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 protein kinase C (PKC) activator 12-O-tetradecanoylphorbol 13-acetate (TPA) has been shown to potentiate the stimulatory effect of ethanol on the hydrolysis of phosphatidylethanolamine (PtdEtn) in NIH 3T3 fibroblasts. Following an initial 20-min period, the main product of PtdEtn degradation in cells treated with TPA plus ethanol was ethanolamine phosphate. Here, we have examined the regulatory role of PKC and the possible catalytic role of phospholipase C in the formation of ethanolamine phosphate. TPA, bryostatin, and bombesin, direct or indirect activators of PKC, had similar potentiating effects on ethanol-induced formation of [14C]ethanolamine phosphate from [14C]PtdEtn in [14C]ethanolamine-prelabelled NIH 3T3 fibroblasts. At lower concentrations of ethanol (40-80 mM), significant stimulation of ethanolamine phosphate formation required longer treatments (2 h or longer). The combined effects of TPA (100 nM) and ethanol (50-200 mM) on ethanolamine phosphate formation were not inhibited by the PKC inhibitors staurosporine or 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7). In contrast, these inhibitors significantly inhibited TPA-induced formation of ethanolamine, catalyzed by a phospholipase-D-type enzyme. In membranes isolated from TPA+ethanol-treated cells, enhanced formation of ethanolamine phosphate was maintained for at least 20 min. Down-regulation of PKC by prolonged (24-h) treatment of NIH 3T3 fibroblasts by 300 nM TPA enhanced, while overexpression of alpha-PKC in Balb/c fibroblasts diminished, the stimulatory effect of ethanol on the formation of ethanolamine phosphate. Finally, addition of the protein phosphatase inhibitor okadaic acid (2 microM) to fibroblasts inhibited TPA+ethanol-induced formation of ethanolamine phosphate. These results suggest that alpha-PKC-mediated protein phosphorylation may negatively regulate PtdEtn hydrolysis and that the potentiating effect of TPA may result, at least partly, from increased degradation of this PKC isoform.
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PMID:The long-term combined stimulatory effects of ethanol and phorbol ester on phosphatidylethanolamine hydrolysis are mediated by a phospholipase C and prevented by overexpressed alpha-protein kinase C in fibroblasts. 132 80

Changes in cytosolic calcium concentration ([Ca2+]i) have been implicated in the regulation of intracellular pH (pHi) in several cell types. In the present study we investigated the regulatory mechanism of Na+/H+ exchange induced by angiotensin II (AII) in cultured rat vascular smooth muscle cells (VSMCs). Serially passaged VSMCs from Sprague-Dawley rat thoracic aorta were grown on coverslips and loaded with the pH-sensitive fluorescent indicator 2',7'-bis-(carboxyethyl)-5,6-carboxyfluorescein (BCECF). In HCO(3-)-free Ringer solution, pH 7.40, the resting pHi was 7.21 +/- 0.02 (n = 21). A biphasic response was seen after exposure of these cells to AII: an initial transient a acidification, followed by sustained alkalization. The magnitude of alkalization was dose-dependent. AII-mediated acidification was completely inhibited by [Sar1-IIe5-Gly8]AII, but amiloride had no effect. In contrast, the alkalization induced by AII was abolished by both amiloride and Na(+)-free medium. In Ca(2+)-free medium, the AII-induced alkalization was partially blocked and verapamil also caused partial inhibition. Since AII activates phospholipase C in VSMCs, we examined whether AII would increase Na+/H+ exchange by activation of protein kinase C. An inhibitor of protein kinase C, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), partially inhibited the alkalization induced by AII. These results indicate that AII stimulates cytoplasmic alkalization via an amiloride-sensitive Na+/H+ exchange system in cultured rat VSMCs, and that this AII-stimulated Na+/H+ exchange is mediated by Ca(2+)-dependent and protein kinase C-dependent mechanisms.
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PMID:Stimulation of Na+/H+ exchange induced by angiotensin II in cultured rat vascular smooth muscle cells: role of Ca2+ and C-kinase. 154 35

The mechanism of aluminumfloride (AlF)-induced Ca2+ sensitization was explored in alpha-toxin-permeabilized rabbit mesenteric artery. In the presence of 0.18 microM Ca2+ and deferoxamine, a strong chelator of aluminum (Al3+), fluoride (F-; applied in the form of NaF) induced very slow tension development, while in the presence of tracer levels of Al3+ tension developed rapidly possibly due to formation of Al-F complexes (especially AlF4-). As a result, AlF significantly shifted the relationship between tension development and free Ca2+ concentration in the Ca(2+)-EGTA buffer (pCa-tension curve) to the left. The rate of the tension development also depended on the EGTA concentration: increasing the EGTA concentration from 0.5 to 10 mM markedly decreased the maximal rate of contraction ((dT/dt)max), probably due to chelation of Al3+ by EGTA, without effect on the maximal tension (delta Tmax). The AlF-induced Ca2+ sensitization could be reversed by extensive washing with relaxing solution (pCa greater than 8), in contrast to the contractions induced by guanosine 5'-[gamma-thio]triphosphate (GTP gamma s; a non-hydrolyzable GTP analogue) or phorbol 12,13-dibutyrate (PDBu) which were irreversible. However, the action of all the compounds appeared to be mediated through a H-7 (1-[5-isoquinolinesulfonyl]-2-methylpiperazine dihydrochloride)-sensitive pathway, and no additive effects among them were observed. In addition, GDP increased (dT/dt)max due to AlF without changing delta Tmax, whereas guanosine 5'-[beta-thio]diphosphate (GDP beta s; a non-hydolyzable GDP analogue) decreased both parameters. These findings suggest that AlF acts on G-proteins to enhance Ca2+ sensitivity of contractile elements through a H-7-sensitive pathway.
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PMID:Aluminum fluoride induces a reversible Ca2+ sensitization in alpha-toxin-permeabilized vascular smooth muscle. 158 51

Na(+)-Ca2+ exchange contributes to regulation of cytosolic free Ca2+ levels ([Ca2+]i) of cultured human mesangial cells following phospholipase C stimulation, as shown by larger responses to vasoconstrictors such as angiotensin II (ANG II) or endothelin 1 in Na(+)-free media. In turn, previous activation of phospholipase C by vasoconstrictors significantly enhances the amplitude of the [Ca2+]i elevation induced by Na+ withdrawal. We studied the mechanisms of upregulation in monolayer cultures loaded with the fluorescent Ca(2+)-sensitive probe fura-2. The exchanger was stimulated by insulin and inhibited by chronic exposure to serum. A rise of [Ca2+]i was not sufficient per se to enhance exchange activity, as prior elevation of [Ca2+]i with the ionophores ionomycin or 8-bromo-A23187 failed to augment the response to Na+ withdrawal. Protein kinase C (PKC) activation by phorbol 12-myristate-13-acetate (PMA), alone or in combination with a rise of [Ca2+]i, potently inhibited basal and vasoconstrictor-enhanced Na(+)-Ca2+ exchange. Suppression of the effects of ANG II was not due to frustrated phospholipase C activation by PMA, because addition of PMA after ANG II also inhibited Na(+)-Ca2+ exchange. PKC downregulation by 24-h pretreatment with PMA or inhibition with 1-(5-isoquinolinesulfonyl)-2-methylpiperazine or staurosporine did not prevent activation by ANG II. The exchanger was markedly potentiated by Na+ loading the cells with gramicidin D or reducing extracellular K+. ANG II failed to stimulate Na(+)-Ca2+ exchange when added in the absence of extracellular Na+. Therefore vasoconstrictors promote Na(+)-Ca2+ exchange by a mechanism independent of [Ca2+]i and PKC while presumably linked to Na+ influx.
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PMID:Regulation of Na(+)-Ca2+ exchange in cultured human mesangial cells. 171 60

