title: Hydrogen peroxide-mediated cytosolic acidification is a signal for mitochondrial translocation of Bax during drug-induced apoptosis of tumor cells.
abstract: Absence of the proapoptotic protein Bax renders tumor cells resistant to drug-induced apoptosis. We have shown that hydrogen peroxide (H(2)O(2))-mediated cytosolic acidification is an effector mechanism during drug-induced apoptosis of tumor cells. Here, we report that Bax is critical in determining the sensitivity of tumor cells to H(2)O(2)-induced apoptosis. More importantly, exposure of colorectal carcinoma (HCT116) and leukemia cells (HL60 and CEM) to H(2)O(2) or its intracellular production during drug-induced apoptosis is a signal for mitochondrial translocation of Bax. Furthermore, we provide evidence that drug-induced H(2)O(2)-mediated Bax translocation in tumor cells is caspase independent but involves cytosolic acidification. Inhibiting cytosolic acidification prevents Bax translocation, and contrarily enforced acidification of the intracellular milieu results in mitochondrial recruitment of Bax, even in the absence of a trigger. These findings provide a novel mechanism for mitochondrial translocation of Bax and directly implicate H(2)O(2)-mediated cytosolic acidification in the recruitment of the mitochondrial pathway during drug-induced apoptosis of tumor cells.
authors.affiliation: Department of Physiology, Faculty of Medicine, National University of Singapore, Singapore.
authors.forename: Kashif A
authors.initials: KA
authors.lastname: Ahmad
authors.forename: Kartini B
authors.initials: KB
authors.lastname: Iskandar
authors.forename: Jayshree L
authors.initials: JL
authors.lastname: Hirpara
authors.forename: Marie-Veronique
authors.initials: MV
authors.lastname: Clement
authors.forename: Shazib
authors.initials: S
authors.lastname: Pervaiz
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D003600:Cytosol / Q000378:metabolism*; D018922:HL-60 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008928:Mitochondria / Q000378:metabolism*; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; D006861:Hydrogen Peroxide