Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study was aimed at gaining an understanding of metabolic events responsible for the inhibition of cells in G2 phase, a known physiological restriction site in the cell cycle of multicellular organisms. In an earlier study, phosphatidic acid was proposed as an inhibitory mediator in the epidermal growth factor (EGF)-induced inhibition of A431 cells in G2 phase via the phospholipase C pathway [Kaszkin, Richards and Kinzel (1992) Cancer Res. 52, 5627-5634]. We show here that the phorbol ester phorbol 12-myristate 13-acetate (PMA) induces a reversible inhibition of the G2/M transition in A431 cells under conditions of phospholipase D-catalysed phosphatidic acid formation. Such PMA-induced inhibition in G2 phase is largely attenuated in the presence of 1-propanol (but not of 2-propanol). In this case the amount of phosphatidic acid is reduced to almost control levels, and instead phosphatidylpropanol is formed. In the case of EGF-induced activation of a phospholipase D the amount of phosphatidic acid is only slightly decreased in the presence of a primary alcohol. Under these conditions the EGF-induced G2 delay was not affected. The correlation between the formation of phosphatidic acid and the G2 delay induced by PMA, as well as by an exogenous bacterial phospholipase D (from Streptomyces chromofuscus), could be supported by using synchronized cells in order to increase the population of cells in G2 phase. This study indicates that the formation of substantial amounts of phosphatidic acid immediately before entry into mitosis seems to be important for establishing a delay in the cell cycle at the G2/M border by exogenous ligands.
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PMID:Phosphatidic acid mobilized by phospholipase D is involved in the phorbol 12-myristate 13-acetate-induced G2 delay of A431 cells. 866 Feb 73

Hepatocyte growth factor (HGF), a mesenchyme derived growth factor, promotes cell growth, cell motility, and morphogenesis in a variety of epithelial cells. The diverse responses are transduced across the cell membrane by the met/HGF receptor, a product of c-met protooncogene. The met/HGF receptor recruits a variety of second messenger molecules which relay the diverse intracellular responses of HGF. In this study, we show that HGF autophosphorylates and activates met/HGF receptor. The activated met/HGF receptor then physically associates with and activates phospholipase C-gamma (PLC-gamma). Furthermore, upon ligand stimulation, tyrosine-autophosphorylated met/HGF receptor also activates Nck oncogene product. Taken together, our results suggest that the receptor activation leads to formation of a complex in which PLC-gamma and Nck oncogene product co-exist with the activated met/HGF receptor, and that the Nck oncogene product is an important component of HGF signaling in Calu-1 and A549 cells.
Cancer Lett 1996 Jul 12
PMID:Hepatocyte growth factor induces activation of Nck and phospholipase C-gamma in lung carcinoma cells. 866 84

Many tumors produce vascular endothelial growth factor (VEGF), a paracrine factor acting selectively on endothelial cells. VEGF has many effects on cultured endothelial cells and mediates angiogenesis and enhanced vascular permeability in vivo. The endothelial signal transduction pathways of VEGF represent novel targets for cancer therapy because they are readily accessible to systemically administered drugs. We have examined VEGF-stimulated signals generated in HUVEC to identify potential targets for therapeutic intervention. The transphosphatidylation reaction has been used to monitor phospholipase D (PLD) activity; total inositol phosphates have been measured after prelabeling of cells with [3H]myoinositol; and intracellular free calcium has been measured using Fura-2 fluorescence. After HUVEC-stimulation with VEGF, there is an early influx of calcium (maximal by 100 seconds) followed by activation of PLD (half maximal by 100 seconds, EC50 70 pm). The PLD activity was inhibited by reducing extracellular calcium (150 nM, 50% inhibition), exposure to 12-O-tetradecanoylphorbol 13 acetate (200 nM, 24 hours, 100% inhibition), Roche 31,8220 (10 microM, 15 minutes, 72% inhibition), or genestein (100 microM, 30 minutes, 56% inhibition), which suggests a dependence on both protein kinase C and tyrosine phosphorylation. Activation of phospholipase C-catalyzed hydrolysis of phosphatidylinositol-4,5-bisphosphate was inferred from the production of inositol phosphates, although this response was slower (half maximal by 3 minutes). The phospholipase C activity was also dependent on influx of calcium and was partially inhibited by low (150 nM) extracellular calcium. PLD may be involved in mediating a number of endothelial responses to tumor-secreted VEGF, notably cytoskeleton-dependent effects such as the cell migration involved in angiogenesis. This signal transduction pathway could represent an accessible and vulnerable target for cancer therapeutic intervention and has the novelty of being located within normal cells rather than tumor cells.
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PMID:Vascular endothelial growth factor stimulates protein kinase C-dependent phospholipase D activity in endothelial cells. 880 65

