title: Transforming growth factor beta1 induces hypoxia-inducible factor-1 stabilization through selective inhibition of PHD2 expression.
abstract: The hypoxia-inducible transcription factor-1 (HIF-1) is central to a number of pathological processes through the induction of specific genes such as vascular endothelial growth factor (VEGF). Even though HIF-1 is highly regulated by cellular oxygen levels, other elements of the inflammatory and tumor microenvironment were shown to influence its activity under normal oxygen concentration. Among others, recent studies indicated that transforming growth factor (TGF) beta increases the expression of the regulatory HIF-1alpha subunit, and induces HIF-1 DNA binding activity. Here, we demonstrate that TGFbeta acts on HIF-1alpha accumulation and activity by increasing HIF-1alpha protein stability. In particular, we demonstrate that TGFbeta markedly and specifically decreases both mRNA and protein levels of a HIF-1alpha-associated prolyl hydroxylase (PHD), PHD2, through the Smad signaling pathway. As a consequence, the degradation of HIF-1alpha was inhibited as determined by impaired degradation of a reporter protein containing the HIF-1alpha oxygen-dependent degradation domain encompassing the PHD-targeted prolines. Moreover, inhibition of the TGFbeta1 converting enzyme, furin, resulted in increased PHD2 expression, and decreased basal HIF-1alpha and VEGF levels, suggesting that endogenous production of bioactive TGFbeta1 efficiently regulates HIF-1-targeted genes. This was reinforced by results from HIF-1alpha knock-out or HIF-1alpha-inhibited cells that show impairment in VEGF production in response to TGFbeta. This study reveals a novel mechanism by which a growth factor controls HIF-1 stability, and thereby drives the expression of specific genes, through the regulation of PHD2 levels.
authors.affiliation: Immunology Division, Faculty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: McMahon
authors.forename: Martine
authors.initials: M
authors.lastname: Charbonneau
authors.forename: Sebastien
authors.initials: S
authors.lastname: Grandmont
authors.forename: Darren E
authors.initials: DE
authors.lastname: Richard
authors.forename: Claire M
authors.initials: CM
authors.lastname: Dubois
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D045683:Furin / Q000037:antagonists & inhibitors; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D006900:Hydroxylation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D007249:Inflammation / Q000235:genetics / Q000378:metabolism; D051379:Mice; D011393:Procollagen-Proline Dioxygenase / Q000037:antagonists & inhibitors*; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D051785:Smad Proteins / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011994:Recombinant Proteins; D051785:Smad Proteins; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D042461:Vascular Endothelial Growth Factor A; C490190:EGLN1 protein, human; D011393:Procollagen-Proline Dioxygenase; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D045683:Furin