Inhibition of S6K lowers age-related inflammation and immunosenescence and increases lifespan via the endolysosomal system

The nutrient-sensing Target of Rapamycin complex 1 (TORC1) is an evolutionarily conserved regulator of longevity. S6 kinase (S6K) is an essential downstream mediator for the effect of TORC1 on longevity. However, mechanistic insights on how TORC1-S6K signalling promotes lifespan and healthspan are still limited. Here we show that activity of S6K in the Drosophila fat body is essential for rapamycin-mediated longevity. Fat-body-specific activation of S6K blocked lifespan extension upon rapamycin feeding and induced accumulation of multilamellar lysosomal enlargements. Besides, fat body-specific S6K knockdown extended lifespan in files. We performed proteomics for Drosophila fat body to explore the fat body-specific regulation of protein expression by two separate datasets: fat body-specific S6K activation (Lsp2GS>S6KCA) with rapamycin treatment; and fat body-specific S6K inhibition (Lsp2GS>S6KRNAi). To assess if the age-prolonging mechanisms of TORC1-S6K signalling are conserved between flies and mammals, we assessed the impact of rapamycin treatment in the proteome of liver from C3B6F1 mice (F1 hybrids of C3H/HeOuJ females and C57Bl/6N males).