Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

To investigate mechanisms of mononuclear phagocyte cell signaling, the effects of bacterial LPS on protein kinase activities in normal human peripheral blood monocytes were examined. Incubation of intact monocytes with LPS brought about time- and concentration-dependent increases in myelin basic protein (MBP) phosphotransferase activity in high speed supernatants of cell lysates. Anion-exchange chromatography on Mono Q demonstrated that LPS treatment resulted in two principal peaks of stimulated MBP kinase activity. Evidence was obtained to indicate that the first eluted peak of MBP kinase activity is accounted for by p42 and p44 mitogen-activated protein (MAP) kinases. Thus, 1) MBP kinase activity within peak 1 was quantitatively precipitated by anti-MAP kinase Abs, 2) the enzyme effectively phosphorylated a specific peptide substrate, 3) peak 1 contained proteins of subunit size M(r) 42,000 and M(r) 44,000 that reacted specifically with anti-MAP kinase Abs, and that 4) were recognized by anti-phosphotyrosine Abs only after stimulation of cells with LPS. Studies of the second peak of LPS-stimulated MBP kinase activity indicate that it is an isoform of protein kinase C (PKC) because: 1) enzyme activity was quantitatively immunoprecipitated by anti-PKC Abs, 2) the activity of the enzyme was potently and selectively inhibited by a specific peptide modeled on the autoinhibitory domain of PKC, and 3) the presence of a protein of subunit size M(r) 80,000 recognized by anti-PKC Abs. Because the second peak of MBP kinase activity (like the first) was active in the absence of added calcium and in the presence of 2 mM EGTA, it appears to be a type II, calcium-independent isoform of PKC. Abs to CD14 completely abrogated LPS-induced activation of both Mono Q peaks of MBP phosphotransferase activity. These results indicate that LPS coordinately activates both an apparently calcium-independent PKC and MAP kinase in mononuclear phagocytes and these responses appear to be initiated by signaling through the cell surface receptor, CD14.
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PMID:CD14-dependent activation of protein kinase C and mitogen-activated protein kinases (p42 and p44) in human monocytes treated with bacterial lipopolysaccharide. 752 66

Vascular endothelial cell (EC) injury or activation by LPS plays a critical role in the pathogenesis of Gram-negative meningitis and endotoxic shock. EC do not express membrane CD14, but respond to LPS in a soluble CD14-dependent manner. The signal transduction mechanisms involved in LPS-induced EC responses are largely unknown. We used bovine and human brain microvessel EC (BBMEC, and HBMEC) to study LPS-induced protein tyrosine phosphorylation. LPS rapidly induced the tyrosine phosphorylation of several proteins in BBMEC and HBMEC, which was detectable by 5 to 15 min, reached a maximum by 30 min, and declined by 60 to 90 min. The increase in tyrosine phosphorylation was apparent following stimulation with LPS at 0.1 ng/ml and was dose dependent up to 100 ng/ml. Similar changes in tyrosine phosphorylation were induced by smooth and rough LPS as well as lipid A, but not by the inactive lipid A analogue, Rhodopseudomonas sphaeroides diphosphoryl lipid A. Pretreatment of EC with the tyrosine kinase inhibitor, herbimycin A, inhibited LPS-stimulated protein tyrosine phosphorylation and LPS-mediated lactic dehydrogenase release from BBMEC and IL-6 release from HBMEC in a dose-dependent manner. Three proteins with apparent m.w. of 44, 42, and 41 kDa were predominant among the LPS-induced tyrosine phosphoproteins, and they were identified as mitogen-activated protein kinase isoforms ERK1, ERK2, and p38, respectively. LPS-induced protein tyrosine phosphorylation in HBMEC and BBMEC was soluble CD14 dependent, since pretreatment of these cells with anti-hCD14 mAb inhibited the LPS-induced tyrosine phosphorylation of p44, p42, and p41. Additionally, LPS induced a mobility shift in p44 and p42 mitogen-activated protein kinase isozymes, which was inhibited by herbimycin A pretreatment of the EC. These findings demonstrate for the first time that increased protein tyrosine phosphorylation and activation of mitogen-activated protein kinases occur rapidly after LPS stimulation of EC in the presence of soluble CD14. Our data also suggest that a herbimycin-sensitive step, presumably a tyrosine kinase, is involved in mediating LPS-induced human EC activation and IL-6 secretion.
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PMID:Lipopolysaccharide stimulates the tyrosine phosphorylation of mitogen-activated protein kinases p44, p42, and p41 in vascular endothelial cells in a soluble CD14-dependent manner. Role of protein tyrosine phosphorylation in lipopolysaccharide-induced stimulation of endothelial cells. 756 Nov 8

