ER stress induces caspase-8 activation, stimulating cytochrome c release and caspase-9 activation.
Excess ER stress induces caspase-12 activation and/or cytochrome c release, causing caspase-9 activation. Little is known about their relationship during ER stress-mediated cell death. Upon ER stress, P19 embryonal carcinoma (EC) cells showed activation of various caspases, including caspase-3, caspase-8, caspase-9, and caspase-12, and extensive DNA fragmentation. We examined the relationship between ER stress-mediated cytochrome c/caspase-9 and caspase-12 activation by using caspase-9- and caspase-8-deficient mouse embryonic fibroblasts and a P19 EC cell clone [P19-36/12 (-) cells] lacking expression of caspase-12. Caspase-9 and caspase-8 deficiency inhibited and delayed the onset of DNA fragmentation but did not inhibit caspase-12 processing induced by ER stress. P19-36/12 (-) cells underwent apoptosis upon ER stress, with cytochrome c release and caspase-8 and caspase-9 activation. The dominant negative form of FADD and z-VAD-fmk inhibited caspase-8, caspase-9, Bid processing, cytochrome c release, and DNA fragmentation induced by ER stress, suggesting that caspase-8 and caspase-9 are the main caspases involved in ER stress-mediated apoptosis of P19-36/12 (-) cells. Caspase-8 deficiency also inhibited the cytochrome c release induced by ER stress. Thus, in parallel with the caspase-12 activation, ER stress triggers caspase-8 activation, resulting in cytochrome c/caspase-9 activation via Bid processing.
Jimbo
A
A
Division of Development, National Institute of Neuroscience, NCNP, 4-1-1 Ogawahigashi-machi, Kodaira, Tokyo 187-8502, Japan.
Fujita
E
E
Kouroku
Y
Y
Ohnishi
J
J
Inohara
N
N
Kuida
K
K
Sakamaki
K
K
Yonehara
S
S
Momoi
T
T
D000818:Animals; D017209:Apoptosis; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000378:metabolism; D053454:Caspase 12; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism*; D053938:DNA Fragmentation; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D004789:Enzyme Activation / Q000502:physiology; D007158:Immunologic Techniques; D051379:Mice; D011499:Protein Processing, Post-Translational / Q000502:physiology; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; D002352:Carrier Proteins; D003574:Cytochrome c Group; C506440:Casp12 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053454:Caspase 12; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases