Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tumour necrosis factor (TNF) is a potent mitogen for some fibroblast cell lines. Here we have examined the TNF-mediated changes in protein phosphorylation in Swiss 3T3 and human FS-4 fibroblasts, and compared them with changes observed after the treatment of cells with other mitogens, such as platelet-derived growth factor (PDGF) and bombesin. TNF stimulated the rapid phosphorylation of two 41,000-Mr and two 43,000-Mr cytosol proteins on tyrosine, threonine and/or serine, as did PDGF, epidermal growth factor and fibroblast growth factor; the increased levels of this mitogen-induced protein-tyrosine phosphorylation correlated well with the extent of mitogen-induced DNA synthesis as determined by the percentage of labelled nuclei. In contrast, bombesin, which is an even better mitogen for Swiss 3T3 cells than TNF, stimulated the tyrosine phosphorylation of 41,000-Mr and 43,000-Mr proteins only to a limited extent. On the other hand, bombesin and PDGF stimulated the rapid serine phosphorylation of an 80,000-Mr acidic protein, a major substrate for protein kinase C; increased phosphorylation of the 80,000-Mr protein was not observed at all when cells were stimulated with TNF. These results suggest significant differences among the mitogenic signalling pathways of TNF, PDGF and bombesin as regards the involvement of protein kinases; the mitogenic signalling pathway of TNF involves the activation of tyrosine kinase, but not of protein kinase C, whereas bombesin seems to transduce its mitogenic signal mainly through the activation of protein kinase C, and the activation of both kinases seems to be involved in the mitogenic signalling pathway of PDGF.
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PMID:Mitogenic signalling pathway of tumour necrosis factor involves the rapid tyrosine phosphorylation of 41,000-Mr and 43,000-Mr cytosol proteins. 169 38

Tumour necrosis factor (TNF) and related cytokines have been found to alter the phenotype of vascular endothelial cells so as to promote coagulation, inflammation and immunity. We have used recombinant human TNF, lymphotoxin (LT), interleukin 1 alpha (IL-1 alpha) and interleukin 1 beta (IL-1 beta) to study and compare the effects of these molecules on cultured human endothelial cells (HEC). All four mediators cause HEC monolayers to reorganize from an epithelioid to a fibroblastoid morphology. Reorganization is slow (days), reversible upon cytokine withdrawal and enhanced by co-addition of immune interferon. Coincident with morphological change, TNF and LT (but not IL-1 alpha or IL-1 beta) cause a marked increase in HLA-A, B mRNA and antigen expression. TNF and LT also induce a slow increase in the mRNA levels and cell-surface expression of IL-1 species. All four cytokines have been reported to enhance HEC adhesiveness for lymphocytes and inflammatory leucocytes; these changes temporally coincide with a rapid (hours) and sustained increase in expression of intercellular adhesion molecule 1 (ICAM-1), and with a rapid but transient de novo expression of an endothelial-leucocyte adhesion molecule (detected by antibody H4/18), respectively. TNF and LT induce reciprocal tachyphylaxis for the reinduction of H4/18 binding but do not inhibit induction by IL-1 alpha and IL-1 beta; similarly, IL-1 alpha and IL-1 beta induce reciprocal tachyphylaxis but do not inhibit TNF or LT. We have used the binding of H4/18 to explore the mechanism of action of TNF. Tumour-promoting phorbol esters, but not agents which increase cytoplasmic calcium concentrations, were found to induce binding, suggesting a possible involvement of the protein kinase C pathway in the response of HEC to TNF. Cells pretreated for 24 hours with phorbol esters cannot be reinduced to express H4/18 binding by phorbol esters yet retain full responsiveness to TNF. Thus TNF also appears to act on HEC through a pathway independent of protein kinase C activation. Collectively, these effects of TNF and related cytokines may be understood as examples of endothelial cell activation.
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PMID:Effects of tumour necrosis factor and related cytokines on vascular endothelial cells. 333 9

