Insulin stimulates hypoxia-inducible factor 1 through a phosphatidylinositol 3-kinase/target of rapamycin-dependent signaling pathway.
Hypoxia-inducible factor 1 (HIF-1) is a transcription factor involved in normal mammalian development and in the pathogenesis of several disease states. It consists of two subunits, HIF-1alpha, which is degraded during normoxia, and HIF-1beta, which is constitutively expressed. Activated HIF-1 induces the expression of genes involved in angiogenesis, erythropoiesis, and glucose metabolism. We have previously reported that insulin stimulates vascular endothelial growth factor (VEGF) expression (). In this study, we show that insulin activates HIF-1, leading to VEGF expression in retinal epithelial cells. Insulin activates HIF-1alpha protein expression in a dose-dependent manner with a maximum reached within 6 h. The expression of HIF-1alpha is correlated with the activation of HIF-1 DNA binding activity and the transactivation of a HIF-1-dependent reporter gene. Insulin does not appear to affect HIF-1alpha mRNA transcription but regulates HIF-1alpha protein expression through a translation-dependent pathway. The expression of an active form of protein kinase B and treatment of cells with specific inhibitors of phosphatidylinositol 3-kinase (PI3K), MAPK, and target of rapamycin (TOR) show that mainly PI3K and to a lesser extent TOR are required for insulin-induced HIF-1alpha expression. HIF-1 activity and VEGF expression are also dependent on PI3K- and TOR-dependent signaling. In conclusion, we show here that insulin regulates HIF-1 action through a PI3K/TOR-dependent pathway, resulting in increased VEGF expression.
Treins
Caroline
C
INSERM U145, Institut Fédératif de Recherche 50, Faculté de Médecine, Avenue de Valombrose, 06107 Nice Cedex 2, France.
Giorgetti-Peraldi
Sophie
S
Murdaca
Joseph
J
Semenza
Gregg L
GL
Van Obberghen
Emmanuel
E
D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007328:Insulin / Q000494:pharmacology*; D007700:Kinetics; D008222:Lymphokines / Q000235:genetics*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010857:Pigment Epithelium of Eye; D010957:Plasmids; D014176:Protein Biosynthesis / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D020123:Sirolimus / Q000494:pharmacology*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D003035:Cobalt; D004268:DNA-Binding Proteins; D016228:Endothelial Growth Factors; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007328:Insulin; D008222:Lymphokines; D020928:Mitogen-Activated Protein Kinases; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020123:Sirolimus; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C018021:cobaltous chloride