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:2.7.12.2 (MEK)
18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the contribution of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) and mitogen-activated protein kinase (MAP kinase) in norepinephrine (NE)-induced arachidonic acid (AA) release in rabbit aortic vascular smooth muscle cells (VSMC). NE enhanced release of AA via activation of cytosolic phospholipase A2 (cPLA2) but not secretory PLA2 in VSMC prelabeled with [3H]AA. NE (10 microM) enhanced CaM kinase II and MAP kinase activity. In cells transiently transfected with antisense oligonucleotides complementary to the translation initiation sites of CaM kinase II and MAP kinase, NE-induced AA release was inhibited by 100 and 35% respectively. Treatment of cells with PD-098059, a MAP kinase kinase inhibitor, or with MAP kinase antisense oligonucleotide reduced NE-induced activation of MAP kinase and cPLA2. NE-induced MAP kinase and cPLA2 activation was also inhibited in cells treated with a CaM kinase II inhibitor, KN-93, or with CaM kinase II antisense oligonucleotide. On the other hand, inhibition of MAP kinase kinase with PD-098059 or of MAP kinase with antisense oligonucleotides did not alter the NE-induced increase in CaM kinase II activity. Phosphorylation of MAP kinase and CaM kinase II by NE, studied by 32P incorporation and immune complex kinase assays, was inhibited by KN-93. Collectively, these data suggest that CaM kinase II can activate MAP kinase, which in turn activates cPLA2 to release AA for prostacyclin synthesis in the rabbit VSMC. This novel pathway for activation of MAP kinase by CaM kinase II appears to be mediated through stimulation of MAP kinase kinase. Activation of adrenergic receptors with NE in VSMC caused translocation of CaM kinase II, MAP kinase, and cPLA2 to the nuclear envelope only in the presence of extracellular Ca2+. Okadaic acid, which increased phosphorylation and activity, did not translocate these enzymes. Therefore, it appears that in rabbit VSMC, NE, by promoting extracellular Ca2+ influx, increases CaM kinase II activity, leading to activation of MAP kinase and cPLA2 and translocation to the nuclear envelope, resulting in release of AA from the nuclear envelope for prostacyclin synthesis.
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PMID:Calcium/calmodulin-dependent protein kinase IIalpha mediates activation of mitogen-activated protein kinase and cytosolic phospholipase A2 in norepinephrine-induced arachidonic acid release in rabbit aortic smooth muscle cells. 893 65

Incubation of rat glomerular mesangial cells with potent proinflammatory cytokines like interleukin 1beta, (IL- 1beta) triggers the expression of a non-pancreatic secretory phospholipase A2 (sPLA2) and increases the formation of prostaglandin E2. We show here that sPLA2 acts in an autocrine fashion on mesangial cells and induces a rapid activation of protein kinase C (PKC) isoenzymes delta and epsilon and of p42 mitogen-activated protein kinase (MAPK), two putative activators of cytosolic phospholipase A2 (cPLA2). sPLA2 also activates Raf-1 kinase in mesangial cells which integrates the signals coming from PKC for further processing along the MAPK cascade. Subsequently a phosphorylation and activation of cPLA2 is observed, thus arguing for a cross-talk between the two classes of PLA2. Pretreatment of cells with either the highly specific PKC inhibitor Ro-318220 or the highly specific MAPK kinase (MEK) inhibitor PD 98059 completely blocked the sPLA2-induced cPLA2 activation, indicating that both kinases are essential for the cross-talk between the two types of PLA2. The effect of sPLA2 is mimicked by lysophosphatidylcholine (LPC), a reaction product of sPLA2 activity. LPC stimulates PKC-epsilon, Raf-1 kinase and MAPK activation as well as cPLA2 activation with a subsequent increase in arachidonic acid release from mesangial cells. These data suggest that sPLA2 by cleaving membrane phospholipids and generating LPC and other lysophospholipids activates cPLA2 via the PKC/Raf-1/MAPK signalling pathway. Hence a network of interactions between different PLA2s is operative in mesangial cells and may contribute to the progression of glomerular inflammatory processes.
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PMID:Cross-talk between secretory phospholipase A2 and cytosolic phospholipase A2 in rat renal mesangial cells. 936 43

