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)

Acidic fibroblast growth factor (aFGF) enhances nerve growth factor (NGF) synthesis by astrocytes obtained from various brain regions. NGF secretion by fibrous-shaped astrocytes transformed by dibutyryl-cAMP (db-cAMP) pretreatment was less than that by untreated astrocytes. However, aFGF also enhanced NGF secretion by fibrous-shaped astrocytes. The effects of various kinds of intracellular signaling modulators on NGF synthesis were examined. None of the following second messenger effectors had an effect on NGF synthesis: protein kinase C (PKC) agonist (phorbol myristate acetate (PMA)) or antagonist (sphingosine (SP)). LiCl, and ionomycin (Iono). Further, increases of intracellular cAMP by forskolin (FK) or db-cAMP have no significant effect on NGF synthesis in astrocytes under a standard culture condition. However, NGF synthesis by astrocytes in the presence of aFGF was significantly enhanced by db-cAMP, but not by FK or sodium butyrate. These results indicate that an excessive amount of cAMP enhances the effect of aFGF on NGF synthesis in astrocytes. NGF synthesis in astrocytes was not affected by treatment with anti-aFGF or anti-bFGF neutralizing antibodies, indicating that FGFs are not involved in the autocrine regulation of NGF synthesis in astrocytes. Transforming growth factor-beta 1 (TGF-beta 1), which inhibits some effects of FGFs, increased NGF synthesis in concert with aFGF. Furthermore, the highest NGF synthesis was observed when astrocytes were stimulated by all of the following cytokines: aFGF, interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) and TGF-beta 1. The mechanism regulating NGF synthesis in fibroblasts obtained from prenatal rat skin was also investigated. Acidic FGF, basic FGF (bFGF), epidermal growth factor (EGF), platelet-derived growth factor (PDGF), transforming growth factor-alpha (TGF-alpha), TGF-beta 1, IL-1 beta, and TNF-alpha were found to be regulators of NGF synthesis in skin fibroblasts. Among these cytokines, aFGF is the most potent regulator of NGF synthesis in fibroblasts. NGF synthesis by skin fibroblasts, either in the presence or absence of aFGF, was not modified by any of the following: FK, PMA, SP, LiCl, and Iono. However, db-cAMP significantly enhanced NGF synthesis in both conditions. Sodium butyrate enhanced NGF synthesis in the presence of aFGF, but not in the absence of aFGF. These results suggest that an excessive amount of cAMP and butyrate moiety regulate NGF synthesis in skin fibroblasts in different ways.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Cooperative regulation of nerve growth factor synthesis and secretion in fibroblasts and astrocytes by fibroblast growth factor and other cytokines. 137 78

We examined the interaction of parathyroid hormone (PTH) and recombinant human insulin-like growth factor I (IGF-I) on collagen synthesis in 21-day fetal rat calvariae as assessed by measuring the incorporation of [3H]proline into collagenase-digestible protein. After 96 hours of culture, 10 nM PTH antagonized the stimulation of collagen synthesis and partially blocked the increase in dry weight produced by 10 nM IGF-I. The effect of PTH to block IGF-I stimulated collagen synthesis was observed in the central bone of calvariae and was mimicked by forskolin and phorbol 12-myristate 13-acetate, but not by 1,25-dihydroxyvitamin D3, transforming growth factor-alpha or dexamethasone. Our data are consistent with the concept that the direct effect of PTH is to inhibit basal CDP labeling and fully oppose IGF-I stimulated CDP labeling. The finding that this effect of PTH is mimicked by forskolin and PMA suggests that this block in IGF-I stimulation of CDP labeling involves both cAMP and protein kinase C mediated pathways.
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PMID:Parathyroid hormone blocks the stimulatory effect of insulin-like growth factor-I on collagen synthesis in cultured 21-day fetal rat calvariae. 196 62

