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 effects of carbachol (CCh) on phospholipase C(PLC)-mediated phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis and its modulation by isoproterenol were investigated in SV40-adenovirus transformed rabbit corneal epithelial cells (RCEC). When examined under light microscope, these cells exhibited a cobblestone-like appearance typical of the corneal epithelial cells grown in primary culture. Addition of CCh (0.1 mM) for 30 min to RCEC, prelabeled with 32Pi, decreased the radioactivity in phosphatidylinositol 4-phosphate and PIP2 by 15 and 27%, respectively, and concomitantly increased the radioactivity in phosphatidylinositol and phosphatidic acid by 14 and 38%, respectively. When the concentration of CCh was increased to 1 mM, the changes in radioactivity were even more pronounced. Addition of CCh (0.1 mM) to the cells, prelabeled with myo[3H]inositol, increased the accumulation of [3H]inositol 1,4,5-trisphosphate ([3H]InsP3) by 115%, indicating stimulation of PLC-mediated PIP2 hydrolysis. Similar increases were also observed in [3H]InsP1 and [3H]InsP2. The effects of CCh on inositol phosphate accumulation were time- and dose-dependent, and were inhibited by atropine (10 microM), suggesting that the observed effects of CCh were mediated by activation of muscarinic cholinergic receptors. The effects of CCh were antagonized more potently by 4-diphenylacetoxy N-methyl-piperidine than by pirenzepine, indicating that the muscarinic receptors involved in PLC activation are probably of M3 type. By Western immunoblotting analysis with various anti-PLC antibodies, the RCEC were shown to contain PLC gamma 1 and PLC delta 1 in the soluble fraction and PLC beta 1 in the microsomal fraction. Addition of isoproterenol to RCEC, increased cAMP both in a time- and dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of carbachol on phospholipase C-mediated phosphatidylinositol 4,5-bisphosphate hydrolysis, and its modulation by isoproterenol in rabbit corneal epithelial cells. 758 2

Rat islets respond to glucose stimulation with a marked first and second phase increase in insulin secretion. In contrast, mouse islets have a similar first phase response but little second phase secretion. In these studies, we determined if activation of phospholipase C (PLC) accounts for these differences in second phase insulin secretion in these two species. Stimulation of freshly isolated mouse and rat islets with 15 mM glucose resulted in comparable first phase insulin secretion; however, the second phase response from mouse islets was only doubled from 28 +/- 6 to 60 +/- 7 pg/islet.min compared with an increase from 24 +/- 4 to 1064 +/- 93 pg/islet.min from rat islets. The addition of the muscarinic agonist carbachol (100 microM) in the presence of 15 mM glucose, however, markedly increased second phase insulin release from mouse islets to 801 +/- 80 pg/islet.min. Similar increases in second phase insulin release from mouse islets were obtained with the addition of 500 nM of the protein kinase C activator tetradecanoyl phorbol acetate in the presence of 15 mM glucose. However, the incretin factor glucagon-like peptide-1, which elevates islet cAMP levels, had little effect on second phase insulin release in the mouse. An analysis of PLC-mediated phosphoinositide (PI) hydrolysis revealed that 15 mM glucose increased inositol phosphate (IP) accumulation 0.5-fold above baseline in mouse islets compared with 3.7-fold in rat islets. In contrast, carbachol stimulated IP accumulation 3.5-fold in both mouse and rat islets. Analysis of PLC isozymes with isozyme specific monoclonal antibodies, demonstrated that mouse islets express 14 +/- 4% of PLC-delta 1 and 18 +/- 6% of PLC-beta 1 compared with rat islets but similar amounts of the PLC-gamma 1 (117 +/- 16%). These findings suggest that the decreased second phase insulin secretory response in mouse compared with rat islets results, at least in part, from an inability of high glucose to stimulate comparable increments in PI hydrolysis. This lack of glucose responsiveness may be due to the pronounced underexpression of specific PLC isozymes in the mouse.
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PMID:Regulation of insulin release by phospholipase C activation in mouse islets: differential effects of glucose and neurohumoral stimulation. 758 23

