and calcium signals in the heart, can cause tachycardia and sudden death. This project studies how mutations in one important ion channel called the calcium release channel (ryanodine receptor) cause ventricular arrhythmia and sudden death. Successful completion of this study will allow us to rationalize a therapeutic approach for the optimal treatment of these disorders.

描述（由申请人提供）：Ryanodine 受体 (RyRs) 是肌浆网的 Ca2+ 释放通道，提供诱导心肌细胞收缩所需的大部分 Ca2+。在细胞内环境中，RyR 受到多种胞质和腔内因子的调节，因此其输出信号 (Ca2+) 会诱导精细分级的细胞收缩，而不会引发可能导致异常电活动（室性心律失常）的细胞过程，而异常电活动是猝死 (SD) 的主要原因。最近有研究表明，心脏 RyR 基因 (hRYR2) 的点突变与儿茶酚胺能多形性室性心动过速 (CPVT) 相关，RyR 功能障碍的重要性得到了强调，CPVT 是一种致心律失常综合征，其特征是在心脏表面正常的个体中发生肾上腺素介导的室性心动过速。绝大多数 CPVT 突变位于 RyR2 蛋白的三个位点（“热点”），影响 RyR 功能的不同方面，然而，将 RyR2 蛋白突变与快速心律失常的发展联系起来的分子机制仍不完全清楚。我们的一般假设是 CPVT 突变导致多种形式的 RyR2 功能障碍，表型的严重程度由控制 Ca2+ 释放的受影响结构域的层次结构决定。为了检验这一假设，我们将使用单个 RyR2 通道、来自野生型小鼠的分离心室肌细胞和整个心脏以及 CPVT 敲入小鼠模型来：（1）确定 CPVT 突变改变的三个“热点”中的每一个是否都出现不同的 RyR2 功能障碍模式； (2) 确定三个“热点”中每一个的突变引起的可能不同的 RyR2 功能障碍是否会汇聚成异常电活动的主要细胞机制； (3) 确定 CPVT 敲入小鼠模型是否会产生相似的表型并对 2-肾上腺素能刺激和 2-阻滞剂产生相同的反应。我们将使用一系列最先进的技术，包括通过激光光解“笼中”Ca2+对单通道活动进行动力学分析、使用激光扫描共焦显微镜进行高速Ca2+成像，以及记录整个跳动心脏的异常电活动。因此，拟议的实验设计将结合分子、细胞和全心脏研究，以前所未有的综合生理学水平阐明 RyR 引发的快速心律失常的分子机制。 公共健康相关性：离子通道（负责在心脏中产生电信号和钙信号的蛋白质）的突变可能导致心动过速和猝死。该项目研究一种称为钙释放通道（兰尼碱受体）的重要离子通道的突变如何导致室性心律失常和猝死。这项研究的成功完成将使我们能够合理化治疗方法，以实现这些疾病的最佳治疗。