Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, Iowa; Abboud Cardiovascular Research Center, University of Iowa Carver College of Medicine, Iowa City, Iowa.
Division of Cardiovascular Medicine, Department of Internal Medicine, University of Iowa, Iowa City, Iowa.
Heart Rhythm. 2023 Nov;20(11):1548-1557. doi: 10.1016/j.hrthm.2023.07.067. Epub 2023 Aug 3.
Decreased peak sodium current (I) and increased late sodium current (I), through the cardiac sodium channel Na1.5 encoded by SCN5A, cause arrhythmias. Many Na1.5 posttranslational modifications have been reported. A recent report concluded that acute hypoxia increases I by increasing a small ubiquitin-like modifier (SUMOylation) at K442-Na1.5.
The purpose of this study was to determine whether and by what mechanisms SUMOylation alters I, I, and cardiac electrophysiology.
SUMOylation of Na1.5 was detected by immunoprecipitation and immunoblotting. I was measured by patch clamp with/without SUMO1 overexpression in HEK293 cells expressing wild-type (WT) or K442R-Na1.5 and in neonatal rat cardiac myocytes (NRCMs). SUMOylation effects were studied in vivo by electrocardiograms and ambulatory telemetry using Scn5a heterozygous knockout (SCN5A) mice and the de-SUMOylating protein SENP2 (AAV9-SENP2), AAV9-SUMO1, or the SUMOylation inhibitor anacardic acid. Na1.5 trafficking was detected by immunofluorescence.
Na1.5 was SUMOylated in HEK293 cells, NRCMs, and human heart tissue. HyperSUMOylation at Na1.5-K442 increased I in NRCMs and in HEK cells overexpressing WT but not K442R-Na1.5. SUMOylation did not alter other channel properties including I. AAV9-SENP2 or anacardic acid decreased I, prolonged QRS duration, and produced heart block and arrhythmias in SCN5A mice, whereas AAV9-SUMO1 increased I and shortened QRS duration. SUMO1 overexpression enhanced membrane localization of Na1.5.
SUMOylation of K442-Na1.5 increases peak I without changing I, at least in part by altering membrane abundance. Our findings do not support SUMOylation as a mechanism for changes in I Na1.5 SUMOylation may modify arrhythmic risk in disease states and represents a potential target for pharmacologic manipulation.
心脏钠离子通道 Na1.5 编码的峰值钠电流（I）和晚期钠电流（I）的减少，通过多种钠离子通道 Na1.5 的翻译后修饰而发生。最近的一份报告得出结论，急性缺氧通过增加 K442-Na1.5 上的小泛素样修饰（SUMOylation）来增加 I。
本研究旨在确定 SUMOylation 是否以及通过何种机制改变 I、I 和心脏电生理。
通过免疫沉淀和免疫印迹检测 Na1.5 的 SUMOylation。通过在表达野生型（WT）或 K442R-Na1.5 的 HEK293 细胞和新生大鼠心肌细胞（NRCMs）中进行带有/不带有 SUMO1 过表达的膜片钳测量 I。通过心电图和动态遥测研究体内的 SUMOylation 效应，使用 Scn5a 杂合敲除（SCN5A）小鼠和去 SUMOylating 蛋白 SENP2（AAV9-SENP2）、AAV9-SUMO1 或 SUMOylation 抑制剂 anacardic acid。通过免疫荧光检测 Na1.5 的运输。
HEK293 细胞、NRCMs 和人心组织中 Na1.5 被 SUMOylated。Na1.5-K442 的过度 SUMOylation增加了 NRCMs 和过表达 WT 的 HEK 细胞中的 I，但不改变 K442R-Na1.5 的 I。SUMOylation 不改变包括 I 在内的其他通道特性。AAV9-SENP2 或 anacardic acid 减少了 SCN5A 小鼠的 I、延长了 QRS 持续时间并产生了心脏阻滞和心律失常，而 AAV9-SUMO1 则增加了 I 并缩短了 QRS 持续时间。SUMO1 过表达增强了 Na1.5 的膜定位。
K442-Na1.5 的 SUMOylation 增加了峰值 I，而不会改变 I，至少部分原因是改变了膜丰度。我们的发现不支持 SUMOylation 作为 I Na1.5 变化的机制。SUMOylation 可能会改变疾病状态下的心律失常风险，代表了药物干预的潜在靶点。
