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)

Earlier studies demonstrated that dietary omega-3 polyunsaturated fatty acid (PUFA) supplementation attenuates the chemotactic response of neutrophils and the generation of leukotriene (LT) B4 by neutrophils stimulated with calcium ionophore; however, the mechanisms and relationship of these effects were not examined. Neutrophils and monocytes from eight healthy individuals were examined before and after 3 and 10 wk of dietary supplementation with 20 g SuperEPA daily, which provides 9.4 g eicosapentaenoic acid (EPA) and 5 g docosahexaenoic acid. The maximal neutrophil chemotactic response to LTB4, assessed in Boyden microchambers, decreased by 69% after 3 wk and by 93% after 10 wk from prediet values. The formation of [3H]inositol tris-phosphate (IP3) by [3H]inositol-labeled neutrophils stimulated by LTB4 decreased by 71% after 3 wk (0.033 +/- 0.013% [3H] release, mean +/- SEM) and by 90% after 10 wk (0.011 +/- 0.011%) from predict values (0.114 +/- 0.030%) as quantitated by beta-scintillation counting after resolution on HPLC. LTB4-stimulated neutrophil chemotaxis and IP3 formation correlated significantly (P < 0.0001); each response correlated closely and negatively with the EPA content of the neutrophil phosphatidylinositol (PI) pool (P = 0.0003 and P = 0.0005, respectively). Neither the affinities and densities of the high and low affinity LTB4 receptors on neutrophils nor LTB4-mediated diglyceride formation changed appreciably during the study. Similar results were observed in neutrophils activated with platelet-activating factor (PAF). The summed formation of LTB4 plus LTB5 was selectively inhibited in calcium ionophore-stimulated neutrophils and was also inhibited in zymosan-stimulated neutrophils. The inhibition of the summed formation of LTB4 plus LTB5 in calcium ionophore-stimulated neutrophils and in zymosan-stimulated neutrophils did not correlate significantly with the EPA content of the PI pool. The data indicate that dietary omega-3 PUFA supplementation inhibits the autoamplification of the neutrophil inflammatory response by decreasing LTB4 formation through the inactivation of the LTA epoxide hydrolase and independently by inhibiting LTB4- (and PAF) stimulated chemotaxis by attenuating the formation of IP3 by the PI-selective phospholipase C. This is the initial demonstration that dietary omega-3 PUFA supplementation can suppress signal transduction at the level of the PI-specific phospholipase C in humans.
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PMID:Dietary omega-3 polyunsaturated fatty acids inhibit phosphoinositide formation and chemotaxis in neutrophils. 838 24

Phospholipase C isoenzymes can generate different proportions of cyclic and non-cyclic inositol phosphates. Stimulation of [3H]-inositol labeled pancreatic minilobules by buffer, bombesin, neuromedin B or carbachol in presence of 10 mM lithium, followed by separation of inositol phosphates, yielded the following results for cyclic inositol monophosphate (cIP) [DPM/mg protein; Mean +/- SEM (n)]: control [21 +/- 6, (9)]; bombesin [145 +/- 24, (12)]; neuromedin B (99 +/- 22 (9)] and carbachol [512 +/- 60, (12)]. The generation of cIP and IP were significantly correlated [r2 = 0.72 (p < 0.05)] following carbachol activation, while no significant correlation was obtained following bombesin receptor activation by either bombesin or neuromedin B. Presence of zinc (100 microM) in the final incubation medium failed to amplify the bombesin-stimulated cIP accumulation. Based on our studies we postulate that different phospholipase C isoenzymes may be activated following muscarinic and bombesin receptor stimulation in pancrea.
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PMID:Bombesin and muscarinic receptor activation in rat pancreas generate cyclic inositol monophosphate: possible involvement of different phospholipase C isoenzymes. 838 41

The effect of [MgADP] on relaxation from isometric tension, initiated by reducing free [Ca2+] through photolysis of the caged photolabile Ca2+ chelator diazo-2, was determined at 20 degrees C in alpha-toxin permeabilized tonic (rabbit femoral artery, Rf) and phasic (rabbit bladder, Rb) smooth muscle. In Rf, the shape of the relaxation curve was clearly biphasic, consisting of a slow "plateau" phase followed by a monotonic exponential decline with rate constant k. The duration of the plateau (d = 44 +/- 4 s, mean +/- SEM, n = 28) was well correlated (R = 0.92) with the total t1/2 of relaxation that was 66 +/- 3 s (n = 28) in the presence of 20 mM creatine phosphate (CP), and was prolonged in the absence of CP (t1/2 = 83 +/- 3 s, n = 7); addition of 100 microM MgADP further slowed relaxation (t1/2 = 132 +/- 7 s, n = 14). In Rb, a plateau was not detectable and t1/2 (= 15 +/- 2 s, n = 6) was not affected by 100 microM MgADP. In Rf the Q10 between 20 degrees C and 30 degrees C was 4.3 +/- 0.4 for d-1 and 2.8 +/- 0.3 for k (n = 8; p = 0.006). The regulatory myosin light chain (MLC20) in Rf was dephosphorylated at 0.07 +/- 0.02 s-1, from 42 +/- 3% before to 20 +/- 2% after photolysis of diazo-2, reaching basal values at a time when force had fallen by only 40%. We conclude that, in the presence of ATP, as during rigor, the affinity of dephosphorylated cross-bridges for MgADP is significantly higher in tonic than in phasic smooth muscle and contributes to the maintenance of force at low levels of phosphorylation. The MgADP dependence of the post-dephosphorylation phase of relaxation is consistent with its being rate-limited by the slow off-rate of ADP from cross-bridges that were dephosphorylated while in force-generating ADP-bound (AM*D) cross-bridge states. The fourfold faster off-rate of ADP from AM*D in the phasic, Rb, compared to tonic, Rf, smooth muscle is a major determinant of the different kinetics of relaxation in the two types of smooth muscle.
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PMID:The role of MgADP in force maintenance by dephosphorylated cross-bridges in smooth muscle: a flash photolysis study. 859 68

Although protein kinase C (PKC) activation has been shown to inhibit Ca2+ influx in T lymphocytes, the role of PKC on Ca2+ sequestration or extrusion processes has not been fully explored. We examined the effect of CD3 stimulation and PKC activators on cytosolic Ca2+ (Ca2+i) extrusion and 45Ca2+ efflux in human leukemic Jurkat T cells. Treatment of Fura-2 loaded cells with phorbol 12-myristate 13-acetate (PMA) or thymeleatoxin (THYM) resulted in a decrease in Ca2+i both in the presence and absence of extracellular Ca2+, whereas inactive phorbol esters had no effect. PKC activators added at the peak of a Ca2+i transient induced by anti-CD3 mAb, ionomycin or thapsigargin (TG) stimulated the rate and extent of return of Ca2+i to basal levels by 17-53%. PKC stimulation of the Ca2+i decline was not enhanced by the presence of Na+, indicating that PKC activators increase Ca2+ pump activity rather than a Na+/Ca2+ exchange mechanism. As CD3 receptor activation enhanced the Ca2+i decline in TG-treated cells, antigen-mediated activation of phospholipase C (PLC) signaling includes enhanced Ca2+ extrusion at the plasma membrane. The effect of PKC activators on parameters of Ca2+i extrusion were further explored. PMA significantly increased the rate of Ca2+ extrusion in TG-treated cells from 0.28 +/- 0.02 to 0.35 +/- 0.03 s-1 (mean +/- SEM) and stimulated the initial rate of 45Ca2+ efflux by 69% compared to inactive phorbol ester treated cells. The effects of PKC activation on the Ca2+i decline were eliminated by PKC inhibitors, PKC down regulation (24 h PMA pretreatment), ATP-depletion and conditions that inhibited the Ca2+ pump. In contrast, pretreatment of cells with okadaic acid enhanced the PMA-stimulated response. We suggest that Jurkat T cells contain a PKC-sensitive Ca2+ extrusion mechanism likely to be the Ca2+ pump. In lymphocytes, receptor/PLC-linked PKC activation modulates Ca2+i not only by inhibiting Ca2+ influx but also by stimulating plasma membrane Ca2+i extrusion.
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PMID:Protein kinase C modulates cytosolic free calcium by stimulating calcium pump activity in Jurkat T cells. 874 51