Overexpression of the epidermal growth factor (EGF) receptor (c-erbB) proto-oncogene is a frequent occurrence in human carcinoma and appears to accompany autocrine or paracrine transforming growth factor-alpha expression, which in model systems can result in activation of EGF receptor tyrosine kinase activity and phenotypic transformation. Here we have investigated the transcriptional regulation of the EGF receptor gene, by run-on transcription in isolated nuclei derived from epithelioid tumor lines. The level of transcription was measured at various points on the 100-kilobase pair EGF receptor gene locus, on either sense or antisense DNA strands. We find the level of sense strand transcription along exon 1 is 8-fold higher than transcription in exons 2-26. Primary EGF receptor transcripts appear to pause or terminate prematurely between exons 1 and 2. Termination was mapped to a sequenced region approximately 2 kilobase pairs 3' of exon 1, proximal to a previously reported DNase I hypersensitive site and an enhancer-like activity. Transcription in the CpG-rich region surrounding exon 1 is bidirectional, with antisense transcripts initiating in intron 1 and extending through the coding first exon. Activation of protein kinase C results in a 5-fold induction of EGF receptor transcription, accompanied by a slow release in the block RNA elongation between exon 2 and exon 26, showing that EGF receptor RNA synthesis may be altered by changes in de novo transcription and by a block to RNA elongation.
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PMID:Contributory effects of de novo transcription and premature transcript termination in the regulation of human epidermal growth factor receptor proto-oncogene RNA synthesis. 198 48

Cleavage of the membrane-anchored precursor for transforming growth factor-alpha (TGF-alpha), a rate-limiting step in the generation of soluble TGF-alpha, can be stimulated by phorbol esters acting via protein kinase C. In the present study, activators of other intracellular signaling pathways were tested for their ability to stimulate pro-TGF-alpha cleavage in Chinese hamster ovary cells transfected with a pro-TGF-alpha cDNA. Treatment with the Ca2+ ionophore, A23187, rapidly increased the rate of pro-TGF-alpha cleavage over 25-fold. This effect of A23187 on pro-TGF-alpha cleavage was dependent on the influx of extracellular calcium and was largely independent of protein kinase C activation. In contrast, phorbol 12-myristate 13-acetate stimulation of pro-TGF-alpha cleavage via activation of protein kinase C did not require extracellular calcium. Stimulation of pro-TGF-alpha cleavage by serum was largely independent of both protein kinase C and extracellular calcium influx, whereas activators of protein kinase A and protein kinase G did not stimulate pro-TGF-alpha cleavage. These results suggest that regulation of pro-TGF-alpha cleavage is a complex process that can be controlled by extracellular agents via at least three distinct signal transduction pathways.
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PMID:Multiple signals activate cleavage of the membrane transforming growth factor-alpha precursor. 200 14

A single topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) to mouse skin decreased 125I-labeled epidermal growth factor (EGF) binding in epidermal membrane preparations within 1 h while 1,8-dihydroxy-3-methyl-9-anthrone (chrysarobin) gradually reduced binding with maximum inhibition at 15 h. Subsequently, 125I-EGF binding increased to approximately 200% of control in epidermal membrane preparations from both TPA- and chrysarobin-treated mice. A single application of TPA but not chrysarobin resulted in a rapid translocation of protein kinase C (PKC) to the membrane; however, treatment with both promoters ultimately led to a time-dependent loss of PKC activity in both membrane and cytosol fractions. The initial inhibition of 125I-EGF binding was sustained for at least 24 h after single and multiple treatments with both promoting agents. Acid washing restored EGF binding to control levels in membrane preparations obtained 24 h after a single application, whereas acid washing of membrane preparations obtained 24 h after a second application of TPA or chrysarobin increased binding (2.5-fold and 1.5-fold that of the control, respectively). The presence of increased amounts of ligands for the EGF receptor in tumor promoter-treated epidermis was initially confirmed in 125I-EGF binding competition experiments using NRK-49F cells. A single topical application of TPA or chrysarobin induced elevated levels of transforming growth factor-alpha (TGF-alpha) mRNA at 6 h or 15-24 h, respectively. Elevated levels of a TGF-alpha precursor (21 kDa) were subsequently observed in cytosol and membrane preparations after single and multiple applications of TPA or chrysarobin. These results suggest that repeated topical application of tumor promoters may lead to sustained loss of a negative-feedback mechanism involving phosphorylation at Thr-654 of the EGF receptor by PKC. The concomitant elevation of ligands, such as TGF-alpha, may provide a mechanism for sustained cell proliferation essential for skin tumor promotion.
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PMID:Evidence for autocrine/paracrine growth stimulation by transforming growth factor-alpha during the process of skin tumor promotion. 200 35

