EAK-7 Controls Development and Life Span by Regulating Nuclear DAF-16/FoxO Activity

Abstract

SUMMARY FoxO transcription factors control development and longevity in diverse species. Although FoxO regulation via changes in its subcellular localization is well established, little is known about how FoxO activity is regulated in the nucleus. Here we show that the conserved C. elegans protein EAK-7 acts in parallel to the serine/threonine kinase AKT-1 to inhibit the FoxO transcription factor DAF-16. Loss of EAK-7 activity promotes diapause and longevity in a DAF-16/FoxO-dependent manner. Whereas akt-1 mutation activates DAF-16/FoxO by promoting its translocation from the cytoplasm to the nucleus, eak-7 mutation increases nuclear DAF-16/FoxO activity without influencing DAF-16/FoxO subcellular localization. Thus, EAK-7 and AKT-1 inhibit DAF-16/FoxO activity via distinct mechanisms. Our results implicate EAK-7 as a FoxO regulator and highlight the biological impact of a new regulatory pathway that governs the activity of nuclear FoxO without altering its subcellular location.

Unexpected Role for Dosage Compensation in the Control of Dauer Arrest, Insulin-Like Signaling, and FoxO Transcription Factor Activity inCaenorhabditis elegans

“…To test this model, we determined the effect of dpy-21 RNAi on the subcellular localization of a functional DAF-16A::GFP fusion protein (Henderson and Johnson 2001b) in daf-16(null);akt-1(null) double-mutant animals (Figures 4B and Figure S2). As previously shown (Zhang et al 2008; Alam et al 2010; Dumas et al 2010), DAF-16A::GFP was nuclear in many akt-1(null) animals cultured on E. coli containing a control RNAi construct. Exposure of animals of the same genotype to dpy-21 RNAi promoted the nuclear export and cytoplasmic retention of DAF-16A::GFP.…”

“…The strong dauer-constitutive phenotype of eak-7;akt-1 double mutants is fully suppressed by daf-16/FoxO loss-of-function mutations (Alam et al 2010). We reasoned that screening for loss-of-function mutations that suppress the dauer-constitutive phenotype of eak-7;akt-1 double mutants might identify genes encoding novel DAF-16/FoxO activators.…”

“…The following mutant alleles were used: daf-9(dh6) and daf-9(k182) (Gerisch et al 2001), eak-7(tm3188) (Alam et al 2010), and sdc-2(y46) (Nusbaum and Meyer 1989). Double, triple, and quadruple mutant animals were constructed by conventional methods.…”

“…EAK-7, which is likely the most downstream component of the EAK pathway, is a conserved protein of unknown function that is expressed in the same tissues as DAF-16/FoxO. Although EAK-7 likely regulates the nuclear pool of DAF-16/FoxO, it is situated at the plasma membrane (Alam et al 2010), suggesting that it controls DAF-16/FoxO activity via unknown intermediary molecules.…”

RNAi Interrogation of Dietary Modulation of Development, Metabolism, Behavior, and Aging in C. elegans

“…While it is generally accepted that mTORC1 shortens lifespan, the role of mTORC2 in lifespan regulation is complex and somewhat controversial (Alam et al, 2010; Mizunuma et al, 2014; Soukas et al, 2009; Tullet et al, 2008; Xiao et al, 2013). Emerging evidence suggests that mTORC2 signaling regulates lifespan in a diet- and perhaps temperature-dependent manner (Mizunuma et al, 2014; Soukas et al, 2009; Xiao et al, 2013).…”