Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.12.2 (MEK)
 18,161 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

Angiotensin II (Ang II) is a potent pressor hormone, a stimulus for vascular smooth muscle hypertrophy and an activator of multiple tyrosine kinases. The physiological effects of Ang II are mediated through activation of AT1 and AT2 receptors, receptors that have been coupled to tyrosine kinase(s) and tyrosine phosphatases, respectively. Agonists of G protein-coupled receptors, of which Ang II is one, have recently been shown to stimulate smooth muscle contraction in part via activation tyrosine kinases. We tested the hypothesis that Ang II-induced contraction in the rat aorta was dependent on activation of tyrosine kinase(s) and specifically investigated the role of the tyrosine kinase mitogen-activated protein kinase kinase (MEK), a kinase important to the mitogen activated protein kinase (MAPK) pathway. Rat thoracic aortic strips denuded of endothelium and cultured aortic smooth muscle cells were used in isolated tissue baths for measurement of isometric contractile force and Western analyses of protein tyrosyl-phosphorylation. Ang II (0.1-100 nM)-induced contraction in the aorta was completely blocked by the AT1 receptor antagonist losartan (1 microM) but unaffected by the AT2 receptor antagonist PD123319 (100 nM) or tyrosine phosphatase inhibitor sodium orthovanadate (1 microM), indicating an AT1 receptor mediates aortic contraction to Ang II. Neither the tyrosine kinase inhibitor genistein (5 microM), inactive tyrosine kinase inhibitor daidzein (5 microM) nor MEK inhibitor PD098059 (10 microM) reduced Ang II-induced contraction; the concentrations of inhibitors used maximally reduced contraction stimulated by other agonists of G protein-coupled receptors such as serotonin. Moreover, Ang II-induced contraction was not altered by the combination of PD098059 and PD123319, indicating that it is unlikely AT2 receptor stimulation masks activation of the MAPK pathway through AT1 receptor activation. The nonflavone tyrosine kinase inhibitor tyrphostin B42 (30 microM) reduced Ang II-induced maximal contraction (to 11.2% control) but, unlike the other tyrosine kinase inhibitors, also reduced KCl-induced contraction (to 55.2% control), indicating a probable nonselectivity of tyrphostin B42. Ang IIinduced maximal contraction was reduced by the L-type voltage gated calcium channel antagonist nifedipine (50 nM), consistent with the activation of calcium channels by Ang II. In cultured rat aortic smooth muscle cells, Ang II (0.1-1000 nM) stimulated concentration-dependent tyrosyl-phosphorylation of the extracellular signal regulated kinase (Erk) mitogen activated protein kinases (maximal stimulation, fold basal: Erk-1 = 17-fold, Erk-2 = 3-fold), indicating that Ang II can activate MEK. Losartan (1 microM) abolished Ang II (10 nM)-induced Erk tyrosyl-phosphorylation and PD098059 (10 microM), which did not diminish Ang II-induced aortic contraction, reduced Ang II (10 nM)-stimulated phosphorylation of Erk-2 by 72%. Finally, Ang II (1 microM) increased tyrosyl-phosphorylation of the Erk proteins in isolated aorta exposed to Ang II for 5 min. Thus, while Ang II can stimulate both MEK activation and vascular contraction via interaction with AT1 receptors, stimulation of MEK does not appear to be important for Ang II-induced contraction. These findings dissociate the process of Ang II-stimulated Erk protein tyrosyl-phosphorylation from Ang II-induced contraction in the rat aorta.
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PMID:Dissociation of angiotensin II-stimulated activation of mitogen-activated protein kinase kinase from vascular contraction. 973 8

