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)

The objective of the present study was to investigate the implication of protein kinase A (PKA), protein kinase C (PKC), and receptor protein tyrosine kinase (R-PTK) pathways in the regulation of estradiol (E2) and progesterone (P4) production by bovine granulosa cells. Cells were harvested from bovine follicles (8-15 mm diameter) and cultured without serum for an initial 3 days (37 degrees C; 5% CO(2) in air; D1-D3). On the fourth day of culture (D4), E2 and P4 production were stimulated with FSH (1-6 ng/ml) or forskolin (FSK) in the presence or absence of intracellular effectors of PKA, PKC, and R-PTK. Culture medium was collected and replaced each day. Stimulation of granulosa cell adenylate cyclase activity with FSK (0.06-3.75 microM) mimicked FSH, inducing a quadratic increase (P < 0.001) of E2 production and a continuous elevation of P4 (P < 0.01). Inhibition of R-PTK activity with genistein (25-50 microM) increased the sensitivity of cells to FSH as demonstrated by a leftward shift in the dose response curve (P < 0.001). Treatment with transforming growth factor-alpha (TGFalpha; 0. 1 ng/ml) abolished the FSH-induced E2 production (P < 0.001) and this effect was not reversed (P < 0.001) by FSK or by genistein. Furthermore, the inhibitory effect of TGFalpha on FSH-induced E2 production was reproduced by phorbol 12-myristate 13-acetate (PMA; 1. 25-2.5 microM), a PKC activator (P < 0.001). Interestingly, genistein inhibited P4 production (P < 0.05). From these results, we conclude that E2 production by bovine granulosa cells is mediated by intracellular factors and can be stimulated downstream from the FSH receptor. The results also suggest that stimulation of R-PTK and/or PKC activities, as probably occurs with TGFalpha, negatively affects the PKA pathway, thus decreasing E2 production. Furthermore, inhibition of R-PTK leads to an increase production of E2 and may limit luteinization of bovine granulosa cells.
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PMID:Intracellular regulation of estradiol and progesterone production by cultured bovine granulosa cells. 1054 77

The biological effects of epidermal growth factor receptor (EGFR) activation may differ between epidermal suprabasal and basal keratinocytes, since growth factors are mitogenic in adherent cells only in the presence of cell-extracellular matrix (ECM) interaction. To investigate biological effects of EGFR activation on keratinocytes without cell-ECM interaction, we cultured normal human keratinocytes on polyhydroxyethylmethacrylate-coated plates, which disrupt cell-ECM but not cell-cell interaction. The cells initially expressed keratin 10 (K10) and then profilaggrin, mimicking sequential differentiation of epidermal suprabasal keratinocytes. The addition of EGF or transforming growth factor-alpha promoted late terminal differentiation (profilaggrin expression, type 1 transglutaminase expression and activity, and cornified envelope formation) of the suspended keratinocytes, while suppressing K10 expression, an early differentiation marker. These effects were attenuated by EGFR tyrosine kinase inhibitor PD153035 or an anti-EGFR monoclonal antibody, whereas protein kinase C inhibitors H7 and bisindolylmaleimide I or mitogen-activated protein kinase/extracellular signal-regulated kinase kinase inhibitor PD98059 abolished profilaggrin up-regulation but not K10 suppression. Since the antidifferentiative role of EGFR on cell-ECM interaction-conserved keratinocytes has been well documented, our results indicate that the biological effects of EGFR on keratinocytes are influenced by cell-ECM interaction and suggest that EGFR activation promotes rather than inhibits the terminal differentiation of suprabasal epidermal keratinocytes.
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PMID:Activation of epidermal growth factor receptor promotes late terminal differentiation of cell-matrix interaction-disrupted keratinocytes. 1060 Dec 94