The cellular signaling events leading to the systemic inflammatory response syndrome and sepsis in monocytes/macrophages activated by lipopolysaccharide (LPS) are well understood. LPS is a glycolipid component of Gram-negative bacterial cell wall. It exerts its effect through the lipid A moiety. LPS binds to monocytes/macrophages via a membrane-bound receptor, CD14, an interaction which is optimized in the presence of plasma factors, LPS-binding protein, and septin. Although LPS is known to bind to other receptors, the roles of these receptors in transmembrane signaling and activation of monocytes/macrophages are not as well understood as is that of the CD14 receptor. Intracellular events in response to LPS stimulation are mediated by phospholipase (PL) C, protein kinases, PLA2, and PLD. Activation of PLC by LPS results in the release of diacylglycerol and inositol 1,4,5-trisphosphate. The former mediates the stimulation of protein kinase C, and the latter induces an increase in intracellular calcium concentration. LPS stimulation of monocytes/macrophages also results in the phosphorylation and activation of several protein kinases, including protein tyrosine kinases which mediate cytokine production, and mitogen-activated protein kinase which activates cytosolic PLA2 to release arachidonate. LPS also plays a role in cellular proliferation and differentiation. Upregulation of the secretory form of PLA2 has also been documented in response to LPS. PLD is stimulated by LPS to release phosphatidic acid (PA). PA can activate the respiratory burst by increasing diacylglycerol production and by modulating the effects of guanine nucleotide-binding proteins. Therapeutic strategies to decrease the clinical effects of sepsis would logically include agents which block at initial receptor-ligand interaction, as well as those which attenuate the intracellular events that follow LPS stimulation. Early in vivo studies are promising, but clearly much work remains to be done.
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PMID:Signaling events in monocytes and macrophages. 758 75

Nuclear factor kappa B (NF-kappa B), consisting of p50 and p65, is bound to a cytoplasmic retention protein, I kappa B, in a resting state, and the stimulation of cells with a variety of inflammatory stimuli induces the dissociation of NF-kappa B from I kappa B and the nuclear translocation of NF-kappa B, thereby activating several genes involved in inflammatory responses, such as interleukin (IL)-6, IL-8, and tumor necrosis factor alpha. In order to elucidate the precise mechanism of NF-kappa B activation, we have established lipopolysaccharide (LPS)-dependent NF-kappa B activation in a cell-free system using plasma membrane-enriched, cytosol, and nuclear fractions extracted from a human monocytic cell line, THP-1, by disruption with sonication followed by a differential centrifugation. The combination of plasma membrane-enriched fraction and cytosol was sufficient to activate NF-kappa B in a LPS/CD14-dependent manner only in the presence of ATP as judged by the binding of NF-kappa B to the IL-8 gene kappa B site on an electrophoretic mobility shift assay. LPS-dependent NF-kappa B activation was inhibited by protein kinase inhibitors, such as staurosporine, herbimycin A, tyrphostin, and genistein, but not mitogen-activated protein kinase substrate, cGMP-dependent protein kinase, cAMP-dependent protein kinase, protein kinase C, and calmodulin-dependent protein kinase II inhibitory peptides, suggesting that staurosporine-sensitive kinase(s) as well as tyrosine kinase(s) are involved in LPS-mediated NF-kappa B activation. In addition, LPS induced the phosphorylation of I kappa B-alpha, starting at 5 min after the stimulation in a cell-free system. Moreover, the phosphorylation was inhibited by herbimycin A and tyrphostin, but not staurosporine, suggesting that these protein kinase inhibitors act at distinct steps of signal transmission. Establishment of ligand-dependent activation of NF-kappa B in a cell-free system will facilitate identification of protein kinase(s) and its substrate(s) involved in LPS-mediated NF-kappa B activation.
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PMID:Establishment of lipopolysaccharide-dependent nuclear factor kappa B activation in a cell-free system. 787 68

