Pathogenesis of HERG Mutations in Human Long QT Syndrome

简介(申请人提供)：先天性长QT间期综合征(LQTS)是一种 与心脏复极延迟和QT延长相关的疾病 心电图上的间隔，这可能导致室性心律失常 心源性猝死。LQTS(LQT2)的主要形式之一是由 人类乙醚-A-GO-GO相关基因(HERG)突变 快速激活延迟整流钾通道。到目前为止，已经有100多个 已在LQTS患者中发现HERG突变。我们之前的工作 已经表明，LQT2中HERG通道功能丧失的一个主要机制是 蛋白质运输缺陷，导致突变通道无法 到达细胞表面。我们还证明了高亲和力的HERG通道阻滞剂 可以纠正一些LQT2突变体的缺陷蛋白运输。的目标 本研究的目的是：(1)研究缺陷蛋白的转运机制 LQT2突变通道，以及(2)确定英雄通道阻滞剂如何拯救 运输有缺陷的LQT2突变通道。我们的假设是(1)LQT2 突变会导致HERO蛋白的错误折叠或不正确组装 被质量控制体系认可，导致ER保留和降级 蛋白酶体，以及(2)与具有高亲和力的英雄通道结合的药物 作为药理伴侣，促进正确的折叠或组装 允许运输到质膜的构象。我们将测试 这些假说有四个具体目的：目的一是确定LQT2是否 突变会导致突变通道的错误折叠或不正确组装；目标2到 分子伴侣在LQT2突变体内质网滞留中的作用研究 途径；目的3研究LQT2突变体 被蛋白酶体识别和降解；以及目标4阐明 高亲和力HERG通道阻滞剂纠正缺陷的机制 LQT2突变通道的蛋白运输。我们将结合使用 生化、免疫组织化学和膜片钳技术研究野生型 HERG和LQT2突变通道在转染组培养细胞中的表达 在无细胞系统中。这些研究将加强我们对如何 错误折叠和不正确组装的LQT2突变通道被识别， ER质量控制体系的保留和降级以及HERG如何渠道 阻滞剂可以改变这些过程，挽救LQT2突变通道。澄清 这些机制是朝着发展的重要一步 先天性LQTS治疗的药理学策略。

DESCRIPTION (provided by applicant): Congenital long QT syndrome (LQTS) is a disease associated with delayed cardiac repolarization and prolonged QT intervals on the electrocardiogram, which can lead to ventricular arrhythmia with cardiac sudden death. One of the major forms of LQTS (LQT2) is caused by mutations in the human ether-a-go-go-related gene (HERG) that encodes the rapidly activating delayed rectifier potassium channel. To date, more than 100 HERG mutations have been identified in patients with LQTS. Our previous work has shown that a major mechanism for loss of HERG channel function in LQT2 is defective protein trafficking which results in failure of mutant channels to reach the cell surface. We also showed that high affinity HERG channel blockers can correct defective protein trafficking of some LQT2 mutants. The goals of this proposal are (1) to study the mechanisms of defective protein trafficking of LQT2 mutant channels, and (2) to determine how HERO channel blockers rescue trafficking defective LQT2 mutant channels. Our hypotheses are (1) LQT2 mutations cause misfolding or improper assembly of HERO protein which is recognized by quality control system leading to ER retention and degradation by the proteasome, and (2) drugs that bind to HERO channels with high affinity act as pharmacological chaperones to promote proper folding or assembly in a conformation that permits trafficking to the plasma membrane. We will test these hypotheses by four specific aims: aim I to determine whether LQT2 mutations cause misfolding or improper assembly of mutant channels; aim 2 to study the role of molecular chaperones in the ER retention of LQT2 mutant channels; aim 3 to investigate the mechanisms by which LQT2 mutants are recognized and degraded by the proteasome; and aim 4 to elucidate the mechanisms by which high affinity HERG channel blockers correct defective protein trafficking of LQT2 mutant channels. We will use a combination of biochemical, immunohistochemical and patch clamp techniques to study wild type HERG and LQT2 mutant channels expressed in transfected tissue culture cells and in cell-free systems. These studies will strengthen our knowledge of how misfolded and improperly assembled LQT2 mutant channels are recognized, retained and degraded by the ER quality control system and how HERG channel blockers modify these processes and rescue LQT2 mutant channels. Elucidating these mechanisms is an important step towards the development of pharmacological strategies for therapies of congenital LQTS.