Gong Yingchao, Lu Xue, Wang Xingchen, Wang Yinfang, Shen Zhida, Gao Yun, Zhuang Lenan, Yu Luyang, Chen Jiawen, Li Qinfeng, Qiu Fuyu, Lin Jun, Tao Yuhang, Jiang Chenyang, Fu Guosheng, Zhang Peng, Lai Dongwu
Department of Cardiology, Zhejiang Key Laboratory of Cardiovascular Intervention and Precision Medicine, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China. (Y. Gong, X.L., X.W., Z.S., Y. Gao, L.Z., L.Y., J.C., Q.L., F.Q., J.L., Y.T., C.J., G.F., D.L.).
Central Laboratory, Putuo Hospital, Shanghai University of Traditional Chinese Medicine, China (Y.W., P.Z.).
Circulation. 2025 Jun 30. doi: 10.1161/CIRCULATIONAHA.124.069737.
Pathological cardiac remodeling after myocardial infarction (MI) is a leading cause of heart failure and sudden death. The detailed mechanisms underlying the transition to heart failure after MI are not fully understood. Disruptions in the endoplasmic reticulum (ER)-mitochondria connectivity, along with mitochondrial dysfunction, are substantial contributors to this remodeling process. In this study, we aimed to explore the impact of mitochondrial tumor suppressor 1A (Mtus1A) on cardiac remodeling subsequent to MI and elucidate its regulatory role in ER-mitochondria interactions.
Single-nucleus RNA sequencing analysis was performed to delineate the expression patterns of Mtus1 in human cardiomyocytes under ischemic stress. MI models were induced in mice by left coronary artery ligation and replicated in vitro using primary neonatal rat ventricular myocytes exposed to oxygen glucose deprivation. Cardiac-specific deletion of Mtus1 was achieved by crossing floxed Mtus1 mice with the Myh6-MerCreMer mice. The impact of Mtus1A, a mitochondrial isoform of Mtus1, on cardiac function and the molecular mechanisms were investigated in both in vivo and in vitro settings. Mitochondria-associated ER membranes coupling levels were evaluated by transmission electron microscopy and live-cell imaging. Protein interactions involving Mtus1A were explored through immunoprecipitation-mass spectrometry, coimmunoprecipitation, and proximity ligation assay. The roles of Mtus1A and Fbxo7 (F-box protein 7) were validated in a murine MI model using adeno-associated virus serotype 9 (AAV9).
Bioinformatics analysis revealed a significant downregulation of Mtus1 expression in human cardiomyocytes under ischemic conditions, indicating its potential role in stress response. The predominant isoform in murine cardiomyocytes, Mtus1A, showed reduced expression in the left ventricle of mice after MI, which is consistent with the decreased levels of its orthologs in heart tissues from patients with MI. Cardiac-specific knockout of Mtus1 in mice exacerbated cardiac dysfunction after MI. Both in vitro and in vivo studies demonstrated the vital role of Mtus1A in modulating mitochondria-associated ER membranes coupling and preserving mitochondrial function. Mechanistically, Mtus1A functions as a scaffold protein that maintains the formation of inositol 1,4,5-trisphosphate receptor 1 (IPR1)-glucose-regulated protein 75 (Grp75)-voltage-dependent anion channel 1 (VDAC1) complex through its amino acid sequence 189-219. In addition, Mtus1A protein is stabilized by K6-linked ubiquitination through the E3 ubiquitin ligase Fbxo7. Mtus1A overexpression in mice mitigated MI-induced cardiac dysfunction and remodeling by maintaining ER-mitochondria connectivity.
Our study demonstrates that Mtus1A is crucial for modulating MI-induced cardiac remodeling by preserving ER-mitochondria communication and ameliorating mitochondrial function in cardiomyocytes. Mtus1A may serve as a potential therapeutic target for treating heart failure after MI.
心肌梗死（MI）后病理性心脏重塑是心力衰竭和猝死的主要原因。MI后向心力衰竭转变的详细机制尚未完全阐明。内质网（ER）-线粒体连接中断以及线粒体功能障碍是这一重塑过程的重要促成因素。在本研究中，我们旨在探讨线粒体肿瘤抑制因子1A（Mtus1A）对MI后心脏重塑的影响，并阐明其在ER-线粒体相互作用中的调节作用。
进行单核RNA测序分析以描绘缺血应激下人心肌细胞中Mtus1的表达模式。通过左冠状动脉结扎在小鼠中诱导MI模型，并使用暴露于氧葡萄糖剥夺的原代新生大鼠心室肌细胞在体外进行复制。通过将携带floxed Mtus1的小鼠与Myh6-MerCreMer小鼠杂交来实现心脏特异性敲除Mtus1。在体内和体外环境中研究了Mtus1的线粒体异构体Mtus1A对心脏功能和分子机制的影响。通过透射电子显微镜和活细胞成像评估线粒体相关内质网膜偶联水平。通过免疫沉淀-质谱、共免疫沉淀和邻近连接分析探索涉及Mtus1A的蛋白质相互作用。使用9型腺相关病毒（AAV9）在小鼠MI模型中验证了Mtus1A和Fbxo7（F-box蛋白7）的作用。
生物信息学分析显示缺血条件下人心肌细胞中Mtus1表达显著下调，表明其在应激反应中的潜在作用。小鼠心肌细胞中的主要异构体Mtus1A在MI后小鼠左心室中的表达降低，这与其在MI患者心脏组织中的直系同源物水平降低一致。小鼠中Mtus1的心脏特异性敲除加剧了MI后的心脏功能障碍。体外和体内研究均证明Mtus1A在调节线粒体相关内质网膜偶联和维持线粒体功能方面的重要作用。从机制上讲，Mtus1A作为一种支架蛋白，通过其氨基酸序列189-219维持肌醇1,4,5-三磷酸受体1（IPR1）-葡萄糖调节蛋白75（Grp75）-电压依赖性阴离子通道1（VDAC1）复合物的形成。此外，Mtus1A蛋白通过E3泛素连接酶Fbxo7的K6连接泛素化而稳定。小鼠中Mtus1A的过表达通过维持ER-线粒体连接减轻了MI诱导的心脏功能障碍和重塑。
我们的研究表明，Mtus1A通过维持ER-线粒体通讯和改善心肌细胞线粒体功能，对调节MI诱导的心脏重塑至关重要。Mtus1A可能作为治疗MI后心力衰竭的潜在治疗靶点。
