title: JNK1 mediates degradation HIF-1alpha by a VHL-independent mechanism that involves the chaperones Hsp90/Hsp70.
abstract: Hypoxia-inducible factor-1alpha (HIF-1alpha) is a master transcription factor that is critical for the regulation of a variety of cellular functions. HIF-1alpha is rapidly degraded under normoxic conditions by ubiquitin-mediated proteasome pathway controlled by the tumor suppressor von Hippel Lindau (VHL). Several recent studies reveal that heat-shock proteins (Hsp) can regulate HIF-1alpha protein degradation by a VHL-independent pathway. Here, we demonstrate that the stress kinase c-Jun NH(2)-terminal kinase 1 (JNK1) is required for Hsp-dependent regulation of HIF-1alpha. Stabilization of HIF-1alpha was impaired in JNK1-/- cells but could be rescued by JNK1 reconstitution under hypoxic conditions. These effects could be phenocopied in other cell settings by JNK1 silencing. Accordingly, HIF-1 transcriptional activity and target gene expression were dramatically reduced in JNK1-/- cells. Further, decreased levels of endogenous Hsp90/Hsp70 proteins in JNK1-/- cells affected the protective roles of these chaperones in stabilizing newly synthesized HIF-1alpha, whereas enforced expression of Hsp90/Hsp70 in JNK1-/- cells increased HIF-1alpha stability relative to parental control cells. Furthering this connection, we also found that defective expression of the Hsp90 acetyltransferase HDAC6 in JNK1-/- cells was associated with reduced Hsp90 chaperone activity. Taken together, our studies define a novel function for JNK1 in regulating HIF-1alpha turnover by a VHL-independent mechanism.
authors.affiliation: Nelson Institute of Environmental Medicine, New York University School of Medicine, Tuxedo, New York 10987, USA.
authors.forename: Dongyun
authors.initials: D
authors.lastname: Zhang
authors.forename: Jingxia
authors.initials: J
authors.lastname: Li
authors.forename: Max
authors.initials: M
authors.lastname: Costa
authors.forename: Jimin
authors.initials: J
authors.lastname: Gao
authors.forename: Chuanshu
authors.initials: C
authors.lastname: Huang
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000633:toxicity; D015687:Cell Hypoxia / Q000502:physiology; D045744:Cell Line, Tumor; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006367:HeLa Cells; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases / Q000096:biosynthesis; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics / Q000378:metabolism*; D009532:Nickel / Q000633:toxicity; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D015533:Transcriptional Activation; D014162:Transfection; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism
chemical_list: D002273:Carcinogens; C497442:HIF1A protein, human; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D009532:Nickel; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D048055:Mitogen-Activated Protein Kinase 8; C433811:HDAC6 protein, human; D000073864:Histone Deacetylase 6; D006655:Histone Deacetylases; C497446:VHL protein, human