KCNE4激活CaN-NFAT信号通路促进心肌钙通道重构对慢性缺血性心衰室性心律失常的影响及机制研究

The leading cause of death in chronic ischemic heart failure (HF) patients are sudden cardiac death due to ventricular arrhythmia. The underlying mechanism involves the intracellular signaling pathway-mediated ventricular calcium channel remodeling. As a crucial member of the arrhythmia-susceptibility KCNE gene family, KCNE4 creates a multifactorial substrate for arrhythmogenesis via interaction with signaling pathways. Our preliminary results showed that KCNE4 encoded protein (MiRP3) expression was attenuated in left ventricles of chronic ischemic failure hearts. Meanwhile, KCNE4 deletion caused long QT syndrome and predisposed to ischemia-induced ventricular arrhythmia. KCNE4 disruption could result in prolonged action potential and impaired calcium handling after chronic ischemic heart failure. It was also found that KCNE4 deletion caused an elevated expression of MCIP protein which interacts with CaN-NFAT signaling pathway. Therefore, KCNE4 knockout mice will be employed in the current project and we aim to determine how KCNE4 deletion affects arrhythmogenesis in chronic ischemic heart failure and how it generates electric substrates for postischemic calcium remodeling. Its interaction with calcium α subunits will also be studied. Next, the role of KCNE4 in CaN-NFAT pathway is further evaluated, and in combination with cell culture experiments, we aim to determine the mechanism by which KCNE4 regulates arrhythmogenesis in chronic ischemic heart failure by modulating calcium channel remodeling upon activation of CaN-NFAT signaling pathway. By understanding the KCNE4 related HF arrhythmia pathogenesis, completion of these studies will provide important mechanistic insight into the role of KCNE4 in arrhythmogenesis during chronic ischemic heart failure. Our proposed studies may also allow for accelerated development of therapeutic agents for HF related ventricular arrhythmia.

慢性缺血性心力衰竭（心衰）病人的主要死因是心衰期恶性室性心律失常导致的心源性猝死，细胞内信号通路介导的心室钙重构是其重要机制。KCNE4作为心律失常致病基因KCNE家族的重要成员，我们发现，KCNE4在慢性缺血性心衰心室表达减弱。而其缺陷可致长QT综合征，对心肌缺血致室性心律失常易感，使心衰心室肌动作电位时程延长，钙稳态受损，并能作用于调节钙通道的CaN-NFAT信号通路的MCIP结合蛋白。本研究旨在通过KCNE4基因敲除小鼠，研究KCNE4对缺血性心衰室性心律失常事件的影响；研究其对心衰心肌钙重构电流的影响及其调控相关钙通道α亚基的机制；明确其对缺血性心衰CaN-NFAT信号通路的影响，并结合体外实验，研究心衰后KCNE4激活CaN-NFAT通路通过钙重构对室性心律失常的调节机制，阐明KCNE4在缺血性心衰室性心律失常发病机制中的作用，为慢性缺血性心衰室性心律失常的防治提供新的理论基础。

慢性缺血性心衰导致的恶性室性心律失常是心衰病人的主要死因，目前仍缺乏有效的治疗手段。本项目立足于人类心律失常的致病基因KCNE4，在整体动物，细胞和分子水平上，研究其对慢性缺血性心衰致室性心律失常的影响及其调控机制。该项目发现了KCNE4基因敲除小鼠具有长QT综合征的特征，KCNE4基因敲除能够显著增加缺血诱导的恶性室性心律失常的发生率和严重程度，且成性别依赖性。在慢性缺血性心衰情况下，KCNE4基因缺陷小鼠更易发生心衰后室性心律失常，不仅如此，我们还发现，慢性缺血性心衰时，心肌细胞钙通道开放受到KCNE4的调控。KCNE4表达下调，可激活CaN-NFAT信号通路，进一步促进心衰心肌钙重构，导致慢性缺血性心衰室性心律失常发生。本研究阐明了KCNE4能够对心衰心律失常的发生进行调控的主要机制，进一步深化了对慢性缺血性心衰导致室性心律失常的认识，为新的诊疗手段的实施，以及临床治疗靶点的选择提供了理论依据。