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)

To gain insight into the mechanisms involved in the formation of maternally stored mRNPs during Xenopus laevis development, we searched for soluble cytoplasmic proteins of the oocyte that are able to selectively bind mRNAs, using as substrate radiolabeled mRNA. In vitro mRNP assembly in solution was followed by UV-cross-linking and RNase digestion, resulting in covalent tagging of polypeptides by nucleotide transfer. Five polypeptides of approximately 54, 56 60, 70, and 100 kD (p54, p56, p60, p70, and p100) have been found to selectively bind mRNA and assemble into mRNPs. These polypeptides, which correspond to previously described native mRNP components, occur in three different particle classes of approximately 4.5S, approximately 6S, and approximately 15S, as also determined by their reactions with antibodies against p54 and p56. Whereas the approximately 4.5S class contains p42, p60, and p70, probably each in the form of individual molecules or small complexes, the approximately 6S particles appears to consist only of p54 and p56, which occur in a near-stoichiometric ratio suggestive of a heterodimer complex. The approximately 15S particles contain, in addition to p54 and p56, p60 and p100 and this is the single occurring form of RNA-binding p100. We have also observed changes in the in vitro mRNA binding properties of these polypeptides during oogenesis and early embryonic development, in relation to their phosphorylation state and to the activity of an approximately 15S particle-associated protein kinase, suggesting that these proteins are involved in the developmental translational regulation of maternal mRNAs.
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PMID:Different forms of soluble cytoplasmic mRNA binding proteins and particles in Xenopus laevis oocytes and embryos. 167 Jul 77

Triton-insoluble cytoskeleton of nonpigment cells has bound protein kinase that phosphorylates, with or without added cAMP, tubulins and the intermediate filament proteins p60, p56, p53, and p45a to give multiple charge variants. In the absence of 8-Br-cAMP, Triton-insoluble cytoskeletons from xanthophores also phosphorylate p60, p56, and p45a, but not p53; tubulin phosphorylation may also be reduced. In the presence of 8-Br-cAMP, p53, as well as several other peptides, are phosphorylated. One of these latter peptides was identified as the carotenoid droplet (pigment organelle) protein p57, whose phosphorylation and dephosphorylation precede pigment dispersion and aggregation respectively (Lynch et al.: J. Biol. Chem. 261:4204-4211, 1986). The amount of pp57 produced depends on the state of pigment distribution in the xanthophores used to prepare the cytoskeletons for labeling. With cytoskeletons from xanthophores with aggregated pigment, pp57 is a major labeled phosphoprotein seen in two-dimensional gels. With cytoskeletons prepared from xanthophores with dispersed pigment, the yield of labeled pp57 is greatly reduced (by at least 90%). Together with earlier results, we propose that, in the aggregated state, p57 serves to bind carotenoid droplets to the cytoskeletons, most likely the microtubules. The significance of other cAMP-dependent phosphorylation reactions is unknown but may be related to cAMP-induced cytoskeleton rearrangement in intact xanthophores.
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PMID:cAMP-independent and cAMP-dependent protein phosphorylations by isolated goldfish xanthophore cytoskeletons: evidence for the association of cytoskeleton with a carotenoid droplet protein. 254 7

The LSTRA murine thymoma cell line contains an elevated level of tyrosine protein kinase activity. When a microsomal preparation from these cells is incubated in vitro with ATP, the principal tyrosine protein kinase substrate is a 56,000-dalton protein, p56. We have found that an activity phosphorylating p56 on tyrosine can also be detected at low levels in microsomes from most, but not all, T lymphoma cell lines and from normal thymic tissue. Only 1 of 30 other lymphoma cell lines was found to contain an elevated level of such a tyrosine protein kinase. An activity that phosphorylated p56 in vitro was not detectable in the cells of other hematopoietic lineages. Anti-peptide antibodies reactive with the site of in vitro tyrosine phosphorylation of p56 allowed us to determine that the apparent abundance of the p56 polypeptide parallels closely the level of the tyrosine protein kinase activity in the cell lines examined. This suggests that p56 is the protein kinase responsible for the elevated tyrosine protein kinase activity in LSTRA cells and that the phosphorylation of p56 observed in vitro results from autophosphorylation. Two-dimensional tryptic peptide mapping revealed that p56 is distinct from the proteins encoded by the cellular genes which are the progenitors of retroviral tyrosine protein kinases, src, yes, fgr, abl, fes, and ros. Additionally, none of these proto-oncogenes was found to be transcribed at elevated levels in LSTRA or Thy19 cells. Like the catalytic subunit of the cyclic AMP-dependent protein kinase, the cellular and viral forms of p60src, and the protein phosphatase calcineurin B, p56 contains covalently bound fatty acid.
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PMID:Characterization of the protein apparently responsible for the elevated tyrosine protein kinase activity in LSTRA cells. 654 43

