Oxidative stress causes a reversible decrease of deubiquitylases activity in old vertebrate brains

Abstract

Abstract The ubiquitin–proteasome system is essential for neuronal proteostasis, yet its function declines with age. How aging affects deubiquitylating enzymes (DUBs) in the vertebrate brain remains unclear. Here we used activity-based proteomics to profile cysteine protease DUBs in aging mouse and killifish brains. We identified a subset of DUBs that progressively lose catalytic activity with age despite stable protein abundance. Mechanistically, oxidative stress impaired DUB function through thiol oxidation, whereas antioxidant treatment with N-acetylcysteine ethyl ester (NACET) restored activity in aging brains. In human iPSC-derived neurons, global DUB inhibition and targeted inhibition of USP7, one of the most strongly age-affected DUBs, partially recapitulated ubiquitylation changes observed in aged brains. Temporal analysis in mice further revealed that DUB inhibition precedes proteasome decline during brain aging. Together, these findings identify redox-sensitive DUBs that lose activity with age and suggest impaired deubiquitylation as an early, potentially reversible driver of proteostasis decline in the aging brain.