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)

Study of the mechanisms by which interferon (IFN) treatment of cells induces resistance to virus infections has been complicated by the multiple biochemical changes induced. Over 20 proteins are increased by IFN, including the double-stranded (ds) RNA-activated protein kinase, (2'-5') oligo A synthetase, surface proteins such as the major histocompatibility complex (MHC) proteins, and various proteins with unknown functions. The availability of cloned complementary DNAs for several IFN-induced proteins now allows us to probe their roles in IFN action. For instance, the murine Mx protein has been shown to confer resistance, to influenza virus. We studied chinese hamster ovary (CHO) cell clones expressing high constitutive levels of (2'-5') A synthetase as a result of transfection with the cDNA encoding the enzyme form which has a relative molecular mass (Mr) of 40K. Elevated enzyme correlates directly with resistance to infection by a picornavirus such as Mengo, but does not make the cells resistant to vesicular stomatitis virus (VSV).
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PMID:Constitutive expression of (2'-5') oligo A synthetase confers resistance to picornavirus infection. 282 34

When polymorphonuclear leukocytes (PMN) are exposed to most harvests of influenza A virus (depressing virus, DV) for 20 min, chemotactic, secretory, and oxidative functions are depressed upon subsequent exposure to soluble or particulate stimuli. Other harvests of influenza A virus (non-DV) do not alter these activities. The DV-induced changes in multiple functions suggest the virus may interfere with steps involved in PMN activation. Because some of these steps may be regulated by protein phosphorylation, we examined the effect of non-DV and DV on cellular protein phosphorylation. PMN loaded with 32P-labeled inorganic orthophosphate were exposed to non-DV, DV, or buffer for 30 min; cells were then treated with buffer, FMLP (10(-6) M), or PMA (100 ng/ml) for 30 s. Samples were sonicated and centrifuged; cytosolic and particulate fractions were analyzed by SDS-PAGE and autoradiography. Exposure of PMN to either non-DV or DV caused phosphorylation of several cell proteins. However, when DV-treated PMN were then stimulated with FMLP or PMA, further phosphorylation was inhibited compared to non-DV- or buffer-treated cells. This suggests that DV-induced depression of PMN end-stage functions may be due to changes in cell protein phosphorylation. DV could interfere with phosphorylation of PMN proteins by altering protein kinase activity. We therefore examined the influence of non-DV and DV on some parameters that could affect kinase function. PMN intracellular [Ca2+] was monitored by using the fluorescent Ca2+ indicator, Indo 1, and cAMP levels were measured by RIA. PMN treated with DV alone or DV plus FMLP had higher intracellular [CA2+] than PMN similarly treated with non-DV or buffer. Exposure of PMN to non-DV, DV, or buffer caused minimal changes in cAMP levels, and similar increases occurred in cAMP levels upon FMLP stimulation. To determine whether DV interferes with transmembrane signaling, the effect of influenza virus on PMN transmembrane potential was studied by using a fluorescent cyanine dye. Transmembrane potential changes were greater in PMN exposed to DV than to non-DV or buffer; however, subsequent stimulation with FMLP caused equivalent changes in transmembrane potential. Our data show that protein phosphorylation in PMN is induced by DV and non-DV infection; upon subsequent stimulation with FMLP or PMA, there is inhibited cellular phosphorylation only in PMN previously exposed to DV.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Alterations in cell protein phosphorylation in human neutrophils exposed to influenza A virus. A possible mechanism for depressed cellular end-stage functions. 283 42

Membranes isolated from chick embryo cells (CEC) were found to contain an endogenous protein kinase that phosphorylated endogenous proteins. 32P incorporation into membrane proteins was analysed by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE) and detected by autoradiography. Membrane phosphorylation in the presence of physiological saline (PM-phys) and in the presence of influenza virus (PM-V) were compared. Under short-time incubation (less than 1 min) with gamma-32P ATP there was practically no difference between PM-phys and PM-V in 32P incorporation. Under prolonged incubation (3-15 min), gradual dephosphorylation of the phosphoprotein moving in SDS-PAGE in the zone of relative molecular mass (Mr) of 60 kDa (phosphoprotein P60) was observed in PM-phys whereas in PM-V, phosphorylation of P60 increased with the time of incubation with gamma-32P ATP. Dephosphorylation of P60 in PM-phys was inhibited by 2.5 mmol/l EGTA as well as by 100 mumol/l chlorpromazine (CPZ) and stimulated by calmodulin (CaM) in the presence of Ca2+. Responsible for the dephosphorylation was probably the endogenous Ca2+ and/or CaM-dependent membrane protein phosphatase. It was inhibited by influenza virus (even in the presence of Ca2+ and CaM). The possible role of P60 phosphorylation in the first step of virus infection is discussed.
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PMID:Effect of influenza virus on protein phosphorylation in isolated membranes of chick embryo cells. 285 56

