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)

Treatment of neonatal rat cardiomyocytes for 72 h in the presence of tumor necrosis factor alpha (TNF alpha) (10 U/ml) lead to a decrease in basal and alpha 1-adrenoceptor-induced formation of the calcium-mobilizing second messenger inositol trisphosphate (IP3) and its metabolites, IP2 and IP1, by 35 and 26%, respectively. The synthesis of phosphatidylinositol bisphosphate (PIP2), the substrate of PI-specific phospholipase C, was decreased by 45% following the TNF alpha (10 U/ml) exposure. Time courses of TNF alpha (10 U/ml)-induced alterations in rat cardiomyocytes showed a parallel decline of basal inositol phosphate formation and PIP2 synthesis suggesting that the decrease in inositol phosphate formation was due to the reduction in PIP2 synthesis. As the TNF alpha-induced decrease of PIP2 synthesis was associated with a decreased synthesis of the phospholipid phosphatidylinositol (PI), the precursor of PIP2, by 33%, the decreased availability of PIP2 is apparently, at least in part, the result of the decreased synthesis of PI. As an apparent functional consequence of the decrease in IP3 formation following the TNF alpha exposure, the alpha 1-adrenoceptor-mediated induction of arrhythmias by 100 mumol/l noradrenaline + 10 mumol/l timolol was abolished in TNF alpha-pretreated rat cardiomyocytes. To investigate one of the possible mechanisms of the TNF alpha-induced decrease of PIP2 formation, the effect of TNF alpha pretreatment on glycerol-3-phosphate dehydrogenase (GDH), a key enzyme of lipogenesis, was studied: Exposure of the rat cardiomyocytes for 72 h to TNF alpha induced a concentration-dependent decrease in GDH activity by maximally 55%.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Tumor necrosis factor alpha decreases inositol phosphate formation and phosphatidylinositol-bisphosphate (PIP2) synthesis in rat cardiomyocytes. 817 May 1

The kinetic properties of endothelin-1 (ET-1) binding sites and the production of inositol phosphates (IPs; IP1, IP2, IP3), cyclic AMP, thromboxane B2, and prostaglandin F2 alpha induced by various endothelins (ET-1, ET-2, ET-3, and sarafotoxin S6b) were examined in endothelial cells derived from human brain microvessels (HBECs). The presence of both high- and low-affinity binding sites for ET-1 with KD1 = 122 pM and KD2 = 31 nM, and Bmax1 = 124 fmol/mg of protein and Bmax2 = 909 fmol/mg of protein, respectively, was demonstrated on intact HBECs. ET-1 dose-dependently stimulated IP accumulation with EC50 (IP3) = 0.79 nM, whereas ET-3 was ineffective. The order of potency for displacing ET-1 from high-affinity binding sites (ET-1 > ET-2 > sarafotoxin S6b > ET-3) correlated exponentially with the ability of respective ligands to induce IP3 formation. ET-1-induced IP3 formation by HBEC was inhibited by the ETA receptor antagonist, BQ123. The protein kinase C activator phorbol myristate ester dose-dependently inhibited the ET-1-stimulated production of IPs, whereas pertussis toxin was ineffective. Cyclic AMP production by HBECs was enhanced by both phorbol myristate ester and ET-1, and potentiated by combined treatment with ET-1 and phorbol myristate ester. Data indicate that protein kinase C plays a role in regulating the ET-1-induced activation of phospholipase C, whereas interaction of different messenger systems may regulate ET-1-induced accumulation of cyclic AMP. ET-1 also stimulated endothelial prostaglandin F2 alpha production, suggesting that activation of phospholipase A2 is most likely secondary to IP3-mediated intracellular calcium mobilization because both ET-1-induced IP3 and prostaglandin F2 alpha were inhibited by BQ123. These findings are the first demonstration of ET-1 (ETA-type) receptors linked to phospholipase C and phospholipase A2 activation in HBECs.
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PMID:Endothelin-1 receptor binding and cellular signal transduction in cultured human brain endothelial cells. 829 22

