1 Nature Reviews Drug Discovery 2007 Vol: 6(5):391-403. DOI: 10.1038/nrd2289

Targeting dual-specificity phosphatases: manipulating MAP kinase signalling and immune responses

Dual-specificity phosphatases (DUSPs) are a subset of protein tyrosine phosphatases, many of which dephosphorylate threonine and tyrosine residues on mitogen-activated protein kinases (MAPKs), and hence are also referred to as MAPK phosphatases (MKPs). The regulated expression and activity of DUSP family members in different cells and tissues controls MAPK intensity and duration to determine the type of physiological response. For immune cells, DUSPs regulate responses in both positive and negative ways, and DUSP-deficient mice have been used to identify individual DUSPs as key regulators of immune responses. From a drug discovery perspective, DUSP family members are promising drug targets for manipulating MAPK-dependent immune responses in a cell-type and disease-context-dependent manner, to either boost or subdue immune responses in cancers, infectious diseases or inflammatory disorders.

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Figures
Figure 1: The MAPK pathway and the role of DUSPs.The three main arms of the mitogen-activated protein kinase (MAPK) pathway, ERK (extracellular signal-regulated kinase), JNK (c-Jun N-terminal kinase) and p38, that mediate immune cell functional responses to stimuli through multiple receptors such as chemoattractant receptors, Toll-like receptors and cytokine receptors are shown. The three-tiered kinase dynamic cascade leads to activated MAPKs entering the nucleus to trigger immediate early gene and transcription factor activation for cellular responses such as cytokine production, apoptosis and migration. Approximately 18 MAPK genes encompassing four subfamilies have now been identified in mammalian cells137. The main classes of mammalian MAPKs consist of ERK1 and ERK2, and the more recently identified larger kinases ERK3 (α and β), ERK4 (ERK1b), ERK5, ERK7 and ERK8; p38 MAPKs (p38α, β, γ, δ); and JNKs, also known as stress-activated protein kinases (SAPK1, 2, 3) (for recent reviews see Refs 6,8,9,97,138,139). All MAPKs, except the larger ERKs that remain less well characterized139, 140, are activated by dual phosphorylation of the threonine and tyrosine residues within a conserved 'TXY' motif in their kinase domain. A general feature of MAPK pathways is the three-tiered kinase canonical cascade consisting of a MAPK, a MAPK kinase (MAP2K, MAPKK, MKK or MEK) and a MAPK kinase kinase (MAP3K or MAPKKK)9, 141. The existence of this tier is probably essential for the amplification and tight regulation of the transmitted signal. Seven upstream MAP2Ks and 14 MAP3Ks have been identified9, 141, 142. For receptor tyrosine kinases (RTKs) and G-protein coupled receptors (GPCRs), MAPK cascade activation is initiated by small GTP-binding proteins, STE20-like kinases or by adaptor proteins that transmit the signal to MAP3Ks9. MAP3Ks then transfer the signal to MAP2Ks to induce MAPK activation. Thus, MAP3Ks provide some stimulus specificity, creating independent signalling modules that may function in parallel, whereas the MAPKs carry out the effector functions of each cascade, either through direct phosphorylation of effector proteins, such as transcription factors, or activation of subordinate kinases, known as MAPK-activated protein kinases (MAPKAPKs). Multiple dual-specificity phosphatases (DUSPs) specifically dephosphorylate the threonine and tyrosine residues on MAPKs, rendering them inactive either in the cytoplasm or nucleus. DUSPs also assist in shuttling or anchoring MAPKs to control their activity. Red arrows indicate feedback or crosstalk within the MAPK pathway. Figure 2: Regulation of DUSPs by MAPKs.In contrast to mitogen-activated protein kinases (MAPKs) themselves, dual-specificity phosphatase (DUSP) expression and activity are strongly regulated by three main mechanisms as shown in panels a–c. a | The unique, strong, transcriptional activation of DUSPs to various stimuli either through immediate early gene (IEG) activation (DUSP1, DUSP4, DUSP7 and DUSP2), or by other transcription factors (DUSP6, DUSP9, DUSP10 and DUSP8) through activity of MAPKs themselves. MAPK-dependent activation of E-box and AP2 transcription factors leads to DUSP transcription. MAPKs also promote the stability of DUSP mRNA in the cytoplasm. b | Protein stability and catalytic activity of DUSPs is highly regulated through binding to MAPK substrates in both negative and positive ways. MAPK binding to DUSPs can increase protein stablility to provide feedback to MAPK activity44. Sometimes however, as is the case for DUSP1, MAPK binding can decrease protein stability and promote DUSP1 proteolysis through the ubiquitin ligase SCFSkp2, thereby sustaining MAPK activity45. c | Reactive oxygen species (ROS) that regulate some immune responses and activate the upstream kinase MAP3K5 (also known as ASK1) directly inactivate catalytic sites (at the conserved cysteine 257) of DUSPs. d | The temporal control of MAPKs results in varied cellular responses. The induction of DUSP expression and activity correlates with high MAPK activity to control the sustained or late phase of MAPK activity that is crucial for inducing IEGs and forming transcription factor complexes. Red arrows indicate positive regulation and green arrows indicate negative regulation in the tight regulation loops between MAPKs and DUSPs. CBP, CREB-binding protein (also known as CREBBP); MAP2K, MAPK kinase; MAP3K, MAP2K kinase; NFAT, nuclear factor of activated T cells. Figure 3: Phosphatases that regulate MAPKs.Of the 159 phosphatases identified in the human genome that operate in signal transduction, 106 of these are considered to be protein tyrosine phosphatases (PTPs). This PTP superfamily is further subdivided into 7 categories that are based on structural homology and substrate preference. These categories are: protein tyrosine phosphatase (PTPs), dual-specificity phosphatases (DUSPs), myotuberlarin-related phosphatases (MTMs), CDC25 phosphatases, low molecular weight (LMW) phosphatases, inositol-4-phosphatases (Inos.4P) and SAC1-domain phosphatases55, 143. PTPs and some serine/threonine phosphatases (PPs) show activity towards mitogen-activated protein kinases (MAPKs) by dephosphorylating single tyrosine or threonine residues. Class I DUSPs have activity towards MAPKs by dephosphorylating both tyrosine and threonine residues and are further subclassified into CH2-motif containing MAPK phosphatases (MKPs), JSP1-like phosphatases, MKP6-like, VHR-like, slingshot-like and SKPR1/ hyVH1. PPM, protein phosphatases, magnesium dependent; PPP, phosphoprotein phosphatases.
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References
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    • . . . Inhibitors of other pathways, such as the nuclear factor-κB (NF-κB) pathway, are also showing promise in clinical trials2 . . .
    • . . . Also noteworthy is the calcineurin phosphatase inhibitor cyclosporin — which regulates NFAT (nuclear factor of activated T cells) signalling and has proved to be a highly successful immunosuppressant for allo-graft rejection and inflammatory disorders, particularly psoriasis2, 3 — and of course blockbuster drugs such as the tyrosine kinase inhibitor imatinib (Gleevec; Novartis) . . .
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    • . . . Finally, glucocorticoids that are used widely to treat various inflammatory conditions have anti-inflammatory effects that are due in part to the induction of dual-specificity phosphatase 1 (DUSP1), a regulator of the MAPK pathway that negatively regulates pro-inflammatory gene expression in macrophages4, 5 . . .
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    • . . . Finally, glucocorticoids that are used widely to treat various inflammatory conditions have anti-inflammatory effects that are due in part to the induction of dual-specificity phosphatase 1 (DUSP1), a regulator of the MAPK pathway that negatively regulates pro-inflammatory gene expression in macrophages4, 5 . . .
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    • . . . The evolutionarily conserved MAPK pathway is present in yeast and all other eukaryotes and is a major signalling pathway in many cell types, particularly in immune cells6, 7, 8, 9 . . .
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    • . . . JNK is involved in Fas-mediated cell death as well as Bax-mediated apoptosis by releasing Bim to suppress the pro-survival factors BCL-2 and BCL-XL, while ERK-mediated phosphorylation of Bim inhibits its pro-apoptotic function and marks it for proteasomal degradation7, 26. . . .
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    • . . . The roles of extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) isoforms of MAPKs have been studied extensively in T cells, in particular for T-cell development in the thymus10, 11, 12, 13, CD4+ T-cell differentiation to T helper 1 (TH1) and TH2 cells14, 15, 16, and T-cell proliferation . . .
