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

---

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

The pleiotropic cytokine tumor necrosis factor-alpha (TNF alpha) controls the expression of multiple gene products in macrophages and plays an important role in host defense. TNF alpha is recognized by the receptors, CD120a (p55) and CD120b (p75). Ligation of CD120a (p55) by TNF alpha or by anti-receptor agonistic antibodies initiates signal transduction leading to the activation of mitogen-activated protein kinases (MAPKs) (p42mapk/erk2 and p44mapk/erk1). Phosphorylation and activation of MAPK are mediated by MAPK kinase (MEK), a family of Thr/Tyr kinases. In this study, we investigated the preferential involvement of the MEK isoforms MEK1 and MEK2 in the activation of p42mapk/erk2 in mouse macrophages stimulated with TNF alpha. Exposure of macrophages to TNF alpha stimulated a time-dependent increase in the activity of MEK1 as measured by an in vitro kinase assay using kinase-inactive p42mapk/erk2 (rMAPKkd) as substrate in the presence of gamma-[32P]ATP. Maximal activation of MEK1 was detected at 10 min poststimulation and coincided with maximal transphosphorylation of Tyr and Thr residues of rMAPKkd. By contrast, there was no evidence of MEK2 activation in macrophages in response to TNF alpha. These data suggest that MEK1 is the preferred substrate for MEK kinase, the upstream kinase implicated in activation of the MAPK pathway in macrophages by TNF alpha.
...
PMID:Preferential involvement of MEK1 in the tumor necrosis factor-alpha-induced activation of p42mapk/erk2 in mouse macrophages. 749 90

PD 098059 has been shown previously to inhibit the dephosphorylated form of mitogen-activated protein kinase kinase-1 (MAPKK1) and a mutant MAPKK1(S217E,S221E), which has low levels of constitutive activity (Dudley, D. T., Pang, L., Decker, S. J., Bridges, A. J., and Saltiel, A. R. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 7686-7689). Here we report that PD 098059 does not inhibit Raf-activated MAPKK1 but that it prevents the activation of MAPKK1 by Raf or MEK kinase in vitro at concentrations (IC50 = 2-7 microM) similar to those concentrations that inhibit dephosphorylated MAPKK1 or MAPKK1(S217E,S221E). PD 098059 inhibited the activation of MAPKK2 by Raf with a much higher IC50 value (50 microM) and did not inhibit the phosphorylation of other Raf or MEK kinase substrates, indicating that it exerts its effect by binding to the inactive form of MAPKK1. PD 098059 also acts as a specific inhibitor of the activation of MAPKK in Swiss 3T3 cells, suppressing by 80-90% its activation by a variety of agonists. The high degree of specificity of PD 098059 in vitro and in vivo is indicated by its failure to inhibit 18 protein Ser/Thr kinases (including two other MAPKK homologues) in vitro by its failure to inhibit the in vivo activation of MAPKK and MAP kinase homologues that participate in stress and interleukin-1-stimulated kinase cascades in KB and PC12 cells, and by lack of inhibition of the activation of p70 S6 kinase by insulin or epidermal growth factor in Swiss 3T3 cells. PD 098059 (50 microM) inhibited the activation of p42MAPK and isoforms of MAP kinase-activated protein kinase-1 in Swiss 3T3 cells, but the extent of inhibition depended on how potently c-Raf and MAPKK were activated by any particular agonist and demonstrated the enormous amplification potential of this kinase cascade. PD 098059 not only failed to inhibit the activation of Raf by platelet-derived growth factor, serum, insulin, and phorbol esters in Swiss 3T3 cells but actually enhanced Raf activity. The rate of activation of Raf by platelet-derived growth factor was increased 3-fold, and the subsequent inactivation that occurred after 10 min was prevented. These results indicate that the activation of Raf is suppressed and that its inactivation is accelerated by a downstream component(s) of the MAP kinase pathway.
...
PMID:PD 098059 is a specific inhibitor of the activation of mitogen-activated protein kinase kinase in vitro and in vivo. 749 6

p42mapk [mitogen activated protein (MAP) kinase; extracellular signal-regulated protein kinase (ERK)] is a serine/threonine-specific protein kinase that is activated by dual tyrosine and threonine phosphorylation in response to diverse agonists. Both the tyrosine and threonine phosphorylations are necessary for full enzymic activity. A MAP kinase activator recently purified and cloned has been shown to be a protein kinase (MAP kinase kinase) that is able to induce the dual phosphorylation of MAP kinase on both the regulatory tyrosine and threonine sites in vitro. In the present paper we have utilized MAP kinase mutants altered in the sites of regulatory phosphorylation to show, both in vivo and in vitro, that phosphorylation of the tyrosine and the threonine can occur independently of one another, with no required order of phosphorylation. We also utilized kinase-defective variants of MAP kinase with mutations in either the ATP-binding loop or the catalytic loop, and obtained data suggesting that the activity or structure of the catalytic loop of MAP kinase plays an important role in its own dual phosphorylation.
...
PMID:Dual phosphorylation and autophosphorylation in mitogen-activated protein (MAP) kinase activation. 750 57

