Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.24 (mitogen-activated protein kinase)
 95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mitogen-activated protein (MAP) kinases are regarded as switch kinases in the phosphorylation cascade initiated by various agonists. We have investigated whether endothelins (ET), which are constrictor and mitogenic isopeptides, can increase MAP kinase activity in rat mesangial cells, using bovine myelin basic protein (MBP) as a substrate for an in vitro kinase assay. Treatment of quiescent mesangial cells with ET-1 rapidly stimulated a kinase activity which phosphorylated exogenous MBP. This stimulation was dose-dependent, with threshold responses at 1 nM-ET-1. Epidermal growth factor and thrombin also activated this kinase in mesangial cells. We also examined the ET signal transduction pathways leading to activation of MBP kinase. Pertussis toxin had no effect on ET-stimulated MBP kinase activity. Stimulation of protein kinase C by phorbol ester increased MBP kinase activity, and down-regulation of PKC partially inhibited ET-stimulated MBP kinase as well as phorbol ester-stimulated MBP kinase activity. Interestingly, genestein, an inhibitor of protein tyrosine kinases, partially inhibited MBP kinase stimulated by ET but not by phorbol esters. These results suggest that ET stimulates MBP kinase activity in rat mesangial cells via at least two pathways: one which is protein kinase C-dependent and a second one that involves a protein tyrosine kinase. Finally, by raising rabbit antibodies against the two forms of MAP kinase, p44mapk and p42mapk, we demonstrated that both isoforms are expressed in mesangial cells. Antibody alpha 1 Cp42 specifically immunoprecipitated p42mapk and allowed us to demonstrate that ET stimulates MBP kinase activity in the p42mapk immunocomplex. In conclusion, we have provided evidence that, in rat mesangial cells, MAP kinases are rapidly activated by ET-1, a regulatory process that involves at least protein kinase C activation and also a contribution of a tyrosine kinase not yet characterized.
 ...
PMID:Endothelin rapidly stimulates mitogen-activated protein kinase activity in rat mesangial cells. 128 Jan 3

Incubation of Swiss 3T3 or L929 cells with tumor necrosis factor (TNF) leads to the rapid stimulation of several cytosolic Ser/Thr kinases active toward myelin basic protein, the S6 peptide (RRLSSLR), the G peptide (SPQPSRRGSESSEE), and Kemptide (LRRASLG). This confirms the hypothesis that kinases other than protein kinases A and C may be involved in the TNF signal transduction. Chromatography on Mono Q resolved multiple kinase peaks with each substrate tested and moreover revealed a TNF-mediated casein kinase-2 activation in both cell lines, measurable with the specific RRREEESEEE peptide or with the G peptide. The TNF-stimulated myelin basic protein kinases-1 and -2 were identified as extracellular signal-regulated kinases-2 and -1, respectively, based on their elution pattern on Mono Q chromatography, their inactivation by protein phosphatase action, their reaction with phosphothreonine and phosphotyrosine antibodies, and by their migration on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as 42- and 44-kDa proteins recognized by anti-extracellular signal-regulated kinase antibodies.
 ...
PMID:Tumor necrosis factor stimulates multiple serine/threonine protein kinases in Swiss 3T3 and L929 cells. Implication of casein kinase-2 and extracellular signal-regulated kinases in the tumor necrosis factor signal transduction pathway. 128 78

Treatment of PC12 cells with nerve growth factor (NGF) induces a rapid increase in tyrosine phosphorylation of multiple cellular proteins. Expression of a dominant inhibitory Ras mutant specifically blocked NGF- and TPA-induced tyrosine phosphorylation of two proteins of approximately 42 and 44 kd. Conversely, expression of an oncogenic variant of Ras induced tyrosine phosphorylation of the same 42 and 44 kd proteins. The 44 kd protein was immunoprecipitated with an antibody directed against extracellular signal-regulated kinase 1/mitogen-activated protein kinase (MAPK) and the 42 kd protein comigrated with a 42 kd MAPK, indicating that at least one and probably both Ras-regulated phosphoproteins are MAPKs. In addition, MAPK activation, as measured by in vitro phosphorylation of myelin basic protein, was also regulated by Ras. Ras was not required for NGF-induced activation of Trk or tyrosine phosphorylation of PLC-gamma 1. Thus, NGF-induced tyrosine phosphorylation occurs both prior to and following Ras action, and Ras plays a critical role in the NGF- and TPA-induced tyrosine phosphorylation of MAPKs.
 ...
PMID:Ras is essential for nerve growth factor- and phorbol ester-induced tyrosine phosphorylation of MAP kinases. 131 92

