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)

1,25-dihydroxycholecalciferol (1,25(OH)2D3) rapidly affects calcium (Ca2+) transport in several cell systems, suggesting physiological actions independent of genomic activation. To test this hypothesis, we studied immediate to early effects (0.5-300 sec) of 1,25(OH)2D3 on cytosolic Ca2+ [Ca2+]i in single osteogenic sarcoma ROS 17/2.8 cells loaded with fura-2. An acute rise in [Ca2+]i was observed in 40% of the cells following addition of 1,25(OH)2D3, with a threshold concentration of 10(-11) M. In most cases, the [Ca2+]i rise was transient, with return to baseline within 1 min; less frequently a more prolonged effect was observed, with variable recovery times. 25-hydroxycholecalciferol (25(OH)D3) reproduced the effect of 1,25(OH)2D3 on [Ca2+]i, with equal potency and similar responses, whereas 24,25-dihydroxycholecalciferol, 1 alpha-hydroxycholecalciferol, and 22 oxa-1,25(OH)2D3 were not effective. 1,25(OH)2D3 also increased [Ca2+]i in ROS 24/1 cells, which are defective of receptors for the vitamin D metabolites. At high doses (10(-8)-10(-7) M) of 1,25(OH)2D3 the [Ca2+]i rise in ROS 17/2.8 cells was due to both influx of extracellular Ca2+ and release of Ca2+ from intracellular stores, as the effect was only partially inhibited by Ca2(+)-channel blockade by nifedipine. At low doses (10(-9)-10(-10) M), the effect was entirely dependent on extracellular Ca2+. 1,25(OH)2D3 also increased the production of inositol 1,4,5 trisphosphate (Ins(1, 4, 5)P3) and diacylglycerol, at a threshold dose of 10(-9) M, indicating activation of phospholipase C (PLC). In two thirds of the cells studied, a second addition of 1,25(OH)2D3 within 5 min to cells prestimulated with equimolar doses of the vitamin D metabolite resulted in a [Ca2+]i transient of higher amplitude than the first, a phenomenon occurring at all doses of the hormone, and associated with production of Ins(1, 4, 5)P3. This response amplification was not produced by 25(OH)D3, and pretreatment with 1 alpha(OH)D3 did not significantly enhance 1,25(OH)2D3-induced production of Ins(1, 4, 5)P3. In conclusion, activation of the Ca2+ message system by vitamin D metabolites is a rapid, nongenomic effect; 1,25(OH)2D3 specifically activates both PLC and dihydropyridine-sensitive Ca2+ channels, and "primes" the cells to respond with an enhanced [Ca2+]i rise to a subsequent homologous stimulation; the presence of both the 1 alpha and 25 hydroxyl groups is necessary to express the full hormonal action of vitamin D on [Ca2+]i.
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PMID:Nongenomic activation of the calcium message system by vitamin D metabolites in osteoblast-like cells. 222 14

We investigated the possibility that 1,25-dihydroxycholecalciferol acts in human amnion as a physiologic calcium ionophore to effect increased prostaglandin E2 production in this tissue. This possibility was based on the propositions that this metabolite of vitamin D3 acts in other target tissues, that is, bone, intestine, chorioallantoic membrane, kidney, and intestine, to effect increased calcium absorption, that 1,25-dihydroxycholecalciferol is present in amniotic fluid, which bathes the amnion, and that the mobilization of calcium in amnion is associated with stimulation of enzymes, namely, phospholipase A2 and phosphatidylinositol-specific phospholipase C that act ultimately to effect the release of arachidonic acid, which in turn leads to increased prostaglandin E2 production. We found that human amnion cells, maintained in primary monolayer culture, are responsive to 1,25-dihydroxycholecalciferol. Treatment of these cells with 1,25-dihydroxycholecalciferol for 18 hours brought about the induction, in a dose-dependent manner, of 25-hydroxycholecalciferol 24-hydroxylase, a marker of 1,25-dihydroxycholecalciferol action. In addition, treatment of human amnion cells in monolayer culture with 1,25-dihydroxycholecalciferol caused, within 12 hours, a significant increase in the synthesis of prostaglandin E2, which was maintained for the duration of treatment, that is, 48 hours. These findings may be indicative of a significant physiologic role for 1,25-dihydroxycholecalciferol in metabolic processes that are important in amnion, including transport, amniotic fluid volume homeostasis, and the initiation of parturition.
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PMID:Response of human amnion cells in culture to 1,25-dihydroxycholecalciferol: increased 25-hydroxycholecalciferol 24-hydroxylase activity and prostaglandin E2 formation. 346 44

