Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glial cells in the mammalian CNS are subject to environmental stress resulting from a variety of neuro-pathological conditions. In this study, we have examined the activation of a stress signal responsive kinase, i.e., stress-activated protein kinase (SAPK) or c-Jun N-terminal kinase (JNK), in primary cultures of rat brain glial cells (i.e., astrocytes and oligodendrocytes) and an oligodendrocyte progenitor cell line, CG4, in response to cytokines and other stress inducers. JNK/SAPK activity was measured by an immune complex kinase assay using polyclonal anti-JNK antibodies along with GST c-Jun (1-79) as the substrate. Among the cytokines tested, TNF-alpha had the strongest effect on JNK activation followed by TNF-beta in both the glial cell types while a substantial level of kinase activation was observed in response to IL-1 in astrocytes. JNK activation by TNF-alpha in astrocytes, but not in oligodendrocytes, showed a biphasic response. An in-gel kinase assay of cell extracts and immunoprecipitated JNK confirmed the activation of JNK1 in cells treated with TNF-alpha. JNK was also activated by several other stress-inducing factors including. UV light, heat shock, inhibitors of protein synthesis, and mechanical injury. Incubation of cells with bacterial sphingomyelinase and a cell-permeable ceramide stimulated JNK activity, suggesting that the ceramide pathway may play a role in JNK activation, although the time course of activation did not correspond to that of TNF-alpha. The results are discussed in terms of possible roles of JNK activation in signaling for gliosis in astrocytes and as a protective/toxic response in oligodendrocytes.
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PMID:Activation of C-jun N-terminal kinase/stress-activated protein kinase in primary glial cultures. 889 12

Both NF-kappaB and c-Jun are activated by cytokines such as TNF-alpha and by stresses such as UV irradiation. A key step in the activation of NF-kappaB is the phosphorylation of its inhibitor, IkappaB alpha, by a ubiquitination-inducible multiprotein kinase complex (IkappaB alpha kinase). A central kinase in the c-Jun activation pathway is mitogen-activated protein kinase/ERK kinase kinase-1 (MEKK1). Here, we show that MEKK1 induces the site-specific phosphorylation of IkappaB alpha in vivo and, most strikingly, can directly activate the IkappaB alpha kinase complex in vitro. Thus, MEKK1 is a critical component of both the c-Jun and NF-kappaB stress response pathways. Since the IkappaB alpha kinase complex can be independently activated by ubiquitination or MEKK1-dependent phosphorylation, it may be an integrator of multiple signal transduction pathways leading to the activation of NF-kappaB.
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PMID:Activation of the IkappaB alpha kinase complex by MEKK1, a kinase of the JNK pathway. 900 62

Fc gamma R cross-linking on murine macrophages resulted in the activation of mitogen-activated protein kinase (MAPK) family members p42MAPK, p38, and c-Jun NH2-terminal kinase (JNK)/stress-activated protein kinase (SAPK). The temporal pattern of activation was distinct for each kinase. p42MAPK activation peaked at 5 min after receptor cross-linking, while peak p38 activity occurred 5 to 10 min later. Maximal JNK/SAPK activation occurred 20 min after Fc gamma R cross-linking. The selective MAPK/extracellular signal-regulated kinase-1 (MEK-1) inhibitor PD 098059 inhibited activation of p42MAPK induced by Fc gamma R cross-linking, but not p38 or JNK/SAPK activation. PD 098059 also inhibited the synthesis of TNF-alpha induced by Fc gamma R cross-linking (IC50 approximately 0.1 microM). Together, these results suggest that 1) the activation of MAPKs may play a role in Fc gammaR signal transduction, and 2) the activation of p42MAPK is necessary for Fc gamma R cross-linking-induced TNF-alpha synthesis.
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PMID:Fc gamma receptor cross-linking activates p42, p38, and JNK/SAPK mitogen-activated protein kinases in murine macrophages: role for p42MAPK in Fc gamma receptor-stimulated TNF-alpha synthesis. 912 Mar 4