Activation of macrophages by bacterial lipopolysaccharide (LPS) induces transcription of genes that encode for proinflammatory regulators of the immune response. Previous work has suggested that activation of the transcription factor activator protein 1 (AP-1) is one LPS-induced event that mediates this response. Consistent with this notion, we found that LPS stimulated AP-1-mediated transcription of a transfected reporter gene in the murine macrophage cell line RAW 264.7. As AP-1 activity is regulated in part by activation of the c-Jun N-terminal kinase (JNK), which phosphorylates and subsequently increases the transcriptional activity of c-Jun, we examined whether LPS treatment of macrophages resulted in activation of this kinase. LPS treatment of RAW 264.7 cells, murine bone marrow-derived macrophages, and the human monocyte cell line THP-1 resulted in rapid activation of the p46 and p54 isoforms of JNK. Treatment with wild-type and rough mutant forms of LPS and synthetic lipid A resulted in JNK activation, while pretreatment with the tyrosine kinase inhibitor herbimycin A inhibited this response. Binding of LPS-LPS binding protein (LBP) complexes to CD14, a surface receptor that mediates many LPS responses, was found to be crucial, as pretreatment of THP-1 cells with the monoclonal antibody 60b, which blocks this binding, inhibited JNK activation. These results suggest that LPS activation of JNK in monocyte/macrophage cells is a CD14- and protein tyrosine phosphorylation-dependent event that may mediate the early activation of AP-1 in regulating LPS-triggered gene induction.
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PMID:Activation of c-Jun N-terminal kinase in bacterial lipopolysaccharide-stimulated macrophages. 861 Jan 16

Human vascular endothelial cells (HUVECs), which do not display the lipopolysaccharide (LPS) receptor CD14, were examined for protein tyrosine phosphorylation after LPS stimulation in the presence and absence of soluble CD14 (sCD14). By phosphotyrosine Western blotting and immunocomplex kinase assays we show that LPS was capable of inducing in these cells rapid protein tyrosine phosphorylation and kinase activation of two members of the mitogen-activated protein kinase (MAPK) family erk-1 and the newly discovered p38, requiring the presence of sCD14. LPS-induced tyrosine phosphorylation of MAPK was associated with increased transcript- and surface protein expression of intracellular adhesion molecule-1 by HUVECs. MAPK phosphorylation and activation was induced by LPS in concentrations as little as 30 ng/mL and as early as 15 minutes after stimulation. Furthermore, tyrosine kinase inhibitors such as Genistein partially inhibited this effect. These results show that LPS triggers similar signaling events in both CD14+ myelo-monocytic cells and cells lacking the putative LPS-receptor CD14, suggesting the presence of a common, yet unidentified element in LPS-signaling in both cell types.
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PMID:Lipopolysaccharide induces the rapid tyrosine phosphorylation of the mitogen-activated protein kinases erk-1 and p38 in cultured human vascular endothelial cells requiring the presence of soluble CD14. 863 98

