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)

Two glycoinositol phospholipids (GIPL A and GIPL B) have been purified from epimastigotes of Trypanosoma cruzi at the logarithmic phase of growth (2 days). The GIPLs differ mainly in the lipid moiety and are similar to the lipopeptidophosphoglycan (LPPG) previously isolated from epimastigotes at the stationary phase (4-5 days). [3H]-palmitic acid was incorporated into 1-O-hexadecyl-2-O-palmitoylglycerol in GIPL A and into a sphinganine ceramide with palmitic acid and lignoceric acid as the fatty acids in GIPL B. The lipids could be released by incubation with phosphatidylinositol-specific phospholipase C (PI-PLC) or glycosylphosphatidylinositol phospholipase D (GPI-PLD) from rat serum. The oligosaccharides share the common core structure of the glycosylphosphatidylinositol (GPI) membrane anchors. Microheterogeneity was demonstrated, as well as substitution by galactose, which is mainly in the furanose configuration as was previously described for the LPPG. However, methylation analysis indicated that 20% of the galactose is present as terminal pyranose units. In infective trypomastigotes, [3H]-palmitic acid was incorporated into the anchor of the Tc-85 glycoprotein. The lipid cleaved by phospholipase C digestion was identified as 1-O-hexadecylglycerol and the main oligosaccharide has the structure of the conserved core of all GPI anchors. [3H]-palmitic acid-labelled Tc-85 released into the culture medium as membrane vesicles showed 80% resistance to the action of PI-PLC. However, after mild alkaline hydrolysis, part of the radioactivity was released by the enzyme.
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PMID:Free and protein-linked glycoinositolphospholipids in Trypanosoma cruzi. 808 Dec 36

In ram spermatozoa, treatment with the ionophore A23187 and Ca2+ led to an increase in total diacylglycerol mass and to exocytosis of the acrosomal granule. If sperm cells were prelabeled with [3H]palmitic acid, stimulation with A23187/Ca2+ resulted in the generation of [3H]diacylglycerols with a mixture of saturated and unsaturated fatty acids. When cells were prelabeled with 1-O-[3H]octadecylglycerophosphocholine, stimulation led to the generation of [3H]alkylacylglycerol. No rise in [3H]diacyl- or [3H]alkylacylphosphatidic acid was detected under these conditions. Moreover, no changes in the mass of phosphatidic acid have been previously noted under similar conditions. Thus, these results indicate that diradylglycerols are generated via phospholipase C (PLC). Increases in diradylglycerols were paralleled by rises in monoacyl- or monoalkylglycerols labeled at position 1, but not in free [3H]palmitic acid or [3H]octadecanol, implying that, unlike somatic cells, spermatozoa catabolize diradylglycerols via a 2-diglyceride lipase. Activation of PLC appears to be effected by phosphoinositide-derived diacylglycerol: exposure to Mg2+, a cation known to inhibit phosphoinositide hydrolysis, resulted in less PLC activity upon stimulation, and addition of exogenous 1,2-diacylglycerols enhanced the enzyme's activity. However, 1,3-diacylglycerol and alkylacylglycerol also stimulated PLC activity, suggesting that the effect is unlikely to be mediated via protein kinase C. Since diradylglycerols are known to be essential in the molecular sequence leading to membrane fusion in mammalian spermatozoa, these results suggest that their generation via PLC constitutes a fundamental event during acrosomal exocytosis in response to physiological agonists.
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PMID:Polyphosphoinositide-derived diacylglycerol stimulates the hydrolysis of phosphatidylcholine by phospholipase C during exocytosis of the ram sperm acrosome. Effect is not mediated by protein kinase C. 808 26