The ectodomain of several membrane-bound proteins can be shed by proteolytic cleavage. The activity of the proteases involved in shedding is highly regulated by several intracellular second messenger pathways, such as protein kinase C (PKC) and intracellular Ca(2+). Recently, the shedding of the adhesion molecule L-selectin has been shown to be regulated by the interaction of calmodulin (CaM) with the cytosolic tail of L-selectin. Prevention of CaM-L-selectin interaction by CaM inhibitors or mutation of a CaM binding site in L-selectin induced L-selectin ectodomain shedding. Whether this action of CaM inhibitors also affects other membrane-bound proteins is not known. In the present paper we show that CaM inhibitors also stimulate the cleavage of several other transmembrane proteins, such as the membrane-bound growth factor precursors pro-transforming growth factor-alpha and pro-neuregulin-alpha2c, the receptor tyrosine kinase, TrkA, and the beta-amyloid precursor protein. Cleavage induced by CaM inhibitors was a rapid event, and resulted from the activation of a mechanism that was independent of PKC or intracellular Ca(2+) increases, but was highly sensitive to hydroxamic acid-based metalloprotease inhibitors. Mutational analysis of the intracellular domain of the TrkA receptor indicated that CaM inhibitors may stimulate membrane-protein ectodomain cleavage by mechanisms independent of CaM-substrate interaction.
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PMID:Stimulation of cleavage of membrane proteins by calmodulin inhibitors. 1067 54

The induction of epidermal differentiation by extracellular Ca2+ involves activation of both tyrosine kinase and protein kinase C (PKC) signaling cascades. To determine if the differentiation-dependent activation of tyrosine kinase signaling can influence the PKC pathway, we examined the tyrosine phosphorylation status of PKC isoforms in primary mouse keratinocytes stimulated to terminally differentiate with Ca2+. Elevation of extracellular Ca2+ induced tyrosine phosphorylation of PKC-delta, but not the other keratinocyte PKC isoforms (alpha, epsilon, eta, zeta). We have previously demonstrated that activation of the epidermal growth factor receptor (EGFR) pathway induces PKC-delta tyrosine phosphorylation in basal keratinocytes (Denning M F, Dlugosz A A, Threadgill D W, Magnuson T, Yuspa S H (1996) J Biol Chem 271: 5325-5331). When basal keratinocytes were stimulated to differentiate by Ca2+, the level of cell-associated transforming growth factor-alpha (TGF-alpha) increased 30-fold, while no increase in secreted TGF-alpha was detected. Furthermore, Ca2+-induced tyrosine phosphorylation of PKC-delta and phosphotyrosine-association of the receptor adapter protein Shc was diminished in EGFR -/- keratinocytes, suggesting that EGFR activation may occur during keratinocyte differentiation. Tyrosine phosphorylated PKC-delta was also detected in mouse epidermis, suggesting that this differentiation-associated signaling pathway is physiological. These results establish a requirement for the EGFR in Ca2+-induced tyrosine phosphorylation of PKC-delta, and document the production of cell-associated TGF-alpha in differentiated keratinocytes which may function independent of its usual mitogenic effects.
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PMID:Cross-talk between epidermal growth factor receptor and protein kinase C during calcium-induced differentiation of keratinocytes. 1083 17

The almost ubiquitously expressed ClC-2 chloride channel is activated by hyperpolarization and osmotic cell swelling. Osmotic swelling also activates a different class of outwardly rectifying chloride channels, and several reports point to a link between protein tyrosine phosphorylation and activation of these channels. This study examines the possibility that transforming growth factor-alpha (TGF-alpha) modulates ClC-2 activity in human colonic epithelial (T84) cells. TGF-alpha (0.17 nM) irreversibly inhibited ClC-2 current in nystatin-perforated whole cell patch-clamp experiments, whereas a superimposed reversible activation of the current was observed at 8.3 nM TGF-alpha. Both effects required activation of the intrinsic epidermal growth factor receptor (EGFR) tyrosine kinase activity, of phosphoinositide 3-kinase, and of protein kinase C. With microspectrofluorimetry of the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, TGF-alpha was shown to reversibly alkalinize T84 cells at 8.3 nM but not at 0.17 nM, suggesting that 8.3 nM TGF-alpha-induced alkalinization activates ClC-2 current. This study indicates that ClC-2 channels are targets for EGFR signaling in epithelial cells.
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PMID:Regulation of ClC-2 chloride channels in T84 cells by TGF-alpha. 1135 Jul 54

