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)

We show that lipopolysaccharide-free actetylated low-density lipoprotein (LDL), but not native LDL, stimulates tumor-necrosis factor-alpha (TNF-alpha) secretion by rat peritoneal macrophages and the signal-transduction pathways involved. The role of the scavenger receptor (SR) in this response was suggested by the absence of an effect induced by native LDL, signal coupling involving pertussis-toxin-dependent guanine-nucleotide-binding regulatory (G) protein, and the complete inhibition of this response by SR ligands [poly(I) and dextran sulfate]. Acetylated LDL induces rapid Ca2+ release from inositol-phosphate-sensitive Ca2+ stores mediated by pertussis-sensitive G proteins and a sustained Ca2+ rise mediated by Ca2+ influx and by Ca2+ release from ryanodine-sensitive Ca2+ stores. Acetylated LDL-induced Ca2+ influx and TNF-alpha production were abolished by inhibitors of phospholipase C (U73122) and phospholipase A2 (bromophenacyl bromide), but were not affected by an inhibitor of protein kinase C (calphostine C). Therefore, Ca2+ influx induced by acetylated LDL is dependent on Ca2+ store depletion. Arachidonate released by acetylated LDL acts as a second messenger to activate TNF-alpha secretion via Ca2+ influx. While the Ca2+ signal was not modified by an inhibitor of protein tyrosine kinases (PTK; herbimycin A), this inhibitor completely blocked TNF-alpha production, suggesting the involvement of PTK downstream of the Ca2+ signal. These results suggest that a sustained elevation of intracellular Ca2+, mediated through Ca2+ influx via the phospholipase-A2-dependent pathway, is essential for induction of TNF-alpha secretion. The type of SR class involved in these pathways remains to be identified.
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PMID:Involvement of calcium and arachidonate metabolism in acetylated-low-density-lipoprotein-stimulated tumor-necrosis-factor-alpha production by rat peritoneal macrophages. 957 94

Mastoparan, a peptide toxin from wasp venome, mimics receptors by stimulating the GTPase activity of guanine nucleotide binding proteins and the G-protein-coupled phospholipase C (PLC). By using Mas-7, the active analog of mastoparan, we showed that it makes pores in the plasma membrane. Treatment with Mas-7 but not Mas-17, the inactive analog, produced a concentration-dependent rise in intracellular Ca2+ concentration ([Ca2+]i) and facilitated the uptake of ethidium bromide (EtBr) (314 Da) to a sustained level during the stimulation. In addition, Mas-7 triggered the influx of lucifer yellow (457 Da), while it did not induce the influx of fura-2 (831 Da) and Evans blue (961 Da). However, the Mas-7-induced permeability was selectively prevented by the addition of La3+, Ni2+, and Co2+, but not Cd2+. This blocking activity was concentration-dependent. While the stimulatory effect of Mas-7 on PLC activity was dependent on extracellular Ca2+, the pore forming activity of Mas-7 was not effected by removal of extracellular Ca2+. These results, therefore, suggest that the mastoparan's action in pore formation is independent from its action in PLC stimulation and is negatively effected by inorganic cations.
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PMID:Characterization of Mas-7-induced pore formation in SK-N-BE(2)C human neuroblastoma cells. 963 47

Purinoceptor agonists produced potassium currents with the order of potency: ATP > adenosine = ADP = AMP > beta,gamma-methylene ATP, while a small response or no response was induced by 2-methylthio ATP, UTP, or alpha,beta-methylene ATP. The response induced by beta,gamma-methylene ATP was completely inhibited in the presence of alpha,beta-methylene ATP, suggesting that the relevant receptor for these agonists was a P3 purinoceptor. ATP induced currents with a latency of 24 s and the currents were not induced in defolliculated oocytes. The currents were not affected by either the Gi/o-protein inhibitor, pertussis toxin (PTX), or the selective cAMP-dependent protein kinase inhibitor, H-89, or the phospholipase C (PLC) inhibitor, neomycin, or the phospholipase A2 (PLA2) inhibitor, 4-bromophenacyl bromide. The currents were enhanced by the selective protein kinase C (PKC) inhibitor, GF109203X, but otherwise, they were reduced by the potent PKC activator, 12-O-tetradecanoylphorbol-13-acetate. The results of the present study suggest that a P3 purinoceptor in the follicle cell layer of oocytes is involved in activation of potassium channels and that the evoked currents are regulated by PLC/PLA2-independent PKC activation.
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PMID:ATP produces potassium currents via P3 purinoceptor in the follicle cell layer of Xenopus oocytes. 965 60

