Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.3 (phospholipase C)
 18,461 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Membrane currents were recorded by a patch-clamp pipette technique in cultured cells from rat portal vein using the whole-cell mode. 2. Noradrenaline (NA, 10(-5) M) and phorbol-12,13-dibutyrate (PDBu, 10(-7) M) produced an increase in voltage-dependent inward current carried by barium (5 mM), but their effects were not additive. Calcium-activated chloride current was evoked by NA but not by PDBu. 3. The NA-induced increase in peak voltage-dependent inward current was inhibited by intracellular application of GDP-beta-S (10(-3) M) while the effect of PDBu was unchanged. GDP-beta-S blocked the NA-induced chloride current but had no effect on the caffeine-induced chloride current. 4. Inclusion of GTP-gamma-S (10(-5)-10(-4) M) in the pipette solution increased the voltage-dependent inward current and inhibited the NA- or PDBu-induced increase in peak current. GTP-gamma-S potentiated the effect of NA on calcium-activated chloride current. At higher concentrations (10(-3) M), GTP-gamma-S activated the chloride current and prevented the effects of NA or caffeine on this current. 5. The combination of 10(-5) M-aluminium chloride and 10(-2) M-sodium fluoride had an effect similar to that of high concentrations of GTP-gamma-S on both inward current and calcium-activated chloride current. In contrast, arachidonic acid (10(-3) M) had no effect on calcium and chloride conductances activated by NA. 6. Cells responded normally to NA after pre-treatment for 4-30 h with 10 micrograms ml-1 pertussis toxin (PTx). 7. It is concluded that the stimulation of calcium and chloride conductances by NA is mediated through activation of a PTx-insensitive GTP-binding protein. This effect may involve activation of phospholipase C enzyme and production of both D-myo-inositol 1,4,5-trisphosphate which depletes calcium stores and diacylglycerol which activates protein kinase C.
 ...
PMID:GTP-binding proteins mediate noradrenaline effects on calcium and chloride currents in rat portal vein myocytes. 170 Jan 11

Factor X-activating activity (FXAA) was determined by a chromogenic assay in normal and malignant breast tissue. FXAA was found in all tissue (n = 38) irrespective of pathology, and the activity of normal tissue was similar to that of tumours. FXAA correlated with tissue hemoglobin in normal breast (p less than 0.02) but not in tumours. FXAA was markedly reduced by aluminium hydroxide, barium citrate, anti-human factor VII, DFP, PMSF and phospholipase C, but was unaffected by iodoacetamide and mercuric chloride. It is concluded that FXAA is a serine protease with the properties of a tissue factor-factor VII complex. FXAA occurs in normal and malignant breast tissue, although the 'normal' activity may be an artefact of the homogenization process.
 ...
PMID:Factor X-activating procoagulant in normal and malignant breast tissue. 228 55

Hemolymph (blood) of an insect, the tobacco hornworm, Manduca sexta, contains a phospholipase A1. The specificity of this enzyme was demonstrated by the use of substrates with labeled fatty acids in specific positions and by conversion of the enzyme product, a lysophospholipid, to 2-acylglycerol by the action of bacterial phospholipase C. The insect phospholipase A1 hydrolyzes phosphatidylethanolamine and phosphatidylglycerol, but not phosphatidylcholine or triolein. Divalent cation is required, with calcium ion being most effective, although strontium, barium, and magnesium ions also support activity. Only substrates dispersed in buffer from ethanol are hydrolyzed; ether, Triton X-100, and taurodeoxycholate are inhibitory. The enzyme has been purified 90-fold. At that stage, it is still far from homogeneous, but stability problems have hindered further purification. It has an apparent Mr = 155,000 +/- 11,000, estimated by gel permeation chromatography.
 ...
PMID:A phospholipase A1 from the hemolymph of the tobacco hornworm, Manduca sexta. 683 59

