The regulation of mitochondria function and health is a central node in tissue maintenance, ageing as well as the pathogenesis of various diseases. However, the maintenance of an active mitochondrial functional state and its quality control mechanisms remain incompletely understood. By studying mice with a mitochondria-targeted reporter that shifts its fluorescence from “green” to “red” with time (MitoTimer), we found MitoTimer fluorescence spectrum was heavily dependent on the oxidative metabolic state in the skeletal muscle fibers. The mitoproteolytic activity was enhanced in an energy dependent manner, and accelerated the turnover of MitoTimer protein and respiratory chain substrate, responsible for a green predominant MitoTimer fluorescence spectrum under the oxidative conditions. PGC1α, as well as anti-ageing regents promoted enhanced mitoproteolysis. In addition, cells with the green predominant mitochondria exhibited lower levels of MitoSox and protein carbonylation, indicating a favorable redox state. Thus, we identified MitoTimer as a probe for mitoproteolytic activity and found a heightened control of mitoproteolysis in the oxidative metabolic state, providing a framework for understanding the maintenance of active oxidative metabolism while limiting oxidative damages.

中文翻译：

---

线粒体蛋白水解和氧化磷酸化的耦合使得能够通过 MitoTimer 荧光追踪活跃的线粒体状态

线粒体功能和健康的调节是组织维持、衰老以及各种疾病发病机制的中心节点。然而，线粒体活性功能状态的维持及其质量控制机制仍不完全清楚。通过研究带有线粒体靶向报告基因的小鼠（MitoTimer），该报告基因的荧光随时间从“绿色”变为“红色”（MitoTimer），我们发现 MitoTimer 荧光光谱严重依赖于骨骼肌纤维中的氧化代谢状态。线粒体蛋白水解活性以能量依赖性方式增强，并加速 MitoTimer 蛋白和呼吸链底物的周转，导致氧化条件下 MitoTimer 荧光光谱以绿色为主。 PGC1α 以及抗衰老药物可促进线粒体蛋白水解作用的增强。此外，线粒体以绿色为主的细胞表现出较低水平的 MitoSox 和蛋白质羰基化，表明有利的氧化还原状态。因此，我们将 MitoTimer 确定为线粒体蛋白水解活性的探针，并发现氧化代谢状态下线粒体蛋白水解的增强控制，为理解维持活性氧化代谢同时限制氧化损伤提供了框架。