title: Insulin regulates hypoxia-inducible factor-1α transcription by reactive oxygen species sensitive activation of Sp1 in 3T3-L1 preadipocyte.
abstract: Oxygen sensing transcription factor HIF-1 is activated due to accumulation of regulatory subunit HIF-1α by posttranslational stability mechanism during hypoxia or by several other stimuli even in normoxia. HIF-1α is also regulated by NF-kB mediated transcription mechanism. Reactive oxygen species (ROS) act as an important regulator of HIF-1 either by affecting prolyl hydroxylase activity, the critical determinant of HIF-1α stabilization or by activating NF-kB to promote HIF-1α transcription. Insulin is known to activate HIF-1 by a ROS dependent mechanism but the molecular mechanism of HIF-1α regulation is not known so far. Here we show that insulin regulates HIF-1α by a novel transcriptional mechanism by a ROS-sensitive activation of Sp1 in 3T3-L1 preadipocyte. Insulin shows little effect on HIF-1α protein stability, but increases HIF-1α promoter activity. Mutation analyses, electrophoretic mobility shift assay and chromatin immunoprecipitation assay confirm the role of Sp1 in HIF-1α transcription. We further demonstrate that insulin-induced ROS generation initiates signaling pathway involving phosphatidylinositol 3-kinase and protein kinase C for Sp1 mediated HIF-1α transcription. In summary, we reveal that insulin regulates HIF-1α by a novel transcriptional mechanism involving Sp1.
authors.affiliation: Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, India.
authors.forename: Sudipta
authors.initials: S
authors.lastname: Biswas
authors.forename: Reshmi
authors.initials: R
authors.lastname: Mukherjee
authors.forename: Nisha
authors.initials: N
authors.lastname: Tapryal
authors.forename: Amit K
authors.initials: AK
authors.lastname: Singh
authors.forename: Chinmay K
authors.initials: CK
authors.lastname: Mukhopadhyay
mesh_terms: D041721:3T3-L1 Cells; D024506:5' Flanking Region; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D005786:Gene Expression Regulation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology*; D051379:Mice; D009154:Mutation; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D055550:Protein Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020218:Response Elements; D017384:Sequence Deletion; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007328:Insulin; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D016329:Sp1 Transcription Factor; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C