The effects of extracellular divalent cations on the intracellular Ca2+ concentration ([Ca2+]i) in neonatal rat islet cells were investigated to determine whether these cells, like several others, have signal-generating surface cation sensors. Raising the external Ca2+ concentration by 1 mM increments triggered either sustained increases in [Ca2+]i or large sharp [Ca2+]i spikes followed by return to a suprabasal level. The external Ca(2+)-triggered [Ca2+]i responses were abolished by treating the cells with the inhibitor of inositol phospholipid hydrolysis, neomycin (1.5 mM), but not by another phospholipase C inhibitor, U-73,122 (2.5 microM), or the voltage-sensitive Ca2+ channel blockers nifedipine (20 microM) and methoxyverapamil (D600; 50 microM). [Ca2+]i responses were also triggered by barium (Ba2+; 1 mM) and cobalt (Co2+; 1 mM). The Ba2+ responses were also inhibited by neomycin and unaffected by nifedipine or D600 and the Co2+ response required external Ca2+. Therefore, neonatal rat pancreatic islet cells may display divalent cation receptors/sensors on their surfaces. Activation of these putative receptors, which are coupled to neomycin-sensitive, voltage-independent, dihydropyridine-insensitive channels, by Ca2+, Ba2+ or Co2+ would trigger [Ca2+]i responses by opening these channels to admit external Ca2+ into the cell. The physiological function(s) of such cell-surface divalent cation receptors/sensors and the [Ca2+]i surges they generate in pancreatic islet cells is not known.
 ...
PMID:Do pancreatic islet cells from neonatal rats have surface receptors or sensors for divalent cations? 851 94

We have determined the crystal structures of complexes of phosphoinositide-specific phospholipase C-delta1 from rat with calcium, barium, and lanthanum at 2.5-2.6 A resolution. Binding of these metal ions is observed in the active site of the catalytic TIM barrel and in the calcium binding region (CBR) of the C2 domain. The C2 domain of PLC-delta1 is a circularly permuted topological variant (P-variant) of the synaptotagmin I C2A domain (S-variant). On the basis of sequence analysis, we propose that both the S-variant and P-variant topologies are present among other C2 domains. Multiple adjacent binding sites in the C2 domain were observed for calcium and the other metal/enzyme complexes. The maximum number of binding sites observed was for the calcium analogue lanthanum. This complex shows an array-like binding of three lanthanum ions (sites I-III) in a crevice on one end of the C2 beta-sandwich. Residues involved in metal binding are contained in three loops, CBR1, CBR2, and CBR3. Sites I and II are maintained in the calcium and barium complexes, whereas sites II and III coincide with a binary calcium binding site in the C2A domain of synaptotagmin I. Several conformers for CBR1 are observed. The conformation of CBR1 does not appear to be strictly dependent on metal binding; however, metal binding may stabilize certain conformers. No significant structural changes are observed for CBR2 or CBR3. The surface of this ternary binding site provides a cluster of freely accessible liganding positions for putative phospholipid ligands of the C2 domain. It may be that the ternary metal binding site is also a feature of calcium-dependent phospholipid binding in solution. A ternary metal binding site might be a conserved feature among C2 domains that contain the critical calcium ligands in their CBR's. The high cooperativity of calcium-mediated lipid binding by C2 domains described previously is explained by this novel type of calcium binding site.
 ...
PMID:A ternary metal binding site in the C2 domain of phosphoinositide-specific phospholipase C-delta1. 906 2

The effect of recombinant human tumor necrosis factor-alpha (TNF) on voltage-gated membrane currents of cultured neurons derived from embryonic rat cerebral cortex was studied using the whole-cell patch-clamp technique. Treatment of neurons with TNF resulted in an increase in outward potassium current density, dependent upon the concentration of TNF and the incubation time, without affecting other membrane currents such as barium and N-methyl-D-aspartate (NMDA). Long exposures (12-48 hr) to TNF (10-100 ng/ml) increased transient outward potassium current (A-current) density without affecting the parameters of activation and inactivation of the current. Prolonged exposures to TNF diminished its increasing effect on the A-current. Since the increase of A-current density induced by TNF is inhibited by both the anti-TNF receptor antibody and cycloheximide treatment, the effect of TNF might be mediated through receptors and by de novo synthesis of the channel protein itself and/or modulating proteins associated with the channel activities. Results indicate that phosphatidylcholine-specific phospholipase C and protein kinase C, but not ceramide, are involved in the signal transduction. In toxicological experiments, TNF had no neurotoxicity. Moreover, a 12 hr pretreatment of TNF protected neurons against NMDA-induced neurotoxicity. This protective effect of TNF was cancelled by 4-aminopyridine, an A-current blocker, suggesting that the increase of A-current densities induced by TNF contributes to the neuroprotection.
 ...
PMID:Tumor necrosis factor enhancement of transient outward potassium currents in cultured rat cortical neurons. 945 13

