Abstract
HIF-1α not only enables cells to survive under hypoxic conditions but also promotes cell cycle arrest and apoptosis. Therefore, its expression should be controlled at optimal levels in growing tumors. We recently reported that bafilomycin A1 exorbitantly expressed HIF-1α and induced the p21WAF1/Cip1-mediated growth arrest of tumors (Mol Pharmacol70:1856–1865, 2006). In the present study, we addressed the mechanism underlying bafilomycin-induced HIF-1α expression. Bafilomycin stabilized HIF-1α under normoxic conditions without changes in intracellular pH. However, when ATP6V0C, the target protein of bafilomycin, was knocked down, this bafilomycin effect was significantly attenuated. Inversely, ATP6V0C expression increased HIF-1α levels in a gene dose-dependent manner. ATP6V0C competed with Von Hippel-Lindau protein in HIF-1α binding by directly interacting with HIF-1α, which was stimulated by bafilomycin. In confocal images, ATP6V0C was normally present in the cytoplasm but was translocated in company with HIF-1α to the nucleus by bafilomycin. The N-terminal end (amino acids 1–16) of HIF-1α was identified as the ATP6V0C-interacting motif. These results suggest that ATP6V0C, a novel regulator of HIF-1α, mediates HIF-1α expression by bafilomycin.
Footnotes
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This work was supported by a grant from the Korean Ministry of Health and Welfare Research Fund 2005 (A050479) and by a grant from the National R&D Program for Cancer Control, Ministry of Health and Welfare Research Fund (0520260-2).
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J.-H.L. and J.-W.P. contributed equally to this work.
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Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
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doi:10.1124/mol.106.030296.
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ABBREVIATIONS: HIF-1α, hypoxia-inducible factor 1α; ARNT, aryl hydrocarbon receptor nuclear translocator; ODDD, oxygen-dependent degradation domain; PHD, prolyl hydroxylase; pVHL, von Hippel-Lindau tumor suppressor protein; ATP6V0C, subunit c in V0 sector of V-ATPase; Vc, ATP6V0C; BM, bafilomycin A1; V-ATPase, vacuolar H+ ATPase; HEK, human embryonic kidney; HA, hemagglutinin; PCR, polymerase chain reaction; RT, reverse transcription/transcriptase; siRNA, small interfering RNA; pHi, intracellular pH; BCECF, 2,7-bis(2-carboxyethyl)-5(6)-carboxyfluorescein; RFP, red fluorescent protein; GFP, green fluorescent protein; mHIF-1α, HIF-1α mutant; MG132, N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal.
- Received August 26, 2006.
- Accepted December 15, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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