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)

F9 mouse teratocarcinoma and PyS-2 cells in culture incubated with monovalent cations in buffered sucrose solution (0.25 M) can secrete as much as 40% of their total lysosomal enzymes into the medium within 30 min. Longer incubation does not lead to further loss of enzyme, suggesting that only a certain fraction of lysosomes is capable of discharge. The simultaneous presence of sucrose and cation, each at the respective optimal concentrations of 0.25 and 0.15 M, is required for lysosomal discharge (i.e. twice isoosmolarity). The cells remain fully viable. Sodium ions are more effective than lithium and potassium ions, whereas amines and divalent cations are less effective. Other sugars including glucose can replace sucrose to varying extents. Secretion is accompanied by a rapid short-lived rise in the level of cAMP. Forskolin as well as agents that activate G protein such as cholera toxin, AlF4-, and vanadate ions also increase the rate of secretion. Sucrose-Na+ stimulation takes place independently of changes in influx or efflux of calcium ions or changes in the levels of extracellular or free intracellular calcium ions. Neomycin, an inhibitor of phospholipase C, has little effect on secretion. Our results suggest that the secretion observed is mediated by a cAMP-dependent mechanism involving G proteins. Calcium ions and phospholipase C appear to play little or no part in the activation process.
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PMID:Stimulated secretion of lysosomal enzymes by cells in culture. 254 92

A basophilic leukemic cell line from rat (RBL-1) was used to characterize leukotriene D4 (LTD4) receptor-mediated biochemical and pharmacological effects. [3H]LTD4 binding to the plasma membrane enriched preparation was stereo-selective, specific and saturable. Sodium ions and guanine nucleotides specifically regulated [3H]LTD4 binding to the membrane receptors. Leukotriene E4 (LTE4) and high affinity specific antagonists bound to the receptor with a rank-order potency equivalent to that for the LTD4 receptors in guinea pig lung. In the [3]myoinositol labeled RBL-1 cells, LTD4 and LTE4 induced a rapid hydrolysis of [3H]phosphoinositides. The biosynthesis of the [3H]inositol-trisphosphate was rapid and was detectable at 15-sec poststimulation. The biosynthesis of [3H]inositol-monophosphate was stereo-selective and specific and was inhibited specifically by receptor antagonists. In fura-2 loaded RBL-1 cells, LTD4 and LTE4 induced a transient intracellular Ca++ mobilization. Agonist-induced Ca++ mobilization was specific and stereo-selective and was inhibited by specific receptor antagonists. The most (greater than 85%) LTD4-induced immediate response of Ca++ mobilization was from intracellular sources, whereas a small amount (less than 15%) was derived from the extracellular milieu. Both components were stimulated by receptor agonists and inhibited by the receptor antagonists, suggesting that they were regulated by the LTD4 membrane receptors. In addition, the results also suggested that a guanine nucleotide binding protein, insensitive to islet activating protein from Bordetella pertussis (not Gi or Go), was involved in the signal transduction mechanisms for LTD4 receptors in RBL-1 cells. These results suggested that the plasma membrane enriched LTD4 receptor was coupled via an islet activating protein insensitive G protein to a phosphoinositide specific phospholipase C. Agonist binding to the receptor could activate phospholipase C and resulted in phosphoinositide hydrolysis. Diacylglycerol and inositol trisphosphate could function as intracellular messengers that trigger or contribute to calcium mobilization in RBL-1 cells.
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PMID:Leukotriene D4 receptor-mediated phosphoinositol hydrolysis and calcium mobilization in rat basophilic leukemic cells. 284 29

The rat bladder epithelial cell receptors involved in mannose-sensitive adherence of Escherichia coli strains were studied. Sodium metaperiodate and lipase pretreatment of epithelial cells significantly reduced bacterial adherence to cells whereas trypsin and phospholipase C had a marginal or insignificant effect on adherence. Neuraminidase and colominic acid significantly increased adherence, whereas N-acetylneuraminic acid significantly reduced adherence. These data suggest that the rat bladder epithelial cell receptors involved in mannose-sensitive adherence are glycolipids. In addition, the data suggested that sialic acid on bladder epithelial cells acts as a nonspecific inhibitor of adherence, whereas colominic acid, a component of some E. coli K1 capsules, may act as a promoter of adherence.
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PMID:Evidence for a bladder cell glycolipid receptor for Escherichia coli and the effect of neuraminic acid and colominic acid on adherence. 627 93

Fatty acid positional distributions and the fatty acid compositions of diacyl and alkyl acyl analogs of the three major glycerophospholipids of Paramecium tetraurelia were examined. Phosphatidylcholine and the phospho- and phosphonyl ethanolamine glycerolipids were separated into diacyl and alkyl acyl species by thin-layer chromatography after phospholipase C digestion, and acetylation. Phosphatidylcholine and the ethanolamine phosphonolipid were predominantly in the alkyl acyl form and phosphatidylethanolamine was predominantly in the diacyl form. The three major glycerophospholipids were also subjected to hydrolysis by phospholipase A2. Complete and efficient hydrolyses of all three phospholipids were accomplished with the enzyme from porcine pancreas. Sodium tetraborate prevented acyl migration when added to reaction mixtures. Fatty acids released by phospholipase A2 action, and the lysoderivatives were separated by thin-layer chromatography. Fatty acid methyl esters were prepared and analyzed by gas-liquid chromatography. Saturated acids were predominantly at C-1 of diacyl phospholipids. Polyunsaturated fatty acids were mainly at C-2, particularly in the alkyl acyl species. An exception was gamma-linolenate which was a major acid found esterified to C-1 in the three diacyl phospholipids. Identification of this acid at that position supports the idea that in some ciliates there may be an acyltransferase, specific for gamma-linolenate, that esterifies this acid to the glycerophospholipids.
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PMID:Positional distribution of fatty acids in the major glycerophospholipids of Paramecium tetraurelia. 740 Jun 87

Ferricyanide reductase activity of plasma membranes isolated from Ehrlich ascites tumour cells was very sensitive to trypsin treatment. The decreases of activity observed after treatment with different glycosidases suggests that ferricyanide reductase is a glycoprotein. The opposite effects of phospholipase A2 and phospholipase C on the redox activity indicate that the phospholipidic environment plays an important role in the function of ferricyanide reductase. Sodium ions at millimolar concentrations, and some divalent cations at micromolar concentrations (Ca2+, Mg2+, Sr2+, and Mn2+) behaved as stimulators of ferricyanide reductase activity.
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PMID:Characterization of plasma membrane redox activity from Ehrlich cells. 804 92

Endothelial cells possess beta-adrenoceptors linked to adenylate cyclase which may regulate several aspects of endothelial cell function. The potential for this second messenger system to be modulated by protein kinase C activity was investigated. Bovine aortic endothelial cells (BAECs) were cultured in the absence or presence of phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C. Basal and forskolin-, sodium fluoride (NaF)-, and isoproterenol-stimulated adenylate cyclase activity was measured in homogenates from BAECs. beta-adrenoceptor density on membranes from BAECs was measured by 125I-iodocyanopindolol binding. Sodium dodecylsulfate-polyacrylamide gel electrophoresis of immunoprecipitated proteins was used to identify phosphorylated proteins. Pretreatment of BAECs with 100 nM PMA for 30 min increased basal adenylate cyclase activity above control levels, and also increased enzyme activity stimulated by forskolin, NaF, or isoproterenol. Pretreatment of BAECs for 60 min with 100 nM staurosporine, an inhibitor of protein kinase C, prevented the enhancement of adenylate cyclase activity caused by PMA. Treatment of BAECs with PMA did not trigger phosphorylation of the inhibitory guanine nucleotide-binding protein, and there was no change in BAEC beta-adrenoceptor density following PMA pretreatment. Exposure of BAECs to ATP or bradykinin did not mimic the effects of phorbol ester. In conclusion, activation of protein kinase C by PMA enhanced adenylate cyclase activity in BAECs. However, ATP and bradykinin which activate endothelial cell surface receptors linked to phospholipase C did not mimic this effect.
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PMID:Phorbol ester enhances activation of adenylate cyclase in bovine aortic endothelial cells. 827 22

Fusion of mouse melanoma cells grown in monolayers has been directly monitored by fluorescence resonance energy transfer between fluorescein and rhodamine probes attached to octadecanoic acid. Various poly(ethylene glycol)s (PEG), either alone or in combination with amphipathic molecules, have been used as fusogens. Fusion starts at a maximum rate as soon as PEG is removed from the medium and reaches a plateau after 20-30 min. Both the initial rate and extent of fusion have been recorded for each experiment. The extent of fusion shows in general a positive correlation with the initial rate, although PEGs with different molar masses appear to induce fusion at different rates, but to a similar extent. A good correlation has been found between the extent of fusion, as measured by fluorescence, and the 'fusion index' computed from cell and nucleus counting; a calibration curve is provided for the interconversion of both parameters. Optimum fusion values are obtained with 50% (w/v) PEG 1500. The effect of pre-treatments with surfactants (Triton X-100, sodium dodecylsulphate) on PEG-induced fusion has also been tested. Sodium dodecylsulphate, but not Triton, enhances considerably both the rate and extent of cell fusion. The in situ generation of the amphipathic molecule diacylglycerol, through the catalytic activity of a phospholipase C, also enhances significantly the fusion parameters. These results are in good agreement with previous studies based on syncytia counting.
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PMID:Real-time measurements of chemically-induced membrane fusion in cell monolayers, using a resonance energy transfer method. 829 22

The methyl ester of pyruvic acid (methyl pyruvate) stimulated a dose-dependent increase in insulin secretion from isolated perifused rat islets. The threshold level for release was about 10 mM, and at 20 mM the addition of MP to perifused islets resulted in a large first phase of secretion followed by an insulin-secretory response that was sustained for at least 40 min. When compared to the effects of 20 mM glucose, peak first-phase release rates in response to 20 mM methyl pyruvate were comparable, but the second phase of release was only about 10-15% of that observed with an equimolar level of the hexose. The stimulatory effects of 20 mM methyl pyruvate on secretion were abolished by the K1+-ATP channel blocker diazoxide (200 microM) and by the calcium channel antagonist nitrendipine (500 nM). The glucokinase inhibitor mannoheptulose (20 mM) had no adverse effect on the secretory response to 20 mM methyl pyruvate, whereas 10 microM forskolin amplified the insulinotropic action of MP. Sodium pyruvate alone or in combination with 10 microM forskolin had no insulinotropic effect. In additional experiments islet phosphoinositide pools were labeled with myo-2-[3H]inositol, and the subsequent accumulation of labeled inositol phosphates was used to monitor the activation of phospholipase C. Methyl pyruvate stimulated a dose-dependent increase in inositol phosphate levels when measured after a 30-min incubation period with a maximal increase of about 300% at 20 mM methyl pyruvate. The increase in phosphoinositide hydrolysis caused by methyl pyruvate (20 mM) was, like insulin secretion, reduced by both diazoxide and nitrendipine but was immune to inhibition by mannoheptulose. Pyruvate (20 mM) had no effect on inositol phosphate accumulation. Prior short-term exposure to methyl pyruvate sensitized islets to subsequent stimulation with 15 mM glucose. Sodium pyruvate did not sensitize islets. These findings support the concept that the mitochondrial metabolism of nutrient molecules is an event sufficient to acutely augment insulin release from the beta cell, to increase phospholipase C-mediated phosphoinositide hydrolysis, and to induce time-dependent potentiation of insulin secretion.
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PMID:Influence of pyruvic acid methyl ester on rat pancreatic islets. Effects on insulin secretion, phosphoinositide hydrolysis, and sensitization of the beta cell. 901

Many ion transporters and channels appear to be regulated by ATP-dependent mechanisms when studied in planar bilayers, excised membrane patches, or with whole-cell patch clamp. Protein kinases are obvious candidates to mediate ATP effects, but other mechanisms are also implicated. They include lipid kinases with the generation of phosphatidylinositol phosphates as second messengers, allosteric effects of ATP binding, changes of actin cytoskeleton, and ATP-dependent phospholipases. Phosphatidylinositol-4,5-bisphosphate (PIP2) is a possible membrane-delimited messenger that activates cardiac sodium-calcium exchange, KATP potassium channels, and other inward rectifier potassium channels. Regulation of PIP2 by phospholipase C, lipid phosphatases, and lipid kinases would thus tie surface membrane transport to phosphatidylinositol signaling. Sodium-hydrogen exchange is activated by ATP through a phosphorylation-independent mechanism, whereas ion cotransporters are activated by several protein kinase mechanisms. Ion transport in epithelium may be particularly sensitive to changes of cytoskeleton that are regulated by ATP-dependent cell signaling mechanisms.
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PMID:Cytoplasmic ATP-dependent regulation of ion transporters and channels: mechanisms and messengers. 907 61

Phospholipase C activity has been assayed with phosphatidylcholine as substrate in the presence of sodium cholate at concentrations well below those producing lipid solubilization. With short-chain phosphatidylcholine, which exists in monomeric form in aqueous solution, cholate has little or no effect. However, when the substrate is egg phosphatidylcholine in the form of bilayers, small cholate concentrations (below 1 mM, corresponding to an effective surfactant:lipid ratio below 0.05) increase the maximum enzyme rates by about threefold, while decreasing drastically the latency periods of enzyme activity. Previous studies from this laboratory have associated the phospholipase enhancing activity of a variety of amphiphiles to their ability to facilitate the formation of inverted hexagonal phospholipid structures, yet sodium cholate has the opposite effect, stabilizing the lamellar versus the inverted hexagonal phase. This suggests that cholate is activating phospholipase C through a hitherto undescribed mechanism. Sodium cholate concentrations above 1 mM decrease further the enzyme lag time, but they are less effective in enhancing enzyme rates. These observations may be pertinent in the analysis of biochemical data with purified lipases, as well as in physiological studies of biliary function. Copyright 1999 Academic Press.
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PMID:Effect of Sublytic Concentrations of Sodium Cholate on Phospholipase C Hydrolysis of Phospholipid Bilayers. 1052 83


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