title: Ionizing radiation-induced apoptosis in ataxia-telangiectasia fibroblasts. Roles of caspase-9 and cellular inhibitor of apoptosis protein-1.
abstract: Ionizing radiation (IR) has been shown to induce apoptosis to a greater extent in a fibroblast cell line AT5BIVA derived from an individual with ataxia-telangiectasia (AT) than in control fibroblasts. However, the signaling pathway that underlies IR-induced apoptosis in AT cells has remained unknown. The mechanism of apoptosis in response to gamma-irradiation has now been examined in three AT fibroblast lines (AT3BIVA, AT4BIVA, and AT5BIVA) derived from different individuals with AT. The apoptotic indexes of these cell lines at 72 h after irradiation were 12, 31, and 35%, respectively, compared with a value of 2.3% for control fibroblasts. Immunoblot analysis and fluorometric assays revealed that the extents of IR-induced activation of caspase-3 and caspase-9 were markedly greater in AT4BIVA and AT5BIVA cells than in AT3BIVA and control cells. Furthermore, the basal abundance of the apoptotic inhibitor, a cellular inhibitor of apoptosis proteins (c-IAP-1), was markedly reduced in AT4BIVA and AT5BIVA cells compared with that in AT3BIVA and control cells. The overexpression of either caspase-9 mutant forms or recombinant c-IAP-1 in AT5BIVA cells inhibited the IR-induced activation of caspases-3 and 9 and reduced the apoptotic index of the irradiated cells. These results indicate that the extent of IR-induced apoptosis in different AT cell lines is inversely related to the abundance of c-IAP-1 and directly related to the extent of activation of caspases-3 and 9.
authors.affiliation: Department of Radiation Medicine, Division of Radiation Research, Vincent T. Lombardi Cancer Center, Georgetown University School of Medicine, Washington, D. C. 20007, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Dimtchev
authors.forename: A
authors.initials: A
authors.lastname: Dritschilo
authors.forename: M
authors.initials: M
authors.lastname: Jung
mesh_terms: D019943:Amino Acid Substitution; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D001260:Ataxia Telangiectasia / Q000378:metabolism* / Q000473:pathology*; D001665:Binding Sites; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000473:pathology / Q000528:radiation effects; D005720:Gamma Rays; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D011506:Proteins; D011994:Recombinant Proteins; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases