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 structural effects of in situ production of diacylglycerol by phospholipase C in pure lipid model membranes have been examined by freeze fracture electron microscopy. Phospholipase C-activity induces massive aggregation and fusion of large unilamellar lipid vesicles and leads to the formation of a 'sealed' lipid aggregate; the outer membrane of this aggregate appears to be continuous. In some areas lipid arranges into a honeycomb structure; this structure is probably a precursor of a discontinuous inverted (type II) cubic phase. Similarly, enzyme treatment of multilamellar vesicles leads to extensive membrane fusion and vesiculation. Thus morphological evidence is obtained showing the ability of phospholipase C to induce bilayer destabilization and fusion. It is speculated that phospholipase C-induced membrane fusion involves a type II fusion intermediate induced by diacylglycerol produced locally.
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PMID:Phospholipase C activity-induced fusion of pure lipid model membranes. A freeze fracture study. 191 34

The making and sealing of a tight junction (TJ) requires cell-cell contacts and Ca2+, and can be gauged through the development of transepithelial electrical resistance (TER) and the accumulation of ZO-1 peptide at the cell borders. We observe that pertussis toxin increases TER, while AIF3 and carbamil choline (carbachol) inhibit it, and 5-guanylylimidodiphosphate (GTPTs) blocks the development of a cell border pattern of ZO-1, suggesting that G-proteins are involved. Phospholipase C (PLC) and protein kinase C (PKC) probably participate in these processes since (i) activation of PLC by thyrotropin-1 releasing hormone increases TER, and its inhibition by neomycin blocks the development of this resistance; (ii) 1,2-dioctanoylglycerol, an activator of PKC, stimulates TER development, while polymyxin B and 1-(5-isoquinoline sulfonyl)-2-methyl-piperazine dihydrochloride (H7), which inhibit this enzyme, abolish TER. Addition of 3-isobutyl-1-methyl-xanthine, dB-cAMP or forskolin do not enhance the value of TER, but have just the opposite effect. Trifluoperazine and calmidazoline inhibit TER development, suggesting that calmodulin (CaM) also plays a role in junction formation. These results indicate that junction formation may be controlled by a network of reactions where G-proteins, phospholipase C, adenylate cyclase, protein kinase C and CaM are involved.
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PMID:Assembly and sealing of tight junctions: possible participation of G-proteins, phospholipase C, protein kinase C and calmodulin. 192 Mar 85

When cultured in the presence of fetal calf serum, arterial smooth muscle cells from spontaneously hypertensive rats (SHR) proliferate more rapidly and are more numerous at confluency than cells from normotensive Wistar-Kyoto (WKY) animals. The phenomenon has been demonstrated in several laboratories but its molecular origin remains unclear. On the other hand phospholipase C activation and c-fos transcription are early events able to trigger cell mitosis. Therefore, the enhancement of inositol phosphates formation induced in SHR cells by various vasoactive agents and growth factors suggests that this enzyme might be implicated in the abnormal proliferation triggered by serum. In this case a unique molecular abnormality would be responsible for both arterial hypercontractility and dystrophy encountered in hypertension. In order to test this hypothesis we have compared DNA replication, phospholipase C activation, and c-jun and c-fos nuclear protooncogene transcriptions stimulated by fetal calf serum (FCS), vasoactive agents (angiotensin II and vasopressin), and epithelial growth factor (EGF) in SHR and WKY rat cells. The results obtained with these various agonists tested under the same experimental conditions confirm that the classical pathogenic diagram: (PLC hyperactivation----increase in c-fos transcription----enhanced cell proliferation) may apply to the action of vasoactive agents which are only slightly mitogenic on SHR cells, but not to the very important effect of fetal calf serum. Indeed, FCS stimulated inositol phosphate formation and c-jun and c-fos transcription, but none of these parameters was enhanced in SHR cells. Phospholipase C activation may exert some control upon DNA replication, as its partial inhibition by pertussis toxin coincided with an equivalent decrease in thymidine incorporation. It is, however, not absolutely required for the onset of DNA replication in aortic smooth muscle cells, as shown by the results obtained with EGF under the same experimental conditions. An abnormal molecular reaction different from PLC activation is therefore responsible for the enhanced proliferation of cultured SHR aortic smooth muscle cells, and several cell alterations may concur to the formation of the hypertensive arteriopathy.
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PMID:Hyperactivation of phospholipase C does not support the enhanced proliferation of aortic smooth muscle cells from spontaneously hypertensive rats. 193 Aug 47

