title: RACK1 competes with HSP90 for binding to HIF-1alpha and is required for O(2)-independent and HSP90 inhibitor-induced degradation of HIF-1alpha.
abstract: Hypoxia-inducible factor 1 (HIF-1) regulates transcription in response to changes in O(2) concentration. O(2)-dependent degradation of the HIF-1alpha subunit is mediated by prolyl hydroxylase (PHD), the von Hippel-Lindau (VHL)/Elongin-C/Elongin-B E3 ubiquitin ligase complex, and the proteasome. Inhibition of heat-shock protein 90 (HSP90) leads to O(2)/PHD/VHL-independent degradation of HIF-1alpha. We have identified the receptor of activated protein kinase C (RACK1) as a HIF-1alpha-interacting protein that promotes PHD/VHL-independent proteasomal degradation of HIF-1alpha. RACK1 competes with HSP90 for binding to the PAS-A domain of HIF-1alpha in vitro and in human cells. HIF-1alpha degradation induced by the HSP90 inhibitor 17-allylaminogeldanamycin is abolished by RACK1 loss of function. RACK1 binds to Elongin-C and promotes ubiquitination of HIF-1alpha. Elongin-C-binding sites in RACK1 and VHL show significant sequence similarity. Thus, RACK1 is an essential component of an O(2)/PHD/VHL-independent mechanism for regulating HIF-1alpha stability through competition with HSP90 and recruitment of the Elongin-C/B ubiquitin ligase complex.
authors.affiliation: Vascular Biology Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
authors.forename: Ye V
authors.initials: YV
authors.lastname: Liu
authors.forename: Jin H
authors.initials: JH
authors.lastname: Baek
authors.forename: Huafeng
authors.initials: H
authors.lastname: Zhang
authors.forename: Roberto
authors.initials: R
authors.lastname: Diez
authors.forename: Robert N
authors.initials: RN
authors.lastname: Cole
authors.forename: Gregg L
authors.initials: GL
authors.lastname: Semenza
mesh_terms: D000595:Amino Acid Sequence; D016227:Benzoquinones / Q000494:pharmacology; D001667:Binding, Competitive; D002460:Cell Line; D000075065:Elongin; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D066298:In Vitro Techniques; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D011485:Protein Binding; D040901:Proteomics; D034622:RNA Interference; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D016227:Benzoquinones; C000616396:ELOB protein, human; C000616395:ELOC protein, human; D000075065:Elongin; C497442:HIF1A protein, human; D018841:HSP90 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047029:Lactams, Macrocyclic; D009363:Neoplasm Proteins; C419368:RACK1 protein, human; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D014157:Transcription Factors; C112765:tanespimycin; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D019204:GTP-Binding Proteins; C497446:VHL protein, human; D010100:Oxygen