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

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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)

The tyrosine phosphorylation of microtubule-associated protein (MAP) kinase was examined in the gerbil brain after transient ischemia and reperfusion. Phosphorylation of MAP kinase was maximal within 1 min of reperfusion following 5 min of ischemia and returned to control levels as early as 5 min postischemia. The greatest increase in MAP kinase phosphorylation was detected in the hippocampus, with minor increases in other ischemic regions of the brain. Several tyrosine-phosphorylated proteins were detected in the gerbil hippocampus; however, the ischemia and reperfusion injury only increased tyrosine phosphorylation of MAP kinase. The increase in tyrosine phosphorylation was prevented by the N-methyl-D-aspartate (NMDA) receptor blocker (+)-MK-801, whereas a non-NMDA receptor blocker, 6-cyano-7-nitroquinoxaline-2,3-dione, was ineffective. Pretreatment of gerbils with calcium channel blockers also prevented the tyrosine phosphorylation of MAP kinase in the ischemic brain. Altogether, these results imply an involvement of glutamate receptors and calcium during the tyrosine phosphorylation of MAP kinase. Tyrosine phosphorylation was also prevented when ischemia and reperfusion were conducted under hypothermic conditions, which protect against neurodegenerative damage. These findings implicate a role for MAP kinase in neuronal damage resulting from ischemia and reperfusion.
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PMID:Tyrosine phosphorylation of microtubule-associated protein kinase after transient ischemia in the gerbil brain. 132 34

The N-methyl-D-aspartate (NMDA) receptor, a subtype of glutamate receptors, plays a key role in synaptic plasticity in the nervous system. After NMDA receptor activation, calcium entry into the postsynaptic neuron is a critical initial event. However, the subsequent mechanisms by which the NMDA receptor signal is processed are incompletely understood. Stimulation of cultured rat hippocampal cells with glutamate resulted in the rapid and transient tyrosine phosphorylation of a 39-kilodalton protein (p39). Tyrosine phosphorylation of p39 was triggered by the NMDA receptor and required an influx of Ca2+ from the extracellular medium. Because p39 was found to be highly related or identical to the microtubule-associated protein 2 kinase, the NMDA receptor signal may be processed by a sequential activation of protein kinases.
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PMID:Stimulation of protein tyrosine phosphorylation by NMDA receptor activation. 171 95

Mitogen-activated protein kinase (MAP kinase) is a serine/threonine protein kinase that becomes enzymatically activated and phosphorylated on tyrosine and threonine following treatment of quiescent cells with a variety of stimulatory agonists. Phosphorylation on both tyrosine and threonine is necessary to maintain full activity, and these two regulatory phosphorylations occur close to each other, separated by a single glutamate. To study the mechanisms by which MAP kinase becomes phosphorylated and activated, we have cloned a full-length cDNA encoding MAP kinase and have expressed the enzyme in Escherichia coli as a soluble nonfusion protein. We find that the enzyme displays a basal, intramolecular autophosphorylation on tyrosine-185 that is accompanied by activation of the enzyme's kinase activity towards an exogenous substrate. The tyrosine-phosphorylated protein displays a small fraction of the activity seen with the fully activated, doubly phosphorylated enzyme isolated from mammalian cells but is activated 10- to 20-fold relative to the unphosphorylated enzyme. These findings raise the possibility that regulation of MAP kinase activity in response to agonist stimulation could occur in part through the enhancement of autophosphorylation on tyrosine.
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PMID:Autophosphorylation in vitro of recombinant 42-kilodalton mitogen-activated protein kinase on tyrosine. 183 84

The Lck tyrosine kinase molecule plays an essential role in T cell activation and T cell development. Using the expression cloning technique, we have isolated a gene that encodes a molecule, LckBP1, able to associate with murine Lck. Analysis of full-length LckBP1 cDNA indicates at least four potentially important segments: a four tandem 37 amino acid repeat motif with a potential helix-turn-helix DNA binding motif; a proline-rich region; a proline-glutamate repeat; and an SH3 domain. These four regions are very similar to the human haematopoietic-specific protein 1 (HS1). Deletion mutant analysis of LckBP1 revealed two proline-rich regions that permit association with Lck SH3. One region contains prolines conserved among HS1 and cortactin, and the other region contains a potential MAP kinase recognition site. In vivo association between Lck and LckBP1 was confirmed by immunoprecipitation of lysates from a pre-T cell line and adult thymocytes using antibodies specific for Lck and LckBP1. LckBP1 is tyrosine phosphorylated after T-cell receptor stimulation. The SH3 domain and the potential helix-turn-helix motif in LckBP1 suggest that this molecule may associate with various molecules and function as a DNA binding molecule. The data also suggest that LckBP1 mediates intracellular signalling through Lck in T cells.
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PMID:LckBP1, a proline-rich protein expressed in haematopoietic lineage cells, directly associates with the SH3 domain of protein tyrosine kinase p56lck. 762 41