1. Glutamate suppressed high-voltage-activated barium currents (IBa, HVA) in tiger salamander retinal ganglion cells. Both ionotropic (iGluR) and metabotropic (mGluR) receptors contributed to this calcium channel inhibition. 2. Trans-ACPD (1-aminocyclopentane-trans-1S,3R-dicarboxylic acid), a broad-spectrum metabotropic glutamate receptor agonist, suppressed a dihydropyridine-sensitive barium current. Kainate, an ionotropic glutamate receptor agonist, reduced an omega-conotoxin GVIA-sensitive current. 3. The relative effectiveness of selective agonists indicated that the predominant metabotropic receptor was the L-2-amino-4-phosphonobutyrate (L-AP4)-sensitive, group III receptor. This receptor reversed the action of forskolin, but this was not responsible for calcium channel suppression. l-AP4 raised internal calcium concentration. Antagonists of phospholipase C, inositol trisphosphate (IP3) receptors and ryanodine receptors inhibited the action of metabotropic agonists, indicating that group III receptor transduction was linked to this pathway. 4. The action of kainate was partially suppressed by BAPTA, by calmodulin antagonists and by blockers of calmodulin-dependent phosphatase. Suppression by kainate of the calcium channel current was more rapid when calcium was the charge carrier, instead of barium. The results indicate that calcium influx through kainate-sensitive glutamate receptors can activate calmodulin, which stimulates phosphatases that may directly suppress voltage-sensitive calcium channels. 5. Thus, ionotropic and metabotropic glutamate receptors inhibit distinct calcium channels. They could act synergistically, since both increase internal calcium. These pathways provide negative feedback that can reduce calcium influx when ganglion cells are depolarized.
 ...
PMID:Metabotropic and ionotropic glutamate receptors regulate calcium channel currents in salamander retinal ganglion cells. 966 Aug 96

Mammalian homologues of the Drosophila transient receptor potential (TRP) protein have been proposed to function as ion channels, and in some cases as store-operated or capacitative calcium entry channels. However, for each of the mammalian TRP proteins, different laboratories have reported distinct modes of cellular regulation. In the present study we describe the cloning and functional expression of the human form of TRP4 (hTRP4), and compare its activity with another well studied protein, hTRP3. When hTRP4 was transiently expressed in human embryonic kidney (HEK)-293 cells, basal bivalent cation permeability (barium) was increased. Whole-cell patch-clamp studies of hTRP4 expressed in Chinese hamster ovary cells revealed a constitutively active non-selective cation current which probably underlies the increased bivalent cation entry. Barium entry into hTRP4-transfected HEK-293 cells was not further increased by phospholipase C (PLC)-linked receptor activation, by intracellular calcium store depletion with thapsigargin, or by a synthetic diacylglycerol, 1-oleoyl-2-acetyl-sn-glycerol (OAG). In contrast, transient expression of hTRP3 resulted in a bivalent cation influx that was markedly increased by PLC-linked receptor activation and by OAG, but not by thapsigargin. Despite the apparent differences in regulation of these two putative channel proteins, green fluorescent protein fusions of both molecules localized similarly to the plasma-membrane, notably in discrete punctate regions suggestive of specialized signalling complexes. Our findings indicate that while both hTRP4 and hTRP3 can apparently function as cation channels, their putative roles as components of capacitative calcium entry channels are not readily demonstrable by examining their behaviour when exogenously expressed in cells.
 ...
PMID:Cloning and expression of the human transient receptor potential 4 (TRP4) gene: localization and functional expression of human TRP4 and TRP3. 1104 29

