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:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chronic myeloid leukemia (CML) is characterized by the presence of a 210-kD protein (P210bcr-abl) in the cytoplasm of leukemic cells, generated by the reciprocal translocation between chromosome 9 and chromosome 22. Due to this translocation, the abl oncogene is coupled to the bcr gene, forming a new determinant in this protein encoded by the bcr-abl joining region. In the joining region itself, either the bcr exon 2 is coupled to the abl exon 2 (b2-a2), or the bcr exon 3 is coupled to the abl exon 2 (b3-a2). Thus, these joining regions form by definition new tumor-specific determinants in the respective chimeric P210-bcr-abl molecules. This paper addresses the question as to whether these tumor-specific joining regions are exposed on the P210bcr-abl molecule in such a way that antibodies can be generated to detect these sites. To test this possibility a polyclonal antiserum, termed BP-1, was raised against a synthetic peptide representative for the b2-a2 joining region. The reactivity of BP-1 was analyzed in an ELISA system on various synthetic peptides. Peptide inhibition studies showed the presence of antibodies to different parts of the b2-a2 peptide in the polyvalent antiserum. The reactivity of BP-1 was then tested with native P210bcr-abl molecules in various CML cell lines (K562, LAMA-84, and BV173) using a protein kinase assay. In this context, the bcr-abl junctions were first analyzed at the DNA and RNA level. The present study indicates that BP-1 specifically recognizes the b2-a2 junction in native P210bcr-abl. Furthermore, BP-1 clearly discriminates between b2-a2 P210bcr-abl and b3-a2 P210bcr-abl. We conclude that the tumor-specific b2-a2 joining region is antigenically exposed on the native P210bcr-abl molecule.
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PMID:Antibody recognition of the tumor-specific bcr-abl joining region in chronic myeloid leukemia. 246 13

There is mounting evidence that in fat and other insulin-sensitive cells activation of protein synthesis may involve the dissociation of a protein (4E-BP1) from eukaryotic initiation factor (eIF)-4E thus allowing formation of the eIF-4F complex. This study compares the effects of insulin and epidermal growth factor (EGF) on the phosphorylation of 4E-BP1 in fat-cells (followed by gel-shift assays and incorporation of 32P) and on its association with eIF-4E. Several lines of evidence suggest that mitogenactivated protein kinase (MAP kinase) is not involved in these effects of insulin. Insulin causes much more extensive phosphorylation and dissociation of 4E-BP1 from eIF-4E than EGF, although EGF activates MAP kinase to a much greater extent than insulin. Moreover, MAP kinase does not phosphorylate 4E-BP1 when it is complexed with eIF-4E. In contrast, insulin activates the 40S ribosomal protein S6 kinase (p70S6K) 18-fold compared with a 2-fold activation by EGF, and the time course of this activation is similar to the phosphorylation and dissociation of 4E-BP1. Rapamycin, a specific inhibitor of the activation of this latter kinase, inhibits dissociation of 4E-BP1 from eIF-4E in cells incubated with insulin but reveals a phosphorylated from of 4E-BP1 which remains bound to eIF-4E. It is concluded that in rat epididymal fat-cells, the effects of insulin on 4E-BP1 involves multiple phosphorylation events. One phosphorylation event is rapamycin-insensitive, occurs only on bound 4E-BP1 and does not initiate dissociation. The second event does result in dissociation and is blocked by rapamycin, suggesting that the p70S6K signalling pathway is involved: p70S6K itself is probably not involved directly as this kinase does not phosphorylate 4E-BP1 in vitro.
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PMID:Both rapamycin-sensitive and -insensitive pathways are involved in the phosphorylation of the initiation factor-4E-binding protein (4E-BP1) in response to insulin in rat epididymal fat-cells. 868 86

