Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The synthetic low-toxicity lipid A analog DT-5461a induces endogenous TNF production in mice. The activity of TNF so induced is probably the main contributor to the antitumor effect of this compound. In the present study, we investigated the mechanism by which DT-5461a induces TNF production in murine macrophage RAW 264 cells. DT-5461a mimicked the ability of LPS to induce TNF production in a dose-dependent manner. DT-5461a at higher concentrations inhibited specific binding of [3H]LPS to the cells and reduced LPS-induced TNF production to the level induced by DT-5461a alone. In addition, DT-5461a, as well as LPS, induced tyrosine phosphorylation of MAP kinases, the early signal transduction pathway of this production. Herbimycin A, an inhibitor of tyrosine kinase, inhibited the LPS- and DT-5461a-induced tyrosine phosphorylation, expression of TNF mRNA, and subsequent TNF secretion. These results suggest that DT-5461a and LPS induce TNF production in murine macrophages through the common receptor sites and the similar early signaling pathway.
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PMID:Production of tumor necrosis factor induced by synthetic low-toxicity lipid A analog, DT-5461a, is mediated by LPS receptor sites and tyrosine kinase-MAP kinase signaling pathway in murine macrophages. 753 Nov 15

Treatment of human diploid FS-4 fibroblasts with TNF or IL-1 led to a rapid increase in the phosphorylation of a approximately 28-kDa protein. Increased phosphorylation was seen after 5 min of TNF treatment, it reached a plateau between 10 and 30 min, and decreased thereafter. Immunoprecipitation with specific antibodies identified the 28-kDa protein as a member of the family of small heat shock proteins (Hsp28). Treatment of cells with different kinase inhibitors (staurosporine, H7, H8, HA-1004, or chelerythrine chloride) failed to inhibit TNF-induced Hsp28 phosphorylation, suggesting that neither protein kinase C nor other common protein kinases were involved. Treatment of FS-4 cells with sodium arsenite led to a very strong increase in the phosphorylation of Hsp28 demonstrable after 5 min and persisting for at least 4 h. Tyrosine phosphorylation of pp42 and pp44 MAP kinases was increased by TNF treatment, whereas arsenite produced a modest increase in tyrosine phosphorylation of pp44 while decreasing that of pp42 MAP kinase. The finding that sodium arsenite strongly increased Hsp28 phosphorylation, together with the resistance of TNF-induced phosphorylation to kinase inhibitors, supports the notion that increased serine phosphorylation of Hsp28 in this system involves inhibition of protein phosphatase activity.
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PMID:Pathways of heat shock protein 28 phosphorylation by TNF in human fibroblasts. 785 64

The BAC-1.2F5 macrophage cell line depends on CSF-1 for proliferation and survival. Phosphorylation and activation of the RAF-1 kinase are among the early events in CSF-1 signal transduction. To characterize the role of RAF-1 in CSF-1-induced proliferation, we overexpressed oncogenically activated RAF-1, cellular RAF-1 and RAF-1 kinase-defective mutant proteins in BAC-1.2F5 cells. We were unable to establish stable cell lines expressing either kinase-negative or full length RAF-1 proteins, implying that expression of these molecules is not tolerated in BAC-1.2F5 cells. Oncogenically activated RAF-1 induces CSF-1-independent growth in the absence of autocrine growth factor production. Autonomous growth is not associated with dedifferentiation, since v-raf-expressing macrophages perform the same immunological functions as control cells. Intriguingly, autonomous growth correlates with the suppression of CSF-1-mediated MAP-Kinase activation and with the low constitutive expression of a number of CSF-1-inducible genes, including fos, jun, ets2, and myc, but also the genes for the inflammatory cytokines TNF alpha and IL-1 beta. Many of these genes have AP-1 binding sites in their promoters, and the v-raf-expressing cells contain constitutive AP-1 binding activity. These data indicate that RAF-1, but not MAP-Kinase, is a key component in CSF-1 mitogenic signal transduction, and are consistent with a working hypothesis in which RAF-1 mediates transcriptional activation of genes via AP-1.
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PMID:v-raf confers CSF-1 independent growth to a macrophage cell line and leads to immediate early gene expression without MAP-kinase activation. 824 34

