Abstract
Both the mitogen-activated protein kinase (MAPK) phosphatases MKP-1 and MKP-2 exert important feedback control of MAPK-mediated signaling events. The function of MKP-1 and MKP-2 is regulated via complex mechanisms, ranging from increased transcription of the MKP-1 and MKP-2 genes to post-translational catalytic activation of MKP-1 and MKP-2 proteins upon binding to their substrate MAPKs. In addition, MKP-1 stability increases upon ERK-dependent phosphorylation of two serine residues in its C-terminus. The C-terminal regions of MKP-1 and MKP-2, but not those of other MKPs, are homologous. To investigate the role of this domain, we have deleted the C-terminal tails from MKP-1 and MKP-2 and examined the effect of these deletions on their enzymatic activity. C-terminally truncated MKP-1 and MKP-2 exhibited, both in vivo and in vitro, substantially greater phosphatase activity towards their substrate MAPKs than did the full-length counterparts. However, C-terminal truncations did not significantly change either their substrate affinity, or their substrate-mediated catalytic activation. Basal phosphatase activity of the truncated proteins was also significantly higher than that of the wild-type counterparts. Collectively, these results suggest that the C-terminal domain may potentially play a role in the regulation of MKP-1 and MKP-2.
MeSH terms
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Amino Acid Sequence
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Animals
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Blotting, Western
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Catalytic Domain
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Cell Cycle Proteins*
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Dual Specificity Phosphatase 1
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Gene Deletion
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Glutathione Transferase / metabolism
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Immediate-Early Proteins / metabolism*
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In Vitro Techniques
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JNK Mitogen-Activated Protein Kinases*
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MAP Kinase Kinase 4
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinase Kinases / immunology
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Mitogen-Activated Protein Kinase Kinases / metabolism
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Mitogen-Activated Protein Kinases / antagonists & inhibitors*
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Mitogen-Activated Protein Kinases / immunology
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Mitogen-Activated Protein Kinases / metabolism
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Molecular Sequence Data
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Nitrophenols / metabolism
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Organophosphorus Compounds / metabolism
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Phosphoprotein Phosphatases*
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Phosphorylation
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Plasmids
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Protein Phosphatase 1
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Protein Tyrosine Phosphatases / metabolism*
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Recombinant Fusion Proteins / metabolism
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Sequence Homology, Amino Acid
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Transcription Factor AP-1 / pharmacology
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Transcription, Genetic
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Tumor Cells, Cultured / metabolism*
Substances
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Cell Cycle Proteins
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Immediate-Early Proteins
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Nitrophenols
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Organophosphorus Compounds
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Recombinant Fusion Proteins
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Transcription Factor AP-1
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nitrophenylphosphate
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Glutathione Transferase
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JNK Mitogen-Activated 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 4
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Mitogen-Activated Protein Kinase Kinases
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Phosphoprotein Phosphatases
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Protein Phosphatase 1
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Dual Specificity Phosphatase 1
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Protein Tyrosine Phosphatases