Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.11.18 (MAP)
 7,412 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bovine myelin basic protein (MBP) was found to be an excellent in vitro substrate (apparent Km = 50 microM) for MAP (mitogen-activated protein) kinase and can be used in lieu of microtubule-associated protein 2 for purification and functional studies of the enzyme. MBP phosphotransferase activity co-purified with MAP kinase during sequential DE52, phenyl-Superose, and gel filtration chromatography, and kinase activities for the two substrates were co-regulated by mitogen stimulation. MAP kinase phosphorylated MBP exclusively on threonine, and only one major phosphopeptide was generated by digestion with trypsin or endoproteinase Lys-C. Using mass spectrometry, we determined that the phosphorylation site is threonine 97, present in the conserved triproline loop of MBP, with (partial) sequence -Thr-Pro-Arg-Thr97-Pro-Pro-Pro-. Thr97 is a known in vivo phosphorylation site in MBP although enzymes capable of phosphorylating this site have not been identified previously. MAP kinase phosphorylated peptide 88-109 from rabbit MBP and a synthetic peptide 91-109 from human MBP but did not phosphorylate either the histone H1 peptide, utilized by p34cdc2, or the peptide substrate for the recently described proline-directed kinase. Thus, the sequence surrounding threonine 97 in bovine MBP may contain essential features of a recognition sequence for MAP kinase.
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PMID:Identification by mass spectrometry of threonine 97 in bovine myelin basic protein as a specific phosphorylation site for mitogen-activated protein kinase. 170 Sep 79

Treatment of BC3H1 myocytes or 3T3-L1 fibroblasts with fluoroaluminate (AlF4-), a direct activator of G proteins, increased the tyrosine phosphorylation of a 42-kDa cytosolic protein. AlF4- induced a parallel increase in protein kinase activity toward myelin basic protein (MBP) in partially purified cell extracts. To test whether AlF4- was activating the 42-kDa MAP (mitogen-activated protein) kinase, extracts from AlF4--treated cells were taken through the chromatographic steps routinely used to purify MAP kinase from growth factor-stimulated cells. Following phenyl-Superose chromatography, a peak of MBP kinase activity eluted at a position characteristic of MAP kinase. Immunoblotting of the active fractions with anti-phosphotyrosine antibodies revealed a single reactive protein band of Mr 42,000. Stimulation of MAP kinase by AlF4- was rapid, peaking within 15 min and persisting for at least 1 h. In contrast, the activation of MAP kinase by insulin was transient, characteristic of its activation by growth factors in other cell types. Although concentrations of sodium fluoride greater than 1 mM also activated MAP kinase, this effect was shown to be dependent upon the simultaneous presence of aluminum ions in the medium. Activation of MAP kinase by AlF4- was not affected by either cellular depletion of protein kinase C or pretreatment of cells with pertussis toxin. Potential sites of action of AlF4- are discussed. These findings suggest that activation of a G protein(s) in intact cells can initiate events that result in tyrosine phosphorylation and activation of MAP kinase.
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PMID:Activation of mitogen-activated protein kinase in BC3H1 myocytes by fluoroaluminate. 170 25