Tumour necrosis factor (TNF) plays a pivotal role in the induction of cerebral complications during Plasmodium falciparum malaria. TNF secretion by macrophages can be induced by lipopolysaccharide (LPS) and by P. falciparum antigens, but it is unclear whether similar mechanisms control the monokine expression in both cases. The signal transduction pathway by which parasite antigens induce TNF secretion remains to be established. The results reported here, using various inhibitors of second messenger pathways, clearly demonstrate that the signal transduction leading to TNF secretion is mediated partly through protein kinase C and calmodulin-dependent protein kinase activation. Furthermore, this signal seems to be differentially regulated after LPS or parasite stimulation, since cyclo-oxygenase inhibition by indomethacin resulted in twofold more TNF production enhancement with LPS stimulation than with parasite stimulation. The nature of the receptor involved in the parasite induced-macrophage stimulation remains obscure. However, the results discussed here indicate that parasite antigens stimulate multiple signal transduction pathways via G protein. Identification of the different pathways involved in these receptor-mediated events may be invaluable in the development of specific inhibitors against TNF over-production during cerebral malaria.
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PMID:Signal transduction pathways involved in tumour necrosis factor secretion by Plasmodium falciparum-stimulated human monocytes. 782 69

Malignant B lymphocytes from patients with B-chronic lymphocytic leukaemia (B-CLL) or hairy cell leukemia (HCL) are refractory in vitro to mitogenic stimulation by several agents which trigger proliferation of normal B cells. Tumour necrosis factor (TNF) is a growth factor for these malignant cells, although the proliferative response is usually small. TNF regulates some of its cellular responses via induction of the transcription factors NF kappa B and AP-1 (jun/fos). The induction of NF kappa B by TNF is mediated via a novel signalling pathway involving the generation of reactive oxidative intermediates. Induction of jun and fos proteins (polypeptide components of AP-1) are mediated via pathways involving protein kinase C and the protein kinase encoded by the raf proto-oncogene. Here we have used an electrophoretic mobility shift assay to show that TNF induced NF kappa B in malignant cells isolated from 3/3 HCL and 15/15 B-CLL patients. By contrast, phorbol myristate acetate (PMA), a direct activator of protein kinase C, failed to activate this transcription factor in 1/1 HCL and 5/5 B-CLL isolates. The induction of jun and fos proteins (as detected by Western blot analysis) showed greater heterogeneity. Nuclear jun was induced by TNF in 5/12 chronic B cell leukaemia isolates. PMA induced this protein in 4/5 samples. Nuclear fos was induced by TNF in only 2/12 isolates and by PMA in 2/5. The data suggest that the pathways for the activation of jun and fos by TNF are defective in some B-CLL and HCL cells and that these defects may be heterogeneous. The induction of AP-1 is crucial in securing the mitogenic response to TNF. It is therefore plausible that these lesions may contribute to the refractory nature of B-CLL and HCL cells to proliferative stimuli in vitro.
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PMID:Regulation of transcription factors NF kappa B and AP-1 following tumour necrosis factor-alpha treatment of cells from chronic B cell leukaemia patients. 804 32

Thrombomodulin (TM) is expressed on vascular endothelial cells and plays an important role in the anticoagulant pathway by maintaining the thrombo-resistance of the blood vessel wall. We show that in primary human endothelial cells TM gene expression is repressed at the transcriptional level by Tumour necrosis factor (TNF alpha) through a protein kinase C independent pathway. The TM promoter is highly active in endothelial cells and is inhibited by TNF alpha. The -76/-56 region mediates both specific high basal activity and TNF alpha-repression. It binds a nuclear factor specific to endothelial cells, that appears to belong to the Ets-family by various criteria. The -76/-56 region contains three direct repeats of the ets-core sequence GGAA that are important for specific high basal activity, TNF alpha repression and trans-activation by expression of Ets-1 and 2. Although human Ets-1 (h-Ets-1) and chicken c-Ets-1 and 2 stimulate the TM promoter through the -76/-56 element, their activity is not suppressed by TNF alpha. c-Ets-1 competes and overrides TNF alpha repression in a concentration dependent manner. We propose that either a different member of the Ets domain protein family, or an Ets-associated co-factor, is the target of the TNF alpha signalling cascade in endothelial cells.
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PMID:Ets transcription factor binding site is required for positive and TNF alpha-induced negative promoter regulation. 828 9

Photodynamic therapy (PDT) is currently under investigation in phase II and III clinical studies for the treatment of tumours in superficial localisations. Thus far, the underlying mechanisms of PDT regarding cellular responses and gene regulation are poorly understood. Photochemically generated singlet oxygen (1O2) is mainly responsible for cytotoxicity induced by PDT. If targeted cells are not disintegrated, photo-oxidative stress leads to transcription and translation of various stress response and cytokine genes. Tumour necrosis factor (TNF) alpha, interleukin (IL) 1 and IL-6 are strongly induced by photodynamic treatment, supporting inflammatory action and immunological anti-tumour responses. To investigate the first steps of gene activation, this study focused on the proto-oncogenes c-jun and c-fos, both coding for the transcription factor activator protein 1 (AP-1), which was found to mediate IL-6 gene expression. We here determine the effects of photodynamic treatment on transcriptional regulation and DNA binding of transcription factor AP-1 in order to understand the modulation of subsequent regulatory steps. Photodynamic treatment of epithelial HeLa cells was performed by incubation with Photofrin and illumination with 630 nm laser light in vitro. Expression of the c-jun and c-fos genes was determined by way of Northern blot analysis, and DNA-binding activity of the transcription factor AP-1 was evaluated by electrophoretic mobility shift assay (EMSA). Photofrin-mediated photosensitisation of HeLa cells resulted in a rapid and dose-dependent induction of both genes but preferential expression of c-jun. Compared with the transient expression of c-jun and c-fos by phorbol ester stimulation, photodynamic treatment led to a prolonged activation pattern of both immediate early genes. Furthermore, mRNA stability studies revealed an increased half-life of c-jun and c-fos transcripts resulting from photosensitisation. Although mRNA accumulation after PDT was stronger and more prolonged compared with phorbol ester stimulation, with regard to AP-1 DNA-binding activity, phorbol ester was more efficient. Surprisingly, in addition to the activation of AP-1 DNA-binding via PDT, photodynamic treatment can decrease AP-1 DNA-binding of other strong inducers, such as the protein kinase C-mediated pathway of phorbol esters and the antioxidant pyrrolidine dithiocarbamate (PDTC). This study demonstrates a strong induction of c-jun and c-fos expression by PDT, with prolonged kinetics and mRNA stabilisation as compared with activation by phorbol esters. Interestingly, this observation is not coincident with an overinduction of AP-1 DNA-binding, hence suggesting that post-translational modifications are dominant regulatory mechanisms after PDT that tightly control AP-1 activity in the nucleus thus limiting the risk of deregulated oncogene expression.
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PMID:Strong and prolonged induction of c-jun and c-fos proto-oncogenes by photodynamic therapy. 867 54

At present, the exact mechanism of the pathogenic effect of anti-PR-3 antibodies remains unknown. Interaction of anti-neutrophil cytoplasmic antibodies (ANCAs) with human umbilical vein endothelial cells (HUVECs) may play a key role. Recently we were able to show that ANCAs recognize their target antigen, PR-3, translocated into the membrane of HUVECs. The objective of this study was to investigate regulation, i.e. signal transduction pathways, of PR-3 expression in endothelial cells. HUVECs were isolated according to the method of Jaffe et al. and cultured under standard conditions. A cyto-enzyme-linked immunosorbent assay (ELISA) with unfixed cells was performed. Membrane-expressed PR-3 was detected by affinity-purified and monoclonal anti-PR-3 Ab. Tumour necrosis factor alpha (TNF-alpha)-induced membrane expression of PR-3 could be blocked with the RNA synthesis inhibitor actinomycin D, the protein kinase C (PKC) and proteinase A (PKA) inhibitor staurosporine, the specific PKA inhibitor calphostin C, the c-AMP-dependent PKA inhibitor KT5720 and the tyrosine kinase inhibitor genistein in a dose-dependent manner. The effect of calphostin C was the most significant. In addition, the effect of phorbol 12-myristate 13-acetate (PMA), a mediator of intracellular second messengers, was investigated. In our study, pretreatment of cells with PMA for 48 h led to a down-regulation of PR-3 expression. This effect, however, could be overridden by TNF-alpha stimulation, i.e. TNF-alpha-induced membrane expression of PR-3 was resistant to down-regulation of PKC. In conclusion, our data suggest that translocation of PR-3 in HUVECs is an active process depending on protein synthesis. PR-3 expression by HUVECs may involve a PKC reactive to cytokines such as TNF-alpha which induces PR-3 expression at a transcriptional level.
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PMID:Signal transduction pathways of membrane expression of proteinase 3 (PR-3) in human endothelial cells. 939 84