The immunosuppressant, rapamycin, inhibits cell growth by interfering with the function of a novel kinase, termed mammalian target of rapamycin (mTOR). The putative catalytic domain of mTOR is similar to those of mammalian and yeast phosphatidylinositol (PI) 3-kinases. This study demonstrates that mTOR is a component of a cytokine-triggered protein kinase cascade leading to the phosphorylation of the eukaryotic initiation factor-4E (eIF-4E) binding protein, PHAS-1, in activated T lymphocytes. This event promotes G1 phase progression by stimulating eIF-4E-dependent translation initiation. A mutant YAC-1 T lymphoma cell line, which was selected for resistance to the growth-inhibitory action of rapamycin, was correspondingly resistant to the suppressive effect of this drug on PHAS-1 phosphorylation. In contrast, the PI 3-kinase inhibitor, wortmannin, reduced the phosphorylation of PHAS-1 in both rapamycin-sensitive and -resistant T cells. At similar drug concentrations (0.1-1 microM), wortmannin irreversibly inhibited the serine-specific autokinase activity of mTOR. The autokinase activity of mTOR was also sensitive to the structurally distinct PI 3-kinase inhibitor, LY294002, at concentrations (1-30 microM) nearly identical to those required for inhibition of the lipid kinase activity of the mammalian p85-p110 heterodimer. These studies indicate that the signaling functions of mTOR, and potentially those of other high molecular weight PI 3-kinase homologs, are directly affected by cellular treatment with wortmannin or LY294002.
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PMID:Direct inhibition of the signaling functions of the mammalian target of rapamycin by the phosphoinositide 3-kinase inhibitors, wortmannin and LY294002. 889 71

Granulocyte-macrophage colony-stimulating factor (GM-CSF) and Steel factor (SLF) synergistically stimulate Raf-1 kinase activity, protein synthesis, and proliferation in hematopoietic MO7e cells; synergistic action of these factors is blocked by the suppressive chemokines macrophage inflammatory protein-1alpha (MIP-1alpha) and interferon-inducible protein 10 (IP-10; Aronica et al, J Biol Chem 270:21998, 1995). We assessed the potential for both stimulatory and inhibitory factors to act through the MAP kinase signaling pathway by studying the effects of growth factors and chemokines on MAP kinase activation. Also, because activation of kinase signaling pathways and stimulation of protein synthesis by peptide growth factors are associated with increased phosphorylation of eukaryotic initiation factor 4E (elF-4E) and the translational repressor 4E-binding protein 1 (4E-BP1) in some target cells, we investigated whether growth factor treatment could alter eIF-4E or 4E-BP1 phosphorylation state in MO7e cells. We report that treatment of MO7e cells with GM-CSF and SLF stimulated significant, greater-than-additive increases in MAP kinase activity and the phosphorylation of both eIF-4E and 4E-BP1. Increased 4E-BP1 phosphorylation correlated with a decrease in the association of 4E-BP1 with eIF-4E. Growth factor-induced phosphorylation of 4E-BP1 and dissociation of 4E-BP1 from eIF-4E was blocked in cells treated with rapamycin, wortmannin, or PD098059. Treatment of cells with IP-10 or MIP-1alpha blocked the stimulatory effects of GM-CSF and SLF, resulting in suppression of MAP kinase activity, eIF-4E and 4E-BP1 phosphorylation, and eIF-4E/4E-BP1 dissociation. Our results suggest that GM-CSF and SLF exert part of their combined growth-promoting effects on MO7e cells through activation of MAP kinase and enhancement of eIF-4E and 4E-BP1 phosphorylation and dissociation and that suppression of growth factor-induced protein synthesis by MIP-1alpha and IP-10 involves translational repression at the level of eIF-4E.
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PMID:Macrophage inflammatory protein-1alpha and interferon-inducible protein 10 inhibit synergistically induced growth factor stimulation of MAP kinase activity and suppress phosphorylation of eukaryotic initiation factor 4E and 4E binding protein 1. 1675 74

Infection with many viruses results in the selective shutoff of host protein synthesis. A common target for virus interference with host protein synthesis is the cap-binding protein complex, eIF4F. The large subunit of the complex, eIF4G, is cleaved upon picornavirus (except cardiovirus) infection. Infection with adenovirus and influenza virus causes dephosphorylation of the cap-binding subunit, eIF4E. Recently, it has been shown that infection with poliovirus or encephalomyocarditis virus activates 4E-BP1, which is a specific inhibitor of eIF4E. Here we show that early in adenovirus infection, 4E-BP1 and its related protein 4E-BP2 are phosphorylated and hence inactivated. This is not consistent with a role of 4E-BPs in adenovirus-induced shutoff, but could explain the increase in protein synthesis reported early in infection. Phosphorylation of 4E-BP1 and 4E-BP2 is consistent with earlier findings in adenovirus-infected cells on the activation of the protein kinase p70(S6k), whose phosphorylation lies on the same pathway as 4E-BPs, by E1A. Findings similar to those described here were reported for 4E-BP1 by D. Feigenblum and R. J. Schneider (1996, Mol. Cell. Biol. 16, 5450-5457).
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PMID:Adenovirus infection inactivates the translational inhibitors 4E-BP1 and 4E-BP2. 934 20

