USP-48 enables insulin-mediated longevity and modulates the mitochondrial stress response

The mitochondrial prohibitin (PHB) complex is essential for mitochondrial homeostasis, yet its depletion produces opposite effects on lifespan: shortening it in wild-type C. elegans but extending it in insulin/IGF-1 receptor daf-2 mutants, which show an attenuated mitochondrial unfolded protein response (UPR^mt). To identify regulators of this differential stress response and its role in aging, we conducted the first genome-wide double-RNAi screen in C. elegans. We identify the ubiquitin-specific peptidase USP-48 as a modulator of the UPR^mt, specially required for lifespan extension under reduced insulin signaling. USP-48 influences mitochondrial structure and function and cooperates with the transcription factor DVE-1 to regulate the UPR^mt largely independent of activating transcription factor associated with stress-1 (ATFS-1). Tissue-specific analysis shows that USP-48 is required for lifespan primarily in the hypodermis, with a smaller germline contribution, but is dispensable in muscle and intestine. Mechanistically, USP-48 promotes histone H2B deubiquitination to shape stress-responsive transcription, revealing ubiquitination as a key determinant of metabolism-dependent longevity.