心脏钠通道Nav1.5的SUMOylation化在心肌缺血致心律失常中的作用及其机制研究

Sudden cardiac death (SCD) caused by arrhythmia is one of the major causes of death from myocardial infarction (MI), but the mechanism has not yet been fully explored. The prolongation of QT interval is the basis of arrhythmia after MI. The gain-of-function of the congenital or acquired cardiac sodium channel (Nav1.5) is involved in the prolongation of QT interval and arrhythmogenesis. Our preliminary data showed that SUMOylation of Nav1.5 leading to enhanced Nav1.5 expression and increased transient sodium current and window current. We also found hypoxia increases the SUMOylation level of Nav1.5. This proposal is hypothesized that hypoxia-induced SUMOylation could increase the channel expression and sodium current density as well as window current of Nav1.5 channel, which in turn resulting in delayed repolarization of myocytes, prolongation of QT interval and increased risk of arrhythmogenesis and SCD. In this proposal, Nav1.5-HEK and iPSC-CMs cells and MI models from deSUMOylation knockout mice were used as experimental models. Using molecular biology and patch clamp techniques, we will investigate whether and how the SUMOylation modification of Nav1.5 involves in the arrhythmogenesis after MI. Successfully conducting the proposed study will provide a theoretical basis for the mechanism of SCD caused by arrhythmia, and develop novel therapeutic targets for the reduction of SCD after MI.

心律失常致心源性猝死（SCD）是心梗的主要死因之一，但机制尚未完全探明。QT间期延长是心梗后心律失常的基础，心脏钠通道Nav1.5功能的先天性或获得性增强参与QT间期延长和心律失常的发生。我们发现SUMOylation化修饰增加Nav1.5通道的表达及功能，而低氧可增加Nav1.5的SUMOylation化水平，由此假设心梗后低氧激活Nav1.5的SUMOylation化修饰，增加Nav1.5的表达及快钠电流密度和窗电流，引起心肌细胞复极延迟，QT间期延长，增加心律失常或SCD风险。本研究拟以Nav1.5-HEK及iPSC-CMs细胞以及去SUMOylation化基因敲除小鼠心梗模型为对象，采用分子生物学、膜片钳技术等方法，阐明Nav1.5的SUMOylation化修饰及其介导心梗后心律失常的分子机制。预期结果将为心梗后心律失常的发生机制提供理论依据，为降低心梗后SCD发生提供治疗靶点。

研究背景：恶性心律失常、心源性猝死（SCD）是心梗的主要死因之一，但其机制尚不明确。心梗后常见心电图QT间期延长，SCN5A基因编码的心脏钠通道NaV1.5的功能获得性改变可导致QT间期延长，而QT 间期延长可以增加心律失常发生风险。转录后SUMOylation化修饰参与多种蛋白的转录后修饰，调节蛋白的表达及功能。而低氧可激活神经型钠通道的SUMOylation化修饰。心肌梗死后由于罪犯血管的狭窄或堵塞导致远端供血区心肌缺血、缺氧。.研究目的：证实心梗后低氧激活心肌NaV1.5的SUMOylation化修饰可能介导心梗后心律失常的假说。.研究方法：分别以体外细胞模型（NaV1.5-HEK及iPSC-CMs细胞）及在体动物模型（野生型小鼠、SENP基因敲除小鼠心梗模型）为实验对象，采用细胞生物学、分子生物学、膜片钳技术等方法。.研究结果：①发现泛素蛋白修饰分子（small ubiquitin-like modifier，SUMO）1增强心脏NaV1.5通道的表达及INa,T窗电流，而特异性去SUMO化蛋白酶（SUMO-specific protease，SENP）2降低NaV1.5通道的表达及INa,T电流密度。②进一步发现SUMO1通过结合至NaV1.5通道的K442位和K1683位氨基酸而增加NaV1.5通道的SUMOylation化水平。③心脏特异性敲除SENP2后小鼠心房和心室中NaV1.5通道表达均明显增加，容易出现室性心律失常。④进一步发现低氧培养环境增强NaV1.5通道的SUMOylation化水平，增加NaV1.5通道和SUMO1的表达，而不改变SENP1的表达。.研究结论：SUMOylation化修饰调节心脏NaV1.5通道的表达及功能，而低氧微环境增强NaV1.5通道的SUMOylation化修饰水平，初步提示NaV1.5钠通道的SUMOylation化修饰调节（包括SUMOylation和deSUMOylation）在心梗后心律失常发生过程中的作用。.

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