The effect of trichloroethanol (TCEt), the active metabolite of chloral hydrate, on the intracellular concentration of calcium ([Ca(2+)](i)) was investigated in rat submandibular glands (RSMG) acini loaded with fura-2. TCEt (1 - 10 mM) increased the [Ca(2+)](i) independently of the presence of calcium in the extracellular medium. Dichloroethanol (DCEt) and monochloroethanol (MCEt) reproduced the stimulatory effect of TCEt but at much higher concentrations (about 6 fold higher for DCEt and 20 fold higher for MCEt). TCEt mobilized an intracellular pool of calcium, which was depleted by a pretreatment with thapsigargin, an inhibitor of the sarcoplasmic and endoplasmic reticulum calcium-dependent ATPases, but not with FCCP, an uncoupler of mitochondria. TCEt 10 mM inhibited by 50% the thapsigargin-sensitive microsomal Ca(2+)-ATPase. DCEt 10 mM and MCEt 10 mM inhibited the ATPase by 20 and 10%, respectively. TCEt inhibited the increase of the [Ca(2+)](i) and the production of inositol phosphates in response to carbachol, epinephrine and substance P. TCEt inhibited the uptake of calcium mediated by the store-operated calcium channel (SOCC). ATP and Bz-ATP increased the [Ca(2+)](i) in RSMG acini and this effect was blocked by extracellular magnesium, by Coomassie blue and by oxydized ATP (oATP). TCEt potentiated the increase of the [Ca(2+)](i) and of the uptake of extracellular calcium in response to ATP and Bz-ATP. TCEt had no effect on the uptake of barium and of ethidium bromide in response to purinergic agonists. These results suggest that TCEt, at sedative concentrations, exerts various effects on the calcium regulation: (1) it mobilizes a thapsigargin-sensitive intracellular pool of calcium in RSMG acini; (2) it inhibits the uptake of calcium via the SOCC; (3) it inhibits the activation by G protein-coupled receptors of a polyphosphoinositide-specific phospholipase C. It does not interfere with the activation of the ionotropic P2X receptors. The use of chloral hydrate should be avoided in studies exploring the in vivo responses to sialagogues.
 ...
PMID:Multiple effects of trichloroethanol on calcium handling in rat submandibular acinar cells. 1205 35

Binding of an odorant to its receptor activates the cAMP-dependent pathway, and also leads to inositol 1,4,5-trisphosphate (InsP(3)) production. This induces opening of a plasma membrane channel in olfactory receptor cells (ORCs). We investigated single-channel properties of this channel in the presence of a phospholipase C (PLC) activator (imipramine) and of a potent activator of the InsP(3)/Ca(2+) release channel (adenophostin A) by reconstituting carp olfactory cilia into planar lipid bilayers. In the presence of 53 mM barium as a charge carrier, the addition of 50 microM imipramine induced a current of 1.53+/-0.05 pA at 0 mV. There were two different mean open times (6.0+/-0.6 ms and 49.6+/-6.4 ms). The I/ V curve displayed a slope conductance of 50+/-2 pS. Channel activity was transient and was blocked by neomycin (50 microM). These observations suggest that imipramine may activate the olfactory InsP(3)-gated channel through PLC. Using the same ionic conditions, the application of 0.5 microM adenophostin A triggered a current of 1.47+/-0.04 pA at 0 mV. The I/ V curve displayed a slope conductance of 60+/-2 pS. This channel showed only a single mean open time (15.0+/-0.3 ms) and was strongly inhibited by ruthenium red (30 microM) and heparin (10 microg/mL). These results indicate that adenophostin A and imipramine may act on the ciliary InsP(3)-gated channel and are potentially valuable pharmacological tools for studying olfactory transduction mechanisms.
 ...
PMID:Adenophostin A and imipramine are two activators of the olfactory inositol 1,4,5-trisphosphate-gated channel in fish olfatory cilia. 1273 98


1 2 Next >>