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

The addition of interleukin-3 (IL-3) and granulocyte-macrophage colony-stimulating factor (GM-CSF) to hormone-dependent cells induces tyrosine phosphorylation of Janus protein kinase 2 (Jak2) and activates its in vitro kinase activity. To explore the role of Jak2 in IL-3/GM-CSF-mediated signal transduction, we constructed a CD16/CD7/Jak2 (CD16/Jak2) fusion gene containing the external domain of CD16 and the entire Jak2 molecule and expressed this fusion protein using a recombinant vaccinia virus. The clustering of CD16/Jak2 fusion protein by cross-linking with an anti-CD16 antibody induced autophosphorylation of the fusion protein but did not induce the phosphorylation of either the endogenous Jak2 or the beta chain. Cross-linking of CD16/Jak2 stimulates the tyrosine phosphorylation of a large group of proteins that are also phosphorylated after the addition of IL-3 or GM-CSF and include proteins of 145, 97, 67, 52, and 42 kDa. Closer analysis demonstrated that the CD16/Jak2 phosphorylates Shc, a 52-kDa protein, and the 145-kDa protein associated tightly with Shc, as well as mitogen-associated protein kinase (pp42). Electrophoretic mobility shift assays demonstrate that CD16/Jak2 activates the ability of signal transduction and activation of transcription (STAT) proteins to bind to an interferon-gamma-activated sequence oligonucleotide in a manner similar to that seen after IL-3 treatment. Cross-linking of the CD16/Jak2 protein stimulated increases in c-fos and junB similar to IL-3 but did not cause major changes in the levels of the c-myc message, which normally increases after IL-3 treatment. Thus, a transmembrane CD16/Jak2 fusion is capable of activating protein phosphorylation and mRNA transcription in a manner similar but not identical to hematopoietic growth factors.
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PMID:Signal transduction by a CD16/CD7/Jak2 fusion protein. 754 2

Supraphysiological levels of glucocorticoids, whether endogenous (Cushing's syndrome) or exogenous (glucocorticoid therapy), inhibit growth in children and immature animals. This effect has long been suspected to be due to glucocorticoid antagonism of GH action at the level of peripheral tissues. In the present study we demonstrate direct antagonism of GH action at the cellular level by the artificial glucocorticoid dexamethasone. Dexamethasone was found to inhibit the ability of GH to elicit several early events in GH signaling in 3T3-F442A fibroblasts. Dexamethasone (100 nM) for 24 h decreases by 50-75% GH-induced tyrosyl phosphorylation of mitogen-activated protein kinases ERK1 and ERK2, the transcription factor Stat3/APRF, the GH receptor-associated tyrosine kinase JAK2, and the GH receptor. These effects appear to be specific to GH. Dexamethasone does not inhibit induction of tyrosyl phosphorylation of ERK proteins by epidermal growth factor or phorbol myristate acetate, nor does it block induction of tyrosyl phosphorylation of Stat3/APRF by leukemia inhibitory factor or interleukin-6, or induction of JAK2 by leukemia inhibitory factor or interferon-gamma. Dexamethasone does not decrease the expression of ERK1 or -2, Stat3, or JAK2 proteins. Rather, the effects of dexamethasone on GH action appear to be due to a decrease in the number of GH receptors in the plasma membrane. Twenty-four-hour treatment with dexamethasone leads to a 50% decrease i GH binding, which Scatchard analysis suggests is due to a decrease in GH receptor number. These findings suggest that glucocorticoids antagonize cellular GH action by decreasing GH binding, suggesting a mechanism by which systemic glucocorticoids could antagonize GH action in peripheral tissues.
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PMID:Dexamethasone-induced antagonism of growth hormone (GH) action by down-regulation of GH binding in 3T3-F442A fibroblasts. 758 9

Tumour necrosis factor-alpha (TNF-alpha), an important mediator in both immune and inflammation responses, is one of the major cytokines released by activated macrophages. The present study shows that, during macrophage activation, protein tyrosine phosphorylation of STAT1 alpha and ERK2 occurred as an immediate early signal, whereas maximum TNF-alpha mRNA transcription appeared at 3 hr, precursor TNF-alpha formation at 3 to 4 hr, and TNF-alpha release at 5 to 6 hr after stimulation of an RPMI-1640-based induction medium containing lipopolysaccharide (100 ng/ml), interferon-gamma (100 U/ml), and 0.5% bovine serum albumin. Herbimycin A, a tyrosine kinase inhibitor, suppresses protein tyrosine phosphorylation of STAT1 alpha and ERK2 and also blocks TNF-alpha production by resident peritoneal macrophages from BALB/c mice, suggesting a possible association between protein tyrosine phosphorylation of STAT1 alpha and ERK2 and macrophage activation resulting in TNF-alpha production.
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PMID:Dynamic production of tumour necrosis factor-alpha (TNF-alpha) messenger RNA, intracellular and extracellular TNF-alpha by murine macrophages and possible association with protein tyrosine phosphorylation of STAT1 alpha and ERK2 as an early signal. 867 7