The p53 tumor suppressor protein is tightly regulated in the cell and is phosphorylated at multiple sites by several different protein kinases. We have investigated the phosphorylation of p53 by mitogen-activated protein (MAP) kinase, a protein kinase that plays a central role in mediating many mitogenic and differentiation signals. Recombinant wild-type mouse p53 was phosphorylated in vitro by activated recombinant p42-MAP kinase but not by inactive MAP kinase or by the activating protein, MAP kinase kinase. Phosphorylation of p53 by MAP kinase occurred at two N-terminal sites, threonine residues 73 and 83. Tryptic phosphopeptides of recombinant p53 phosphorylated in vitro by MAP kinase comigrated on two-dimensional maps with p53 from SV3T3 cells labeled in vivo with [32P]orthophosphate, suggesting that MAP kinase targets a site in p53 that is phosphorylated in the cell. Following serum stimulation of quiescent C57MG cells, two p53 kinases, which were resolved by chromatography on Mono Q, were stimulated 15-20-fold within 5 min. Each of these kinase activities co-eluted with myelin basic protein kinase activity and could be inactivated following treatment with protein phosphatase 2A, a serine/threonine phosphatase, or leukocyte antigen receptor, a protein tyrosine phosphatase, suggesting that these activities were members of the MAP kinase family. The two kinase activities from the lysates targeted the same phosphorylation sites on p53 as the purified recombinant MAP kinase. These protein kinase activities were also stimulated following exposure of the cells to ultraviolet radiation, but with slightly delayed kinetics. Phorbol ester treatment of SV3T3 cells led to increased phosphorylation of the peptide containing the residues targeted by MAP kinase. The data suggest that p53 may be phosphorylated by MAP kinase physiologically and that this interaction may be involved in the cell's response to UV exposure, growth factor stimulation, or transformation by oncogenes.
...
PMID:Phosphorylation of the tumor suppressor protein p53 by mitogen-activated protein kinases. 751 Jul 6

In the renal medulla during antidiuresis, the extracellular fluid becomes hyperosmotic. Madin-Darby canine kidney (MDCK) epithelial cells adapt in hyperosmotic conditions and serve as a useful tissue culture model for cellular responses to hyperosmolality. We demonstrate that hyperosmolality stimulates phospholipase C, Raf-1 kinase mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase activities and that it increases phosphorylation of Raf-1 kinase, and p42 MAP kinase in MDCK cells. Stimulation of these kinases is osmolality-dependent (from 300 to 600 mosm/kg H2O). The time course of activation is sequential; the peak stimulation for Raf-1 kinase is at 5 min, at 10 min for MAP kinase kinase and MAP kinase, and at 20 min for S6 kinase. The activation of Raf-1 kinase and MAP kinase is inhibited by phorbol 12-myristate 13-acetate pretreatment in the presence of calphostin C or H-7. Tyrosine kinase inhibitors (genistein, herbimycin) do not significantly suppress hyperosmolality-induced MAP kinase activity. The increase of Ins-1,4,5-P3 levels by hyperosmolality suggests that activation of these kinases is mediated at least partially via activation of phospholipase C. Thus, hyperosmolality stimulates the serine/threonine kinases, Raf-1 kinase, MAP kinase kinase, MAP kinase, and S6 kinase, via predominantly protein kinase C-dependent, tyrosine kinase-independent pathways in MDCK cells.
...
PMID:Sequential activation of Raf-1 kinase, mitogen-activated protein (MAP) kinase kinase, MAP kinase, and S6 kinase by hyperosmolality in renal cells. 752 42