Mitogen-activated protein kinase (MAP kinase) was activated by stimulation of glutamate receptors in cultured rat hippocampal neurons. Ten micromolar glutamate maximally stimulated MAP kinase activity, which peaked during 10 min and decreased to the basal level within 30 min. Experiments using glutamate receptor agonists and antagonists revealed that glutamate stimulated MAP kinase through NMDA and metabotropic glutamate receptors but not through non-NMDA receptors. Glutamate and its receptor agonists had no apparent effect on MAP kinase activation in cultured cortical astrocytes. Addition of calphostin C, a protein kinase C (PKC) inhibitor, or down-regulation of PKC activity partly abolished the stimulatory effect by glutamate, but the MAP kinase activation by treatment with ionomycin, a Ca2+ ionophore, remained intact. Lavendustin A, a tryrosine kinase inhibitor, was without effect. In experiments with 32P-labeled hippocampal neurons, MAP kinase activation by glutamate was associated with phosphorylation of the tyrosine residue located on MAP kinase. However, phosphorylation of Raf-1, the c-raf protooncogene product, was not stimulated by treatment with glutamate. Our observations suggest that MAP kinase activation through glutamate receptors in hippocampal neurons is mediated by both the PKC-dependent and the Ca(2+)-dependent pathways and that the activation of Raf-1 is not involved.
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PMID:Activation of mitogen-activated protein kinase in cultured rat hippocampal neurons by stimulation of glutamate receptors. 764 5

Epidermal growth factor (EGF) functions in a bimodal capacity in the nervous system, acting as a mitogen in neuronal stem cells and a neurotrophic factor in differentiated adult neurons. Thus, it is likely that EGF signal transduction, as well as receptor expression, differs among various cell types and possibly in the same cell type at different stages of development. We used hippocampal neuronal cell lines capable of terminal differentiation to investigate changes in EGF receptor expression, DNA synthesis, and stimulation of mitogen-activated protein (MAP) kinase by EGF before and after differentiation. H19-7, the line that was most representative of hippocampal neurons, was mitogenically responsive to EGF only before differentiation and increased in EGF binding after differentiation. MAP kinase was stimulated by EGF in both undifferentiated and differentiated cells, as well as in primary hippocampal cultures treated with either EGF or glutamate. These results indicate that the activation of MAP kinase by EGF is an early signaling event in both mitotic and postmitotic neuronal cells. Furthermore, these studies demonstrate the usefulness of hippocampal cell lines as a homogeneous neuronal system for studies of EGF signaling or other receptor signaling mechanisms in the brain.
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PMID:Activation of mitogen-activated protein kinase by epidermal growth factor in hippocampal neurons and neuronal cell lines. 769 Aug 47

Recent studies have identified at least two homologous mitogen-activated protein (MAP) kinases that are activated by phosphorylation of both tyrosine and threonine residues by an activator kinase. To help define the role of these MAP kinases in neuronal signalling, we have used primary cultures derived from fetal rat cortex to assess the regulation of their activity by agonist stimulation of glutamate receptors and by synaptic activity. Regulation was assayed by monitoring changes in both tyrosine phosphorylation on western blots and in vitro kinase activity toward a selective MAP kinase substrate peptide. In initial studies, we found that phorbol ester treatment increased tyrosine phosphorylation of p42 MAP kinase and stimulated MAP kinase activity. A similar response was elicited by three agonists of metabotropic glutamate receptors, i.e., trans-(+/-)-1-amino-1,3-cyclopentane dicarboxylic acid, quisqualate, and (2S,3S,4S)-alpha-(carboxycyclopropyl)glycine. MAP kinase activity and p42 MAP kinase tyrosine phosphorylation were also stimulated by the ionotropic glutamate receptor agonist, kainate, but not by N-methyl-D-aspartate. To examine regulation of MAP kinase by synaptic activity, cultures were treated with picrotoxin, an inhibitor of GABAA receptor-mediated inhibition that enhances spontaneous excitatory synaptic activity. Treatment of cultures with picrotoxin elicited activation of MAP kinase. This response was blocked by tetrodotoxin, which suppresses synaptic activity. These results demonstrate that p42 MAP kinase is activated by glutamate receptor agonist stimulation and by endogenous synaptic activity.
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PMID:Activation of p42 mitogen-activated protein kinase by glutamate receptor stimulation in rat primary cortical cultures. 769 64

