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:2.7.10.1 (ERK)
95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biological effects of staphylococcal enterotoxins (SE), potentiated by bacterial lipopolysaccharide (LPS), were studied with mice. Control animals survived the maximum dose of either SE or LPS, while mice receiving both agents died. SEA was 43-fold more potent than SEB and 20-fold more potent than SEC1. The mechanism of toxicity was further examined with transgenic mice deficient in major histocompatibility complex class I or II expression. Class II-deficient mice were resistant to SEA or SEB. However, class I-deficient animals were less susceptible to SEA (30% lethality) than wild-type mice (93% lethality). In vitro stimulation of T cells from the three mouse phenotypes by SEA correlated well with toxicity. T cells from transgenic or wild-type mice were similarly responsive to SEA when presented by irradiated, wild-type mononuclear cells. These data confirmed that the toxicity of SE was mainly exerted through a mechanism dependent on the expression of major histocompatibility complex class II molecules. Toxicity was also linked to stimulated cytokine release. Levels in serum of tumor necrosis factor alpha, interleukin-6, and gamma interferon peaked 2 to 4 h after the potentiating dose of LPS but returned to normal within 10 h. Concentrations of interleukin-1 alpha were also maximal after 2 h but remained above the background for up to 22 h. Relative to the levels in mice given only SEA or LPS, the levels in serum of tumor necrosis factor alpha, interleukin-6, and gamma interferon increased 5-, 10-, and 15-fold, respectively, after injections of SEA plus LPS. There was only an additive effect of SEA and LPS on interleukin-1 alpha concentrations.
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PMID:Toxicity of staphylococcal enterotoxins potentiated by lipopolysaccharide: major histocompatibility complex class II molecule dependency and cytokine release. 822 6

Bacterial LPS induce production of cytokines such as IL-1, IL-6, and TNF in mononuclear phagocytes, and this represents a central component in the pathogenesis of septic shock syndrome. However, the mechanisms by which LPS activates these cells to express cytokines are not completely characterized. The present study addressed the role of different protein kinases in the LPS induction of cytokines. It is shown that LPS induced a 12- to 16-fold increase in IL-1 beta, IL-6, and TNF-alpha mRNA levels, and this was completely or more than 80% blocked by the protein tyrosine kinase specific inhibitors herbimycin A and genistein at the concentrations of 1.7 and 37 microM, respectively. Protein kinase C inhibition by staurosporine reduced LPS induction of TNF-alpha, whereas it had no effects on IL-6 and IL-1 beta. Inhibition of protein kinase A by H89 reduced IL-6 mRNA levels but did not detectably change IL-1 beta or TNF-alpha mRNA levels. In contrast, LPS did not increase leukemia inhibitory factor mRNA, which was constitutively expressed and not significantly reduced by these inhibitors. In addition to cytokine mRNA levels, LPS-induced IL-6 protein synthesis and IL-6 bioactivity were also reduced to baseline levels by the PTK inhibitors herbimycin A and genistein. Both PTK inhibitors also reduced the LPS activation of nuclear factor-kappa B (NF-kappa B), which is a transcription factor involved in the expression of cytokine genes such as IL-6 and TNF-alpha. The activation of NF-kappa B was also reduced by H89, whereas staurosporine had no effect on this response. In summary, these findings suggest that protein kinase C and protein kinase A appear to have selective effects in the LPS induction of cytokines, whereas PTK is required for LPS induction of a broad spectrum of cytokines and NF-kappa B activation in monocytes.
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PMID:Protein tyrosine kinase activation is required for lipopolysaccharide induction of cytokines in human blood monocytes. 825 85

CD8-positive cytotoxic T cells (CTLs) are activated by recognition of peptide bound to MHC class I molecules on target cells. This human leukocyte antigen-restricted process induces not only lysis of target cells but also secretion of lymphokines by the CTLs, including TNF-alpha, TNF-beta, and IFN-gamma. In this study we show that activation of HIV-1-specific CTL clones by their cognate peptide epitopes induces HIV-1 replication in the chronically HIV-1-infected T-cell line ACH-2. The HIV-1-inducing activity correlates with increased levels of TNF-alpha produced by these CTLs, and can be inhibited by anti-TNF-alpha antibodies, indicating that the effect is mediated by this cytokine. These studies suggest that activation of CTL in vivo could lead to enhanced viral replication. Although HIV-1-specific CTLs may serve as a host defense to inhibit virus replication, the induction of TNF-alpha production by these cells may facilitate viral replication in infected bystander cells, contributing to viral persistence and disease pathogenesis.
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PMID:Induction of HIV-1 replication in a chronically infected T-cell line by cytotoxic T lymphocytes. 831 73

Thalidomide, a selective inhibitor of tumor necrosis factor alpha (TNF-alpha) synthesis, suppresses the activation of latent human immunodeficiency virus type 1 (HIV-1) in a monocytoid (U1) line. The inhibition is dose dependent and occurs after exposure of the cells to recombinant TNF-alpha, phorbol myristate acetate, lipopolysaccharide, and other cytokine combinations. Associated with HIV-1 inhibition is a reduction in agonist-induced TNF-alpha protein and mRNA production. Thalidomide inhibition of virus replication in the phorbol myristate acetate- and recombinant TNF-alpha-stimulated T-cell line ACH-2 is not observed. The presence of thalidomide also inhibits the activation of virus in the peripheral blood mononuclear cells of 16 out of 17 patients with advanced HIV-1 infection and AIDS. These results suggest the use of thalidomide in a clinical setting to inhibit both virus replication and the TNF-alpha-induced systemic toxicity of HIV-1 and opportunistic infections.
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PMID:Thalidomide inhibits the replication of human immunodeficiency virus type 1. 832 69

Hepatocyte growth factor/scatter factor (HGF-SF), a multifunctional cytokine, is the ligand for the met receptor tyrosine kinase. Multiple met mRNAs of 8, 7, 5, 3 and 1.6-kb in size have been identified in human cell lines and tissue. To investigate the biological function of these various isoforms we have isolated cDNA clones corresponding to some of the differentially spliced met mRNAs. Characterization of these cDNAs suggests that by alternative splicing and possibly by use of distinct transcription initiation sites the met HGF-SF receptor is expressed in various isoforms. We have demonstrated that there are two met 8-kb mRNAs that differ through alternative splicing of a 54-bp exon that maintains the open reading frame such that these proteins differ by only 18 aa in their extracellular domain. The -54-bp form corresponds to the most abundant 8-kb met RNA and encodes the p190 met alpha beta heterodimer. In contrast the +54-bp mRNA encodes a protein of 170 kd that is not cleaved yet is expressed at the cell surface and has in vitro kinase activity. The 7-kb mRNA differs by alternative splicing such that it encodes a protein with a distinct amino terminus. Unlike these met RNAs, the 1.6-kb mRNA has new 5' and 3' sequences and encodes a protein that shares homology with the extracellular domain of the met RTK but has a unique carboxy terminus. Thus multiple met RNAs encode proteins that differ in both the extracellular ligand binding domain and within the cytoplasmic domain suggesting that these different met isoforms may have distinct biological activities.
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PMID:Isoforms of the met receptor tyrosine kinase. 838 Jul 36

Protein-tyrosine kinases (PTKs) of the JAK family have been characterized on the basis of their ability to mediate the rapid induction of transcription of interferon-responsive genes through the stimulation of a class of latent cytoplasmic transcription factors known as signal transducers and activators of transcription (STATs). STAT activation, which has been described as being Ras-independent, requires tyrosine phosphorylation, but STAT transactivating activity is enhanced by phosphorylation on serine as well, probably by extracellular signal-regulated kinase/mitogen-activated protein kinase(s) (ERK/MAPK). STATs can be activated upon binding of ligands to receptor PTKs, to G-protein-linked receptors, and to cytokine receptors. Whether JAKs are required for the activation of signaling pathways other than that leading to STAT activation is not known. The binding of growth hormone (GH) to its receptor (GHR) activates JAK2 and STATs as well as ERK/MAP kinases. We have used a transient transfection system in 293 cells to evaluate the requirement for JAK2 in the activation of ERK2/MAPK by GH. We found that JAK2 is required for GH-simulated activation of ERK2/MAPK. Employing the transient expression of dominant negative forms of H-Ras and Raf-1, we determined that the GHR/JAK2-mediated activation of ERK2/MAPK is dependent on both Ras and Raf. Thus, JAK protein-tyrosine kinases may represent a common component in the activation of the ERK2/MAPK and STAT signaling pathways, which appear to bifurcate upstream of Ras activation but converge with ERK/MAPK phosphorylation of STATs.
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PMID:JAK2, Ras, and Raf are required for activation of extracellular signal-regulated kinase/mitogen-activated protein kinase by growth hormone. 853 33

Epidermal growth factor is a potential mitogen for many different human tumours. Its effect is mediated via a bispecific receptor (EGFR), the expression of which correlates well with invasive disease. We investigated the modulation of EGFR by cytokines produced following bacillus Calmette Guerin (BCG)-immunotherapy. Our data demonstrate the IFN gamma, TNF alpha and IL-1 alpha can decrease the expression of EGFR on some bladder tumour cell lines. IFN gamma reduced EGFR expression on two of eight cell lines (RT4, SD). However, IL-1 and TNF did not share this activity. When cells were treated with a combination of all three cytokines, EGFR was decreased on three cell lines (RT4, RT112, SD) and furthermore, the change in the receptor expression was even more marked. Treatment with phorbol ester (thereby activating protein kinase C) resulted in rapid disappearance of the receptor from the cell surface. Interestingly, the decrease of EGFR expression did not require protein synthesis. Although the cytokines studied could down modulate EGFR, this only occurred on three out of eight cell lines; therefore, it is unlikely that the suppression of proliferative activity caused by cytokine-induced decrease of EGFR expression is central to the antitumour action of BCG therapy, but in a proportion of tumours this mechanism may be involved.
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PMID:Cytokine modulation of epidermal growth factor receptor expression on bladder cancer cells is not a major contributor to the antitumour activity of cytokines. 856 66

