A Forkhead/winged helix-related transcription factor mediates insulin-increased plasminogen activator inhibitor-1 gene transcription.
Plasminogen activator inhibitor-1 (PAI-1) is an important regulator of fibrinolysis by its inhibition of both tissue-type and urokinase plasminogen activators. PAI-1 levels are elevated in type II diabetes and this elevation correlates with macro- and microvascular complications of diabetes. Insulin increases PAI-1 production in several experimental systems, but the mechanism of insulin-activated PAI-1 transcription remains to be determined. Deletion analysis of the PAI-1 promoter revealed that the insulin response element is between -117 and -7. Mutation of the AT-rich site at -52/-45 abolished the insulin responsiveness of the PAI-1 promoter. This sequence is similar to the inhibitory sequence found in the phosphoenolpyruvate carboxylkinase/insulin-like growth factor-I-binding protein I promoters. Gel-mobility shift assays demonstrated that the forkhead bound to the PAI-1 promoter insulin response element. Expression of the DNA-binding domain of FKHR acted as a dominant negative to block insulin-increased PAI-1-CAT expression. A LexA-FKHR construct was also insulin responsive. These data suggested that a member of the Forkhead/winged helix family of transcription factors mediated the effect of insulin on PAI-1 transcription. Inhibition of phosphatidylinositol 3-kinase reduced the effect of insulin on PAI-1 gene expression, a result consistent with activation through FKHR. However, it was likely that a different member of the FKHR family (not FKHR) mediated this effect since FKHR was present in both insulin-responsive and non-responsive cell lines.
Vulin
Anthony Igor
AI
Department of Pharmacology, New York University School of Medicine, New York, New York 10016, USA.
Stanley
Frederick M
FM
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D051858:Forkhead Transcription Factors; D006801:Humans; D007328:Insulin / Q000502:physiology*; D008156:Luciferases / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000502:physiology*
D017931:DNA Primers; D051858:Forkhead Transcription Factors; D007328:Insulin; D009687:Nuclear Proteins; D017395:Plasminogen Activator Inhibitor 1; D014157:Transcription Factors; D008156:Luciferases