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)

The mechanism of cAMP regulation of the respiratory burst was studied with HL-60 cells that had been DMSO-differentiated to a neutrophil-like cell. To evaluate the effects of known cAMP concentrations, cells were permeabilized with streptolysin-O. Chemotactic peptide (FMLP)-stimulated NADPH oxidase activity was inhibited by cAMP at concentrations higher than 3 microM. Because intracellular calcium was buffered, inhibitory actions of cAMP were not mediated by modulation of calcium concentration. Effects of cAMP on chemotactic peptide signal transduction mediated by phospholipase C, phospholipase D, and phospholipase A2 were then determined. Neither inositol phosphate generation (phospholipase C) nor phosphatidylethanol generation (phospholipase D activity in presence of 1.6% ethanol) induced by FMLP were significantly affected by cAMP. In contrast, cAMP potently inhibited FMLP-induced arachidonic acid mobilization (phospholipase A2). NADPH oxidase activity induced by exogenous arachidonic acid was not inhibited by cAMP. These results indicate that cAMP-mediated inhibition of arachidonic acid mobilization may be important in regulation of the respiratory burst.
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PMID:Regulation of the respiratory burst by cyclic 3',5'-AMP, an association with inhibition of arachidonic acid release. 133 10

Membranes prepared from DMSO-differentiated HL60 cells labeled with [3H]inositol hydrolyze polyphosphoinositides in a Ca2+-dependent manner, generating inositol 1,4-bisphosphate (IP2) and inositol 1,4,5-trisphosphate (IP3). Incubation of membranes with GTP or GTP gamma S reduces the concentration of Ca2+ required for activation. This nucleotide effect is potentiated by formyl-Met-Leu-Phe (FMLP). Pertussis toxin inhibits FMLP-induced augmentation, but not the induction of IP2/IP3 formation by GTP or GTP gamma S. These results suggest that differentiated HL60 cells contain a membrane-associated phospholipase C that degrades polyphosphoinositides and that activation of this enzyme is mediated by at least two guanine nucleotide binding proteins, one of which is linked to FMLP receptors and is pertussis toxin sensitive.
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PMID:Chemotactic peptide, calcium and guanine nucleotide regulation of phospholipase C activity in membranes from DMSO-differentiated HL60 cells. 303 41

The effects of diacylglycerols and phospholipase C on dimethylsulfoxide (DMSO)-induced differentiation were investigated in Friend erythroleukemic cells (FELC). Greater than 80% of cells become benzidine-positive when incubated with 1.5% DMSO. The tumor promoter, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), inhibits DMSO-induced differentiation in FELC. Diacylglycerols were found to inhibit DMSO-induced differentiation dose responsively with the order of potency being 1-oleoyl-2-acetylglycerol (OAG) greater than dicaprylin greater than dilaurin greater than diolein. Phospholipase C which releases endogenous diacylglycerols from membrane phospholipids also inhibited DMSO-induced differentiation dose responsively. These results support the hypothesis that diacylglycerols can have effects similar to tumor promoters and suggest that protein kinase C may be a common mechanism for tumor promotion.
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PMID:Inhibition of dimethylsulfoxide-induced differentiation in Friend erythroleukemic cells by diacylglycerols and phospholipase C. 659 1

