Department of Pharmacology, Beijing Key Laboratory of Metabolic Disturbance Related Cardiovascular Disease, School of Basic Medical Sciences, Capital Medical University, District of Fengtai, Street of Youanmenwai, #10 Xitoutiao, Beijing, 100069, People's Republic of China.
The Affiliated Suzhou Hospital of Nanjing Medical University, Suzhou, 215008, Jiangsu, People's Republic of China.
Basic Res Cardiol. 2019 Aug 28;114(5):40. doi: 10.1007/s00395-019-0748-8.
Connexin 43 (Cx43)-associated gap junctions form electrical and mechanical conduits between adjacent ventricular cardiomyocytes, ensuring coordinate electrical excitation and synchronic contraction for each heartbeat. Cx43 dephosphorylation is a characteristic of ischemia, arrhythmia, and a failing and aging myocardium, but the exact phosphosite(s) triggering myocardial apoptosis and electrical disturbance and its underlying mechanisms are unclear. We previously found that Cx43-serine 282 phosphorylation (pS282) can regulate cardiomyocyte survival and electrical stability. Here, we investigated the hypothesis that S282 dephosphorylation occurs in and contributes to ischemia/reperfusion (I/R)-induced cardiac injury. We found enhanced Cx43-pS262 and Cx43-pS368 but decreased Cx43-pS282 in rat hearts subjected to I/R (30 min/2 h). I/R rats had ventricular arrhythmias and myocardial apoptosis with activation of the p38 mitogen-activated protein kinase (p38)/factor-associated suicide (Fas)/Fas-associating protein with a novel death domain (FADD) pathway. Similarly, S282 dephosphorylation, abnormal Ca transients, cell apoptosis and p38/Fas/FADD activation also occurred in neonatal rat ventricular myocytes exposed to anoxia/reoxygenation (12/6 h). To confirm the causative role of S282 dephosphorylation in cardiac injury, rat hearts were intramyocardially injected with a virus carrying the S282 mutant substituted with alanine (S282A), thus causing arrhythmias and reducing cardiac output and myocardial apoptosis with p38/Fas/FADD pathway activation. Moreover, Cx43-S282A mice displayed arrhythmias and impaired cardiac output with global myocardial apoptosis. Our findings revealed that Cx43 dephosphorylation at S282 triggers arrhythmias and, at least partly, contributes to cardiomyocyte death upon I/R by activating the p38/Fas/FADD pathway, providing a novel molecular mechanism and potential target for protecting against cardiac I/R injury.
间隙连接蛋白 43（Cx43）相关的缝隙连接在相邻的心室心肌细胞之间形成电和机械通道，确保每个心跳的协调电兴奋和同步收缩。Cx43 的去磷酸化是缺血、心律失常以及衰竭和老化心肌的特征，但触发心肌细胞凋亡和电干扰的确切磷酸化位点及其潜在机制尚不清楚。我们之前发现 Cx43-丝氨酸 282 磷酸化（pS282）可以调节心肌细胞的存活和电稳定性。在这里，我们研究了 S282 去磷酸化是否发生在缺血/再灌注（I/R）诱导的心脏损伤中，并对此假说进行了验证。我们发现，在 I/R（30 分钟/2 小时）后的大鼠心脏中，Cx43-pS262 和 Cx43-pS368 增强，但 Cx43-pS282 减少。I/R 大鼠出现室性心律失常和心肌细胞凋亡，同时激活 p38 丝裂原激活蛋白激酶（p38）/因子相关自杀（Fas）/Fas 相关蛋白含新型死亡域（FADD）途径。同样，在缺氧/复氧（12/6 小时）处理的新生大鼠心室肌细胞中也发生 S282 去磷酸化、异常钙瞬变、细胞凋亡和 p38/Fas/FADD 激活。为了证实 S282 去磷酸化在心脏损伤中的因果作用，我们将携带 S282 突变为丙氨酸（S282A）的病毒注入大鼠心肌内，导致心律失常，降低心输出量，并通过 p38/Fas/FADD 途径激活导致心肌细胞凋亡。此外，Cx43-S282A 小鼠表现出心律失常和心输出量受损，伴有整体心肌细胞凋亡。我们的研究结果表明，Cx43 在 S282 处的去磷酸化触发心律失常，并通过激活 p38/Fas/FADD 途径，至少部分导致 I/R 后的心肌细胞死亡，为保护心脏免受 I/R 损伤提供了新的分子机制和潜在靶点。