This paper reviews our work on the localization of transforming growth factor-alpha (TGF alpha) in normal adult tissues and the regulation of its synthesis and that of its receptor. We detected TGF alpha immunohistochemically in brain neurons and showed the TGF alpha mRNA derived from the human brain stem is virtually identical to the mRNA derived from human renal tumour cells. In cells derived from anterior pituitary glands, another site of TGF alpha expression, TGF alpha secretion and mRNA levels can be regulated by phorbol esters. The expression of the epidermal growth factor (EGF) receptor, which is also the TGF alpha receptor, is also stimulated by phorbol esters. Similar stimulation of receptor and ligand expression in human breast cancer cells was shown in response to phorbol esters and EGF. The ability of ligand to stimulate its own synthesis and that of its receptor suggests the presence of an autocrine positive feedback loop, however we were unable to break this loop in the breast cancer cells by antibodies that blocked the interaction of TGF alpha with the EGF receptor. The ability of EGF to stimulate EGF receptor and TGF alpha expression appears to require protein kinase C, since inhibition of this enzyme blocked the ability of EGF to stimulate these genes. These studies raise the possibility that hormones capable of activating protein kinase C could stimulate EGF receptor and TGF alpha expression.
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PMID:TGF alpha in normal physiology. 210 4

Diploid WB rat liver epithelial cells contain abundant, rapidly internalized epidermal growth factor receptors, and respond pleiotropically to ligand binding. Signal transduction pathways downstream from the EGF receptor involve activation of elements that are both dependent on and independent of protein kinase C activation. Neoplastic transformation of wild-type WB rat liver epithelial cells by exposure to N-methyl-N'-nitro-N-nitrosoguanidine is associated with progressive alterations in the responses of affected cells to binding of EGF to EGF receptors, including heightened cell proliferation and the expression of several other phenotypic properties. Tumorigenic rat liver epithelial cells acquire the ability to express transforming growth factor-alpha (TGF-alpha), and to secrete this growth factor in a regulated and then unregulated manner. TGF-alpha expression, together with the presence of abundant EGF receptors, provides affected cells with an autocrine growth cycle. The ability of transformed WB rat liver epithelial cells to produce tumors cosegregates clonally with TGF-alpha expression and with heightened expression of c-myc, c-Ha-ras and c-Ki-ras proto-oncogenes.
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PMID:Sequential changes in epidermal growth factor receptor/ligand function in cultured rat liver epithelial cells transformed chemically in vitro. 218 76