1. The relationship between muscarinic receptor-mediated phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown and the increase of intracellular Ca2+ ([Ca2+])i has been examined in canine cultured tracheal smooth muscle cells (TSMCs). 2. Addition of acetylcholine (ACh) and carbachol led to a 2-3 fold increase in [Ca2+]i over the resting level as determined by fura-2, with half-maximal stimulation (EC50) obtained at concentrations of 97 and 340 nM, respectively. Addition of the partial agonist, bethanechol, showed a smaller increase in PIP2 turnover and [Ca2+]i than did ACh or carbachol. 3. Addition of ACh or carbachol to TSMCs that had been prelabelled with [3H]-inositol led to the rapid (5-15 s) release of inositol mono, bis and trisphosphates IP1, IP2 and IP3. The time course of IP3 accumulation is correlated with the time course of the peak rise in [Ca2+]i. 4. Inclusion of EGTA lowered the resting [Ca2+]i and markedly reduced the extent of the agonist-induced rise in [Ca2+]i. When assayed under conditions similar to those used for the [Ca2+]i measurements, EGTA reduced the muscarinic agonist-stimulated inositol phosphates (IPs) accumulation. Conversely, ionomycin could stimulate IPs accumulation and elevate [Ca2+]i. The addition of Ca2+ (2.7-617 nM) to digitonin-permeabilized TSMCs directly stimulated IPs accumulation. 5. Both Ca2+ and guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S) stimulated the formation of IPs in digitonin-permeabilized TSMCs prelabelled with [3H]-inositol. A further calcium-dependent increase in IPs accumulation was obtained by inclusion of either GTP gamma S or carbachol. The combined presence of carbachol and GTP gamma S elicited a synergistic effect on IPs accumulation, with half-maximal stimulation observed at approximately 8 nM free Ca2+.6. These results indicate that (i) the magnitude of the initial rise in [Ca2+], is directly related to the production of IPs and (ii) the phospholipase C-mediated PIP2 breakdown in TSMCs is sensitive to regulation by physiologically relevant concentrations of free Ca2+ ([Ca2+]f).
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PMID:Muscarinic regulation of cytosolic free calcium in canine tracheal smooth muscle cells: Ca2+ requirement for phospholipase C activation. 829 14

Inositol phosphate formation was examined in aluminium-treated murine neuroblastoma cells labelled with [3H]-myoinositol. Employing fluoride-stimulated intact cells, aluminium (0.2 microM to 1 mM) reduced inositol phosphate formation in a dose-dependent manner. In digitonin-permeabilized cells, stimulated with nonhydrolyzable GTP[S], inositol phosphate formation was also inhibited by increasing aluminium doses; the IC50 value was about 20 microM aluminium, while the inositol phosphate level was reduced 2.5 to 3 fold by 50 microM aluminium. The inhibitory effect of aluminium (50 microM) could not be reversed by increasing GTP[S] concentrations up to 500 microM. Prechelation of aluminium to citrate or EGTA completely abolished the aluminium-triggered inhibition of fluoride-stimulated inositol phosphate formation in intact cells, but had little effect on the inhibition of permeabilized cells stimulated with GTP[S]. In neuroblastoma cells phosphoinositide hydrolysis could be evoked either through a pathway involving the Mg2+/guanine nucleotide binding (Gp) protein, or via a pathway operative in the presence of high intracellular Ca2+ concentrations. In the Mg2+/Gp protein-mediated pathway, formation of inositol triphosphate, IP3, inositol diphosphate, IP2, and inositol monophosphate, IP, was apparently inhibited by aluminium in an interdependent manner. As to the Ca(2+)-mediated pathway, aluminium application mainly diminished the release of IP3. Following interiorization, aluminium thus acts upon elements critical for phosphoinositide-associated signal transduction. An aluminium target apparently resides on the Gp protein. Phosphatidylinositol-4,5-diphosphate-specific phospholipase C probably harbours a second aluminium target.
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PMID:Aluminium impacts elements of the phosphoinositide signalling pathway in neuroblastoma cells. 839 Nov 23

The cellular content of phosphatidic acid can increase in response to several agonists either by phosphorylation of diacylglycerol after phospholipase C-catalyzed hydrolysis of phospholipids or directly through activation of phospholipase D. Although previous findings indicated that the generation of phosphatidic acid was exclusively a means of regulation of the cellular concentration of diacylglycerol, more recent studies have indicated that phosphatidic acid may also directly regulate several cellular functions. Accordingly, the present study was performed to assess whether phosphatidic acid could stimulate cardiac phospholipase C in intact adult rabbit ventricular myocytes. The mass of inositol 1,4,5-trisphosphate [Ins (1,4,5)P3] was determined by a specific and sensitive binding protein assay and by direct mass measurement using anion exchange chromatography for separation of selected inositol phosphates and gas chromatography and mass spectrometry for quantification of inositol monophosphate (IP1), inositol bisphosphate (IP2), inositol trisphosphate (IP3), and inositol tetrakisphosphate (IP4). Phosphatidic acid (10(-9)-10(-6) M) elicited a rapid concentration-dependent increase in Ins (1,4,5)P3 accumulation, with the peak fourfold to fivefold increase at 30 seconds of stimulation; the concentration required for 50% of maximal stimulation was 4.4 x 10(-8) M. The time course of individual inositol phosphates indicated a successive increase in the mass of IP3, IP4, IP2, and IP1 in response to stimulation with phosphatidic acid. The production of Ins (1,4,5)P3 in response to phosphatidic acid was not altered in the absence of extracellular calcium or in the presence of extracellular EGTA (10(-3) M). Thus, these findings indicate that phosphatidic acid is a potent activator of inositol phosphate production in adult ventricular myocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Phosphatidic acid stimulates inositol 1,4,5-trisphosphate production in adult cardiac myocytes. 843 93

