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)

In a proteomics-based screen for proteins interacting with cyclin-dependent protein kinase (CDK), we have identified a novel CDK complex containing the eukaryotic translation initiation factor, eIF4A. Reciprocal immunoprecipitations using antibodies against eIF4A indicate that the interaction is specific. The CDKA-eIF4A complex is abundant in actively proliferating and growing cells but is absent from cells that have ceased dividing. The CDKA-eIF4A complex contains kinase activity that is sensitive to the CDK-specific inhibitor roscovitine. This interaction points to a possible molecular mechanism linking cell proliferation with translational control.
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PMID:In vivo interaction between CDKA and eIF4A: a possible mechanism linking translation and cell proliferation. 1470 32

Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF2alpha) at serine 51 inhibits protein synthesis in cells subjected to various forms of stress including virus infection. The human papillomavirus (HPV) E6 oncoprotein contributes to virus-induced pathogenicity through multiple mechanisms including the inhibition of apoptosis and the blockade of interferon (IFN) action. We have investigated a possible functional relationship between the E6 oncoprotein and eIF2alpha phosphorylation by an inducible-dimerization form of the IFN-inducible protein kinase PKR. Herein, we demonstrate that HPV type 18 E6 protein synthesis is rapidly repressed upon eIF2alpha phosphorylation caused by the conditional activation of the kinase. The remainder of E6, however, can rescue cells from PKR-mediated inhibition of protein synthesis and induction of apoptosis. E6 physically associates with GADD34/PP1 holophosphatase complex, which mediates translational recovery, and facilitates eIF2alpha dephosphorylation. Inhibition of eIF2alpha phosphorylation by E6 mitigates eIF2alpha-dependent responses to transcription and translation of proapoptotic genes. These findings demonstrate, for the first time, a role of the oncogenic E6 in apoptotic signaling induced by PKR and eIF2alpha phosphorylation. The functional interaction between E6 and the eIF2alpha phosphorylation pathway may have important implications for HPV infection and associated pathogenesis.
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PMID:Control of alpha subunit of eukaryotic translation initiation factor 2 (eIF2 alpha) phosphorylation by the human papillomavirus type 18 E6 oncoprotein: implications for eIF2 alpha-dependent gene expression and cell death. 1506 Jan 62

UV light induces a delayed and prolonged (3-20 h) activation of NFkappaB when compared with the immediate and acute (10-90 min) activation of NFkappaB in response to tumor necrosis factor alpha treatment. In the early phase (3-12 h) of NFkappaB activation, UV light reduces inhibitor of NFkappaB (IkappaB) through an IkappaB kinase-independent, but polyubiquitin-dependent, pathway. However, the mechanism for the UV light-induced reduction of IkappaB and activation of NFkappaB is not known. In this report, we show that UV light down-regulates the total amount of IkappaB through decreasing IkappaB mRNA translation. Our data show that UV light inhibits translation of IkappaB in wild-type mouse embryo fibroblasts (MEF(S/S)) and that this inhibition is prevented in MEF(A/A) cells in which the phosphorylation site, Ser-51 in the eukaryotic translation initiation factor 2 alpha-subunit, is replaced with a non-phosphorylatable Ala (S51A). Our data also show that UV light-induced NFkappaB activation is delayed in MEF(A/A) cells and in an MCF-7 cell line that is stably transfected with a trans-dominant negative mutant protein kinase-like endoplasmic reticulum kinase (PERK). These results suggest that UV light-induced eukaryotic translation initiation factor 2 alpha-subunit phosphorylation translationally inhibits new IkappaB synthesis. Without a continuous supply of newly synthesized IkappaB, the existing IkappaB is degraded through a polyubiquitin-dependent proteasomal pathway leading to NFkappaB activation. Based upon our results, we propose a novel mechanism by which UV light regulates early phase NFkappaB activation by means of an ER-stress-induced translational inhibition pathway.
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PMID:Ultraviolet light activates NFkappaB through translational inhibition of IkappaBalpha synthesis. 1518 76

Phosphorylation of the alpha (alpha) subunit of the eukaryotic translation initiation factor 2 (eIF2) leads to the inhibition of protein synthesis in response to diverse stress conditions, including viral infection. The eIF2alpha kinase PKR has been shown to play an essential role against vesicular stomatitis virus (VSV) infection. We demonstrate here that another eIF2alpha kinase, the endoplasmic reticulum-resident protein kinase PERK, contributes to cellular resistance to VSV infection. We demonstrate that mouse embryonic fibroblasts (MEFs) from PERK(-/-) mice are more susceptible to VSV-mediated apoptosis than PERK(+/+) MEFs. The higher replication capacity of VSV in PERK(-/-) MEFs results from their inability to attenuate viral protein synthesis due to an impaired eIF2alpha phosphorylation. We also show that VSV-infected PERK(-/-) MEFs are unable to fully activate PKR, suggesting a cross talk between the two eIF2alpha kinases in virus-infected cells. These findings further implicate PERK in virus infection, and provide evidence that the antiviral and antiapoptotic roles of PERK are mediated, at least in part, via the activation of PKR.
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PMID:Resistance to vesicular stomatitis virus infection requires a functional cross talk between the eukaryotic translation initiation factor 2alpha kinases PERK and PKR. 1554 27

