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)

Murine Thy-1-negative lymphoma mutants synthesize membrane proteins that normally bear glycolipid anchors but do not express these proteins on the cell surface. This phenotype may reflect altered regulation of gene(s) required for anchor biosynthesis. Since tissue culture cells treated with sodium butyrate transcribe new DNA sequences and since these transcripts are translated, it was of interest to determine whether butyrate treatment could restore surface expression of lipid-anchored proteins. When Thy-1-negative lymphoma mutants (complementation groups A-C, E, F, and H) were cultured for three days in 1.5 mM butyrate, a small percentage of the class H cells acquired phosphatidylinositol-specific phospholipase C-releasable surface Thy-1 and J11d. Membrane-associated Thy-1 was not observed before 24 h of treatment. Induction was reversible. Cell fusion studies have shown that murine LM (TK-) fibroblasts can be assigned to the class H lymphoma complementation group. Although these cells synthesize Ly-6, this normally lipid-anchored protein is absent from the cell surface. When LM (TK-) cells were cultured for three days in butyrate, 10% of the cells reversibly expressed Ly-6. In addition, LM (TK-) cells transfected with a plasmid encoding Thy-1 do not express Thy-1, but could be induced to express both Ly-6 and Thy-1 by butyrate treatment. Northern analysis of total RNA from Ly-6/Thy-1-expressing cells indicates that increased steady-state transcript levels cannot account for surface expression of these proteins. We conclude that the lack of expression of three proteins at the surface of class H mutant and the LM (TK-) cells is not due to gross structural lesions in genes along the anchor biosynthetic pathway.
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PMID:Sodium butyrate causes reexpression of three membrane proteins on glycolipid-anchoring mutants. 167 68

Dopamine receptors of DA-1 and DA-2 subtypes are localized in various regions within the kidney including the renal vasculature (DA-1) as well as sympathetic nerve terminals innervating the renal blood vessels (DA-2). More recent studies using receptor-ligand binding and receptor autoradiography have shown that DA-1 receptors are localized at both the luminal and basolateral membranes at the level of the proximal tubules. Activation of these DA-1 receptors by dopamine and by selective DA-1 receptor agonists results in natriuresis and diuresis. The cellular signaling mechanisms responsible for this response appear to be DA-1 receptor-induced activation of adenylate cyclase and phospholipase C, which via the generation of various intracellular messenger systems cause inhibition of Na(+)-H+ antiport (luminal) and Na+, K(+)-ATPase (basolateral), respectively. Both of these events consequently inhibit sodium reabsorption leading to natriuresis and diuresis. It is also known that dopamine can be synthesized within proximal tubular cells from L-dopa, which is taken up from the tubular lumen, and this locally produced dopamine plays an important role in the regulation of sodium excretion particularly during increases in sodium intake. Furthermore, a defect in the renal dopaminergic mechanism may be one of the pathogenic factors in certain forms of hypertension. Finally, whereas DA-1 receptor agonists are shown to be of therapeutic benefit in the treatment of hypertension, heart failure, and acute renal failure, some selective DA-2 receptor agonists are effective antihypertensive agents.
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PMID:Anatomical distribution and function of dopamine receptors in the kidney. 168 44

Species-specific monoclonal antibodies to Leishmania tropica, T11 and T13-15, recognize membranal and secreted antigens. The membrane form of the antigen migrates on sodium dodecyl sulfate-polyacrylamide gels with a diffuse molecular weight from 15 to 50 kDa and can be labeled with palmitic acid, myoinositol, galactose, glucosamine, and inorganic phosphate. Both phosphate and sugar-labeled material were isolated from metabolically labeled promastigotes by affinity chromatography on antibodies coupled to Sepharose 4B. No binding to Ricinus communis agglutinin was observed. This material behaves like lipophosphoglycans from other Leishmania but contains unique species-specific epitopes. It is susceptible to cleavage by phospholipase C and after digestion no longer partitions into the detergent phase following a Triton X-114 extraction. All four monoclonal antibodies appear to recognize a carbohydrate epitope on the lipophosphoglycan since periodate treatment of this material bound to nitrocellulose essentially eliminated antibody binding. In addition, T15 binding could be blocked by 5 mM mannose-6-PO4 and fructose-1- or 6-PO4, but not by mannose, glucose, fructose, or the additional PO4 derivatives examined. The antibodies recognize a similar but not identical epitope, as demonstrated by a competitive radioimmunoassay using 125I-labeled T11, T13, and T15. Expression of surface antigen is elevated during the promastigote stationary phase.
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PMID:Leishmania tropica: characterization of a lipophosphoglycan-like antigen recognized by species-specific monoclonal antibodies. 168 34

In the present study characterization of phosphatidylinositol 4,5-bisphosphate-specific phospholipase C (PIP2-PLC) activity and receptor-mediated hydrolysis of PIP2 in rat anterior pituitary membranes were investigated. Incubation of the membrane fraction of anterior pituitary homogenate with [3H]inositol-labeled PIP2 in the presence of calcium increased the concentration of the water-soluble degradation product inositol trisphosphate (IP3) in a time-dependent manner. PIP2-PLC in the rat anterior pituitary had a pH optimum at 5.5 and a requirement for cations. Ca2+ and Mg2+ could activate the enzyme. Activity was maximal at a total magnesium concentration of 1 mM and at a free Ca2+ concentration of 100 microM. The addition of the detergent Triton X-100 (0.05% w/v) to the membrane fraction resulted in a 50% decrease of PIP2-PLC activity, whereas the presence of sodium deoxycholate (1 mg/ml) in the membrane fraction increased the PIP2-PLC activity by 100%. The tachykinins substance P, 8-Tyr-substance P, physalaemin, neurokinin A, eledoisin, kassinin and neurokinin B induced receptor-mediated breakdown of [3H]inositol-labeled PIP2 in the membrane fraction in a concentration-dependent manner, but with different potencies. The tachykinins displayed the following rank order of potencies: substance P greater than 8-Tyr-substance P greater than physalaemin greater than neurokinin A greater than eledoisin greater than kassinin greater than neurokinin B, which is consistent with the involvement of a NK-1 receptor. Combined treatment of anterior pituitary membranes by substance P and thyrotropin-releasing hormone (TRH) resulted in an additional increase in PIP2-PLC activity compared to stimulation with TRH alone.
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PMID:Substance P and related tachykinins induce receptor-mediated hydrolysis of polyphosphoinositides in the rat anterior pituitary. 169 Nov 15

