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)

We have previously described the purification of a myelin basis protein (MBP) kinase from maturing sea star oocytes (Sanghera, J. S., Paddon, H. B., Bader, S. A., and Pelech, S. L. (1990) J. Biol. Chem. 265, 52-57). The ability of the purified 44-kDa protein to bind azido-ATP and undergo autophosphorylation on the serine residue implied that it is a protein kinase. Furthermore, partial amino acid sequence data has revealed that it is a novel protein kinase, which we have provisionally designated p44mpk. Autophosphorylation of p44mpk to 0.7 mol of phosphate/mol of enzyme was correlated with a modest (approximately 17%) increase in the MBP-phosphorylating activity of the kinase. Rabbit polyclonal antibody raised against purified p44mpk recognized on immunoblots the protein in highly purified preparations as well as crude oocyte extracts. The affinity-purified anti-p44mpk antibody could immunoprecipitate active kinase, but a subpopulation of the antibody also appeared to be inhibitory. Using this antibody, we have demonstrated that the up to 12-fold stimulation of the cytosolic MBP-phosphorylating activity of this kinase that occurs during sea star oocyte maturation is not due to an increase in the amount of enzyme protein, either from a redistribution within the oocyte or protein synthesis. A slight retardation of the migration of the activated p44mpk on sodium dodecyl sulfate-polyacrylamide gels and its tighter interaction with a MonoQ column is consistent with phosphorylation of the kinase during maturation. p44mpk underwent enhanced phosphorylation when oocytes prelabeled with [32P]orthophosphate were induced to mature with 1-methyladenine. The stimulated MBP-phosphorylating activity of p44mpk in cytosols from maturing oocytes was partly stabilized by the presence of the phosphatase inhibitor beta-glycerol phosphate. Furthermore, treatment of purified p44mpk with protein phosphatase 2A and alkaline phosphatase resulted in 56 and 86% decreases, respectively, in the activity of the kinase. Together, these findings strongly implicate a role for phosphorylation of p44mpk in its activation during sea star oocyte maturation.
 ...
PMID:Role of protein phosphorylation in the maturation-induced activation of a myelin basic protein kinase from sea star oocytes. 201 85

Two intermediary kinases in a protein serine/threonine kinase cascade that is triggered in the response of Swiss 3T3 cells to epidermal growth factor (EGF) have been identified. Several separable EGF-stimulated serine/threonine kinase activities were characterized in the preceding paper (Ahn, N. G., Weiel, J. E., Chan, C. P., and Krebs, E.G. (1990) J. Biol. Chem. 265, 11487-11494). These were preincubated in various combinations in the presence of MgATP with chromatographic fractions from unstimulated cell extracts. Activation of the rate of phosphorylation of a synthetic peptide, Arg-Arg-Leu-Ser-Ser-Leu-Arg-Ala, was observed on preincubation of the breakthrough fraction from unstimulated cell extracts with either of two distinct EGF-stimulated kinase activities, each of which phosphorylated myelin basic protein. Kinetic analysis and fractionation by sizing gel chromatography demonstrated that two myelin basic protein kinase activities (of approximately 30 and approximately 50 kDa) represented the activating components in the mixtures whereas the unstimulated cell extract breakthrough gave rise in each case to the activated Arg-Arg-Leu-Ser-Ser-Leu-Arg-Ala peptide kinase activity of approximately 110 kDa. Inasmuch as the in vitro activation reactions required magnesium plus ATP and were reversed by protein phosphatase treatment, an activation mechanism involving phosphoryl transfer is suggested.
 ...
PMID:Evidence for an epidermal growth factor-stimulated protein kinase cascade in Swiss 3T3 cells. Activation of serine peptide kinase activity by myelin basic protein kinases in vitro. 214 54