A reconstituted lipoprotein, containing human apolipoprotein A-I and phosphatidylcholine (1:200, molar ratio), referred to as ApoLipo, was used prophylactically in an endotoxin shock model in anesthetized rabbits. ApoLipo was administered at a dose of 75 mg protein/kg body weight 15 min before the beginning of a slow, continuous lipopolysaccharide (LPS, endotoxin) infusion (4.17 micrograms LPS/kg/hr). During the 6 hr LPS infusion, the Control-LPS group manifested a marked increase in serum tumor necrosis factor (TNF, peak value 7.82 [2.7-11.2] ng/ml at 1 hr), and many of the pathophysiologic sequelae of endotoxin shock, including hypotension (MAP: 59 +/- 7 mmHg) and metabolic acidosis (BE: -9.9 +/- 2.7) at 3 hr, and a severe neutropenia developed rapidly (PMN count: 5 +/- 3% of baseline at 30 min). In the ApoLipo treated group, serum TNF levels did not rise during the course of LPS infusion (0.1 [0.06-0.64] ng/ml at 1 hr). Hypotension (77 +/- 2 mmHg) and acidosis (-2.7 +/- 0.4) were also significantly attenuated, and the appearance of leukopenia was delayed by 1 hr (110 +/- 12% at 30 min, but 9 +/- 2% at 2 hr). Endotoxemia in the ApoLipo treated group was reduced in comparison to controls, albeit nonsignificantly. The infusion of the same dose of phosphatidylcholine without apoA-I was significantly less efficacious.
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PMID:A reconstituted, apolipoprotein A-I containing lipoprotein reduces tumor necrosis factor release and attenuates shock in endotoxemic rabbits. 832 86

The model in Figure 3 summarizes the data presented above. Using the induction of the select panel of LPS-inducible genes and the phosphorylation on tyrosine of specific MAP kinases, we have been able to dissociate three signaling pathways shared by LPS and its analogs and mimetics: a pathway that leads to tyrosine phosphorylation, one that leads to the induction of a gene subset including TNF alpha, TNFR-2, and IL-1 beta, and a pathway that results in induction of IP-10, D3, and D8 gene expression. It is still unclear if macrophage activation by non-LPS products occurs entirely through distinct yet redundant pathways or if other signaling receptors ultimately tie into the same intermediate pathways. This approach may identify particular stimuli as tools to induce specific pathways leading to select gene subsets and/or tyrosine kinase activation and, perhaps, identify a pathway deficient in C3H/HeJ macrophages.
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PMID:Dissection of LPS-induced signaling pathways in murine macrophages using LPS analogs, LPS mimetics, and agents unrelated to LPS. 852 49