Classically, opioids inhibit Ca2+ influx, but recent reports suggest opioids may also stimulate Ca2+ entry. Therefore, we have measured the effect of opioids on intracellular Ca2+ ([Ca2+]i), fluorimetrically, in Fura-2-loaded SH-SY5Y cells. Fentanyl 0.3 mumol litre-1 caused a mean increase in [Ca2+]i of 18.8 (SEM 2.1) nmol litre-1 in some (30.3%) batches of SH-SY5Y cells. In responding cells, the fentanyl-induced increase in [Ca2+]i was dose-dependent, with an EC50 of 0.73 mumol litre-1. This response was naloxone-reversible, and the delta opioid agonist [D-Pen2,5]enkephalin had no effect on [Ca2+]i, suggesting the fentanyl-induced Ca2+ response was entirely mediated by the mu opioid receptor. Fentanyl 0.3 mumol litre-1 increased [Ca2+]i without preactivation of phospholipase C by another agonist, and this was markedly reduced by Ni2+ 2.5 mmol litre-1. These data suggest that mu opioids directly increase [Ca2+]i by stimulating Ca2+ influx in SH-SY5Y cells.
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PMID:Fentanyl increases intracellular Ca2+ concentrations in SH-SY5Y cells. 878 53

The purpose of this study was to visualize muscarinic receptors and their distribution on cardiomyocytes and to examine the effects of muscarinic cholinergic receptor (mACh-R) stimulation with carbachol on phosphatidylcholine hydrolysis. Cardiomyocytes were prepared as primary culture from 7-day-old chick embryo hearts. Cardiomyocytes, grown on cover slips, were labelled with BODIPY PZ, a fluorescent analog of the muscarinic receptor antagonist pirenzepine, and examined with a laser scanning confocal microscope, mACh-R clusters were visualized and were fairly homogeneous in size with diameters ranging from 0.5 to 1.0 micron. The number of receptor clusters per cell was 83.5 +/- 6.8 (mean +/- SEM) and clusters were found at the periphery of the cell. Cardiomyocytes, grown as a monolayer in dishes, were treated with the 10(-4) M carbachol, a mACh-R agonist, and the effects on phosphatidylcholine hydrolysis were ascertained in cells preincubated with [methyl-3H]choline for 18 h. Cells were washed, lysed, and subjected to thin-layer chromatography to separate [3H]choline in various metabolites of phosphatidylcholine. Carbachol significantly (p < 0.05) increased intracellular free choline and decreased cellular phospholipid consistent with phosphatidylcholine hydrolysis. Carbachol increased the amount of [3H]choline that effluxed out of the cardiomyocyte into the medium. Carbachol-induced choline efflux was not prevented by pretreatment with n-butanol, a phospholipase D inhibitor, suggesting that other lipases such as phospholipase C are the major enzyme involved in phosphatidylcholine hydrolysis. Pertussis toxin prevented carbachol-induced choline efflux and the changes in intracellular free choline and phospholipid. An action of carbachol through G proteins was supported by the ability of pertussis toxin to antagonize the carbachol-induced reduction in cAMP generation from isoproterenol. In summary, mACh-Rs, visualized in living cardiomyocytes, were peripheral to the nucleus. Phosphatidylcholine hydrolysis induced by mACh-R stimulation may be a signal transduction pathway for mACh-R in the cardiomyocyte, operating through inhibitory G proteins sensitive to pertussis toxin.
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PMID:Visualization of muscarinic cholinergic receptors on chick cardiomyocytes and their involvement in phosphatidylcholine hydrolysis. 925 Mar 60

