title: Cobalt chloride-induced estrogen receptor alpha down-regulation involves hypoxia-inducible factor-1alpha in MCF-7 human breast cancer cells.
abstract: The estrogen receptor (ER) is down-regulated under hypoxia via a proteasome-dependent pathway. We studied the mechanism of ERalpha degradation under hypoxic mimetic conditions. Cobalt chloride-induced ERalpha down-regulation was dependent on the expression of newly synthesized protein(s), one possibility of which was hypoxia-inducible factor-1alpha (HIF-1alpha). To examine the role of HIF-1alpha expression in ERalpha down-regulation under hypoxic-mimetic conditions, we used a constitutively active form of HIF-1alpha, HIF-1alpha/herpes simplex viral protein 16 (VP16), constructed by replacing the transactivation domain of HIF-1alpha with that of VP16. Western blot analysis revealed that HIF-1alpha/VP16 down-regulated ERalpha in a dose-dependent manner via a proteasome-dependent pathway. The kinase pathway inhibitors PD98059, U0126, wortmannin, and SB203580 did not affect the down-regulation. A mammalian two-hybrid screen and immunoprecipitation assays indicated that ERalpha interacted with HIF-1alpha physically. These results suggest that ERalpha down-regulation under hypoxia involves protein-protein interactions between the ERalpha and HIF-1alpha.
authors.affiliation: College of Life Science, Institute of Biotechnology, Department of Bioscience and Biotechnology, Sejong University, Kwang-Jin-Gu, Seoul 143-747, Korea.
authors.forename: Jungyoon
authors.initials: J
authors.lastname: Cho
authors.forename: Dukkyung
authors.initials: D
authors.lastname: Kim
authors.forename: SeungKi
authors.initials: S
authors.lastname: Lee
authors.forename: YoungJoo
authors.initials: Y
authors.lastname: Lee
mesh_terms: D016587:Antimutagenic Agents / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects*; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D005260:Female; D017405:Herpes Simplex Virus Protein Vmw65 / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins / Q000378:metabolism*; D014176:Protein Biosynthesis / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D016587:Antimutagenic Agents; D004268:DNA-Binding Proteins; D047628:Estrogen Receptor alpha; C497442:HIF1A protein, human; D017405:Herpes Simplex Virus Protein Vmw65; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D003035:Cobalt; C018021:cobaltous chloride