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    • . . . The roles of extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK) isoforms of MAPKs have been studied extensively in T cells, in particular for T-cell development in the thymus10, 11, 12, 13, CD4+ T-cell differentiation to T helper 1 (TH1) and TH2 cells14, 15, 16, and T-cell proliferation . . .
    • . . . ERK has a proposed role in T-cell anergy, promotes TH2-cell differentiation and is needed for thymocyte maturation6, 15. p38 MAPKs control production of interferon-γ (IFNG)14 and apoptosis of certain T-cell subsets17 . . .
    • . . . The MAP3K (MAPK kinase kinase) TPL2 (also known as MAP3K8) and ERK promote the transport of mRNA for tumour-necrosis factor (TNF) from the nucleus to the cytoplasm but have no effect on transcription of the TNF gene or on the stabilization of TNF mRNA following toll-like receptor 4 (TLR4) activation in macrophages19. p38 is probably involved in the initiation of TNF translation by the ARE region20. p38 also promotes transcriptional activation of the interleukin genes IL1A and IL1B in lipopolysaccharide-stimulated macrophages21, and specifically regulates IL-12 (Ref. 6) and IFNG14 production in certain cells . . .
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    • . . . ERK has a proposed role in T-cell anergy, promotes TH2-cell differentiation and is needed for thymocyte maturation6, 15. p38 MAPKs control production of interferon-γ (IFNG)14 and apoptosis of certain T-cell subsets17 . . .
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    • . . . ERK has a proposed role in T-cell anergy, promotes TH2-cell differentiation and is needed for thymocyte maturation6, 15. p38 MAPKs control production of interferon-γ (IFNG)14 and apoptosis of certain T-cell subsets17 . . .
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    • . . . This is achieved through the activation of nuclear transcription factors, and through the stabilization of inflammatory cytokine mRNA using adenosine-uridine-rich elements (AREs)18, 19 . . .
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    • . . . This is achieved through the activation of nuclear transcription factors, and through the stabilization of inflammatory cytokine mRNA using adenosine-uridine-rich elements (AREs)18, 19 . . .
    • . . . The MAP3K (MAPK kinase kinase) TPL2 (also known as MAP3K8) and ERK promote the transport of mRNA for tumour-necrosis factor (TNF) from the nucleus to the cytoplasm but have no effect on transcription of the TNF gene or on the stabilization of TNF mRNA following toll-like receptor 4 (TLR4) activation in macrophages19. p38 is probably involved in the initiation of TNF translation by the ARE region20. p38 also promotes transcriptional activation of the interleukin genes IL1A and IL1B in lipopolysaccharide-stimulated macrophages21, and specifically regulates IL-12 (Ref. 6) and IFNG14 production in certain cells . . .
  20. Lee, J. C. et al. A protein kinase involved in the regulation of inflammatory cytokine biosynthesis. Nature 372, 739-746 (1994) , .
    • . . . The MAP3K (MAPK kinase kinase) TPL2 (also known as MAP3K8) and ERK promote the transport of mRNA for tumour-necrosis factor (TNF) from the nucleus to the cytoplasm but have no effect on transcription of the TNF gene or on the stabilization of TNF mRNA following toll-like receptor 4 (TLR4) activation in macrophages19. p38 is probably involved in the initiation of TNF translation by the ARE region20. p38 also promotes transcriptional activation of the interleukin genes IL1A and IL1B in lipopolysaccharide-stimulated macrophages21, and specifically regulates IL-12 (Ref. 6) and IFNG14 production in certain cells . . .
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    • . . . The MAP3K (MAPK kinase kinase) TPL2 (also known as MAP3K8) and ERK promote the transport of mRNA for tumour-necrosis factor (TNF) from the nucleus to the cytoplasm but have no effect on transcription of the TNF gene or on the stabilization of TNF mRNA following toll-like receptor 4 (TLR4) activation in macrophages19. p38 is probably involved in the initiation of TNF translation by the ARE region20. p38 also promotes transcriptional activation of the interleukin genes IL1A and IL1B in lipopolysaccharide-stimulated macrophages21, and specifically regulates IL-12 (Ref. 6) and IFNG14 production in certain cells . . .
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    • . . . JNK regulates paxillin, a cytoskeletal protein involved in cell motility, to control cell migration22; p38 mediates signalling through both C5AR1 (the complement component C5a receptor 1) and CXCR4 (CXC-chemokine receptor 4)23 and controls cell directionality through its downstream substrate MAPK-activated protein kinase 2/3 (MAPKAPK2/3)24 . . .
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    • . . . JNK regulates paxillin, a cytoskeletal protein involved in cell motility, to control cell migration22; p38 mediates signalling through both C5AR1 (the complement component C5a receptor 1) and CXCR4 (CXC-chemokine receptor 4)23 and controls cell directionality through its downstream substrate MAPK-activated protein kinase 2/3 (MAPKAPK2/3)24 . . .
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    • . . . JNK regulates paxillin, a cytoskeletal protein involved in cell motility, to control cell migration22; p38 mediates signalling through both C5AR1 (the complement component C5a receptor 1) and CXCR4 (CXC-chemokine receptor 4)23 and controls cell directionality through its downstream substrate MAPK-activated protein kinase 2/3 (MAPKAPK2/3)24 . . .
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    • . . . Similarly, ERK governs cell motility through its ability to control both cell adhesion and detachment at the trailing end25 . . .
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    • . . . JNK is involved in Fas-mediated cell death as well as Bax-mediated apoptosis by releasing Bim to suppress the pro-survival factors BCL-2 and BCL-XL, while ERK-mediated phosphorylation of Bim inhibits its pro-apoptotic function and marks it for proteasomal degradation7, 26. . . .
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    • . . . Recently, a role for ERK was established for integrating signals in TLR4-driven plasma cell differentiation27, but B-cell phenotypes have yet to be reported in MAPK-deficient mice. . . .
  28. Reth, M. & Brummer, T. Feedback regulation of lymphocyte signalling. Nature Rev. Immunol. 4, 269-278 (2004) , .
    • . . . MAPK signalling was initially viewed as a relatively simple linear receptor-to-nucleus pathway, but new knowledge from the last 5 years demonstrates a reversible phosphorylation of kinases in multiple cascades controlled by many feedback loops and much crosstalk with other pathways28, 29, 30, 31 . . .
    • . . . There is also now an increased understanding of the feedback loops28, 37 and crosstalk within the MAPK pathway and with other pathways that assist in the amplification, diversification and termination of the MAPK signal . . .
  29. Cheung, P. C., Campbell, D. G., Nebreda, A. R. & Cohen, P. Feedback control of the protein kinase TAK1 by SAPK2a/p38. EMBO J. 22, 5793-5805 (2003).This paper shows the importance of feedback control of p38 and JNK and why inhibition of p38 may activate JNK pathways , .
    • . . . MAPK signalling was initially viewed as a relatively simple linear receptor-to-nucleus pathway, but new knowledge from the last 5 years demonstrates a reversible phosphorylation of kinases in multiple cascades controlled by many feedback loops and much crosstalk with other pathways28, 29, 30, 31 . . .
    • . . . This feedback control limits the activation of p38, as well as downstream components such as JNK and IKK (inhibitor of NF-κB kinase kinase), and synchronizes the three pathways29 . . .
    • . . . However, inhibition of p38 disrupts this feedback and causes the activation of the JNK and IKK pathways, which themselves are pro-inflammatory and may lead to unwanted side effects29 . . .
  30. Friedman, A. & Perrimon, N. A functional RNAi screen for regulators of receptor tyrosine kinase and ERK signalling. Nature 444, 230-234 (2006) , .
    • . . . MAPK signalling was initially viewed as a relatively simple linear receptor-to-nucleus pathway, but new knowledge from the last 5 years demonstrates a reversible phosphorylation of kinases in multiple cascades controlled by many feedback loops and much crosstalk with other pathways28, 29, 30, 31 . . .
    • . . . Examples of crosstalk include the ERK-dependent inhibition of p38 following exposure to transforming growth factor-β1 (TGFB1) to inhibit inflammatory cytokine production38 and the sustained activation of JNK, which blocks ERK activation in response to mitogenic stimuli30, 31, 39 . . .
  31. Jeffrey, K. L. et al. Positive regulation of immune cell function and inflammatory responses by phosphatase PAC-1. Nature Immunol. 7, 274-283 (2006).The first description of DUSP2-deficient mice and positive regulation of immune responses by a DUSP. Also highlights the importance of in vivo analysis of DUSP proteins , .