The Immunoglobulin (Ig) binding capacity of Toxoplasma gondii tachyzoites was investigated using fluorescence flow-cytometry analysis. Polyclonal mouse, human and rat immunoglobulins without specific anti-Toxoplasma activity bound to parasites in a concentration-dependent manner, saturating them at circulating serum concentrations. The immunoglobulin class and subclass specificity of binding was investigated using irrelevant monoclonal antibodies. IgM, IgA and IgG reacted with the parasite membrane. The attachment of mouse IgM to the parasite surface was hampered by mouse IgG1, IgG2a, IgG2b and IgG3. The binding of mouse IgG was proportionally reduced with increasing concentrations of mouse monoclonal IgM. The binding of murine immunoglobulin was diminished when in presence of human IgG. Purified Fc- but not Fab portions of immunoglobulins, fixed to parasites. Using labelled calibrated beads, the Ig binding capacity of parasites was estimated to be 6900 +/- 500 sites per tachyzoite. The Kd of the T. gondii Fc Receptor (FcR) activity was determined at 1.4 +/- 0.1 microM (mean +/- SEM). Such FcR activity was reduced by phospholipase C, trypsin and pronase treatment of the parasites. These data show a low affinity FcR activity on T. gondii tachyzoites which recognizes Ig of different species and isotypes and is likely supported by a glycosyl-phosphatidylinositol (GPI)-anchored surface protein of the parasite.
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PMID:Identification and characterization of a Fc receptor activity on the Toxoplasma gondii tachyzoite. 949 16

Cytotoxic T lymphocytes (CTLs) that infiltrate the heart are important immune effectors implicated in heart transplant rejection, myocarditis, and other cardiomyopathies. To investigate the mechanism(s) underlying CTL damage to the myocardium through activation of the Fas receptor (Fas/CD95/Apo-1) by the Fas ligand, we explored the interaction between peritoneal exudate CTLs (PELs), derived from perforin gene-knockout (P-/-) mice, and murine ventricular myocytes. Fas expression on isolated ventricular myocytes was demonstrated immunohistochemically. Action potentials, [Ca2+]i transients, and contractions of myocytes conjugated to P-/- PELs or treated with the apoptosis-inducing anti-Fas monoclonal antibody Jo2 were recorded. Action potential characteristics of nonconjugated myocytes and myocytes conjugated with P-/- PELs were, respectively, as follows: Vm, -73.2+/-1.5 and -53.6+/-6.4 mV (mean+/-SEM); action potential amplitude, 117.9+/-3.9 and 74.3+/-21.2 mV; and action potential duration at 80% repolarization, 17+/-6 and 42+/-13 milliseconds (all P<.05). P-/- PELs also induced early and delayed afterdepolarizations as well as arrhythmogenic activity. Diastolic [Ca2+]i increased during the cytocidal interaction with P-/- PELs, from a fluorescence ratio of 0.82+/-0.05 (n=7) to 1.98+/-0.09 (n=13) (P<.05). All of the effects caused by P-/- PELs were reproduced by incubating the myocytes with Jo2. Heparin (50 microg/mL), an antagonist of inositol trisphosphate (IP3)-operated sarcoplasmic reticulum Ca2+ channels, or U-73122 (2 micromol/L), a phospholipase C inhibitor, but not the inactive agonist U-73343, prevented Fas-mediated myocyte dysfunction. Additionally, intracellular application (through the patch pipette) of the active IP3 analogue, inositol 1,4,5-trisphosphate, but not the inactive analogue, inositol 1,3,4-trisphosphate, caused electrophysiological changes resembling those resulting from P-/- PELs and Jo2, suggesting that CTL-induced Fas-based myocyte dysfunction is mediated by IP3. We conclude that a Fas-based perforin-independent mechanism of CTL action can account for the immunopathology seen in the allotransplanted heart, myocarditis, and dilated cardiomyopathy.
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PMID:Fas (CD95/Apo-1)-mediated damage to ventricular myocytes induced by cytotoxic T lymphocytes from perforin-deficient mice: a major role for inositol 1,4,5-trisphosphate. 950 4