Four native and cloned adenosine receptors (ARs), designated A1AR, A2aAR, A2bAR, and A3AR, have been characterized functionally and by radioligand binding. In the present study, we have used selective antibodies to identify the G protein subunits and phospholipase C (PLC)-beta isoform coupled to A1ARs in smooth muscle membranes and permeabilized muscle cells from rabbit intestine. Immunoblot analysis disclosed the presence of a full complement of G proteins. Adenosine caused contraction of dispersed muscle cells and increases in D-myo-inositol-1,4,5-trisphosphate, intracellular calcium, and cAMP levels. Contraction and the increases in D-myo-inositol-1,4,5-trisphosphate and intracellular calcium levels were abolished by the A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine and augmented by the A2 antagonist CGS-15943; the reverse occurred with cAMP. A selective A1AR agonist, cyclopentyladenosine, inhibited forskolin-stimulated cAMP accumulation; the inhibition was reversed by treatment of the cells with pertussis toxin or a G alpha i3-specific antibody. The pattern of inhibition implied coexistence of A1ARs and A2ARs coupled to interactive signaling pathways, with A2ARs mediating activation of adenylyl cyclase and A1ARs mediating activation of PLC and inhibition of adenylyl cyclase. Adenosine-stimulated PLC activity in muscle membranes was selectively blocked by G alpha i3- and G beta-specific antibodies, as well as by a PLC-beta 3-specific antibody, but not by antibodies to other PLC-beta isoforms or G proteins. A combination of maximally effective concentrations of G alpha i3- and G beta-specific antibodies did not elicit greater inhibition than did either alone. In contrast, cholecystokinin-stimulated PLC activity was selectively blocked by PLC-beta 1- and G alpha q/11-specific antibodies. Adenosine-stimulated contraction and 45Ca2+ efflux in permeabilized muscle cells were also selectively blocked by G alpha i3-, G beta-, and PLC-beta 3-specific antibodies, whereas cholecystokinin-stimulated contraction was selectively blocked by PLC-beta 1- and G alpha q/11-specific antibodies. The results indicate that A1ARs are coupled to PLC-beta 3 via both alpha and beta gamma subunits of Gi3.
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PMID:Adenosine A1 receptor-mediated activation of phospholipase C-beta 3 in intestinal muscle: dual requirement for alpha and beta gamma subunits of Gi3. 760 57

Previous investigations have demonstrated the presence of conventional lipid kinases and phospholipase C (PLC) activities in nuclei of Friend erythroleukemia cells. Moreover, when Friend erythroleukemia cells are treated for 96 h with the antitumor drug tiazofurin, the induction of erythroid differentiation is accompanied by changes in amounts of both phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate due to the inhibition of an uncharacterized nuclear PLC activity. Here, we show that the nuclear PLC beta 1 isoform is down-regulated by tiazofurin (5 microM) treatment of Friend erythroleukemia cells as shown by both Western blot and Northern blot analyses for PLC beta 1 message. This indicates that PLC beta 1 down-regulation is tightly linked with erythroid differentiation of Friend erythroleukemia cells and that the autonomous nuclear signaling via inositol lipid cycle can be controlled by the antitumor drug tiazofurin.
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PMID:Phosphoinositide signaling in nuclei of Friend cells: tiazofurin down-regulates phospholipase C beta 1. 760 13

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) induces the differentiation of normal human keratinocytes, in part by increasing their basal intracellular calcium levels (Cai) over a period of hours. Agonists such as ATP acting through membrane receptors cause an immediate but transient increase in Cai accompanied by an increase in inositol trisphosphate (IP3). Treatment of keratinocytes for 24 h with 1 nM 1,25(OH)2D3 resulted in a two- to four-fold potentiation of the Cai response of these cells to ATP. This potentiation was inhibitable with cycloheximide, unaccompanied by a change in total intracellular calcium pools, but associated with an increase in basal IP3 levels and ATP-stimulated IP3 production. Treatment with 1,25(OH)2D3 raised the protein and mRNA levels of phospholipase C isoenzymes, particularly phospholipase C-beta 1 in a dose-dependent manner. These studies indicate that 1,25(OH)2D3 modulates the keratinocyte signal transduction pathway by induction of phospholipase isoenzymes, a previously undescribed action for this hormone.
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PMID:1,25-Dihydroxyvitamin D3 upregulates the phosphatidylinositol signaling pathway in human keratinocytes by increasing phospholipase C levels. 761 34