Exposure of cultured human epidermal keratinocytes to the protein kinase C (Ca2+- and phospholipid-dependent protein kinase)-activating phorbol esters 12-O-tetradecanoylphorbol-13-acetate (TPA) or 4-beta-phorbol-12,13-didecanoate markedly enhanced accumulation of transforming growth factor-alpha (TGF-alpha) mRNA and secretion of TGF-alpha protein. The nonactivating phorbol ester, 4-alpha-phorbol 12,13-didecanoate, had no effect. In the absence of exogenous growth factors, confluent cultures of keratinocytes express low or undetectable levels of TGF-alpha mRNA and protein. While TPA and epidermal growth factor treatment of keratinocyte cultures deprived of growth factors both induced TGF-alpha mRNA expression, maximum induction by TPA is 5-fold greater than epidermal growth factor. Furthermore, the addition of epidermal growth factor did not enhance TPA-mediated induction of TGF-alpha mRNA expression. Under these experimental conditions, TPA increased levels of secreted TGF-alpha protein by 20-fold at 24 h. Concentration dependence and kinetic studies of TGF-alpha expression showed that TPA (greater than or equal to 1 ng/ml) induced accumulation of TGF-alpha mRNA with an optimum concentration of 10 ng/ml. TGF-alpha mRNA expression increased within 1 h following TPA treatment (10 ng/ml) and peaked at 5 h. At 24 h, TPA-treated cultures still expressed elevated levels of TGF-alpha mRNA (1.7-fold). Protein secretion into the medium was enhanced 2-fold (5 h) to 3-fold (24 h) by TPA treatment of keratinocyte cultures containing growth factors. Prolonged pretreatment (24 h) of keratinocyte cultures with TPA caused marked desensitization of TGF-alpha mRNA expression to repeated stimulation by phorbol ester. The synthetic diacylglycerol, 1,2-sn-dioctanoylglycerol, enhanced levels of TGF-alpha transcription and secretion of TGF-alpha protein. The rate of TGF-alpha mRNA accumulation peaked and declined earlier for 1,2-sn-dioctanoylglycerol compared to TPA. 1,2-sn-Dioctanoylglycerol (50 micrograms/ml) increased production and secretion of TGF-alpha protein, but less than TPA treatment. An inhibitor of protein kinase C, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, also inhibited 1,2-sn-dioctanoylglycerol-mediated accumulation of TGF-alpha mRNA. Cycloheximide failed to inhibit TGF-alpha mRNA expression induced by TPA and, when added alone to keratinocyte cultures, significantly enhanced TGF-alpha mRNA accumulation. Actinomycin D abrogated transcriptional activation of TGF-alpha mRNA by TPA. These studies suggest that activation of protein kinase C by active phorbol esters or diacylglycerols is responsible, at least in part, for TGF-alpha gene expression.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Induction of transforming growth factor-alpha expression in human keratinocytes by phorbol esters. 292 87

Angiogenesis depends on cytokines and vascular cell adhesion events. Two cytokine-dependent pathways of angiogenesis were shown to exist and were defined by their dependency on distinct vascular cell integrins. In vivo angiogenesis in corneal or chorioallantoic membrane models induced by basic fibroblast growth factor or by tumor necrosis factor-alpha depended on alpha v beta 3, whereas angiogenesis initiated by vascular endothelial growth factor, transforming growth factor-alpha, or phorbol ester depended on alpha v beta 5. Antibody to each integrin selectively blocked one of these pathways, and a cyclic peptide antagonist of both integrins blocked angiogenesis stimulated by each cytokine tested. These pathways are further distinguished by their sensitivity to calphostin C, an inhibitor of protein kinase C that blocked angiogenesis potentiated by alpha v beta 5 but not by alpha v beta 3.
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PMID:Definition of two angiogenic pathways by distinct alpha v integrins. 749 98

Hepatocyte growth factor (HGF) is a potent mitogen for rat and human hepatocytes in primary culture and appears to be the physiological hepatotrophic factor that triggers or modulates liver regeneration. Regulation of HGF gene expression and the protein production in human skin fibroblasts was examined. Addition of epidermal growth factor (EGF), platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), acidic fibroblast growth factor (aFGF) and transforming growth factor-alpha (TGF-alpha) to confluent cultures of the cells markedly stimulated HGF secretion from the cells. The stimulating effect of EGF, PDGF and bFGF was further investigated. The effect of all three growth factors was maximal at 3-30 ng/ml and was accompanied by an increase in HGF mRNA levels. The mRNA levels were not elevated at 5 h but were at 10 h or more after addition of EGF. The levels of HGF mRNA in fibroblasts treated with the optimal doses of EGF, PDGF, bFGF, aFGF and TGF-alpha for 24 h were 6, 4, 5, 4 and 5 times that of control cultures incubated in medium only, respectively. The growth factor-induced HGF mRNA expression and HGF secretion was inhibited by addition of TGF-beta 1 or dexamethasone. Pretreatment with a high dose of phorbol 12-myristate 13-acetate (PMA), which causes down-regulation in protein kinase C (PKC) activity and PMA-induced HGF secretion, did not reduce the effects of the growth factors on HGF mRNA expression and HGF secretion, but rather enhanced them.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Induction of hepatocyte growth factor in human skin fibroblasts by epidermal growth factor, platelet-derived growth factor and fibroblast growth factor. 753 91


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