It has been shown that platelets from patients suffering from eclampsia are hyporesponsive to stimulation by agonists like thrombin and ADP. Although platelet hyporeactivity contributes to the pathogenesis of the disease process, the cause for this is still not known. Platelet aggregation and secretion are membrane-based phenomena initiated by the processes of cell signalling. Hence, to understand the mechanisms underlying platelet hyporeactivity in eclampsia, membrane microviscosity and activities of the signalling enzymes were measured in human platelets stimulated with thrombin. Membrane fluidity was determined from the steady-state fluorescence anisotropy of diphenylhexatriene incorporated in cell membranes. Activities of phospholipase C and protein kinase C in stimulated platelets were assessed from the extents of phosphatidic acid generation and pleckstrin phosphorylation, respectively. Platelet membrane microviscosity in eclampsia (2.3 +/- 0.2 SEM, n = 5) was significantly lower (P < 0.05) than that in the matched gravid control subjects (3.1 +/- 0.2, n = 4). In eclampsia, generation of phosphatidic acid and phosphorylation of pleckstrin were decreased by 25% (P < 0.05, n = 3) and 35% (P < 0.05, n = 3), respectively, after 60 sec of platelet stimulation. It was concluded that the hyporeactive platelets obtained from eclampsia have more fluid membranes and diminished activities of phospholipase C and protein kinase C. In summary, this study shows that alterations in membrane fluidity and activities of the signalling enzymes (phospholipase C and protein kinase C) may contribute to the diminished platelet responsiveness observed in the eclamptic condition.
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PMID:Platelets from eclampsia patients have reduced membrane microviscosity and lower activities of the signalling enzymes. 959 60

We studied the interactions between platelet-activating factor (PAF) and phospholipase C (PLC) in the modulation of microvascular responses in the hamster cheek pouch using intravital microscopy and computer-assisted image analysis. Changes in arteriolar diameter and in integrated optical intensity (IOI, an index of vascular permeability) were measured. Fluorescein-isothiocyanate-labeled dextran 150 (FITC-Dx 150) served as a tracer for macromolecular transport. 2-Nitro-4-carboxyphenyl N,N-diphenylcarbamate (NCDC) and 1-(6-((17beta-3-methoxyestra-1,3, 5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5,-dione (U-73122), two PLC inhibitors, were applied topically in separate experiments. PAF at 10(-7) M elevated IOI from baseline to a mean +/- SEM value of 70. 7 +/- 8.9 units. Pretreatment with 10(-4) and 10(-5) M NCDC and with U-73122 at 10(-5) and 10(-6) M attenuated the maximal increment in mean IOI (+/-SEM) induced by PAF at 10(-7) M to mean +/- SEM values of 30.6 +/- 6.5, 39.3 +/- 6.0, 12.1 +/- 4.8, and 41.5 +/- 6.0, respectively. The simultaneous vasoconstrictor action of 10(-7) M PAF was expressed as the experimental-to-baseline ratio, with the baseline diameter adjusted to a value of 1. PAF constricted the arterioles to a mean +/- SEM ratio of 0.30 +/- 0.07. Pretreatment with the PLC inhibitors NCDC at 10(-4) and 10(-5) M NCDC and with U-73122 at 10(-5) and 10(-6) M attenuated 10(-7) M PAF-induced vasoconstriction to mean +/- SEM diameter ratios of 0.55 +/- 0.05, 0. 48 +/- 0.06, 0.55 +/- 0.08, and 0.58 +/- 0.06, respectively. Our results demonstrate that PLC is an element of the biochemical pathway involved in PAF modulation of microvascular permeability and in PAF modulation of arteriolar diameter.
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PMID:Platelet-activating factor modulates microvascular dynamics through phospholipase C in the hamster cheek pouch. 1062 66


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