Calcium flux is required for the mammalian sperm acrosome reaction, an exocytotic event triggered by egg binding, which results in a dramatic rise in sperm intracellular calcium. Calcium-dependent membrane fusion results in the release of enzymes that facilitate sperm penetration through the zona pellucida during fertilization. We have characterized inositol 1,4,5-trisphosphate (IP3)-gated calcium channels and upstream components of the phosphoinositide signaling system in mammalian sperm. Peptide antibodies colocalized G alpha q/11 and the beta 1 isoform of phospholipase C (PLC beta 1) to the anterior acrosomal region of mouse sperm. Western blotting using a polyclonal antibody directed against purified brain IP3 receptor (IP3R) identified a specific 260 kD band in 1% Triton X-100 extracts of rat, hamster, mouse and dog sperm. In each species, IP3R immunostaining localized to the acrosome cap. Scatchard analysis of [3H]IP3 binding to rat sperm sonicates revealed a curvilinear plot with high affinity (Kd = 26 nM, Bmax = 30 pmol/mg) and low affinity (Kd = 1.6 microM, Bmax = 550 pmol/mg) binding sites, reflecting among the highest receptor densities in mammalian tissue. Immunoelectron microscopy confirmed the acrosomal localization in rat sperm. The IP3R fractionated with acrosomes by discontinuous sucrose gradient centrifugation and was enriched in the medium of acrosome-reacted sperm. ATP-dependent 45Ca2+ loading of digitonin permeabilized rat sperm was decreased by 45% in the presence of 10 microM IP3. The IP3-mediated release of calcium was blocked by heparin. Thapsigargin, a sequiterpene lactone inhibitor of the microsomal Ca(2+)-ATPase, stimulated the acrosome reaction of mouse sperm to the same extent as the Ca2+ ionophore, A23187. The failure of caffeine and ryanodine to affect calcium accumulation suggested that thapsigargin acted through an IP3-sensitive store. The presence of G alpha q/11, PLC beta 1 and a functional IP3R in the anterior acrosomal region of mammalian sperm, as well as thapsigargin's induction of the acrosome reaction, implicate IP3-gated calcium release in the mammalian acrosome reaction.
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PMID:Inositol 1,4,5-trisphosphate receptors selectively localized to the acrosomes of mammalian sperm. 764 3

We had previously reported that the CD29 mAb "K20," presented in a soluble form, blocks peripheral T cell proliferation/activation induced by a CD3 mAb. To better characterize the negative signal delivered by soluble K20, we have investigated its effects on the phospholipid metabolism, both in Jurkat and CD4+ T cells. In CD3-activated T cells, K20 inhibited the increase of diacylglycerol (DAG) and phosphatidic acid levels, but did not modify phosphatidylinositol 4,5-bisphosphate levels, cytosolic Ca2+ raise, and inositolphosphates formation, indicating that K20 did not inhibit phosphatidylinositol 4,5-bisphosphate hydrolysis by phospholipase C-gamma. Moreover, in these conditions, K20 increased phosphatidylethanolamine levels, without variation of phosphatidylcholine, phosphatidylserine, and phosphatidylinositol, suggesting that K20 specifically increased the phosphatidylethanolamine biosynthesis from DAG. Thus, the effects of K20 on DAG and phosphatidic acid levels resulted from an accelerated catabolism rather than from a defect of synthesis. That K20 acts solely at an early step of T cell activation, namely before the binding of IL-2 to its receptor, is supported by the observation that adding exogenous rIL-2 increased proliferation in spite of K20. These results suggest that the beta 1 integrin molecules interact with the membrane phospholipid metabolism and they appear to be the hallmark of a peculiar negative pathway of T cell activation, likely to play an important regulatory role mediated via the T cell integrin molecules.
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PMID:Suppressive effect of T cell proliferation via the CD29 molecule. The CD29 mAb 1 "K20" decreases diacylglycerol and phosphatidic acid levels in activated T cells. 768 29

