Abstract
Although the involvement of protein kinase C (PKC) in the activation of the mitogen-activated protein (MAP) kinase pathway has been implicated through experiments using 12-O-tetradecanoylphorbol-13-acetate (TPA), there has been no direct demonstration that PKC activates the MAP kinase pathway. A Raf-dependent intact cell assay system for monitoring the activation of MAPK/ERK kinase (MEK) and extracellular signal-related kinase (ERK) permitted us to evaluate the role of PKC isotypes in MAP kinase activation. Treatment of cells with TPA or epidermal growth factor resulted in the activation of MEK and ERK. The activation of the MAP kinase pathway triggered by epidermal growth factor was completely inhibited by dominant-negative Ras (RasN17), whereas the activation triggered by TPA was not, consistent with previous observations. The introduction of an activated point mutant of PKCdelta, but not PKCalpha or PKCepsilon, resulted in the activation of the MAP kinase pathway. The activation of MEK and ERK by an activated form of PKCdelta requires the presence of c-Raf and is independent of RasN17. These results demonstrate that activation of PKCdelta is sufficient for the activation of MEK and ERK and that the pathway operates in a manner dependent on c-Raf and independent of Ras.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3T3 Cells
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Animals
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COS Cells
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Calcium-Calmodulin-Dependent Protein Kinases / genetics
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
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Enzyme Activation
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Epidermal Growth Factor / pharmacology
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Isoenzymes / genetics
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Isoenzymes / metabolism*
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MAP Kinase Kinase 1
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Mice
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinase Kinases*
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Mitogen-Activated Protein Kinases*
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Models, Biological
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Mutation
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Protein Kinase C / genetics
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Protein Kinase C / metabolism*
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Protein Kinase C-delta
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Protein Serine-Threonine Kinases / metabolism*
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Protein-Tyrosine Kinases / metabolism*
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-raf
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Rats
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Recombinant Fusion Proteins / metabolism
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Signal Transduction
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Tetradecanoylphorbol Acetate / pharmacology
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ras Proteins / metabolism*
Substances
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Isoenzymes
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Proto-Oncogene Proteins
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Recombinant Fusion Proteins
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Epidermal Growth Factor
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Prkcd protein, mouse
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Prkcd protein, rat
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Protein-Tyrosine Kinases
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-raf
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Protein Kinase C
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Protein Kinase C-delta
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Calcium-Calmodulin-Dependent Protein Kinases
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 1
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Map2k1 protein, mouse
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Mitogen-Activated Protein Kinase Kinases
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ras Proteins
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Tetradecanoylphorbol Acetate