title: Ionizing radiation-induced, Bax-mediated cell death is dependent on activation of cysteine and serine proteases.
abstract: Bcl-2 family proteins and interleukin-1-beta converting enzyme/Caenorhabditis elegans cell death gene-3 (ICE/CED-3) family proteases (caspases) represent the basic regulators of apoptosis. However, the precise mechanism by which they interact is unclear. In this study, we found that gamma-radiation-induced apoptosis of leukemia cells was associated with activation of multiple caspases and bax up-regulation. Membrane changes and caspase activities were suppressed by specific caspase inhibitors. Similarly, the serine protease inhibitors z-Ala-Ala-Asp-cmk (AAD) and tosyl-lysine chloromethyl ketone (TLCK) also prevented caspase activation and poly(ADP-ribose) polymerase cleavage in vivo but had no effect on caspase activity in vitro. TLCK also prevented bax up-regulation as a result of its inhibitory effect on p53 function. Inhibitors of caspases and serine proteases partially prevented cell death, suggesting a caspase involvement in Bax-mediated cell death. We propose an ordering of signaling events in Bax-mediated cell death, including steps upstream and downstream of p53 and bax up-regulation.
authors.affiliation: Department of Cancer Biology, Lerner Research Institute, The Cleveland Clinic Foundation, Ohio 44195, USA.
authors.forename: B
authors.initials: B
authors.lastname: Gong
authors.forename: Q
authors.initials: Q
authors.lastname: Chen
authors.forename: B
authors.initials: B
authors.lastname: Endlich
authors.forename: S
authors.initials: S
authors.lastname: Mazumder
authors.forename: A
authors.initials: A
authors.lastname: Almasan
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation; D005720:Gamma Rays; D006801:Humans; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D015854:Up-Regulation; D051028:bcl-2-Associated X Protein
chemical_list: C494826:BAX protein, human; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D015842:Serine Proteinase Inhibitors; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D014107:Tosyllysine Chloromethyl Ketone; D012697:Serine Endopeptidases; D020169:Caspases