The human leukaemic cell line K562 is a pluripotent stem cell with the potential to mature along a megakaryocytic or erythroid line. In these cells, thrombin and U46619 (9,11-dideoxy-9 alpha, 11 alpha-methanoepoxy prostaglandin F2 alpha), a thromboxane A2 analogue, increased intracellular Ca2+ in a rapid and concentration-dependent manner. The peak transient observed with both thrombin and U46619 was preserved upon stimulation in the absence of extracellular calcium and blunted with phorbol myristate acetate, suggestive of activation of phospholipase C. Short-term treatment with leupeptin abolished the calcium response to thrombin, but did not alter that to U46619. Both pertussis toxin (PT) and DMSO pretreatment inhibited thrombin- but not U46619-stimulated intracellular calcium elevation, indicating that these agonists signal through different G-proteins. Western blot analysis of crude membranes from K562 cells revealed the presence of G12 alpha and G13 alpha; the other known PT-substrates, Gi1 alpha and G0 alpha, were not detected. Consistent with this observation, ADP-ribosylation experiments revealed the presence of two PT substrates which co-migrated with human erythrocyte G12 alpha and G13 alpha. An antibody raised against Gq/11 alpha, a subfamily of G-protein alpha subunits unmodified by PT, specifically recognized 42 kDa protein(s) in K562 cells. PCR amplification of reverse-transcribed K562 RNA followed by DNA sequencing showed that these cells express messages for both Gq alpha and G11 alpha. Treatment of K562 cells with DMSO reduced the levels of thrombin receptor mRNA, without simultaneous changes in the expression of G12 alpha and G13 alpha. We have thus identified Ca(2+)-mobilizing agonists and related G-proteins in K562 cells, together with changes induced by DMSO in this signalling pathway.
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PMID:Ca2+ signalling in K562 human erythroleukaemia cells: effect of dimethyl sulphoxide and role of G-proteins in thrombin- and thromboxane A2-activated pathways. 749 5

The intracellular localizations of phosphatidylinositol 4,5-bisphosphate (PIP2) and of its hydrolyzing enzyme phospholipase C (PLC; in this case the beta 1 isoform) have been evaluated by electron microscope immunocytochemistry in cells exposed to mitogenic or differentiating agents. These cells have been previously demonstrated to present a signal transduction system based on the polyphosphoinositide hydrolysis localized at the nuclear level, which can be specifically modulated by agonists. The results demonstrate that in Swiss 3T3 mouse fibroblasts mitogenically stimulated by insulin-like growth factor I (IGF-I), a rapid and transient decrease of the PIP2 detectable by immunogold labeling occurs at the nuclear interior. This effect appears due to the activation of the PLC beta 1 isozyme already present in the nucleus, since no significant variations of the enzyme amount and distribution can be detected by immunolabeling. However, after 30 min of exposure to IGF-I, when the PLC beta 1 activity is returned to basal level, a slight but significant increase of the enzyme amount is detected both in the nucleus and in the cytoplasm. On the other hand, an increased accumulation of PIP2 in the nucleus, accompanied by a decrease of the intranuclear amount of PLC beta 1 isozyme, have been observed in mouse erythroleukemia Friend cells, induced to erythroid differentiation by dimethylsulfoxide (DMSO). These results indicate that quantitative immunocytochemistry represents an increment in the available methodologies to investigate the complex regulation of nuclear PI-signalling.
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PMID:Immunocytochemical detection of the intranuclear variations of phosphatidylinositol 4,5-bisphosphate amount associated with changes of activity and amount of phospholipase C beta 1 in cells exposed to mitogenic or differentiating agonists. 754 15

We have studied the effect of dexamethasone on the granulocytic differentiation of the human promyelocytic cell line HL-60 induced by treatment with retinoic acid (RA) or dimethyl sulphoxide (DMSO). Dexamethasone potentiated the immunophenotypic and functional parameters associated with the granulocytic differentiation induced by RA, including changes in CD11b and CD71 expression, inhibition of cell proliferation, enhancement of secretory and oxidative responses and increase of the phospholipase C (PLC), phospholipase A2 (PLA2) and phospholipase D (PLD) activities. However, dexamethasone had selective effects on several parameters of DMSO-induced cell differentiation. Dexamethasone inhibited the DMSO-induced increase of CD11b cell surface expression as well as the oxidative response and PLD activation triggered by 4 beta-phorbol 12-myristate 13-acetate. Nevertheless, dexamethasone potentiated the receptor-mediated PLC activation and the receptor-mediated secretory and oxidative responses in DMSO-treated cells. Unlike RA-treated HL-60 cells, the DMSO-treated cells contained high values of activatable PLA2 activity which were not affected by dexamethasone. Thus dexamethasone affected differently functional parameters and effector systems of granulocytic HL-60 cells, depending on the differentiation agent used. Dexamethasone by itself did not induce HL-60 cell differentiation, but enhanced the receptor- and non-receptor-mediated secretory responses and induced the appearance of stimulated PLA2 activity in undifferentiated HL-60 cells. These data provide evidence for the selective modulation of functional responses by dexamethasone through alterations in signalling processes.
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PMID:Dexamethasone modifies the functional responses of the granulocytic differentiating HL-60 cells. 790 61

