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:3.1.4.3 (phospholipase C)
18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mastoparan, a basic tetradecapeptide isolated from wasp venom, is a novel mitogen for Swiss 3T3 cells. This peptide induced DNA synthesis in synergy with insulin in a concentration-dependent manner; half-maximum and maximum responses were achieved at 14 and 17 microM, respectively. Mastoparan also stimulated DNA synthesis in the presence of other growth promoting factors including bombesin, insulin-like growth factor-1, and platelet-derived growth factor. The synergistic mitogenic stimulation by mastoparan can be dissociated from activation of phospholipase C. Mastoparan did not stimulate phosphoinositide breakdown, Ca2+ mobilization or protein kinase C-mediated phosphorylation of a major cellular substrate or transmodulation of the epidermal growth factor receptor. In contrast, mastoparan stimulated arachidonic acid release, prostaglandin E2 production, and enhanced cAMP accumulation in the presence of forskolin. These responses were inhibited by prior treatment with pertussis toxin. Hence, mastoparan stimulates arachidonic acid release via a pertussis toxin-sensitive G protein in Swiss 3T3 cells. Arachidonic acid, like mastoparan, stimulated DNA synthesis in the presence of insulin. The ability of mastoparan to stimulate mitogenesis was reduced by pertussis toxin treatment. These results demonstrate, for the first time, that mastoparan stimulates reinitiation of DNA synthesis in Swiss 3T3 cells and indicate that this peptide may be a useful probe to elucidate signal transduction mechanisms in mitogenesis.
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PMID:Mastoparan, a novel mitogen for Swiss 3T3 cells, stimulates pertussis toxin-sensitive arachidonic acid release without inositol phosphate accumulation. 170 71

To ascertain whether mannose 6-phosphate affects insulin-like growth factor (IGF) II stimulation of phospholipase C activity in the basolateral membrane of the renal proximal tubular cell, we determined the effect of mannose 6-phosphate on IGF II-stimulated production of inositol trisphosphate (Ins-P3) in isolated basolateral membranes. Production of Ins-P3 measured in the presence of 10(-10), 10(-9), or 10(-8) M rat IGF II was potentiated approximately 2-fold by inclusion of 5 mM mannose 6-phosphate in incubations. Mannose 6-phosphate had no effect on Ins-P3 production in the absence of IGF II. Neither mannose 1-phosphate, mannose, glucose 6-phosphate, nor fructose 1-phosphate exerted similar potentiation. Enhancement of IGF II-stimulated Ins-P3 production required concentrations on the order of several millimolar mannose 6-phosphate. Total and specific binding of 10(-10) M 125I-IGF II to basolateral membranes was significantly increased by 5 mM mannose 6-phosphate. However, there was no significant effect on total or specific binding of 10(-9) or 10(-8) M 125I-IGF II. Our findings suggest that mannose 6-phosphate potentiates stimulation of phospholipase C by IGF II in the basolateral membrane of the renal proximal tubular cell and that potentiation is mediated via a mechanism in addition to enhanced binding of IGF II. Such potentiation could reflect a role for the mannose 6-phosphate moiety as a modulator of IGF II "signal" transmission in vivo.
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PMID:Mannose 6-phosphate potentiates insulin-like growth factor II-stimulated inositol trisphosphate production in proximal tubular basolateral membranes. 278 38

We have previously shown that lactogenic hormones stimulate epidermal growth factor (EGF) mRNA accumulation in mouse mammary glands in vivo and in mouse mammary epithelial cells (NMuMG line). However, our in vitro studies indicate that the lactogenic hormone prolactin (PRL) completely inhibits EGF-stimulated DNA synthesis. PRL does not alter cholera toxin or insulin-like growth factor-1-stimulated cell growth, thus the inhibition appears to be specific for EGF. Our current studies are designed to evaluate the effects of PRL on EGF-stimulated signaling events in the NMuMG cell line. Cells treated with PRL for 30 min demonstrated a loss of high affinity EGF-binding ability. After long-term PRL treatment (18 h) there was a decrease in EGF receptor (R) number, as determined by [125I]EGF binding. PRL treatment (8 h) also decreased EGF-R mRNA levels. An EGF-stimulated increase in EGF-R mRNA observed 2-4 h after treatment was decreased when PRL was added to the cultures. Furthermore, levels of EGF-stimulated tyrosine phosphorylation of the EGF-R (170 kDa) and phospholipase C gamma (145 kDa) are dramatically decreased in cells treated with PRL. Also of great interest was a decrease in EGF-stimulated c-myc mRNA in PRL-treated cells. We conclude that PRL is acting to down-regulate the EGF-R, thus limiting EGF-stimulated cell signaling in mammary tissue.
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PMID:Prolactin inhibits epidermal growth factor (EGF)-stimulated signaling events in mouse mammary epithelial cells by altering EGF receptor function. 824 65

Insulin-like growth factor II (IGF II)/mannose 6-phosphate (Man-6-P) receptor, which has two binding sites, was efficiently purified using a phospho-pentamannan affinity column. The molecular mass of the receptor purified from rat fibrosarcoma cells (KMT-17) was 240,000 (240K), whereas that of the receptor from normal rat liver and fibroblasts (NRK-49F) was 250K. However, when the receptor was subjected to deglycosylation by treatment with tunicamycin, the receptors of the KMT-17 and MRK-49F cells gave the same molecular mass of 225K, indicating that the difference in molecular mass between two cell lines resulted from the different oligosaccharide sizes. Analysis of the number of receptor site and binding affinity with IGF II on cell surface showed that KMT-17 cells expressed about 10 times more sites than in NRK-49F cells, whereas the binding affinity of KMT cells was lower than that of NRK-49F cells. Since it is known that asparagine-linked oligosaccharides in the IGF II/Man-6-P receptor are essential for IGF II binding, the types of oligosaccharides in the receptor were investigated by concanavalin A affinity chromatography. It was revealed that a ratio (38%) of tetra- and triantennary (multiantennary) complex-type oligosaccharides in the receptor of KMT-17 cells was lower than that (61%) in NRK-49F cells. These results indicate that the receptor of KMT-17 cells possesses predominantly less branched complex-type oligosaccharides and that multiantennary complex-type oligosaccharides of the receptor are most likely to contribute to higher affinity binding of IGF II. To determine whether IGF II activates phosphatidyl inositol-specific phospholipase C (PLC) in KMT-17 cells, the production of inositol trisphosphate (IP3) was measured. Treatment with IGF II increased the level of IP3 in a concentration-dependent manner. The level of IP3 reached the maximum after 15 seconds of incubation. When the cells were pretreated with anti-receptor antibody, no activation of the PLC was observed. These findings suggest that IGF II stimulates PLC through binding to the IGF II/Man-6-P receptor.
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PMID:[Insulin-like growth factor II/mannose-6 phosphate receptors in a rat fibrosarcoma cell line]. 831 38

In the current study, endothelin-1 (ET-1) worked as a mitogen on Chinese hamster ovary cells stably expressing human endothelinA; when applied to serum-deprived cells, ET-1 caused dose-dependent increase in [3H]thymidine incorporation and cell proliferation. No synergism was observed between the effect of ET-1 and that of insulin-like growth factor-1/basic fibroblast growth factor. Both the inhibition of intracellular Ca2+ response by phospholipase C inhibitor U73122 and the down-regulation of protein kinase C (PKC) by pretreatment with phorbol 12-myristate-13-acetate (PMA) partially blocked the ET-1-induced mitogenic responses. Wortmannin, a phosphatidylinositol-3-kinase inhibitor, caused dose-dependent inhibition of the ET-1-induced mitogenic responses in both PMA-treated and -untreated cells. Wortmannin also inhibited ET-1-induced increase in phosphatidylinositol trisphosphate formation and activation of mitogen-activated protein kinase (MAPK), whereas it failed to inhibit PMA-induced activation of MAPK. In accordance with its effect on MAPK activation, wortmannin inhibited ET-1-induced activation of Raf-B, whereas it failed to inhibit the effect of PMA. These results suggested the role of a Ca2+/PKC-independent, wortmannin-sensitive signaling pathway that linked ETA and MAPK cascade in the mitogenic signaling activated by ETA.
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PMID:Endothelin-1-induced mitogenic responses of Chinese hamster ovary cells expressing human endothelinA: the role of a wortmannin-sensitive signaling pathway. 864 84

