Caveolae and Cardiac Repolarization

描述(申请人提供)：心肌复极特性的改变经常是各种心脏疾病对室性心律失常易感性增加的基础，但对心脏复极的控制尚不完全清楚。导致动作电位时程延长或缩短的复极异常可导致心律失常。心肌细胞中多种不同的离子通道影响动作电位复极，至少有13个不同的基因与遗传性长QT综合征有关，这突显了参与复极的离子通道和调控通路的多样性。例如，小窝蛋白-3基因(CAV3)的突变被认为是遗传性长QT综合征(LQTS)的原因之一。Cav-3是一种必需的支架蛋白，在细胞中形成特殊的膜微域被称为小窝，它是多个信号分子和离子通道蛋白的家园。在这项应用中提出的初步数据显示，基因消融小鼠心脏中的小窝蛋白-3显著延长了心脏复极。这项拟议的研究将检验心脏小窝通过控制特定通道的密度和功能特性来提供心脏复极的综合调节的假设。使用心脏特异调节Cav-3表达的基因工程小鼠模型和人类iPS细胞-心肌细胞模型，该提案将从三个特定的目的研究小窝在心脏复极调节中的作用：1) 确定心肌细胞Cav-3丰度的变化对小窝密度和心脏复极的影响；2)评估Cav-3丰度的变化和LQTS相关的Cav-3突变对电压门控性钾电流的密度和生物物理性质的影响；以及3)确定Cav-3野生型和LQTS相关突变如何调节ICa，L的密度和特性。这些研究将为控制心脏复极和可导致心律失常的疾病中的异常提供新的机械性的新见解。

DESCRIPTION (provided by applicant): Changes in the repolarization properties of cardiac muscle frequently underlie the increased susceptibility to ventricular arrhythmias in a variety of heart diseases, but the control of cardiac repolarization is incompletely understood. Abnormalities of repolarization resulting in action potential duration prolongation or shortening can be pro-arrhythmic. Multiple different ion channels in cardiomyocytes impact action potential repolarization, and the diversity of ion channels and regulatory pathways involved in repolarization is highlighted by the association of at least 13 distinct genes with the inherited long QT syndrome which is due to delayed repolarization. For example, mutations in the caveolin-3 gene (CAV3) have been implicated as one cause of the inherited Long QT syndrome (LQTS). Cav-3 is an essential scaffolding protein required for the formation of specialized membrane microdomains in cells referred to as caveolae which are home to multiple signaling molecules and ion channel proteins. Preliminary data presented in this application show that genetic ablation of caveolin-3 in the mouse heart dramatically prolongs cardiac repolarization. The proposed research will test the hypothesis that cardiac caveolae provide integrated regulation of cardiac repolarization by controlling the density and functional properties of specifc ion channels. Using both genetically engineered mouse models with cardiac-specific regulation of Cav-3 expression as well as human iPS cell-cardiomyocyte models, the proposal will examine the role of caveolae in the regulation of cardiac repolarization in three specific aims: 1) Determine the impact of changes in the abundance of Cav-3 in cardiomyocytes on the density of caveolae and on cardiac repolarization; 2) Evaluate the impact of changes in Cav-3 abundance and LQTS-associated Cav-3 mutations on the density and biophysical properties of voltage-gated potassium currents; and 3) Determine how wild type Cav-3 and LQTS-associated mutations of Cav-3 regulate the density and properties of ICa,L. These studies will provide mechanistic new insights into the control of cardiac repolarization and abnormalities in disease which can result in arrhythmias.