Lipopolysaccharide (LPS) stimulates immune responses by interacting with the membrane receptor CD14 to induce the generation of cytokines such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1, and IL-6. The mechanism by which the LPS signal is transduced from the extracellular environment to the nuclear compartment is not well defined. Recently, an increasing amount of evidence suggests that protein tyrosine kinases especially the Src-family kinases Hck, Fgr, and Lyn, play important roles in LPS signaling. To directly address the physiological function of Hck, Fgr and Lyn in LPS signaling, a genetic approach has been used to generate null mutations of all three kinases in a single mouse strain. hck-/-fgr-/-lyn-/- mice are moderately healthy and fertile; macrophages cultured from these mice express normal levels of CD14 and no other Src-family kinases were detected. Although the total protein phosphotyrosine level is greatly reduced in macrophages derived from hck-/-fgr-/-lyn-/- mice, functional analyses indicate that both elicited peritoneal (PEMs) and bone marrow-derived macrophages (BMDMs) from triple mutant mice have no major defects in LPS-induced activation. Nitrite production and cytokine secretion (IL-1, IL-6, and TNF-alpha) are normal or even enhanced in hck-/-fgr-/-lyn-/- macrophages after LPS stimulation. The development of tumor cell cytotoxicity is normal in triple mutant BMDMs and only partially impaired in PEMs after LPS stimulation. Furthermore, the activation of the ERK1/2 and JNK kinases, as well as the transcription factor NF-kappaB, are the same in normal and mutant macrophages after LPS stimulation. The current study provides direct evidence that three Src-family kinases Hck, Fgr, and Lyn are not obligatory for LPS-initiated signal transduction.
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PMID:Lipopolysaccharide (LPS)-induced macrophage activation and signal transduction in the absence of Src-family kinases Hck, Fgr, and Lyn. 915 3

Engagement of receptors for the Fc region of IgG (Fc gamma R) can activate a variety of biological responses in macrophages, and these responses can be modulated either positively or negatively by co-stimulation with a variety of agents including cytokines such as interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta). We have previously demonstrated that Fc gamma R crosslinking activates the mitogen-activated protein kinase (MAPK) family members p42MAPK, p38, and JNK. Herein, we examined the modulatory effect of IFN-gamma, TGF-beta, and platelet-activating factor (PAF) on Fc gamma R-induced MAPK activation in murine macrophages. Fc gamma R-induced activation of p42MAPK and JNK was augmented nearly two-fold by pretreatment with IFN-gamma. Conversely, TGF-beta pretreatment suppressed Fc gamma R-induced activation of p42MAPK, JNK, and p38. These modulatory effects of IFN-gamma and TGF-beta on MAPK activation correlated with changes in Fc gamma R-stimulated TNF-alpha production by these two cytokines.
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PMID:Interferon-gamma and transforming growth factor-beta modulate the activation of mitogen-activated protein kinases and tumor necrosis factor-alpha production induced by Fc gamma-receptor stimulation in murine macrophages. 929 89

A human homolog of the yeast Ssk2 and Ssk22 mitogen-activated protein kinase kinase kinases (MAPKKK) was cloned by functional complementation of the osmosensitivity of the yeast ssk2delta ssk22delta sho1delta triple mutant. This kinase, termed MTK1 (MAP Three Kinase 1), is 1607 amino acids long and is structurally highly similar to the yeast Ssk2 and Ssk22 MAPKKKs. In mammalian cells (COS-7 and HeLa), MTK1 overexpression stimulated both the p38 and JNK MAP kinase pathways, but not the ERK pathway. MTK1 overexpression also activated the MKK3, MKK6 and SEK1 MAPKKs, but not the MEK1 MAPKK. Furthermore, MTK1 phosphorylated and activated MKK6 and SEK1 in vitro. Overexpression of a dominant-negative MTK1 mutant [MTK1(K/R)] strongly inhibited the activation of the p38 pathway by environmental stresses (osmotic shock, UV and anisomycin), but not the p38 activation by the cytokine TNF-alpha. The dominant-negative MTK1(K/R) had no effect on the activation of the JNK pathway or the ERK pathway. These results indicate that MTK1 is a major mediator of environmental stresses that activate the p38 MAPK pathway, and is also a minor mediator of the JNK pathway.
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PMID:A human homolog of the yeast Ssk2/Ssk22 MAP kinase kinase kinases, MTK1, mediates stress-induced activation of the p38 and JNK pathways. 930 39