We prepared a monoclonal antibody to microtubule-associated protein 1 (MAP 1), one of the two major high molecular weight MAP found in microtubules isolated from brain tissue. We found that MAP 1 can be resolved by SDS PAGE into three electrophoretic bands, which we have designated MAP 1A, MAP 1B, and MAP 1C in order of increasing electrophoretic mobility. Our antibody recognized exclusively MAP 1A, the most abundant and largest MAP 1 polypeptide. To determine the distribution of MAP 1A in nervous system tissues and cells, we examined tissue sections from rat brain and spinal cord, as well as primary cultures of newborn rat brain by immunofluorescence microscopy. Anti-MAP 1A stained white matter and gray matter regions, while a polyclonal anti-MAP 2 antibody previously prepared in this laboratory stained only gray matter. This confirmed our earlier biochemical results, which indicated that MAP 1 is more uniformly distributed in brain tissue than MAP 2 (Vallee, R.B., 1982, J. Cell Biol., 92:435-442). To determine the identity of cells and cellular processes immunoreactive with anti-MAP 1A, we examined a variety of brain and spinal cord regions. Fibrous staining of white matter by anti-MAP 1A was generally observed. This was due in part to immunoreactivity of axons, as judged by examination of axonal fiber tracts in the cerebral cortex and of large myelinated axons in the spinal cord and in spinal nerve roots. Cells with the morphology of oligodendrocytes were brightly labeled in white matter. Intense staining of Purkinje cell dendrites in the cerebellar cortex and of the apical dendrites of pyramidal cells in the cerebral cortex was observed. By double-labeling with antibodies to MAP 1A and MAP 2, the presence of both MAP in identical dendrites and neuronal perikarya was found. In primary brain cell cultures anti-MAP 2 stained predominantly cells of neuronal morphology. In contrast, anti-MAP 1A stained nearly all cells. Included among these were neurons, oligodendrocytes and astrocytes as determined by double-labeling with anti-MAP 1A in combination with antibody to MAP 2, myelin basic protein or glial fibrillary acidic protein, respectively. These results indicate that in contrast to MAP 2, which is specifically enriched in dendrites and perikarya of neurons, MAP 1A is widely distributed in the nervous system.
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PMID:Widespread distribution of the major polypeptide component of MAP 1 (microtubule-associated protein 1) in the nervous system. 636 69

Intracellular signaling pathways regulating vascular smooth muscle (VSM) cell growth and hypertrophy can be initiated by activation of receptor tyrosine kinases and/or protein kinase C (PKC). Mitogen-activated protein kinases (MAP kinases) are cytosolic serine/threonine kinases, proposed to act as a point of convergence for diverse growth factors utilizing these signaling pathways. The goals of this study were (1) to determine whether MAP kinase is expressed in cultured rat aortic VSM, (2) to assess the activation of MAP kinase by known proliferative and hypertrophic stimuli, and (3) to determine if stimulation of a PKC-dependent signaling pathway in these cells results in MAP kinase activation. MAP kinase activity was measured in cytosolic extracts of aortic VSM by quantifying myelin basic protein phosphorylation. Three peaks of activity were resolved chromatographically and identified as MAP kinase isoforms (MW 42, 44, and 46 kDa) by immunoblotting with antipeptide antibodies specific for MAP kinase. MAP kinase activity in quiescent growth-arrested cells (157 +/- 19 pmole 32P/min/mg) was markedly stimulated within 15 min by known mitogens (10% serum, 731 +/- 40 pmole 32P/min/mg; 40 ng/ml PDGF, 670 +/- 105 pmole 32P/min/mg; P < 0.01) and partially sustained for at least 90 min (serum, 606 +/- 34 pmole 32P/min/mg; PDGF, 323 +/- 59 pmole 32P/min/mg P < 0.05). Angiotensin II (AII, 0.1 microM) and a pharmacological PKC activator, phorbol 12,13-dibutyrate (PDB, 0.1 microM), are reported to be nonmitogenic hypertrophic stimuli in these cells. These stimuli transiently increased MAP kinase activity with a peak at 5 min (AII, 328 +/- 15 pmole 32P/min/mg; PDB, 592 +/- 41 pmole 32P/min/mg; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of MAP kinase activity by growth stimuli in vascular smooth muscle. 804 Nov 41

