ATP6V0C competes with von Hippel-Lindau protein in hypoxia-inducible factor 1alpha (HIF-1alpha) binding and mediates HIF-1alpha expression by bafilomycin A1.
HIF-1alpha 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-1alpha and induced the p21(WAF1/Cip1)-mediated growth arrest of tumors (Mol Pharmacol 70:1856-1865, 2006). In the present study, we addressed the mechanism underlying bafilomycin-induced HIF-1alpha expression. Bafilomycin stabilized HIF-1alpha 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-1alpha levels in a gene dose-dependent manner. ATP6V0C competed with Von Hippel-Lindau protein in HIF-1alpha binding by directly interacting with HIF-1alpha, which was stimulated by bafilomycin. In confocal images, ATP6V0C was normally present in the cytoplasm but was translocated in company with HIF-1alpha to the nucleus by bafilomycin. The N-terminal end (amino acids 1-16) of HIF-1alpha was identified as the ATP6V0C-interacting motif. These results suggest that ATP6V0C, a novel regulator of HIF-1alpha, mediates HIF-1alpha expression by bafilomycin.
Lim
Ji-Hong
JH
Cancer Research Institute, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul 110-799, Korea.
Park
Jong-Wan
JW
Kim
Sung Joon
SJ
Kim
Myung-Suk
MS
Park
Sang-Ki
SK
Johnson
Randall S
RS
Chun
Yang-Sook
YS
D020816:Amino Acid Motifs; D001667:Binding, Competitive; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000737:chemistry / Q000378:metabolism*; D018942:Macrolides / Q000494:pharmacology*; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism*
D004791:Enzyme Inhibitors; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018942:Macrolides; C040929:bafilomycin A1; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D025262:Vacuolar Proton-Translocating ATPases; C497446:VHL protein, human