    • . . . MAPK signalling was initially viewed as a relatively simple linear receptor-to-nucleus pathway, but new knowledge from the last 5 years demonstrates a reversible phosphorylation of kinases in multiple cascades controlled by many feedback loops and much crosstalk with other pathways28, 29, 30, 31 . . .
    • . . . Examples of crosstalk include the ERK-dependent inhibition of p38 following exposure to transforming growth factor-β1 (TGFB1) to inhibit inflammatory cytokine production38 and the sustained activation of JNK, which blocks ERK activation in response to mitogenic stimuli30, 31, 39 . . .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
    • . . . The diverse expression patterns of the many DUSPs in different immune cell types have been analysed recently31, 73, 79 . . .
    • . . . Nuclear DUSPs (DUSP1, DUSP2, DUSP4 and DUSP5) show the most dramatic transcriptional regulation, at least in leukocytes31 . . .
    • . . . On the other hand, DUSP2 is highly transcriptionally regulated, but is exclusive to immune cells31. . . .
    • . . . For instance, although Dusp10−/− T cells had elevated JNK activity (as predicted from in vitro studies), there was no change in p38 activity61; Dusp1−/− macrophages had elevated p38 and JNK activity but no change in ERK activity despite in vitro evidence that demonstrates an equal preference for all three62, 96, 97; DUSP3 had little activity towards MAPK in vitro, but had elevated ERK and JNK activity following RNA interference70; and Dusp2−/− macrophages and mast cells showed a surprising reduction in ERK and p38 activity but elevated JNK activity, highlighting the co-dependence of certain DUSPs and the strong influence of MAPK crosstalk31 (Table 1). . . .
    • . . . This resulted in reduced inflammatory mediator production from these cells, which could be rescued through reconstitution with phosphatase-active DUSP2 (Ref. 31) . . .
    • . . . Dusp2−/− mice were protected in the KxB/N model of inflammatory arthritis, which is dependent on mast cell and macrophage activation31. . . .
  32. Murphy, L. O., Smith, S., Chen, R. H., Fingar, D. C. & Blenis, J. Molecular interpretation of ERK signal duration by immediate early gene products. Nature Cell Biol. 4, 556-564 (2002) , .
    • . . . The distinct biological outcomes are often achieved purely because of the duration of MAPK activity, as immediate early genes act as sensors to the MAPK signal32 . . .
  33. Volmat, V., Camps, M., Arkinstall, S., Pouyssegur, J. & Lenormand, P. The nucleus, a site for signal termination by sequestration and inactivation of p42/p44 MAP kinases. J. Cell Sci. 114, 3433-3443 (2001) , .
    • . . . Spatial arrangement and compartmentalization are also important aspects, whereby the nucleus acts as an essential site for signal termination by sequestering the MAPKs away from their cytoplasmic activators and aligning them with nuclear phosphatases33, 34 . . .
  34. Pouyssegur, J., Volmot, V. & Lenormand, P. Fidelity and spatio-temporal control in MAP kinase (ERKs) signalling. Biochem. Pharm. 64, 755-763 (2002) , .
    • . . . Spatial arrangement and compartmentalization are also important aspects, whereby the nucleus acts as an essential site for signal termination by sequestering the MAPKs away from their cytoplasmic activators and aligning them with nuclear phosphatases33, 34 . . .
    • . . . In addition, spatial localization of MAPKs also determines the sensitivity of the MAPK module to various stimuli34, 35, as well as the specific cellular outputs by subcellular-specific substrates36 . . .
  35. Harding, A., Tian, T., Westbury, E., Frische, E. & Hancock, J. F. Subcellular localization determines MAP kinase signal output. Curr. Biol. 15, 869-873 (2005) , .
    • . . . In addition, spatial localization of MAPKs also determines the sensitivity of the MAPK module to various stimuli34, 35, as well as the specific cellular outputs by subcellular-specific substrates36 . . .
  36. Hazzalin, C. A. & Mahadevan, L. C. MAPK-regulated transcription: a continuously variable gene switch? Nature Rev. Mol. Cell Biol. 3, 30-40 (2002) , .
    • . . . In addition, spatial localization of MAPKs also determines the sensitivity of the MAPK module to various stimuli34, 35, as well as the specific cellular outputs by subcellular-specific substrates36 . . .
  37. Zimmermann, S. et al. MEK1 mediates a positive feedback on Raf-1 activity independently of Ras and Src. Oncogene 15, 1503-1511 (1997) , .
    • . . . There is also now an increased understanding of the feedback loops28, 37 and crosstalk within the MAPK pathway and with other pathways that assist in the amplification, diversification and termination of the MAPK signal . . .
  38. Xiao, Y. Q. et al. Cross-talk between ERK and p38 MAPK mediates selective suppression of pro-inflammatory cytokines by transforming growth factor-. J. Biol. Chem. 277, 14884-14893 (2002) , .
    • . . . Examples of crosstalk include the ERK-dependent inhibition of p38 following exposure to transforming growth factor-β1 (TGFB1) to inhibit inflammatory cytokine production38 and the sustained activation of JNK, which blocks ERK activation in response to mitogenic stimuli30, 31, 39 . . .
  39. Shen, Y. H. et al. Cross-talk between JNK/SAPK and ERK/MAPK pathways: sustained activation of JNK blocks ERK activation by mitogenic factors. J. Biol. Chem. 278, 26715-26721 (2003) , .
    • . . . Examples of crosstalk include the ERK-dependent inhibition of p38 following exposure to transforming growth factor-β1 (TGFB1) to inhibit inflammatory cytokine production38 and the sustained activation of JNK, which blocks ERK activation in response to mitogenic stimuli30, 31, 39 . . .
  40. Rommel, C. et al. Differentiation stage-specific inhibition of the Raf-MEK-ERK pathway by Akt. Science 286, 1738-1741 (1999) , .
    • . . . MAPKs also display crosstalk with other pathways, such as the JAK–STAT (Janus kinase–signal transducer and activator of transcription) and PI3K (phosphatidylinositol 3-kinase) pathways40, 41 . . .
  41. Zimmermann, S. & Moelling, K. Phosphorylation and regulation of Raf by Akt (protein kinase B). Science 286, 1741-1744 (1999) , .
    • . . . MAPKs also display crosstalk with other pathways, such as the JAK–STAT (Janus kinase–signal transducer and activator of transcription) and PI3K (phosphatidylinositol 3-kinase) pathways40, 41 . . .
  42. Reth, M. Hydrogen peroxide as second messenger in lymphocyte activation. Nature Immunol. 3, 1129-1134 (2002) , .
    • . . . From a biochemical perspective, the enzymatic power of a phosphatase is as much as 100 to 1,000 times as great as that of a kinase, owing to the fact that kinases require ATP and therefore use a second-order reaction, whereas dephosphorylation is direct42 . . .
  43. Grumont, R. J., Rasko, J. E. J., Strasser, A., Gerondakis, S. Activation of the mitogen-activated protein kinase pathway induces transription of the PAC-1 phosphatase gene. Mol. Cell. Biol. 16, 2913-2921 (1996) , .
    • . . . Strong transcriptional induction and protein stabilization of phosphatases — both a result of MAPK activity43, 44, 45, 46, 47 — as well as the control of their activity by reversible oxidation48, 49 are illustrative of this (Fig. 2) . . .
    • . . . This induction is also dependent on MAPK activation and is thought to be a mechanism for the attenuation of mitogenic signalling43, 46, 80 . . .
  44. Camps, M. et al. Catalytic activation of the phosphatase MKP-3 by ERK2 mitogen-activated protein kinase. Science 280, 1262-1265 (1998).The first paper to describe the feedback control of DUSP catalytic activity by MAPKs , .
  45. Lin, Y. W. & Yang, J. L. Cooperation of ERK and SCFSkp2 for MKP-1 destruction provides a positive feedback regulation of proliferating signaling. J. Biol. Chem. 281, 915-926 (2006) , .
  46. Brondello, J.-M., Brunet, A., Pouyssegur, J. & McKenzie, F. R. The dual specificity mitogen-activated protein kinase phosphatase-1 and-2 are induced by p42/p44 MAPK cascade. J. Biol. Chem. 272, 1368-1376 (1997) , .
    • . . . Strong transcriptional induction and protein stabilization of phosphatases — both a result of MAPK activity43, 44, 45, 46, 47 — as well as the control of their activity by reversible oxidation48, 49 are illustrative of this (Fig. 2) . . .