Prostaglandin H2 (PGH2) and thromboxane A2 (TXA2) are potent activators of platelets and vascular smooth muscle whose responses are mediated through a common G-protein coupled receptor (TXA2/PGH2 receptor). Despite the many studies describing their ability to aggregate platelets and contract vascular smooth muscle, little is known concerning the potential mitogenic capabilities of these autocoids. Mitogen-activated protein kinases (MAP kinases) and ribosomal S6 kinases are well characterized intracellular mediators involved in proliferation of cells. The present study was designed to examine the activation of MAP kinase and S6 kinase in guinea pig coronary artery smooth muscle cells (CASMC) in response to stimulation by a TXA2/PGH2 mimetic, I-BOP ([1S-(1 alpha,2 beta(5Z),3 alpha(1E,3R*),4 alpha)]-7-[3-(3-hydroxy-4-(4'- iodophenoxy)-1-butenyl)-7-oxabicyclo-[2.2.1]heptan-2-yl]-5-h eptenoic acid). Equilibrium radioligand binding assays using [125I]BOP defined a single class of high affinity TXA2/PGH2 receptors on monolayers of guinea pig CASMC (Kd = 0.18 +/- 0.03 nM; 26,476 +/- 3,600 sites/cell; 0.08 +/- 0.01 pmol/mg of protein; n = 12). I-BOP produced a concentration-dependent increase in [3H]thymidine incorporation in these cells (EC50 = 0.3 nM) which was inhibited by a series of TXA2/PGH2 receptor antagonists as well as by verapamil and staurosporine. I-BOP also produced a time-dependent increase in the activation of kinases phosphorylating myelin basic protein (MBP; a substrate for MAP kinase) and RRLSSLRA (S6 peptide; a substrate for pp85rsk kinase), reaching a peak activation between 5 and 10 min. Stimulated MBP kinases were identified as ERK1 and ERK2. The activation of these kinases by I-BOP was inhibited by the TXA2/PGH2 receptor antagonist SQ29548 and also by staurosporine. These results indicate that I-BOP, a TXA2/PGH2 mimetic, produces growth of coronary artery vascular smooth muscle cells, which is preceded by activation of MAP kinase and S6 kinase.
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PMID:Thromboxane A2/prostaglandin H2-stimulated mitogenesis of coronary artery smooth muscle cells involves activation of mitogen-activated protein kinase and S6 kinase. 811 6

Two cDNA clones, cATMPK1 and cATMPK2, encoding MAP kinases (mitogen-activated protein kinases) have been cloned from Arabidopsis thaliana and their nucleotide sequences have been determined. Putative proteins encoded by ATMPK1 and ATMPK2 genes, designated ATMPK1 and ATMPK2, contain 370 and 376 amino acid residues, respectively, and are 88.7% identical at the amino acid sequence level. ATMPK1 and ATMPK2 exhibit significant similarity to rat ERK2 (49%) and Xenopus MAP kinase (50%). The amino acid residues corresponding to the sites of phosphorylation (Thr-Glu-Tyr) that are involved in the activation of MAP kinases are conserved in ATMPK1 and ATMPK2. Northern blot analysis indicates that the ATMPK1 and ATMPK2 mRNAs are significantly present in all the organs except seeds. Genomic Southern blot analysis suggests that there are a few additional genes that are related to ATMPK1 and ATMPK2 in the Arabidopsis genome. Purified Xenopus MAP kinase kinase (MAPK kinase) phosphorylates ATMPK1 and ATMPK2 proteins that have been expressed in Escherichia coli, activating these enzymes. A rapid and transient activation of 46-kDa protein kinase activity that phosphorylated myelin basic protein (MBP) was detected when auxin-starved tobacco BY-2 cells were treated with synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D). Protein kinase activities which phosphorylated the recombinant ATMPK2 protein also increased rapidly after auxin treatment in the auxin-starved BY-2 cells. These results suggest that auxin may function as an activator of plant MAP kinase homologues, as do various mitogens in animal systems.
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PMID:Characterization of two cDNAs that encode MAP kinase homologues in Arabidopsis thaliana and analysis of the possible role of auxin in activating such kinase activities in cultured cells. 813 Jul 95

Skeletal muscle is a major target of insulin action. The possible role of MAP kinase activation in insulin receptor signaling in muscle was examined. After a 48-hr fast, rats were injected intravenously with insulin or saline, muscles were excised after 3-20 min, homogenized, and MAP kinases were partially purified by ammonium sulfate precipitation and Mono Q chromatography. Activity was assayed as 32P-incorporation into myelin basic protein. Two activity peaks were identified; peak I eluted with approximately 0.1 M NaCl and peak II with approximately 0.2 M NaCl. Three min after insulin injection the activity of peak II increased > 2-fold, peak I was unchanged. After 10 min, the activity of peak II returned toward baseline, while peak I was activated approximately 3-fold. Immunoblots confirmed the presence of MAP kinases eluting with activity peaks I and II; the former as a approximately 41 kDa protein and the latter as a doublet of approximately 42 and approximately 44 kDa. The data suggest sequential activation of two MAP kinases in muscles; the isoform which activates/deactivates rapidly may represent ERK-1, while the more slowly responding isoform may be ERK-2.
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PMID:Sequential activation of two mitogen activated protein (MAP) kinase isoforms in rat skeletal muscle following insulin injection. 826 93

