Abstract
CC139 fibroblasts are one of several model systems in which the Raf --> MEK --> ERK1/2 pathway can inhibit apoptosis independently of the PI3K pathway; however, the precise mechanism for this protective effect is not known. Serum withdrawal from CC139 fibroblasts resulted in the rapid onset of apoptosis, which was prevented by actinomycin D or cycloheximide. Serum withdrawal promoted the rapid, de novo accumulation of Bim(EL), a proapoptotic 'BH3-only' member of the Bcl-2 protein family. Bim(EL) expression was an early event, occurring several hours prior to caspase activation. In contrast to studies in neurons, activation of the JNK --> c-Jun pathway was neither necessary nor sufficient to induce Bim(EL) expression. Selective inhibition of either the ERK pathway (with U0126) or the PI3K pathway (with LY294002) caused an increase in the expression of Bim(EL). Furthermore, selective activation of the ERK1/2 pathway by deltaRaf-1:ER* substantially reduced Bim(EL) expression, abolished conformational changes in Bax and blocked the appearance of apoptotic cells. The ability of deltaRaf-1:ER* to repress Bim(EL) expression required the ERK pathway but was independent of the PI3K --> PDK --> PKB pathway. Thus, serum withdrawal-induced expression of Bim(EL) occurs independently of the JNK --> c-Jun pathway and can be repressed by the ERK pathway independently of the PI3K pathway. This may contribute to Raf- and Ras-induced cell survival at low serum concentrations.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Apoptosis / drug effects
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Apoptosis Regulatory Proteins
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Bcl-2-Like Protein 11
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Butadienes / pharmacology
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Carrier Proteins / biosynthesis*
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Carrier Proteins / genetics
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Cell Line / drug effects
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Cell Line / metabolism
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Chromones / pharmacology
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Cricetinae
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Cricetulus
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Culture Media, Serum-Free / pharmacology
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Cycloheximide / pharmacology
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Cysteine Endopeptidases / pharmacology
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Cysteine Proteinase Inhibitors / pharmacology
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Dactinomycin / pharmacology
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Enzyme Activation / drug effects
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Enzyme Inhibitors / pharmacology
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Fibroblasts / metabolism
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JNK Mitogen-Activated Protein Kinases
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Lung
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Membrane Proteins*
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Mitogen-Activated Protein Kinase 1 / antagonists & inhibitors
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Mitogen-Activated Protein Kinase 1 / metabolism*
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases / antagonists & inhibitors
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Mitogen-Activated Protein Kinases / metabolism*
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Mitogen-Activated Protein Kinases / physiology*
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Morpholines / pharmacology
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Nitriles / pharmacology
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Nucleic Acid Synthesis Inhibitors / pharmacology
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Phosphatidylinositol 3-Kinases / physiology*
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Phosphoinositide-3 Kinase Inhibitors
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism
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Protein Structure, Tertiary
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Protein Synthesis Inhibitors / pharmacology
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2*
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Proto-Oncogene Proteins c-raf / genetics
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Proto-Oncogene Proteins c-raf / physiology*
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RNA, Messenger / biosynthesis
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RNA, Messenger / genetics
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Recombinant Fusion Proteins / metabolism
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Signal Transduction / drug effects
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Signal Transduction / physiology
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bcl-2-Associated X Protein
Substances
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Apoptosis Regulatory Proteins
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Bcl-2-Like Protein 11
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Butadienes
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Carrier Proteins
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Chromones
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Culture Media, Serum-Free
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Cysteine Proteinase Inhibitors
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Enzyme Inhibitors
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Membrane Proteins
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Morpholines
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Nitriles
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Nucleic Acid Synthesis Inhibitors
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Phosphoinositide-3 Kinase Inhibitors
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Protein Synthesis Inhibitors
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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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Recombinant Fusion Proteins
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U 0126
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bcl-2-Associated X Protein
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Dactinomycin
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Cycloheximide
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-raf
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JNK Mitogen-Activated Protein Kinases
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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Cysteine Endopeptidases