Phospholipase C-beta 4(PLC-beta 4), a new member of phospholipase C isozyme, was purified from bovine cerebellum. The cDNA encoding rat PLC-beta 4 has been cloned from a cDNA library prepared from rat brain. The predicted open reading frame encodes a protein of 1,176 amino acids with a calculated molecular weight of 134,552. The deduced amino acid sequence exhibits 39, 36, and 36% identity with the sequences of rat PLC-beta 1, human PLC-beta 2, and rat PLC-beta 3, respectively. The amino acid sequence of PLC-beta 4, especially, shows higher identity (50%) with norpA PLC sequence from Drosophila melanogaster than those of other PLC-beta subtypes, suggesting that the PLC-beta 4 might be a mammalian PLC equivalent of norpA PLC implicated in photosignal transduction in Drosophila.
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PMID:Cloning of cDNA encoding rat phospholipase C-beta 4, a new member of the phospholipase C. 768 23

Phosphoinositide metabolism, phospholipase C immunoreactivity, and protein kinase C translocation were measured in brain slices of 6- and 24-month-old F-344 rats. Basal phosphoinositide labeling and accumulation of [3H]inositol phosphates were reduced in the 24-month-old rats. The cholinergic agonist, carbachol, induced lower net accumulations of inositol phosphates in striatal, hippocampal, and cortical slices of the aged rats. The dose-response curve for carbachol showed a significantly lower maximal response in the striatum of senescent rats, whereas the time course of [3H]inositol incorporation into inositol metabolites and the accumulation of free [3H]inositol in tissues from young and old animals were not different. Quantitative analyses showed marked reductions in endogenous brain levels of the phosphoinositides and in phospholipase C-beta 1 immunoreactivity, but no marked reductions in endogenous brain levels of the phosphoinositides and in phospholipase C-beta 1 immunoreactivity, but no changes in phospholipase C-gamma levels in aged animals. Moreover, basal protein kinase C activity and carbachol-mediated translocation of the enzyme were significantly reduced in the cerebral cortex of the senescent animals. These findings imply that aging is associated with alterations in the brain content, metabolism, and activity of phosphoinositide-derived second messengers in the F-344 rat brain.
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PMID:Decreased phospholipase C-beta immunoreactivity, phosphoinositide metabolism, and protein kinase C activation in senescent F-344 rat brain. 772 32

Guanosine 5'-[beta gamma-imido]triphosphate (p[NH]ppG)-stimulated phospholipase C (PLC) activity in bovine brain coated vesicles is inhibited by glutamate agonists. In the present study we show that quisqualic acid (QA), (+/-)-trans-1-aminocyclopentane-1,3-dicarboxylate (trans-ACPD), glutamic acid and ibotenic acid inhibited p[NH]ppG-stimulated PLC by 44, 41, 36 and 25% respectively. Carbachol also produced an inhibition of p[NH]ppG-stimulated PLC by 45%. The inhibition caused by trans-ACPD and QA was dose-dependent. DL-2-Amino-3-phosphonopropionic acid and (RS)-alpha-methyl-4-carboxyphenylglycine, specific antagonists of metabotropic glutamate receptors (mGluRs), abolished these inhibitory effects. trans-ACPD inhibition of p[NH]ppG-stimulated PLC was also observed in the presence of ionotropic glutamate receptor antagonists. When carbachol and QA or trans-ACPD were combined, additive inhibitory effects were observed. Preincubation of bovine brain coated vesicles with pertussis toxin abolished the inhibitory effects of mGluR analogues and carbachol on p[NH]ppG-stimulated PLC activity. The presence of Gs alpha and pertussis toxin substrates, Gi alpha and Go alpha subunits as well as PLC beta 1 in bovine brain coated vesicles has been confirmed by immunoblot. These results support the coupling of mGluRs to a PLC in an inhibitory manner through a pertussis toxin-sensitive G-protein in bovine brain coated vesicles.
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PMID:Metabotropic glutamate receptor analogues inhibit p[NH]ppG-stimulated phospholipase C activity in bovine brain coated vesicles: involvement of a pertussis toxin-sensitive G-protein. 774 17


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