Plasmids encoding the amino terminal portion of an influenza virus hemagglutinin (HA) fused to polyoma virus middle T (mT) or large T (lT) sequences have been constructed. Stable expression of the chimeric proteins was obtained in established rat embryo fibroblasts following plasmid co-transfection and selection for G418 resistance. The synthesis and localization of the proteins was followed by metabolic labeling with [35S]methionine and [3H]mannose, cell fractionation, and immunoprecipitation with anti-polyoma T antibody. The HA leader and amino terminal peptide direct the synthesis of the lT and mT proteins into the endoplasmic reticulum where they undergo glycosylation, but this occurs with a very low efficiency. Most of the HA-mT and HA-lT fusion protein molecules do not enter completely into the endoplasmic reticulum, but rather achieve their normal locations in the cell as slightly higher molecular weight proteins, presumably due to the extra sequences derived from HA at their amino termini. HA-mT fusion protein is found to have associated tyrosine-specific protein kinase activity precipitable with anti-src as well as anti-T antibody, and cells expressing this fusion protein have a transformed phenotype.
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PMID:Expression of influenza hemagglutinin-polyoma T-antigen fusion proteins in a rat embryo fibroblast cell line. 303 93

We investigated the mechanisms by which influenza virus prevents shutoff of protein synthesis by a cellular protein kinase normally activated during infection. Earlier work has shown that influenza virus superinfection of cells previously infected by the adenovirus VAI RNA-negative mutant dl331 resulted in selective translation of influenza virus mRNAs and suppression of the elevated protein kinase levels normally found in cells infected by the mutant alone (M. G. Katze, B. M. Detjen, B. Safer, and R. M. Krug, Mol. Cell. Biol. 6:1741-1750, 1986). We elucidated the mechanisms of this kinase repression and can now report that influenza virus encodes a gene product which functions to directly block the autophosphorylation and activity of the interferon-induced, double-stranded-RNA-activated protein kinase, P68. Suppressed P68 activity was found not only in doubly infected cells but also in cells infected by influenza virus alone. Moreover, the decrease in P68 activity correlated with a decrease in the endogenous levels of phosphorylation of the alpha subunit of the eucaryotic initiation factor eIF-2, the natural substrate of the protein kinase. Suppression of P68 activity occurred as early as 2 h after influenza virus infection and required viral gene expression beyond the level of primary mRNA transcription to take place. We confirmed our in vivo observations with in vitro mixing experiments which showed that the influenza virus inhibitor can act in trans to block P68 activity. Combined repression of P68 function and eIF-2 alpha phosphorylation during influenza virus infection is essential for continued catalytic recycling of eIF-2 and efficient mRNA translation.
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PMID:Influenza virus regulates protein synthesis during infection by repressing autophosphorylation and activity of the cellular 68,000-Mr protein kinase. 341 83

PKR is a serine/threonine protein kinase induced by interferon treatment and activated by double-stranded RNAs. As a result of activation, PKR becomes autophosphorylated and catalyzes phosphorylation of the alpha subunit of protein synthesis eukaryotic initiation factor 2 (eIF-2). While studying the regulation of PKR in virus-infected cells, we found that a cellular 58-kDa protein (P58) was recruited by influenza virus to downregulate PKR and thus avoid the kinase's deleterious effects on viral protein synthesis and replication. We now report on the cloning, sequencing, expression, and structural analysis of the P58 PKR inhibitor, a 504-amino-acid hydrophilic protein. P58, expressed as a histidine fusion protein in Escherichia coli, blocked both the autophosphorylation of PKR and phosphorylation of the alpha subunit of eIF-2. Western blot (immunoblot) analysis showed that P58 is present not only in bovine cells but also in human, monkey, and mouse cells, suggesting the protein is highly conserved. Computer analysis revealed that P58 contains regions of homology to the DnaJ family of proteins and a much lesser degree of similarity to the PKR natural substrate, eIF-2 alpha. Finally, P58 contains nine tandemly arranged 34-amino-acid repeats, demonstrating that the PKR inhibitor is a member of the tetratricopeptide repeat family of proteins, the only member identified thus far with a known biochemical function.
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PMID:The 58,000-dalton cellular inhibitor of the interferon-induced double-stranded RNA-activated protein kinase (PKR) is a member of the tetratricopeptide repeat family of proteins. 751 Dec 4

The interferon-induced RNA-dependent protein kinase (PKR) is considered to play an important role in the cellular defense against viral infection and, in addition, has been suggested to be a tumor suppressor gene because of its growth-suppressive properties. Activation of PKR by double-stranded RNAs leads to the phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF-2 alpha) and a resultant block to protein synthesis initiation. To avoid the consequences of kinase activation, many viruses have developed strategies to down-regulate PKR. Recently, we reported on the purification and characterization of a cellular inhibitor of PKR (referred to as p58), which is activated during influenza virus infection. Subsequent cloning and sequencing has revealed that p58 is a member of the tetratricopeptide repeat (TPR) family of proteins. To further examine the physiological role of this PKR inhibitor, we stably transfected NIH 3T3 cells with a eukaryotic expression plasmid containing p58 cDNA under control of the cytomegalovirus early promoter. By taking advantage of a recently characterized p58 species-specific monoclonal antibody, we isolated cell lines that overexpressed p58. These cells exhibited a transformed phenotype, growing at faster rates and higher saturation densities and exhibiting anchorage-independent growth. Most importantly, inoculation of nude mice with p58-overexpressing cells gave rise to the production of tumors. Finally, murine PKR activity and endogenous levels of eIF-2 alpha phosphorylation were reduced in the p58-expressing cell lines compared with control cells. These data, taken together, suggest that p58 functions as an oncogene and that one mechanism by which the protein induces malignant transformation is through the down-regulation of PKR and subsequent deregulation of protein synthesis.
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PMID:The 58-kilodalton inhibitor of the interferon-induced double-stranded RNA-activated protein kinase is a tetratricopeptide repeat protein with oncogenic properties. 751 1

