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脏性猝死的基础，这是发达国家死亡的主要原因。最近的发现证明了一种基于基因突变的人类心律失常的新范式，该基因突变影响心脏离子通道和转运体的表达/亚细胞定位。人类4型长QT综合征(LQT4)是由膜适配器ankyrin-B(AnkB)功能缺失突变引起的。携带LQT4的受试者和AnkB表达降低的小鼠表现出相似的复杂心脏表型，包括房性、室性、传导缺陷，以及心脏性猝死的风险。然而，AnkB多肽的分子同一性、AnkB在特定心肌细胞中的表达范围以及AnkB多肽对心脏兴奋性的细胞作用(S)仍然是关键的，尚未回答的问题。此外，AnkB在正常心脏中的调节机制以及在人类心律失常中的功能障碍仍未解决。这项研究计划的长期目标是了解AnkB功能在心脏中的分子基础。我们假设，由于离子通道/转运体运输和膜稳定性的缺陷，AnkB多肽在整个心脏中的协调功能障碍导致了人类4型长QT综合征的复杂表型。其具体目的是：1)研究AnkB亚型在不同类型的心脏兴奋性细胞中的表达和亚细胞分布。2)利用新近发展的慢病毒技术，确定AnkB在成人心肌细胞离子通道/转运体转运和定位中的细胞作用(S)。3)确定心脏AnkB调节的机制，并确定与致死性心律失常相关的人类AnkB功能丧失突变如何影响这一调节。离子通道和转运体在心肌细胞中的靶向性、定位和稳定性的细胞通路基本上是未知的，但为未来的心脏治疗提供了一个令人兴奋的新靶点。我们建议使用最近发展的表达技术来阐明AnkB依赖的细胞通路的分子机制，这些通路在原代心肌细胞的生理环境中用于离子通道和转运体的靶向、定位和稳定性。预计这些信息将促进对基于AnkB的人类致死性人类心律失常以及与钙稳态异常相关的获得性心律失常的机制的理解，并开始确定未来调节细胞兴奋性的潜在分子靶点。

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.