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

In dog thyroid epithelial cells (thyrocytes) in primary culture, thyrotropin (TSH) acting through cAMP induces proliferation and differentiation expression, whereas epidermal growth factor (EGF) and tumor-promoting phorbol esters induce proliferation and dedifferentiation. In these cells we have demonstrated mitogen-activated protein (MAP) kinase phosphorylation by 32P labeling and two-dimensional gel electrophoresis and by immunodetection with anti-MAP kinase and anti-phosphotyrosine antibodies after one- or two-dimensional gel electrophoresis. MAP kinase localization was demonstrated by immunochemical staining. We show the following results. (i) As in other systems, EGF and phorbol esters induced p42 and p44 MAP kinases phosphorylation on tyrosine, serine, and threonine. This effect was rapid, peaking after 5 and 15 min, respectively, followed by a slow decline thereafter. It preceded a translocation of MAP kinase immunoreactivity from cytoplasm to nucleus. (ii) Carbamylcholine, a potent stimulator of the Ca(2+)-phosphatidylinositol cascade which is unable to induce DNA synthesis, stimulated MAP kinases phosphorylation and nuclear staining with kinetics similar to those observed after EGF action, indicating that MAP kinase phosphorylation was not sufficient for mitogenesis. (iii) The cAMP-dependent mitogenic cascade elicited by TSH and forskolin did not involve the phosphorylation and nuclear translocation of p42 and p44 MAP kinases at any time during the entire prereplicative phase. Activation of MAP kinases by phosphorylation is therefore not a necessary step in the G0-G1 transition in this mitogenic cascade.
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PMID:Phosphorylation of mitogen-activated protein kinases is involved in the epidermal growth factor and phorbol ester, but not in the thyrotropin/cAMP, thyroid mitogenic pathway. 838 60

The Elk-1 and SRF transcription factors form a ternary complex at the c-fos serum response element (SRE). Growth factor stimulation rapidly induces a reversible change in the electrophoretic mobility of the ternary complex, accompanied by increased phosphorylation of the Elk-1 C-terminal region and by the activation of a 42 kd cellular Elk-1 kinase. Phosphorylation of Elk-1 in vitro by partially purified p42/p44 MAP kinase induces a similar reduction in ternary complex mobility but has little effect on the efficiency of its formation. In vitro, MAP kinase phosphorylates the Elk-1 C-terminal region at multiple sites, which are also phosphorylated following growth factor stimulation in vivo. The Elk-1 C-terminal region functions as a regulated transcriptional activation domain whose activity in vivo is dependent on the integrity of the MAP kinase sites. These findings directly link transcriptional activation by the SRE to the growth factor-regulated phosphorylation of an SRE-binding protein.
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PMID:The SRF accessory protein Elk-1 contains a growth factor-regulated transcriptional activation domain. 838 92

IL-6 is a multi-functional cytokine that utilizes 80-kDa ligand-binding and 130-kDa signal-transducing subunits to stimulate diverse cellular responses. Although IL-6R ligation has been associated with tyrosine protein phosphorylation and activation of an unidentified serine/threonine kinase, very little is known about the intermediary signaling events between the cell membrane and the nucleus. rIL-6 treatment of the human B cell line, AF-10, induced MAP kinase (mitogen-activated protein kinase) activity as determined by in vitro phosphorylation of microtubule-associated protein-2 (MAP-2) and the synthetic peptide APRTPGGRR, corresponding to amino acids 95-98 of bovine myelin basic protein. The kinetics of the response was rapid and dependent on the dose of rIL-6. The response was cytokine specific, did not require the presence of extracellular Ca2+, and was minimally affected by the presence of staurosporine. MAP kinase activation in AF-10 cells occurred in parallel with appearance of 42- and 44-kDa tyrosine phosphoproteins (p42 and p44). Moreover, MAP kinase activation was diminished when AF-10 cells were stimulated with rIL-6 in the presence of tyrosine protein kinase inhibitors, genistein and geldanomycin. p42 and p44 co-electrophoresed on SDS-PAGE with extracellular signal-related kinase (ERK)-2, and ERK-1, respectively; both are members of the ERK family. In addition to p42MAPK and p44MAPK, rIL-6 also activated a MAP-2 kinase that eluted at a lower salt concentration (20 to 60 mM NaCl, peak I) from Mono-Q resin than p42MAPK (120 to 180 mM NaCl, peak II). The identify of this kinase is unknown but it is not an MPB kinase or a protein that exhibits immunoreactivity with anti-ERK antisera. In another IL-6-responsive B cell line, SKW6.4, rIL-6-activated peak I MAP-2 kinase but failed to activate ERK-2. The protein kinase C agonist, PMA, did, however, activate ERK-2 in SKW6.4 cells. These results show that the pleiotrophic cytokine, IL-6, activates p42MAPK/ERK-2 and at least one other serine/threonine kinase in B cell lines.
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PMID:Recombinant IL-6 activates p42 and p44 mitogen-activated protein kinases in the IL-6 responsive B cell line, AF-10. 838 18

