Molecular Mechanisms of Ankyrin-B-based Arrhythmia

描述（由申请人提供）：心脏兴奋性缺陷是人类心律失常和心源性猝死的基础，心源性猝死是发达国家死亡的主要原因。最近的研究结果表明，人类心律失常的基因突变的基础上，影响心脏离子通道和转运蛋白的表达/亚细胞定位的一个新的范例。人类4型长QT综合征（LQT 4）是由膜适配器锚蛋白-B（AnkB）的功能缺失突变引起的。LQT 4受试者和AnkB表达降低的小鼠显示出相似的复杂心脏表型，包括心房、心室、传导缺陷和心源性猝死风险。然而，AnkB多肽的分子特性、AnkB在专门的心脏细胞中的表达范围以及AnkB多肽对心脏兴奋性的细胞作用仍然是关键的，但尚未回答的问题。此外，正常心脏中AnkB调节和人类心律失常中功能障碍的潜在机制仍然没有解决。这项研究计划的长期目标是了解心脏中AnkB功能的分子基础。我们假设，协调功能障碍的AnkB多肽在整个心脏创建复杂的表型的人4型长QT综合征由于缺陷的离子通道/转运蛋白运输和膜的稳定性。具体的目的是：1）表征AnkB亚型在心脏不同兴奋细胞类型中的表达和亚细胞分布。2)使用最近开发的慢病毒技术定义AnkB在成年心肌细胞中离子通道/转运蛋白运输和定位的细胞作用。3)表征心脏中AnkB调节的潜在机制，并确定与致命性心律失常相关的人类AnkB功能丧失突变如何影响这种调节。心肌细胞中离子通道和转运蛋白靶向、定位和稳定性的细胞途径基本上是未知的，但为未来的心脏治疗提供了令人兴奋的新靶点。我们建议使用最近开发的表达技术来阐明的分子机制AnkB依赖的细胞通路的离子通道和转运蛋白的靶向，定位和稳定性的生理背景下的原代心肌细胞。预计这些信息将促进对基于AnkB的人类致命性心律失常以及与异常Ca 2+稳态相关的获得性心律失常的潜在机制的理解，并开始定义用于调节细胞兴奋性的潜在未来分子靶点。

DESCRIPTION (provided by applicant): Defects in cardiac excitability are the basis for human arrhythmia and sudden cardiac death, a leading cause of mortality in developed countries. Recent findings demonstrate a new paradigm for human arrhythmia based on gene mutations that affect the expression/subcellular localization of cardiac ion channels and transporters. Human type 4 long QT syndrome (LQT4) results from loss-of-function mutations in the membrane adapter ankyrin-B (AnkB). Subjects with LQT4, and mice with reduced AnkB expression display similar complex cardiac phenotypes including atrial, ventricular, conduction defects, and risk of sudden cardiac death. However, the molecular identities of AnkB polypeptides, scope of AnkB expression in specialized cardiac cells, and cellular role(s) for AnkB polypeptides for cardiac excitability remain critical, yet unanswered questions. Moreover, the mechanisms underlying AnkB regulation in normal heart, and dysfunction in human arrhythmia remain unsolved. The long-term objective of this research proposal is to understand the molecular basis for AnkB function in the heart. We hypothesize that coordinate dysfunction of AnkB polypeptides throughout the heart create the complex phenotype of human type 4 long QT syndrome due to defects in ion channel/transporter trafficking and membrane stability. The specific aims are to: 1) Characterize the expression and subcellular distribution of AnkB isoforms in diverse excitable cell types of heart. 2) Define the cellular role(s) of AnkB for ion channel/transporter trafficking and localization in adult cardiomyocytes using recently developed lentiviral techniques. 3) Characterize the mechanisms underlying AnkB regulation in heart, and determine how human AnkB loss-of-function mutations associated with fatal arrhythmia affect this regulation. The cellular pathways underlying ion channel and transporter targeting, localization, and stability in cardiomyocytes are essentially unknown but present an exciting new target for future cardiac therapies. We propose to use recently developed expression techniques to elucidate the molecular mechanisms underlying AnkB-dependent cellular pathways for ion channel and transporter targeting, localization, and stability in the physiological context of the primary cardiomyocyte. It is anticipated that this information will advance understanding of mechanisms underlying AnkB-based human fatal human arrhythmia as well as acquired cardiac arrhythmias associated with abnormal Ca2+ homeostasis, and begin to define potential future molecular targets for the regulation of cellular excitability.