This study demonstrates the ability of phospholipase C from Clostridium perfringens to stimulate the generation of platelet-activating factor (PAF-acether) in cultured intestinal epithelial cells (INT 407). Cells were exposed to phospholipase C for up to 60 min, and the content of PAF-acether within the cells and in the extracellular medium was determined. Phospholipase C caused a time-dependent formation of PAF-acether within the cells and also release of PAF-acether to the medium. In contrast, phospholipase C did not affect the cellular acetylhydrolase activity or the ability of the cells to metabolize extracellularly added 14C-PAF-acether. These findings suggest the possibility that intestinal epithelial cells, when stimulated with a naturally occurring intestinal bacterial toxin, generate and release PAF-acether. The possibility that this might contribute to the pathophysiology of inflammatory bowel disease is discussed.
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PMID:Phospholipase C from Clostridium perfringens stimulates formation and release of platelet-activating factor (PAF-acether) in cultured intestinal epithelial cells (INT 407). 194 65

During cellular senescence in vitro, the cells do not respond mitogenically to serum growth factors at high population doubling levels. Phospholipase C activity in low PDL IMR 90 cells showed a 4.7-fold stimulation in response to 10% serum compared to 3.3-fold in high PDL cells when measured in whole cell extracts. Immunoaffinity purified tyrosine phosphorylated protein fraction showed a greater increase (5.2-fold) in phospholipase C activity in low PDL than high PDL cells (2.1-fold) in response to serum. Serum stimulated PLC gamma 1 activity was diminished in high PDL cells. Immunokinase assay of PLC gamma 1 immunoprecipitates from serum stimulated IMR 90 fibroblasts suggested that diminished enzymatic activity in high PDL cells is not due to less receptor coupled tyrosine phosphorylated PLC gamma 1 enzyme. Serum stimulated [3H]thymidine incorporation into DNA declined in parallel with the activity of PLC gamma 1, suggesting that its activation might play significant roles in this in vitro model for cellular senescence.
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PMID:Decline of signal transduction by phospholipase C gamma 1 in IMR 90 human diploid fibroblasts at high population doubling levels. 195 65

Most of the phosphoinositide-specific phospholipase C activity in human amnion at term was found to be attributable to a single isoform (Mr 85,000). Phospholipase C purified from amnion catalyzed the calcium-dependent hydrolysis of both phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate. The high phospholipase C activity of amnion cells isolated at 38-41 weeks of gestation declined greater than 80% during the initial 2-5 days of culture to values characteristic of amnion tissue in early gestation. Activities of phospholipase A2 and phosphatidylinositol synthase remained essentially unaltered during this period of culture. Loss of phospholipase C activity was apparently due neither to the appearance of an inhibitor nor to the loss of an activator and most likely reflected a decrease in the amount of enzyme in amnion cells. Basal production of prostaglandin E2 (PGE2) by amnion cells also declined greatly during the period of loss of phospholipase C activity. Involvement of phospholipase C in the regulation of amnion prostaglandin production was also supported by the finding that the phospholipase C inhibitor, U-73122, potently inhibited amnion cell PGE2 production. In contrast, vasopressin, which appears to stimulate prostaglandin production in amnion cells by a phospholipase C-dependent mechanism, was equipotent in stimulating PGE2 production by amnion cells on Day 2 and Day 5 of culture, even though phospholipase C activity had declined by more than 75%. Furthermore, epidermal growth factor stimulation of PGE2 production by amnion cells appeared to be largely attributable to an increase in prostaglandin H synthase activity and did not involve an increase in phospholipase C activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of the major phosphoinositide-specific phospholipase C of human amnion. 196 96

Phospholipase C (lecithinase or phosphatidylcholine phosphorylase) catalyzes the hydrolysis of lecithin into phosphorylcholine and 1,2-diglyceride. Bacterial production of phospholipase C may damage reproductive tract tissues by both direct and indirect mechanisms. Use of the synthetic substrate p-nitrophenylphosphorylcholine phospholipase C activity was determined in 204 isolates representative of those found in female genital tract. Multiple aerobic (28%) and anaerobic (28%) reproductive tract microorganisms showed phospholipase C activity. Phospholipase C-producing isolates included strains of Bacteroides fragilis, B. bivius, B. thetaiotaomicron, Gardnerella vaginalis, and group B streptococcus. Phospholipase C activity was heterogenous; not all isolates that belong to a particular species showed activity. Phospholipase C production may be a possible virulence factor produced by a number of microflora commonly implicated in various reproductive tract infections or conditions, as well as in some instances of preterm birth.
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PMID:Phospholipase C activity in microorganisms associated with reproductive tract infection. 199 22