The induction of T-cell growth by the T-cell antigen receptor (TcR) is dependent on a co-ordinated process of phosphorylation and dephosphorylation of intracellular proteins. An intermediary in this signalling pathway is the serine kinase, p42 mitogen-activated protein kinase (p42MAPK), also known as microtubule-associated protein-2 kinase (MAP-2K). MAP-kinase is activated upon the acquisition of tyrosine as well as threonine phosphate groups and removal of either by specific tyrosine or serine/threonine phosphatases abrogates kinase activity. Okadaic acid (OA), a tumour promoter and potent inhibitor of type 1 and 2A serine/threonine protein phosphatases (PP1 and PP2A), induced MAP-kinase activity in Jurkat T cells in a dose-dependent fashion with optimal effect at 1 microM. Compared to rapid activation (peak < 10 min) of MAP-kinase by another tumour promoter, the phorbol ester, PMA, the effect of OA was delayed (> 30 min) and more sustained. In spite of activating a growth-promoting kinase, OA differed from PMA by its lack of mitogenic activity and failure to induce CD25 [interleukin-2R alpha (IL-2R alpha)] expression in normal human T cells. This implies that PP1 and PP2A also act downstream of MAP-kinase to facilitate later cell cycle events. PMA induced a 42,000 MW tyrosine phosphoprotein which co-electrophoresed and co-chromatographed with ERK-2, a p42 MAP-kinase. Although OA induced an identical Mono-Q peak, there was less avid tyrosine phosphorylation of p42. OA also differed from PMA to the extent by which it induced mobility shift of the tyrosine protein kinase, p56lck, which has been implicated in p42MAPK activation in T cells. Taken together, these results indicate that OA and PMA exert both overlapping as well as divergent effects on lymphocyte growth pathways.
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PMID:Contrasting effects of two tumour promoters, phorbol myristate acetate and okadaic acid, on T-cell responses and activation of p42 MAP-kinase/ERK-2. 838 30

Mitogen-activated protein (MAP) kinases comprise an evolutionarily conserved family of proteins that includes at least three vertebrate protein kinases (p42, p44, and p55 MAPK) and five yeast protein kinases (SPK1, MPK1, HOG1, FUS3, and KSS1). Members of this family are activated by a variety of extracellular agents that influence cellular proliferation and differentiation. In Saccharomyces cerevisiae, there are multiple physiologically distinct MAP kinase activation pathways composed of structurally related kinases. The recently cloned vertebrate MAP kinase activators are structurally related to MAP kinase activators in these yeast pathways. These similarities suggest that homologous kinase cascades are utilized for signal transduction in many, if not all, eukaryotes. We have identified additional members of the MAP kinase activator family in Xenopus laevis by a polymerase chain reaction-based analysis of embryonic cDNAs. One of the clones identified (XMEK2) encodes a unique predicted protein kinase that is similar to the previously reported activator (MAPKK) in X. laevis. XMEK2, a highly expressed maternal mRNA, is developmentally regulated during embryogenesis and expressed in brain and muscle. Expression of XMEK2 in yeast cells suppressed the growth defect associated with loss of the yeast MAP kinase activator homologs, MKK1 and MKK2. Partial sequence of a second cDNA clone (XMEK3) identified yet another potential MAP kinase activator. The pattern of expression of XMEK3 is distinct from that of p42 MAPK and XMEK2. The high degree of amino acid sequence similarity of XMEK2, XMEK3, and MAPKK suggests that these three are related members of an amphibian family of protein kinases involved in the activation of MAP kinase. Discovery of this family suggests that multiple MAP kinase activation pathways similar to those in yeast cells exist in vertebrates.
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PMID:Novel members of the mitogen-activated protein kinase activator family in Xenopus laevis. 839 11

