The Target of Rapamycin Pathway Antagonizes pha-4/FoxA to Control Development and Aging

Abstract

SUMMARY BACKGROUND FoxA factors are critical regulators of embryonic development and post-embryonic life, but little is know about the upstream pathways that modulate their activity [1]. C. elegans pha-4 encodes a FoxA transcription factor that is required to establish the foregut in embryos, and to control growth and longevity after birth [2–5]. We previously identified the AAA+ ATPase homologue ruvb-1 as a potent suppressor of pha-4 mutations [6]. RESULTS Here we show that ruvb-1 is a component of the TOR pathway in C. elegans (CeTOR). Both ruvb-1 and let-363/TOR control nucleolar size and promote localization of box C/D snoRNPs to nucleoli, suggesting a role in rRNA maturation. Inactivation of let-363/TOR or ruvb-1 suppresses the lethality associated with reduced pha-4 activity. The CeTOR pathway controls protein homeostasis and also contributes to adult longevity [7, 8]. We find that pha-4 is required to extend adult lifespan in response to reduced CeTOR signaling. Mutations in the predicted CeTOR target rsks-1/S6 kinase or in ife-2/eIF4E also reduce protein biosynthesis and extend lifespan [9–11], but only rsks-1 mutations require pha-4 for adult longevity. In addition, rsks-1, but not ife-2, can suppress the larval lethality associated with pha-4 loss-of-function mutations. CONCLUSION The data suggest that pha-4 and the CeTOR pathway antagonize one another to regulate post-embryonic development and adult longevity. We suggest a model in which nutrients promote TOR and S6 kinase signaling, which represses pha-4/FoxA, leading to a shorter lifespan. A similar regulatory hierarchy may function in other animals to modulate metabolism, longevity or disease.