The translation of a capped, polyadenylated RNA after injection into the nucleus of Xenopus oocytes occurs only if the RNA contains an intron. A single point mutation in the splice donor site prevents translation. Intron-less RNA is exported efficiently to the cytoplasm and is held, undegraded, in a translationally inert state for several days. Translation can be activated by treating the oocytes with progesterone or by injecting antibodies that bind the FRGY2 class of messenger RNA binding proteins, p56 and p60, but these antibodies are only effective if delivered to the nucleus. Inhibitors of casein kinase II also activate translation whereas phosphatase inhibitors block progesterone-mediated activation of translation. These data suggest the presence of an RNA handling pathway in the nucleus of Xenopus oocytes which is regulated by casein kinase type II phosphorylation and which directs transcripts to be sequestered by p56/p60 or by closely related proteins. This pathway can be bypassed if the RNA contains an intron and it can be reversed by progesterone treatment. These data may have implications for understanding translational control during early development.
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PMID:Intron-less RNA injected into the nucleus of Xenopus oocytes accesses a regulated translation control pathway. 781 14

We show that Escherichia coli produce a factor that inhibits the activity of tyrosine and serine/threonine protein kinases. The factor is a protein found in the periplasmic compartment and is also secreted into the culture medium. Using a particle concentration fluorescence immunoassay specific for tyrosine kinase activity and inhibition of the tyrosine kinase p56(lck), we purified this factor to apparent homogeneity. Analysis of trypsin-digested fragments by mass spectrometry identified the inhibitor as the bacterial periplasmic protein UDP-sugar hydrolase, an enzyme with potent and nonspecific 5'-nucleotidase activity. Overexpression of the enzyme in bacteria leads to coordinate increases in both 5'-nucleotidase and p56(lck) inhibitory activity, confirming the identity of the inhibitor. The kinase inhibitory activity appears to be due to the formation of adenosine, which we show is inhibitory for p56(lck), cAMP-dependent protein kinase, and casein kinase. Overexpression of UDP-sugar hydrolase leads to an increase in the recovery of enteropathogenic E. coli following infection of HeLa cell monolayers and corresponding alterations in tyrosine-phosphorylated host proteins. These results suggest that UDP-sugar hydrolase may be an important factor affecting host cell function following intracellular bacterial infection.
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PMID:Identification of a bacterial inhibitor of protein kinases. Mechanism and role in host cell invasion. 879 49

Two forms (G-I and G-II kinases) of casein kinase II(CK-II) in a partially purified CK-II fraction (Mono Q fraction) of mouse liver were separated by means of glycyrrhizin (GL)-affinity column chromatography. Biochemical characterization revealed that these two GL-binding kinases were identical to CK-II. Two phosphate acceptors [p99 (pI 7.0) and p56] copurified with CK-II were identified as ERp99 (Hsp-90-family protein) and calreticulin, respectively. Another protein [p100 (pI 9.0)], which crossreacted with anti-serum against human glucocorticoid receptor (GR), was associated with ERp99. Phosphorylation of p99 [a hetero-complex of p99 (pI 7.0) and p100 (pI 9.0)] and p56 by CK-II in vitro was stimulated significantly by low levels (1-3 microM) of GL, but inhibited significantly at doses above 20 microM. However, no effect of GL on autophosphorylation of ERp99 was detected. The data provided here suggest that GL can regulate CK-II-mediated phosphorylation involved in the GL-induced biological effects in mammalian cells.
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PMID:Identification of glycyrrhizin-binding protein kinase as casein kinase II and characterization of its associated phosphate acceptors in mouse liver. 885 10

A 56 kDa protein kinase was molecularly cloned from human fetal brain. This protein kinase (p56 KKIAMRE) shares homology with p42 KKIALRE (Meyerson et al., 1992) and is related to the proline-directed protein kinase group of signal transducing enzymes. The p56 KKIAMRE and p42 KKIALRE protein kinases exhibit mutually exclusive expression in reproductive tissues; p56 KKIAMRE in testis and p42 KKIALRE in ovary. p56 KKIAMRE and p42 KKIALRE may therefore contribute to signal transduction within these highly differentiated tissues. p56 KKIAMRE and p42 KKIALRE are activated by treatment of cells with epidermal growth factor (EGF). Although p56 KKIAMRE and p42 KKIALRE contain the MAP kinase dual phosphorylation motif Thr-Xaa-Tyr (Thr-Asp-Tyr), phosphorylation on Thr and Tyr within this motif is not required for EGF-stimulated protein kinase activity.
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PMID:Molecular cloning of the epidermal growth factor-stimulated protein kinase p56 KKIAMRE. 900 Jan 30

