title: FoxO1 negatively regulates leptin-induced POMC transcription through its direct interaction with STAT3.
abstract: FoxO1, which is up-regulated during early stages of diet-induced leptin resistance, directly interacts with STAT3 and prevents STAT3 from binding to specificity protein 1 (SP1)-pro-opiomelanocortin (POMC) promoter complex, and thereby inhibits STAT3-mediated regulation of POMC transcription. FoxO1 also binds directly to the POMC promoter and negatively regulates its transcription. The present study aims to understand the relative contribution of the two interactions in regulating POMC expression. We studied the structural requirement of FoxO1 for its interaction with STAT3 and POMC promoter, and tested the inhibitory action of FoxO1 mutants by using biochemical assays, molecular biology and computer modelling. FoxO1 mutant with deletion of residues Ala137-Leu160 failed to bind to STAT3 or inhibit STAT3-mediated POMC activation, although its binding to the POMC promoter was unaffected. Further analysis mapped Gly140-Leu160 to be critical for STAT3 binding. The identified region Gly140-Leu160 was conserved among mammalian FoxO1 proteins, and showed a high degree of sequence identity with FoxO3, but not FoxO4. Consistently, FoxO3 could interact with STAT3 and inhibit POMC promoter activity, whereas FoxO4 could not bind to STAT3 or affect POMC promoter activity. We further identified that five residues (Gln145, Arg147, Lys148, Arg153 and Arg154) in FoxO1 were necessary in FoxO1-STAT3 interaction, and mutation of these residues abolished its interaction with STAT3 and inhibition of POMC promoter activity. Finally, a FoxO1-STAT3 interaction interface model generated by computational docking simulations confirmed that the identified residues of FoxO1 were in close proximity to STAT3. These results show that FoxO1 inhibits STAT3-mediated leptin signalling through direct interaction with STAT3.
authors.affiliation: *Singapore Bioimaging Consortium, Singapore 138667, Republic of Singapore.
authors.forename: Wei
authors.initials: W
authors.lastname: Ma
authors.affiliation: †Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), Singapore 138671, Republic of Singapore.
authors.forename: Gloria
authors.initials: G
authors.lastname: Fuentes
authors.affiliation: *Singapore Bioimaging Consortium, Singapore 138667, Republic of Singapore.
authors.forename: Xiaohe
authors.initials: X
authors.lastname: Shi
authors.affiliation: †Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), Singapore 138671, Republic of Singapore.
authors.forename: Chandra
authors.initials: C
authors.lastname: Verma
authors.affiliation: *Singapore Bioimaging Consortium, Singapore 138667, Republic of Singapore.
authors.forename: George K
authors.initials: GK
authors.lastname: Radda
authors.affiliation: *Singapore Bioimaging Consortium, Singapore 138667, Republic of Singapore.
authors.forename: Weiping
authors.initials: W
authors.lastname: Han
mesh_terms: D000818:Animals; D017124:Conserved Sequence; D015536:Down-Regulation; D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D020738:Leptin / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D062105:Molecular Docking Simulation; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011333:Pro-Opiomelanocortin / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D054411:Receptors, Leptin / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D000071161:Forkhead Box Protein O1; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C474033:FoxO3 protein, mouse; C467200:Foxo1 protein, mouse; C515448:LEPR protein, human; D020738:Leptin; D050505:Mutant Proteins; D010446:Peptide Fragments; D054411:Receptors, Leptin; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D011333:Pro-Opiomelanocortin