The human mucin gene MUC4 encodes a large transmembrane mucin that is thought to play important roles in tumor cell biology and that is overexpressed in human pancreatic carcinomas. In this report, we describe the structure and functional activity of the 5'-flanking region, including 1.0 kilobase of the promoter. The long 5'-untranslated region (2.7 kilobases) is characterized by a high content of GC in its 3'-end. The first TATA box was located at -2672/-2668. Multiple transcription start sites and a high density of putative binding sites for Sp1 (GC and CACCC boxes), AP-1/-2/-4, cAMP-responsive element-binding protein, GATA, GR, and STAT transcription factors were found within the 5'-flanking region. Transcriptional activity of the promoter was assessed using pGL3-luciferase deletion mutants in two MUC4-expressing (CAPAN-1 and CAPAN-2) and one nonexpressing (PANC-1) pancreatic cancer cell line. Two highly active fragments (-219/-1 and -2781/-2572) that drive MUC4 transcription in CAPAN-1 and CAPAN-2 cells were identified. Gel retardation assays indicated that Sp1 and Sp3 bind to cognate cis-elements found in the 5'-flanking region and that Sp1 transactivates, whereas Sp3 inhibits the GC-rich region (-464/-1) in CAPAN-2 cells. Activation of protein kinase C with phorbol ester and treatment of cells with epidermal growth factor and transforming growth factor-alpha resulted in up-regulation of the promoter. Tumor necrosis factor-alpha and interferon (IFN)-gamma inflammatory cytokines had no or mild effect on MUC4 transcriptional activity when used alone. However, a very strong synergistic effect (10-12-fold activation) between IFN-gamma and tumor necrosis factor-alpha or IFN-gamma and transforming growth factor-alpha was obtained in CAPAN-2 cells. Altogether these results demonstrate that the 5'-flanking region of MUC4 contains epithelial cell-specific, positive, and negative regulatory cis-elements, that Sp1/Sp3 are important regulators of MUC4 basal expression, and that its regulation in pancreatic cancer cells involves complex interplay between several signaling pathways.
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PMID:Characterization of human mucin gene MUC4 promoter: importance of growth factors and proinflammatory cytokines for its regulation in pancreatic cancer cells. 1141 7

Phosphorylation of extracellular signal-regulated kinases (ERK1/ERK2) has been implicated in cell proliferation of mammalian cells. In the present study, we investigated the role of docosahexaenoic acid (DHA) in the modulation of ERK1/ERK2 phosphorylation, stimulated either with phorbol 12-myristate 13-acetate (PMA) or transforming growth factor-alpha (TGFalpha) in NIH/3T3 cells. We observed that both PMA and TGFalpha induced ERK1/ERK2 phosphorylation within 5 min of stimulation. PMA acts upstream of MEK and via activation of protein kinase C (PKC), as GF109203X, a potent PKC inhibitor, and U0126, a MEK inhibitor, abolished its actions on ERK1/ERK2 phosphorylation. TGFalpha did not act via PKC because GF109203X failed to curtail the degree of ERK1/ERK2 phosphorylation in these cells. DHA alone failed to induce the phosphorylation of these mitogen-activated protein (MAP) kinases; however, this fatty acid significantly curtailed the PMA- but not TGFalpha-induced MAP kinase enzyme activity and phosphorylation in NIH/3T3 cells. Furthermore, we observed that DHA significantly inhibited PMA-induced translocation of two PKC isoforms, PKC alpha and PKC epsilon, from cytosol to plasma membrane. Interestingly, DHA failed to inhibit the PMA-induced translocation PKC delta isoform in these cells. Furthermore, DHA decreased PMA-induced proliferation of NIH/3T3 cells. In this study, we show for the first time that DHA inhibits MAP kinase ERK1/ERK2) activation and proliferation of NIH/3T3 cells via its inhibitory action on PKC alpha and epsilon isoforms.
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PMID:Docosahexaenoic acid modulates phorbol ester-induced activation of extracellular signal-regulated kinases 1 and 2 in NIH/3T3 cells. 1159 32

