Cap‐independent translation: A shared mechanism for lifespan extension by rapamycin,acarbose, and 17α‐estradiol

We hypothesized that rapamycin (Rapa), acarbose (ACA), which both increase mouse lifespan, and 17α‐estradiol, which increases lifespan in males (17aE2) all share common intracellular signaling pathways with long‐lived Snell dwarf, PAPPA‐KO, and Ghr−/− mice. The long‐lived mutant mice exhibit reduction in mTORC1 activity, declines in cap‐dependent mRNA translation, and increases in cap‐independent translation (CIT). Here, we report that Rapa and ACA prevent age‐related declines in CIT target proteins in both sexes, while 17aE2 has the same effect only in males, suggesting increases in CIT. mTORC1 activity showed the reciprocal pattern, with age‐related increases blocked by Rapa, ACA, and 17aE2 (in males only). METTL3, required for addition of 6‐methyl‐adenosine to mRNA and thus a trigger for CIT, also showed an age‐dependent increase blunted by Rapa, ACA, and 17aE2 (in males). Diminution of mTORC1 activity and increases in CIT‐dependent proteins may represent a shared pathway for both long‐lived‐mutant mice and drug‐induced lifespan extension in mice.