Functional Calsequestrin-1 Is Expressed in the Heart and Its Deficiency Is Causally Related to Malignant Hyperthermia-Like Arrhythmia
Functional Calsequestrin-1 Is Expressed in the Heart and Its Deficiency Is Causally Related to Malignant Hyperthermia-Like Arrhythmia
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DOI：
10.1161/circulationaha.121.053255
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发表时间：
2021-09-07
期刊：
影响因子：
37.8
通讯作者：
Luo，Dali
中科院分区：
文献类型：
--
作者：
Sun，Zhipeng;Wang，Luqi;Luo，Dali
背景Calsequestrins (Casqs) 包含 Casq1 和 Casq2 亚型，分别缓冲 Ca2+ 并调节其在骨骼肌和心肌肌浆网中的释放。与CASQ1或CASQ2突变相关的人类遗传性疾病包括恶性高热/环境中暑（MH/EHS）和儿茶酚胺能多形性室性心动过速。然而，患有 MH/EHS 事件的患者经常会出现心律失常，其潜在机制仍不清楚。 方法分别通过心电图和电图对来自传统 (Casq1-KO) 和心脏特异性 (Casq1-CKO)Casq1 敲除小鼠的工作心脏进行体内和离体监测。 MH由2%异氟烷诱导并用丹曲林腹腔注射处理。延时成像用于监测 Casq1 基因敲低、过度表达或截短的离体小鼠心肌细胞或新生大鼠心室肌细胞的细胞内 Ca2+ 活性。通过交联Western印迹分析确定两个Casqs的构象变化。结果与MH/EHS患者一样，Casq1-KO和Casq1-CKO小鼠在暴露于2%异氟醚后出现基础心率加快和室性心动过速，但可以通过丹曲林缓解。 Casq1-KO 离体心脏中也发生基底窦性心动过速和心室异位电触发。因此，Casq1-CKO 小鼠的心室心肌细胞表现出丹曲林敏感的 Ca2+ 波增加和异氟烷舒张期过早 Ca2+ 瞬态/振荡。 Casq1 敲低的新生大鼠心室肌细胞在异氟醚上增强了自发的 Ca2+ 火花/瞬变，而过表达 Casq1 的细胞表现出减少的 Ca2+ 火花/瞬变，而在 Casq1 C 末端截断 9 个氨基酸的细胞中则不存在这种情况。结构评估表明，大部分 Casq1 蛋白以聚合物形式存在，并与心室肌浆网中的兰尼定受体 2 发生物理相互作用。 Casq1 同种型也在人类心肌中表达。从机制上讲，暴露于 2% 异氟烷或 41°C 加热会诱导小鼠心室和骨骼肌组织中的 Casq1 寡聚化，导致心室中 Casq1/兰尼碱受体 2 相互作用减少，并增加兰尼碱受体 2 活性。 结论 Casq1 在心脏中表达，调节肌浆网 Ca2+ 释放和心率。 Casq1缺陷通过触发诱导的Casq1寡聚化和减轻其对兰尼碱受体2介导的Ca2+释放的抑制作用独立地引起MH/EHS样室性心律失常，从而揭示了一种新的遗传性心律失常和MH/EHS心律失常发生的新机制。
BackgroundCalsequestrins (Casqs), comprising the Casq1 and Casq2 isoforms, buffer Ca2+and regulate its release in the sarcoplasmic reticulum of skeletal and cardiac muscle, respectively. Human inherited diseases associated with mutations inCASQ1orCASQ2include malignant hyperthermia/environmental heat stroke (MH/EHS) and catecholaminergic polymorphic ventricular tachycardia. However, patients with an MH/EHS event often experience arrhythmia for which the underlying mechanism remains unknown.MethodsWorking hearts from conventional (Casq1-KO) and cardiac-specific (Casq1-CKO)Casq1knockout mice were monitored in vivo and ex vivo by ECG and electric mapping, respectively. MH was induced by 2% isoflurane and treated intraperitoneally with dantrolene. Time-lapse imaging was used to monitor intracellular Ca2+activity in isolated mouse cardiomyocytes or neonatal rat ventricular myocytes with knockdown, overexpression, or truncation of theCasq1gene. Conformational change in both Casqs was determined by cross-linking Western blot analysis.ResultsLike patients with MH/EHS,Casq1-KO andCasq1-CKO mice had faster basal heart rate and ventricular tachycardia on exposure to 2% isoflurane, which could be relieved by dantrolene. Basal sinus tachycardia and ventricular ectopic electric triggering also occurred inCasq1-KO hearts ex vivo. Accordingly, the ventricular cardiomyocytes fromCasq1-CKO mice displayed dantrolene-sensitive increased Ca2+waves and diastole premature Ca2+transients/oscillations on isoflurane. Neonatal rat ventricular myocytes with Casq1-knockdown had enhanced spontaneous Ca2+sparks/transients on isoflurane, whereas cells overexpressing Casq1 exhibited decreased Ca2+sparks/transients that were absent in cells with truncation of 9 amino acids at the C terminus of Casq1. Structural evaluation showed that most of the Casq1 protein was present as a polymer and physically interacted with ryanodine receptor-2 in the ventricular sarcoplasmic reticulum. The Casq1 isoform was also expressed in human myocardium. Mechanistically, exposure to 2% isoflurane or heating at 41 °C induced Casq1 oligomerization in mouse ventricular and skeletal muscle tissues, leading to a reduced Casq1/ryanodine receptor-2 interaction and increased ryanodine receptor-2 activity in the ventricle.ConclusionsCasq1 is expressed in the heart, where it regulates sarcoplasmic reticulum Ca2+release and heart rate. Casq1 deficiency independently causes MH/EHS-like ventricular arrhythmia by trigger-induced Casq1 oligomerization and a relief of its inhibitory effect on ryanodine receptor-2–mediated Ca2+release, thus revealing a new inherited arrhythmia and a novel mechanism for MH/EHS arrhythmogenesis.