We have previously demonstrated that growth hormone (GH) promotes an increase in tyrosine kinase activity associated with the GH receptor. To gain insight into the role of GH-dependent tyrosine kinase activity in signaling by GH, we investigated the possibility that GH might stimulate MAP kinase, a serine/threonine/tyrosine kinase thought to be a common element in tyrosine kinase-initiated response cascades. Treatment of 3T3-F442A fibroblasts with 100 ng/ml GH results in a 3-6-fold increase in the ability of cell-free extracts to phosphorylate MAP-2 and myelin basic protein. GH-stimulated kinase activity is unaffected by heparin, H7, or cAMP-dependent protein kinase inhibitor peptide, partially reduced by staurosporin and inhibited by fluoride and calcium ions, indicating that the kinase is not protein kinase C or A, casein kinase, or a calcium/calmodulin-dependent protein kinase. Based on gel permeation chromatography, the molecular mass of the GH-stimulated MAP kinase is approximately kDa. Furthermore, anti-phosphotyrosine antibodies revealed the GH-dependent appearance of two phosphotyrosine-containing proteins in cell-free lysates of GH-treated cells that co-migrate with proteins recognized by anti-MAP kinase antibodies. The GH-dependent increase in MAP kinase activity displays a biphasic time course and is dependent on the concentration of GH applied to the cells. GH-dependent MAP kinase activity, partially purified by Mono-Q chromatography, is inactivated by treatment with alkaline phosphatase. Addition of H7 to the cells prior to the addition of GH has no effect, whereas addition of H8 increases MAP kinase activity in control cells with no effect in GH-treated cells, indicating that protein kinase C is unlikely to be an intermediary in the GH-dependent stimulation of MAP kinase activity. These findings indicate that signaling by GH in 3T3-F443A cells may, at least in part, utilize a kinase cascade similar to those that have been proposed for other membrane receptors with associated tyrosine kinase activity.
 ...
PMID:Stimulation by growth hormone of MAP kinase activity in 3T3-F442A fibroblasts. 131 28

A synthetic peptide modeled after the major threonine (T669) phosphorylation site of the epidermal growth factor (EGF) receptor was an efficient substrate (apparent Km approximately 0.45 mM) for phosphorylation by purified p44mpk, a MAP kinase from sea star oocytes. The peptide was also phosphorylated by a related human MAP kinase, which was identified by immunological criteria as p42mapk. Within 5 min of treatment of human cervical carcinoma A431 cells with EGF or phorbol myristate acetate (PMA), a greater than 3-fold activation of p42mapk was measured. However, Mono Q chromatography of A431 cells extracts afforded the resolution of at least three additional T669 peptide kinases, some of which may be new members of the MAP kinase family. One of these (peak I), which weakly adsorbed to Mono Q, phosphorylated myelin basic protein (MBP) and other MAP kinase substrates, immunoreacted as a 42 kDa protein on Western blots with four different MAP kinase antibodies, and behaved as a approximately 45 kDa protein upon Superose 6 gel filtration. Another T669 peptide kinase (peak IV), which bound more tightly to Mono Q than p42mapk (peak II), exhibited a nearly identical substrate specificity profile to that of p42mapk, but it immunoreacted as a 40 kDa protein only with anti-p44mpk antibody on Western blots, and eluted from Superose 6 in a high molecular mass complex of greater than 400 kDa. By immunological criteria, the T669 peptide kinase in Mono Q peak III was tentatively identified as an active form of p34cdc2 associated with cyclin A. The Mono Q peaks III and IV kinases were modestly stimulated following either EGF or PMA treatments of A431 cells, and they exhibited a greater T669 peptide/MBP ratio than p42mapk. These findings indicated that multiple proline-directed kinases may mediate phosphorylation of the EGF receptor.
 ...
PMID:Identification of epidermal growth factor Thr-669 phosphorylation site peptide kinases as distinct MAP kinases and p34cdc2. 132 Apr 11