    • . . . This induction is also dependent on MAPK activation and is thought to be a mechanism for the attenuation of mitogenic signalling43, 46, 80 . . .
  47. Brondello, J. M., Pouyssegur, J. & McKenzie, F. R. Reduced MAP kinase phosphatase-1 degradation after p42/p44MAPK-dependent phosphorylation. Science 286, 2514-2517 (1999).Describes the control of DUSP protein stability by MAPKs , .
    • . . . Strong transcriptional induction and protein stabilization of phosphatases — both a result of MAPK activity43, 44, 45, 46, 47 — as well as the control of their activity by reversible oxidation48, 49 are illustrative of this (Fig. 2) . . .
    • . . . However, through a negative-feedback mechanism, ERK can induce stabilization of DUSP1 by direct phosphorylation, which leads to reduced ubiquitylation and proteasomal degradation47 . . .
  48. Kamata, H. et al. Reactive oxygen species promote TNF-induced death and sustained JNK activation by inhibiting MAP kinase phosphatases. Cell 120, 649-661 (2005) , .
    • . . . Strong transcriptional induction and protein stabilization of phosphatases — both a result of MAPK activity43, 44, 45, 46, 47 — as well as the control of their activity by reversible oxidation48, 49 are illustrative of this (Fig. 2) . . .
    • . . . Indeed, TNF-induced cell death is promoted by reactive oxygen species that specifically inhibit the cysteine residue at the catalytic site of DUSPs, to increase JNK activity48 . . .
  49. Salmeen, A. et al. Redox regulation of protein tyrosine phosphatase 1B involves a sulphenyl-amide intermediate. Nature 423, 769-773 (2003) , .
    • . . . Strong transcriptional induction and protein stabilization of phosphatases — both a result of MAPK activity43, 44, 45, 46, 47 — as well as the control of their activity by reversible oxidation48, 49 are illustrative of this (Fig. 2) . . .
    • . . . Enzymatic deactivation of phosphatases also occurs by the action of reactive oxygen species that have been shown to reversibly oxidize the conserved catalytic site cysteine in PTPs and inactivate their enzymatic activity49, 91 . . .
  50. Bhalla, U. S., Ram, P. T. & Iyengar, R. MAP kinase phosphatase as a locus of flexibility in a mitogen-activated protein kinase signaling network. Science 297, 1018-1023 (2002).A computational analysis highlighting the DUSPs as the control point of the MAPK signalling network , .
    • . . . Interestingly, a computational analysis of the MAPK system suggests that DUSPs, and not the kinases, dictate the extent of MAPK phosphorylation following cellular activation50 . . .
  51. Masuda, K., Shima, H., Watanabe, M. & Kikuchi, K. MKP-7, a novel mitogen-activated protein kinase phosphatase, functions as a shuttle protein. J. Biol. Chem. 276, 39002-39011 (2001) , .
    • . . . Also, the influence of DUSPs extends beyond that of a dephosphorylating role, as some can shuttle or anchor MAPKs between the cytoplasm and nucleus51, 52. . . .
    • . . . In addition to their differing patterns of tissue expression, DUSPs show differing subcellular localizations (that is, cytosolic versus nuclear), which suggests that they regulate the activity of specific pools of MAPKs51, 52. . . .
    • . . . DUSP16, which contains both a nuclear localization signal and a nuclear export signal, can transport both p38 and JNK from the nucleus to the cytoplasm51 . . .
    • . . . By contrast, DUSP8, DUSP10 and DUSP16 have little activity for ERK and seem to prefer JNK and p38 kinases51, 75, 76, 92, 93 . . .
  52. Karlsson, M., Mathers, J., Dickinson, R. J., Mandl, M. & Keyse, S. M. Both nuclear-cytoplasmic shuttling of the dual specificity phosphatase MKP-3 and its ability to anchor MAP kinase in the cytoplasm are mediated by a conserved nuclear export signal. J. Biol. Chem. 279, 41882-41891 (2004).References 51 and 52 were the first to describe a role for DUSPs in controlling MAPK subcellular localization , .
    • . . . Also, the influence of DUSPs extends beyond that of a dephosphorylating role, as some can shuttle or anchor MAPKs between the cytoplasm and nucleus51, 52. . . .
    • . . . In addition to their differing patterns of tissue expression, DUSPs show differing subcellular localizations (that is, cytosolic versus nuclear), which suggests that they regulate the activity of specific pools of MAPKs51, 52. . . .
    • . . . Similarly, DUSP6, a cytoplasmic DUSP that contains a nuclear export signal, causes the cytoplasmic retention of ERK2, which is dependent on both its nuclear export signal and its KIM motif that binds the MAPK52 . . .
  53. Canagarajah, B. J., Khokhlatchev, A., Cobb, M. H. & Goldsmith, E. J. Activation mechanism of the MAP kinase ERK2 by dual phosphorylation. Cell 90, 859-869 (1997) , .
    • . . . MAPKs are inactivated completely by dephosphorylation of either the tyrosine or threonine residues, or both53 . . .
  54. Camps, M., Nichols, A. & Arkinstall, S. Dual specificity phosphatases: a gene family for control of MAP kinase function. FASEB J. 14, 6-16 (2000) , .
    • . . . In intact cells, dephosphorylation and inactivation of MAPKs occurs with kinetics that range from minutes to several hours depending on the cell type and activating stimulus54 . . .
    • . . . The phosphatases that can inactivate MAPKs include: the PTPs that hydrolyse phosphotyrosine residues on activated MAPKs; the serine/threonine phosphatases, referred to as protein phosphatases (PPs), that dephosphorylate threonine residues; and the class I family of DUSPs (also known as MAPK phosphatases, DSPs or MKPs) that dephosphorylate phosphotyrosine and threonine residues that are located in the same MAPK54, 57, 58, 59, 60 (Fig. 3) . . .
    • . . . The class I DUSPs regulate MAPK activity through 'TXY-motif' dephosphorylation and represent particularly important negative regulators of MAPK signalling54, 61, 62, 63 (Table 1). . . .
    • . . . Of these 11 are 'typical' MKPs that contain a CH2 motif for MAPK docking and comprise three major subfamilies that are based on their sequence similarity, substrate specificity and subcellular localization54, 64, 65, 66, 67 (Table 1) . . .
    • . . . They all share common features, including an extended active-site motif with high sequence similarity to the corresponding region of the VH1 protein tyrosine phosphatase that was isolated from vaccinia virus54 . . .
    • . . . The KIM confers substrate specificity and is the least homologous region demonstrating individual substrate preferences54, 67. . . .
    • . . . DUSP8, DUSP10 and DUSP16 make up the third subgroup as they preferentially recognize JNK, p38 or both, respectively54, 64, 67. . . .
  55. Alonso, A. et al. Protein tyrosine phosphatases in the human genome. Cell 117, 699-711 (2004) , .
  56. Andersen, J. N. et al. A genomic perspective on protein tyrosine phosphatases: gene structure, pseudogenes, and genetic disease linkage. FASEB J. 18, 8-30 (2004) , .
    • . . . Based on structural homology and substrate preference, this superfamily is divided into seven categories55, 56 (Fig. 3; see also the Protein Tyrosine Phosphatases web site) . . .
  57. Lyon, M. A., Ducruet, A. P., Wipf, P. & Lazo, J. S. Dual-specificity phosphatases as targets for antineoplastic agents. Nature Rev. Drug Discov. 1, 961-976 (2002) , .
    • . . . The phosphatases that can inactivate MAPKs include: the PTPs that hydrolyse phosphotyrosine residues on activated MAPKs; the serine/threonine phosphatases, referred to as protein phosphatases (PPs), that dephosphorylate threonine residues; and the class I family of DUSPs (also known as MAPK phosphatases, DSPs or MKPs) that dephosphorylate phosphotyrosine and threonine residues that are located in the same MAPK54, 57, 58, 59, 60 (Fig. 3) . . .
  58. Keyse, S. M. Protein phosphatases and the regulation of MAP kinase activity. Semin. Cell Dev. Biol. 9, 143-152 (1998) , .
    • . . . The phosphatases that can inactivate MAPKs include: the PTPs that hydrolyse phosphotyrosine residues on activated MAPKs; the serine/threonine phosphatases, referred to as protein phosphatases (PPs), that dephosphorylate threonine residues; and the class I family of DUSPs (also known as MAPK phosphatases, DSPs or MKPs) that dephosphorylate phosphotyrosine and threonine residues that are located in the same MAPK54, 57, 58, 59, 60 (Fig. 3) . . .