Angiotensin II (ATII) and platelet-derived growth factor (PDGF) are two vasoconstrictors implicated in the maintenance of normal vascular homeostasis. PDGF A-chain levels increase in cultured vascular smooth muscle cells (SMCs) exposed to ATII. The molecular mechanisms underlying this induction are not known. We used transient transfection analysis to show that ATII can increase reporter gene activity driven by fragments of the PDGF-A promoter bearing recognition elements for the transcription factor, Egr-1. Nuclear run-off experiments indicate that ATII induces Egr-1 expression at the level of transcription. Gel shift and supershift studies show that Egr-1 protein accumulates in the nuclei of SMCs exposed to ATII and binds to the proximal region of the PDGF-A promoter in a specific, time-dependent manner. ATII induced extracellular-signal regulated kinase (p42/44 ERK) activity as did phorbol 12-myristate 13-acetate. The specific MEK1/2 inhibitor, PD98059, suppressed both PDGF-A and Egr-1 endogenous and promoter-dependent expression inducible by ATII. The ATII type 1 receptor (AT1) antagonist, Losartan, inhibited ATII-induction of p42/44 ERK, as well as Egr-1 and PDGF-A, whereas neither PD123319, an AT2 receptor antagonist, nor wortmannin, an inhibitor of phosphatidylinositol 3-kinase and c-Jun N-terminal kinase, had any effect. ATII-induction of Egr-1 and PDGF-A was blocked by SIN-1, a NO donor. In addition, this pathway was blocked by overexpression of NO synthase. Collectively, these findings demonstrate that ATII activation of the PDGF-A promoter is mediated via the MEK/ERK/Egr-1 pathway and AT1 receptor and that this process is antagonized by NO.
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PMID:Angiotensin II (ATII)-inducible platelet-derived growth factor A-chain gene expression is p42/44 extracellular signal-regulated kinase-1/2 and Egr-1-dependent and mediated via the ATII type 1 but not type 2 receptor. Induction by ATII antagonized by nitric oxide. 1044 31

In a previous study, we had shown that activation of the AT2 (angiotensin type 2) receptor of angiotensin II (Ang II) induced morphological differentiation of the neuronal cell line NG108-15. In the present study, we investigated the nature of the possible intracellular mediators involved in the AT2 effect. We found that stimulation of AT2 receptors in NG108-15 cells resulted in time-dependent modulation of tyrosine phosphorylation of a number of cytoplasmic proteins. Stimulation of NG108-15 cells with Ang II induced a decrease in GTP-bound p21ras but a sustained increase in the activity of p42mapk and p44mapk as well as neurite outgrowth. Similarly, neurite elongation, increased polymerized tubulin levels, and increased mitogen-activated protein kinase (MAPK) activity were also observed in a stably transfected NG108-15 cell line expressing the dominant-negative mutant of p21ras, RasN17. These results support the observation that inhibition of p21ras did not impair the effect of Ang II on its ability to stimulate MAPK activity. While 10 microM of the MEK inhibitor, PD98059, only moderately affected elongation, 50 microM PD98059 completely blocked the Ang II- and the RasN17-mediated induction of neurite outgrowth. These results demonstrate that some of the events associated with the AT2 receptor-induced neuronal morphological differentiation of NG108-15 cells not only include inhibition of p21ras but an increase in MAPK activity as well, which is essential for neurite outgrowth.
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PMID:Signals from the AT2 (angiotensin type 2) receptor of angiotensin II inhibit p21ras and activate MAPK (mitogen-activated protein kinase) to induce morphological neuronal differentiation in NG108-15 cells. 1047 50

The aim of the present study was to investigate the proliferative effects of Ang II in human cardiac fibroblasts. The effects of Ang II in human cardiac fibroblasts on the 3H-thymidine incorporation, the cell number, the 3H-leucine incorporation and the total protein content were measured. The expression of receptor mRNA was performed by reverse transcription-polymerase chain reaction (RT-PCR). Ang II increased 3H-leucine incorporation in a concentration-dependent manner but not 3H-thymidine incorporation in primary cultures of human cardiac fibroblasts. The maximum effect (24 +/- 3% over control) was obtained at a concentration of 10 nM. There were no significant alterations of cell number or total protein content, suggesting that Ang II stimulated protein synthesis but did not induce hypertrophy. The accumulation of 3H-leucine was blocked by the AT1 receptor antagonist candesartan but not by the AT2 receptor antagonist PD123319. By using RT-PCR, both AT1 and AT2 receptors mRNA were found to be expressed in human cardiac fibroblasts. The selective MAPKK inhibitor PD098059, the protein kinase C inhibitor K252a or the phospholipase C inhibitor U73122 did not significantly inhibit Ang II augmented 3H-leucine incorporation. However, this was significantly blocked by the Ca2+-dependent protein kinase C inhibitor GO6976, the non-selective protein kinase inhibitor staurosporine and the tyrosine kinase inhibitor tyrphostin 25. The effects of Ang II were unaffected by the Gi-protein blocker pertussis toxin, indicating a Gi-protein-independent pathway. Ang II was synergistic with insulin but showed no significant increase on 3H-leucine incorporation when combined with PDGF or EGF. In summary, Ang II stimulates protein synthesis through AT1 receptors in human cardiac fibroblasts, but has no hypertrophic or hyperplastic effect. The response is mediated by a MAPKK-independent and Ca2+-sensitive PKC-dependent pathway.
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PMID:Angiotensin II type 1 receptors stimulate protein synthesis in human cardiac fibroblasts via a Ca2+-sensitive PKC-dependent tyrosine kinase pathway. 1071 68