Lysophosphatidic acid (LPA) added to serum-starved Swiss 3T3 cells induced, in a time- and concentration-dependent manner, tyrosine phosphorylation of multiple proteins, including proteins of 43, 64, 88 kDa and a group of proteins between 110 and 130 kDa. Among them, two proteins, p43 and p120, were identified as mitogen-activated protein kinase (MAP-kinase) and focal adhesion kinase (FAK), respectively, by immunoprecipitation and immunoblot analysis. Tyrosine phosphorylation of p64 peaked at 1 min and declined rapidly, whereas that of MAP-kinase and FAK peaked at 5 and 10 min after the addition of LPA, respectively. The activity of MAP-kinase determined as phosphorylation of myelin basic protein increased transiently about 3-fold at 5 min, and correlated with tyrosine phosphorylation. These results indicate that tyrosine phosphorylation of these proteins is a part of the signal transduction by LPA and may be involved in its mitogenic responses.
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PMID:Lysophosphatidic acid induces tyrosine phosphorylation and activation of MAP-kinase and focal adhesion kinase in cultured Swiss 3T3 cells. 836 68

Microinjection of transforming p21ras into Xenopus oocytes caused a time-dependent increase in the level of total cell protein phosphorylation that culminated with germinal vesicle breakdown (GVBD). The same pattern of phosphorylation was observed in oocytes matured by either progesterone or insulin. Treatment with cycloheximide (CHX) completely blocked both GVBD and the associated de novo phosphorylations induced by the hormones, but did not abolish p21ras-induced maturation nor the occurrence of associated maturation promoting factor (MPF)-dependent and -independent phosphorylations. Thus, induction of GVBD by p21ras in the absence of protein synthesis correlated with the activation of cytosolic MPF-associated kinase activity similar in specificity on exogenous (histone H1) and endogenous (47 kDa and a 42 kDa proteins) substrates to the MPF activity of hormonally-matured oocytes. The injection of p21ras in the presence of CHX caused also activation of other kinase(s) proceeding MPF activation which were responsible for the phosphorylation of endogenous substrates including a 41 kDa protein and a 92 kDa protein kinase that comigrated, respectively, with bands recognized specifically by antibodies to MAP2 kinase and S6 kinase. The phosphorylation of those bands correlated also with the activation of cytosolic kinases acting specifically on myelin basic protein (MBP) and a S6-derived peptide as substrates. These results indicate that, in the absence of protein synthesis, p21ras is able to activate phosphorylation events leading to GVBD and suggest that this oncoprotein can participate in at least two separate pathways of MPF activation. We propose that the activation of MAP/MBP kinases and S6 kinases is an early effect of p21ras oncoproteins.
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PMID:p21ras-induced meiotic maturation of Xenopus oocytes in the absence of protein synthesis: MPF activation is preceded by activation of MAP and S6 kinases. 838 Dec 22

In numerous cases of signal transduction, the mitogen-activated protein kinases (MAP kinases) or extracellular regulated kinases (ERKs) are found to be activated by phosphorylations which result in electrophoretic mobility changes. Activities of MAP kinases in cytosolic extracts can also be monitored by the capacity of such extracts to phosphorylate myelin basic protein. These two assays were used to demonstrate that MAP kinases were rapidly activated during heat shock of both quiescent and exponentially growing mammalian (hamster, rat, mouse and human) cells. Thus, the MAP kinase cascade is likely to also ensure heat-shock signal transduction and contribute to the regulation of the complex array of metabolic changes designated as the heat-shock response.
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PMID:MAP kinase activation during heat shock in quiescent and exponentially growing mammalian cells. 838 21


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