  59. Tonks, N. K. & Neel, B. G. From form to function: signaling by protein tyrosine phosphatases. Cell 87, 365-368 (1996) , .
    • . . . The phosphatases that can inactivate MAPKs include: the PTPs that hydrolyse phosphotyrosine residues on activated MAPKs; the serine/threonine phosphatases, referred to as protein phosphatases (PPs), that dephosphorylate threonine residues; and the class I family of DUSPs (also known as MAPK phosphatases, DSPs or MKPs) that dephosphorylate phosphotyrosine and threonine residues that are located in the same MAPK54, 57, 58, 59, 60 (Fig. 3) . . .
  60. Tonks, N. K. & Neel, B. G. Combinatorial control of the specificity of protein tyrosine phosphatases. Curr. Opin. Cell Biol. 13, 182-195 (2001) , .
    • . . . The phosphatases that can inactivate MAPKs include: the PTPs that hydrolyse phosphotyrosine residues on activated MAPKs; the serine/threonine phosphatases, referred to as protein phosphatases (PPs), that dephosphorylate threonine residues; and the class I family of DUSPs (also known as MAPK phosphatases, DSPs or MKPs) that dephosphorylate phosphotyrosine and threonine residues that are located in the same MAPK54, 57, 58, 59, 60 (Fig. 3) . . .
  61. Zhang, Y. et al. Regulation of innate and adaptive immune responses by MAP kinase phosphatase 5. Nature 430, 793-797 (2004).The first paper to describe a physiological role for a DUSP in vivo and a role for DUSPs in the immune system , .
    • . . . The class I DUSPs regulate MAPK activity through 'TXY-motif' dephosphorylation and represent particularly important negative regulators of MAPK signalling54, 61, 62, 63 (Table 1). . . .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
    • . . . For instance, although Dusp10−/− T cells had elevated JNK activity (as predicted from in vitro studies), there was no change in p38 activity61; Dusp1−/− macrophages had elevated p38 and JNK activity but no change in ERK activity despite in vitro evidence that demonstrates an equal preference for all three62, 96, 97; DUSP3 had little activity towards MAPK in vitro, but had elevated ERK and JNK activity following RNA interference70; and Dusp2−/− macrophages and mast cells showed a surprising reduction in ERK and p38 activity but elevated JNK activity, highlighting the co-dependence of certain DUSPs and the strong influence of MAPK crosstalk31 (Table 1). . . .
    • . . . DUSP10 was shown to be an important regulator of innate and adaptive immune responses mediated by the attenuation of JNK activity61 . . .
    • . . . Dusp10−/− mice exhibited an expected increase in cytokine production from macrophages after TLR stimulation, but also had an unexpected reduction in proliferation of T cells and protection in a model of experimental autoimmune encephalomyelitis61 . . .
  62. Chu, Y., Solski, P. A., Khosravi-Far, R., Der, C. J. & Kelly, K. The mitogen-activated protein kinase phosphatases PAC1, MKP-1, and MKP-2 have unique substrate specificities and reduced activity in vivo toward the ERK2 sevenmaker mutation. J. Biol. Chem. 271, 6497-6501 (1996) , .
    • . . . The class I DUSPs regulate MAPK activity through 'TXY-motif' dephosphorylation and represent particularly important negative regulators of MAPK signalling54, 61, 62, 63 (Table 1). . . .
    • . . . Thus, DUSP regulation of MAPKs may be cell-type and stimulus specific62, 94. . . .
    • . . . For example, although both DUSP2 and DUSP4 have a preference for ERK in vitro, DUSP4 dephosphorylates ERK much more efficiently than DUSP2 (Ref. 62) . . .
    • . . . For instance, although Dusp10−/− T cells had elevated JNK activity (as predicted from in vitro studies), there was no change in p38 activity61; Dusp1−/− macrophages had elevated p38 and JNK activity but no change in ERK activity despite in vitro evidence that demonstrates an equal preference for all three62, 96, 97; DUSP3 had little activity towards MAPK in vitro, but had elevated ERK and JNK activity following RNA interference70; and Dusp2−/− macrophages and mast cells showed a surprising reduction in ERK and p38 activity but elevated JNK activity, highlighting the co-dependence of certain DUSPs and the strong influence of MAPK crosstalk31 (Table 1). . . .
    • . . . Overexpression of the ubiquitous DUSP1, which dephosphorylates ERK, JNK and p38 (Ref. 62), has been found in several malignancies, including breast and prostate98, 99 . . .
  63. Ward, Y. et al. Control of MAP kinase activation by the mitogen-induced threonine/tyrosine phosphatase PAC1. Nature 367, 651-654 (1994) , .
    • . . . The class I DUSPs regulate MAPK activity through 'TXY-motif' dephosphorylation and represent particularly important negative regulators of MAPK signalling54, 61, 62, 63 (Table 1). . . .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
  64. Theodosiou, A. & Ashworth, A. MAP kinase phosphatases. Genome Biol. 3, 3009 (2002) , .
    • . . . Of these 11 are 'typical' MKPs that contain a CH2 motif for MAPK docking and comprise three major subfamilies that are based on their sequence similarity, substrate specificity and subcellular localization54, 64, 65, 66, 67 (Table 1) . . .
    • . . . In addition, the active site motif of all four of these DUSPs is encoded within exon 4 and the length of their exon 3 is identical, which is suggestive of a common ancenstral gene64, 67 . . .
    • . . . DUSP8, DUSP10 and DUSP16 make up the third subgroup as they preferentially recognize JNK, p38 or both, respectively54, 64, 67. . . .
  65. Keyse, S. M. An emerging family of dual specificity MAP kinase phosphatases. Biochim. Biophys. Acta 1265, 152-160 (1995) , .
    • . . . Of these 11 are 'typical' MKPs that contain a CH2 motif for MAPK docking and comprise three major subfamilies that are based on their sequence similarity, substrate specificity and subcellular localization54, 64, 65, 66, 67 (Table 1) . . .
  66. Keyse, S. M. The role of protein phosphatases in the regulation of mitogen and stress-activated protein kinases. Free Radic. Res. 31, 341-349 (1999) , .
    • . . . Of these 11 are 'typical' MKPs that contain a CH2 motif for MAPK docking and comprise three major subfamilies that are based on their sequence similarity, substrate specificity and subcellular localization54, 64, 65, 66, 67 (Table 1) . . .
  67. Keyse, S. M. Protein phosphatases and the regulation of mitogen-activated protein kinase signalling. Curr. Opin. Cell Biol. 12, 186-192 (2000) , .
    • . . . Of these 11 are 'typical' MKPs that contain a CH2 motif for MAPK docking and comprise three major subfamilies that are based on their sequence similarity, substrate specificity and subcellular localization54, 64, 65, 66, 67 (Table 1) . . .
    • . . . The KIM confers substrate specificity and is the least homologous region demonstrating individual substrate preferences54, 67. . . .
    • . . . In addition, the active site motif of all four of these DUSPs is encoded within exon 4 and the length of their exon 3 is identical, which is suggestive of a common ancenstral gene64, 67 . . .
    • . . . Most DUSPs are inducible genes with basal levels of DUSPs being mostly low in unstressed or unstimulated cells67 . . .
    • . . . By contrast, DUSP6, DUSP8, DUSP9 and DUSP10 are not encoded by immediate early genes67, 81 . . .
  68. Ishibashi, T., Bottaro, D. P., Chan, A., Miki, T. & Aaronson, S. A. Expression cloning of a human dual-specificity phosphatase. Proc. Natl Acad. Sci. USA 89, 12170-12174 (1992) , .
    • . . . DUSP3 (also known as VHR) is an additional mammalian homologue of VH1 (Ref. 68) but lacks the required N-terminal motif for MAPK binding and indeed appears to be relatively inactive against MAPKs in vitro69 . . .
  69. Shin, D. Y. et al. A novel human ERK phosphatase regulates H-ras and v-raf signal transduction. Oncogene 14, 2633-2639 (1997) , .
    • . . . DUSP3 (also known as VHR) is an additional mammalian homologue of VH1 (Ref. 68) but lacks the required N-terminal motif for MAPK binding and indeed appears to be relatively inactive against MAPKs in vitro69 . . .
  70. Rahmouni, S. et al. Loss of the VHR dual-specific phosphatase causes cell-cycle arrest and senescence. Nature Cell Biol. 8, 524-531 (2006) , .
