Suppression of postmitochondrial signaling and delayed response to UV-induced nuclear apoptosis in HeLa cells.
Activation of postmitochondrial pathways by UV irradiation was examined using mouse lymphoma 3SB and human leukemic Jurkat cells and two human carcinoma cell lines (HeLa and MCF-7). Exposure of 3SB and Jurkat cells resulted in large amounts of cytochrome c and apoptosis-inducing factor (AIF) being released into the cytosol, and a clear laddering pattern of DNA fragments was observed within 3 h of incubation after irradiation. Simultaneously, activation of caspase-9 and its downstream caspases was detected. HeLa and MCF-7 cells also showed extensive release of mitochondrial factors and caspase-9 activation at 4 to 6 h after exposure, but apoptotic nuclear changes appeared much later. Compared with 3SB and Jurkat cells, these carcinoma cell lines exhibited reduced activation of caspase-9-like proteolytic activity by UV radiation, and levels of caspase-3-like activity in HeLa cells were extremely low, similar to those in caspase-3-deficient MCF-7 cells. These results suggest that the delayed response to UV-induced nuclear apoptosis in HeLa cells is due to a reduced activation of the caspase cascade downstream of cytochrome c release and suppression of caspase-3 activity.
Sasai
Kaori
K
Department of Regulatory Radiobiology, Research Institute for Radiation Biology and Medicine, Hiroshima University, Hiroshima 734-8553, Japan.
Yajima
Hirohiko
H
Suzuki
Fumio
F
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects*; D051033:Apoptosis Inducing Factor; D015153:Blotting, Western; D053148:Caspase 3; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000528:radiation effects; D003374:Coumarins / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D005420:Flavoproteins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D009842:Oligopeptides / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014466:Ultraviolet Rays
C494829:AIFM1 protein, human; D051033:Apoptosis Inducing Factor; D061945:Caspase Inhibitors; D003374:Coumarins; D003574:Cytochrome c Group; D004273:DNA, Neoplasm; D005420:Flavoproteins; D005456:Fluorescent Dyes; D008565:Membrane Proteins; D009842:Oligopeptides; C102580:acetyl-aspartyl-glutamyl-valyl-aspartyl-amino-4-methylcoumarin; C505407:CASP3 protein, human; C506433:CASP9 protein, human; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases