Nuclear Trapping of the Forkhead Transcription Factor FoxO1 via Sirt-dependent Deacetylation Promotes Expression of Glucogenetic Genes

Activation of NAD-dependent deacetylases, or Sirtuins, prolongs life span and mimics the effects of caloric restriction(definition) in yeast. The FoxO subfamily of forkhead transcription factors has been shown to mediate some of the effects of Sirtuins. Here we have shown that Sirtuin activation or hydrogen peroxide treatment overrides the phosphorylation-dependent nuclear exclusion of FoxO1 caused by growth factors and causes nuclear translocation of FoxO1 in hepatocytes. Kinetic measurements of nuclear fluorescence recovery after photobleaching show that FoxO1 is readily diffusible within the nucleus under normal conditions but becomes restricted within a nuclear subdomain following treatment with the prototypical Sirtuin agonist resveratrol or oxidative stress. Expression of FoxO1 target genes is accordingly increased, leading to activation of gluconeogenesis and increased glucose release from hepatocytes. Selective modulation of the FoxO/Sirtuin interaction represents a promising therapeutic modality for metabolic disorders. Activation of NAD-dependent deacetylases, or Sirtuins, prolongs life span and mimics the effects of caloric restriction in yeast. The FoxO subfamily of forkhead transcription factors has been shown to mediate some of the effects of Sirtuins. Here we have shown that Sirtuin activation or hydrogen peroxide treatment overrides the phosphorylation-dependent nuclear exclusion of FoxO1 caused by growth factors and causes nuclear translocation of FoxO1 in hepatocytes. Kinetic measurements of nuclear fluorescence recovery after photobleaching show that FoxO1 is readily diffusible within the nucleus under normal conditions but becomes restricted within a nuclear subdomain following treatment with the prototypical Sirtuin agonist resveratrol or oxidative stress. Expression of FoxO1 target genes is accordingly increased, leading to activation of gluconeogenesis and increased glucose release from hepatocytes. Selective modulation of the FoxO/Sirtuin interaction represents a promising therapeutic modality for metabolic disorders. The long-standing observation that caloric restriction is associated with longevity has led to a widely held theory that metabolism and life span share common cellular pathways (1Wood J.G. Rogina B. Lavu S. Howitz K. Helfand S.L. Tatar M. Sinclair D. Nature. 2004; 430: 686-689Crossref PubMed Scopus (1541) Google Scholar, 2Koubova J. Guarente L. Genes Dev. 2003; 17: 313-321Crossref PubMed Scopus (391) Google Scholar). One such pathway has been proposed to involve forkhead transcription factors of the FoxO subfamily (3Furukawa-Hibi Y. Yoshida-Araki K. Ohta T. Ikeda K. Motoyama N. J. Biol. Chem. 2002; 277: 26729-26732Abstract Full Text Full Text PDF PubMed Scopus (210) Google Scholar, 4van der Horst A. 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The latter causes FoxO acetylation, thus promoting the interaction between FoxO and Sirt1, the mammalian ortholog of Sir2.1 (4van der Horst A. Tertoolen L.G. de Vries-Smits L.M. Frye R.A. Medema R.H. Burgering B.M. J. Biol. Chem. 2004; 279: 28873-28879Abstract Full Text Full Text PDF PubMed Scopus (461) Google Scholar, 5Brunet A. Sweeney L.B. Sturgill J.F. Chua K.F. Greer P.L. Lin Y. Tran H. Ross S.E. Mostoslavsky R. Cohen H.Y. Hu L.S. Cheng H.L. Jedrychowski M.P. Gygi S.P. Sinclair D.A. Alt F.W. Greenberg M.E. Science. 2004; 303: 2011-2015Crossref PubMed Scopus (2570) Google Scholar, 11Motta M.C. Divecha N. Lemieux M. Kamel C. Chen D. Gu W. Bultsma Y. McBurney M. Guarente L. Cell. 2004; 116: 551-563Abstract Full Text Full Text PDF PubMed Scopus (1175) Google Scholar, 12Daitoku H. Hatta M. Matsuzaki H. Aratani S. Ohshima T. Miyagishi M. Nakajima T. Fukamizu A. Proc. Natl. Acad. Sci. U. S. A. 2004; 101: 10042-10047Crossref PubMed Scopus (500) Google Scholar). However, the effect of Sirt1-dependent deacetylation on FoxO function remains somewhat controversial, with most (4van der Horst A. Tertoolen L.G. de Vries-Smits L.M. Frye R.A. Medema R.H. Burgering B.M. J. Biol. Chem. 2004; 279: 28873-28879Abstract Full Text Full Text PDF PubMed Scopus (461) Google Scholar, 5Brunet A. Sweeney L.B. Sturgill J.F. Chua K.F. Greer