JAK2, a member of the Janus kinase superfamily was found to interact functionally with Raf-1, a central component of the ras/mitogen-activated protein kinase signal transduction pathway. Interferon-gamma and several other cytokines that are known to activate JAK2 kinase were also found to stimulate Raf-1 kinase activity toward MEK-1 in mammalian cells. In the baculovirus coexpression system, Raf-1 was activated by JAK2 in the presence of p21ras. Under these conditions, a ternary complex of p21ras, JAK2, and Raf-1 was observed. In contrast, in the absence of p21ras, coexpression of JAK2 and Raf-1 resulted in an overall decrease in the Raf-1 kinase activity. In addition, JAK2 phosphorylated Raf-1 at sites different from those phosphorylated by pp60v-src. In mammalian cells treated with either erythropoietin or interferon-gamma, a small fraction of Raf-1 coimmunoprecipitated with JAK2 in lysates of cells in which JAK2 was activated as judged by its state of tyrosine phosphorylation. Taken together, these data suggest that JAK2 and p21ras cooperate to activate Raf-1.
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PMID:The cytokine-activated tyrosine kinase JAK2 activates Raf-1 in a p21ras-dependent manner. 887 96

Rat C6 glioma cells have been used to characterize molecular events involved in the regulation of inducible nitric oxide synthase (iNOS) gene expression stimulated by interferon-gamma (IFN-gamma) plus lipopolysaccharide (LPS). IFNs induce a signaling event which involves activation of Stat1 transcription factor. Previous studies have shown that IFNs also induce extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) activation. However, the mechanisms by which IFNs stimulate MAPK activation remain elusive. Here we show that in C6 glioma cells, transiently expressing the dominant-negative form of c-Ha-Ras (Asn-17) abrogated IFN-gamma-induced ERK1 and ERK2 activation. Furthermore, PD98059, a specific MEK1 inhibitor, also blocked this activation. These results indicate that p21ras and MEK1 are required for IFN-gamma-induced ERK1 and ERK2 activation. Recent studies have reported that MAPK is responsible for serine phosphorylation of Stat1 which is required for Stat1's DNA binding and maximal transcriptional activity. Thus, we examined the role of the Ras-MAPK pathway in Stat1 activation and subsequent iNOS induction in C6 glioma cells. Further experiments showed that neither Asn-17 Ras expression nor concentrations of PD98059, which completely abrogated IFN-gamma-induced ERK1 and ERK2 activation, affected Stat1 DNA binding activity or iNOS induction, indicating that the Ras-MAPK pathway does not appear to be involved in the activation of Stat1 and subsequent iNOS induction in C6 glioma cells.
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PMID:Activation of Stat1 and subsequent transcription of inducible nitric oxide synthase gene in C6 glioma cells is independent of interferon-gamma-induced MAPK activation that is mediated by p21ras. 918 Feb 63

Interleukin-18 (IL-18) was identified as an inducer of interferon-gamma (IFN-gamma) production by stimulated T cells. In this study, we used an ovalbumin-responsive murine Th1 clone (OVA#4), in which DNA synthesis was reportedly enhanced after IL-18 treatment in the presence of a non-mitogenic TCR/CD3 stimulus, to examine signal transduction pathways. In the presence of the stimulus, IL-18 induced the appearance of tyrosine-phosphorylated proteins and herbimycin A inhibited DNA synthesis. It is suggested that protein tyrosine kinase (PTK) mediated signaling is induced by IL-18. Specifically, IL-18 induced phosphorylation of phosphorylates p56(lck) (LCK) and mitogen-activated protein kinase (MAPK). IL-18 alone induced the kinase activities of both LCK and MAPK, and the activities were increased by the TCR/CD3 stimulus. Simultaneously, IL-18 induced the association of LCK with MAPK and this was also increased by the TCR/CD3 stimulus. The activation of the LCK-MAPK pathway correlated with enhanced DNA synthesis in OVA#4 cells. These results suggest that the LCK-MAPK pathway is involved in IL-18 signaling and that IL-18 may play an important role in modification of TCR/CD3-mediated response.
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PMID:Interleukin-18 induces activation and association of p56(lck) and MAPK in a murine TH1 clone. 926 43