We examined effects of acute unilateral enucleation on incorporation from blood of intravenously injected unsaturated [1-14C]arachidonic acid ([14C]AA) and [1-14C]docosahexaenoic acid ([14C]DHA), and of saturated [9,10-3H]palmitic acid ([3H]PA), into visual and nonvisual brain areas of awake adult Long-Evans hooded rats. Regional cerebral metabolic rate for glucose (rCMRglc) values also were assessed with 2-deoxy-D-[1-14C]glucose ([14C]DG). One day after unilateral enucleation, an awake rat was placed in a brightly lit visual stimulation box with black and white striped walls, and a radiolabeled fatty acid was infused for 5 min or [14C]DG was injected as a bolus. [14C]DG also was injected in a group of rats kept in the dark for 4 h. Fifteen minutes after starting an infusion of a radiolabeled fatty acid, or 45 min after injecting [14C]DG, the rat was killed and the brain was prepared for quantitative autoradiography. Incorporation coefficients k* of fatty acids, or rCMRglc values, were calculated in homologous brain regions contralateral and ipsilateral to enucleation. As compared with ipsilateral regions, rCMRglc was reduced significantly (by as much as -39%) in contralateral visual areas, including the superior colliculus, lateral geniculate body, and layers I, IV, and V of the primary (striate) and secondary (association, extrastriate) visual cortices. Enucleation did not affect incorporation of [3H]PA into contralateral visual regions, but reduced incorporation of [14C]AA and of [14C]DHA by -18.5 to -2.1%. Percent reductions were correlated with percent reductions in rCMRglc in most but not all regions. No effects were noted at any of nine non-visual structures that were examined. These results indicate that enucleation acutely reduces neuronal activity in contralateral visual areas of the awake rat and that the reductions are coupled to reduced incorporation of unsaturated fatty acids into sn-2 regions of phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine. Reduced fatty acid incorporation likely reflects reduced activity of phospholipases A2 and/or phospholipase C.
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PMID:In vivo cerebral incorporation of radiolabeled fatty acids after acute unilateral orbital enucleation in adult hooded Long-Evans rats. 811 26

The Tc-85 glycoprotein, specific for the infective stage of Trypanosoma cruzi, is anchored via glycosylphosphatidylinositol. The protein was purified from parasites, labeled metabolically with palmitic acid, by immunoprecipitation with the H1A10 monoclonal antibody or by affinity column chromatography on wheat germ agglutinin. Antisera to the soluble form of the variant surface glycoprotein of Trypanosoma brucei brucei cross-reacted with Tc-85 when the immunoprecipitate was analysed by Western blotting. The reaction was intensified upon previous incubation of the glycoprotein with phosphatidylinositol-specific phospholipase C. Such recognition was abolished when the cyclic phosphate was opened by mild acid treatment. The lipid cleaved by phospholipase C digestion, was identified as 1-O-hexadecylglycerol by reverse-phase thin-layer chromatography. The glycan core was deaminated and chemically labeled by reduction with NaB3H4. The labeled glycoprotein was exhaustively treated with pronase and dephosphorylated with 50% HF. Although microheterogeneity of the oligosaccharide moiety was apparent, by thin layer chromatography, a main spot coincident with Man(alpha 1-2) Man(alpha 1-6) Man(alpha 1-4) anhydromannitol was shown, consistent with the conserved core structure of all glycosylphosphatidylinositol anchors analysed to date.
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PMID:The glycosylphosphatidylinositol anchor of the trypomastigote-specific Tc-85 glycoprotein from Trypanosoma cruzi. Metabolic-labeling and structural studies. 822 3

Treatment of [14C]choline- or [14C]ethanolamine-labeled NIH 3T3 fibroblasts with Bacillus cereus phosphatidyl-choline-specific phospholipase C (PLC) enhanced phospholipase D (PLD)-mediated hydrolysis of the respective 14C-labeled phospholipids. PLD activity was stimulated by 1.5 U/mL of PLC and by 100 nM of the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) to similar extents. Treatment of [14C]palmitic acid-labeled fibroblasts with PLC in the presence of ethanol also enhanced PLD-mediated formation of phosphatidylethanol; the effects of PLC and PMA were nonadditive. PLC had no effect on PLD activity in fibroblasts in which PKC was down-regulated by prolonged (24 h) treatment with 300 nM PMA. These data indicate that treatment of fibroblasts with exogenous PLC results in PKC-dependent activation of PLD.
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PMID:Protein kinase C-dependent stimulation of phospholipase D in phospholipase C-treated fibroblasts. 835 74