Colorectal cancer has a high incidence of morbidity and mortality in the North American population. Elevated levels of plasmalogens have been reported in some neoplastic tissues including colon tumors, but the mechanism for this increase has not been defined. Since changes in plasmalogen level are usually associated with changes in the other phospholipid subclasses, a general increase in all phospholipid subclasses may also be found in colonic neoplasms. In this study, the levels of the major phospholipids, including their plasmalogen and diacylphospholipid subclasses, were found to be elevated in human malignant colonic tissues. Since phosphatidylcholine is the most prominent type of phospholipid found in both malignant and control tissues, the mechanism for its accumulation during malignancy was investigated. Decreases in phospholipase C and D activities were observed in tumor samples, but an enhancement of the CTP: phosphocholine cytidylyltransferase activity was also detected. Immunoblotting analysis revealed that the elevated cytidylyltransferase activity was caused by a three-fold increase in the level of enzyme protein during tumor development. Based on these enzyme studies, we conclude that the high level of phosphatidylcholine in colon tumors resulted from a decrease in its turnover and an increase in its expression.
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PMID:The modulation of choline phosphoglyceride metabolism in human colon cancer. 890 31

A number of proteins are found attached to the plasma membrane of mammalian cells by a glycosylphosphatidylinositol (GPI) anchor that can be cleaved by GPI specific phospholipase D (GPI-PLD). There are no known specific inhibitors of GPI-PLD. We examined some inhibitors of phosphatidylinositol specific phospholipase C (PI-PLC) for their ability to inhibit human serum and human bone marrow cell GPI-PLD. Azo analogues of suramin were found to be potent inhibitors of GPI-PLD. One compound had an IC50 of 3.7 microM that was 10-fold lower than the IC50 required to inhibit PI-PLC. The azo suramin analogues inhibited cancer cell growth at concentrations similar to those required to inhibit GPI-PLD, and below concentrations required to inhibit growth factor binding. It is possible that inhibition of cell growth might be related to the ability of the compounds to inhibit GPI-PLD.
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PMID:Inhibition of glycosylphosphatidylinositol (GPI) phospholipase D by suramin-like compounds. 891 44

The objective of the present study was to investigate the effect of membrane fatty acid (FA) composition on the activity of phospholipase C (PLC) in HT-29 human colon cancer cells. The membrane FA composition was altered by supplementing cultured cells with FAs of different composition. The FAs were stearic acid (18:0; SA), gamma linolenic acid (18:3 omega 6; gamma LnA); alpha linolenic acid (18:3 omega 3; alpha LnA;); eicosapentaenoic acid (20:5 omega 3; EPA) and docosahexaenoic acid (22:6 omega 3; DHA). The fatty acids were supplemented as a FA/BSA complex. Cells supplemented with SA served as the control. Tumor growth was followed by counting the number of cells in culture. The results indicate that polyunsaturated fatty acid (PUFA) supplementation had no consistent effect on tumor growth from 1 day to another throughout the 15 days of growth. The fatty acid composition of membranes indicates that cells incorporated and modified the supplemented fatty acids by desaturation, elongation and retroconversion. The unsaturation index (UI) of membranes of cells supplemented with EPA and DHA was higher than other groups. PLC activity; measured in the absence of GTP gamma(S) in the assay mixture; was not influenced by membrane FA modification. However, in the presence of GTP gamma(S) PLC of cells supplemented with 18:3(omega 6) was the lowest among the groups. It has been shown that 18:3(omega 6) accumulated the most in the phosphatidylethanolamine (PE) fraction. There was a negative correlation between the activity of PLC in the presence of G protein activation and PE 18:3 (omega 6) content without affecting UI. It was concluded that G protein may be sensitive to the level of 18:3(omega 6) content and not to the general fluidity of the membranes.
Cancer Lett 1996 Nov 12
PMID:The effect of unsaturated fatty acids on membrane composition and signal transduction in HT-29 human colon cancer cells. 895 Feb 5