We previously demonstrated that influenza virus infection induces apoptosis in culture cells. Here, we examined the activation of the Fas antigen gene that encodes an apoptosis-mediating membrane protein in the virus-infected cells. The virus elicited a transient but marked increase in Fas antigen mRNA 3 to 4 hr after infection, followed by the expression of the antigen on the cell surface. Poly(I)-poly(C), a synthetic double-stranded RNA, similarly activated Fas antigen gene expression, and poly(I)-poly(C)-treated cells are highly susceptible to the cell killing effect of IgM isotype of anti-Fas monoclonal antibody. On the other hand, the IgG isotype of anti-Fas monoclonal antibody, which has an inhibitory effect on Fas Ag-mediated cell death, suppressed the virus-induced cell death. Prior exposure of the cells to anti-interferon-beta antibody decreased the degree of cell death as well as the amount of Fas mRNA. The autophosphorylation activity of double-stranded RNA-activated protein kinase was also decreased in the antibody-treated cells. Moreover, a protein kinase inhibitor, 2-aminopurine, blocked the Fas Ag gene activation by poly(I)-poly(C). These results suggested that the activation of Fas Ag gene in the early phase of infection is an important event for apoptosis, and that it is regulated by the double-stranded RNA/interferon system involving protein phosphorylation.
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PMID:Activation of the apoptotic Fas antigen-encoding gene upon influenza virus infection involving spontaneously produced beta-interferon. 753 67

Madin-Darby canine kidney and other epithelial cell lines (e.g. Caco-2, MCF-10A and MCF-7) develop intracellular vacuoles composed of apical membrane displaying microvilli (VACs) when impaired from forming normal cell-to-cell contacts. In a previous publication, we showed that VACs are rapidly exocytosed upon treatment with 8-Br-3',5'-cyclic adenosine monophosphate (8-Br-cAMP), a membrane-permeable analog of cAMP, and that this exocytosis correlates with variations in the cellular cAMP concentration in response to the cell-cell contacts. In the present work, we tested the hypothesis that cAMP may be a positive modulator of the 'constitutive' exocytic pathway. To mimic conditions in cells with incomplete intercellular contacts, the intracellular levels of cAMP were decreased by means of two independent approaches: (i) pores were induced in the plasma membrane with the polypeptidic antibiotic subtilin, thus allowing small molecules (including cAMP) to permeate and move out of the cytoplasm; and (ii) adenylate cyclase and protein kinase A were blocked with specific inhibitors. In all cases, the intracellular levels of cAMP were measured and, in porated cells, equilibrated to simulate the corresponding physiological intracellular concentrations. The decrease in cAMP within the physiological range resulted in a decreased rate of transport of an apical marker of the constitutive pathway (influenza virus hemagglutinin) from the trans-Golgi network to the apical plasma membrane. Likewise, the delivery of a number of cellular apical proteins to the plasma membrane was retarded at low cAMP concentrations. The inhibitors of adenylate cyclase failed to block basolateral delivery of vesicular stomatitis virus G protein. This differential modulatory effect may represent a differentiation-dependent control of the insertion of apical membrane in epithelial cells.
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PMID:Cyclic AMP modulates the rate of 'constitutive' exocytosis of apical membrane proteins in Madin-Darby canine kidney cells. 765 16

It was shown that human recombinant gamma IFN given to volunteers intramuscularly (90 x 10(3) IU) and by inhalation (120 x 10(3) IU) induced 5-10-fold increase circulating IFN (up to 40-60 IU/ml); the activities of 2,5-oligoadenylate synthetase increased 1.5-2 fold and protein kinase of lymphocytes--3-5-fold. The repeated doses of gamma IFN at 12-15-hour intervals maintained a relatively stable IFN status, the inhalatory route of application being more effective. Convalescents after influenza different from healthy donors by a higher level of serum interferon and activity of 2.5-oligoadenylate synthetase but the activity of protein kinase was lowered in lymphocytes and plasma. The side effects induced by IFN administration were more marked only after intramuscular injections of 90 10 IU and were absent after inhalation of IFN (120,000 IU).
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PMID:[Clinical trials of recombinant gamma-interferon. Circulating interferon and the 2,5-oligoadenylate synthetase activity after intramuscular and inhalation administrations]. 769 Jun 16


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