Oxytocin(OT) is considered to have several activities besides strongly inducing myometrial contraction by activating phosphatidilinositol-specific phospholipase C(PI-PLC). These include reconstructing the phospholipid constituents of the cell membrane and activating a variety of fatty acid producing systems. On the other hand, pregnancy-related steroid hormones which are produced by the fetus, placenta and mother are considered to be closely involved in the maintenance of pregnancy and the initiation of labor. In the present study with cultured myometrial cells, we examined what effect these steroid hormones might exert on the intramyometrial production of fatty acid by OT. Our results confirmed bi-phasic production of arachidonic acid(AA), linoleic acid(LA), palmitic acid(PA), and stearic acid(SA) by OT. Phase 1 was an increasing but transient phenomenon having its peak at 30 sec. It is considered to be derived from phosphatidylinositol bis-phosphate. Phase 2 was a persistent and increasing phenomenon which was initiated after 120 sec. It is considered to be mediated by Ca-dependent phospholipase. We also studied the effect of steroid hormones on the production of fatty acid. For AA, LA, and PA, we confirmed that dehydroepiandrosterone sulfate(DHAS) shortened the time taken in reaching the peak of Phase 1 to half of that of the control, and progesterone(P) extended the time 2-3 fold. These findings suggest that DHAS, P and F might modify the human myometrial construction mechanism as a factor which regulates the quantity and velocity of fatty acid production.
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PMID:[The effect of oxytocin on production of free fatty acid in primary human uterine myometrial cell culture]. 837 Oct 25

The exposure of brain cells to adverse conditions, such as ATP depletion, induces the degradation of membrane phospholipids and the accumulation of free fatty acids. We have investigated the mechanism of membrane breakdown in an in vitro cell injury model. Confluent cells from the human astroglial cell line UC-11MG were treated with sodium iodoacetate to deplete their intracellular ATP. Large amounts of saturated (palmitic acid) and unsaturated (oleic, linoleic and arachidonic acid) free fatty acids as well as diacylglycerols containing prelabeled fatty acids were released from the cells prior to the loss of plasma membrane integrity. The capacity of the cells to reincorporate free fatty acid into membrane phospholipids decreased in parallel with the loss of intracellular ATP, indicating the failure of the acyltransferase pathway. The addition of the phospholipase A2 inhibitors manoalide, mepacrine, or U-26384, or the phospholipase C inhibitor U-73122, reduced the severity of cell injury, but did not maintain cell viability. The addition of a battery of protease inhibitors with or without the phospholipase inhibitors had no protective effect. These results suggest that the activation of phospholipases A2 and C coupled with the loss of the reacylation process lead to the breakdown of membrane components during lethal cell injury.
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PMID:Degradation of membrane phospholipids in the cultured human astroglial cell line UC-11MG during ATP depletion. 846 Oct 44