Soluble staphylococcal peptidoglycan (sPGN) is an inducer of cytokine secretion and may activate macrophages through the CD14 lipopolysaccharide (LPS) receptor. To elucidate sPGN-activated signal transduction pathways, stimulation of mitogen-activated protein (MAP) kinases by sPGN was studied in mouse RAW264.7 macrophages. sPGN strongly activated extracellular signal-regulated kinase (ERK) 1 and ERK2, moderately activated c-Jun NH2 terminal kinase (JNK), and weakly activated p38 MAP kinase, in contrast to LPS, which strongly activated all of these kinases, and phorbol 12,13-dibutyrate (PDB), which strongly activated ERK1 and ERK2 but did not activate p38 or JNK. sPGN- and LPS-induced activation of ERK1 and ERK2, unlike PDB-induced activation, was sensitive to inhibition by herbimycin A and insensitive to inhibition by increased intracellular cAMP. These results demonstrate differential activation of MAP kinases by sPGN, similar but not identical activation of signal transduction pathways by sPGN and LPS, and different mechanisms of MAP kinase activation by bacterial stimulants and phorbol esters.
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PMID:Differential activation of extracellular signal-regulated kinase (ERK) 1, ERK2, p38, and c-Jun NH2-terminal kinase mitogen-activated protein kinases by bacterial peptidoglycan. 884 16

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

Septic shock is an increasingly important clinical condition, characterized by systemic hypotension, ischemia, and ultimately organ failure. In Gram negative infection, the bacterial cell wall component, lipopolysaccharide (endotoxin, LPS), has been strongly linked to the pathophysiological responses that result in septic shock. LPS is bound in plasma to a protein called LPS-binding protein (LBP), which facilitates the binding of LPS to a cell surface receptor, CD14. Binding to CD14 stimulates cell signaling mechanisms that result in the production of inflammatory cytokines. However, the events which follow LPS binding to CD14 and which lead to the production of cytokines remain unclear. It has recently become evident that a number of phosphorylation cascades including MAP kinase pathways and NF-kappaB activation pathway are initiated by exposure of cells to LPS. These cascades act at both the transcriptional and translational levels to regulate cytokine production. This review will focus on the signaling pathways that are initiated by LPS and the cellular effects of the signaling pathways.
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PMID:Cellular activation mechanisms in septic shock. 956 Mar 58

This communication describes an extracellular signal-regulated kinase kinase (MEK)-dependent signal transduction pathway that prevents the terminal differentiation of a hemopoietic cell line. Both PMA and the cell-permeable ceramide, C2-ceramide, caused differentiation of U937 cells, but with distinct cell morphology and CD11b/CD14 surface expression. While PMA activated extracellular signal-regulated kinase (ERK), a downstream kinase of Raf-MEK signaling, C2-ceramide activated c-Jun NH2-terminal kinase (JNK), an anchor kinase of stress-induced signaling. Furthermore, only C2-ceramide stimulated an induction of cell cycle arrest that was associated with stable expression of p21CIP1 and retinoblastoma nuclear phosphoprotein dephosphorylation. Expression of p21CIP1 and JNK activation were also observed in sphingosine-treated cells, whereas sphingosine did not induce detectable differentiation. Concomitant stimulation with C2-ceramide and PMA resulted in the PMA phenotype, and cell cycle arrest was absent. ERK activation was enhanced by C2-ceramide plus PMA stimulation, whereas the activation of JNK was aborted. Strikingly, the inhibition of MEK with PD98059 altered the phenotype of C2-ceramide- and PMA-stimulated U937 cells to that of cells treated with C2-ceramide alone. Thus, ERK and JNK pathways deliver distinct signals, and the ERK pathway is dominant to the JNK cascade. Furthermore, differentiation and cell cycle arrest caused by C2-ceramide rely on independent signaling pathways, and JNK is an unlikely signaling element for this differentiation. Importantly, during C2-ceramide and PMA costimulation, the JNK pathway is not simply blocked by ERK activation; rather, cross-talk between these MAP kinase pathways acts to simultaneously augment ERK activity and down-regulate JNK activity.
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PMID:The mitogen-activated protein kinase pathway inhibits ceramide-induced terminal differentiation of a human monoblastic leukemia cell line, U937. 968 2


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