Angiotensin II (Ang II) receptor subtype 1, AT1, is expressed by the rat thyroid. A relationship between thyroid function and several components of the renin-angiotensin system has also been established, but the Ang II cellular effects in thyrocytes and its transduction signalling remain undefined. The aim of the present paper was to investigate the modulation of the activity of the Na(+)-K(+)ATPase by Ang II and its intracellular transduction pathway in PC-Cl3 cells, an established epithelial cell line derived from rat thyroid. Here we have demonstrated, by RT-PCR analysis, the expression of mRNA for the Ang II AT1 receptor in PC-Cl3 cells; mRNA for the Ang II AT2 receptor was not detected. Ang II was not able to affect the intracellular Ca(2+) concentration in fura-2-loaded cells, but it stimulated the translocation from the cytosol to the plasma membrane of atypical protein kinase C-zeta (PKC-zeta) and -iota (PKC-) isoforms with subsequent phosphorylation of the extracellular signal-regulated kinases 1 and 2 (ERK1 and 2). Translocated atypical PKCs displayed temporally different activations, the activation of PKC-zeta being the fastest. PC-Cl3 cells stimulated with increasing Ang II concentrations showed dose- and time-dependent activation of the Na(+)-K(+)ATPase activity, which paralleled the PKC-zeta translocation time course. Na(+)-K(+)ATPase activity modulation was dependent on PKC activation since the PKC antagonist staurosporine abolished the stimulatory effect of Ang II. The inhibition of the ERK kinases 1 and 2 (MEK1 and 2) by PD098059 (2'-amino-3'-methoxyflavone) failed to block the effect of Ang II on the Na(+)-K(+)ATPase activity. In conclusion, our results suggest that Ang II modulates Na(+)-K(+)ATPase activity in PC-Cl3 cells through the AT1 receptor via activation of atypical PKC-zeta while the Ang II-activated PKC- appears to have other as yet unknown functions.
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PMID:Angiotensin II AT1 receptor stimulates Na+ -K+ATPase activity through a pathway involving PKC-zeta in rat thyroid cells. 1252 32

Extracellular signal-regulated kinase 1/2 (ERK1/2) may play a central signaling role in vascular remodeling. We investigated a possible combined role for the renin-angiotensin system and platelet-derived growth factor beta-receptor (PDGF-beta-R) in pressure-induced ERK1/2 activation in intact rat mesenteric small arteries. In an organ culture model, vessels were pressurized (70 mm Hg) for 1 hour plus a 5-minute intervention period. The intervention was either a rise in intraluminal pressure (up to 140 mm Hg) or challenge with angiotensin II (Ang II, 0.1 micromol/L) or PDGF-BB (30 microg/L). ERK1/2 activation was determined by Western blotting as formation of phosphorylated ERK1/2. All interventions caused ERK1/2 activation that was inhibited by the MEK inhibitor PD98059. The response to pressure was inhibited by an ACE inhibitor (perindoprilat), an Ang II receptor type 1 (R-AT1) antagonist (candesartan), and tyrosine kinase inhibitors (genistein, herbimycin A). An R-AT2 antagonist (PD123319) had no significant effect. Both a PDGF-receptor tyrosine kinase inhibitor (RPR101511A) and a neutralizing PDGF-beta-R antibody (AF385) inhibited the activation of ERK1/2 caused by PDGF-BB, Ang II, and pressure. That the latter interventions could indeed inhibit the PDGF-beta-R was supported by experiments with unmounted vessels in which PDGF-beta-R activation was measured by Western blot; both PDGF-BB and Ang II-mediated PDGF-beta-R activation were inhibited by RPR101511A and AF385. Immunohistochemistry showed that ERK1/2 and PDGF-beta-R was located in the adventitia, tunica media, and intima. The results suggest that pressure in rat mesenteric small arteries causes acute activation of ERK1/2 through pathways involving Ang II and PDGF-beta-R.
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PMID:Pressure-induced activation of extracellular signal-regulated kinase 1/2 in small arteries. 1262 63