The signalling mechanisms whereby high-density lipoproteins (HDL) and low-density lipoproteins (LDL) affect a number of cellular functions in fibroblasts are unclear. This study has analyzed the influence of HDL3 and LDL on the phosphatidylinositol specific phospholipase C pathway in human skin fibroblasts. Exposure of myo-[2-3H]-inositol prelabelled fibroblasts to HDL3 or LDL elicited major increases in IP1 and minor increases in IP2 and IP3 within 30 s. In fura-2 loaded suspended fibroblasts, HDL3 and LDL increased intracellular Ca2+ concentrations ([Ca2+]i) with comparable rapid, transient kinetics. The dose-profiles for HDL3- and LDL-induced increases in [Ca2+]i were also comparable, with half-maximally and maximally effective concentrations being approximately 15 micrograms/mL and approximately 50 micrograms/mL, respectively. HDL3- and LDL-induced increases in [Ca2+]i were diminished by approximately 60% (vs. control fibroblasts) in thapsigargin-pretreated fibroblasts, indicating that release of Ca2+ from intracellular pools is the major contributor toward lipoprotein-induced increases in [Ca2+]i. Pertussis toxin-pretreatment of cells completely abolished lipoprotein induced Ca(2+)-transient, indicating the involvement of a guanine nucleotide-binding protein in the signalling process. In [3H]-palmitic acid-prelabelled fibroblasts, both HDL3 and LDL were observed to stimulate production of DAG. Activation of protein kinase C (PKC) was analysed by determining the cytosol-to-membrane translocation of both enzymatic activity and immunoreactivity of specific PKC isoforms (alpha, delta, epsilon, and zeta). Stimulation with HDL3 and LDL evoked a rapid (within 2.5 min) translocation of PKC activity, with PKC alpha and PKC epsilon being the isoforms translocated. It is concluded that HDL3 and LDL acutely stimulate a phosphoinositide-specific phospholipase C pathway in human skin fibroblasts. However, the specific cell membrane events mediating this signal transduction remain to be further elucidated.
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PMID:High-density lipoprotein and low-density lipoprotein-mediated signal transduction in cultured human skin fibroblasts. 851 99

Heat-stable antigen (HSA), expressed by various antigen-presenting cells (APC), has been described as a costimulatory molecule for CD4+ T cells. Recently, we observed that HSA also serves as an important costimulatory molecule on epidermal Langerhans cells (LC). During these studies, low levels of HSA staining were also detected on normal murine keratinocytes (KC). To investigate whether HSA also is involved in T-cell activation by KC, normal murine KC or the spontaneously transformed KC cell-line PAM 212 were treated with PDB or PMA to induce HSA-expression. FACS analyses showed induction of HSA expression on normal murine KC, as well as PAM 212 cells. In functional assays PDB or PMA-treated normal or transformed KC were far more potent inducers of primary allogeneic T-cell responses than untreated KC. Addition of anti-HSA-specific mAb 20C9 specifically inhibited the costimulatory activity of KC, an effect that was even more pronounced when CTLA-4Ig was added to the cultures. Cleavage of HSA on KC surfaces by a phosphoinositol-specific phospholipase C (PI-PLC) also significantly inhibited the costimulatory capacity of KC for naive CD4+ T cells. In aggregate, our data indicate that expression of HSA on activated KC contributes to the capacity of these cells to induce proliferation of allogeneic T cells.
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PMID:Heat-stable antigen is expressed by murine keratinocytes and delivers costimulatory signals in T-cell activation. 858 19

Tc-85, an 85-kDa surface glycoprotein specific for the trypomastigote stage of Trypanosoma cruzi, has been implicated in the invasion of host cells by the parasite. Radioactive palmitic acid was incorporated into Tc-85 immunoprecipitated from the culture medium with the H1A10 monoclonal antibody, suggesting that shedding occurs with Tc-85 bearing its GPI anchor. In contrast to the glycoprotein remaining in the parasites, the glycosylphosphatidylinositol moiety in shed Tc-85 is resistant to phosphatidylinositol phospholipase C and becomes susceptible to the enzyme following alkali treatment. An alkylglycerol was identified by thin layer chromatography of an ether extract after the enzymatic reaction. Resistance to cleavage by phospholipase C is due to fatty acid esterification of the inositol residue in shed Tc-85. This is the first example of inositol modification in anchors from a glycoprotein of Trypanosoma cruzi.
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PMID:Trypanosoma cruzi: the Tc-85 surface glycoprotein shed by trypomastigotes bears a modified glycosylphosphatidylinositol anchor. 863 80


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