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

The present studies were performed to determine whether the major biologically active metabolite of vitamin D3, 1,25-dihydroxycholecalciferol [1,25(OH)2D3], could influence the activities of rat colonic particulate guanylate cyclase and adenylate cyclase. To address these issues, colonocytes were harvested from Sprague-Dawley rats and suspended in Krebs-Ringer bicarbonate buffer. The cells were then treated with 1,25(OH)2D3 or other agents (see below) and crude membranes were prepared and analyzed for particulate guanylate cyclase and adenylate cyclase activities. The results of these studies demonstrated that: 1) 1,25(OH)2D3, in a concentration-dependent manner, rapidly (within minutes) stimulated guanylate, but not adenylate cyclase activity; 2) preincubation of the cells with staurosporine, a protein kinase inhibitor, or U73122, an inhibitor of phosphoinositide-phospholipase C-dependent processes, blocked the increase in guanylate cyclase activity induced by 1,25(OH)2D3; and 3) 12-O-tetradecanoyl phorbol 13-acetate and 1,2-dioctanoyl-sn-glycerol, known activators of protein kinase C, also rapidly stimulated rat colonic particulate guanylate cyclase activity. Taken together, these results demonstrate that 1,25(OH)2D3 rapidly stimulates together, these results demonstrate that 1,25(OH)2D3 rapidly stimulates rat colonic particulate guanylate cyclase, at least in part, via a protein kinase C-dependent mechanism.
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PMID:1,25-Dihydroxycholecalciferol rapidly activates rat colonic particulate guanylate cyclase via a protein kinase C-dependent mechanism. 810 80

Three days pretreatment of the prolactin (PRL) secreting GH4C1 cells with 10 nM calcitriol attenuated both the basal and thyrotropin-releasing hormone (TRH)-stimulated (1 microM, 5 s) inositol trisphosphate (IP3) production by 30 and 26%, respectively. The effect was detectable at 10 nM (basal) and 1 pM (TRH-stimulated), and maximal at 1 microM (basal) and 10 nM (TRH), respectively. Calcitriol was at least 100 times more potent than calcidiol and 24-hydroxycalcidiol, and the effect was reversible upon cessation of pretreatment. Calcitriol pretreatment (1 microM, 5 days) also decreased the levels of phosphatidyl-inositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate by 23, 55 and 32%, respectively. GTP gamma S-stimulated (100 microM, 30 s) IP3 production was decreased by 45% after calcitriol pretreatment (10 nM, 5 days). Pertussis toxin (1 nM, 4 h) attenuated both the basal and TRH-stimulated IP3 production, but this effect was omitted by calcitriol pretreatment. Thus, calcitriol specifically attenuates both the basal and TRH-stimulated inositol phosphate production in GH4C1 cells. The mechanism, at least partly, involves decreased availability of phosphoinositides for phospholipase C. Calcitriol regulation of a pertussis toxin-sensitive G-protein might also play some role.
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PMID:Calcitriol attenuates the thyrotropin-releasing hormone-stimulated inositol phosphate production in clonal rat pituitary (GH4C1) cells. 834 24

1,25-Dihydroxyvitamin D-3 (1,25(OH)2D3) which activates the phospholipase C (PLC)-protein kinase C (PKC) signalling pathway, induces within 1 min a dose-dependent (10(-11)-10(-7) M) increase in the release of [3H]arachidonic acid ([3H]AA) from prelabeled embryonic chick myoblasts. The response is dependent on extracellular calcium, since it is suppressed by EGTA and nifedipine, a Ca(2+)-channel blocker, and is mimicked by the calcium ionophore A23187. 1,25(OH)2D3-induced release of [3H]AA is not affected by neomycin (0.5 mM), an inhibitor of phosphoinositide hydrolysis. 12-o-tetradecanoylphorbol-13-acetate (TPA), a PKC activator, induces an extracellular Ca(2+)-independent release of [3H]AA and amplifies the release of AA stimulated by 1,25(OH)2D3. 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H7), a PKC inhibitor, markedly suppressed TPA as well as 1,25(OH)2D3-induced [3H]AA release. Down-regulation of cellular PKC abolishes the effect of the phorbol ester, and partially inhibits 1,25(OH)2D3-induced [3H]AA release. Temporally correlated with AA liberation, the hormone increases the formation of lysophosphatidylcholine (lysoPC) and lysophosphatidylethanolamine (lysoPE) and decreases the cellular content of PC and PE. These results indicate that part of AA release by 1,25(OH)2D3 derives from PLA2 activation and that the effects of the hormone are mediated by PKC in a mode independent of phosphoinositide hydrolysis by PLC.
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PMID:1,25-Dihydroxyvitamin D-3 induces arachidonate mobilization in embryonic chick myoblasts. 839 56