The biological effects of type IIA 14-kDa phospholipase A2 (sPLA2) on 1321N1 astrocytoma cells were studied. sPLA2 induced a release of [3H]arachidonic acid ([3H]AA) similar to that elicited by lysophosphatidic acid (LPA), a messenger acting via a G-protein-coupled receptor and a product of sPLA2 on lipid microvesicles. In contrast, no release of [1-14C]oleate could be detected in cells labeled with this fatty acid. As these findings pointed to a selective mechanism of [3H]AA release, it was hypothesized that sPLA2 could act by a signaling mechanism involving the activation of cytosolic PLA2 (cPLA2), i.e. the type of PLA2 involved in the release of [3H]AA elicited by agonists. In keeping with this view, stimulation of 1321N1 cells with sPLA2 elicited the decrease in electrophoretic mobility that is characteristic of the phosphorylation of cPLA2, as well as activation of p42 mitogen-activated protein (MAP) kinase, c-Jun kinase, and p38 MAP kinase. Incubation with sPLA2 of quiescent 1321N1 cells elicited a mitogenic response as judged from an increased incorporation of [3H]thymidine. Attempts to correlate the effect of extracellular PLA2 with the generation of LPA were negative. Incubation with pertussis toxin prior to the addition of either sPLA2 or LPA only showed abrogation of the response to LPA, thus suggesting the involvement of pertussis-sensitive Gi-proteins in the case of LPA. Treatments with inhibitors of the catalytic effect of sPLA2 such as p-bromophenacyl bromide and dithiothreitol did not prevent the effect on cPLA2 activation. In contrast, preincubation of 1321N1 cells with the antagonist of the sPLA2 receptor p-aminophenyl-alpha-D-mannopyranoside-bovine serum albumin, blocked cPLA2 activation with a EC50 similar to that described for the inhibition of binding of sPLA2 to its receptor. Moreover, treatment of 1321N1 cells with the MAP kinase kinase inhibitor PD-98059 inhibited the activation of both cPLA2 and p42 MAP kinase produced by sPLA2. In summary, these data indicate the existence in astrocytoma cells of a signaling pathway triggered by engagement of a sPLA2-binding structure, that produces the release of [3H]AA by activating the MAP kinase cascade and cPLA2, and leads to a mitogenic response after longer periods of incubation.
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PMID:Secretory phospholipase A2 activates the cascade of mitogen-activated protein kinases and cytosolic phospholipase A2 in the human astrocytoma cell line 1321N1. 941 22

This study investigated the signal transduction mechanisms of angiotensin-(1-7) [Ang-(1-7)]- and Ang II-stimulated arachidonic acid (AA) release for prostaglandin (PG) production in rabbit aortic vascular smooth muscle cells. Ang II and Ang-(1-7) enhanced AA release in cells prelabeled with [3H]AA. However, 6-keto-PGF1 alpha synthesis produced by Ang II was much less than that caused by Ang-(1-7). In the presence of the lipoxygenase inhibitor baicalein, Ang II enhanced production of 6-keto-PGF1 alpha to a greater degree than Ang-(1-7). Angiotensin type (AT)1 receptor antagonist DUP-753 inhibited only Ang II-induced [3H]AA release, whereas the AT2 receptor antagonist PD-123319 inhibited both Ang II- and Ang-(1-7)-induced [3H]AA release. Ang-(1-7), receptor antagonist D-Ala7-Ang-(1-7) inhibited the effect of Ang-(1-7), but not of Ang II. In cells transiently transfected with cytosolic phospholipase A2 (cPLA2), mitogen-activated protein (MAP) kinase or Ca(++)-/cal-modulin-dependent protein (CAM) kinase II antisense oligonucleotides, Ang-(1-7)- and Ang II-induced [3H]AA release was attenuated. The CaM kinase II inhibitor KN-93 and the MAP kinase kinase inhibitor PD-98059 attenuated both Ang-(1-7)- and Ang II-induced cPLA2 activity and [3H]AA release. Ang-(1-7) and Ang II also increased CaM kinase II and MAP kinase activities. Although KN-93 attenuated MAP kinase activity, PD-98059 did not affect CaM kinase II activity. Both Ang II and Ang-(1-7) caused translocation of cytosolic PLA2 to the nuclear envelope. These data show that Ang-(1-7) and Ang II stimulate AA release and prostacyclin synthesis via activation of distinct types of AT receptors. Both peptides appear to stimulate CaM kinase II, which in turn, via MAP kinase activation, enhances cPLA2 activity and release of AA for PG synthesis.
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PMID:Signal transduction mechanisms involved in angiotensin-(1-7)-stimulated arachidonic acid release and prostanoid synthesis in rabbit aortic smooth muscle cells. 943 2