HUVEC exposed to IL-1 alpha, TNF alpha or LPS showed a time dependent increase in E-selectin expression which was maximal at between 4-6h after stimulation. Stimulation of HUVEC with IL-1 alpha, TNF alpha or LPS for between 2 and 6h followed by removal or neutralisation of IL-1 alpha, TNF alpha or LPS and incubation in new media up to 6h resulted in identical levels of E-selectin expression at 6h, as cells which had been continuously stimulated for 6h with IL-1 alpha, TNF alpha or LPS. These studies demonstrated that HUVEC were committed to the induction of E-selectin following a 2 hr incubation with either IL-1 alpha, TNF alpha or LPS. The protein tyrosine kinase (PTK) inhibitors ST271, ST638 or genistein (0-100M) were ineffective in reducing cytokine or LPS stimulated E-selectin expression during a 2h cytokine or LPS stimulation of cells, in which inhibitors were either coincubated with cytokine/LPS or previously preincubated with the PTK inhibitors. However when PTK inhibitors were present during both agonist activation (2h) and subsequent expression of E-selectin after removal of agonist (4h) the PTK inhibitors resulted in a dose dependent reduction in both IL-1 alpha and LPS stimulated E-selectin expression (IC50 = 50M). Moreover when PTK inhibitors were only incubated with cells for the 4h after cytokine or LPS activation of cells, PTK inhibitors resulted in a more effective dose dependent reduction in IL-1 alpha or LPS stimulated E-selectin expression (IC50 = 10M). Determination of total and surface expressed E-selectin showed that the reduction in E-selectin expression represented a reduction in E-selectin protein and analysis of E-selectin mRNA by RT-PCR demonstrated that inhibition of E-selectin protein synthesis reflected reduced E-selectin mRNA. Other cytokine or LPS signalling pathways such as the activation of MAP-kinase (ERK-2) was unaffected by pre and coincubation with the PTK inhibitors. These studies suggest that HUVEC can become committed to the induction of E-selectin after removal of the stimulus and that protein tyrosine kinase inhibitors do not effect initial (5-30 min) cytokine or LPS signals which result in E-selectin expression but can inhibit the expression of cytokine/LPS induced E-selectin expression at a step distal to MAP-kinase activation.
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PMID:Protein tyrosine kinase inhibitors act downstream of IL-1 alpha and LPS stimulated MAP-kinase phosphorylation to inhibit expression of E-selectin on human umbilical vein endothelial cells. 880 94

A novel homologue of p38 MAP kinase, called SAPK4, has been cloned which shares 61% amino acid identity with p38 and is expressed predominantly in testes, pancreas and small intestine. We also cloned an alternative form of p38beta, termed p38beta2, which lacks the additional 8 amino acid insertion unique to p38beta. p38, p38beta, p38beta2, ERK6/p38gamma/SAPK3, and SAPK4 were characterized with respect to stimulus-dependent activation in transfected cells, substrate specificity, and sensitivity to inhibition by pyridinyl imidazoles. All homologues were stimulated, although to differing extents, by IL-1beta, TNF, sorbitol, and UV. Only SAPK3 and SAPK4 were stimulated significantly by PMA. p38beta showed the weakest activation overall. MBP, ATF-2, and both MAPKAP kinase-2 and kinase-3 were good substrates of p38 and p38beta in vitro. In contrast, only MBP, ATF2, and MAPKAP kinase-3 proved to be significant substrates of SAPK3 and SAPK4, and of these three, MAPKAP kinase-3 was by far the weakest. p38beta had very poor kinase activity for all substrates except MBP. While both p38 and p38beta2 were comparably inhibited by SB 203580 and SB 202190, neither SAPK3 nor SAPK4 were inhibited. p38beta was partially inhibited by both inhibitors. These data suggest that SAPK3 and SAPK4 form a distinct subset of the p38 MAP kinases with different expression pattern, response to stimuli, substrate specificity, and inhibitor sensitivity.
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PMID:Novel homologues of CSBP/p38 MAP kinase: activation, substrate specificity and sensitivity to inhibition by pyridinyl imidazoles. 920 91

Activation of the extracellular signal-regulated kinase (ERK) pathway has been shown to occur in monocytes following stimulation with LPS. However, the importance of this event for monocyte function is not clear. To address this issue, we used the novel MAP/ERK kinase (MEK) inhibitor, U0126. Stimulation of monocytes with LPS resulted in activation of the mitogen-activated protein kinase (MAPK) family members ERK, Jun NH2-terminal kinase (JNK), and p38. Treatment of monocytes with LPS in the presence of U0126 blocked the activation of ERK1 and ERK2. However, the activation of Jun NH2-terminal kinase and p38 family members was not affected by the compound, confirming the selectivity of U0126. To examine the effects of MEK inhibition on monocyte function, we measured production of the cytokines IL-1, IL-8, and TNF, as well as PGE2. Monocytes treated with LPS in the presence of U0126 failed to release IL-1, IL-8, TNF, or PGE2. The failure to secrete IL-1 and TNF was due to decreased levels of mRNA. These results demonstrate that activation of MEK/ERK is critical for cytokine and PGE2 production by monocytes in response to LPS.
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PMID:Inhibition of MAP kinase kinase prevents cytokine and prostaglandin E2 production in lipopolysaccharide-stimulated monocytes. 982 May 49