Previous studies suggest that p56(lck) activity influences thymocyte development at a stage prior to TCR alphabeta expression. Transgenic mice that express high levels of p56(lck) activity during thymopoiesis develop thymic lymphomas consisting of cells with immature surface phenotypes. We have utilized cell lines derived from lck-induced thymic tumors to define biochemical pathways regulated by p56(lck) activity in immature thymocytes. Here we report that components of the Ras/Raf/MAPK pathway are constitutively activated in these lck-transformed immature thymoblasts. p56(lck) utilizes Shc and Grb2 adaptors to mediate activation of p21(ras) in the thymoblast lines by promoting tyrosine phosphorylation of the Shc protein and constitutive interaction between Shc and Grb2. The putative guanine nucleotide exchange factor p95(vav) is also maintained in constitutively tyrosine phosphorylated form as a result of elevated Lck activity. One target of activated Ras, the Raf-1 kinase, is hyperphosphorylated and downstream targets of activated Raf-1, Erk1 and Erk2, are hyperphosphorylated and activated in Lck-transformed thymocytes. Forskolin treatment reverses Raf-1 hyperphosphorylation in the cells and inhibits proliferation by blocking G1/S transition. In contrast, conventional protein tyrosine kinase inhibitors block proliferation by arresting Lck thymoblasts at G2/M. Lck-mediated stimulation of the Ras/Raf/MAPK pathway is also required to maintain cell viability by preventing programmed cell death. In summary, p56(lck) activity stimulates G1/S transition in immature thymoblasts and maintains cell viability via transduction of constitutive activation signals downstream to components of the Ras/Raf/MAPK pathway.
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PMID:Targets of p56(lck) activity in immature thymoblasts: stimulation of the Ras/Raf/MAPK pathway. 904 11

Intercellular adhesion molecule 1 (ICAM-1) (CD54) is an adhesion molecule of the immunoglobulin superfamily. The interaction between ICAM-1 on B lymphocytes and leukocyte function-associated antigen 1 on T cells plays a major role in several aspects of the immune response, including T-dependent B cell activation. While it was originally believed that ICAM-1 played a purely adhesive role, recent evidence suggests that it can itself transduce biochemical signals. We demonstrate that cross-linking of ICAM-1 results in the up-regulation of class II major histocompatibility complex, and we investigate the biochemical mechanism for the signaling role of ICAM-1. We show that cross-linking of ICAM-1 on the B lymphoma line A20 induces an increase in tyrosine phosphorylation of several cellular proteins, including the Src family kinase p53/p56(lyn). In vitro kinase assays showed that Lyn kinase was activated within 1 min after ICAM-1 cross-linking. In addition, ICAM-1 cross-linking resulted in activation of Raf-1 and mitogen-activated protein kinases, as determined by gel mobility shift. Activation of these kinases may represent important components in the cascade of signals that link ICAM-1 to various ICAM-1-elicited cellular responses. These data confirm the important role of ICAM-1 as a signaling molecule in B cell activation.
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PMID:Signaling through intercellular adhesion molecule 1 (ICAM-1) in a B cell lymphoma line. The activation of Lyn tyrosine kinase and the mitogen-activated protein kinase pathway. 908 38

Different classes of protein kinase inhibitors for protein kinase C, cAMP-dependent protein kinase or protein tyrosine kinases have been studied for their effect on phospholipid metabolism. The results show that among the compounds studied, only 4'-aminohydroxyflavone (AHF), previously described as a specific inhibitor of the protein tyrosine kinase p56(lck), markedly increased phosphatidylserine synthesis in Jurkat T cells. The biosyntheses of phosphatidylcholine and phosphatidylethanolamine were not affected. Also, the synthesis of phospholipids from tritium-labeled fatty acid as precursor was left unchanged by the p56(lck) inhibitor. The decreased phosphatidylserine synthesis induced when triggering the CD3-TCR complex was impaired by AHF, suggesting that p56(lck) could be implicated in the regulation of the serine-base exchange enzyme system. Direct evidence for the participation of p56(lck) in the regulation of the serine-base exchange enzyme system was obtained by using p56(lck)-deficient Jurkat cells (J.CaM 1.6) in which the basal base exchange activity was markedly increased and on the other hand AHF had no effect. In addition, transfection of J.Cam 1.6 cells with p56(lck)-cDNA allowed recovery of the AHF activity.
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PMID:The protein tyrosine kinase p56(lck) regulates the serine-base exchange activity in Jurkat T cells. 908 83


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