    • . . . RNA interference of DUSP3 however had profound effects on the cell cycle mediated by JNK and ERK70 . . .
    • . . . For instance, although Dusp10−/− T cells had elevated JNK activity (as predicted from in vitro studies), there was no change in p38 activity61; Dusp1−/− macrophages had elevated p38 and JNK activity but no change in ERK activity despite in vitro evidence that demonstrates an equal preference for all three62, 96, 97; DUSP3 had little activity towards MAPK in vitro, but had elevated ERK and JNK activity following RNA interference70; and Dusp2−/− macrophages and mast cells showed a surprising reduction in ERK and p38 activity but elevated JNK activity, highlighting the co-dependence of certain DUSPs and the strong influence of MAPK crosstalk31 (Table 1). . . .
  71. Zama, T. et al. Scaffold role of a mitogen-activated protein kinase phosphatase, SKRP1, for the JNK signaling pathway. J. Biol. Chem. 277, 23919-23926 (2002) , .
    • . . . Additional members of this class I subfamily of DUSPs include stress-activated protein kinase (SAPK) pathway-regulating phosphatase 1 (SKRP1), which lacks the CDC25 domain but contains the conserved active-site sequence and can inactivate JNK through its binding to the upstream JNK-activator MKK4/7 (Refs 71,72). . . .
  72. Zama, T. et al. A novel dual specificity phosphatase SKRP1 interacts with the MAPK kinase MKK7 and inactivates the JNK MAPK pathway. Implication for the precise regulation of the particular MAPK pathway. J. Biol. Chem. 277, 23909-23918 (2002) , .
    • . . . Additional members of this class I subfamily of DUSPs include stress-activated protein kinase (SAPK) pathway-regulating phosphatase 1 (SKRP1), which lacks the CDC25 domain but contains the conserved active-site sequence and can inactivate JNK through its binding to the upstream JNK-activator MKK4/7 (Refs 71,72). . . .
  73. Hammer, M. et al. Control of dual-specificity phosphatase-1 expression in activated macrophages by IL-10. Eur. J. Immunol. 35, 2991-3001 (2005) , .
    • . . . For instance, activated macrophages express several DUSPs73 . . .
    • . . . The diverse expression patterns of the many DUSPs in different immune cell types have been analysed recently31, 73, 79 . . .
  74. Rohan, P. J. et al. PAC-1: A mitogen-induced nuclear protein tyrosine phosphatase. Science 259, 1763-1766 (1993) , .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
  75. Muda, M. et al. The dual specificity phosphatases M3/6 and MKP-3 are highly selective for inactivation of distinct mitogen-activated protein kinases. J. Biol. Chem. 271, 27205-27208 (1996) , .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
    • . . . By contrast, DUSP8, DUSP10 and DUSP16 have little activity for ERK and seem to prefer JNK and p38 kinases51, 75, 76, 92, 93 . . .
  76. Tanoue, T., Moriguchi, T. & Nishida, E. Molecular cloning and characterization of a novel dual specificity phosphatase, MKP-5. J. Biol. Chem. 274, 19949-19956 (1999) , .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
    • . . . By contrast, DUSP8, DUSP10 and DUSP16 have little activity for ERK and seem to prefer JNK and p38 kinases51, 75, 76, 92, 93 . . .
  77. Muda, M. et al. Molecular cloning and functional characterization of a novel mitogen-activated protein kinase phosphatase, MKP-4. J. Biol. Chem. 272, 5141-5151 (1997) , .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
    • . . . DUSP9 is high in kidney (as previously described77) and intermediate in most leukocyte types . . .
    • . . . Similarly, DUSP9 seems to have a preference for ERK over other MAPKs77 . . .
  78. Christie, G. R. et al. The dual-specificity protein phosphatase DUSP9/MKP-4 is essential for placental function but is not required for normal embryonic development. Mol. Cell. Biol. 25, 8323-8333 (2005) , .
    • . . . For instance, DUSP2 is enriched in haematopoietic cells31, 63, 74; DUSP8 appears to be expressed predominantly in brain, heart and skeletal muscle75; DUSP10 is expressed ubiquitously, but is more abundant in cerebellum, skeletal muscle and bone marrow, and is transcriptionally regulated in macrophages61, 76; whereas DUSP9 is found only in placenta, kidney and embryonic liver77, 78. . . .
    • . . . DUSP9 is required for placental development, but its absence appears not to influence MAPK phosphorylation78 . . .
  79. Tanzola, M. B. & Kersh, G. J. The dual specificity phosphatase transcriptome of the murine thymus. Mol. Immunol. 43, 754-762 (2006) , .
    • . . . The diverse expression patterns of the many DUSPs in different immune cell types have been analysed recently31, 73, 79 . . .
  80. Dowd, S., Sneddon, A. A. & Keyse, S. M. Isolation of the human genes encoding the pyst1 and Pyst2 phosphatases: characterisation of Pyst2 as a cytosolic dual-specificity MAP kinase phosphatase and its catalytic activation by both MAP and SAP kinases. J. Cell Sci. 111, 3389-3399 (1998) , .
    • . . . This induction is also dependent on MAPK activation and is thought to be a mechanism for the attenuation of mitogenic signalling43, 46, 80 . . .
    • . . . For example, DUSP1 is induced by mitogens, oxidative stress, heat shock82 and hypoxia83, 84, whereas DUSP7 is induced only moderately by serum and not by cellular stress80 . . .
  81. Camps, M. et al. Induction of the mitogen-activated protein kinase phosphatase MKP3 by nerve growth factor in differentiating PC12. FEBS Lett. 425, 271-276 (1998) , .
    • . . . By contrast, DUSP6, DUSP8, DUSP9 and DUSP10 are not encoded by immediate early genes67, 81 . . .
    • . . . Moreover, although DUSP6 expression is not induced by either mitogens or cellular stresses85, 86, its expression can be increased by agents that promote neuronal differentiation81 . . .
  82. Keyse, S. M. & Emslie, E. A. Oxidative stress and heat shock induce a human gene encoding a protein-tyrosine phosphatase. Nature 359, 644-647 (1992) , .
    • . . . For example, DUSP1 is induced by mitogens, oxidative stress, heat shock82 and hypoxia83, 84, whereas DUSP7 is induced only moderately by serum and not by cellular stress80 . . .
  83. Laderoute, K. R. et al. Mitogen-activated protein kinase phosphatase-1 (MKP-1) expression is induced by low oxygen conditions found in solid tumor microenvironments. A candidate MKP for the inactivation of hypoxia-inducible stress-activated protein kinase/c-Jun N-terminal protein kinase activity. J. Biol. Chem. 274, 12890-12897 (1999) , .
    • . . . For example, DUSP1 is induced by mitogens, oxidative stress, heat shock82 and hypoxia83, 84, whereas DUSP7 is induced only moderately by serum and not by cellular stress80 . . .
  84. Seta, K. A., Kim, R., Kim, H. W., Millhorn, D. E. & Beitner-Johnson, D. Hypoxia-induced regulation of MAPK phosphatase-1 as identified by subtractive suppression hybridization and cDNA microarray analysis. J. Biol. Chem. 276, 44405-44412 (2001) , .
    • . . . For example, DUSP1 is induced by mitogens, oxidative stress, heat shock82 and hypoxia83, 84, whereas DUSP7 is induced only moderately by serum and not by cellular stress80 . . .
  85. Groom, L. A., Sneddon, A. A., Alessi, D. R., Dowd, S. & Keyse, S. M. Differential regulation of the MAP, SAP and RK/p38 kinases by Pyst1, a novel cytosolic dual-specificity phosphatase. EMBO J. 15, 3621-3632 (1996) , .
    • . . . Moreover, although DUSP6 expression is not induced by either mitogens or cellular stresses85, 86, its expression can be increased by agents that promote neuronal differentiation81 . . .
    • . . . For example, DUSP6 is 100-fold more active towards ERK2 than p38 or JNK85 . . .
  86. Muda, M. et al. MKP-3, a novel cytosolic protein-tyrosine phosphatase that exemplifies a new class of mitogen-activated protein kinase phosphatase. J. Biol. Chem. 271, 4319-4326 (1996) , .
    • . . . Moreover, although DUSP6 expression is not induced by either mitogens or cellular stresses85, 86, its expression can be increased by agents that promote neuronal differentiation81 . . .