Undersulfation of the basement membrane matrix of alveolar type II (AT2) cells compared with that of neighboring type I cells is believed to account for some of the known morphological and functional differences between these pneumocytes. Heparin, a model for sulfated components of basement membrane matrices, is known to inhibit fibroblast growth factor (FGF)-2-stimulated DNA synthesis as well as gene expression of FGF-2 and its receptor in AT2 cells. To determine whether these end points result from specific effects of heparin on FGF-related signaling pathways, isolated rat AT2 cells were treated with 100 ng/ml FGF-1 or FGF-2 in the presence of up to 500 microg/ml heparin. In addition, experiments were done on cells grown in the presence of 20 mM sodium chlorate (sulfation inhibitor). High-dose heparin reduced FGF-1- or FGF-2-stimulated phosphorylation of mitogen-activated protein kinase kinases (MEK1/2), p44/42 mitogen-activated protein kinases (MAPK/ERK1/2), stress-activated protein kinase/c-Jun NH(2)-terminal kinase, Akt/protein kinase B, and p90(RSK). FGF-2-stimulated signaling was more sensitive to heparin's effects than was signaling stimulated by FGF-1. Heparin had an additive effect on the reduced [(3)H]thymidine incorporation in FGF-2-treated AT2 cells caused by inhibition of the MEK/ERK pathway by the MEK inhibitor PD-98059. The data suggest that heparin's known capacity to alter DNA synthesis and, possibly, other biological end points is realized via cross talk between multiple signaling pathways.
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PMID:Heparin affects signaling pathways stimulated by fibroblast growth factor-1 and -2 in type II cells. 1496 81

We investigated the implication of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in the proliferation stimulated by angiotensin II (Ang II) and endothelin-1 (ET-1) in cultured rabbit gingival fibroblasts (CRGF). Ang II stimulated activation of ERK1/2 and the activation was inhibited by CV-11974, an AT1 antagonist, and saralasin, an AT1/AT2 antagonist, but not by PD123,319, an AT2 antagonist in the CRGF. Ang II-stimulated proliferation was inhibited by PD98059 or U0126, selective MEK inhibitors. Furthermore, ET-1 stimulated proliferation via G-protein-coupled ETA receptors, which were identified by Western blot analysis of membrane protein from the CRGF. ET-1 also stimulated activation of ERK1/2 and the activation was inhibited by BQ-123, an ETA inhibitor, and TAK044, an ETA/ETB inhibitor, but not by BQ-788, an ETB inhibitor. ET-1-stimulated proliferation was inhibited by PD98059 or U0126. These findings suggest that ERK1/2 play a role in the signaling process leading to proliferation stimulated by Ang II and ET-1 via G-protein-coupled receptors, AT1 and ETA in CRGF.
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PMID:Inhibition of angiotensin II- and endothelin-1-stimulated proliferation by selective MEK inhibitor in cultured rabbit gingival fibroblastsdagger. 1631 80

To investigate the association between hyperinsulinemia and cardiac hypertrophy, we treated rats with insulin for 7 wk and assessed effects on myocardial growth, vascularization, and fibrosis in relation to the expression of angiotensin II receptors (AT-R). We also characterized insulin signaling pathways believed to promote myocyte growth and interact with proliferative responses mediated by G protein-coupled receptors, and we assessed myocardial insulin receptor substrate-1 (IRS-1) and p110 alpha catalytic and p85 regulatory subunits of phospatidylinositol 3 kinase (PI3K), Akt, MEK, ERK1/2, and S6 kinase-1 (S6K1). Left ventricular (LV) geometry and performance were evaluated echocardiographically. Insulin decreased AT1a-R mRNA expression but increased protein levels and increased AT2-R mRNA and protein levels and phosphorylation of IRS-1 (Ser374/Tyr989), MEK1/2 (Ser218/Ser222), ERK1/2 (Thr202/Tyr204), S6K1 (Thr421/Ser424/Thr389), Akt (Thr308/Thr308), and PI3K p110 alpha but not of p85 (Tyr508). Insulin increased LV mass and relative wall thickness and reduced stroke volume and cardiac output. Histochemical examination demonstrated myocyte hypertrophy and increases in interstitial fibrosis. Metoprolol plus insulin prevented the increase in relative wall thickness, decreased fibrosis, increased LV mass, and improved function seen with insulin alone. Thus our data demonstrate that chronic hyperinsulinemia decreases AT1a-to-AT2 ratio and increases MEK-ERK1/2 and S6K1 pathway activity related to hypertrophy. These changes might be crucial for increased cardiovascular growth and fibrosis and signs of impaired LV function.
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PMID:Hyperinsulinemia: effect on cardiac mass/function, angiotensin II receptor expression, and insulin signaling pathways. 1656 9


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