Bacterial lipopolysaccharide (LPS) is a potent activator of cells of the macrophage/monocyte lineage. Two mature macrophage cell lines, P388D1 and RAW264.7, exhibit very different biological responses to LPS. Although RAW264.7 cells release arachidonic acid from phospholipid in response to LPS stimulation, P388D1 cells do not respond in this manner. However, LPS primes P388D1 cells to release arachidonic acid in response to other stimuli. The goal of this work is to contrast the biochemical events that occur in LPS-treated P388D1 and RAW264.7 macrophages. Enzyme assays indicate that LPS treatment induces the activation of cytosolic PLA2 in RAW264.7, but not in P388D1 cells. Phorbol ester (PMA), a receptor-independent stimulus, also fails to induce arachidonic acid release from P388D1 cells, suggesting that these cells may have a defect in the signal transduction machinery that is common to LPS and PMA. This hypothesis is supported by the observation that the expression of the LPS receptors CD14 and CD11b/CD18 is similar on P388D1 and RAW264.7 cells. Western blot analyses indicate that the erk kinases are activated upon LPS treatment of RAW264.7 but not P388D1 cells. LPS-induced arachidonic acid release is reduced in cells treated with the MEK inhibitor PD98059, suggesting that activated erk kinases mediate the phosphorylation and activation of cPLA2 in this system. Interestingly, the p42 isoform of erk (erk2) appears to be activated in resting P388D1 cells. This observation indicates that the MAP kinase cascade may be constitutively activated in P388D1 cells which may in turn limit their ability to respond to LPS. Together, these data provide evidence that mature macrophages from different sources can exhibit variable responses to LPS and highlight the danger of making generalizations regarding the effects of LPS on macrophages.
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PMID:Mature macrophage cell lines exhibit variable responses to LPS. 988 93

In response to oxidant stress, the cardiovascular system is known to express a number of genes, which could occur owing to the participation of mitogen-activated protein kinases such as MAPKs, ERK and JNK (SAPK) followed by stimulation of at least two well-defined transcription factors NF-KB and AP-1 (c-Fos and c-Jun). Oxidants activate cytosolic and membrane-bound PLA2 activities with the subsequent production of AA metabolites such as HETEs, which subsequently stimulate ERK and JNK (SAPK) activities leading to the activation of transcriptional factors and the ultimate stimulation of the transcription of several mitogen-stress-responsive genes. LacCer, a ceramide analogue present in atherosclerotic plaques, has been found to induce proliferation of aortic smooth muscle cells. LacCer is involved in Ras-GTP loading, activation of kinase cascades (MEK, Raf, p44 MAPK) and c-fos expression. TNF-alpha, on the other hand, induces c-fos, c-myc and c-jun expression. Recent investigations link ceramide and its analogues to the extracellular signal-regulated kinase (ERK) cascade, stress-activated protein kinase-c-Jun kinase (SAPK/JNK) cascade and apoptotic responses. These critical steps in the signalling pathways are sensitive to intracellular thiol-redox and protease(s)-antiprotease(s) status, both of which can be modified by oxidants. Because mobilisation of intracellular Ca2+ caused by a variety of signals also plays a role in the activation of the signalling pathways, an important aspect of future work will be to ascertain the roles of oxidants and Ca2+ individually and in combination in the activation of the signalling pathways. The following two important questions also deserve future attention: (1) How does NF-kB shield cells from apoptotic death? and (2) By what mechanisms does the activated NF-kB cause cellular transformation? Furthermore, the role of AP-1 acting as transcriptional activator seems clear, but the target genes remain to be defined.
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PMID:Oxidant-mediated activation of mitogen-activated protein kinases and nuclear transcription factors in the cardiovascular system: a brief overview. 988 18