  87. Fjeld, C. C., Rice, A. E., Kim, Y., Gee, K. R. & Denu, J. M. Mechanistic basis for catalytic activation of mitogen-activated protein kinase phosphatase 3 by extracellular signal-regulated kinase. J. Biol. Chem. 275, 6749-6757 (2000) , .
    • . . . DUSP6 experiences a 25-fold increase in catalytic activity when complexed to its phosphorylated substrate, ERK2 (Ref. 87) . . .
    • . . . For example, ERK2 binding to DUSP6 via the conserved XXRRXXKXXLXV in the N-terminal kinase binding domain95 stabilizes the active conformation of the active site cysteine115 and results in an approximately 100-fold increase in enzymatic activity44, 87, 99 . . .
  88. Slack, D. N., Seternes, O. M., Gabrielsen, M. & Keyse, S. M. Distinct binding determinants for ERK2/p38 and JNK map kinases mediate catalytic activation and substrate selectivity of map kinase phosphatase-1. J. Biol. Chem. 276, 16491-16500 (2001) , .
    • . . . Similarly, DUSP1 catalytic activation is mediated by physical interactions with ERK2, JNK1 and p38 in vitro88 and DUSP2 enzymatic activity, which is virtually inactive when alone in vitro, is also enhanced upon binding to ERK2 through its N-terminal domain89, 90 . . .
  89. Farooq, A. et al. Solution structure of the MAPK phosphatase PAC-1 catalytic domain. insights into substrate-induced enzymatic activation of MKP. Structure 11, 155-164 (2003) , .
    • . . . Similarly, DUSP1 catalytic activation is mediated by physical interactions with ERK2, JNK1 and p38 in vitro88 and DUSP2 enzymatic activity, which is virtually inactive when alone in vitro, is also enhanced upon binding to ERK2 through its N-terminal domain89, 90 . . .
    • . . . The active sites of PTPs are ~9 Å (Ref. 114), whereas those of the DUSPs tend to be shallower at ~6 Å (Refs 89,115) . . .
  90. Zhang, Q. et al. New insights into the catalytic activation of the MAPK phosphatase PAC-1 induced by its substrate MAPK ERK2 binding. J. Mol. Biol. 354, 777-788 (2005) , .
    • . . . Similarly, DUSP1 catalytic activation is mediated by physical interactions with ERK2, JNK1 and p38 in vitro88 and DUSP2 enzymatic activity, which is virtually inactive when alone in vitro, is also enhanced upon binding to ERK2 through its N-terminal domain89, 90 . . .
  91. Meng, T. C., Fukada, T. & Tonks, N. K. Reversible oxidation and inactivation of protein tyrosine phosphatases in vivo. Mol. Cell 9, 387-399 (2002).An important demonstration of catalytic inactivation of phosphatases by reversible oxidation , .
    • . . . Enzymatic deactivation of phosphatases also occurs by the action of reactive oxygen species that have been shown to reversibly oxidize the conserved catalytic site cysteine in PTPs and inactivate their enzymatic activity49, 91 . . .
  92. Tanoue, T., Yamamoto, T., Maeda, R. & Nishida, E. A novel MAPK phosphatase MKP-7 acts preferentially on JNK/SAPK and p38 and MAPKs. J. Biol. Chem. 276, 26629-26639 (2001) , .
    • . . . By contrast, DUSP8, DUSP10 and DUSP16 have little activity for ERK and seem to prefer JNK and p38 kinases51, 75, 76, 92, 93 . . .
  93. Theodosiou, A., Smith, A., Gillieron, C., Arkinstall, S. & Ashworth, A. MKP5, a new member of the MAP kinase phosphatase family, which selectively dephosphorylates stress-activated kinases. Oncogene 18, 6981-6988 (1999) , .
    • . . . By contrast, DUSP8, DUSP10 and DUSP16 have little activity for ERK and seem to prefer JNK and p38 kinases51, 75, 76, 92, 93 . . .
  94. Hirsch, D. D. & Stork, P. J. Mitogen-activated protein kinase phosphatases inactivate stress-activated protein kinase pathways in vivo. J. Biol. Chem. 272, 4568-4575 (1997) , .
    • . . . Thus, DUSP regulation of MAPKs may be cell-type and stimulus specific62, 94. . . .
  95. Nichols, A. et al. Substrate recognition domains within extracellular signal-regulated kinase mediate binding and catalytic activation of mitogen-activated protein kinase phosphatase-3. J. Biol. Chem. 275, 24613-24621 (2000) , .
    • . . . The substrate specificity of the various DUSPs may reside in their heterogeneous KIM docking site95 . . .
    • . . . For example, ERK2 binding to DUSP6 via the conserved XXRRXXKXXLXV in the N-terminal kinase binding domain95 stabilizes the active conformation of the active site cysteine115 and results in an approximately 100-fold increase in enzymatic activity44, 87, 99 . . .
  96. Hammer, M. et al. Dual specificity phosphatase 1 (DUSP1) regulates a subset of LPS-induced genes and protects mice from lethal endotoxin shock. J. Exp. Med. 203, 15-20 (2006) , .
    • . . . For instance, although Dusp10−/− T cells had elevated JNK activity (as predicted from in vitro studies), there was no change in p38 activity61; Dusp1−/− macrophages had elevated p38 and JNK activity but no change in ERK activity despite in vitro evidence that demonstrates an equal preference for all three62, 96, 97; DUSP3 had little activity towards MAPK in vitro, but had elevated ERK and JNK activity following RNA interference70; and Dusp2−/− macrophages and mast cells showed a surprising reduction in ERK and p38 activity but elevated JNK activity, highlighting the co-dependence of certain DUSPs and the strong influence of MAPK crosstalk31 (Table 1). . . .
    • . . . Recently, four reports described that DUSP1 suppresses endotoxic shock in vivo via feedback control of p38 and JNK activity96, 97, 110, 111 . . .
    • . . . Interestingly, although Dusp1−/− macrophages, splenocytes and dendritic cells showed an increase in cytokine production, which demonstrates its negative control over this cellular process, IL-12 production was specifically reduced, despite similar levels in serum after lipopolysaccharide challenge, which suggests some positive regulatory activities of DUSP1 (Refs 96,97) . . .
  97. Zhao, Q. et al. MAP kinase phosphatase 1 controls innate immune responses and suppresses endotoxic shock. J. Exp. Med. 203, 131-140 (2005).References 96 and 97 were 2 of 4 papers to come out over a 2-month period that described innate immune responses in DUSP1-deficient mice , .
  98. Rauhala, H. E. et al. Dual-specificity phosphatase 1 and serum/glucocorticoid-regulated kinase are downregulated in prostate cancer. Int. J. Cancer 117, 738-745 (2005) , .
    • . . . Overexpression of the ubiquitous DUSP1, which dephosphorylates ERK, JNK and p38 (Ref. 62), has been found in several malignancies, including breast and prostate98, 99 . . .
  99. Wang, H. Y., Cheng, Z. & Malbon, C. C. Overexpression of mitogen-activated protein kinase phosphatases MKP1, MKP2 in human breast cancer. Cancer Lett. 191, 229-237 (2003) , .
    • . . . Overexpression of the ubiquitous DUSP1, which dephosphorylates ERK, JNK and p38 (Ref. 62), has been found in several malignancies, including breast and prostate98, 99 . . .
    • . . . For example, ERK2 binding to DUSP6 via the conserved XXRRXXKXXLXV in the N-terminal kinase binding domain95 stabilizes the active conformation of the active site cysteine115 and results in an approximately 100-fold increase in enzymatic activity44, 87, 99 . . .
  100. Xu, S., Furukawa, T., Kanai, N., Sunamura, M. & Horii, A. Abrogation of DUSP6 by hypermethylation in human pancreatic cancer. J. Hum. Genet. 50, 159-167 (2005) , .
    • . . . DUSP6 is hyper-methylated in pancreatic cancer, which suggests that it could act as a tumour suppressor100, whereas DUSP2 is increased in ovarian cancer and a splice variant was found in leukaemia101, 102 . . .
  101. Givant-Horwitz, V. et al. The PAC-1 dual specificity phosphatase predicts poor outcome in serous ovarian carcinoma. Gynecol. Oncol. 93, 517-523 (2004) , .
    • . . . DUSP6 is hyper-methylated in pancreatic cancer, which suggests that it could act as a tumour suppressor100, whereas DUSP2 is increased in ovarian cancer and a splice variant was found in leukaemia101, 102 . . .