Phospholipase C (specific for inositol lipids) is known to be present both in membranes and cytosol. Receptor-mediated activation of this enzyme occurs via a guanine nucleotide regulatory protein (G-protein), designated Gp. We have compared the stimulation of this enzyme by fMet-Leu-Phe via the G-protein in HL60 membranes and in permeabilised cells. fMet-Leu-Phe stimulated phospholipase C in membranes at 2 min and the response was dependent on exogenously added GTP. GTP alone also stimulated phospholipase C activity such that at 10 min the response to fMet-Leu-Phe was minimal. In comparison, the response to fMet-Leu-Phe in permeabilised cells was greater in extent but did not require added GTP. However, it was antagonized by GDP analogues (GDP[beta S] greater than GDP greater than dGDP) and by pertussis toxin pretreatment, indicating that fMet-Leu-Phe-stimulated phospholipase C activity was also mediated via Gp. GTP and its analogue GTP[gamma S] also stimulated phospholipase C and their effects were strictly additive to the stimulation obtained with fMet-Leu-Phe. Such additivity was also observed when two receptor-directed agonists, fMet-Leu-Phe and ATP, were used to stimulate intact cells. It is concluded that (a) the size of the response with fMet-Leu-Phe in membranes is limited by the loss of a component, possibly phospholipase C, and (b) stoichiometry and physical organisation of multiple species of G-proteins and/or phospholipases C may explain the independent nature of phospholipase C activation by fMet-Leu-Phe, ATP and guanine nucleotides.
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PMID:Characterization of fMet-Leu-Phe-stimulated phospholipase C in streptolysin-O-permeabilised cells. 201 14

The activity of phospholipase A2 types 1 and 2 and phospholipase C was measured in the endometrium of women with ovulatory menorrhagia and in those with normal menstrual blood loss. In both groups of subjects phospholipase A2 type 1 activity was significantly higher in the secretory phase than in the proliferative phase (P less than 0.001). The median activity (pmol/mg protein/min) for the proliferative phase was 27.6 in normal subjects and 40.4 in women with ovulatory menorrhagia and for the secretory phase the median activity was 144.5 in normal women and 138.1 in women with ovulatory menorrhagia. There was no difference between the two groups of women at either stage of the cycle. Phospholipase A2 type 2 activity was also higher in the secretory phase than in the proliferative phase (P less than 0.05 for normal subjects and P less than 0.001 for women with menorrhagia). The median activity (pmol/mg protein/min) for the proliferative phase was 94.4 (normal subjects) and 56.6 (women with menorrhagia) and for the secretory phase 148.3 (normal subjects) and 142.5 (women with menorrhagia). The activity of phospholipase A2 type 2 was significantly lower in the proliferative phase of women with ovulatory menorrhagia compared with normal subjects (P less than 0.05). Phospholipase C activity (nmol/mg protein/min) was significantly higher in women with ovulatory menorrhagia (median 8.2) compared with women with normal blood loss (median 5.5) (P less than 0.01).
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PMID:Phospholipase activity in the endometrium of women with normal menstrual blood loss and women with proven ovulatory menorrhagia. 203 95

The possibility that arachidonic acid (AA) plays a role in the regulation of steroidogenesis in goldfish was investigated using preovulatory ovarian follicles incubated in vitro. AA was shown to act in a time- and dose-dependent manner to stimulate testosterone production. AA in the range of 10(-5) to 10(-4) M increased testosterone production within 2 hr and had a maximal effect by 9 hr. The magnitude of the testosterone response to AA was similar to that observed when ovarian follicles were incubated with human chorionic gonadotropin (hCG). Ovarian follicles incubated with AA and either hCG or forskolin (adenylate cyclase activator) produced more testosterone than follicles incubated with either of these compounds alone. The actions of AA on testosterone production were completely blocked by cyclooxygenase inhibitors (indomethacin or ibuprofen) and were reduced by 50% by the lipoxygenase inhibitor nordihydroguaiaretic acid. Phospholipase C was far more effective than phospholipase A2 in the stimulation of testosterone production. Taken together, these results suggest that AA formed subsequent to the action of phospholipase C on membrane phospholipids has a role in the regulation of steroidogenesis in preovulatory goldfish ovarian follicles.
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PMID:Arachidonic acid stimulates steroidogenesis in goldfish preovulatory ovarian follicles. 210 68


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