MOLECULAR PHYSIOLOGY OF LONG QT SYNDROME & IDIOPATHIC VENTRICULAR FIBRILLATION

该项目的长期目标是了解导致心律失常的离子通道基因突变引起的通道功能障碍的分子基础，并基于这些发现探索细胞和器官水平的潜在疗法。子项目1将探索KvLGT 1和心脏I/Ks通道激活剂对心脏复极化的作用机制和正常化。最近发现了一种新的苯二氮卓类（R-L3），其增加I/Ks的幅度并缩短动作电位时程。我们将研究该化合物对爪蟾卵母细胞异源表达的KvLGT 1和minK通道亚基的影响。我们还将确定这种化合物是否可以抑制兔心肌细胞的早期后去极化，并预防离体灌注心脏的尖端扭转型室性心动过速。子项目2将研究引起长QT综合征和特发性室颤的SCN 5A突变的生物物理特性。从培养的哺乳动物细胞中异源表达的钠通道记录的门控和离子电流将用于了解SCN 5A突变的异常通道功能。子项目3将描述项目1中发现的HERG突变和新发现的导致长QT综合征的基因。这些研究将利用卵母细胞和培养的哺乳动物细胞表达系统。我们将首先集中在HERG的突变，这将提供深入了解通道功能的结构基础。

The long-term goals of this project are to understand the molecular basis of channel dysfunction caused by mutations in ion channel genes that cause cardiac arrhythmia, and to explore potential therapies at the cellular and organ level based on these findings. Subproject 1 will explore the mechanism of action and normalization of cardiac repolarization by an activator of KvLGT1 and cardiac I/Ks channels. A novel benzodiazepine (R-L3) was recently discovered that increases the magnitude of I/Ks and shortens action potential duration. We will study the effects of this compound on KvLGT1 and minK channel subunits heterologously expressed in Xenopus oocytes. We will also determine if this compound can suppress early after depolarizations in rabbit myocytes and prevent torsades de pointes in isolated perfused hearts. Subproject 2 will investigate the biophysical properties of mutations in SCN5A that cause long QT syndrome and idiopathic ventricular fibrillation. Gating and ionic currents recorded from sodium channels heterologously expressed in cultured mammalian cells will be used to understand abnormal channel function of SCN5A mutations. Subproject 3 will characterize mutations in HERG and newly discovered genes that cause long QT syndrome that are identified in Project 1. These studies will utilize both the oocyte and cultured mammalian cell expression systems. We will initially concentrate on mutations in HERG that will provide insights into the structural basis of channel function.