The mu-opioid receptor mediates the analgesic and addictive properties of morphine. Despite the clinical importance of this G-protein-coupled receptor and many years of pharmacological research, few intracellular signaling mechanisms triggered by morphine and other mu-opioid agonists have been described. We report that mu-opioid agonists stimulate three different effectors of a phosphoinositide 3-kinase (PI3K)-dependent signaling cascade. By using a cell line stably transfected with the mu-opioid receptor cDNA, we show that the specific agonist [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin (DAMGO) stimulates the activity of Akt, a serine/threonine protein kinase implicated in protecting neurons from apoptosis. Activation of Akt by DAMGO correlates with its phosphorylation at serine 473. The selective PI3K inhibitors wortmannin and LY294002 blocked phosphorylation of this site, previously shown to be necessary for Akt enzymatic activity. DAMGO also stimulates the phosphorylation of two other downstream effectors of PI3K, the p70 S6 kinase and the repressors of mRNA translation, 4E-BP1 and 4E-BP2. Upon mu-opioid receptor stimulation, p70 S6 kinase is activated and phosphorylated at threonine 389 and at threonine 421/serine 424. Phosphorylation of p70 S6 kinase and 4E-BP1 is also repressed by PI3K inhibitors as well as by rapamycin, the selective inhibitor of FRAP/mTOR. Consistent with these findings, DAMGO-stimulated phosphorylation of 4E-BP1 impairs its ability to bind the translation initiation factor eIF-4E. These results demonstrate that the mu-opioid receptor activates signaling pathways associated with neuronal survival and translational control, two processes implicated in neuronal development and synaptic plasticity.
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PMID:mu-Opioid receptor activates signaling pathways implicated in cell survival and translational control. 972 92

The effects of insulin and rapamycin on the phosphorylation of the translation regulator, initiation factor 4E-binding protein 1 (4E-BP1) have been studied in rat fat cells by following changes in the incorporation of 32P from [32P]Pi under steady-state conditions. Both unbound 4E-BP1 and 4E-BP1 bound to eukaryotic initiation factor 4E (eIF4E) were isolated from the cells and then digested with trypsin and other proteases; the radiolabelled phosphopeptides were then separated by two-dimensional thin- layer analysis and HPLC. The results provide confirmation of the conclusion of Fadden, Haystead and Lawrence [J. Biol. Chem. (1997) 272, 10240-10247] that insulin increases the phosphorylation of four sites that fit a Ser/Thr-Pro motif (Thr-36, Thr-45, Ser-64 and Thr-69) and that taken together these phosphorylations result in the dissociation of 4E-BP1 from eIF4E. The effects of insulin on the phosphorylation of these sites, and hence dissociation from eIF4E, are blocked by rapamycin. However, the present study also provides evidence that insulin increases the phosphorylation of 4E-BP1 bound to eIF4E on a further site (Ser-111) and that this is by a rapamycin-insensitive mechanism. Extraction of rat epididymal fat cells followed by chromatography on Mono-S and Superose 12 columns resulted in the separation of both an insulin-stimulated eIF4E kinase and an apparently novel kinase that is highly specific for Ser-111 of 4E-BP1. The 4E-BP1 kinase was activated more than 10-fold by incubation of the cells with insulin and was markedly more active towards 4E-BP1 bound to eIF4E than towards unbound 4E-BP1. The effects of insulin were blocked by wortmannin, but not by rapamycin. A 14-mer peptide based on the sequence surrounding Ser-111 of 4E-BP1 was also a substrate for the kinase, but peptide substrates for other known protein kinases were not. The kinase is quite distinct from casein kinase 2, which also phosphorylates Ser-111 of 4E-BP1. The possible importance of these kinases in the phosphorylation of 4E-BP1 in fat cells is discussed. It is suggested that the phosphorylation of Ser-111 might be a priming event that facilitates the subsequent phosphorylation of Thr-36, Thr-45, Ser-64 and Thr69 by a rapamycin-sensitive process that initiates the dissociation of 4E-BP1 from eIF4E and hence the formation of the eIF4F complex.
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PMID:Insulin-stimulated kinase from rat fat cells that phosphorylates initiation factor 4E-binding protein 1 on the rapamycin-insensitive site (serine-111). 980 82

