Metabolic rewiring of mitochondria in senescence revealed by time-resolved analysis of the mitochondrial proteome

Mitochondrial dysfunction and cellular senescence are hallmarks of aging. However, the relationship between these two phenomena remains incompletely understood. In this study, we investigated the rewiring of mitochondria upon development of the senescent state in human IMR90 fibroblasts. Determining the bioenergetic activities and abundance of mitochondria, we demonstrate that senescent cells accumulate mitochondria with reduced OXPHOS activity, resulting in an overall increase of mitochondrial activities in senescent cells. Time-resolved proteomic analyses revealed extensive reprogramming of the mitochondrial proteome upon senescence development and allowed the identification of metabolic pathways that are rewired with different kinetics upon establishment of the senescent state. Among the early-responding pathways, the degradation of branched-chain amino acid (BCAA) was increased, while the one carbon-folate metabolism was decreased. Late-responding pathways include lipid metabolism and mitochondrial translation. These signatures were confirmed by metabolic tracing experiments, highlighting metabolic rewiring as a central feature of mitochondria in cellular senescence. Together, our data provide an unprecedentedly comprehensive view on the metabolic status of mitochondria in senescent cells and reveal how the mitochondrial proteome adapts to the induction of senescence.