Two peaks of mitogen-activated protein (MAP) kinase activator activity are resolved upon ion exchange chromatography of cytosolic extracts from epidermal growth factor-stimulated A431 cells. Two forms of the activator (1 and 2) have been purified from these peaks, using chromatography on Q-Sepharose, heparin-agarose, hydroxylapatite, ATP-agarose, Sephacryl S-300, Mono S, and Mono Q. The two preparations each contained one major protein band with an apparent molecular mass of 46 or 45 kDa, respectively, on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Evidence identifying the MAP kinase activators as the 46- and 45-kDa proteins is presented. Using inactive mutants of MAP kinase as potential substrates, it was found that each preparation of MAP kinase activator catalyzes phosphorylation of the regulatory residues, threonine 188 and tyrosine 190, of Xenopus MAP kinase. These results support the concept that the MAP kinase activators are protein kinases. These MAP kinase kinases demonstrate an apparent high degree of specificity toward the native conformation of MAP kinase, although slow autophosphorylation on serine, threonine, and tyrosine residues and phosphorylation of myelin basic protein on serine and threonine residues is detected as well.
 ...
PMID:Purification and characterization of mitogen-activated protein kinase activator(s) from epidermal growth factor-stimulated A431 cells. 132 Nov 46

Nerve growth factor-stimulated mitogen-activated protein kinase (pp42/44MAP) kinase was characterized by sequential column chromatography on DEAE-Sephacel, phenyl-Sepharose CL4B, and S-200. The kinase displayed an apparent molecular mass of 42 kDa and reacted with an antiphosphotyrosine antibody. Peptide mapping of myelin basic protein revealed the presence of one phosphopeptide that was phosphorylated on Thr-97. pp42/44MAP kinase activity was dependent on Mg2+ and inhibited by K252a both in vitro and in vivo. Nerve growth factor-stimulated kinase activation was diminished by down-regulation of protein kinase C with 200 nM 12-phorbol 13-myristate acetate or with staurosporine (1 nM), a protein kinase C inhibitor. Genistein, a protein tyrosine kinase inhibitor, blocked nerve growth factor-mediated neurite extension as well as diminished activation of pp42/44MAP kinase. Our data demonstrate that activation of this kinase system by nerve growth factor displays a requirement for both protein kinase C as well as protein tyrosine kinase. In addition, other agents that are capable of promoting neurite outgrowth in PC12 cells, such as fibroblast growth factor or dibutyryl cyclic AMP, do so independently of activating this kinase system.
 ...
PMID:pp42/44MAP kinase is a component of the neurogenic pathway utilized by nerve growth factor in PC12 cells. 132 67

The subcellular distribution and regulation of MAP kinase isoforms in chicken hepatoma DU249 cells was investigated with antibodies directed against peptides patterned after sequences in the mitogen-activated protein (MAP) kinases, sea star p44mpk, and rat p44erk1. MonoQ chromatography of cytosol from these cells afforded the resolution of at least four peaks of myelin basic protein (MBP) phosphotransferase activity, but only one of these (peak II) was stimulated in extracts from phorbol ester-treated cells. A 40- to 41-kDa (p41) doublet on Western blots detected with three different MAP kinase antibodies was coincident with peak II, and it probably corresponded to the avian homolog of p42mapk/erk2. Immunofluorescent studies with DU249 cells and chicken embryo fibroblasts revealed that most of the cross-reactive protein with at least two different MAP kinase antibodies was distributed in the nucleus. Subcellular fractionation studies confirmed a predominantly nuclear localization for p41 MAP kinase. Nocodazole arrest of DU249 cells was exploited for the detection of an M-phase-activated MBP kinase that was resolved from p41 MAP kinase by phenyl-Superose chromatography. Western blotting analysis with antibodies for the cdc2-encoded protein kinase and p13suc1-agarose binding studies allowed positive identification of this MBP kinase as p34cdc2.
 ...
PMID:Immunological characterization of avian MAP kinases: evidence for nuclear localization. 132 21