Epidermal growth factor receptor (EGFR) ligands are synthesized as type I membrane protein precursors exposed at the cell surface. Shedding of the ectodomain of these proteins is the way cells regulate the equilibrium between cell-associated and diffusible forms of these growth factors. Whereas the regulated shedding of transforming growth factor-alpha, HB-EGF, and amphiregulin precursors have been clearly established, regulation of full-length pro-EGF shedding has not been clearly demonstrated. Here, using both wild-type and M2 mutant CHO-K1 as well as HeLa cell lines transiently transfected with epitope-tagged rat pro-EGF expression plasmid, we demonstrate that these cells synthesize EGF as a high molecular weight membrane-associated precursor glycoprotein expressed at the cell surface. All cell lines are able to release the entire ectodomain of pro-EGF in the extracellular medium following juxtamembrane cleavage of the precursor once it is present at the cell surface. More significantly we clearly established that CHO-M2 and HeLa cells only constitutively release low levels of pro-EGF. This shedding is a regulated phenomenon in wild-type CHO cells where it can be induced by different agents such as phorbol 12-myristate 13-acetate (PMA), pervanadate, and serum but not by calcium ionophores. Using specific inhibitors as well as protein kinase C (PKC) depletion, PMA stimulation was shown to be completely dependent on PKC activation whereas pervanadate and serum stimulation were not. Regulated ectodomain shedding involves the activity of a zinc metalloprotease as determined by inhibition with phenantrolin and TAPI-2 and by the results obtained with the CHO-M2 shedding defective mutant cell line. Comparison of the ability of CHO and HeLa cell lines to shed pro-EGF and pro-TNF-alpha upon stimulation greatly suggests that TACE (ADAM 17) may not be the ectoprotease involved in the secretion of pro-EGF ectodomain and that this protease, which remains to be identified, shows a restricted cellular expression pattern.
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PMID:Regulated cell surface pro-EGF ectodomain shedding is a zinc metalloprotease-dependent process. 1294 92

The development of androgen-independent prostate cancer (AI PrCa) involves constitutive Erk1/2 activation sustained by the epidermal growth factor/transforming growth factor-alpha/EGF receptor (EGF/TGFalpha/EGFR) axis and other trophic signaling mechanisms in neoplastic human prostate epithelial cells in vivo. In this report, we show that growth-inhibitory concentrations of the dietary phytochemical resveratrol suppress EGFR-dependent Erk1/2 activation pathways stimulated by EGF and phorbol ester (12- O -tetradecanoyl phorbol 13-acetate, TPA) in human AI PrCa PC-3 cells in vitro. Because protein kinase C (PKC) is the major cellular receptor for phorbol esters and taking into consideration that resveratrol is PKC-inhibitory, we investigated resveratrol effects on cellular PKC isozymes associated with the suppression of TPA-induced Erk1/2 activation. The PKC isozyme composition of PC-3 cells was defined by Western analysis of the cell lysate with a comprehensive set of isozyme-selective PKC Ab's. PC-3 cells expressed PKCalpha, epsilon, zeta, iota, and PKD (PKCmicro), as did another human AI PrCa cell line of distinct genetic origin, DU145. The effects of resveratrol on TPA-induced PKC isozyme activation were defined by monitoring PKC isozyme translocation and autophosphorylation. Under conditions where resveratrol suppressed TPA-induced Erk1/2 activation, the phytochemical produced isozyme-selective interference with TPA-induced translocation of cytosolic PKCalpha to the membrane/cytoskeleton and selectively diminished the amount of autophosphorylated PKCalpha in the membrane/cytoskeleton of the TPA-treated cells. These results demonstrate that resveratrol abrogation of a PKC-mediated Erk1/2 activation response in PC-3 cells correlates with isozyme-selective PKCalpha inhibition. The results provide evidence that resveratrol may have value as an adjuvant cancer therapeutic in advanced prostate cancer.
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PMID:Resveratrol antagonizes EGFR-dependent Erk1/2 activation in human androgen-independent prostate cancer cells with associated isozyme-selective PKC alpha inhibition. 1473 59

Antisense strategy using synthetic oligodeoxynucleotides has been applied to the suppression of specific gene expression, the modulation of various gene expression, and its biological activity. Antisense strategy is applicable for the growth suppression of glioma cells. Several genes, including transforming growth factor-alpha, basic fibroblast growth factor, fibroblast growth factor receptor 1, vascular endothelial growth factor, telomerase, topoisomerase II alpha-subunit, protein kinase C-alpha, and microtubule-associated protein 1A, have been targeted by antisense strategy in glioma cells. These antisense strategies provide a potential novel antitumor therapy for gliomas.
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PMID:Specific gene suppression using antisense strategy for growth suppression of glioma. 1544 7


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