Abstract
Growth factors activate mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases (ERKs) and Jun kinases (JNKs). Although the signaling cascade from growth factor receptors to ERKs is relatively well understood, the pathway leading to JNK activation is more obscure. Activation of JNK by epidermal growth factor (EGF) or nerve growth factor (NGF) was dependent on H-Ras activation, whereas JNK activation by tumor necrosis factor alpha (TNF-alpha) was Ras-independent. Ras activates two protein kinases, Raf-1 and MEK (MAPK, or ERK, kinase) kinase (MEKK). Raf-1 contributes directly to ERK activation but not to JNK activation, whereas MEKK participated in JNK activation but caused ERK activation only after overexpression. These results demonstrate the existence of two distinct Ras-dependent MAPK cascades--one initiated by Raf-1 leading to ERK activation, and the other initiated by MEKK leading to JNK activation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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3T3 Cells
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Animals
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Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
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Enzyme Activation / drug effects
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Epidermal Growth Factor / pharmacology
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Genes, ras
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HeLa Cells
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Humans
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JNK Mitogen-Activated Protein Kinases
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MAP Kinase Kinase Kinase 1*
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Mice
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinases*
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Nerve Growth Factors / pharmacology
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PC12 Cells
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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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Transfection
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Tumor Necrosis Factor-alpha / pharmacology
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ras Proteins / pharmacology*
Substances
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Nerve Growth Factors
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Proto-Oncogene Proteins
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Tumor Necrosis Factor-alpha
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Epidermal Growth Factor
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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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Calcium-Calmodulin-Dependent Protein Kinases
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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 Kinases
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MAP Kinase Kinase Kinase 1
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MAP3K1 protein, human
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Map3k1 protein, mouse
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ras Proteins