Previous studies indicated that amino acids may activate the protein kinase activity of the target of rapamycin (TOR) and thereby augment and/or mimic the effects of insulin on protein synthesis, p70(S6k) phosphorylation, and multicellular clustering in adipocytes. To identify the individual amino acids responsible for these effects, the present study focused on the TOR substrate and translational repressor 4E-BP1. A complete mixture of amino acids stimulated the phosphorylation of 4E-BP1, decreasing its association with eukaryotic initiation factor eIF-4E. Studies on subsets of amino acids and individual amino acids showed that L-leucine was the amino acid responsible for most of the effects on 4E-BP1 phosphorylation; however, the presence of other amino acids was required to observe a maximal effect. The stimulatory effect of leucine was stereospecific and not mimicked by other branched chain amino acids but was mimicked by the leucine metabolite alpha-ketoisocaproate (alpha-KIC). The effect of alpha-KIC, but not leucine, was attenuated by the transaminase inhibitor (aminooxy)acetate. The latter result indicates that the effects of alpha-KIC required its conversion to leucine. Half-maximal stimulation of 4E-BP1 phosphorylation occurred at approximately 430 microM; therefore, the response was linear within the range of circulating concentrations of leucine found in various nutritional states.
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PMID:Amino acid effects on translational repressor 4E-BP1 are mediated primarily by L-leucine in isolated adipocytes. 981 71

Regulation of translation of mRNAs coding for specific proteins plays an important role in controlling cell growth, differentiation, and transformation. Two proteins have been implicated in the regulation of specific mRNA translation: eukaryotic initiation factor eIF4E and ribosomal protein S6. Increased phosphorylation of eIF4E as well as its overexpression are associated with stimulation of translation of mRNAs with highly structured 5'-untranslated regions. Similarly, phosphorylation of S6 results in preferential translation of mRNAs containing an oligopyrimidine tract at the 5'-end of the message. In the present study, leucine stimulated phosphorylation of the eIF4E-binding protein, 4E-BP1, in L6 myoblasts, resulting in dissociation of eIF4E from the inactive eIF4E.4E-BP1 complex. The increased availability of eIF4E was associated with a 1.6-fold elevation in ornithine decarboxylase relative to global protein synthesis. Leucine also stimulated phosphorylation of the ribosomal protein S6 kinase, p70(S6k), resulting in increased phosphorylation of S6. Hyperphosphorylation of S6 was associated with a 4-fold increase in synthesis of elongation factor eEF1A. Rapamycin, an inhibitor of the protein kinase mTOR, prevented all of the leucine-induced effects. Thus, leucine acting through an mTOR-dependent pathway stimulates the translation of specific mRNAs both by increasing the availability of eIF4E and by stimulating phosphorylation of S6.
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PMID:Leucine regulates translation of specific mRNAs in L6 myoblasts through mTOR-mediated changes in availability of eIF4E and phosphorylation of ribosomal protein S6. 1020 76

Recent studies indicate that phosphatidylinositide-3OH kinase (PI3K)-induced S6 kinase (S6K1) activation is mediated by protein kinase B (PKB). Support for this hypothesis has largely relied on results obtained with highly active, constitutively membrane-localized alleles of wild-type PKB, whose activity is independent of PI3K. Here we set out to examine the importance of PKB signaling in S6K1 activation. In parallel, glycogen synthase kinase 3beta (GSK-3beta) inactivation and eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) phosphorylation were monitored as markers of the rapamycin-insensitive and -sensitive branches of the PI3K signaling pathway, respectively. The results demonstrate that two activated PKBalpha mutants, whose basal activity is equivalent to that of insulin-induced wild-type PKB, inhibit GSK-3beta to the same extent as a highly active, constitutively membrane-targeted wild-type PKB allele. However, of these two mutants, only the constitutively membrane-targeted allele of PKB induces S6K1 activation. Furthermore, an interfering mutant of PKB, which blocks insulin-induced PKB activation and GSK-3beta inactivation, has no effect on S6K1 activation. Surprisingly, all the activated PKB mutants, regardless of constitutive membrane localization, induce 4E-BP1 phosphorylation and the interfering PKB mutant blocks insulin-induced 4E-BP1 phosphorylation. The results demonstrate that PKB mediates S6K1 activation only as a function of constitutive membrane localization, whereas the activation of PKB appears both necessary and sufficient to induce 4E-BP1 phosphorylation independently of its intracellular location.
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PMID:Protein kinase B localization and activation differentially affect S6 kinase 1 activity and eukaryotic translation initiation factor 4E-binding protein 1 phosphorylation. 1033 Jan 91


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