Some of the effects of nerve growth factor (NGF) may be mediated by changes in protein phosphorylation. We have identified a protein kinase from PC-12 cells that catalyzes the phosphorylation of pig brain microtubule-associated protein (MAP)-2 in vitro. This activity is stimulated 2-4-fold in extracts from cells treated with NGF or epidermal growth factor (EGF). The partial purification and characterization of this MAP kinase indicate that it is distinct from previously described NGF-stimulated protein kinases. The NGF-stimulated kinase activity is unaffected by direct addition to the assay of the heat-stable cAMP-dependent kinase peptide inhibitor, staurosporine, or K-252A, is slightly stimulated by heparin and is inhibited by sodium fluoride and calcium ions. Treatment of cells with NGF increases the activity of the kinase within 2 min. The activity declines after 10 min, and a second phase of activation is observed at 20-30 min. Comparison of its behavior on gel permeation and sucrose density gradients indicates a molecular mass in the range of 40,000 daltons. The kinase activity is specific for ATP as substrate with a Km of 12 microM. Although the pathway of activation of MAP kinase by NGF is unknown, the stimulation can be reversed by treatment of the enzyme with alkaline phosphatase, suggesting that activation involves phosphorylation of the kinase itself. The properties and hormone sensitivity of the PC-12 MAP kinase suggest that it is similar to the previously identified, growth factor-sensitive MAP kinase from 3T3-L1 adipocytes.
 ...
PMID:Nerve growth factor stimulates a protein kinase in PC-12 cells that phosphorylates microtubule-associated protein-2. 215 37

A protein kinase activity was identified in pig brain that co-purified with microtubules through repeated cycles of temperature-dependent assembly and disassembly. The microtubule-associated protein kinase (MTAK) phosphorylated histone H1; this activity was not stimulated by cyclic nucleotides. Ca2+ plus calmodulin, phospholipids or polyamines. MTAK did not phosphorylate synthetic peptides which are substrates for cyclic AMP-dependent protein kinase, cyclic GMP-dependent protein kinase. Ca2+/calmodulin-dependent protein kinase II, protein kinase C or casein kinase II. MTAK activity was inhibited by trifluoperazine [IC50 (median inhibitory concn.) = 600 microM] in a Ca2+-independent fashion. Ca2+ alone was inhibitory [IC50 = 4 mM). MTAK was not inhibited by heparin, a potent inhibitor of casein kinase II, nor a synthetic peptide inhibitor of cyclic AMP-dependent protein kinase. MTAK demonstrated a broad pH maximum (7.5-8.5) and an apparent Km for ATP of 45 microM. Mg2+ was required for enzyme activity and could not be replaced by Mn2+. MTAK phosphorylated serine and threonine residues on histone H1. MTAK is a unique cofactor-independent protein kinase that binds to microtubule structures.
 ...
PMID:Properties of a microtubule-associated cofactor-independent protein kinase from pig brain. 255 23

A protein kinase, termed microtubule-associated protein (MAP) kinase, which phosphorylates microtubule-associated protein 2 (MAP-2) in vitro and is stimulated 1.5-3-fold in extracts from insulin-treated 3T3-L1 cells has been identified (Ray, L.B., and Sturgill, T.W. (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 1502-1506). Here, we describe chromatographic properties of MAP kinase and provide biochemical characterization of the partially purified enzyme. Isolation of the enzyme is facilitated by its unusually high affinity for hydrophobic interaction chromatography matrices. The molecular weight of the partially purified enzyme was determined to be 35,000 by gel filtration chromatography and 37,000 by glycerol gradient centrifugation. MAP kinase activity of chromatographic fractions correlated precisely with the presence of a 40-kDa phosphoprotein detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. MAP kinase has a Km of 7 microM for ATP and does not utilize GTP. Acetyl-CoA carboxylase, ATP citrate-lyase, casein, histones, phosvitin, protamine, and ribosomal protein S6 were all poor substrates relative to MAP-2. The enzyme is inhibited by fluoride and beta-glycerol phosphate but not by heparin. These properties of MAP kinase distinguish it from protein kinases previously described in the literature.
 ...
PMID:Characterization of insulin-stimulated microtubule-associated protein kinase. Rapid isolation and stabilization of a novel serine/threonine kinase from 3T3-L1 cells. 284 41

Some properties of the protein kinase activity associated with neurofilaments isolated from the brain stem and spinal cord of rats have been investigated. The activity had an apparent Km for ATP of 20 microM, a pH optimum of 8.0 and phosphorylated both serine and threonine residues in neurofilament proteins. Cyclic AMP had no effect on the in vitro reaction and casein was a preferred exogenous substrate in comparison to histone. Phosphopeptide mapping of the 145 kDa subunit from neurofilaments phosphorylated in the presence and absence of microtubule proteins indicated that the neurofilament-associated activity was distinct from the microtubule-associated protein kinase. Limited proteolysis of neurofilaments with chymotrypsin indicated that the enzyme activity was not associated with a domain of the 200 kDa subunit which may form the side-arm projections on neurofilaments.
 ...
PMID:Characteristics of the protein kinase activity associated with rat neurofilament preparations. 668 14

