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

---

Query: EC:2.7.11.24 (mitogen-activated protein kinase)
95,810 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cross-linking membrane Ig (mIg) on B cells stimulates tyrosine phosphorylation of proteins involved in signal transduction including the mIg-associated proteins Ig-alpha and Ig-beta, the tyrosine kinases p53/p56lyn, p55blk, p59fyn, and PTK72, phosphatidylinositol 3-kinase, phospholipase C gamma 1 and gamma 2, and the mitogen-activated protein kinase. We now show that the p21ras GTPase-activating protein (GAP) is also a substrate for mIg-activated tyrosine kinases. p21ras is a key regulator of cell growth and GAP may act as both a regulator of p21ras activity and as a downstream effector of p21ras. We found that mIg cross-linking caused a rapid increase in tyrosine phosphorylation of GAP in the immature B cell line WEHI-231, the mature B cell lines BAL 17 and Daudi, and the IgG-bearing B cell line A20. In fibroblasts, tyrosine kinase activation causes GAP to associate with two other tyrosine-phosphorylated proteins, p62 and p190, which have homologies to an RNA-binding protein and a transcriptional repressor, respectively. Similarly, mlg cross-linking induced the association of GAP with a 62-kDa tyrosine-phosphorylated protein in BAL 17, WEHI-231, and Daudi cells. Anti-Ig treatment also increased the amount of a 190-kDa tyrosine-phosphorylated protein associated with GAP in WEHI-231 and Daudi cells. After separation by SDS-PAGE and transfer to nitrocellulose, the tyrosine-phosphorylated p62 and p190 present in anti-GAP immunoprecipitates from B cells were capable of binding radiolabeled recombinant GAP, as previously reported for the GAP-associated p62 and p190 from fibroblasts. The amount of p62 that could be detected in this way after immunoprecipitation with antiphosphotyrosine antibodies was much greater from anti-IgM-treated BAL 17 cells than from unstimulated BAL 17 cells. This probably reflects anti-Ig-induced tyrosine phosphorylation of p62. In any case, GAP, p62, and/or p190 may be involved in signal transduction by mIg in B cells.
...
PMID:Targets of B lymphocyte antigen receptor signal transduction include the p21ras GTPase-activating protein (GAP) and two GAP-associated proteins. 841 71

Mitogen-activated protein kinase kinase (MAPKK) is a dual-specificity protein kinase which phosphorylates and activates mitogen-activated protein kinase (MAPK). cDNAs encoding two isoforms of MAPKK, MAPKK1 and MAPKK2 (also known as MEK1 and MEK2), have been cloned in mammalian cells. To analyze the characteristics of MAPKK1 and MAPKK2 individually, we have produced specific anti-MAPKK serum against each isoform. MAPKK1 and MAPKK2 have apparent molecular masses of 45 kDa and 47 kDa, respectively, on SDS/polyacrylamide gel electrophoresis. In mouse tissues, MAPKK1 was highly enriched in brain, while MAPKK2 was present relatively evenly. In rat fibroblastic 3Y1 cells, epidermal growth factor (EGF) treatment induced activation of both MAPKK1 and MAPKK2. Immunoprecipitation experiments have shown that the time courses of activation and deactivation of both isoforms of MAPKK were superimposed. In PC12 cells, both MAPKK1 and MAPKK2 were activated in response to nerve growth factor (NGF) as well as EGF, and the time courses of activation and deactivation of both isoforms were indistinguishable from each other in the NGF-stimulated cells and also in the EGF-stimulated cells. Furthermore, localization of both MAPKK1 and MAPKK2 in the cytoplasm was unchanged in response to EGF and NGF. Thus, the same or quite similar mechanisms may operate in the regulation of the activation and deactivation of two isoforms of MAPKK, and both kinases might have redundant functions when expressed in the same cell.
...
PMID:Activation of two isoforms of mitogen-activated protein kinase kinase in response to epidermal growth factor and nerve growth factor. 852 59

Interleukin-2 (IL-2) induces DNA binding of STAT5, a member of the family of cytokine-regulated transcription factors termed 'signal transducers and activators of transcription'. IL-2-stimulated STAT5-DNA complexes include two tyrosine phosphoproteins which exhibit distinct mobilities in SDS-PAGE gels. Our studies have shown that IL-2 rapidly induces both tyrosine phosphorylation and serine phosphorylation of STAT5 and that the two STAT5 tyrosine phosphoproteins detected in IL-2-activated cells differ in their levels of phosphorylation on serine residues. The two different phosphoforms of STAT5 have identical in vitro DNA binding specificity and reactivity with tyrosine phosphopeptides, but differ in their cellular localization. As well, the present data indicate that the transcriptional activity of STAT5 is regulated by serine kinases in T lymphocytes. Two previously characterized serine kinases activated by IL-2, MAP kinase/ERK2 and p70 S6 kinase, do not appear to be involved in STAT5 regulation by this cytokine. Accordingly, STAT5 activation in T cells requires the convergent action of tyrosine kinases and a distinct serine/threonine kinase which has not previously been implicated in IL-2 signalling.
...
PMID:Interleukin-2 activation of STAT5 requires the convergent action of tyrosine kinases and a serine/threonine kinase pathway distinct from the Raf1/ERK2 MAP kinase pathway. 861 37