1.25-dihydroxyvitamin D3 is of clinical importance (e.g. in the treatment of psoriasis) given its ability to regulate the proliferation and differentiation of human keratinocytes. 1.25-Dihydroxyvitamin D3 mediates its action via genomic and nongenomic pathways. The nongenomic actions begin with the activation of phospholipase C and the subsequent rapid rise in calcium within the cells. We incorporated 1.25-dihydroxyvitamin D3 in liposomes of varying compositions in an attempt to improve their effect/negative side effect ratio. The influence of empty liposomes (1 mM) and free and liposomally incorporated 1.25-dihydroxyvitamin D3 (10 nM) on the rapid release of sulfidoleucotrien and inositole 1,4,5 triphosphate was examined in keratinocytes in vitro. Free 10 nM 1.25-dihydroxyvitamin D3 provoked a rapid rise in sulfidoleucotriens within 30 seconds, followed by a swift decrease in sulfidoleucotrien and inositole 1,4,5-triphosphate concentration after 10 minutes. Empty liposomes and liposomal-incorporated 1.25-dihydroxyvitamin D3 did not show such a strong effect. These results suggest the occurrence of specific binding sites for 1.25-dihydroxyvitamin D3 on the membrane level that are incapable of recognizing 1.25-dihydroxyvitamin D3 trapped within liposomal membrane.
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PMID:Liposomal incorporation changes the effect of 1.25-dihydroxyvitamin D3 on the phospholipase C signal transduction pathway and the eicosanoid cascade on keratinocytes in vitro. 857 90

1. HL-60 human leukemia cells are a widely employed model system for the analysis of signal transduction processes mediated via regulatory heterotrimeric guanine nucleotide-binding proteins (G-proteins). HL-60 promyelocytes are pluripotent and can be differentiated into neutrophilic or monocytic cells. 2. HL-60 cells express formyl peptide-, complement C5a-, leukotriene B4 (LTB4)- and platelet-activating factor receptors, receptors for purine and pyrimidine nucleotides, histamine H1- and H2-receptors, beta 2-adrenoceptors and prostaglandin receptors. 3. The major G-proteins in HL-60 cells are pertussis toxin (PTX)-sensitive Gi-proteins (Gi2 > Gi3). Gs-proteins and G-proteins of the Gq-family (e.g., G16) are expressed, too. 4. G-protein-regulated effector systems in HL-60 cells are adenylyl cyclase and phospholipase C-beta 2 (PLC-beta 2) and, possibly, phospholipase D (PLD), nonselective cation (NSC) channels and NADPH oxidase. 5. The expression of signal transduction pathways in HL-60 cells strongly depends on the differentiation state of cells. 6. Formyl peptides, via Gi-proteins, mediate activation of PLC, PLD, NSC channels, NADPH oxidase and azurophilic granule release and are referred to as full secretagogues. In dibutyryl cAMP (Bt2cAMP)-differentiated HL-60 cells, C5a and LTB4 are partial and incomplete secretagogues, respectively. There are substantial differences in the Gi-protein activations induced by formyl peptides, C5a and LTB4. 7. In HL-60 promyelocytes, purine and pyrimidine nucleotides mediate activation of PLC and NSC channels largely via PTX-insensitive G-proteins and induce functional differentiation. In Bt2cAMP-differentiated HL-60 cells, they additionally activate PLD, NADPH oxidase and granule release via PTX-sensitive and -insensitive pathways. ATP and UTP are partial secretagogues. Multiple types of receptors (i.e., P2Y- and P2U-receptors and pyrimidinocyeptors) may mediate the effects of nucleotides in HL-60 cells. 8. Bt2cAMP- and 1 alpha,25-dihydroxycholecalciferol-differentiated HL-60 cells express H1-receptors coupled to Gi-proteins and PTX-insensitive G-proteins. In the former cells, histamine mediates activation of PLC and NSC channels, and in the latter, activation of NSC channels. Histamine is an incomplete secretagogue in these cells. 9. HL-60 promyelocytes express H2-receptors coupled to adenylyl cyclase, PLC, and NSC channels. There are substantial differences in the agonist/antagonist profiles of H2-receptor-mediated cAMP formation and rises in cytosolic Ca2+ concentration, indicative of the involvement of different H2-receptor subtypes. H2-receptors mediate functional differentiation of HL-60 cells. 10. Certain cationic-amphiphilic histamine receptor ligands (i.e., 2-substituted histamines, lipophilic guanidines, and a histamine trifluoromethyl-toluidide derivative) show stimulatory effects in HL-60 cells that are attributable to receptor-independent activation of Gi-proteins.
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PMID:G-protein-coupled receptors in HL-60 human leukemia cells. 874 93