Engagement of the B-cell antigen receptor complex induces immediate activation of receptor-associated Src family tyrosine kinases including p55blk, p59fyn, p53/56lyn, and perhaps p56lck, and this response is accompanied by tyrosine phosphorylation of distinct cellular substrates. These kinases act directly or indirectly to phosphorylate and/or activate effector proteins including p42 (microtubule-associated protein kinase) (MAPK), phospholipases C-gamma 1 (PLC gamma 1) and C-gamma 2 (PLC gamma 2), phosphatidylinositol 3-kinase (PI 3-K), and p21ras-GTPase-activating protein (GAP). Although coimmunoprecipitation results indicate that the Src family protein tyrosine kinases interact physically with some of these effector molecules, the molecular basis of this interaction has not been established. Here, we show that three distinct sites mediate the interaction of these kinases with effectors. The amino-terminal 27 residues of the unique domain of p56lyn mediate association with PLC gamma 2, MAPK, and GAP. Binding to PI 3-K is mediated through the Src homology 3 (SH3) domains of the Src family kinases. Relatively small proportions of cellular PI 3-K, PLC gamma 2, MAPK, and GAP, presumably those which are tyrosine phosphorylated, bind to the SH2 domains of these kinases. Comparative analysis of binding activities of Blk, Lyn, and Fyn shows that these kinases differ in their abilities to associate with MAPK and PI 3-K, suggesting that they may preferentially bind and subsequently phosphorylate distinct sets of downstream effector molecules in vivo. Fast protein liquid chromatography Mono Q column-fractionated MAPK maintains the ability to bind bacterially expressed Lyn, suggesting that the two kinases may interact directly.
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PMID:Mapping of sites on the Src family protein tyrosine kinases p55blk, p59fyn, and p56lyn which interact with the effector molecules phospholipase C-gamma 2, microtubule-associated protein kinase, GTPase-activating protein, and phosphatidylinositol 3-kinase. 839 16

Chronic myelogenous leukemia (CML) is characterized by a specific chromosomal translocation occurring between the long arms of chromosomes 9 and 22 resulting in a fusion product, p210 BCR/ABL, which has elevated tyrosine kinase activity. Expression of p210 BCR/ABL in murine interleukin-3 (IL-3)--dependent cell lines typically converts these cell lines to factor-independence by a non-autocrine mechanism. The IL-3 receptor is believed to function in part by activating a receptor-associated tyrosine kinase, leading to the hypothesis that p210 BCR/ABL may induce factor-independence of myeloid cells by constitutively phosphorylating some common signal-transducing proteins that normally would be phosphorylated on tyrosine residues in response to IL-3. p210 BCR/ABL subclones were constructed from an IL-3-dependent murine myeloid cell line, 32Dcl3, by transfection of a plasmid containing a full-length p210 BCR/ABL cDNA. Following transfection, the cells became completely factor-independent within 3 weeks. We examined the effects of p210 BCR/ABL and IL-3 on the pattern of tyrosine phosphorylation of cellular proteins in 32Dcl3 cells using one- and two-dimensional antiphosphotyrosine immunoblotting. WEHI-3B conditioned media (WEHI-CM) was used as a source of IL-3. The introduction of p210 BCR/ABL results in constitutively increased levels of tyrosine phosphorylation of more than 20 new proteins, while WEHI-CM induced transient tyrosine phosphorylation of 6 to 10 new proteins. Using two-dimensional immunoblots to examine phosphoproteins, four categories could be identified: (1) proteins that are inducibly tyrosine phosphorylated in response to WEHI-CM in 32Dcl3 cells only, (2) proteins inducibly tyrosine phosphorylated by WEHI-CM only in p210 BCR/ABL+ cells, (3) proteins that are inducibly tyrosine phosphorylated in response to WEHI-CM in both 32Dcl3 cells and p210 BCR/ABL+ cells, and (4) proteins inducibly tyrosine phosphorylated in response to WEHI-CM and constitutively phosphorylated in the presence of p210 BCR/ABL. We have identified one of the proteins in category 4 as p42 mitogen-activated protein (MAP) kinase (ERK2). Overall, however, we found that the signal transduction pathways of IL-3 and BCR/ABL are strikingly different, suggesting that most of the immediate substrates of the IL-3 receptor-activated tyrosine kinase and p210 BCR/ABL kinase are different. Convergence of signaling pathways at p42 MAP kinase is of interest since activation of this kinase has been linked to mitogenesis in many systems. Identification of the overlapping proteins of both IL-3 signal transduction in 32Dcl3 cells and p210 BCR/ABL+ cells may help explain the growth-promoting effects of this oncogene.
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PMID:Interleukin-3 and p210 BCR/ABL activate both unique and overlapping pathways of signal transduction in a factor-dependent myeloid cell line. 840 19