The aim of this study deals with the post-receptor events involved in the response of cultured smooth muscle (SMC) from human bronchi to various agonists of the contraction. [3H]inositol phosphates (IPs) were isolated by high performance liquid chromatography (HPLC) and intracellular Ca2+ concentration ([Ca2+]i) was determined with the Fura-2 fluorescence technique. Following 5 sec stimulation with histamine, an elevation of several [3H]IPs, in particular [3H]1,4-IP2, [3H]1,4,5-IP3 and [3H]1,3,4,5-IP4, above the control values was observed. Following an incubation of 10 or 15 sec with histamine, the content of [3H]1,4,5-IP3 declined towards its basal value, while the amount of metabolites ([3H]4-IP, [3H]1,4-IP2, [3H]1,3,4-IP3) increased with time; [3H]1,3,4,5-IP4 varied little between 5 and 10 sec and decreased at 15 sec. SMC responded also to carbachol and to prostaglandin F2 alpha (PGF2 alpha) by an enhanced production of [3H]IPs, whereas neurokinin A (NKA) had no effect on the turnover of [3H]IPs. Histamine, carbachol and PGF2 alpha evoked a transient elevation in [Ca2+]i, followed by a sustained increase. The duration of the transient elevation appeared similar to that of the increase in [3H]1,4,5-IP3. These results suggest that the 'phospholipase C-1,4,5-IP3-Ca2+ release' signalling pathway is involved in the physiological response of human airway SMC to histamine, carbachol and PGF2 alpha.
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PMID:Signal transduction in smooth muscle cells from human airways. 846 52

Both gastrin and cholecystokinin (CCK) can stimulate pepsinogen release from chief cells, but controversy exists about the receptors or intracellular mediators involved. In the present study, we prepared isolated chief cells from guinea pig stomach (> 90% pure) to investigate the ability of gastrin and CCK to alter cell function. The COOH-terminal octapeptide of CCK (CCK-8) caused an eightfold increase in pepsinogen release (EC50, 54 nM). Both CCK-8 and gastrin increased inositol phosphates, with CCK-8 (1 microM) and gastrin (3 microM) causing a 40- and 14-fold increase in [3H]IP1, 10- and 6-fold for [3H]IP2, and 8- and 4-fold for [3H]IP3. CCK-8 caused a half-maximal increase in [3H]IP3 at 2 nM, and the dose-response curve was monophasic, whereas with gastrin the curve was biphasic, with an EC50 of the initial component (20% maximal) at 38 nM and the second component at 10 microM. L-364,718 (0.1 microM) inhibited the secondary increase seen with gastrin concentrations > 10 nM. The CCK-A-selective agonist A-71378 was 85-90% as efficacious as CCK-8 and was equally potent. With 0.1 microM L-364,718, A-71378 caused no increase in [3H]inositol phosphates until > 10 nM, whereas CCK-8 caused 15% of maximal increase at concentrations > 0.3 nM. Similar results were obtained with cytosolic calcium measured using fura-2 or on CCK-8- or gastrin-stimulated pepsinogen release. These results demonstrate that gastrin and CCK-8 can alter chief cell function by interacting with either a CCK-A or CCK-B/gastrin receptor. Both receptors are coupled to phospholipase C and cause changes in inositol phosphates, cytosolic calcium, and pepsinogen release; however, the intracellular amplification differs between the two receptor subtypes. Activation by CCK-related peptides of the CCK-A receptor subtype accounts for 85-90% of the maximal changes in cellular function, and activation of the CCK-B/gastrin receptor accounts for 10-20% of maximal changes.
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PMID:Gastrin and CCK activate phospholipase C and stimulate pepsinogen release by interacting with two distinct receptors. 847 56