SHP-1 (also known as PTP1C, SHPTP-1, SHP, and HCP) is an SH2 domain-containing protein-tyrosine phosphatase. We have stably overexpressed the native form and a catalytically inactive cysteine to serine mutant of the enzyme, SHP-1-(Cys --> Ser), in human cervical carcinoma HeLa cells. Following stimulation of the cells with epidermal growth factor (EGF) and interferon-gamma (INF-gamma), signal transducers and activators of transcription (STAT) activity was analyzed by using two 32P-labeled DNA probes, namely hSIE which is derived from a high affinity mutant form of the serum-inducible element in the c-fos promotor and GAS which resembles the INF-gamma activation site. EGF induced hSIE binding activity only, and the activity was suppressed by approximately 70% when the inactive mutant form of SHP-1 was expressed but was essentially unaffected by expression of the native enzyme. INF-gamma treatment resulted in appearance of both hSIE and GAS binding activities. While expression of the inactive mutant reduced the activities by 30-50%, the native enzyme caused a 20-30% increase. Consistent with effects on STAT activation, altered SHP-1 expression also affected EGF-induced activation of the mitogen-activated protein kinase pathway; expression of SHP-1-(Cys --> Ser) inhibited activity of MEK by approximately 25%, whereas expression of SHP-1 resulted in a approximately 25% increase. Further studies revealed that overexpression of SHP-1 caused decreased tyrosine phosphorylation of the EGF receptor and that EGF induced phosphorylation and recruitment of SHP-1. Together, the data suggest that SHP-1 is positively involved in EGF- and INF-gamma-induced STAT activation in non-hematopoietic HeLa cells and that, in the EGF signaling system, SHP-1 functions at least partly by modulating tyrosine phosphorylation of EGF receptor.
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PMID:Positive effects of SH2 domain-containing tyrosine phosphatase SHP-1 on epidermal growth factor- and interferon-gamma-stimulated activation of STAT transcription factors in HeLa cells. 928 52

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

Following injury to the central nervous system, an astroglial scar forms that is thought to impede neuronal regeneration and recovery of function. It is our hypothesis that inflammatory cytokines act upon astrocytes to alter their biochemical and physical properties, which may in turn be responsible for failed neuronal regeneration. We have therefore examined the interactions of two cytokines with prominent actions following injury, interferon-gamma (IFN-gamma) and basic fibroblast growth factor (FGF2), in modulating the extracellular matrix and proliferation of astrocytes in culture. We also evaluated the effects of these cytokines on the ability of astrocytes to support the growth of neurites. IFN-gamma significantly inhibited the proliferation of rat cortical astrocytes both in serum-free and serum-containing media as measured by [3H]thymidine incorporation. Furthermore, IFN-gamma also antagonized FGF2-induced proliferation. In parallel, IFN-gamma reduced the levels of the ECM molecules tenascin, laminin, and fibronectin as evaluated by Western blot analysis and immunocytochemistry. Similarly, IFN-gamma also antagonized FGF2-induced tenascin formation. While IFN-gamma-pretreated astrocyte monolayers did not differ from control in their ability to support neurite outgrowth of cortical neurons, it antagonized the enhancement of neurite outgrowth on FGF2-treated monolayers. We demonstrate that IFN-gamma did not alter signal transduction through the FGF2 receptor down to the phosphorylation of mitogen-activated protein kinase, suggesting that the interaction is at the level of transcriptional regulation or that an alternate pathway is involved. These results support the hypothesis that inflammatory cytokines interact to modulate several facets of the gliotic response and such interactions may be important in creating the biochemical and physical properties of the glial scar.
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PMID:Inflammatory cytokines interact to modulate extracellular matrix and astrocytic support of neurite outgrowth. 941 38

Tumor necrosis factor-alpha (TNFalpha) and nitric oxide (NO), the product of inducible NO synthase (iNOS), mediate inflammatory and immune responses in the CNS under a variety of neuropathological situations. They are produced mainly by "activated" astrocytes and microglia, the two immune regulatory cells of the CNS. In this study we have examined the regulation of TNFalpha and iNOS gene expression in endotoxin-stimulated primary glial cultures, focusing on the role of mitogen-activated protein (MAP) kinase cascades. The bacterial lipopolysaccharide (LPS) was able to activate extracellular signal-regulated kinase (ERK) and p38 kinase subgroups of MAP kinases in microglia and astrocytes. ERK activation was sensitive to PD98059, the kinase inhibitor that is specific for ERK kinase. The activity of p38 kinase was inhibited by SB203580, a member of the novel class of cytokine suppressive anti-inflammatory drugs (CSAIDs), as revealed by blocked activation of the downstream kinase, MAP kinase-activated protein kinase-2. The treatment of glial cells with either LPS alone (microglia) or a combination of LPS and interferon-gamma (astrocytes) resulted in an induced production of NO and TNFalpha. The two kinase inhibitors, at micromolar concentrations, individually suppressed and, in combination, almost completely blocked glial production of NO and the expression of iNOS and TNFalpha, as determined by Western blot analysis. Reverse transcriptase-PCR analysis showed changes in iNOS mRNA levels that paralleled iNOS protein and NO while indicating a lack of effect of either of the kinase inhibitors on TNFalpha mRNA expression. The results demonstrate key roles for ERK and p38 MAP kinase cascades in the transcriptional and post-transcriptional regulation of iNOS and TNFalpha gene expression in endotoxin-activated glial cells.
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PMID:Extracellular signal-regulated kinase and p38 subgroups of mitogen-activated protein kinases regulate inducible nitric oxide synthase and tumor necrosis factor-alpha gene expression in endotoxin-stimulated primary glial cultures. 946 88


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