A multiplex polymerase chain reaction (PCR) assay, developed to detect the alpha-toxin and enterotoxin genes (cpa and cpe, respectively) of Clostridium perfringens, was used to identify enterotoxigenic isolates of this organism from feces and intestinal contents of pigs and from feed samples from pig farms in Iowa. The organism was grown on tryptose-sulfite-cycloserine (TSC) agar, TSC agar without egg-yolk, sheep blood agar, or in brain heart infusion broth or cooked meat medium. DNA was extracted by boiling and the PCR assay was carried out using reagents from a commercial kit. The 319 bp amplification product of cpa and the 364 bp product of cpe were visualized under UV light after electrophoresis in a 2% agarose gel containing ethidium bromide. The average sensitivity of the assay, determined on artificially contaminated feces, was 9.2 x 10(4) colony forming units per gram. Assay of 97 isolates from feces and intestinal contents revealed cpa in 89, but all were negative for cpe. While 28% of the 442 total samples cultured yielded C. perfringens, only 5% of 298 fecal or intestinal contents samples were positive upon direct examination by the PCR assay. Ninety-one and eight-tenths % of isolates with the phenotype of C. perfringens were cpa positive by PCR. Forty-three percent of feed samples were culture positive, while 48.3% were PCR positive for cpa. None of these were cpe positive. We conclude that PCR is a useful assay for rapid detection of C. perfringens in feed, and for confirmation of the identity of isolates presumed to be C. perfringens.
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PMID:Multiplex PCR assay for detection of Clostridium perfringens in feces and intestinal contents of pigs and in swine feed. 981 Jun 19

Light-sensitive channels encoded by the Drosophila transient receptor potential-like gene (trpl) are activated in situ by an unknown mechanism requiring activation of Gq and phospholipase C (PLC). Recent studies have variously concluded that heterologously expressed TRPL channels are activated by direct Gq-protein interaction, InsP3 or Ca2+. In an attempt to resolve this confusion we have explored the mechanism of activation of TRPL channels co-expressed with a PLC-specific muscarinic receptor in a Drosophila cell line (S2 cells). Simultaneous whole-cell recordings and ratiometric Indo-1 Ca2+ measurements indicated that agonist (CCh)-induced activation of TRPL channels was not always associated with a rise in Ca2+. Internal perfusion with BAPTA (10 mM) reduced, but did not block, the response to agonist. In most cases, releasing caged Ca2+ facilitated the level of spontaneous channel activity, but similar concentrations (200-500 nM) could also inhibit TRPL activity. Releasing caged InsP3 invariably released Ca2+ from internal stores but had only a minor influence on TRPL activity and none at all when Ca2+ release was buffered with BAPTA. Caged InsP3 also failed to activate any light-sensitive channels in situ in Drosophila photoreceptors. Two phospholipase C inhibitors (U-73122 4 microM and bromo-phenacyl bromide 50 microM) reduced both spontaneous and agonist-induced TRPL activity in S2 cells. The results suggest that, as in situ, TRPL activation involves G-protein and PLC; that Ca2+ can both facilitate and in some cases inhibit TRPL channels, but that neither Ca2+ nor InsP3 is the primary activator of the channel.
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PMID:Activation of heterologously expressed Drosophila TRPL channels: Ca2+ is not required and InsP3 is not sufficient. 988 70

