Regulation of the Cardiac Sodium Channel by Sumoylation

心肌钠离子通道SCN5A(NaV1.5)和内向去极化钠电流(INA)起着关键作用 在调节心房、心室和特殊传导系统的肌细胞的动作电位方面。 SCN5A突变与包括长QT综合征在内的几种心律失常表型有关， Brugada综合征和扩张型心肌病。此外，还观察到Na+通道功能在 心力衰竭，导致传导减慢和基于折返机制的室性心律失常。 小泛素样修饰物(SUMO)，翻译后修饰蛋白质上的赖氨酸残基。减少量 心脏钙处理蛋白的SUMO化与人类心力衰竭有关。它的意义 苏莫化在调节心脏电活动中的作用尚不清楚。我们的初步数据显示， 心脏患者中与适当除颤器电击相关的SUMO1基因多态性 失败，这表明SUMO1改变了心律失常的风险。鉴于我们之前的工作证明了乙酰化 赖氨酸残基上的SCN5A减少了心脏钠电流，我们现在假设除了 乙酰化，SCN5A被SUMO化后翻译修饰，而SUMO-SCN5A对心脏至关重要 钠电流和心脏的正常电活动。这一假设是基于非常新颖的初步假设 数据表明，SUMO1修饰SCN5A并刺激Na+电流，而去SUMO1抑制INA和 在体内加速心律失常。 这一应用将深入探讨苏莫化和去苏莫化对心肌Na+的作用 当前，表征它们对通道特性、表达、泛素化、乙酰化、运输 以及与其已知合作伙伴Sirtuin1的互动。该提案将确定SCN5A中的赖氨酸残基是 SUMO化，并探索这些赖氨酸SUMO化对心脏Na+电流的重要性。会的 开发和使用最先进的生物试剂，包括一种新型的非糖基化NaV1.5敲击剂 小鼠、体内Sumoylate和去Sumoylate NaV1.5的嗜心病毒载体和转基因小鼠 过度表达相扑蛋白。它将利用基础和老鼠电生理学家的专业知识， 分子生物学家和心脏糖基化方面的专家。使用这些试剂，并与集体 调查小组的专业知识，它将确定SCN5A SUMO化是否在心力衰竭中发生改变，以及 心脏SUMO化改变衰竭和非衰竭心脏的心律失常风险。 SCN5A的相扑修饰将识别一种新的心脏INA调节机制，并具有 心力衰竭患者潜在的临床相关性。通过这样做，它将打开使用相扑的大门 蛋白质作为心律失常高危患者的治疗剂。

The cardiac Na+ channel SCN5A (Nav1.5) and the inward depolarizing Na+ current (INa) play a critical role in regulating the action potential of myocytes in the atrium, ventricle, and specialized conduction system. Mutations in SCN5A are associated with several arrhythmia phenotypes including long QT syndrome, Brugada syndrome, and dilated cardiomyopathy. In addition, loss of Na+ channel function is observed during heart failure, leading to conduction slowing and ventricular arrhythmias based on re-entrant mechanisms. Small Ubiquitin-like Modifiers (SUMOs), post-translationally modify lysine residues on proteins. Decrease in SUMOylation of cardiac calcium-handling proteins is associated with human heart failure. The significance of SUMOylation in regulating cardiac electrical activity is not known. Our preliminary data identifies a polymorphism in the SUMO1 gene that associates with appropriate defibrillator shocks in patients with heart failure, suggesting that SUMO1 modifies arrhythmia risk. Given our prior work demonstrating that acetylation of SCN5A on a lysine residue decreases cardiac sodium current, we now hypothesize that in addition to acetylation, SCN5A is post-translationally modified by SUMOylation, and SUMO-SCN5A is vital for the cardiac Na+ current and for normal electrical activity in the heart. This hypothesis is based on very novel preliminary data that SUMO1 modifies SCN5A and stimulates the Na+ current, whereas de-SUMOylation inhibits INa and precipitates cardiac arrhythmias in vivo. This application will explore in-depth the role of SUMOylation and de-SUMOylation on the cardiac Na+ current , characterizing their effect on channels properties, expression, ubiquitination, acetylation, trafficking, and interaction with its known partner Sirtuin1. The proposal will identify the lysine residues in SCN5A that are SUMOylated, and explore the importance of SUMOylation of these lysines on the cardiac Na+ current. It will develop and use state-of-the-art biological reagents, including a novel non-SUMOylatable Nav1.5 knockin mouse, cardiotropic viral vectors to SUMOylate and de-SUMOylate Nav1.5 in vivo, and transgenic mice overexpressing SUMO proteins. It will leverage the expertise of basic and mouse electrophysiologists, molecular biologists, and experts in cardiac SUMOylation. Using these reagents, and with the collective expertise of the investigative team, it will determine if SCN5A SUMOylation is altered in heart failure, and if cardiac SUMOylation modifies arrhythmic risk in failing and non-failing hearts. SUMO modification of SCN5A will identify a new mechanism for regulation of cardiac INa, and one that has potential clinical relevance in patients with heart failure. In doing so, it will open the door for using SUMO proteins as therapeutic agents in patients at risk for cardiac arrhythmias.