title: Retinoblastoma protein-mediated apoptosis after gamma-irradiation.
abstract: Restoration of expression of the retinoblastoma gene to DU-145 prostate-cancer cells sensitizes them to apoptosis induced by gamma-irradiation. In contrast, RB expression-protected cells from UV-induced cell death. RB, a caspase substrate, remained intact during apoptosis in gamma-irradiated DU-145 cells because serine proteases, but not caspases, were activated. In DU-145 cells, RB-mediated apoptosis involved biphasic activation of ABL kinase. ABL kinase was activated within minutes of irradiation, but in the presence of RB expression ABL kinase activation was enhanced 48 h after irradiation, coincident with the onset of cell death. Apoptosis was inhibited by RB mutants with constitutive ABL binding, but ABL overexpression overcame the effect of the RB mutant constructs. Expression of kinase-dead ABL had a dominant-negative effect on RB-mediated cell death. Activation of JUN N-terminal kinase depended on the presence of RB and occurred within 8 h of irradiation. Mutant JUN proteins that lacked the N-terminal transactivation domain and serine substrates for JUN N-terminal kinase inhibited cell death in a dominant-negative manner. Irradiation of DU-145 cells caused activation of p38 MAPK independent of the expression of RB. Inhibitors of p38 MAPK blocked apoptosis after irradiation of RB-expressing cells. The data show that after gamma-irradiation, intact RB mediates transcriptional activation that leads to activation of JNK and late activation of ABL kinase. In addition, p38 MAPK activation occurred independent of RB. ABL kinase, JUN N-terminal kinase, and p38 MAPK activity were all required for RB-mediated DU-145 cell death after gamma-irradiation.
authors.affiliation: Department of Medicine, Lombardi Cancer Center, Georgetown University, Washington, DC 20007-2197, USA.
authors.forename: Cai
authors.initials: C
authors.lastname: Bowen
authors.forename: Michael
authors.initials: M
authors.lastname: Birrer
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gelmann
mesh_terms: D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D020169:Caspases / Q000378:metabolism; D053938:DNA Fragmentation; D004789:Enzyme Activation; D005720:Gamma Rays; D017930:Genes, Reporter; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016315:Proto-Oncogene Proteins c-abl / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D007334:Insulin-Like Growth Factor I; D016315:Proto-Oncogene Proteins c-abl; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases