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)

The activation of GTP-binding proteins (G-proteins) by sodium fluoride + aluminum (AlF4-) was shown in several cell free systems. In the intact cell, NaF +/- aluminum was shown to activate various signal transduction pathways and indirect evidence is in line with effector mechanisms involving regulation of G-protein activity. We have explored the effect of NaF on several components of signal transduction pathways in macrophages. NaF was shown to reduce intracellular ATP levels and to suppress agonist-induced protein tyrosine phosphorylation and reactive oxygen species formation. NaF led to in situ activation of nitrogen activated protein kinase, phospholipase A2 and PtdIns-phospholipase C. Addition of AlCl(3) or deferoxamine, a chelator of aluminum, had little or no effect on NaF mediated enzyme activation. The results suggest that at least some of the pleiotropic effects of NaF in intact cells may not be mediated by G-protein activation but rather by depletion of ATP which is essential for protein phosphorylation reactions.
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PMID:A pleiotropic effect of fluoride on signal transduction in macrophages: is it mediated by GPT-binding proteins? 856 81

The purpose of these studies was to examine the sensitivity of the PIP 2-PLC-transducing pathway (GPLC) and its relationship to the respiratory burst in human polymorphonuclear leukocytes (PMN) stimulated by IL-8, TNF-alpha, or IL-1 beta during sequential changes in buffer oxygen tension from normoxia (pO2 = 180-200 mm Hg), to hypoxia (pO2 < 30 mm Hg) and then reoxygenation (pO2 > 140 mm Hg). Our specific hypothesis was that altered oxygen tensions would regulate the G PLC pathway in human PMN. G PLC activity was assayed by investigating phospholipase C activity by measuring inositol phosphates and diacylglycerol (DAG) formation. Respiratory burst activity was assayed as O 2 production and NADPH oxidase activation in intact PMN and in a cell-free system, respectively, and correlated separately to both early and late DAG production. At 1 min, DAG formation during normoxia was decreased by IL-8 plus fibronectin while hypoxia had no regulatory effect on control of DAG formation by any of the cytokines. In contrast to early DAG formation, hypoxia significantly downregulated late DAG formation induced by buffer without fibronectin, IL-8 plus fibronectin, and IL-1 beta with or without fibronectin. Hypoxia/reoxygenation in and of itself significantly increased DAG formation vs levels seen in the presence or absence of IL-8, TNF-alpha, or IL-1 beta with or without fibronectin. Changes in early DAG production during the alterations in oxygen tension correlated best with corresponding changes in O 2 production in intact cells, whereas late DAG production correlated best with NADPH oxidase activation assayed in the cell-free system. Thus, changes in oxygen tension can directly modulate the extent of the PMN response to stimulation by IL-8, TNF-alpha, or IL-1 beta and the G PLC-receptor pathway is particularly regulated by physiologically relevant periods of hypoxia/reoxygenation.
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PMID:Altered oxygen tension modulates cytokine-induced signal transduction in polymorphonuclear leukocytes: regulation of the G PLC pathway. 860 6

Previously, we have shown that Pseudomonas aeruginosa lipase and phospholipase C (PLC), two extracellular lipolytic enzymes, interact with each other during 12-hydroxyeicosatetraenoic acid (HETE) generation from human platelets. In this regard. the addition of purified P. aeruginosa lipase to PLC-containing crude P. aeruginosa culture supernatants enhances the generation of the chemotactically active 12-HETE from human platelets. Therefore, we analyzed the interaction of purified P. aeruginosa lipase and purified hemolytic P. aeruginosa PLC with regard to inflammatory mediator release from human platelets, neutrophilic and basophilic granulocytes, and monocytes. Purified P. aeruginosa PLC, but not purified lipase by itself, induced 12-HETE generation from human platelets, the generation of leukotriene B4 (LTB4) and oxygen metabolites, enzyme release from human neutrophils, and histamine release from basophils but diminished interleukin-8 (IL-8) release from human monocytes in a dose-dependent manner. The addition of purified lipase enhanced PLC-induced 12-HETE and LTB4 generation, did not influence enzyme, histamine, or IL-8 release, but diminished the PLC-induced chemiluminescent response. Similar results were obtained when the hemolytic PLC from Clostridium perfringens was used instead of P. aeruginosa PLC. For further comparison, we used the well-defined calcium ionophore A23187 and phorbol-12-myristate-13-acetate (PMA) as stimuli. Lipase enhanced calcium ionophore-induced LTB4 generation and beta-glucuronidase release but reduced calcium ionophore-induced and PMA-induced chemiluminescence. In parallel, we analyzed the role of lipase in a crude P. aeruginosa culture supernatant containing PLC and lipase. Lipase activity in the P. aeruginosa culture supernatant was inhibited by treatment with the lipase-specific inhibitor hexadecylsulfonyl fluoride, leaving the activity of PLC unaffected. The capacity of "lipase-inactivated culture supernatant" to induce 12-HETE and LTB4 generation was diminished by 50 to 100%. Our results suggest that the simultaneous secretion of lipase and PLC by P. aeruginosa residing in an infected host may result in severe pathological effects which cannot be explained by the sole action of the individual virulence factor on inflammatory effector cells.
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PMID:Role of Pseudomonas aeruginosa lipase in inflammatory mediator release from human inflammatory effector cells (platelets, granulocytes, and monocytes. 875 61

The ability to produce phosphatidylcholine phospholipase C (lecithinase) is associated with virulence in pathogenic species of Listeria. Levels of production vary greatly among members of the genus, and this virulence factor is not readily detectable in many members of the pathogenic species on conventional agar media containing egg yolk, a common substrate for the enzyme. In this study, the influence of a variety of environmental parameters, including temperature, pH, and salt concentration, on the production of lecithinase by a number of strains was evaluated. Lecithinase production by Listeria monocytogenes LO28 in brain heart infusion medium was optimal at 1.75 to 2.0% NaCl; pH 7.0 to 7.3, and 37 to 40 degrees C, and the presence of oxygen had no effect. In a chemically defined medium, the optimal NaCl concentration and temperature were lower at 0.75 to 1.0% NaCl and 33.5 degrees C. As detection of virulence factors is useful to assist in the identification and differentiation of Listeria species, this report shows that lecithinase activity can conveniently be detected within 36 h on a relatively inexpensive medium. Under the conditions described, L. monocytogenes could be distinguished from other members of the genus as a result of distinct lecithin degradation which was not evident in L. innocua, L. seeligeri, L. ivanovii, L. welshimeri, or L. murrayi/grayi.
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PMID:Influence of environmental parameters on phosphatidylcholine phospholipase C production in Listeria monocytogenes: a convenient method to differentiate L. monocytogenes from other Listeria species. 891 85

Reactive oxygen species (ROS) have been implicated in the pathogenesis of a wide variety of respiratory diseases. We investigated mechanisms of ROS-induced mucin secretion by guinea pig tracheal epithelial (GPTE) cells in primary culture, and ROS-induced activation of the second messenger-producing enzyme phospholipase C (PLC), in GPTE cells and in a virally transformed cell line (BEAS-2B) derived from human bronchial epithelium. Mucin secretion was measured by a monoclonal antibody-based enzyme-linked immunosorbent assay, and PLC activation was assessed by anion exchange chromatography. ROS generated enzymatically by xanthine oxidase (XO, 500 microM) in the presence of purine (500 microM) enhanced release of mucin by GPTE cells and activated PLC in GPTE and BEAS cells. Hypersecretion of mucin and activation of PLC in response to purine + XO appeared to occur via an intracellular pathway(s) dependent on endogenously produced nitric oxide and possibly intracellularly generated oxidants. Both responses could be blocked or attenuated by preincubation of the cells with NG-monomethyl-L-arginine, an inhibitor of the enzyme nitric oxide synthase, or with dimethylthiourea, a compound that can react with a variety of intracellular oxidant species. Reactive nitrogen species generated chemically also stimulated secretion of mucin and activated PLC via a mechanism dependent (at least in part) on intracellular oxidant-mediated process(es). The results suggest that intracellularly generated radical species of nitrogen and oxygen may be important modulators of the response of airway epithelial cells to external oxidant stress.
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PMID:Oxidant stress stimulates mucin secretion and PLC in airway epithelium via a nitric oxide-dependent mechanism. 894 30

Eosinophilic and neutrophilic granulocytes represent major effector cells in the inflammatory response. Whereas neutrophils are predominantly involved in bacterial infections, eosinophils are of essential importance in the allergic inflammation. Surface markers have been used to distinguish neutrophils (CD16+) from eosinophils (CD16-) and might indicate different functional properties of these cells. In this study, expression and functional activity of CD52 on human eosinophils and neutrophils was investigated in nonatopic healthy donors and from patients with hypereosinophilia. Flow cytometric analysis using different anti-CD52 monoclonal antibodies (MoAbs) (mouse IgG3, humanized IgG1, and rat IgM) showed significant and homogeneous expression of CD52 on human eosinophils, but not on neutrophils. In addition, reverse transcription-polymerase chain reaction and Northern blot analysis showed that CD52 mRNA was constitutively expressed in eosinophils but not in neutrophils. Furthermore, expression of CD52 could be diminished in a dose-dependent manner by preincubation of eosinophils with phosphatidylinositol-specific phospholipase C, suggesting that CD52 on eosinophils is anchored to the membrane through a glycosylphosphatidylinositol (GPI) molecule. Whereas the phorbolester phorbol myristate acetate was able to downregulate the expression of CD52 on eosinophils in a dose-dependent manner, different eosinophil activating cytokines and chemotaxins had no effect. Cross-linking of CD52 by mouse anti-CD52 MoAb (IgG3) and humanized anti-CD52 MoAb (IgG1) with goat antimouse antibody and mouse antihuman antibody, respectively, dose-dependently resulted in an inhibition of reactive oxygen species production of eosinophils after stimulation with C5a, platelet-activating factor, and granulocyte-macrophage colony-stimulating factor. In summary, this study shows that the GPI-anchored antigen CD52 is not only a useful marker to distinguish eosinophils from neutrophils. The data point out a novel role of the CD52 antigen on human eosinophils that might be of clinical relevance, because cross-linking of this molecule will stop the destructive power of human eosinophils in the inflammatory tissue.
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PMID:Surface and mRNA expression of the CD52 antigen by human eosinophils but not by neutrophils. 897 62

Recent evidence indicates that reactive oxygen species (ROS) may function as intracellular messengers in receptor signaling pathways. The possible role of ROS in epidermal growth factor (EGF) signaling was therefore investigated. Stimulation of A431 human epidermoid carcinoma cells with EGF resulted in a transient increase in the intracellular concentration of ROS, measured with the oxidation-sensitive fluorescent probe 2',7'-dichlorofluorescin diacetate and laser-scanning confocal microscopy. The predominant ROS produced appeared to be H2O2, because the EGF-induced increase in fluorescence was completely abolished by incorporation of catalase into the cells by electroporation. The elimination of H2O2 by catalase also inhibited the EGF-induced tyrosine phosphorylation of various cellular proteins including the EGF receptor and phospholipase C-gamma1. The dependence of H2O2 production on the intrinsic tyrosine kinase activity of the EGF receptor and the autophosphorylation sites located in its COOH-terminal tail was investigated. EGF failed to induce H2O2 generation in cells expressing a kinase-inactive EGF receptor. However, normal H2O2 generation was observed in cells expressing a mutant receptor from which the 126 COOH-terminal amino acids had been deleted to remove four (out of the total of five) autophosphorylation sites. These results suggest that EGF-induced H2O2 formation requires the kinase activity but probably not the autophosphorylation sites of the EGF receptor and that inhibition of protein tyrosine phosphatase activity by H2O2 may be required for EGF-induced protein tyrosine phosphorylation to be manifested.
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PMID:Epidermal growth factor (EGF)-induced generation of hydrogen peroxide. Role in EGF receptor-mediated tyrosine phosphorylation. 899 50

Two principal pathways of Ca2+ release from the sarcoplasmic reticulum of excitable and non-excitable cells have been described: one pathway dependent on the second messenger D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), and a second pathway sensitive to Ca2+ and regulated by caffeine and ryanodine. It was found that the Ca(2+)-pump activity of vascular smooth muscle sarcoplasmic reticulum is inhibited by superoxide anion radicals (O2.-); however, the effects of reactive oxygen intermediates on sarcoplasmic reticulum Ca2+ release in vascular muscle cells are not well defined. The purpose of the present study was to evaluate the effects of reactive oxygen intermediates generated from the hypoxanthine/xanthine oxidase reaction system on contractions induced by caffeine, Ins(1,4,5)P3 and norepinephrine in staphylococcal alpha-toxin-permeabilized rabbit mesenteric arteries. This system generates O2.-, H2O2, and hydroxyl radicals. We wished to identify which class of reactive oxygen intermediates is responsible for the associated loss of vascular smooth muscle contractile function. Caffeine and Ins(1,4,5)P3 produced a transient contraction when the sarcoplasmic reticulum of the permeabilized, preparations was preloaded with pCa 7.0 solution for 5 min before washing with 0.5 mM EGTA solution; norepinephrine also produced a transient contraction. Exposure of the preparations to hypoxanthine/xanthine oxidase (for 30 min) attenuated caffeine-induced contraction, but was without effect on Ins(1,4,5)P3-induced contraction. The observed effect of hypoxanthine/xanthine oxidase exposure was superoxide dismutase-inhibitable, suggesting O2.- involvement. Hypoxanthine/xanthine oxidase also inhibited norepinephrine-induced contraction. The effect of hypoxanthine/xanthine oxidase on norepinephrine contraction was protected by catalase, but not by superoxide dismutase and dimethyl sulfoxide; exogenously added H2O2 mimicked the effect of hypoxanthine/xanthine oxidase exposure. H2O2, added exogenously, was without effect on Ins(1,4,5)P3-induced contraction. It is suggested that the pathway of Ca2+ release from the sarcoplasmic reticulum dependent on Ins(1,4,5)P3 is insensitive to O2.-. Instead, caffeine-induced Ca2+ release mechanisms may be susceptible to O2.- and H2O2, rather than O2.- and hydroxyl radicals, may be the active agent in the norepinephrine-induced contraction. Our results are also consistent with the view that the attenuation by H2O2 of the norepinephrine-induced contraction may be linked to the receptor-associated pathway of Ins(1,4,5)P3 formation, but not to degradation processes of Ins(1,4,5)P3.
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PMID:Susceptibility of caffeine- and Ins(1,4,5)P3-induced contractions to oxidants in permeabilized vascular smooth muscle. 904 2

The primary objective of this study was to determine the influence of stretch-induced cell injury on the metabolism of cellular phosphatidylcholine (PC). Neonatal rat astrocytes were grown to confluency in Silastic-bottomed tissue culture wells in medium that was usually supplemented with 10 microM unlabeled arachidonate. Cell injury was produced by stretching (5-10 mm) the Silastic membrane with a 50-ms pulse of compressed air. Stretch-induced cell injury increased the incorporation of [3H]choline into PC in an incubation time- and stretch magnitude-dependent manner. PC biosynthesis was increased three- to fourfold between 1.5 and 4.5 h after injury and returned to control levels by 24 h postinjury. Stretch-induced cell injury also increased the activity of several enzymes involved in the hydrolysis [phospholipase A2 (EC 3.1.1.4) and C (PLC; EC 3.1.4.3)] and biosynthesis [phosphocholine cytidylyltransferase (PCT; EC 2.7.7.15)] of PC. Stretch-induced increases in PC biosynthesis and PCT activity correlated well (r = 0.983) and were significantly reduced by pretreating (1 h) the cells with an iron chelator (deferoxamine) or scavengers of reactive oxygen species such as superoxide dismutase and catalase. The stretch-dependent increase in PC biosynthesis was also reduced by antioxidants (vitamin E, vitamin E succinate, vitamin E phosphate, melatonin, and n-acetylcysteine). Arachidonate-enriched cells were more susceptible to stretch-induced injury because lactate dehydrogenase release and PC biosynthesis were significantly less in non-arachidonate-enriched cells. In summary, the data suggest that stretch-induced cell injury is (a) a result of an increase in the cellular level of hydroxyl radicals produced by an iron-catalyzed Haber-Weiss reaction, (b) due in part to the interaction of oxyradicals with the polyunsaturated fatty acids of cellular phospholipids such as PC, and (c) reversible as long as the cell's membrane repair functions (PC hydrolysis and biosynthesis) are sufficient to repair injured membranes. These results suggest that stretch-induced cell injury in vitro may mimic in part experimental traumatic brain injury in vivo because alterations in cellular PC biosynthesis and PLC activity are similar in both models. Therefore, this in vitro model of stretch-induced injury may supplement or be a reasonable alternative to some in vivo models of brain injury for determining the mechanisms by which traumatic cell injury results in cell dysfunction.
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PMID:Alterations in phosphatidylcholine metabolism of stretch-injured cultured rat astrocytes. 910 16

Excitotoxicity has been proposed to contribute to neuronal loss in a broad spectrum of neurodegenerative conditions such as ischemia, hypoglycaemic coma or cerebral trauma. Excitotoxic neuronal injury appears to be mediated mainly by the over-activation of glutamate receptors, especially N-methyl-D-aspartate receptors, with subsequent excessive Ca2+ influx. Concurrent with the activation of glutamate-gated ion channels, metabotropic glutamate receptors (mGluR), which are G-protein coupled receptors, are also expected to be activated. Excessive stimulation of phospholipase C-coupled mGluR, mGluR1 and mGluRS, has been suggested to have neurotoxic consequences. However, the contribution of mGluR activation on excitotoxicity is still unclear and controversial. Here we report that, following ischemic and excitotoxic brain injuries, inactivation of mGluR1 does not prevent excitotoxic neuronal damage. Given the evidence that agonists at this group of mGluR promoted neuronal death in cerebrocortical cultures after oxygen-glucose deprivation or after N-methyl-D-aspartate exposure, our findings suggest that mGluR-mediated excitotoxicity is unlikely associated with mGluR1 but rather with other PLC-coupled mGluR.
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PMID:Evidence against a permissive role of the metabotropic glutamate receptor 1 in acute excitotoxicity. 917 62


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