Abstract
The involvement of dual specificity phosphatases (DSPs) in the mitogen-activated protein kinase (MAPK) signaling has been mostly limited to the inactivation of MAPKs by the direct dephosphorylation of the TXY motif within their activation loop. We report the cloning and characterization of a murine DSP, called JNK pathway-associated phosphatase (JKAP), which lacks the regulatory region present in most other MAP kinase phosphatases (MKPs) and is preferentially expressed in murine Lin(-)Sca-1(+) stem cells. Overexpression of JKAP in human embryonic kidney 293T cells specifically activated c-Jun N-terminal kinase (JNK) but not p38 and extracellular signal-regulated kinase 2. Overexpression of a mutant JKAP, JKAP-C88S, blocked tumor necrosis factor-alpha-induced JNK activation. Targeted gene disruption in murine embryonic stem cells abolished JNK activation by tumor necrosis factor-alpha and transforming growth factor-beta, but not by ultraviolet-C irradiation, indicating that JKAP is necessary for optimal JNK activation. JKAP associated with JNK and MKK7, but not SEK1, in vivo. However, JKAP did not interact with JNK in vitro, suggesting that JKAP exerts its effect on JNK in an indirect manner. Taken together, these studies identify a positive regulator for the JNK pathway and suggest a novel role for DSP in mitogen-activated protein kinase regulation.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Cell Line
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Crosses, Genetic
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DNA, Complementary / metabolism
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Dose-Response Relationship, Drug
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Enzyme Activation
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Hematopoietic Stem Cells / metabolism
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Humans
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In Situ Hybridization
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JNK Mitogen-Activated Protein Kinases*
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MAP Kinase Kinase 4*
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MAP Kinase Kinase 7
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MAP Kinase Signaling System
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Mice
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Mice, Inbred C57BL
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase Kinases / metabolism*
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Mitogen-Activated Protein Kinases
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Models, Genetic
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Molecular Sequence Data
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Mutation
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Phosphoprotein Phosphatases / metabolism*
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Phosphoprotein Phosphatases / physiology*
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Plasmids / metabolism
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Precipitin Tests
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Protein Binding
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RNA, Messenger / metabolism
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Sequence Homology, Amino Acid
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Signal Transduction
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Substrate Specificity
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Tissue Distribution
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Transfection
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Transforming Growth Factor beta / pharmacology
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Tumor Necrosis Factor-alpha / metabolism*
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Ultraviolet Rays
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p38 Mitogen-Activated Protein Kinases
Substances
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DNA, Complementary
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RNA, Messenger
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Transforming Growth Factor beta
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Tumor Necrosis Factor-alpha
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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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p38 Mitogen-Activated Protein Kinases
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MAP Kinase Kinase 4
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MAP Kinase Kinase 7
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MAP2K4 protein, human
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MAP2K7 protein, human
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Map2k4 protein, mouse
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Map2k7 protein, mouse
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Mitogen-Activated Protein Kinase Kinases
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JKAP protein, mouse
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Phosphoprotein Phosphatases