The intracellular effects of bradykinin are mediated through the recently cloned B2 kinin receptor which belongs to the superfamily of receptors with seven transmembrane domains. The molecular events which transduce the bradykinin signal on the post-receptor level are not understood in detail. We studied whether in human foreskin fibroblasts bradykinin treatment induces tyrosine phosphorylation of cellular proteins. Using phosphotyrosine antibodies we detected a bradykinin-dependent phosphorylation of a group of proteins of about 130 kDa and an additional signal around 70kDa after starvation of cells. The effect evoked by 10 nM bradykinin was rapid (2 min) and it was partially reduced by the B2-kinin-receptor antagonist Hoe 140 which was shown to be a weak inducer of tyrosine phosphorylation. The bradykinin-mediated tyrosine phosphorylation events were reproduced in human embryonal kidney 293 fibroblasts which were transiently transfected with the rat B2 kinin receptor, but they were not observed in untransfected 293 control cells. These data suggest that the B2 kinin-receptor subtype is involved. Upon fractionation of cells the 130kDa protein group was recovered both in the membrane and the cytosolic protein fraction. To assess the specificity of this bradykinin effect we stimulated human foreskin fibroblasts with epidermal growth factor (EGF), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF-I) and insulin. While IGF-I, insulin and EGF were almost ineffective, PDGF stimulated the tyrosine phosphorylation of 130-kDa bands with a similar pattern to that produced by bradykinin. Immunoprecipitation experiments with specific antibodies against potential candidate proteins in the molecular-mass range around 130kDa revealed positive results for the focal adhesion kinase FAK and the p130 Src substrate while negative results were obtained for the GTPase-activating protein GAP, the phospholipase C-gamma1, the Janus kinase JAK-1 and vinculin. The data suggest that the tyrosine phosphorylation of FAK and the pl30 Src substrate might be involved in the B2-kinin-receptor signalling cascade.
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PMID:Bradykinin induces tyrosine phosphorylation in human foreskin fibroblasts and 293 cells transfected with rat B2 kinin receptor. 866 18

Glycosyl phosphatidylinositols have been implicated in insulin signaling through their action as precursors of second messenger molecules in peripheral tissues. In the present study, cultured rat astrocytes were used to investigate whether glycosyl phosphatidylinositol might be involved in the mechanism of insulin signal transduction in neural cells. A glycosyl phosphatidylinositol sensitive to hydrolysis by both phosphatidylinositol-specific phospholipase C and glycosyl phosphatidylinositol-specific phospholipase D and to nitrous acid deamination was purified. When astrocytes were exposed to 10 nM insulin, a rapid and significant reduction in the content of glycosyl phosphatidylinositol was observed within 1-2 min. In addition, an inverse concentration-dependent relationship between glycosyl phosphatidylinositol and diacylglycerol levels was found, suggesting a phospholipase C-mediated hydrolysis of glycosyl phosphatidylinositol in response to insulin. The effects of insulin were mediated through its own receptors and not through insulin-like growth factor (IGF)-I and/or IGF-II receptors, as demonstrated by affinity cross-linking studies. Also, the effects of 5 nM IGF-1 or 5 nM IGF-II on glycosyl phosphatidylinositol and diacylglycerol levels were different from those caused by insulin and were not essentially modified by pretreatment of the cells with either platelet-derived growth factor (PDGF) or epidermal growth factor (EGF). When cells were sequentially incubated with PDGF and EGF, a reduction in both glycosyl phosphatidylinositol and diacylglycerol contents was observed; the diacylglycerol but not the glycosyl phosphatidyl content was reversed after incubation with IGF-I, and especially with IGF-II, for 10 min. Despite the remarkable homology among insulin, IGF-I, and IGF-II, our results indicate that in astrocytes these compounds probably use different signal transduction pathways.
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PMID:Insulin promotes the hydrolysis of a glycosyl phosphatidylinositol in cultured rat astroglial cells. 897 4