Treatment of mouse astrocyte cultures with combined interleukin (IL)-1alpha and tumor necrosis factor (TNF)-alpha induced expression of inducible nitric-oxide synthase (iNOS), resulting in sustained release of large amounts of nitric oxide, whereas TNF-alpha and IL-1alpha individually were unable to induce iNOS expression in astrocytes. The role of MAPK cascades and of NF-kappaB activation in the early intracellular signal transduction involved in iNOS transcription in TNF-alpha/IL-1alpha-stimulated astrocytes was investigated. TNF-alpha and IL-1alpha activated all p42/44(MAPK), p38(MAPK), and p54(JNK) pathways as determined by immunoprecipitation kinase assays using specific antibodies and substrates. The p38(MAPK) pathway is specifically involved in TNF-alpha/IL-1alpha-induced iNOS expression, since iNOS protein and nitric oxide release in the presence of a specific inhibitor of p38(MAPK), 4-(4-fluorophenyl)-2-2-(4-hydroxyphenyl)-5-(4-pyridyl)-imidazole (FHPI), were dramatically diminished. In contrast, PD98059, a specific inhibitor of MEK1 had no effect on iNOS expression. p38(MAPK) did not couple NF-kappaB to iNOS transcription, but NF-kappaB had a clear role in iNOS transcription regulation. Northern blot analysis showed that the p38(MAPK) pathway controlled iNOS expression at the transcriptional level, since iNOS mRNA was reduced in the presence of FHPI in TNF-alpha/IL-1alpha-stimulated astrocytes. iNOS expression was investigated with TNF receptor (TNFR)-1- and TNFR-2-deficient mice. The TNF-alpha activity in TNF-alpha/IL-1alpha-stimulated astrocytes was exclusively mediated through TNFR-1, most likely because TNFR-2-mediated signals in astrocytes did not connect to the p38(MAPK) pathway. These data suggest that TNF-alpha/IL-1alpha-induced iNOS expression depends on a yet undetermined second pathway in addition to p38(MAPK).
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PMID:Blockade of p38 mitogen-activated protein kinase pathway inhibits inducible nitric-oxide synthase expression in mouse astrocytes. 935 95

The immunostimulant tumor necrosis factor-alpha (TNF alpha), produced by monocytes/macrophages in response to inflammatory disorders, regulates gene expression in part through induction of mitogen-activated protein kinases (MAPKs), including the stress-activated protein kinase (SAPK) (c-Jun N-terminal kinase [JNK]) and the extracellular signal-regulated kinases (ERKs). In testicular Leydig cells, the induction of steroidogenesis by cAMP is inhibited by TNF alpha. To examine the potential mechanisms governing the mutual inhibition between cAMP and TNF alpha in Leydig cells, the intracellular signaling pathways that contribute to AP-1-dependent gene expression were examined in the mouse MA-10 Leydig cell line. TNF alpha induced SAPK activity sixfold at 15 min, and the PKC inhibitor calphostin C reduced the induction of SAPK by 30%. cAMP induced SAPK activity twofold but reduced TNF alpha-induced SAPK activity. ERK activity was inhibited by both cAMP and TNFa. TNFa increased c-Jun protein, but only weakly induced FOS proteins (c-Fos, FosB, Fra-1, and Fra-2) whereas cAMP increased the abundance of several FOS proteins (c-Fos, FosB, Fra-1, and Fra-2), with little effect on c-Jun levels. AP-1 binding activity, assessed using electrophoretic mobility shift assays, was increased twofold by TNF alpha and fivefold by cAMP. Cyclic AMP alone induced AP-1-responsive reporter (p3TPLUX) activity threefold after 2 h with peak effect of 4-fold at 4 hr. AP-1 reporter was not induced by TNF alpha alone but in the presence of cAMP, TNF alpha induced AP-1 reporter activity 12-fold. In conclusion, TNF alpha and cAMP induce distinct components that separately contribute to the modulation of AP-1 activity in MA-10 cells.
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PMID:The effect of tumor necrosis factor-alpha and cAMP on induction of AP-1 activity in MA-10 tumor Leydig cells. 936 89