Recent findings indicate that ischemia/reperfusion (IR) is associated with phospholipase C (PLC)-induced inositol 1,4,5-triphosphate production, as well as abnormal sarcoplasmic reticulum (SR) Ca2+ release. Therefore, we hypothesized that increased SR Ca2+ release may contribute to Ca2+ overload and myocardial stunning. Neomycin (NEO) was used to inhibit PLC, and sodium dantrolene (DAN) was used to inhibit myocardial SR Ca2+ release. The purposes of this study were (1) to determine if PLC inhibition would reduce IR-induced ventricular dysfunction, (2) to examine ventricular function during inhibition of SR Ca2+ release prior to ischemia, and (3) to examine the influence of SR Ca2+ release inhibition on post-IR ventricular function. Left ventricular developed pressure (DP) and +/- dP/dt of isolated crystalloid perfused rat heart (Langendorff apparatus) paced at 350 bpm were compared before and after global IR (38 degrees C, 20 min I, 40 min R) to assess functional recovery. PLC was inhibited with NEO (10 microM x 5 min prior to ischemia), and SR Ca2+ release was retarded with DAN (12.5 microM) in 0.05% DMSO (vehicle) infused for 3 min via the aortic cannula 13 min prior to ischemia. No effect on DP was observed during NEO or DAN infusion. NEO and DAN pretreatment each improved recovery of DP (% recovery +/- SEM) following IR: control, 46.5 +/- 5.1%; NEO + IR, 71.0 +/- 6.3%,* vehicle + IR, 44.4 +/- 2.9%; DAN + IR, 71.0 +/- 4.7%, *, # (*P < 0.05 vs control IR, #P < 0.05 vs vehicle + IR, ANOVA, Scheffe F test, n = 5 all groups). We conclude that SR Ca2+ release during IR contributes to myocardial stunning.
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PMID:Inhibition of sarcoplasmic reticulum calcium release reduces myocardial stunning. 836 Nov 66

In an earlier study, we presented evidence to suggest that some of the particulate choline-O-acetyltransferase (ChAT) in rat hippocampal tissue might be linked to membranes by a glycosyl-phosphatidylinositol (GPI) anchor. In the present report, we attempted to determine if any of this GPI-anchored ChAT might be intracellular. Internalization of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis into rat hippocampal synaptosomes by the DMSO (dimethyl sulfoxide) freeze/thawing procedure caused an increase in cytosolic and a decrease in membrane-bound ChAT. Incubation of a plasma membrane enriched subcellular fraction at 16 degrees C relative to 4 degrees C led to a conversion of the membrane-bound, amphiphilic ChAT into hydrophilic ChAT. This conversion was blocked by zinc, an inhibitor of GPI-PLC. The cytosolic fraction of ChAT immunoreacted on western blots with an antibody directed against the cross-reacting determinant (CRD) of the GPI anchor. We suggest that some of the membrane-bound ChAT in rat hippocampal tissue is GPI-anchored intracellularly; also, that an endogenous GPI-PLC-like enzyme acts to release it into the cytosol.
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PMID:Membrane-bound choline-O-acetyltransferase in rat hippocampal tissue is anchored by glycosyl-phosphatidylinositol. 846 84

