MOLECULAR PHYSIOLOGY OF LONG QT SYNDROME & IDIOPATHIC VENTRICULAR FIBRILLATION

该项目的长期目标是了解离子通道基因突变导致心律失常导致通道功能障碍的分子基础，并基于这些发现在细胞和器官水平探索潜在的治疗方法。子项目1将探索KvLGT1和心脏I/Ks通道激活剂对心脏复极的作用和正常化机制。最近发现了一种新的苯二氮卓类药物(R-L3)，它能增加I/Ks的幅度，缩短动作电位时程。我们将研究该化合物对非洲爪哇卵母细胞中异源表达的KvLGT1和水貂通道亚基的影响。我们还将确定该化合物是否能抑制兔心肌细胞去极化后的早期，并防止离体灌流心脏的尖端扭矩。子项目2将研究导致长QT综合征和特发性室颤的SCN5A突变的生物物理特性。在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被用来理解SCN5A突变的异常通道功能。子项目3将描述HERG的突变和新发现的导致长QT综合征的基因，这些基因在项目1中被确定。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。我们最初将集中在HERG的突变上，这将为我们提供对通道功能的结构基础的见解。

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.