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

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 enzyme glycogen synthase kinase-3 (GSK-3) has been implicated in the control of several metabolic enzymes and transcription factors in response to extracellular signals. In the past, the enzyme has been considered to be a protein Ser/Thr kinase although it was recently reported to contain Tyr(P) (Hughes, K., Nikolakaki, E., Plyte, S. E., Totty, N. F., and Woodgett, J. R. (1993) EMBO J. 12, 803-808). A cDNA encoding rabbit skeletal muscle GSK-3 beta was cloned and expressed in Escherichia coli as an active protein kinase, with apparent M(r) 46,000, capable of phosphorylating several known GSK-3 substrates. Recombinant GSK-3 beta autophosphorylated on Ser, Thr, and Tyr residues although the enzyme already contained Tyr(P) as judged by its recognition by anti-Tyr(P) antibodies. The net result of the autophosphorylation was a 3-5-fold reduction in enzyme activity. GSK-3 alpha, purified from rabbit muscle, also underwent autophosphorylation but only on Ser and Thr residues. In this case, the autophosphorylation stabilized the enzyme activity compared with the control lacking ATP/Mg2+. Of several phosphatases tested, the lambda-phage phosphatase was the most effective in dephosphorylating at Ser and Thr residues but did not dephosphorylate at Tyr residues. The action of the lambda-phosphatase caused a reactivation of GSK-3 beta to approximately 80% of the starting activity. The protein tyrosine phosphatase PTP1B was able to dephosphorylate at Tyr residues leading to a reduction in enzyme activity. A truncated form of GSK-3 beta, apparent M(r) 40,000, had a significantly higher specific activity, was defective in autophosphorylation, and was not inactivated in the autophosphorylation reaction. We conclude that GSK-3 beta is a dual specificity protein kinase in the same sense as the mitogen-activated protein kinase/ERK family of enzymes. Phosphorylation at different residues differentially controls enzyme activity, Ser/Thr phosphorylation causing inactivation and Tyr phosphorylation resulting in increased activity.
 ...
PMID:Glycogen synthase kinase-3 beta is a dual specificity kinase differentially regulated by tyrosine and serine/threonine phosphorylation. 751 73

We have previously shown that a brain protein kinase, termed PK40, catalyzes the multiple phosphorylation of the KSP-repeat site of neurofilaments (NFs) and also can transform tau proteins into the paired helical filament-like state as found in Alzheimer's disease (AD) brains. Protein sequence analysis suggests that PK40 is a form of the extracellular signal-regulated kinase ERK2. A subpopulation of ERK2 species in soluble brain fractions can be efficiently phosphorylated and activated in cell-free systems, simply by adding Mg(2+)-ATP. Two phosphoisoforms of PK40erk2 are formed in this process, which have a reduced gel mobility, very much like the ERK2 form obtained in cell culture by stimulation with growth factors. One of these low-mobility forms cannot be inactivated with protein phosphatase 2A (PP2A) or with tyrosine phosphatases. The second form can be slowly inactivated by PP2A. In this case two Ser/Thr phosphates are removed at different rates during inactivation: One phosphate is very quickly removed to result in the formation of a high-mobility 39-kDa ERK2 species without consequence for activity; the other, slowly removed Ser/Thr phosphate controls the activity but has no effect on the gel mobility of ERK2. These results show that forms of ERK2 exist with properties different from the previously characterized ERK2 (p42mapk) from stimulated cell cultures. The active ERK2 forms produced in the presence of Mg(2+)-ATP alone could provide an explanation for the existence of constitutive ERK2-like NF phosphorylation in vivo. Excessive formation of an ERK2 species resistant to inactivation by PP2A might be relevant to the persistent pathological tau hyperphosphorylation in AD.
 ...
PMID:Phosphatase resistance of ERK2 brain kinase PK40erk2. 753 8


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