Friend erythroleukemia cells have a nuclear phosphoinositide cycle which is related to both mitogen-stimulated cell growth and erythorid differentiation. Because of the important role of the phosphatidylinositol-transfer protein (PI-TP) in phosphatidylinositol 4,5-bisphosphate (PtdInsP2) synthesis, we have analysed nuclei isolated from Friend cells for the presence of PI-TP. By Western Blotting it was demonstrated that both intact nuclei and nuclei deprived of the outer membrane contained the PI-TP alpha isoform. Upon induction of erythroid differentiation by DMSO, the amount of nuclear PI-TP alpha was greatly diminished. As shown previously, under these same conditions, nuclear phospholipase C beta1 (PLC beta1) is down-regulated as well.
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PMID:Phosphoinositide signalling in nuclei of Friend cells: DMSO-induced differentiation reduces the association of phosphatidylinositol-transfer protein with the nucleus. 901 71

The effects of free radicals, generated by electrolysis of a physiological salt solution, on various inotropic responses to drugs in isolated rat left atria were studied. Evidence for the generation of hydroxyl radicals was obtained from an appropriate fluorimetric assay. The amount of free radicals produced by electrolysis of the medium proved current-dependent. Exposure of isolated rat left atria to the medium which had been subjected to electrolysis caused a current-dependent decrease in contractile force. Oxidative stress, as a result of the electrolysis of the medium, caused altered inotropic responses to extra cellular Ca2+ (pD2 control group: 2.62 +/- 0.06 vs. 2.44 +/- 0.07 electrolysis group), sodium withdrawal (rise in contractile force control group: 1.73 +/- 0.19 mN vs. 0.48 +/- 0.21 mN electrolysis group) and lowering of stimulation frequency. The response to isoprenaline was diminished in atria subjected to oxidative stress and led to a rightward shift of the concentration response curves (pD2 control group: 7.56 +/- 0.10 vs. 6.77 +/- 0.11 electrolysis group). In addition, the inotropic responses to forskolin (pD2 control group: 6.17 +/- 0.12 vs. < 4.5 electrolysis group) and dibutyryl cAMP (rise in contractile force caused by 1 x 10(-5) M db-cAMP in control group: 2.15 +/- 0.01 mN vs. 1.21 +/- 0.10 mN electrolysis group) proved blunted as well. Measurement of the adenylyl cyclase activity revealed that free radicals attenuated the basal (by 11.1%) and forskolin stimulated (155.0 +/- 5.1 vs. 48.0 +/- 1.8 pmol cAMP/mg prot./min for control and electrolysis group respectively) activity of the adenylyl cyclase. DMSO, a well known hydroxyl radical scavenger, was able to abolish the free radical-induced decrease in the response to isoprenaline. Surprisingly, addition of alpha-adrenoceptor agonists to atria subjected to electrolysis-generated free radicals led to a rapid decrease in contractile force. DMSO was unable to counteract the negative intropic effect of methoxamine in atria subjected to oxidative stress. This negative inotropic response to alpha-adrenoceptor agonists in atria subjected to electrolysed medium is unlikely to be the direct result of phospholipase C or protein kinase C activation. Angiotensin II (which stimulates PLC, as well) did not reduce contractile force and chelerythrine (a PKC inhibitor) was unable to counteract the negative inotropic effect of the adrenoceptor agonists. In addition, the negative inotropic effect of methoxamine proved insensitive to 10(-6) M phentolamine and 10(-5) M doxazosin, which indicates an alpha-adrenoceptor independent mechanism. From this study we conclude that free radicals alter responses to various inotropic stimuli. These alterations may be the result of injured contractile elements, transporter molecules and molecules involved in signal transduction. Addition of alpha-adrenoceptor agonists after oxidative stress leads to a alpha-adrenoceptor. PLC and PKC independent decrease in contractile force.
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PMID:The influence of oxidative stress on various inotropic responses in isolated rat left atria. 908 71


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