Kaposi's sarcoma is a highly vascularized multifocal tumor which frequently appears as a complication of HIV infection. It has been suggested that a disorder in the cytokine network may contribute to the development of the disease. We examined the expression of several cytokines in human sporadic Kaposi's-sarcoma specimens, as well as in spindle cells cultured from human lesions, and consistently found high levels of expression of hepatocyte growth factor (HGF). In addition, human lesion-derived spindle cells synthesize and secrete biologically active hepatocyte growth factor and express the hepatocyte-growth-factor receptor (c-MET). Moreover, elevated levels of transforming growth factor beta 1 (TGF beta 1) mRNA were found in lesions of human sporadic Kaposi's sarcoma and in lesion-derived spindle cells which also over-express urokinase. Since HGF, TGF beta 1 and urokinase are all involved in capillary-vessel organization, dysregulation of these interacting agents may play a role in the initiation and/or progression of Kaposi's sarcoma, stimulating the growth of spindle cells and recruiting endothelial cells into the lesion.
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PMID:Over-expression of hepatocyte growth factor in human Kaposi's sarcoma. 856 12

Recombinant human tumor necrosis factor (TNF) binding protein-1 (r-h TBP-1) and recombinant human soluble dimeric TNF receptor (rhu TNFR:Fc) were used to determine the relative contributions of TNF to phorbol myristate acetate (PMA) and cytokine-induced human immunodeficiency virus type 1 (HIV-1) replication in chronically infected cell lines. Treatment of HIV-1-infected promonocytic U1 cells with r-h-TBP-1 or rhu TNFR:Fc reduced PMA-induced HIV-1 p24 antigen production in a concentration-dependent manner, with a maximal inhibition of approximately 90%. Maximal inhibition of p24 antigen production in T-lymphocytic ACH-2 cells was 47% with r-hTBP-1 and 42% with rhu TNFR:Fc. r-hTBP-1 and rhu TNFR:Fc also decreased p24 antigen synthesized by U1 cells in response to other stimuli, including phytohemagglutinin (PHA)-induced supernatant, granulocyte-macrophage colony-stimulating factor, interleukin-6, and TNF. Addition of r-hTBP-1 to U1 cells during the last 4 h of a 24 h incubation with PMA still inhibited p24 antigen production by 15%. U1 cells stimulated with 10(-7) M PMA released approximately 1 ng/ml endogenous TBP-1 with an initial peak observed at 1 h and a second peak at 24 h after PMA stimulation. r-hTBP-1 also partially reversed inhibition of U1 cellular proliferation caused by PMA. Both r-hTBP-1 and rhu TNFR:Fc blocked PMA induction of nuclear factor (NK)- kappa B DNA-binding activity in U1 cells in association with decreases in HIV-1 replication. We conclude that soluble TNF receptors can inhibit stimuli-induced HIV-1 expression and NK- kappa B DNA-binding activity in chronically infected U1 cells.
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PMID:Soluble tumor necrosis factor receptors inhibit phorbol myristate acetate and cytokine-induced HIV-1 expression chronically infected U1 cells. 860 87

We observed that human megakaryocytes expressed the heterodimeric tyrosine kinase RON, which serves as a receptor for macrophage-stimulating protein (MSP). MSP appears to be structurally related to hepatocyte growth factor (HGF), which is a pleiotropic growth factor for a broad spectrum of tissues and cell types. The effects of human rMSP and rHGF on permanent human megakaryocytic cell lines as well as on human and murine primary marrow megakaryocytes were studied. MSP enhanced the maturation of the primary bone marrow megakaryocytes and human megakaryocytic cell lines, CMK and DAMI, as assessed by an increase in ploidy content. The increase in ploidy was blocked by specific Abs for MSP and by anti-IL-6 Abs. MSP treatment of primary human marrow megakaryocytes, DAMI cells, or CMK cells resulted in enhanced secretion of IL-6. The addition of MSP to cultures of immature murine megakaryoblasts showed a significant growth response, similar to that of exogenous IL-6. This increased growth of immature murine megakaryoblasts in response to MSP was abrogated either by Abs against MSP or by neutralizing mAbs to IL-6. HGF, over a range of concentrations (10 to 100 ng/ml) alone or in combination with IL-3, granulocyte-macrophage-CSF, or IL-6, had no effect on differentiation of human or murine marrow megakaryocytes. These results indicate that megakaryocytes express a novel tyrosine kinase receptor (RON), and that its ligand, MSP, appears capable of regulating megakaryocyte maturation, possibly via an autocrine mechanism mediated by induction of the cytokine IL-6.
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PMID:Modulation of megakaryocytopoiesis by human macrophage-stimulating protein, the ligand for the RON receptor. 860 14


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