Tumor-necrosis factor(TNF)-alpha inhibited in a dose-dependent fashion the proliferation of epidermal-growth-factor(EGF)-stimulated MCF-7 breast cancer cells with an IC50 of 0.25 nM. A comparable TNF-alpha-mediated inhibition of p42/44 mitogen-activated protein (MAP) kinase activity was observed in 10 nM EGF-stimulated cells. The MAP kinase activity dropped 50% within 3 min of TNF-alpha (1 nM) addition to EGF-stimulated MCF-7 cells. EGF and TNF-alpha, when added independently, led to a transient stimulation of MAP kinase activity with maximal activations within 6-8 min and 1-2 min, respectively. These observations suggest that MAP kinase activity in EGF-stimulated MCF-7 cells is modulated by the growth-inhibitory receptor pathways of TNF-alpha. Phosphorylation measurements on western blots determined the involvement of several individual MAP kinases, namely p42/44 MAP kinases, p38 MAP kinase and c-Jun N2-terminal kinase 1 (JNK1), in EGF and TNF-alpha-induced signalling. Phosphorylation of p42 and p38 MAP kinases only was observed after treatment with either TNF-alpha or EGF. A combination of both ligands inhibited p42 and p38 MAP kinase phosphorylation in MCF-7 cells. In contrast, no JNK1 phosphorylation was detected in these cells. Simultaneous addition of okadaic acid, a potent inhibitor of phosphatases 1 and 2A, blocked the decay of EGF-stimulated MAP kinase activity over 40 min. TNF-alpha added to EGF-stimulated and okadaic-acid-treated cells increased the MAP kinase activity twofold within 1 min. Similarly, okadaic acid treatment partly reverted the TNF-alpha-inhibited growth of MCF-7 cells. These experiments suggest that phosphatases are involved in the rapid shut-down by TNF-alpha of p42 MAP kinase activity.
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PMID:Tumor-necrosis factor-alpha modulates mitogen-activated protein kinase activity of epidermal-growth-factor-stimulated MCF-7 breast cancer cells. 937 Mar 49

TNF-alpha regulates the expression of many proinflammatory and profibrogenic gene products in macrophages, and hence plays a vital role in controlling the inflammatory response. We have shown previously that exposure of macrophages to TNF-alpha stimulates the activation of members of the mitogen-activated protein kinase (MAPK) family. In this study, we have investigated the mechanism of activation of the p38mapk by TNF-alpha in mouse bone marrow-derived macrophages. Exposure to TNF-alpha resulted in the activation of p38mapk, as measured by 1) the trans-phosphorylation of recombinant activating transcription factor-2 substrate by immunoprecipitated p38mapk and 2) specific tyrosine phosphorylation of immunoprecipitated p38mapk. In addition, selective ligation of the TNF-alpha receptor CD120a (p55) with human TNF-alpha was sufficient to induce p38mapk activation. Using an in vitro kinase assay with recombinant kinase-inactive p38mapk as substrate in the presence of [gamma-32P]ATP, the upstream kinases MKK3 (mitogen-activated protein kinase kinase 3) and MKK4 were found to be activated in response to TNF-alpha. These findings suggest that TNF-alpha transiently phosphorylates and activates the three members of the MAPK family, namely p42(mapk/erk2), p46 c-Jun amino-terminal kinase/stress-activated protein kinase (JNK/SAPK), and p38mapk following cross-linking of CD120a (p55), and that MKK3 and MKK4 are capable of phosphorylating p38mapk.
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PMID:Activation of p38mapk, MKK3, and MKK4 by TNF-alpha in mouse bone marrow-derived macrophages. 937 49


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