Treatment of human platelets with phorbol 12-myristate 13-acetate (PMA) and arginine vasopressin (AVP) increase the phosphorylation and activation of mitogen-activated protein kinase (MAPK). Electrophoretic retardation of MAPK mobility on SDS-polyacrylamide gels was used for determination of MAPK phosphorylation. The activity of MAPK was tested in myelin basic protein (MBP)-containing polyacrylamide gels. In this study we compared the PMA and AVP signal transduction pathways leading to the activation of MAPKs and Na+/H+ exchanger (NHE). Both agonists stimulate MAPK and NHE activities in a similar time frame and concentration dependence. The MAPK and NHE activities induced by PMA were inhibited by staurosporine, a potent inhibitor for protein kinase C (PKC), and by MAPK kinase (MEK) inhibitor, PD98059, but were not affected by the tyrosine kinase inhibitor genistein. In contrast, both AVP-induced MAPK and NHE activities were inhibited by genistein and MEK inhibitor but were not affected by staurosporine. Immunoprecipitation studies demonstrate that PMA, but not AVP, enhances the basal phosphorylation of the NHE-1. In this study, MAPKs are suggested to be a part of converging signaling leading to NHE activation by PKC-dependent and AVP-tyrosine kinase-dependent pathways. We propose that the MAPK activation of the NHE-1 does not involve phosphorylation of this exchanger protein. On the other hand, PKC can lead to phosphorylation and to additional activation of the NHE-1 through a MAPK-independent pathway.
...
PMID:Stimulation of mitogen-activated protein kinase and Na+/H+ exchanger in human platelets. Differential effect of phorbol ester and vasopressin. 866

Full-length cytosolic phospholipase A2 (cPLA2) was cloned from U937 cells and polymorphonuclear leukocytes (PMNLs) while a naturally occurring variant of cPLA2, which lacks residues Val473-Ala749 but has a C-terminal extension of ILMNLSEYMLWMSKVKRFM (DcPLA2) was cloned from PMNLs and mononuclear leukocytes. We were unable to clone DcPLA2 from U937 cells. When cPLA2 and DcPLA2 were expressed in insect cells, both proteins were detected in cell lysates by SDS/PAGE as single bands of apparent molecular masses 100 kDa and 57 kDa, respectively. Full-length cPLA2 was phosphorylated stoichiometrically by p42 mitogen-activated protein (MAP) kinase in vitro at a similar rate to other physiological substrates of this protein kinase and the major site of phosphorylation was identified by amino acid sequencing as Ser505. [32P]Ser(P)505 in cPLA2 was only dephosphorylated at a slow rate by mammalian tissue homogenates. Protein phosphatases 2A, 2B and 2C all contributed significantly to the overall dephosphorylation of cPLA2. The phosphorylation of cPLA2 by p42 MAP kinase correlated with an approximately 1.5-fold increase in specific enzyme activity which was reversed by dephosphorylation.
...
PMID:Cloning and expression of cystolic phospholipase A2 (cPLA2) and a naturally occurring variant. Phosphorylation of Ser505 of recombinant cPLA2 by p42 mitogen-activated protein kinase results in an increase in specific activity. 870 69