Proliferation of thyroid follicular cells is controlled by three intra-cellular cascades [cAMP, inositol 1,4,5-triphosphate (IP3)/Ca2+/diacylglycerol (DAG), and tyrosine kinases] that are activated by distinct extracellular signals and receptors. We had previously generated a transgenic mouse model in which the cAMP cascade was permanently stimulated in thyroid cells by an adenosine A2a receptor (Tg-A2aR model). In the present work, we have generated a transgenic model characterized by the chronic stimulation of both adenylyl cyclase and phospholipase C in thyroid follicular cells. The bovine thyroglobulin gene promoter was used to direct the expression of a constitutively active mutant of the alpha 1B adrenergic receptor, which is known to couple to both cascades in transfected cell lines. The expression of the transgene resulted, as expected, in the activation of phospholipase C and adenylyl cyclase, as demonstrated by the direct measurement of IP3 and cAMP in thyroid tissue. The phenotype resulting from this dual stimulation included growth stimulation, hyperfunction, cell degeneracy attributed to the overproduction of free radicals, and the development of malignant nodules invading the capsule, muscles, and blood vessels. Differentiated metastases were found occasionally in old animals. The development of malignant lesions was more frequent and of earlier onset than in our previous Tg-A2aR model, in which only the cAMP cascade was stimulated. These observations demonstrate that the cAMP and IP3/Ca2+/DAG cascades can cooperate in vivo toward the development of thyroid follicular cell malignancies.
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PMID:Costimulation of adenylyl cyclase and phospholipase C by a mutant alpha 1B-adrenergic receptor transgene promotes malignant transformation of thyroid follicular cells. 897 26

The involvement of phospholipids and especially polyphosphoinositides in cellular signalling has been documented in detail over the last 20 years. Besides the membrane localisation the nucleus also has been show to be a site for both the synthesis and hydrolysis of the phosphorylated forms of phosphatidylinositol. Previous observations dealing with signal transduction have established phospholipase C, specific for inositol lipids (PLC), an important step in the inositol lipid cycle. Of the several known PLC isoforms the type beta 1 is of particular interest because of its reported nuclear localisation, in addition to its presence at the plasma membrane. Indeed, investigations from our laboratory and others have shown the existence in several cell types of an autonomous intranuclear inositide cycle endowed with both conventional lipid kinases and PLC. Moreover, both the stimulation and the inhibition of the nuclear PLC beta 1 under different stimuli implicate this PLC isoform as a key enzyme for mitogen-activated cell growth as well as for differentiation. These findings have prompted us to better characterise the nuclear PLC beta 1. The isoform beta 1 has been studied as a possible target for anti-cancer drugs and as an inducer, via diacylglycerol generation, of the translocation of specific protein kinase C (PKC) isozyme to the nucleus. The chromosome mapping of PLC beta 1 gene has been carried out and the effect of its knock-out by means of antisense cDNA has been determined.
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PMID:Nuclear inositol lipid cycle: a new central intermediary in signal transduction. 904 1