P2U/2Y-receptors elicit multiple signaling in Madin-Darby canine kidney (MDCK) cells, including a transient increase of [Ca2+]i, activation of phospholipases C (PLC) and A2 (PLA2), protein kinase C (PKC) and mitogen-activated protein kinase (MAPK). This study examines the involvement of these signaling pathways in the inhibition of Na+,K+,Cl- cotransport in MDCK cells by ATP. The level of ATP-induced inhibition of this carrier ( approximately 50% of control values) was insensitive to cholera and pertussis toxins, to the PKC inhibitor calphostin C, to the cyclic nucleotide-dependent protein kinase inhibitors, H-89 and H-8 as well as to the inhibitor of serine-threonine type 1 and 2A phosphoprotein phosphatases okadaic acid. ATP led to a transient increase of [Ca2+]i that was abolished by a chelator of Ca2+i, BAPTA. However, neither BAPTA nor the Ca2+ ionophore A231287, or an inhibitor of endoplasmic reticulum Ca2+-pump, thapsigargin, modified ATP-induced inhibition of Na+,K+, Cl- cotransport. An inhibitor of PLC, U73122, and an inhibitor of MAPK kinase (MEK), PD98059, blocked ATP-induced inositol-1,4, 5-triphosphate production and MAPK phosphorylation, respectively. However, these compounds did not modify the effect of ATP on Na+,K+, Cl- cotransport activity. Inhibitors of PLA2 (AACOCF3), cycloxygenase (indomethacin) and lypoxygenase (NDGA) as well as exogenous arachidonic acid also did not affect ATP-induced inhibition of Na+,K+,Cl- cotransport. Inhibition of the carrier by ATP persisted in the presence of inhibitors of epithelial Na+ channels (amiloride), Cl- channels (NPPB) and Na+/H+ exchanger (EIPA) and was insensitive to cell volume modulation in anisosmotic media and to depletion of cells with monovalent ions, thus ruling out the role of other ion transporters in purinoceptor-induced inhibition of Na+,K+,Cl- cotransport. Our data demonstrate that none of the known purinoceptor-stimulated signaling pathways mediate ATP-induced inhibition of Na+,K+,Cl- cotransport and suggest the presence of a novel P2-receptor-coupled signaling mechanism.
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PMID:ATP-induced inhibition of Na+, K+, Cl- cotransport in Madin-Darby canine kidney cells: lack of involvement of known purinoceptor-coupled signaling pathways. 991 50

In the present study we demonstrated that CD95L cross-linking generated reverse signalling in the mouse derived Sertoli cell line TM4. Treatment of TM4 cells with mAb anti-CD95L induced activation of the cytosolic phospholipase A2 (cPLA2). Cytosolic PLA2 activation was controlled by the MAPK pathway as indicated by the ability of the specific MEK inhibitor, PD098059, to abolish cPLA2 activation. In addition, Western blot experiments showed a rapid increase in phosphorylated Erk1/2 following CD95L cross-linking, while no effect on the phosphorylation of other MAPK, p38 or JNK, was observed. CD95L cross-linking by mAb increased the levels of soluble CD95L and apoptotic activity of TM4 cell supernatants, which was blocked by co-incubation with the PLA2 inhibitor, AACOCF3 or PD098059. Finally, pre-treatment of TM4 cells with AACOCF3 or PD098059 completely abolished TM4-induced apoptosis of Jurkat T cells, thus indicating that the Erk/cPLA2 pathway is required for CD95L-induced apoptosis.
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PMID:Erk-dependent cytosolic phospholipase A2 activity is induced by CD95 ligand cross-linking in the mouse derived Sertoli cell line TM4 and is required to trigger apoptosis in CD95 bearing cells. 1127 37