An insulin-stimulated phosphorylation cascade was examined in rat liver after insulin injection via a portal vein by the use of immune complex kinase assays specific to the mitogen-activated protein (MAP) kinase and S6 kinase II homologue (rsk) kinase. We have prepared an antibody against the peptide consisting of a carboxyl-terminal portion of the extracellular signal-regulated kinase 1 (alpha C92), one of the MAP kinases, and an antibody against the peptide consisting of the carboxyl terminus of the mouse S6 kinase II homologue (alpha rsk(m)C). In alpha C92 immune complex assay, maximal activation of rat liver MAP kinases (approximately 4.3-fold) were observed 4.5 min after insulin injection. We also observed an insulin-stimulated MAP kinase activity (approximately 3-fold) in liver extracts from insulin-treated rat in fractions eluted from phenyl-Sepharose with 30-50% ethylene glycol. Kinase assay in myelin basic protein (MBP)-containing gel after sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by denaturation with 6 M guanidine HCl, and renaturation revealed that insulin injection stimulated the kinase activity of the 42- and 44-kDa proteins, which corresponded to the two distinct MAP kinases. In alpha rsk(m)C immune complex assay, maximal stimulation (approximately 5-fold) of the S6 peptide (Arg-Arg-Leu-Ser-Ser-Leu-Arg-Ala) kinase activity was observed 7.5 min after insulin injection. In addition, MAP kinases purified from insulin-treated rat liver were able to activate S6 peptide kinase activity in vitro in alpha rsk(m)C immunoprecipitates from untreated rat liver, accompanied by the appearance of several phosphorylated bands including a major band at 88 kDa. We also examined whether insulin injection stimulates the MAP kinase activator (Ahn, N. G., Seger, R., Bratlien, R. L., Diltz, C. D., Tonks, N. K., and Krebs, E. G. (1991) J. Biol. Chem. 266, 4220-4227) in rat liver. Using recombinant Xenopus MAP kinase, fractions of Q-Sepharose eluted early in the NaCl gradient were found to have MAP kinase activator activity accompanied by the phosphorylation of 42-kDa recombinant Xenopus MAP kinase. From these data, we demonstrate three tiers of a cascade composed of the MAP kinase activator, MAP kinases, and an S6 peptide kinase activity in rat liver under physiological conditions in the intact animal.
 ...
PMID:Sequential activation of MAP kinase activator, MAP kinases, and S6 peptide kinase in intact rat liver following insulin injection. 132 22

The activation of insulin-stimulated protein-serine/threonine kinases has been investigated in CHO cell lines transfected with cDNAs encoding either wild-type or mutant human insulin receptors. (1) Insulin treatment of CHO cells over-expressing wild-type insulin receptors resulted in the rapid and substantial (5-10-fold) activation of cytosolic protein kinases which phosphorylated myelin basic protein, Kemptide and two peptide substrates based on sites phosphorylated on ribosomal protein S6 in vivo. (2) Further fractionation of cytosolic extracts by MonoQ chromatography revealed two peaks of insulin-stimulated myelin basic protein kinase activity which were highly related to the previously described mitogen-activated protein (MAP) kinases ERK1 and ERK2. In addition, at least two major peaks of S6 kinase activity were resolved, which exhibited properties similar to the 70 kDa and 90 kDa S6 kinases described by others; the predominant effect of insulin was on the activity of the 90 kDa enzyme and was in excess of 10-fold. (3) MonoQ fractionation of extracts from parental CHO cells, or cells expressing kinase-deficient receptors, showed all insulin-stimulated peaks of activity to be almost completely absent. (4) Further studies demonstrated that substitution of tyrosine residues 1162 and 1163 (or 1162 alone) with phenylalanine led to a substantial reduction in the ability of insulin to stimulate these protein kinase activities when assayed in cytosolic extracts. In contrast, deletion of 69 amino acids from the C-terminus of the insulin receptor beta-subunit caused a leftward shift in the insulin dose-response curve of the MAP kinase activity, but apparently not in that of the 90 kDa S6 kinase activity.
 ...
PMID:Characterization of insulin-stimulated protein serine/threonine kinases in CHO cells expressing human insulin receptors with point and deletion mutations. 132 27


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