In KB epidermoid cells, we previously showed that interleukin-1 alpha (IL-1) and various mitogens activate the mitogen-activated protein (MAP) kinases ERK1 and ERK2, which phosphorylate both myelin basic protein (MBP) and a peptide containing Thr669 of the epidermal growth factor receptor. In cell-free extracts made from gingival fibroblasts treated with platelet-derived growth factor or HepG2 hepatoma cells stimulated with phorbol myristate acetate, MBP and Thr669 kinase were both elevated 4-fold, and ERK1 and ERK2 were tyrosine-phosphorylated. In these cells IL-1 activated a kinase(s) that phosphorylated Thr669 peptide but not MBP and failed to cause tyrosine phosphorylation of ERK1/ERK2. Ceramide has been proposed as an intracellular mediator of IL-1 action, but C2-ceramide or sphingosine stimulated predominantly MBP-specific kinase activity in fibroblasts and had no effect in HepG2 cells. p54 MAP kinase (also called stress-activated protein kinase) is a c-Jun kinase first isolated from livers of cycloheximide-treated rats. After IL-1 stimulation, immunoprecipitates of lysates made from all three cell types with specific anti-p54 MAP kinase serum contained Thr669 and c-Jun phosphorylating activity, whereas precipitates from unstimulated cells contained no detectable p54 kinase activity. The major peak of IL-1-stimulated HepG2 Thr669 kinase activity co-chromatographed on Mono Q and phenyl-Superose with immunodetectable p54 MAP kinase. IL-1 did not cause p21ras activation in any cell type. Induction of Thr 669 kinase activity was not abrogated by elevation of cAMP levels, which has been shown to interfere with the activation of Raf-1. We could not detect MAP kinase kinase phosphorylating activity in unfractionated lysates made from IL-1-stimulated fibroblasts or HepG2 cells. KB cells contained a small amount of this activity, but it was not precipitated with an anti-Raf-1 antibody. We conclude that most of the IL-1-activated Thr669 kinase activity in fibroblasts and HepG2 cells, and a portion in KB cells, is due to p54 MAP kinase and that its activation is Ras-, Raf-, and MAP kinase kinase-independent.
...
PMID:Interleukin-1 activates p54 mitogen-activated protein (MAP) kinase/stress-activated protein kinase by a pathway that is independent of p21ras, Raf-1, and MAP kinase kinase. 752 98

Mitogen-activated protein (MAP) kinases are a family of serine/threonine kinases implicated in the control of cell proliferation and differentiation. We have found that activated p42mapk is a target for the phosphoepitope antibody MPM-2, a monoclonal antibody that recognizes a cell cycle-regulated phosphoepitope. We have determined that the MPM-2 antibody recognizes the regulatory region of p42mapk. Binding of the MPM-2 antibody to active p42mapk in vitro results in a decrease in p42mapk enzymatic activity. The MPM-2 phosphoepitope can be generated in vitro on bacterially expressed p42mapk by phosphorylation with either isoform of MAP kinase kinase (MKK), MKK1, or MKK2. Analysis of p42mapk proteins mutated in their regulatory sites shows that phosphorylated Thr-183 is essential for the binding of the MPM-2 antibody. MPM-2 binding to Thr-183 is affected by the amino acid present in the other regulatory site, Tyr-185. Substitution of Tyr-185 with phenylalanine results in strong binding of the MPM-2 antibody, whereas substitution with glutamic acid substantially diminishes MPM-2 antibody binding. The MPM-2 phosphoepitope antibody recognizes an amino acid domain incorporating the regulatory phosphothreonine on activated p42mapk in eggs during meiosis and in mammalian cultured cells during the G0 to G1 transition.
...
PMID:The MPM-2 antibody inhibits mitogen-activated protein kinase activity by binding to an epitope containing phosphothreonine-183. 753 73

The mitogen-activated protein kinase (MAPK) also known as extracellular signal-regulated kinase (ERK) plays a crucial role in various signal transduction pathways. ERK is activated by its upstream activator, MEK, via threonine and tyrosine phosphorylation. ERK activity in the cell is tightly regulated by phosphorylation and dephosphorylation. Here we report the cloning and characterization of a novel dual specific phosphatase, HVH2, which may function in vivo as a MAP kinase phosphatase. The deduced amino acid sequence of HVH2 shows significant identity to the VH1-related dual specific phosphatase family. In addition, the N-terminal region of HVH2 also displays sequence identity to the cell cycle regulator, Cdc25 phosphatase. Recombinant HVH2 phosphatase exhibited a high substrate specificity toward activated ERK and dephosphorylated both threonine and tyrosine residues of activated ERK1 and ERK2. Immunofluorescence studies with an epitope-tagged HVH2 showed that the enzyme was localized in cell nucleus. Transfection of HVH2 into NIH3T3 cells inhibited the v-src and MEK-induced transcriptional activation of serum-responsive element containing promoter, consistent with the notion that HVH2 promotes the inactivation of MAP kinase. HVH2 mRNA showed an expression pattern distinct from CL100 (human homologue of mouse MKP1) and PAC1, two previously identified MAP kinase phosphatases. Our data suggest a possible role of HVH2 in MAP kinase regulation.
...
PMID:Isolation and characterization of a novel dual specific phosphatase, HVH2, which selectively dephosphorylates the mitogen-activated protein kinase. 753 68