When HD3 colon carcinoma cells differentiate to fluid-transporting, enterocytic-like cells, they down-regulate their protein kinase C (PKC) beta levels 5-10-fold and lose two responses to basic fibroblast growth factor (FGF): proliferation and the ability to activate p57 mitogen-activated protein (MAP) kinase. HD3 cells were transfected with expression plasmids for the splice variants PKC-beta 1 and PKC-beta 2 and the empty vector for a control. Each of two PKC-beta 1 and each of two PKC-beta 2 transfectant clones exhibited elevated levels of Ca(2+)-and phosphatidylserine-dependent PKC activity. Both PKC-beta 1 transfectant clones had elevated levels of PKC-beta 1 protein compared with the PKC-beta 2 transfectants or controls, whereas both PKC-beta 2 transfectant clones had elevated levels of PKC-beta 2 protein compared with PKC-beta 1 transfectants. Control transfectants had no detectable PKC-beta 2 protein. Similar levels of PKC-alpha were found in all lines. Each PKC-beta transfectant was less differentiated than the parental line and had regained proliferative response to basic FGF. Increased growth rates in athymic mice were seen for PKC-beta 2 and PKC-beta 1 transfectant cells. Immunocytochemistry of the sectioned tumors showed enhanced protein levels of PKC-beta 2 and PKC-beta 1, correlating increased levels of these isonzymes with increased growth. Increased myelin-basic protein (MBP) kinase activities of M(r) 44,000, 57,000, 63,000, 110,000, and 130,000 by in-gel kinase assay characterized each PKC-beta transfectant. Both Western blotting and immunoprecipitation studies from 35S-prelabeled cells with a pan-erk antibody showed no increase in protein abundance of MAP kinases of M(r) 44,000, 57,000, and 63,000, suggesting that elevated PKC-beta levels led to activation of the smaller three MAP and MBP kinases. Activation of p57 MAP kinase in each PKC-beta transfectant was demonstrated by immunoprecipitation with an antiphosphotyrosine monoclonal antibody and then by assay of the immunoprecipitates by in-gel kinase assay on MBP. p57 MAP kinase was distinguished from the M(r) 54,000 stress-activated protein kinases, which migrated more rapidly on SDS gels and could be detected by in-gel kinase assay on MBP only after cellular stress. Thus, expression of elevated levels of PKC-beta 1 and PKC-beta 2 in differentiated HD3 colon carcinoma cells blocked their differentiation, enabled them to proliferate in response to basic FGF like undifferentiated cells, increased their growth rate in athymic mice, and activated several MBP kinases, among them, p57 MAP kinase.
...
PMID:Protein kinase C beta 1 and protein kinase C beta 2 activate p57 mitogen-activated protein kinase and block differentiation in colon carcinoma cells. 873 68

1. Phosphorylation of caldesmon was assayed in canine colonic circular smooth muscle strips labelled with 32P and stimulated with 10 microM acetylcholine. Caldesmon was isolated by two-dimensional non-equilibrium pH gel electrophoresis. Stimulation with acetylcholine increased caldesmon phosphorylation significantly from a basal level of 0.6 +/- 0.07 to 1.1 +/- 0.15 mol P1 (mol caldesmon)-1 after 2 min. 2. MAP kinase activities were measured in SDS extracts of muscle by a gel reconstitution method using myelin basic protein. Myelin basic protein kinase activities were observed at 38, 44, 50 and 57 kDa by the gel reconstitution method. Endogenous caldesmon kinase activities were also identified by the gel reconstitution method at 38, 44 and 50 kDa. The 38 and 44 kDa kinases comigrated with proteins labelled by anti-ERK1 MAP kinase antibodies on Western blots. Both 38 and 44 kDa MBP kinase activities increased significantly during contractions induced by 10 microM acetylcholine, 0.1 microM neurokinin A and 70 mM potassium. 3. Phorbol dibutyrate (0.1 microM) potentiated activation of MAP kinases and contraction of depolarized muscles while producing a decrease in fura-2 fluorescence ratio. This suggests that protein kinase C activation is coupled to MAP kinase activity in colonic smooth muscle. 4. MAP kinases isolated form muscle homogenates by Mono Q chromatography were assayed using the specific MAP kinase substrate peptide APRTPGGRR. Stimulation of muscles for 2 min with 10 microM acetylcholine activated both ERK1 and ERK2 MAP kinase activities 2-fold. 5. To determine the effects of caldesmon phosphorylation by MAP kinase on the cross-bridge cycle, actin sliding velocity was measured with an in vitro motility assay. Unphosphorylated turkey gizzard caldesmon (3 microM) significantly reduced mean sliding velocity. Phosphorylation of caldesmon with sea star ERK1 MAP kinase reversed the inhibitory effect of caldesmon on sliding velocity. The results are consistent with a protein kinase cascade being activated by contractile agonists in gastrointestinal smooth muscle which activates ERK MAP kinases leading to phosphorylation of caldesmon. Phosphorylation of caldesmon in vivo may reverse inhibitory influences of caldesmon on cross-bridge cycling.
...
PMID:Activation of MAP kinases and phosphorylation of caldesmon in canine colonic smooth muscle. 888 69

