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PI3K/Akt is required for heat shock proteins to protect hypoxia-inducible factor 1alpha from pVHL-independent degradation.
J Biol Chem. 2004 Apr 02; 279(14):13506-13.JB

Abstract

Hypoxia inducible factor 1 (HIF-1), a heterodimeric transcription factor composed of HIF-1alpha and HIF-1beta subunits, serves as a key regulator of metabolic adaptation to hypoxia. The amount of HIF-1alpha protein is regulated either by attenuating von Hippel-Lindau protein (pVHL)-dependent ubiquitination and subsequent 26 S proteasomal degradation or by enhancing cap-dependent mRNA translation, presumably involving a phosphatidyinositol 3-kinase (PI3K)/Akt-regulated pathway. In addition, it became apparent that Hsp90 protects HIF-1alpha from oxygen-independent degradation. Here we present evidence that PI3K/Akt is required for heat shock proteins to stabilize HIF-1alpha. In pVHL-deficient renal cell carcinoma cells, PI3K inhibition by LY294002 and wortmannin or transfection of either a dominant negative PI3K or a kinase-dead Akt mutant substantially lowered constitutively expressed HIF-1alpha without altering HIF-1alpha mRNA. Inhibitors of mitogen-activated protein kinase kinase (MAPKK) such as PD98059 or the p38 MAPK inhibitor SB203580 showed no interference. Considering that PI3K inhibitors down-regulated heat shock protein 90 (Hsp90) as well as Hsp70 expression and moreover attenuated heat- or hypoxia-induced Hsp70 as well as hypoxia-induced Hsp90 up-regulation we conclude that PI3K inhibition promoted degradation of HIF-1alpha indirectly by reducing steady state concentrations of Hsp90 and/or Hsp70. HIF-1alpha co-immunoprecipitated with Hsp90/Hsp70 and direct binding of Hsp70 to the oxygen-dependent degradation domain (ODD) of HIF-1alpha was proven by a pull-down assay and a peptide array. PI3K-mediated degradation of HIF-1alpha was confirmed in HEK 293 cells under hypoxia, suggesting that heat shock proteins constitute an integral component for HIF-1alpha accumulation. We conclude that PI3K/Akt contributes to HIF-1alpha stabilization by provoking expression of heat shock proteins.

Authors+Show Affiliations

Department of Cell Biology, Faculty of Biology, University of Kaiserslautern, 67663 Kaiserslautern, Germany.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

14726529

Citation

Zhou, Jie, et al. "PI3K/Akt Is Required for Heat Shock Proteins to Protect Hypoxia-inducible Factor 1alpha From pVHL-independent Degradation." The Journal of Biological Chemistry, vol. 279, no. 14, 2004, pp. 13506-13.
Zhou J, Schmid T, Frank R, et al. PI3K/Akt is required for heat shock proteins to protect hypoxia-inducible factor 1alpha from pVHL-independent degradation. J Biol Chem. 2004;279(14):13506-13.
Zhou, J., Schmid, T., Frank, R., & Brüne, B. (2004). PI3K/Akt is required for heat shock proteins to protect hypoxia-inducible factor 1alpha from pVHL-independent degradation. The Journal of Biological Chemistry, 279(14), 13506-13.
Zhou J, et al. PI3K/Akt Is Required for Heat Shock Proteins to Protect Hypoxia-inducible Factor 1alpha From pVHL-independent Degradation. J Biol Chem. 2004 Apr 2;279(14):13506-13. PubMed PMID: 14726529.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - PI3K/Akt is required for heat shock proteins to protect hypoxia-inducible factor 1alpha from pVHL-independent degradation. AU - Zhou,Jie, AU - Schmid,Tobias, AU - Frank,Ronald, AU - Brüne,Bernhard, Y1 - 2004/01/15/ PY - 2004/1/17/pubmed PY - 2004/5/12/medline PY - 2004/1/17/entrez SP - 13506 EP - 13 JF - The Journal of biological chemistry JO - J Biol Chem VL - 279 IS - 14 N2 - Hypoxia inducible factor 1 (HIF-1), a heterodimeric transcription factor composed of HIF-1alpha and HIF-1beta subunits, serves as a key regulator of metabolic adaptation to hypoxia. The amount of HIF-1alpha protein is regulated either by attenuating von Hippel-Lindau protein (pVHL)-dependent ubiquitination and subsequent 26 S proteasomal degradation or by enhancing cap-dependent mRNA translation, presumably involving a phosphatidyinositol 3-kinase (PI3K)/Akt-regulated pathway. In addition, it became apparent that Hsp90 protects HIF-1alpha from oxygen-independent degradation. Here we present evidence that PI3K/Akt is required for heat shock proteins to stabilize HIF-1alpha. In pVHL-deficient renal cell carcinoma cells, PI3K inhibition by LY294002 and wortmannin or transfection of either a dominant negative PI3K or a kinase-dead Akt mutant substantially lowered constitutively expressed HIF-1alpha without altering HIF-1alpha mRNA. Inhibitors of mitogen-activated protein kinase kinase (MAPKK) such as PD98059 or the p38 MAPK inhibitor SB203580 showed no interference. Considering that PI3K inhibitors down-regulated heat shock protein 90 (Hsp90) as well as Hsp70 expression and moreover attenuated heat- or hypoxia-induced Hsp70 as well as hypoxia-induced Hsp90 up-regulation we conclude that PI3K inhibition promoted degradation of HIF-1alpha indirectly by reducing steady state concentrations of Hsp90 and/or Hsp70. HIF-1alpha co-immunoprecipitated with Hsp90/Hsp70 and direct binding of Hsp70 to the oxygen-dependent degradation domain (ODD) of HIF-1alpha was proven by a pull-down assay and a peptide array. PI3K-mediated degradation of HIF-1alpha was confirmed in HEK 293 cells under hypoxia, suggesting that heat shock proteins constitute an integral component for HIF-1alpha accumulation. We conclude that PI3K/Akt contributes to HIF-1alpha stabilization by provoking expression of heat shock proteins. SN - 0021-9258 UR - https://www.unboundmedicine.com/medline/citation/14726529/PI3K/Akt_is_required_for_heat_shock_proteins_to_protect_hypoxia_inducible_factor_1alpha_from_pVHL_independent_degradation_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0021-9258(19)64009-3 DB - PRIME DP - Unbound Medicine ER -