The purpose of this study was to elucidate the behavior of signal transduction activity in rat and human carcinoma cells. Signal transduction activity was measured by the steady-state activity of the three enzymes involved in the conversion of 1-phosphatidylinositol (PI) to IP3, PI 4-kinase, PI 4-phosphate 5-kinase, and phospholipase C activities were measured by our methods. The results indicate that the steady-state activities of the three signal transduction enzymes and the end-product, IP3, were up-regulated in a transformation- and progression-linked fashion. In rat liver PI kinase, PIP kinase and PLC activities were 0.4, O.04, and 800 nmol/hour/mg protein, respectively. PI and PIP kinase and PLC activities were increased 2- to 8-fold in five rat hepatomas and 29-, 45-, and 4-fold, respectively, in rapidly growing hepatoma 3924A. PI and PIP kinase activities as compared to normal ovary were elevated in human ovarian epithelial carcinomas (4- and 3-fold) and in OVCAR-5 cells in culture (31- and 11-fold). Compared to normal breast parenchymal cells, PI and PIP kinase activities were increased in human breast carcinoma cells (96- and 16-fold). When breast carcinoma cells were plated and expressed their neoplastic proliferative program. IP3 concentration increased 20-fold in early log phase: PI and PIP kinase activities increased 11-fold in mid log phase: PLC activity did not change throughout. PI and PIP kinase activities in bone marrow had short half-lives (t1/2 = 8 minutes) but PLC had a long one (t1/2 > 6 hours). The elevated signal transduction activity was down-regulated by the anti-cancer drug, tiazofurin, and also by quercetin, an inhibitor of PI kinase. The addition of these drugs to cultured carcinoma cells reduced the IP3 concentration, and the cells were killed. These integrated studies are the first showing that signal transduction activity is stringently linked with transformation and progression in rat and human solid tumors and carcinoma cells. Down-regulation (by tiazofurin) or inhibition of PI and PIP kinase activities (by quercetin) in human carcinoma cells led to a marked reduction of IP3 concentration and to cell death. Tiazofurin and quercetin may be useful in the treatment of carcinomas with increased signal transduction capacity.
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PMID:Increased signal transduction activity and down-regulation in human cancer cells. 904

The antiestrogen tamoxifen is widely used for endocrine therapy of breast cancer; however, the mechanisms of estrogen receptor-independent interactions of tamoxifen remain ill defined. Here we examine the effect of tamoxifen on the initial steps of cell signal transduction. To this end, phospholipid metabolism and protein kinase C (PKC) translocation were assessed in CCD986SK human mammary fibroblasts treated with tamoxifen. The addition of tamoxifen resulted in dose-dependent and time-dependent increases in the cellular second messengers phosphatidate (PA) and diacylglycerol (DG). On addition of ethanol to the medium, tamoxifen induced the formation of phosphatidylethanol, demonstrating that tamoxifen activates phospholipase D (PLD). Cellular DG also increased in the presence of ethanol, showing that tamoxifen also activates phospholipase C (PLC). In cells prelabeled with choline and ethanolamine, tamoxifen caused increases in choline, phosphorylcholine, ethanolamine and phosphorylethanolamine. Structure-activity relationship studies for activation of PLD revealed that tamoxifen was the most effective, whereas 4-hydroxy tamoxifen was nearly devoid of activity. Phorbol diesters also activated PLD, but estrogen had no influence. Pretreatment of cells with phorbol dibutyrate (PKC down-regulation protocol) blocked phorbol diester- and tamoxifen-induced PLD activity. Exposure of cells to the PKC inhibitor GF 109203X diminished tamoxifen-induced PLD activity. Addition of tamoxifen to cultures elicited selective membrane association of PKC epsilon. We conclude that tamoxifen exerts considerable extra-nuclear influence at the transmembrane signaling level. These events may contribute to effects beyond the scope of estrogen receptor-dependent actions.
Int J Cancer 1997 Mar 04
PMID:Tamoxifen activates cellular phospholipase C and D and elicits protein kinase C translocation. 905 57


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