Specific transcription in late G1, mediated by the transcription factors SBF (Swi4p-Swi6p) and MBF (Mbp1p-Swi6p), is crucial for cell cycle progression in budding yeast. In order to better understand the G1/S transition, we initiated a search for conditional mutations synthetic lethal with swi4delta. One of the isolated mutants, rsf8swi4delta, showed a growth defect due to cell lysis. rsf8 is allelic to PKC1, encoding a protein kinase C homologue which controls cell integrity. In the presence of the rsf8/(pkc1-8) mutation, a functional SBF but not MBF is required for viability. Importantly, swi4delta and swi6delta strains are hypersensitive to calcofluor white and SDS, indicating that they possess a weakened cell wall. Overexpression or ectopic expression of CLN did not suppress the pkc1-8swi4delta mutant phenotype, thus SBF must control cell integrity independently, rather than acting through CLN expression. We found that at least six genes involved in cell wall biosynthesis are periodically expressed at the G1/S phase boundary. In all six cases, cell cycle-regulated expression is due mainly to Swi4p. Finally, we found that the PKC1 MAP kinase pathway is a positive regulator of five of these cell wall genes, these genes being novel targets of regulation by this pathway. We suggest that SBF and the PKC1 MAP kinase pathway act in concert to maintain cell integrity during bud formation.
...
PMID:Coordinated regulation of gene expression by the cell cycle transcription factor Swi4 and the protein kinase C MAP kinase pathway for yeast cell integrity. 889 Jan 73

Autophosphorylation of the recombinant mitogen-activated protein kinase (MAPK) from Xenopus laevis has been studied to detect the conformational changes in the region of regulatory phosphorylation upon enzyme activation. Slow autophosphorylation of Xenopus MAPK occurred predominantly on tyrosine, the major phosphoregulatory site of MAPKs, through an intramolecular mechanism and was accompanied by a low magnitude stimulation of the catalytic activity towards an exogenous substrate, myelin basic protein. Autophosphorylated but not unphosphorylated enzyme was shown to interact with the protein substrate. In contrast to the previously reported reversibility of many tyrosine kinase reactions, the tyrosine phosphorylation of Xenopus MAPK was found to be irreversible in the presence of high ADP concentrations, although ADP could competitively inhibit both autophosphorylation and myelin basic protein phosphorylation. We concluded, therefore, that the phosphoregulatory tyrosine is no more accessible to an intramolecular phosphotransferase reaction and is out of the reach of the enzyme catalytic center after phosphorylation. The conformational changes in the region of regulatory phosphorylation resulted in a reduced immunoprecipitation of autophosphorylated and MAPK-kinase-phosphorylated forms of the enzyme by a polyclonal antibody raised against a synthetic peptide corresponding to residues 173-197 of Xenopus MAPK which includes the sites of regulatory phosphorylation. The reduced recognition was not due to the phosphorylation itself, since the antibody efficiently immunoprecipitated SDS-denatured forms of the phosphorylated enzyme. The antibody was not a neutralizing antibody, allowing unphosphorylated MAPK to undergo autophosphorylation while in the immune complex. However, autophosphorylation caused a release of phosphorylated enzyme from the immune complex, suggesting that dramatic conformational changes, which could even overcome the antibody constraints, took place in the phosphoregulatory region of MAPK upon enzyme activation.
...
PMID:Phosphoregulatory tyrosine of Xenopus mitogen-activated protein kinase is out of the reach of the enzyme catalytic center after autophosphorylation. Biochemical evidence for conformational changes upon phosphorylation. 891 26

During meiotic maturation, numerous cytoplasmic and nuclear events take place that prepare the oocytes for fertilization. These changes are initiated by an increase in the activity of several kinases, most notably maturation-promoting factor, also called histone H1 kinase. Another kinase, mitogen-activated protein (MAP) kinase, is also stimulated during this period. In this study, we investigated the role of MAP kinase in bovine oocyte maturation. First, the kinetics of activation of histone H1 and MAP kinases during maturation were assessed simultaneously by evaluating their catalytic activities in vitro. We found that they are activated at approximately the same time, around germinal vesicle breakdown (GVBD). Then, at approximately 15 h of maturation, the activity of H1 kinase temporarily decreases, whereas MAP kinase remains high through the metaphase II stage. Second, the activation and catalytic activity of MAP kinase was directly evaluated by Western blotting and by an in-gel kinase assay. We determined that MAP kinase becomes activated and exhibits a decreased mobility through SDS-polyacrylamide gels, and that its catalytic activity increases as maturation progresses. In our system, most of the MAP kinase activity can be attributed to p42MAPK2. Third, the activation pathway of MAP kinase was explored. In Xenopus oocytes, MAP kinase is activated by a kinase cascade that includes several upstream activators; one of them is the product of the proto-oncogene mos. In bovine oocytes, injection of Mos RNA elicited a rapid maximal activation of MAP kinase that resulted in accelerated resumption of meiosis and GVBD. These results were thought to be mediated by an expression of a kinase-active Mos RNA failed to activate MAP kinase. Together, these results suggest a role for MAP kinase during the initiation and progression of meiosis in bovine oocytes. The data also suggest the presence of an MAP kinase-activating cascade that can be initiated by the Mos protein.
...
PMID:Potential role of mitogen-activated protein kinase during meiosis resumption in bovine oocytes. 894 82


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

---