  102. Kothapalli, R., Yoder, S. J., Kusmartseva, I. & Loughran, T. P. Jr. Characterization of a variant of PAC-1 in large granular lymphocyte leukemia. Protein Expr. Purif. 32, 52-60 (2003) , .
    • . . . DUSP6 is hyper-methylated in pancreatic cancer, which suggests that it could act as a tumour suppressor100, whereas DUSP2 is increased in ovarian cancer and a splice variant was found in leukaemia101, 102 . . .
  103. Levy-Nissenbaum, O. et al. Dual-specificity phosphatase Pyst2-L is constitutively highly expressed in myeloid leukemia and other malignant cells. Oncogene 22, 7649-7660 (2003) , .
    • . . . DUSP7 shows enhanced expression in myeloid leukaemia103, 104, whereas DUSP26 is overexpressed in, and promotes growth of, anaplastic thyroid cancers105 . . .
  104. Levy-Nissenbaum, O. et al. Overexpression of the dual-specificity MAPK phosphatase PYST2 in acute leukemia. Cancer Lett. 199, 185-192 (2003) , .
    • . . . DUSP7 shows enhanced expression in myeloid leukaemia103, 104, whereas DUSP26 is overexpressed in, and promotes growth of, anaplastic thyroid cancers105 . . .
  105. Yu, W. et al. A novel amplification target, DUSP26, promotes anaplastic thyroid cancer cell growth by inhibiting p38 MAPK activity. Oncogene 26, 1178-1187 (2006) , .
    • . . . DUSP7 shows enhanced expression in myeloid leukaemia103, 104, whereas DUSP26 is overexpressed in, and promotes growth of, anaplastic thyroid cancers105 . . .
  106. Li, M., Zhou, J. Y., Ge, Y., Matherly, L. H. & Wu, G. S. The phosphatase MKP1 is a transcriptional target of p53 involved in cell cycle regulation. J. Biol. Chem. 278, 41059-41068 (2003) , .
    • . . . DUSP1 expression is also inversely related to apoptosis106, 107, although DUSP1 deletion in mice initially yielded no obvious phenotype with normal development and MAPK activities in fibroblasts108 . . .
  107. Yang, H. & Wu, G. S. p53 transactivates the phosphatase MKP1 through both intronic and exonic p53 responsive elements. Cancer Biol. Ther. 3, 1277-1282 (2004) , .
    • . . . DUSP1 expression is also inversely related to apoptosis106, 107, although DUSP1 deletion in mice initially yielded no obvious phenotype with normal development and MAPK activities in fibroblasts108 . . .
  108. Dorfman, K. et al. Disruption of the erp/mkp-1 gene does not affect mouse development: normal MAP kinase activity in ERP/MKP-1-deficient fibroblasts. Oncogene 13, 925-931 (1996) , .
    • . . . DUSP1 expression is also inversely related to apoptosis106, 107, although DUSP1 deletion in mice initially yielded no obvious phenotype with normal development and MAPK activities in fibroblasts108 . . .
  109. Zhao, Q. et al. The role of mitogen-activated protein kinase phosphatase-1 in the response of alveolar macrophages to lipopolysaccharide: attenuation of proinflammatory cytokine biosynthesis via feedback control of p38. J. Biol. Chem. 280, 8101-8108 (2005) , .
    • . . . However, further studies have shown elevated p38 activity in DUSP1-deficient alveolar macrophages109, which suggests a potential cell-type-specific activity for this DUSP. . . .
  110. Chi, H. et al. Dynamic regulation of pro- and anti-inflammatory cytokines by MAPK phosphatase 1 (MKP-1) in innate immune responses. Proc. Natl Acad. Sci. USA 103, 2274-2279 (2006) , .
    • . . . Recently, four reports described that DUSP1 suppresses endotoxic shock in vivo via feedback control of p38 and JNK activity96, 97, 110, 111 . . .
    • . . . In addition, DUSP1 regulated cytokine production in a temporally specific manner, whereby negative regulation on cytokines was seen at earlier time points following cellular activation, and positive regulation was observed at later time points110 . . .
  111. Salojin, K. V. et al. Essential role of MAPK phosphatase-1 in the negative control of innate immune responses. J. Immunol. 176, 1899-1907 (2006).References 110 and 111 were the other 2 of the 4 papers to come out over a 2-month period that described innate immune responses in DUSP1-deficient mice , .
    • . . . Recently, four reports described that DUSP1 suppresses endotoxic shock in vivo via feedback control of p38 and JNK activity96, 97, 110, 111 . . .
  112. Wu, J. J. et al. Mice lacking MAP kinase phosphatase-1 have enhanced MAP kinase activity and resistance to diet-induced obesity. Cell Metab. 4, 61-73 (2006) , .
    • . . . Despite unimpaired insulin signalling and glucose homeostasis, Dusp1−/− mice were resistant to diet-induced obesity due to increased energy expenditure, but they developed glucose intolerance112 . . .
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    • . . . Thus, the shorter serine/threonine residues may not gain access to the deeper binding pocket of the PTP and therefore may be spared from hydrolysis113. . . .
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    • . . . The active sites of PTPs are ~9 Å (Ref. 114), whereas those of the DUSPs tend to be shallower at ~6 Å (Refs 89,115) . . .
  115. Farooq, A. et al. Solution structure of ERK2 binding domain of MAPK phosphatase MKP-3: structural insights into MKP-3 activation by ERK2. Mol. Cell 7, 387-399 (2001) , .
    • . . . The active sites of PTPs are ~9 Å (Ref. 114), whereas those of the DUSPs tend to be shallower at ~6 Å (Refs 89,115) . . .
    • . . . For many PTPs, physical interaction via the KIM domain of the phosphatase and the target protein is required for conformational changes in the phosphatase to significantly increase enzymatic activity, which otherwise exhibits very low phosphatase activity in the absence of substrates115, 120 . . .
    • . . . For example, ERK2 binding to DUSP6 via the conserved XXRRXXKXXLXV in the N-terminal kinase binding domain95 stabilizes the active conformation of the active site cysteine115 and results in an approximately 100-fold increase in enzymatic activity44, 87, 99 . . .
  116. Lee, J. O. et al. Crystal structure of the PTEN tumor suppressor: implications for its phosphoinositide phosphatase activity and membrane association. Cell 99, 323-334 (1999) , .
    • . . . The wider opening of the PTEN pocket is consistent with its ability to dephosphorylate phosphoinositide lipids and phosphoserine/threonine substrates in addition to phosphotyrosine116 . . .
  117. Tanoue, T., Yamamoto, T. & Nishida, E. Modular structure of a docking surface on MAPK phosphatases. J. Biol. Chem. 277, 22942-22949 (2002) , .
    • . . . KIMs are defined as short sequence motifs that lie distal to the phosphoacceptor in the linear amino-acid sequence and ensure the efficiency and specificity of substrate phosphorylation117 . . .
  118. Pulido, R., Zuniga, A. & Ullrich, A. PTP-SL and STEP protein tyrosine phosphatases regulate the activation of the extracellular signal-regulated kinases ERK1 and ERK2 by association through a kinase interaction motif. EMBO J. 17, 7337-7350 (1998) , .
    • . . . Various types of docking sites have been identified in several MAPK interacting proteins, including upstream kinases (for example, MEKs), phosphatases (DUSPs), scaffold proteins, downstream effectors (for example, MAPKAPKs) and transcription factors, and these docking sites contribute to the affinity of these molecules for specific MAPK members118, 119 . . .
  119. Tanoue, T. & Nishida, E. Molecular recognitions in the MAP kinase cascades. Cell Signal. 15, 455-462 (2003) , .
    • . . . Various types of docking sites have been identified in several MAPK interacting proteins, including upstream kinases (for example, MEKs), phosphatases (DUSPs), scaffold proteins, downstream effectors (for example, MAPKAPKs) and transcription factors, and these docking sites contribute to the affinity of these molecules for specific MAPK members118, 119 . . .
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    • . . . For many PTPs, physical interaction via the KIM domain of the phosphatase and the target protein is required for conformational changes in the phosphatase to significantly increase enzymatic activity, which otherwise exhibits very low phosphatase activity in the absence of substrates115, 120 . . .
    • . . . Interestingly, DUSP6 seems to first dephosphorylate the phosphothreonine residue within the dually phosphorylated TXY motif on ERK2, dissociate, and subsequently reassociate with monophosphorylated ERK2 phoshotyrosine120 . . .
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