We report a strategy for regulating the activity of a cytoplasmic signaling molecule, the protein kinase encoded by raf-1. Retroviruses encoding a gene fusion between an oncogenic form of human p74raf-1 and the hormone-binding domain of the human estrogen receptor (hrafER) were constructed. The fusion protein was nontransforming in the absence of estradiol but could be reversibly activated by the addition or removal of estradiol from the growth media. Activation of hrafER was accompanied in C7 3T3 cells by the rapid, protein synthesis-independent activation of both mitogen-activated protein (MAP) kinase kinase and p42/p44 MAP kinase and by phosphorylation of the resident p74raf-1 protein as demonstrated by decreased electrophoretic mobility. The phosphorylation of p74raf-1 had no effect on the kinase activity of the protein, indicating that mobility shift is an unreliable indicator of p74raf-1 enzymatic activity. Removal of estradiol from the growth media led to a rapid inactivation of the MAP kinase cascade. These results demonstrate that Raf-1 can activate the MAP kinase cascade in vivo, independent of other "upstream" signaling components. Parallel experiments performed with rat1a cells conditionally transformed by hrafER demonstrated activation of MAP kinase kinase in response to estradiol but no subsequent activation of p42/p44 MAP kinases or phosphorylation of p74raf-1. This result suggests that in rat1a cells, p42/p44 MAP kinase activation is not required for Raf-1-mediated oncogenic transformation. Estradiol-dependent activation of p42/p44 MAP kinases and phosphorylation of p74raf-1 was, however, observed in rat1a cells expressing hrafER when the cells were pretreated with okadaic acid. This result suggests that the level of protein phosphatase activity may play a crucial role in the regulation of the MAP kinase cascade. Our results provide the first example of a cytosolic signal transducer being harnessed by fusion to the hormone-binding domain of the estrogen receptor. This conditional system not only will aid the elucidation of the function of Raf-1 but also may be more broadly useful for the construction of conditional forms of other kinases and signaling molecules.
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PMID:Conditional transformation of cells and rapid activation of the mitogen-activated protein kinase cascade by an estradiol-dependent human raf-1 protein kinase. 841 24

Recent studies have demonstrated that administration of an electroconvulsive shock produces a rapid and transient increase in tyrosyl phosphorylation of a approximately 40-kDa protein in rat brain. Initial characterization of this protein's chromatographic properties indicated that it might be a member of a recently identified family of kinases, referred to as mitogen-activated protein (MAP) kinases, that are activated by tyrosyl phosphorylation. In the present study, we have used MAP kinase antisera to assess the identity of this protein. We have found that the approximately 40-kDa phosphotyrosine-containing protein comigrates with p42 MAP kinase (p42mapk) and not with two other 44-kDa MAP kinase family members detected by these antisera. Western blots of proteins immunoprecipitated with MAP kinase antibodies confirm that p42mapk displays increased tyrosyl phosphorylation after an electroconvulsive stimulus. Chromatographic separation of hippocampal extracts indicates that MAP kinase activity elutes in parallel with p42mapk. Accordingly, these studies identify p42mapk as a tyrosyl kinase substrate that is activated by this stimulus and suggest that this form of MAP kinase may be selectively regulated by neuronal stimulation.
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PMID:Identification of p42 mitogen-activated protein kinase as a tyrosine kinase substrate activated by maximal electroconvulsive shock in hippocampus. 841 54

Ligation of the membrane immunoglobulin M receptor as well as stimulation with the protein kinase C agonist phorbol 12-myristate 13-acetate leads to a B-lymphocyte proliferation and differentiation. Both stimuli activate p42 mitogen-activated protein (MAP) kinase in human B-lymphocytes [Casillas, Hanekom, Williams, Katz and Nel (1991) J. Biol. Chem. 266, 19088-19094]. MAP kinase activation is dependent on tyrosine as well as threonine phosphorylation of the kinase and its activity is inhibited by tyrosine as well as threonine/serine phosphatases. Okadaic acid, a specific inhibitor of type 1 and 2A serine/threonine phosphatases, induced MAP kinase activity in a potent and dose-dependent fashion, but failed to induce [3H]thymidine incorporation into normal human tonsil B-cells. Moreover, in combination with membrane immunoglobulin M ligation, okadaic acid decreased rather than increased [3H]thymidine incorporation. The kinetics of MAP kinase activation by okadaic acid differed from phorbol 12-myristate 13-acetate and anti-membrane immunoglobulin M stimulation. Okadaic acid induced tyrosine phosphorylation of 42 kDa and 44 kDa proteins which co-electrophoresed and co-chromatographed with ERK-2 and ERK-1 respectively. Ramos cells also contained a constitutively active 46 kDa MAP kinase which appeared as a separate peak in chromatography and could be immunoprecipitated by an antiserum against a rat ERK-1 fusion protein.
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PMID:Okadaic acid activates p42 mitogen-activated protein kinase (MAP kinase; ERK-2) in B-lymphocytes but inhibits rather than augments cellular proliferation: contrast with phorbol 12-myristate 13-acetate. 845 45


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