We have examined the effects in vitro of calcitriol [1,25(OH)2D3], the hormonal form of vitamin D3, on the breakdown of membrane phosphoinositides in skeletal muscle from young (3 months) and aged (24 months) rats. Calcitriol (10(-9) M) induced a rapid and transient release of IP3/inositol phosphates and diacylglycerol (DAG) from muscle slices/membranes prelabeled with [3H]myo-inositol and [3H]arachidonate, respectively. Inositol phosphate release was maximal at 15 s and then declined. The effects of hormone specificity exhibited as the closely related derivatives of vitamin D3, 25OHD3, 1alphaOHD3 and 24,25(OH)2D3 did not alter muscle inositol phosphate levels. The stimulation of DAG was biphasic, the early phase (15 s) being abolished by neomycin (0.5 mM), an inhibitor of phosphoinositide hydrolysis, similar to IP3 formation and consistent with a role of phospholipase C (PLC) in intracellular signal generation. Neomycin had no effect on the second DAG peak (2 min) induced by calcitriol, suggesting that the late phase of DAG formation is independent from the hydrolysis of phosphoinositides. Higher basal inositol phosphate and DAG levels were detected in muscle from aged rats thereby reducing the effects of the hormone on second messenger generation ( -80 and -60% for IP3 and DAG, respectively). Calcitriol stimulation of PLC was mimicked, in both young and old rats, by GTPgammaS, a non-hydrolyzable analogue of GTP, while GDPbetaS, a G protein inhibitor, suppressed the effect of the hormone. The early effects of calcitriol and GTPgammaS were not additive. Bordetella pertussis toxin abolished by 85% the effects of calcitriol on inositol phosphate release in young rats but was without effect in aged animals. These results demonstrate that calcitriol activates phosphoinositide-PLC in rat skeletal muscle by a mechanism which involves a pertussis-sensitive G protein and that the effects of the hormone are altered with ageing.
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PMID:Age-related loss of calcitriol stimulation of phosphoinositide hydrolysis in rat skeletal muscle. 954 16

17beta-estradiol and 1,25-dihydroxyvitamin D(3)()(calcitriol) rapidly increase (< 5 sec) the concentration of intracellular calcium by mobilizing Ca(2+) from the endoplasmic reticulum and forming inositol 1,4,5-trisphosphate (InsP(3)) and diacylglycerol. Calcitriol increases InsP(3) formation via activation of phospholipase C (PLC)-beta1 linked to a pertussis toxin (PTX)-insensitive G-protein, and estradiol via activation of PLC-beta2 linked to a PTX-sensitive G-protein. Since PLC are effectors of different subunits of various G-proteins, we looked for and identified several G-subunits (Galpha(q/11), Galphas, Galphai, Gbeta and Ggamma) in female rat osteoblasts using Western immunoblotting. The action of calcitriol on InsP(3) formation and Ca(2+) mobilization in Fura-2-loaded confluent osteoblasts involved Galpha(q/11). The membrane effects of estradiol involved Gbetagamma; subunits, and principally Gbeta subunits, but not alpha-subunits. These results may provide additional evidence for membrane receptors of steroid hormones. Since PLC-beta1 is the target effector of Galpha(q/11), whereas PLC-beta2 is only activated by betagamma subunits, this specificity may help to generate membrane receptor-specific responses in vivo.
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PMID:Galpha(q/11) and gbetagamma proteins and membrane signaling of calcitriol and estradiol. 1046 12


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