Abstract
Treatment of human U-937 myeloid leukemia cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) is associated with activation of the stress-activated protein kinase (SAPK) and induction of terminal monocytic differentiation. The present studies demonstrate that TPA targets SAPK to mitochondria by a mechanism dependent on activation of protein kinase C (PKC) beta. Translocation of SAPK to mitochondria in response to TPA is associated with release of cytochrome c, caspase-3 activation and induction of apoptosis. The results show that TPA induces the association of SAPK with the mitochondrial anti-apoptotic Bcl-x(L) protein. Overexpression of Bcl-x(L) attenuated the apoptotic response to TPA treatment. Moreover, expression of Bcl-x(L) mutated at sites of SAPK phosphorylation (Thr-47, -115) was more effective than wild-type Bcl-x(L) in abrogating TPA-induced cytochrome c release and apoptosis. By contrast, expression of Bcl-x(L) had little effect on induction of the monocytic phenotype. These findings indicate that myeloid leukemia cells respond to TPA with targeting of SAPK to mitochondria and that this response contributes to terminal differentiation through the release of cytochrome c and induction of apoptosis.
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 / drug effects
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Apoptosis / physiology*
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Carcinogens / pharmacology
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Cell Compartmentation / drug effects
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Cell Compartmentation / physiology
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Cell Differentiation / drug effects
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Cell Differentiation / physiology*
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Cytochrome c Group / drug effects
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Cytochrome c Group / metabolism
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Fluorescent Antibody Technique
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Gene Expression Regulation, Leukemic / drug effects
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Gene Expression Regulation, Leukemic / physiology
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Humans
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Immunoblotting
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Isoenzymes / drug effects
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Isoenzymes / metabolism
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Leukemia, Myeloid / drug therapy
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Leukemia, Myeloid / metabolism*
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Leukemia, Myeloid / physiopathology
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Mitochondria / drug effects
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Mitochondria / metabolism*
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Mitogen-Activated Protein Kinase 8
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Mitogen-Activated Protein Kinases / drug effects
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Mitogen-Activated Protein Kinases / immunology
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Mitogen-Activated Protein Kinases / metabolism*
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Monocytes / cytology
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Monocytes / drug effects
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Monocytes / metabolism
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Myeloid Progenitor Cells / cytology
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Myeloid Progenitor Cells / drug effects
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Myeloid Progenitor Cells / metabolism
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Protein Kinase C / drug effects
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Protein Kinase C / metabolism
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Protein Kinase C beta
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Proto-Oncogene Proteins c-bcl-2 / drug effects
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Tetradecanoylphorbol Acetate / pharmacology
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Tumor Cells, Cultured / cytology
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Tumor Cells, Cultured / drug effects
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Tumor Cells, Cultured / metabolism*
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bcl-X Protein
Substances
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BCL2L1 protein, human
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Carcinogens
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Cytochrome c Group
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Isoenzymes
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Proto-Oncogene Proteins c-bcl-2
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bcl-X Protein
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Protein Kinase C
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Protein Kinase C beta
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Mitogen-Activated Protein Kinase 8
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Mitogen-Activated Protein Kinases
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Tetradecanoylphorbol Acetate