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

Of the various arachidonate cyclooxygenation eicosanoids synthesized in the normal and injured renal glomerular capillary, prostaglandin F2alpha (PGF2alpha) is the most abundant and potent in eliciting signaling events and biologic responses including contraction and proliferation of glomerular capillary pericytes known as mesangial cells. The regulation of PGF2alpha-induced signaling in these cells is unknown. The present studies assessed two key signaling events in response to PGF2alpha in mesangial cells; activation of phospholipase C (PLC) and protein kinase C (PKC). Mechanisms regulating PLC activation were also explored. Incubation of cultured growth arrested rat mesangial cells with PGF2alpha (1 microM) resulted in activation of a phosphatidyl inositol-specific phospholipase C (PI-PLC) assessed as increased generation of polyphosphates in myo-[3H]-inositol-labeled cells and as increased diacylglycerol (DAG) mass levels measured by a radioenzymatic assay. Generation of both inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate occurred, the former constituting 70% of total inositol trisphosphates. Enhanced generation of inositol 1,4-bisphosphate (IP2) also occurred and was greater than that of inositol 1,4,5-trisphosphate (IP3), indicating that PI-PLC utilized the phosphatidyl inositol monophosphate (PIP) to a greater extent than the phosphatidyl inositol bisphosphate (PIP2) substrate. Generation of DAG in response to PGF2alpha occurred in a biphasic pattern characterized by an early transient rise that peaked concomitantly with IP3 at 15 sec, and a late sustained increase at 2, 5, and 15 min that was not associated with an increase in IP3. PGF2alpha also activated PKC assessed as translocation of enzyme activity from cytosolic to membrane fractions. Inhibition of PKC using H-7 enhanced PGF2alpha-induced generation of IP3 at 15 sec but attenuated generation of DAG at 15 min. A more selective PKC inhibitor, Calphostin C, dose-dependently increased basal IP3 generation and also attenuated generation of DAG in response to PGF2alpha. This indicates that PKC negatively modulates PGF2alpha-induced PI-PLC activation, and that the late sustained DAG generation in response to PGF2alpha is regulated by a PKC-dependent phospholipase other than PLC. The mechanisms of PI-PLC stimulation in response to PGF2alpha were further explored using inhibitors of protein tyrosine phosphorylation and of guanine nucleotide-binding (G) protein activation. Inhibition of protein tyrosine phosphorylation using genistein had no effect on IP3 or DAG generation. ADP ribosylation of Gi using pertussis toxin (PTx) had no effect on IP3 generation in response to PGF2alpha. The inhibitor of receptor-coupled PI-PLC activation aminosteroid compound U-73122 that blocks G(PLC) was also ineffective. The observations indicate that PGF2alpha stimulates a PI-PLC which is under negative feedback regulatory control by PKC, and a phospholipase other than PLC which is under positive regulatory control by PKC. PGF2alpha-induced PI-PLC activation is independent of protein tyrosine phosphorylation and of PTx-sensitive G proteins.
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PMID:PGF2alpha-induced signaling events in glomerular mesangial cells. 865 Feb 55

Cholinergic pathways serve important functions in learning and memory processes, and deficits in cholinergic transmission occur in Alzheimer disease (AD). A subset of muscarinic cholinergic receptors are linked to G-proteins that activate phospholipase C, resulting in the liberation of inositol trisphosphate and Ca2+ release from intracellular stores. We now report that amyloid beta-peptide (Abeta), which forms plaques in the brain in AD, impairs muscarinic receptor activation of G proteins in cultured rat cortical neurons. Exposure of rodent fetal cortical neurons to Abeta25-35 and Abeta1-40 resulted in a concentration and time-dependent attenuation of carbachol-induced GTPase activity without affecting muscarinic receptor ligand binding parameters. Downstream events in the signal transduction cascade were similarly attenuated by Abeta. Carbachol-induced accumulation of inositol phosphates (IP, IP2, IP3, and IP4) was decreased and calcium imaging studies revealed that carbachol-induced release of calcium was severely impaired in neurons pretreated with Abeta. Muscarinic cholinergic signal transduction was disrupted with subtoxic levels of exposure to AP. The effects of Abeta on carbachol-induced GTPase activity and calcium release were attenuated by antioxidants, implicating free radicals in the mechanism whereby Abeta induced uncoupling of muscarinic receptors. These data demonstrate that Abeta disrupts muscarinic receptor coupling to G proteins that mediate induction of phosphoinositide accumulation and calcium release, findings that implicate Abeta in the impairment of cholinergic transmission that occurs in AD.
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PMID:Amyloid beta-peptide disrupts carbachol-induced muscarinic cholinergic signal transduction in cortical neurons. 869 90


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