The neurotrophins are signaling factors that are essential for survival and differentiation of distinct neuronal populations during the development and regeneration of the nervous system. The long-term effects of neurotrophins have been studied in detail, but little is known about their acute effects on neuronal activity. Here we use permeabilized whole-cell patch clamp to demonstrate that neurotrophin-3 (NT-3) and nerve growth factor activate calcium-dependent, paxilline-sensitive potassium channels (BK channels) in cortical neurons. Application of NT-3 or nerve growth factor produced a rapid and gradual rise in BK current that was sustained for 30-50 min; brain-derived neurotrophic factor, ciliary neurotrophic factor, and insulin-like growth factor-1 had no significant effect. The response to NT-3 was blocked by inhibitors of protein kinases, phospholipase C, and serine/threonine protein phosphatase 1 and 2a. Omission of Ca2+ from the extracellular medium prevented the NT-3 effect. Our results indicate that NT-3 stimulates BK channel activity in cortical neurons through a signaling pathway that involves Trk tyrosine kinase, phospholipase C, and protein dephosphorylation and is calcium-dependent. Activation of BK channels may be a major mechanism by which neurotrophins acutely regulate neuronal activity.
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PMID:Activation of calcium-dependent potassium channels in mouse [correction of rat] brain neurons by neurotrophin-3 and nerve growth factor. 902 72

Results from several laboratories have established the existence in the nucleus of an autonomous polyphosphoinositide cycle, which is involved in both cell proliferation and differentiation. A key step of intranuclear polyphosphoinositide metabolism is the phospholipase C-mediated generation of diacylglycerol (DAG). In insulin-like growth factor (IGF)-I-stimulated Swiss 3T3 cells, a transient elevation of intranuclear DAG levels is essential for attracting the alpha isoform of protein kinase C (PKC) to the nucleus. Previous evidence has shown that the nucleus also contains DAG kinase, i.e., the enzyme that yields phosphatidic acid from DAG, thus terminating PKC-mediated signaling events. Here we show that IGF-I treatment of quiescent Swiss 3T3 cells results in the stimulation of nuclear DAG kinase activity. Time course analysis showed an inverse relationship between nuclear DAG mass and DAG kinase activity levels. After IGF-I treatment, maximal enhancement of DAG kinase activity was measured in the internal matrix domain of the nucleus. PKC-alpha remained within the nuclear compartment, even when nuclear DAG mass returned to basal levels. This was conceivably due to interactions with specific nuclear PKC-binding proteins, some of which were identified as lamins A, B, and C and protein C23/nucleolin. Treatment of cells with two DAG kinase inhibitors, R59022 and R59949, blocked the IGF-I-dependent rise in nuclear DAG kinase activity and maintained elevated intranuclear levels of DAG. The two inhibitors also markedly potentiated the mitogenic effect of IGF-I. These results suggest that nuclear DAG kinase plays a key role in regulating the levels of DAG present in the nucleus and that DAG is a key molecule for the mitogenic effect that IGF-I exerts on Swiss 3T3 cells.
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PMID:Enhanced nuclear diacylglycerol kinase activity in response to a mitogenic stimulation of quiescent Swiss 3T3 cells with insulin-like growth factor I. 1070 86

Phospholipase C-gamma1, a tyrosine kinase substrate, hydrolyses phosphatidylinositol 4,5-bisphosphate to produce inositol 1,4,5-trisphosphate and diacylglycerol, which act as second messenger moleculesto mobilize intracellular calcium and activate protein kinase C, respectively. We have investigated the role of phospholipase C-gamma1 in anoikis, or cell death, induced by the loss of extracellular matrix adhesion. Spontaneously immortalized mouse embryonic fibroblasts nullizygous at the Plcg1 locus (Plcg1(-/-)), referred to as Null cells, were derived from targeted gene disruption experiments. Subsequently, phospholipase C-gamma1 was re-expressed in these cells to derive Null+ cells. The Null and Null+ cells were then placed in suspension to induce cell death, which was measured directly as well as by the induction of caspase 3, as an index of programmed cell death or apoptosis. The results demonstrate that insulin-like growth factor can rescue Null+ cells but not Null cells from suspension-induced cell death. This demonstrates that phospholipase C-gamma1 is required for insulin-like growth factor dependent cell survival under these conditions. Lastly, the data demonstrate that insulinlike growth factor stimulated tyrosine phosphorylation of phospholipase C-gamma1 in both adherent and suspension cells.
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PMID:PLC-gamma1 is required for IGF-I protection from cell death induced by loss of extracellular matrix adhesion. 1197 63


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