Rationale: Ischemic heart disease remains a primary threat to human health, while its precise etiopathogenesis is still unclear. TBC domain family member 15 (TBC1D15) is a RAB7 GTPase-activating protein participating in the regulation of mitochondrial dynamics. This study was designed to explore the role of TBC1D15 in acute myocardial infarction (MI)-induced cardiac injury and the possible mechanism(s) involved./nMethods: Mitochondria-lysosome interaction was evaluated using transmission electron microscopy and live cell time-lapse imaging. Mitophagy flux was measured by fluorescence and western blotting. Adult mice were transfected with adenoviral TBC1D15 through intra-myocardium injection prior to a 3-day MI procedure. Cardiac morphology and function were evaluated at the levels of whole-heart, cardiomyocytes, intracellular organelles and cell signaling transduction./nResults: Our results revealed downregulated level of TBC1D15, reduced systolic function, overt infarct area and myocardial interstitial fibrosis, elevated cardiomyocyte apoptosis and mitochondrial damage 3 days after MI. Overexpression of TBC1D15 restored cardiac systolic function, alleviated infarct area and myocardial interstitial fibrosis, reduced cardiomyocyte apoptosis and mitochondrial damage although TBC1D15 itself did not exert any myocardial effect in the absence of MI. Further examination revealed that 3-day MI-induced accumulation of damaged mitochondria was associated with blockade of mitochondrial clearance because of enlarged defective lysosomes and subsequent interrupted mitophagy flux, which were attenuated by TBC1D15 overexpression. Mechanistic studies showed that 3-day MI provoked abnormal mitochondria-lysosome contacts, leading to lysosomal enlargement and subsequently disabled lysosomal clearance of damaged mitochondria. TBC1D15 loosened the abnormal mitochondria-lysosome contacts through both the Fis1 binding and the RAB7 GAPase-activating domain of TBC1D15, as TBC1D15-dependent beneficial responses were reversed by interference with either of these two domains both in vitro and in vivo./nConclusions: Our findings indicated a pivotal role of TBC1D15 in acute MI-induced cardiac anomalies through Fis1/RAB7 regulated mitochondria-lysosome contacts and subsequent lysosome-dependent mitophagy flux activation, which may provide a new target in the clinical treatment of acute MI.

中文翻译：

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TBC1D15 / RAB7调节的线粒体-溶酶体相互作用赋予针对急性心肌梗死所致心脏损伤的心脏保护作用

理由：缺血性心脏病仍然是人类健康的主要威胁，但其确切的病因仍不清楚。TBC域家族成员15（TBC1D15）是一种RAB7 GTPase激活蛋白，参与线粒体动力学的调控。本研究旨在探讨急性心肌梗死（MI）TBC1D15的作用，诱导心肌损伤及其可能的机制（S）involved./n方法：线粒体-溶酶体相互作用进行了评估，使用透射电子显微镜和活细胞延时成像。通过荧光和蛋白质印迹法测量线粒体通量。在3天MI程序之前，通过心肌内注射用腺病毒TBC1D15转染成年小鼠。心脏形态和功能在全心脏，心肌细胞，细胞内细胞器和细胞信号transduction./n的水平进行了评价结果：我们的结果显示MI后3天，TBC1D15的水平下调，收缩功能降低，明显的梗塞面积和心肌间质纤维化，心肌细胞凋亡增加和线粒体损伤。TBC1D15的过表达恢复了心脏的收缩功能，减轻了梗塞面积和心肌间质纤维化，减少了心肌细胞的凋亡和线粒体的损​​害，尽管在没有MI的情况下，TBC1D15本身并未发挥任何心肌作用。进一步检查发现，由于溶酶体的缺陷扩大和随后的线粒体通量中断（被TBC1D15过表达所减弱），MI诱导的3天线粒体积累与线粒体清除受阻有关。机理研究表明，MI持续3天会引起线粒体-溶酶体异常接触，导致溶酶体增大，随后破坏了破坏的线粒体的溶酶体清除率。TBC1D15通过Fis1结合和TBC1D15的RAB7 GAPase激活结构域放松了异常的线粒体-溶酶体接触，因为TBC1D15依赖的有益应答通过干扰这两个结构域中的任何一个而被逆转在体外和体内./n结论：通过FIS1 / RAB7调节线粒体-溶酶体接触和随后的溶酶体依赖性自噬助焊剂活化我们的研究结果表明TBC1D15在急性关键作用MI诱导的心脏异常，其可以提供一个新的目标在急性心肌梗死的临床治疗。