Department of Cardiovascular Medicine, National Clinical Research Center for Child Health and Disorders, Ministry of Education Key Laboratory of Child Development and Disorders, China International Science and Technology Cooperation Base of Child Development and Critical Disorders, Chongqing Key Laboratory of Pediatrics, Children's Hospital of Chongqing Medical University, Chongqing, P.R. China.
Department of Medicine, Center for Precision Medicine, University of Missouri School of Medicine, Columbia, Missouri, USA.
DNA Cell Biol. 2021 Feb;40(2):184-191. doi: 10.1089/dna.2020.5828. Epub 2021 Jan 18.
Malfunction of myocardial mitochondria plays a crucial role in the development of cardiovascular disorders, especially hypertrophic and dilated cardiomyopathies. Cardiac troponin I (cTnI) is an important structural protein and essential to contraction and relaxation of cardiomyocytes. Recent studies suggest that mutated cTnIR193H could function as a regulatory molecule for other cell functions. This study was to determine whether mutated cTnI could contribute to mitochondrial dysfunction of cardiomyocytes. Primary cardiomyocytes were transfected with cTnIR193H adenovirus with empty vector as control. Mitochondrial structure and function were evaluated in the cells 72 h after transfection. Transmission electron microscopy examination showed mitochondria in the cardiomyocytes with R193H mutation displayed broken cristae, vacuolation, and mitophagy. Mitochondrial function studies revealed a significant decrease in complex I activity, ATP and reactive oxygen species levels, and oxygen consumption rate compared with controls. Western blot analysis demonstrated that expressions of mitochondria-related genes, including ND5 (ubiquinone oxidoreductase chain 5), LRPPRC (a leucine-rich protein of pentatricopeptide repeat family), and PGC-1α (PPARG co-activator 1 alpha), were significantly downregulated in R193H mutation cardiomyocytes compared with the control. Swelling and broken cristae were observed in the mitochondria of cardiomyocytes from cTnIR193H mutation transgenic mice with decreased mitochondrial function, not from the littermate control mice. The data from the present study demonstrated that mitochondrial structure and function were significantly impaired in cardiomyocytes with cTnIR193H mutation, suggesting that cTnI might be critically involved in maintaining the structural and functional integrity of myocardial mitochondria.
心肌线粒体功能障碍在心血管疾病的发展中起着关键作用，特别是在肥厚型和扩张型心肌病中。心肌肌钙蛋白 I（cTnI）是一种重要的结构蛋白，对心肌细胞的收缩和舒张至关重要。最近的研究表明，突变型 cTnIR193H 可以作为其他细胞功能的调节分子。本研究旨在确定突变型 cTnI 是否有助于心肌细胞线粒体功能障碍。用空载体作为对照，将携带 cTnIR193H 腺病毒的载体转染到原代心肌细胞中。转染后 72 小时评估细胞中线粒体的结构和功能。透射电子显微镜检查显示，携带 R193H 突变的心肌细胞中的线粒体显示出嵴断裂、空泡化和线粒体自噬。线粒体功能研究显示，与对照组相比，复合物 I 活性、ATP 和活性氧水平以及耗氧量显著降低。Western blot 分析表明，与对照组相比，携带 R193H 突变的心肌细胞中线粒体相关基因的表达，包括 ND5（泛醌氧化还原酶链 5）、LRPPRC（五肽重复家族富含亮氨酸的蛋白）和 PGC-1α（PPARG 共激活因子 1α），显著下调。携带 cTnIR193H 突变的转基因小鼠心肌细胞的线粒体出现肿胀和嵴断裂，线粒体功能下降，而其同窝对照小鼠的线粒体则没有这种情况。本研究的数据表明，携带 cTnIR193H 突变的心肌细胞中线粒体的结构和功能明显受损，提示 cTnI 可能在维持心肌线粒体的结构和功能完整性方面起着关键作用。