We have investigated the mechanisms whereby alpha(2B)-adrenergic receptor (alpha(2B)-AR) promotes MAPK activation in a clone of the renal tubular cell line, LLC-PK1, transfected with the rat nonglycosylated alpha(2)-AR gene. Treatment of LLC-PK1-alpha(2B) with UK14304 or dexmedetomidine caused arachidonic acid (AA) release and ERK2 phosphorylation. AA release was abolished by prior treatment of the cells with pertussis toxin, quinacrine, or methyl arachidonyl fluorophosphonate but not by the addition of the MEK inhibitor U0126. The effects of alpha(2)-agonists on MAPK phosphorylation were mimicked by cell exposure to exogenous AA. On the other hand, quinacrine abolished the effects of UK14304, but not of AA, suggesting that AA released through PLA2 is responsible for MAPK activation by alpha(2B)-AR. The effects of alpha(2)-agonists or AA were PKC-independent and were attenuated by indomethacin and nordihydroguaiaretic acid. Treatment with batimastat, CRM 197, or tyrphostin AG1478 suppressed MAPK phosphorylation promoted by alpha(2)-agonist or AA. Furthermore, conditioned culture medium from UK14304-treated LLC-PK1-alpha(2B) induced MAPK phosphorylation in wild-type LLC-PK1. Based on these data, we propose a model whereby activation of MAPK by alpha(2B)-AR is mediated through stimulation of PLA2, AA release, generation of AA derivatives, activation of matrix metalloproteinases, release of heparin-binding EGF-like growth factor, transactivation of epidermal growth factor receptor, and recruitment of Shc. Whether this pathway is particular to alpha(2B)-AR and LLC-PK1 or whether it can be extended to other cell types and/or other G-protein-coupled receptors remains to be established.
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PMID:alpha 2B-adrenergic receptor activates MAPK via a pathway involving arachidonic acid metabolism, matrix metalloproteinases, and epidermal growth factor receptor transactivation. 1189 Dec 18

We have demonstrated that magnolol suppressed thromboxane B2 (TXB2) and leukotriene B4 (LTB4) formation in A23187-stimulated rat neutrophils. Maximum inhibition was obtained with about 10 microM magnolol. Magnolol was more effective in the inhibition of cyclooxygenase (COX) activity than in the inhibition of 5-lipoxygenase (5-LO) activity as assessed by means of enzyme activity determination in vitro and COX and 5-LO metabolic capacity analyses in vivo. Magnolol alone stimulated cytosolic phospholipase A2 (cPLA2) phosphorylation and the translocation of 5-LO and cPLA2 to the membrane, and evoked arachidonic acid (AA) release. Recruitment of both 5-LO and cPLA2 to the membranes was suppressed by EGTA. Arachidonyl trifluoromethyl ketone (AACOCF3), a PLA2 inhibitor, bromoenol lactone (BEL), a Ca2+-independent PLA2 (iPLA2) inhibitor, and EGTA suppressed the magnolol-induced AA release. However, none of the follows affected magnolol-induced AA-release: 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole (SB203580), a p38 mitogen-activated protein kinase (MAPK) inhibitor, 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)butadiene (U0126), a MAPK kinase (MEK) inhibitor, or 2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide (GF109203X), a protein kinase C (PKC) inhibitor. In addition, magnolol at 30 microM did not stimulate the p38 MAPK and extracellular signal-regulated kinase 2 (ERK2) enzyme activities. These results indicated that magnolol inhibits the formation of prostaglandins and leukotrienes in A23187-stimulated rat neutrophils, probably through a direct blockade of COX and 5-LO activities. The stimulatory effects of magnolol at high concentration on the membrane association of 5-LO and cPLA2 are attributable to the elevation of [Ca2+]i, and on the AA release is likely via activation of cPLA2 and iPLA2.
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PMID:Mechanisms of the influence of magnolol on eicosanoid metabolism in neutrophils. 1510 36


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