Abstract
Cellular stress leads to DNA damage and activation of the intrinsic apoptotic pathway in which translocation of mitochondrial cytochrome c to the cytosol plays a critical role. Previous studies have suggested alternative mechanisms responsible for this process. We examined initiation mechanisms of the intrinsic apoptotic pathway using human neuroblastoma and breast cancer cells. Results indicated that translocation of cytochrome c does not require prior activation of caspases but rather depends on activation of specific BCL-2 family members, depending upon the type of death signal. Thus, DNA damage-induced apoptosis requires new protein synthesis, accumulation of p53 tumor suppressor protein, and p53-dependent induction of BOK and NOXA genes, while a role for BAX in this pathway is not essential. In contrast, apoptosis induced by staurosporine does not require protein synthesis but is characterized by translocation of BAX. Based on these findings, we propose a model of the intrinsic apoptotic cascade induced by DNA damage where proapoptotic BOK substitutes for a function of BAX.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Apoptosis*
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Caspase 2
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Caspase 3
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Caspase 8
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Caspase 9
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Caspases / metabolism
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Cell Death
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Cell Line, Tumor
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Cell Survival
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Cytochromes c / metabolism
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Cytosol / metabolism
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DNA Damage
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Enzyme Activation
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Etoposide / pharmacology
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Humans
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Immunoblotting
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Microscopy, Confocal
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Microscopy, Fluorescence
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Protein Transport
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Proto-Oncogene Proteins c-bcl-2 / physiology*
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RNA Interference
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RNA, Messenger / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Staurosporine / pharmacology
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Time Factors
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Transfection
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Tumor Suppressor Protein p53 / metabolism*
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bcl-2-Associated X Protein
Substances
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BAX protein, human
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Bok protein, mouse
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PMAIP1 protein, human
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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RNA, Messenger
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Tumor Suppressor Protein p53
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bcl-2-Associated X Protein
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Etoposide
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Cytochromes c
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CASP3 protein, human
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CASP8 protein, human
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CASP9 protein, human
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Casp3 protein, mouse
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Casp8 protein, mouse
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Casp9 protein, mouse
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Caspase 2
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Caspase 3
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Caspase 8
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Caspase 9
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Caspases
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Staurosporine