Tumor-promoting phorbol esters, e.g., 12-O-tetradecanoylphorbol 13-acetate (TPA), inhibit TSH-stimulated iodide organification in vitro implying a role for protein kinase C (PKC) in the regulation of differentiated thyroid function. To further explore the PKC dependence of this action of TPA, we studied the effects of PKC inhibition and downregulation on phorbol-mediated differentiated thyroid function in vitro. In addition, the effects of the nonphorbol PKC activator, phospholipase C (PLC) were studied. TPA (100 nM) inhibited TSH-stimulated iodide organification in cultured porcine thyroid cells by over 95% and caused PKC translocation in vitro. Exogenous PLC (1 U/mL) could mimic these effects of TPA. The PKC inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) inhibited TSH-stimulated iodide organification at concentrations exceeding 10 microM. However, partial recovery of phorbol- and PLC-inhibited iodide organification was seen in the presence of identical concentrations of H7. H7 had no effect on PKC translocation in porcine thyroid cell extracts. After 24 h of TPA treatment to induce PKC downregulation, no recovery of TSH-stimulated iodide organification was observed, suggesting that the effects of TPA were irreversible. These studies indicate that the effects of TPA and PLC on differentiated thyroid function are mediated, at least in part, by PKC. These findings provide further evidence for a role for PKC in the regulation of differentiated thyroid function.
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PMID:Phorbol ester and phospholipase C-mediated differentiated thyroid function in vitro: the effects of protein kinase C inhibition and downregulation. 182 67

MCH (melanin concentrating hormone) is a heptadecapeptide, Asp-Thr-Met-Arg-Cys-Met-Val-Gly-Arg-Val-Tyr-Arg-Pro-Cys-Trp-Glu-Val, which stimulates melanosome (melanin granule) aggregation to a perinuclear position within teleost fish integumental melanocytes, resulting in lightening of the skin. The mechanisms of action of MCH are unknown. Drugs that affect the diacylglycerol/inositol triphosphate pathway were used to investigate the possible roles of this pathway in the mechanisms of action of MCH on Synbranchus marmoratus (teleost) melanocytes. The shift of the dose-response curve to MCH in the presence of various concentrations of 4-bromophenacyl bromide and neomycin sulphate, phospholipase C inhibitors, suggests that phospholipase C is stimulated after MCH receptor activation. Low concentrations (10(-9) to 10(-8) M) of the phorbol ester TPA exhibited MCH-like activity, eliciting a dose-dependent melanosome aggregation. Higher doses, however, displaced to the right the dose-response curve to MCH, as did the protein kinase C inhibitors, dibucaine and 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). These results support the assumption that protein kinase C mediates the pigment aggregating activity of MCH. Both MCH and norepinephrine lightening actions were abolished by beta-glycerophosphate, a phosphatase inhibitor, suggesting that a protein dephosphorylation occurs during melanosome aggregation, and is, therefore, a common event triggered by MCH and norepinephrine, although both agonists act through separate receptors and exhibit different transduction mechanisms.
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PMID:Protein-kinase C mediates MCH signal transduction in teleost, synbranchus marmoratus, melanocytes. 194 11

Stimulation of C6 cells with endothelin-1 (ET) caused a biphasic sn-1,2-diacylglycerol (1,2-DG) generation, which occurred not only via phosphatidylinositol 4,5-P2 (PIP2) hydrolysis by specific phospholipase C action, but also through the breakdown of phosphatidylcholine (PC) induced by either PC phospholipase C or D. ET also stimulated DNA synthesis in serum-starved C6 cells. However, in the presence of 1-(5-isoquinolynylsulfonyl)-2-methylpiperazine (H-7), a protein kinase C (PKC) inhibitor, the [3H]thymidine incorporation was markedly inhibited, which was concurrent with the 1,2-DG formation: the second peak was reduced. These findings suggest that brain glial cells might be an important target for ET. In addition to other possible roles, ET may also mediate mitogenesis in the brain, presumably through a PKC-dependent activation of phospholipase C and/or D hydrolyzing PC.
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PMID:Diacylglycerol formation and DNA synthesis in endothelin-stimulated rat C6 glioma cells: the possible role of phosphatidylcholine breakdown. 202 29