Tumour necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) are potent inflammatory cytokines produced by osteoblasts and whose contribution to bone loss occurring in oestrogen deficiency is well documented. Calcitonin gene-related peptide (CGRP) is a neuropeptide abundantly concentrated in sensory nerve endings innervating bone metaphyses and periosteum suggesting that it controls bone homeostasis locally. Since CGRP was shown to inhibit TNF-alpha production by T cells and stimulate IL-6 expression by fibroblasts, this study was designed to investigate whether CGRP regulated TNF-alpha and IL-6 production by osteoblasts. We show that CGRP inhibits the production of TNF-alpha by both lipopolysaccharide (LPS)- and IL-1-stimulated fetal rat osteoblasts. Like CGRP, the cAMP agonists prostaglandin E2 (PGE2), dibutyryl cAMP (Bt2cAMP) and forskolin inhibit TNF-alpha production by osteoblasts. Exposure of osteoblasts to a high dose of phorbol myristoyl acetate (PMA) to deplete PKC activity abolished CGRP-mediated TNF-alpha suppression. In contrast with its potent inhibition of TNF-alpha production, we show that CGRP is a weak inducer of IL-6 when compared to PGE2, Bt2cAMP and forskolin. However, in presence of isobutylmethylxanthine (IBMX) CGRP stimulates the production of IL-6. Collectively, these data suggest that the inhibition of TNF-alpha CGRP is cAMP dependent and PMA sensitive and that the concentration of intracellular cAMP may be a regulatory mechanism for IL-6 expression in osteoblasts.
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PMID:The neuropeptide calcitonin gene-related peptide inhibits TNF-alpha but poorly induces IL-6 production by fetal rat osteoblasts. 941 11

Tumour necrosis factor receptor (TNFR) superfamily members play critical roles in the regulation of cell proliferation and death. One member of the TNFR superfamily, CD27, is unique because it is the only covalently linked homodimer in the family. CD27 and its cellular ligand, CD70, have been implicated in the regulation of T cell and B cell interactions that lead to cellular activation and regulation of immunoglobulin expression. Due to the unique nature of CD27, we chose to screen a number of B cell lymphoma cell lines for CD27 and CD70 expression and evaluate CD27 activation by antibody cross-linking. Two cell lines, HT and SU-4, showed greater cellular proliferation when CD27 was cross-lined and this correlated with increased PKC activation. Additionally, in the HT cell line cell surface expression of IgG was increased by CD27 cross-linking. Thus we have identified cellular systems for the study of CD27 signal transduction that will allow definition of the CD27 signal cascade of some B cell lymphomas.
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PMID:CD27 signals through PKC in human B cell lymphomas. 1041 48

Tumour necrosis factor-alpha (TNF-alpha) is a major immunomodulatory and proinflammatory cytokine which is shed in its soluble form by a membrane-anchored zinc protease, identified as a disintegrin and metalloproteinase (ADAM) called TNF-alpha convertase (TACE; ADAM17). The role of this protease in the adult nervous system remains poorly understood. During cerebral ischemia and subsequent reperfusion, expression and release of TNF-alpha have been shown. We have investigated the expression and activity of TACE in an in vitro model of brain ischemia consisting of rat forebrain slices exposed to oxygen-glucose deprivation (OGD). OGD caused the release of TNF-alpha, an effect which was inhibited by a hydroxamate-based metalloprotease inhibitor, BB-3103, with an IC(50) of 0.1 microM, suggesting that TNF-alpha release results selectively from TACE activity. Assay of TACE enzymatic activity on a fluorescein-labelled peptide spanning the cleavage site in pro-TNF-alpha, as well as Western blot and RT-PCR analyses showed that TACE is present in control forebrain and, more interestingly, that TACE expression is increased in OGD-exposed tissue. TACE enzymatic activity from OGD-exposed slices was significantly inhibited by cycloheximide, suggesting that de novo synthesis of TACE contributes to TNF-alpha release after ischaemia. Moreover, it was also inhibited by bisindolylmaleimide I, indicating that TACE activity is regulated by PKC. These findings posed the question of what was its function therein. Among other actions, TNF-alpha has been described to be involved in the expression of inducible nitric oxide synthase (iNOS), a high-output NOS isoform associated to cellular damage, but the link between TNF-alpha release after brain ischaemia and iNOS expression in this condition has not been shown. We have now found that iNOS expression in OGD-subjected brain slices is inhibited by BB-3103 at concentrations below 1 microM, indicating that shedding of TNF-alpha by TACE plays a necessary part in the induction of this NOS isoenzyme after OGD. Taken together, these data demonstrate that (1) TACE/ADAM17 activity accounts for the majority of TNF-alpha shedding after OGD in rat forebrain slices, (2) an increase in TACE expression contributes, at least in part, to the rise in TNF-alpha after OGD and (3) iNOS expression in OGD-subjected brain slices results from TACE activity and subsequent increase in TNF-alpha levels.
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PMID:Up-regulation of TNF-alpha convertase (TACE/ADAM17) after oxygen-glucose deprivation in rat forebrain slices. 1140 1


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