Double-stranded RNA-dependent protein kinase (PKR) is a participant in the cellular antiviral response and phosphorylates the alpha-subunit of eukaryotic translation initiation factor 2alpha (eIF-2alpha) to block protein synthesis. Treatment of human osteosarcoma cell line MG63 cells with a serine and threonine protein phosphatase inhibitor, okadaic acid, at the concentration of 100 nM, but not at 20 nM, induced apoptosis. To investigate the functional relationship between phosphatases and apoptosis, we examined the phosphorylation levels of PKR and eIF-2alpha by Western blot analysis. During treatment of cells with it at the higher concentration (100 nM), okadaic acid increased the level of phosphorylated PKR in MG63 cells, this kinase phosphorylating eIF-2alpha. However, at the lower concentration (20 nM), okadaic acid did not affect the level of phosphorylated PKR. In the cells treated with 100 nM okadaic acid, activation of NF-kappaB also occurred. Even though inhibition of translation occurred simultaneously in MG63 cells, the expression of pro-apoptotic proteins Fas and Bax was not affected by 100 nM okadaic acid in these cells. We concluded that the inhibition of translation decreased anti-apoptotic protein expression, thus resulting in apoptosis. Our results also suggest that the inhibition of the protein phosphatase activity by okadaic acid induced apoptosis in MG63 cells through PKR and eIF-2alpha.
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PMID:Okadaic acid induces apoptosis through double-stranded RNA-dependent protein kinase/eukaryotic initiation factor-2alpha pathway in human osteoblastic MG63 cells. 1562 11

Cell death is an intrinsic part of metazoan development and mammalian immune regulation. Whereas the molecular events orchestrating apoptosis have been characterized extensively, little is known about the biochemistry of necrotic cell death. Here, we show that, in contrast to apoptosis, the induction of necrosis does not lead to the shut down of protein synthesis. The rapid drop in protein synthesis observed in apoptosis correlates with caspase-dependent breakdown of eukaryotic translation initiation factor (eIF) 4G, activation of the double-stranded RNA-activated protein kinase PKR, and phosphorylation of its substrate eIF2-alpha. In necrosis induced by tumor necrosis factor, double-stranded RNA, or viral infection, de novo protein synthesis persists and 28S ribosomal RNA fragmentation, eIF2-alpha phosphorylation, and proteolytic activation of PKR are absent. Collectively, these results show that, in contrast to apoptotic cells, necrotic dying cells retain the opportunity to synthesize proteins.
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PMID:Protein synthesis persists during necrotic cell death. 1569 14

The protein kinase GCN2 mediates translational control of gene expression in amino acid-starved cells by phosphorylating eukaryotic translation initiation factor 2alpha. In Saccharomyces cerevisiae, activation of GCN2 by uncharged tRNAs in starved cells requires its direct interaction with both the GCN1.GCN20 regulatory complex and ribosomes. GCN1 also interacts with ribosomes in cell extracts, but it was unknown whether this activity is crucial for its ability to stimulate GCN2 function in starved cells. We describe point mutations in two conserved, noncontiguous segments of GCN1 that lead to reduced polyribosome association by GCN1.GCN20 in living cells without reducing GCN1 expression or its interaction with GCN20. Mutating both segments simultaneously produced a greater reduction in polyribosome binding by GCN1.GCN20 and a stronger decrease in eukaryotic translation initiation factor 2alpha phosphorylation than did mutating in one segment alone. These findings provide strong evidence that ribosome binding by GCN1 is required for its role as a positive regulator of GCN2. A particular mutation in the GCN1 domain, related in sequence to translation elongation factor 3 (eEF3), decreased GCN2 activation much more than it reduced ribosome binding by GCN1. Hence, the eEF3-like domain appears to have an effector function in GCN2 activation. This conclusion supports the model that an eEF3-related activity of GCN1 influences occupancy of the ribosomal decoding site by uncharged tRNA in starved cells.
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PMID:Polyribosome binding by GCN1 is required for full activation of eukaryotic translation initiation factor 2{alpha} kinase GCN2 during amino acid starvation. 1572 45

