Investigating KCNQ1 Mistrafficking in Long QT Syndrome

项目摘要 长QT间期综合征(LQTS)是一种以后者延长为特征的心脏疾病 增加心律失常风险的心电图轨迹(QT间期)的一部分 逮捕，以及意外猝死。大约每2500人中就有1人患有先天性 LQTS的形式，30%-50%的病例是由电压门控钾的突变引起的 通道蛋白KCNQ1(类型1 LQTS或LQT1)。KCNQ1中超过250个LQT1相关突变 但这些突变对通道结构和功能的影响，以及是否 这些突变导致LQT1、IS中KCNQ1功能障碍的机制是常见的 仍然未知。这个被提议的项目的主要目标是探索作弊作为一种潜在的 长QT综合征KCNQ1功能丧失的机制 KCNQ1电压敏感结构域(VSD)LQT1相关突变的研究进展 发现大多数减少了KCNQ1向质膜的转运，并破坏了KCNQ1的稳定性 VSD。更多的研究表明，KCNQ1的突变可以导致内质滞留 网状结构(ER)和蛋白酶体降解增加。这导致了这样的假设： 错误敲击是LQT1中蛋白质功能障碍的常见机制。Mistraffking一直是 在其他几种膜蛋白相关疾病中被确定为一种疾病机制，例如 囊性纤维化和视网膜色素变性，在囊性纤维化的情况下，已经开发出药物来 挽救抽奖失误，缓解疾病症状。这导致了另一种假设，即药物 结合新生的KCNQ1通道并增加其稳定性可以增加KCNQ1的贩运。 根据这些假设，我提出了两个目标：1)对基于KCNQ1的突变进行分类 关于它们对KCNQ1贩运的影响，以及2)开发一种高通量筛选方法来识别 增加细胞表面运输的小分子。在目标1中，我将对所有贩运人口进行分类 可能的KCNQ1变异与基于荧光激活细胞分类(FACS)的深度突变 扫描法。这将使我能够确定大多数LQT1相关突变 导致作弊，并提供有关未知重要性(VU)和其他变量的信息 KCNQ1变异体。在目标2中，我将利用免疫荧光和高含量成像来筛选 增加WT或突变的KCNQ1转运的小分子。这将检验这一假设 KCNQ1错配是可以用小分子挽救的。总而言之，这些目标的结果将提供 进一步了解LQT1中KCNQ1功能障碍的分子机制，并探索 开发LQT1新疗法的可能途径。

Project Summary Long QT syndrome (LQTS) is a cardiac disorder characterized by the prolongation of the latter portion of the electrocardiogram trace (the QT interval) that increases risk of cardiac arrythmia, cardiac arrest, and sudden unexpected death. Approximately 1 in 2500 individuals suffer from the congenital form of LQTS, with 30-50% of cases being caused by mutations in the voltage gated potassium channel protein KCNQ1 (type 1 LQTS, or LQT1). Over 250 LQT1-associated mutations in KCNQ1 have been identified, but the impact of these mutations on the channel’s structure and function, and whether there are common mechanisms through which these mutations lead to KCNQ1 dysfunction in LQT1, is still unknown. The primary goal of this proposed project is to explore mistrafficking as a potential mechanism of KCNQ1 loss of function in long QT syndrome. Previous studies of LQT1-associated mutations in the KCNQ1 voltage sensing domain (VSD) found that the majority decreased KCNQ1 trafficking to the plasma membrane and destabilized the VSD. Additional studies have shown that mutations in KCNQ1 can lead to retention in the endoplasmic reticulum (ER) and increased proteasomal degradation. This has led to the hypothesis that mistrafficking is a common mechanism of protein dysfunction in LQT1. Mistrafficking has been identified as a disease mechanism in several other membrane-protein associated diseases, such as cystic fibrosis and retinitis pigmentosa, and in the case of cystic fibrosis, drugs have been developed to rescue mistrafficking and alleviate disease symptoms. This leads to the additional hypothesis that drugs that bind nascent KCNQ1 channels and increase their stability can increase the trafficking of KCNQ1. In line with these hypotheses, I propose two aims: 1) to classify mutations across KCNQ1 based on their impact on KCNQ1 trafficking, and 2) to develop a high throughput screening method to identify small molecules that increase cell surface trafficking. In Aim 1, I will classify the trafficking of all possible KCNQ1 variants with a fluorescence-activated cell sorting (FACS)-based deep mutational scanning method. This will allow me to determine whether the majority of LQT1-associated mutations cause mistrafficking and also provide information on variants of unknown significance (VUS) and other KCNQ1 variants. In Aim 2, I will utilize immunofluorescence and high content imaging to screen for small molecules that increase WT or mutant KCNQ1 trafficking. This will test the hypothesis that KCNQ1 mistrafficking is rescuable with small molecules. Together, the results of these aims will provide further insight into the molecular mechanisms behind KCNQ1 dysfunction in LQT1 and explore a possible route for developing novel treatments for LQT1.