Phosphatidic acid (PA), which can be synthesized de novo, or as a product of phosphatidylcholine hydrolysis and/or phosphorylation of 1,2-diacylglycerol (DAG), mediates diverse cellular functions in various cell types, including cardiomyocytes. We set out to characterize the effect of PA on intracellular free calcium ([Ca2+]i) and inositol-1,4,5-trisphosphate (IP(3)) levels in primary cultures of neonatal rat cardiomyocytes. Addition of PA led to rapid, concentration and time dependent increases in both IP(3) and [Ca2+]i levels in adherent cells. There was strong correlation in the concentration-response relationships between IP(3) and [Ca2+]i increases evoked by PA. Incubation with the sarcoplasmic reticulum (SR) Ca2+ pump inhibitor, cyclopiazonic acid (CPA), significantly attenuated the PA evoked [Ca2+]i increase but had no significant effect on IP(3) accumulation. The phospholipase C (PLC) inhibitor, D-609, attenuated both IP(3) and [Ca2+]i elevations evoked by PA whereas staurosporine (STS), a potent and non-selective PKC inhibitor, had no significant effect on either. Another PLC inhibitor, U73122, but not its inactive analog, U73343, also inhibited PA evoked increases in [Ca2+]i. Depletion of extracellular calcium attenuated both basal and PA evoked increases in [Ca2+]i. The PLA(2) inhibitors, bromophenylacyl-bromide (BPB) and CDP-choline, had no effect on PA evoked [Ca2+]i responses. Neither the DAG analog, dioctanoylglycerol, nor the DAG kinase inhibitor, R59949, affected PA evoked changes in [Ca2+]i. Taken together, these data indicate that PA, in a manner independent of PKC, DAG, or PLA(2), may enhance Ca2+ release from IP(3) sensitive SR Ca(2+) stores via activation of PLC in neonatal rat cardiomyocytes.
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PMID:Phosphatidic acid increases inositol-1,4,5,-trisphosphate and [Ca2+]i levels in neonatal rat cardiomyocytes. 1047 28

In an evaluation of the contribution of swelling-induced amino acid release, through the regulatory volume decrease (RVD) process, to cerebral ischemic injury, studies of the role of phospholipases and protein kinases in the response to hyposmotic stress were undertaken using an in vivo rat cortical cup model. Hyposmotic stress induced significant releases of aspartate, glutamate, glycine, phosphoethanolamine, taurine and GABA from the rat cerebral cortex. Taurine release was most affected, exhibiting a greater than 9-fold increase during the hyposmotic stimulus. The phospholipase A2 (PLA2) inhibitors 4-bromophenacyl bromide (1 microM) and 7,7-dimethyleicosadienoic acid (5 microM) had no significant effects on hyposmotically induced amino acid release. AACOCF3 (50 microM), an inhibitor of cytosolic PLA2 decreased taurine release to 84% of DMSO controls. The release of the other amino acids was not affected. The phospholipase C inhibitor U73122 (5 microM) had no significant effects on amino acid release. The protein kinase C (PKC) inhibitor chelerythrine (5 microM) significantly reduced hyposmotically induced taurine release to 72% of saline controls but had no significant effects on the other amino acids. Stimulation of PKC with phorbol 12-myristate, 13-acetate (10 microM) did not significantly change taurine, glutamate, glycine or phosphethanolamine release. The releases of aspartate and GABA were enhanced 2 to 3 fold. Phorbol 12,13-didecanoate (10 microM), another potent stimulator of PKC, significantly increased taurine release to 122% of DMSO controls. The releases of aspartate, glutamate and glycine were enhanced 2.5 to 3.5 fold. Similarly, stimulation of protein kinase A with forskolin (100 microM) significantly increased taurine, aspartate, and glycine release 1.5- to 2-fold compared to DMSO controls. In summary, phospholipases may play a minor role in volume regulation. These studies also support the hypothesis that protein kinases play a modulatory role in the RVD response. The results show that although RVD may play a role, additional mechanisms, including phospholipase activation, must be involved in the ischemia-evoked release of excitotoxic amino acids.
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PMID:Hyposmotically induced amino acid release from the rat cerebral cortex: role of phospholipases and protein kinases. 1053 55

