BACKGROUND Cardiac hypertrophy compensates for increased biomechanical stress of the heart induced by prevalent cardiovascular pathologies but can result in heart failure if left untreated. Here, we hypothesized that the membrane fusion and repair protein dysferlin is critical for the integrity of the transverse-axial tubule (TAT) network inside cardiomyocytes and contributes to the proliferation of TAT endomembranes during pressure overload-induced cardiac hypertrophy. METHODS Stimulated emission depletion and electron microscopy were used to localize dysferlin in mouse and human cardiomyocytes. Data-independent acquisition mass spectrometry revealed the cardiac dysferlin interactome and proteomic changes of the heart in dysferlin-knockout mice. After transverse aortic constriction, we compared the hypertrophic response of wild-type versus dysferlin-knockout hearts and studied TAT network remodeling mechanisms inside cardiomyocytes by live-cell membrane imaging. RESULTS We localized dysferlin in a vesicular compartment in nanometric proximity to contact sites of the TAT network with the sarcoplasmic reticulum, a.k.a. junctional complexes for Ca2+-induced Ca2+ release. Interactome analyses demonstrated a novel protein interaction of dysferlin with the membrane-tethering sarcoplasmic reticulum protein juncophilin-2, a putative interactor of L-type Ca2+ channels and ryanodine receptor Ca2+ release channels in junctional complexes. Although the dysferlin-knockout caused a mild progressive phenotype of dilated cardiomyopathy, global proteome analysis revealed changes preceding systolic failure. Following transverse aortic constriction, dysferlin protein expression was significantly increased in hypertrophied wild-type myocardium, while dysferlin-knockout animals presented markedly reduced left-ventricular hypertrophy. Live-cell membrane imaging showed a profound reorganization of the TAT network in wild-type left-ventricular myocytes after transverse aortic constriction with robust proliferation of axial tubules, which critically depended on the increased expression of dysferlin within newly emerging tubule components. CONCLUSIONS Dysferlin represents a new molecular target in cardiac disease that protects the integrity of tubule-sarcoplasmic reticulum junctional complexes for regulated excitation-contraction coupling and controls TAT network reorganization and tubular membrane proliferation in cardiomyocyte hypertrophy induced by pressure overload.

中文翻译：

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Dysferlin 促进心脏肥大中的管状膜增殖。


背景技术心脏肥大补偿了由普遍的心血管病理引起的心脏生物力学应力的增加，但如果不及时治疗可能导致心力衰竭。在这里，我们假设膜融合和修复蛋白 Dysferlin 对于心肌细胞内横轴小管 (TAT) 网络的完整性至关重要，并有助于压力超负荷引起的心脏肥大期间 TAT 内膜的增殖。方法使用受激发射损耗和电子显微镜来定位小鼠和人类心肌细胞中的dysferlin。数据独立的采集质谱分析揭示了 Dysferlin 敲除小鼠心脏的 Dysferlin 相互作用组和蛋白质组变化。主动脉横缩后，我们比较了野生型心脏与 Dysferlin 敲除心脏的肥大反应，并通过活细胞膜成像研究了心肌细胞内的 TAT 网络重塑机制。结果我们将 Dysferlin 定位在囊泡区室中，以纳米级接近 TAT 网络与肌浆网的接触位点，即 Ca2+ 诱导 Ca2+ 释放的连接复合物。相互作用组分析表明，dysferlin 与膜束缚肌浆网蛋白 juncophilin-2 存在一种新型蛋白质相互作用，juncophilin-2 是连接复合物中 L 型 Ca2+ 通道和兰尼碱受体 Ca2+ 释放通道的假定相互作用物。尽管 Dysferlin 敲除导致了扩张型心肌病的轻度进行性表型，但整体蛋白质组分析揭示了收缩衰竭之前的变化。 主动脉横缩后，肥厚的野生型心肌中 Dysferlin 蛋白表达显着增加，而 Dysferlin 敲除动物的左心室肥厚显着减少。活细胞膜成像显示，在横主动脉缩窄后，野生型左心室肌细胞中的 TAT 网络发生了深刻的重组，轴管强劲增殖，这在很大程度上取决于新出现的小管成分中 Dysferlin 表达的增加。结论 Dysferlin 代表了心脏病的一个新分子靶点，它可以保护小管-肌浆网连接复合物的完整性，调节兴奋-收缩耦合，并控制压力超负荷引起的心肌细胞肥大中的 TAT 网络重组和管状膜增殖。