The role of ceramide as a second messenger is a subject of great interest, particularly since it is implicated in signaling in response to inflammatory cytokines. Ceramide induces apoptosis in both cytokine-dependent MC/9 cells and factor-independent U937 cells. Elevation of cyclic adenosine monophosphate (cAMP) levels inhibits apoptosis induced by ceramide and several other treatments. One target of cAMP-mediated signaling is the transcription factor CREB (cAMP response element binding protein), and recently CREB phosphorylation at an activating site has been shown to also be mediated by a cascade involving p38 mitogen-activated protein kinase (MAPK), one of the stress-activated MAP kinases. Because no role for p38 MAPK in apoptosis has been firmly established, we examined the relationship between p38 MAPK and CREB phosphorylation under various conditions. Ceramide, or sphingomyelinase, like tumor necrosis factor- (TNF-) or the hematopoietic growth factor, interleukin-3 (IL-3), was shown to activate p38 MAPK, which in turn activated MAPKAP kinase-2. Each of these treatments led to phosphorylation of CREB (and the related factor ATF-1). A selective p38 MAPK inhibitor, SB203580, blocked TNF-- or ceramide-induced CREB phosphorylation, but had no effect on the induction of apoptosis mediated by these agents. The protective agents cAMP and IL-3 also led to CREB phosphorylation, but this effect was independent of p38 MAPK, even though IL-3 was shown to activate both p38 MAPK and MAPKAP kinase-2. Therefore, the opposing effects on apoptosis observed with cAMP and IL-3, compared with ceramide and TNF-, could not be explained on the basis of phosphorylation of CREB. In addition, because SB203580 had no effect of TNF- or ceramide-induced apoptosis, our results strongly argue against a role for p38 MAPK in the induction of TNF-- or ceramide-induced apoptosis.
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PMID:Ceramide and cyclic adenosine monophosphate (cAMP) induce cAMP response element binding protein phosphorylation via distinct signaling pathways while having opposite effects on myeloid cell survival. 986 64

ICAM-1 is an Ig-like cell adhesion molecule expressed by several cell types, including the endothelium. Cross-linking of ICAM-1 on the surface of different cell types has previously been shown to cause an increase in cellular activation within the cytoplasm. In this study, we have compared signaling events following ligation of ICAM-1 by cross-linking with mAbs with events after activation of HUVEC by TNF. ICAM-1 cross-linking caused activation of Erk-1 and the AP-1 transcription factor complex, without any increase in NF-kappaB activity, in contrast to TNF stimulation. Transcription of VCAM-1 mRNA was observed by reverse-transcriptase PCR after ICAM-1 cross-linking, with no associated transcription of E-selectin. This was reflected by the presence of VCAM-1 protein after immunoprecipitation, without E-selectin expression, in ICAM-1 cross-linked cells. In contrast, mRNA and protein for both VCAM-1 and E-selectin were observed in TNF-treated HUVEC, as expected. Addition of the MEK (MAP/Erk kinase) inhibitor PD98059 reduced expression of VCAM-1 after ICAM-1 cross-linking, suggesting that the Erk pathway is involved in ICAM-1-mediated VCAM-1 expression. In conclusion, ICAM-1-induced expression of VCAM-1 represents a pathway for adhesion molecule up-regulation that is distinct from the TNF-induced pathway. It may be similar to the IL-4 pathway or it may represent a novel pathway.
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PMID:Ligation of ICAM-1 on endothelial cells leads to expression of VCAM-1 via a nuclear factor-kappaB-independent mechanism. 1007 50


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