A Novel Mitogen-Activated Protein Kinase Phosphatase Is an Important Negative Regulator of Lipopolysaccharide-Mediated c-Jun N-Terminal Kinase Activation in Mouse Macrophage Cell Lines

Abstract

Mitogen-activated protein kinases (MAPKs) are activated by phosphorylation of threonine and tyrosine residues within a signature sequence of T-X-Y by dual-specificity MAPK kinases (MKKs). MKKs are in turn phosphorylated and activated by a family of serine/threonine MKK kinases (47). Extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) (also called stress-activated protein kinase), and p38 (also called RK or CSBP) are distinct classes of MAPKs playing important roles in various cellular events. JNKs are activated by diverse stimuli, including DNA damage, heat shock, bacterial components, inflammatory cytokines, and Fas (31). Activated JNKs play an essential role in the activation of transcriptional factors, such as c-Jun (21), ATF-2 (16), Elk-1 (57), and ets-2 (50). In macrophages, activated JNKs mediate the expression of inducible nitric oxide synthase (6), cyclooxygenase-2 (56), chemokines such as RANTES (23), and cytokines such as tumor necrosis factor alpha (TNF-␣), interleukin-1 (IL-1), and IL-6 (39), all of which not only potently activate host defense mechanisms but also often lead to excessive inflammatory responses in microbial infection.MAPK activation is a reversible process, and an emerging family of dual-specificity protein phosphatases (DSPs) have been shown to inactivate MAPKs through dephosphorylation of both threonine and tyrosine residues that are essential for the enzymatic activity (4). DSPs share two common features: a catalytic domain with significant amino acid sequence homology to a vaccinia virus DSP, VH-1, and an N-terminal region homologous to the catalytic domain of the cdc25 phosphatase (rhodanase homology domain). Among DSP family members, some show highly selective substrate specificity while others efficiently inactivate all three classes of MAPKs. Interestingly, gene expression of many DSPs is significantly induced following stimulation with growth factors, cytokines, or cell stresses, and this induction of MAPK phosphatases (MKPs) may function as a negative feedback mechanism of MAPK activity.In this study, in order to elucidate the regulatory mechanisms of MAPK pathways in macrophages, we screened a cDNA library from a mouse macrophage cell line with a cDNA probe of MKP-1, a known MKP. We isolated a partial cDNA containing the extended active-site sequence motif, (V/L) X(V/I)HCXAG(I/V)SRSXT(I/V)XXAY(L/I)M (where X is any amino acid), conserved in all DSPs (27,35,41). By rescreening the library and extending the cDNA by the method of 5Ј rapid amplification of cDNA ends (5Ј-RACE), we have isolated a full-length cDNA, which we named MKP-M (for MKP isolated from macrophages). It includes an N-terminal

Restraint of Proinflammatory Cytokine Biosynthesis by Mitogen-Activated Protein Kinase Phosphatase-1 in Lipopolysaccharide-Stimulated Macrophages

“…4C). A finding that also illustrates this possibility has been reported for MKP-M, another MKP family member isolated from macrophages (35). MKP-M has been shown to primarily act on JNK, although its induction is primarily mediated by p38.…”

Identification and Characterization ofChlamydia pneumoniae-Specific Proteins That Activate Tumor Necrosis Factor Alpha Production in RAW 264.7 Murine Macrophages

“…In contrast, the effect of LPS on stimulation of TNF-␣ expression in RAW 264.7 cells was not affected by U0126. These findings are consistent with reports demonstrating that in addition to ERK 1/2, LPS-induced TNF-␣ expression occurs via p38 (2,45) and JNK (3,29) signaling. In contrast, C. pneumoniae antigens did not activate JNK and p38 kinases in this study (Fig.…”

ATM-dependent activation of the gene encoding MAP kinase phosphatase 5 by radiomimetic DNA damage

“…This di erence between JNK and p38 in the time course of dephosphorylation may re¯ect the activities of di erent MKPs following DNA damage. Indeed, several di erent MKPs are known to dephosphorylate JNK and p38 (Haneda et al, 1999;Camps et al, 2000;Masuda et al, 2001;Matsuguchi et al, 2001;Tanoue et al, 2001), but they may be involved to di erent extents in the deactivation of their target proteins following di erent stimuli. Since the transcription factors that induce the DUSP10 gene are not known, the mechanism of induction and the nature of its link to ATM are not clear.…”

“…Their subsequent deactivation is achieved by dephosphorylation of the TXY motif by several types of phosphatases including the dual speci®city MAP kinase phosphatases (MKPs). The 10 known members of the MKP family share common motifs, but exhibit substrate speci®city for di erent MAP kinases (Haneda et al, 1999;Camps et al, 2000;Masuda et al, 2001;Matsuguchi et al, 2001;Tanoue et al, 2001).…”