Protein phosphorylation has evolved as the most versatile posttranslational modification widely used by cells. Signal transduction pathways mediated by activation of MAP kinases and protein kinase C trigger the exit of cells from the quiscence (Go-->G1 transition). Indeed, binding of growth factors at the cell surface triggers their receptors, usually possessing a tyrosine kinase on the cytoplasmic side, to phosphorylate other molecules passing on the information sequentially to GRB2 protein, to p21ras, to c-Raf-1, to MAP kinase kinase, to MAP kinase, to p90rsk, to transcription factors. Activated PKC, MAP kinase, and pp90src can translocate to the nucleus where they phosphorylate a number of protein transcription regulators in a cell cycle-dependent manner or in response to cell stimulation for exit from quiescence. The cell cycle is mainly regulated by p34cdc2 or otherwise called cdc2 in association with cyclins B at G2/M and by Cdk2 in association with cyclins A, D1, and E at G1/S checkpoints; phosphorylation of histone H1 and lamins by cdc2 triggers chromosome assembly and nuclear envelope breakdown, respectively, as a prelude to mitosis. Cdc2 activities functioning as a G2/M regulator are controlled by its phosphorylation and dephosphorylation at Ser/Thr residues. MAP kinases might be the missing link in the chain connecting the Go to G1 transition with the cell cycle regulation, whereas phosphorylation of replication protein factors, retinoblastoma, and p53 might link the G1 to S transition with the control of DNA synthesis. A number of transcription factors are known to stimulate DNA replication, including p53, c-Myc, AP-1, Oct-1, T-antigen; the DNA binding activities of all these proteins and their interaction with other transcription factors are controlled by phosphorylation. The nuclear import of several proteins including NF kappa B, Dorsal, glucocorticoid receptor, ISGF3, rNFIL-6, T antigen, and the kinases PKC, MAP, and p90rsk, are dependent on their phosphorylation at specific sites. Histone phosphorylation stimulated at discrete stages of the cell cycle or in response to cAMP or other stimuli might induce profound changes in chromatin organization.
...
PMID:Phosphorylation of transcription factors and control of the cell cycle. 754 80

Analysis of genes involved in yeast cell wall beta-glucan assembly has led to the isolation of EXG1, PBS2 and PTC1. EXG1 and PBS2 were isolated as genes that, when expressed from multicopy plasmids, led to a dominant killer toxin-resistant phenotype. The PTC1 gene was cloned by functional complementation of the calcofluor white-hypersensitive mutant cwh47-1. PTC1/CWH47 is the structural gene for a type 2C serine/threonine phosphatase, EXG1 codes for an exo-beta-glucanase, and PBS2 encodes a MAP kinase kinase in the Pbs2p-Hog1p signal transduction pathway. Overexpression of EXG1 on a 2 mu plasmid led to reduction in a cell wall beta 1,6-glucan and caused killer resistance in wild type cells; while the exg1 delta mutant displayed modest increases in killer sensitivity and beta 1,6-glucan levels. Disruption of PTC1/CWH47 and overexpression of PBS2 gave rise to similar beta-glucan related phenotypes, with higher levels of EXG1 transcription, increased exo-beta-glucanase activity, reduced beta 1,6-glucan levels, and resistance to killer toxin. Genetic analysis revealed that loss of function of the PBS2 gene was epistatic to PTC1/CWH47 disruption, indicating a functional role for the Ptc1p/Cwh47p phosphatase in the Pbs2p-Hog1p signal transduction pathway. These results suggest that Ptc1p/Cwh47p and Pbs2p play opposing regulatory roles in cell wall glucan assembly, and that this is effected in part by modulating Exg1p activity.
...
PMID:Regulation of cell wall beta-glucan assembly: PTC1 negatively affects PBS2 action in a pathway that includes modulation of EXG1 transcription. 756 87


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---