title: The LXXLL motif of murine forkhead transcription factor FoxO1 mediates Sirt1-dependent transcriptional activity.
abstract: The forkhead transcription factor FoxO1 has been identified as a negative regulator of insulin/IGF-1 signaling. Its function is inhibited by phosphorylation and nuclear exclusion through a PI3K-dependent pathway. However, the structure/function relationship of FoxO1 has not been elucidated completely. In this study, we carried out mutation analysis of the FoxO1 coactivator-interacting LXXLL motif (amino acids 459-463). Expression of a 3A/LXXAA mutant, in which 3 Akt phosphorylation sites (T24, S253, and S316) and 2 leucine residues in the LXXLL motif (L462 and L463) were replaced by alanine, decreased both Igfbp-1 and G6Pase promoter activity and endogenous Igfbp-1 and G6Pase gene expression in simian virus 40-transformed (SV40-transformed) hepatocytes. Importantly, mutagenesis of the LXXLL motif eliminated FoxO1 interaction with the nicotinamide adenine dinucleotide-dependent (NAD-dependent) deacetylase sirtuin 1 (Sirt1), sustained the acetylated state of FoxO1, and made FoxO1 nicotinamide and resveratrol insensitive, supporting a role for this motif in Sirt1 binding. Furthermore, intravenous administration of adenovirus encoding 3A/LXXAA FoxO1 into Lepr db/db mice decreased fasting blood glucose levels and improved glucose tolerance and was accompanied by reduced G6Pase and Igfbp-1 gene expression and increased hepatic glycogen content. In conclusion, the LXXLL motif of FoxO1 may have an important role for its transcriptional activity and Sirt1 binding and should be a target site for regulation of gene expression of FoxO1 target genes and glucose metabolism in vivo.
authors.affiliation: Department of Clinical Molecular Medicine, Division of Diabetes, Digestive and Kidney Disease, Kobe University Graduate School of Medicine, Kobe, Japan. nakaej@med.kobe-u.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Nakae
authors.forename: Yongheng
authors.initials: Y
authors.lastname: Cao
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Daitoku
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Fukamizu
authors.forename: Wataru
authors.initials: W
authors.lastname: Ogawa
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Yano
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Hayashi
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics; D017124:Conserved Sequence; D003907:Dexamethasone / Q000494:pharmacology; D004331:Drosophila melanogaster / Q000235:genetics; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000502:physiology; D020738:Leptin / Q000235:genetics; D051379:Mice; D016296:Mutagenesis; D011994:Recombinant Proteins / Q000378:metabolism; D056564:Sirtuin 1; D037761:Sirtuins / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D007328:Insulin; D020738:Leptin; D011994:Recombinant Proteins; D003907:Dexamethasone; C470545:Sirt1 protein, mouse; D056564:Sirtuin 1; D037761:Sirtuins; D015056:1-Methyl-3-isobutylxanthine