Mitogen-activated protein kinase kinase (MAPKK) is a dual specificity protein kinase that exhibits a high degree of specificity toward its downstream target, mitogen-activated protein kinase (MAPK). In this study, we used stable overexpression of MAPKK and its mutants in NIH 3T3 cells to study effects on downstream components of the MAPK signaling cascade and to correlate them to physiological responses. We have mutated the potential regulatory serine residue 222 to alanine (S222A) or to glutamate (S222E) and serines 212 and 218 together to alanine residues (S212A,S218A). Lysine 97 was mutated to alanine (K97A) to provide an inactive enzyme. Overexpression of the wild type MAPKK had no effect on any of the parameters examined. The K97A and S222A mutants served as dominant negatives by suppressing MAPKK, MAPK, and p90rsk activation in vivo. S222E enhanced all of these activities, and S212A,S218A had a small inhibitory effect. A similar trend was observed when cellular proliferation was examined and the different effects were accompanied by altered cellular shape. Taken together, our results demonstrate a direct linkage between the MAPK signaling pathway and the control of cellular proliferation and morphology and also establish that phosphorylation of serine 222 is essential for MAPKK activation together with the phosphorylation of an additional serine(s) (probably serine 218).
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PMID:Overexpression of mitogen-activated protein kinase kinase (MAPKK) and its mutants in NIH 3T3 cells. Evidence that MAPKK involvement in cellular proliferation is regulated by phosphorylation of serine residues in its kinase subdomains VII and VIII. 792 75

A variety of extracellular signals lead to the phosphorylation and activation of mitogen-activated protein kinases (MAP kinases). An activator of MAP kinases, Mek1, phosphorylates MAP kinases at threonine and tyrosine residues and is itself phosphorylated at serine-218 and -222 by the protooncogene product Raf-1. By introducing negatively charged residues that may mimic the effect of phosphorylation at positions 218 and 222, we have activated the capacity of Mek1 to phosphorylate MAP kinase by > 100-fold. The most effective activation by a single substitution resulted from the introduction of aspartate at position 218, whereas the introduction of either aspartate or glutamate at position 222 was ineffective. Expression of the activated Mek1 phosphorylation-site mutants in COS-7 cells led to the activation of MAP kinase in the cells and resulted in an increase in the mass of the transfected COS-7 cell population, suggesting an important role of Mek1 in the transduction of mitogenic signals.
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PMID:Constitutive activation of Mek1 by mutation of serine phosphorylation sites. 809 Jul 53

Extracellular signal-regulated protein kinases (ERK) 1 and 2 and mutants of each were expressed in bacteria with a hexahistidine tag and purified using nickel-chelate chromatography. Basal activity of wild type ERK2 was approximately 2 nmol/min/mg. Self-catalyzed phosphorylation occurred in vitro on the major physiological site of tyrosine phosphorylation in an intramolecular reaction. Rabbit muscle ERK activator activated ERK2 500-1000-fold up to a specific activity (approximately 2 mumol/min/mg) approximating that of ERK1 purified from stimulated cells (Boulton, T.G., Gregory, J.S., and Cobb, M.H. (1991) Biochemistry 30, 278-286). ERK1 could also be activated by the ERK activator to the same extent. Mutants lacking the major site of tyrosine phosphorylation were autophosphorylated at a greatly reduced rate and were no longer highly activated by the ERK kinase. Mutants lacking the major site of threonine phosphorylation were autophosphorylated at the same or an enhanced rate, but the kinase activity of these mutants depended on the residue used to replace the threonine. Replacement by glutamate rendered the kinase capable of being activated by ERK activator, while replacement by alanine did not. Thus, the carboxyl group of glutamate can provide at least some of the features introduced by phosphothreonine in activated ERKs.
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PMID:Regulation and properties of extracellular signal-regulated protein kinases 1 and 2 in vitro. 844 86


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