A Shigella flexneri strain, cured of the large 220-kb virulence plasmid, expresses adhering and invading ability in confluent monolayers of HeLa cells similar to its parent strain. Invasion by both the parent and the cured strains resulted in alteration of the monomeric actin (G) in the total actin pool of HeLa cells. Other indicators of invasive characteristics of virulent Shigella strains such as production of keratoconjunctivitis in guinea pig eye in vivo, Congo red binding and expression of contact hemolysin however, indicated loss of invasive properties in the plasmid cured strain. Further, pretreatment of bacterial cells with para-bromophenacyl bromide (p-BPB), a specific chemical inhibitor of phospholipase A, adversely affected adhesion to and invasion of HeLa cells in vitro, irrespective of the presence of the 220-kb plasmid indicating the possible involvement of the enzyme phospholipase A in the invasion process. Adherence of both the strains to guinea pig colonic epithelial cells (CECs) in vitro was reduced significantly on pretreatment of bacteria or CECs with p-BPB. Expression of exocellular enzymes viz. protease, elastase, phospholipase A and phospholipase C were not related to the large plasmid.
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PMID:Adhesion and invasion of a mutant Shigella flexneri to an eukaryotic cell line in absence of the 220-kb virulence plasmid. 1058 48

Treatment of human natural killer (NK) cells with phospholipase A(2) (PLA(2)) inhibitors, mepacrine and 4-bromophenacyl bromide (BPB), diminished their ability to lyse K562 target cells by as much as 100%. The ability of NK cells to bind to K562 cells was significantly affected by BPB above 2 microM, but not by mepacrine at any concentration tested. This indicates that BPB is having effects on NK cells unrelated to its inhibition of PLA(2) activity at concentrations above 2 microM. The activation of phospholipase C in response to K562 cell binding (as measured by inositol phosphate turnover) was unaffected by inhibition of the PLA(2) activity. The products of PLA(2) catabolism are a fatty acid (often arachidonic acid) and a lysophospholipid. Inhibition of NK cytotoxicity by mepacrine or BPB is reversed significantly when lysophosphatidylcholine, but no other lysolipid, is added back to the NK cells before assaying for cytotoxicity. Arachidonic acid, but not linoleic acid, also significantly reverses inhibition of NK cytotoxicity. Finally, the 15-lipoxygenase product, 15S-hydroperoxyeicosatetraenoic acid (15S-HPETE), is also able to reverse mepacrine-induced inhibition of NK cytotoxicity. The 5-lipoxygenase product 5S-HPETE was not effective. These data indicate that PLA(2) activation is a necessary signal in human NK cytotoxicity and that it is not involved in protein tyrosine kinase and subsequent phospholipase C activation; these latter two enzymes are also required in the cytotoxic response. Thus PLA(2) activation is either a more distal signal, dependent on activation of some earlier signal, or an independent cosignal stimulated by tumor-target binding which generates lysophosphatidylcholine, arachidonic acid, and/or a lipoxygenase product(s).
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PMID:Lysophosphatidylcholine and arachidonic acid are required in the cytotoxic response of human natural killer cells to tumor target cells. 1074 96

The unicellular Tetrahymena enzymatically split the synthetic phosphodiester, 4-methylumbelliferyl phosphocholine substrate. The enzyme activity was completely blocked in vitro and drastically inhibited in vivo by G-protein activating fluorides (NaF; AIF4- and BeF3-). The phospholipase A2 inhibitor, quinacrine, and the protein phosphatase inhibitor, neomycin, inhibited the enzyme activity in vitro and activated it in vivo. Another phospholipase A2 inhibitor 4-bromo phenacyl bromide was ineffective in vivo and in vitro alike, as well as the cyclooxygenase inhibitor indomethacin. Results of these experiments indicate that some treatments could be specific for a well defined activity (e.g., phospholipase A2, G-protein) but subject to influence by other enzymes (e.g., phospholipase C, sphingomyelinase). The experiments call attention to the differences in the results of the in vivo and in vitro studies.
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PMID:Fluorimetric analysis of phospholipase activity in Tetrahymena pyriformis GL. 1088 70


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