C5b-9-induced glomerular epithelial cell (GEC) injury in vivo (in passive Heymann nephritis) and in culture is associated with damage to the endoplasmic reticulum (ER) and increased expression of ER stress proteins. Induction of ER stress proteins is enhanced via cytosolic phospholipase A(2) (cPLA(2)) and limits complement-dependent cytotoxicity. The present study addresses another aspect of the ER unfolded protein response, i.e. activation of protein kinase R-like ER kinase (PERK or pancreatic ER kinase), which phosphorylates eukaryotic translation initiation factor 2-alpha (eIF2alpha), thereby generally suppressing translation and decreasing the protein load on a damaged ER. Phosphorylation of eIF2alpha was enhanced significantly in glomeruli of proteinuric rats with passive Heymann nephritis, compared with control. In cultured GECs, complement induced phosphorylation of eIF2alpha and reduced protein synthesis, and complement-stimulated phosphorylation of eIF2alpha was enhanced by overexpression of cPLA(2). Ischemia-reperfusion in vitro (deoxyglucose plus antimycin A followed by glucose re-exposure) also stimulated eIF2alpha phosphorylation and reduced protein synthesis. Complement and ischemia-reperfusion induced phosphorylation of PERK (which correlates with activation), and fibroblasts from PERK knock-out mice were more susceptible to complement- and ischemia-reperfusion-mediated cytotoxicity, as compared with wild type fibroblasts. The GEC protein, nephrin, plays a key role in maintaining glomerular permselectivity. In contrast to a general reduction in protein synthesis, translation regulated by the 5'-end of mouse nephrin mRNA during ER stress was paradoxically maintained, probably due to the presence of short open reading frames in this mRNA segment. Thus, phosphorylation of eIF2alpha and consequent general reduction in protein synthesis may be a novel mechanism for limiting complement- or ischemia-reperfusion-dependent GEC injury.
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PMID:Role of the endoplasmic reticulum unfolded protein response in glomerular epithelial cell injury. 1586 8

Insulin resistance may be modeled in H-411E liver cells in tissue culture with the use of the cytokine tumor necrosis factor-alpha (TNF-alpha) and insulin. This tissue-culture model nicely mimics IR in human type 2 diabetes mellitus. After incubation of liver cells in tissue culture with INS alone, TNF-alpha alone, and TNF-alpha plus insulin, as well as a control sample, liver-cell extracts were separated on 2D polyacrylamide-gel electrophoresis on the basis of isoelectric point and molecular weight. We analyzed the gel images with the use of PD Quest software (Bio-Rad Laboratories, Hercules, Calif) to identify differentially expressed protein spots (ie, up or down with insulin vs down or up with TNF-alpha plus insulin). In separate experiments, phosphorus-32 incorporation/autoradiography and phosphoprotein staining were used to characterize treatment-induced phosphorylations. Affected protein spots were identified with the use of peptide fingerprinting and matrix-assisted laser desorption ionization time of flight mass spectrometry. The first series of experiments identified 6 differentially expressed proteins: eukaryotic translation initiation factor-3, subunit 2, regulator of G-protein signaling-5, superoxide dismutase, protein disulfide isomerase A6, proteasome subunit-alpha type 3, and regucalcin. In addition, we observed changes in the phosphorylation of protein disulfide isomerase A6. A second series of experiments identified 7 additional proteins with significantly altered differential expression: cell-division protein kinase-4, kinogen heavy chain, carbonic anhydrase-7, E 3 ubiquitin protein ligase, URE-B1; Rab GDP dissociation inhibitor-beta, Rab GDP dissociation inhibitor-beta2, and MAWDBP. It can be seen that differentially expressed proteins, affected by treatment with insulin or with TNF-alpha plus insulin, include regulators of translation, protein degradation, cellular Ca ++ , G-proteins, and free-radical production. Although one cannot detail the mechanism or mechanisms of TNF-alpha induced IR from this data alone, it is easy to relate all of these proteins to a role in insulin signal transduction and, hence, insulin resistance.
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PMID:Proteome of H-411E (liver) cells exposed to insulin and tumor necrosis factor-alpha: analysis of proteins involved in insulin resistance. 1590 99

Dendritic cells (DCs) are central to T cell immunity, and many strategies have been used to manipulate DCs to modify immune responses. We investigated the effects of antioxidants ascorbate (vitamin C) and alpha-tocopherol (vitamin E) on DC phenotype and function. Vitamins C and E are both antioxidants, and concurrent use results in a nonadditive activity. We have demonstrated that DC treated with these antioxidants are resistant to phenotypic and functional changes following stimulation with proinflammatory cytokines. Following treatment, the levels of intracellular oxygen radical species were reduced, and the protein kinase RNA-regulated, eukaryotic translation initiation factor 2alpha, NF-kappaB, protein kinase C, and p38 MAPK pathways could not be activated following inflammatory agent stimulation. We went on to show that allogeneic T cells (including CD4(+)CD45RO, CD4(+)CD45RA, and CD4(+)CD25(-) subsets) were anergized following exposure to vitamin-treated DCs, and secreted higher levels of Th2 cytokines and IL-10 than cells incubated with control DCs. These anergic T cells act as regulatory T cells in a contact-dependent manner that is not dependent on IL-4, IL-5, IL-10, IL-13, and TGF-beta. These data indicate that vitamin C- and E-treated DC might be useful for the induction of tolerance to allo- or autoantigens.
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PMID:Inhibition of NF-kappa B and oxidative pathways in human dendritic cells by antioxidative vitamins generates regulatory T cells. 1594 64


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