The mechanisms by which phospholipase C from Clostridium perfringens stimulates release of arachidonic acid (AA) in cultured intestinal epithelial cells (INT-407) were investigated. INT-407 cells were first allowed to incorporate 14C-labeled AA into their phospholipids; the labeled cells were then exposed to phospholipase C, and the release of free 14C-AA was determined. Phospholipase C caused a rapid (3 min) intracellular rise of free 14C-AA, followed by a considerable, dose- and time-dependent release of 14C-AA into the extracellular medium. For comparison, the calcium ionophore A23187 also caused a rapid mobilization of free 14C-AA, but a much lower extracellular 14C-AA release than phospholipase C during longer (1 h) incubation. The 14C-AA release was accompanied by a degradation of 14C-myo-inositol-labeled phosphatidylinositols and was reduced by the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7). Both phospholipase C- and A23187-stimulated 14C-AA release was associated with degradation of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol and was reduced by nordihydroguaiaretic acid and 4-bromophenacyl bromide, two known phospholipase A2 inhibitors. In addition, the 14C-AA release was reduced by the calmodulin inhibitors trifluoperazine, compound 48/80, and N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7). These findings indicate that phospholipase C from C. perfringens stimulates phospholipase A2-mediated AA release from human intestinal epithelial cells and suggest that this stimulation is brought about via processes involving phosphatidylinositol breakdown and activation of calmodulin and protein kinase C. It is possible that this phospholipase C-evoked AA release may contribute to the mucosal pathologic condition in diseases with altered intestinal microbial flora.
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PMID:Phospholipase C from Clostridium perfringens stimulates phospholipase A2-mediated arachidonic acid release in cultured intestinal epithelial cells (INT 407). 211 Jun 84

We have previously demonstrated that influenza A virus (IAV) stimulates the human neutrophil through phospholipase C activation. With the use of the fluorescent indicator 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein (BCECF), cytoplasmic acidification and subsequent alkalinization are shown to accompany this activation. These responses are not inhibited by pertussis toxin (PT). The alkalinization is mediated largely *but not entirely) by the Na(+)-H+ antiporter and is not initiated, or modulated, by the IAV-induced cytosolic Ca2+ (Cai2+) rise. Rather, protein kinase C (PKC) is likely the mediator of cell alkalinization, based on studies using the PKC inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7). The acidification can be dissociated from the alkalinization response, which is also independent of Cai2+ fluxes and of PKC. Both pHi responses can be dissociated from the respiratory burst. Cytosolic alkalinization and acidification seem to reflect two independently mediated responses of the activated neutrophil, the former resulting ultimately from phospholipase activation and the latter from other activities that are not yet fully characterized.
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PMID:Human neutrophil stimulation by influenza virus: relationship of cytoplasmic pH changes to cell activation. 211 68

Studies were performed to examine interactions between the adenylyl cyclase (AC) and phospholipase C (PLC) signaling systems in cultured rat inner medullary collecting duct cells. Stimulation of AC by either arginine vasopressin (AVP) or forskolin or addition of exogenous cAMP inhibits epidermal growth factor (EGF)-stimulated PLC. This inhibition is mediated by activation of cAMP-dependent kinase as it is prevented by pretreatment with the A-kinase inhibitor, N-[2-(methylamino)ethyl]-5-isoquinoline-sulfonamide (H8) but not by the C-kinase inhibitor, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7). Exposure to EGF eliminates AVP-stimulated cAMP generation. This is not mediated by a cyclooxygenase product as inhibition by EGF is observed even in the presence of the cyclooxygenase inhibitor, flurbiprofen. Inhibition by EGF is not due to an increase in inositol trisphosphate (IP3) as exposure of saponin-permeabilized cells to exogenous IP3 is without effect. Inhibition by EGF is prevented by pretreatment with the C-kinase inhibitor, H7, but not by the A-kinase inhibitor, H8. Exposure to the synthetic diacylglycerol (DAG), dioctanoylglycerol, also inhibits AVP-stimulated AC activity; therefore, inhibition by EGF is due to activation of protein kinase C. Thus, in cultured rat inner medullary collecting duct cells, cAMP and DAG function as mutually inhibitory second messengers with each impairing formation of the other.
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PMID:Cyclic adenosine monophosphate and diacylglycerol. Mutually inhibitory second messengers in cultured rat inner medullary collecting duct cells. 216 48


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