Nepalia Amrita, Saini Deepak Kumar
Department of Developmental Biology and Genetics, Indian Institute of Science, Bengaluru, 560012, India.
Longevity India Initiative, Indian Institute of Science, Bengaluru, 560012, India.
Adv Biol (Weinh). 2025 Aug;9(8):e2400597. doi: 10.1002/adbi.202400597. Epub 2025 Mar 24.
Mitochondrial dysfunction is an irrefutable hallmark of cellular senescence and aging. The dysfunction is marked by increased mitochondrial volume and reduced function, typified by low Adenosine Triphosphate (ATP) production and higher Reactive Oxygen Species (ROS) generation. Over the years, this dysfunction has been linked to Electron Transport Chain (ETC) malfunction and low NAD levels, augmented by poor mitophagy. However, the genetic regulation of mitochondrial dysfunction is still not clear. Here, using several senescence models, the first report on the role of the downregulation of a mitochondrial protein, Translocase of Inner Mitochondrial Membrane 50 (TIMM50), in senescence is presented. The downregulation of TIMM50 is also sufficient for triggering senescence through impaired mitochondrial function, characterized using a variety of mitochondrial function assessment assays. Reduced levels of TIMM50 initiated all the hallmarks of senescence, and overexpression significantly slowed senescence onset in response to an external trigger. The pathway analysis revealed that TIMM50 loss is mediated by the sirtuin1-dependent downregulation of CCAAT enhancer binding protein alpha (CEBPα), a transcription activator for TIMM50 expression. To establish the translational value of the observation, screening several potential anti-aging compounds revealed TIMM50 stabilizing and senescence-delaying effects only for verapamil and mitochondrial ROS quencher, Mito (2-(2,2,6,6-Tetramethylpiperidin-1-oxyl-4-ylamino)-2-oxoethyl)triphenylphosphonium chloride (MitoTEMPO), both known anti-aging entities. Overall, TIMM50 is identified as the key mitochondrial protein whose downregulation is a critical step in initiating cellular senescence.
线粒体功能障碍是细胞衰老和机体老化的一个无可争议的标志。这种功能障碍的特征是线粒体体积增大和功能减退，表现为三磷酸腺苷（ATP）生成减少和活性氧（ROS）生成增加。多年来，这种功能障碍一直与电子传递链（ETC）功能异常和烟酰胺腺嘌呤二核苷酸（NAD）水平降低有关，线粒体自噬功能不佳进一步加剧了这种情况。然而，线粒体功能障碍的基因调控仍不清楚。在此，利用多种衰老模型，首次报道了线粒体蛋白内膜转位酶50（TIMM50）下调在衰老中的作用。TIMM50的下调也足以通过线粒体功能受损引发衰老，这是通过多种线粒体功能评估试验来表征的。TIMM50水平降低引发了衰老的所有特征，而过表达则显著延缓了外部触发因素引起的衰老进程。通路分析表明，TIMM50的缺失是由依赖沉默调节蛋白1的CCAAT增强子结合蛋白α（CEBPα）下调介导的，CEBPα是TIMM50表达的转录激活因子。为了确定这一观察结果的转化价值，对几种潜在的抗衰老化合物进行筛选后发现，只有维拉帕米和线粒体ROS淬灭剂Mito（2-(2,2,6,6-四甲基哌啶-1-氧基-4-基氨基)-2-氧代乙基）三苯基氯化鏻（MitoTEMPO）具有稳定TIMM50和延缓衰老的作用，这两种都是已知的抗衰老物质。总体而言，TIMM50被确定为关键的线粒体蛋白，其下调是启动细胞衰老的关键步骤。