1. Cultured aortic endothelial cells of the pig respond to the endothelium-derived relaxing factor (EDRF) they release with an increase in cyclic GMP content. This response is inhibited by haemoglobin or by L-NG-monomethyl-arginine (L-NMMA), and has been used to investigate the effects of phorbol esters on EDRF release. 2. Pretreatment with phorbol-12,13-dibutyrate (PDB) but not the inactive 4 alpha-phorbol-12,13,-didecanoate (PDD), inhibited increases in cyclic GMP induced by substance P (10(-8) M) in a time and concentration-dependent manner. PDB did not affect basal cyclic GMP levels. 3. PDB (3 x 10(-7) M), but not PDD (3 x 10(-7) M), also inhibited ATP (10(-5) M)-induced increases in cyclic GMP, but did not affect those induced by bradykinin (10(-7) M). 4. Increases in cyclic GMP induced by low (10(-7) M) but not high (10(-6) M) concentrations of the calcium ionophore A23187 were inhibited by PDB (3 x 10(-7) M). This inhibitory effect was due to enhanced destruction of EDRF by superoxide anions rather than inhibition of EDRF release, as the inhibition was abolished in the presence of superoxide dismutase (SOD, 30 mu ml-1) and catalase (CAT, 100 mu ml-1). 5. SOD and CAT did not affect the inhibitory action of PDB on substance P or ATP-induced increases in cyclic GMP. 6. Increases in endothelial cell cyclic GMP content induced by sodium nitroprusside (10(-5) M) were unaffected by PDB pretreatment. 7. The inhibitory effects of PDB are probably a result of an action of protein kinase C on the steps between receptor occupation and phospholipase C activation.
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PMID:Release of endothelium-derived relaxing factor from pig cultured aortic endothelial cells, as assessed by changes in endothelial cell cyclic GMP content, is inhibited by a phorbol ester. 169 49

Aerolysin from Aeromonas sobria AB3 was isolated and purified. The pure toxin formed sodium dodecyl sulfate-insoluble oligomers in a lipidic environment. The addition of aerolysin to the aqueous phase bathing lipid bilayer membranes resulted in the formation of ion-permeable channels which had a single-channel conductance of about 70 pS in 0.1 M KCl. This defines the toxin as a channel-forming component similar to other toxins but without any indication for an association-dissociation reaction, since the channels had a long lifetime at low voltages. At voltages higher than 50 mV, the aerolysin channel switched into a closed state with a low residual conductance. The single-channel conductance was a linear function of the total aqueous conductance, which suggested that the toxin oligomers formed aqueous channels with an estimated minimal diameter of about 0.7 nm. The aerolysin pores were found to be slightly anion selective. The pore-forming properties of aerolysin were compared with those of alpha-toxin of Staphylococcus aureus. Both aerolysin and alpha-toxin share secondary structure features, must oligomerize to form pores in lipid bilayer membranes, and form channels with similar properties.
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PMID:Aerolysin of Aeromonas sobria: evidence for formation of ion-permeable channels and comparison with alpha-toxin of Staphylococcus aureus. 169 19

Membrane phospholipase C (PLC) activation is induced by the interaction of numerous vasoactive hormones and growth factors with their receptors. Two products are liberated: inositol triphosphate (IP3) and diacyglycerol (DG). The first product liberates intracellular calcium from its stores in the sarcoplasmic reticulum and the second one activates a phosphokinase, which triggers a transmembrane Na+/H+ exchange. A cascade of metabolic events secondary to these chemical changes impinges on the expression of nuclear proto-oncogenes, which determines cell growth. Studies conducted in spontaneously hypertensive rats (SHRs) have shown that PLC is hyperreactive to various agonists and that the phenomenon is present within a variety of cells, fibroblasts, platelets, and myocytes. Therefore, it is likely that hypertension in SHRs is characterized by a diffuse and intrinsic cellular defect that cannot be considered a consequence of the hemodynamic changes of hypertension. On the one hand, enhanced intracellular calcium mobilization may play a role in arterial tone and contraction whereas, on the other hand, enhanced activation of proto-oncogenes, myc, fos, and jun, may be involved in the mechanisms of arteriosclerosis. The pattern of an evolution towards arterial cell proliferation with acquisition of a secretory phenotype with collagen production was indeed observed in cultured cells from the arterial wall.
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PMID:Hypertension and atherosclerosis. 169 95

Mode of stimulatory action of deoxycholate (DCA) on the secretagogue-induced amylase release and the phospholipase C reaction in isolated rat pancreatic acini was investigated using sodium fluoride (NaF), which is a direct activator of GTP-binding proteins (G proteins). DCA enhanced the amylase release induced by submaximal concentrations of NaF without affecting the maximal level of this reaction. Under the similar conditions, DCA enhanced the NaF-induced phospholipase C reaction. These stimulatory effects of DCA on the NaF-induced amylase release and phospholipase C reaction are comparable to those on the secretagogue-induced reactions reported previously. These results suggest that DCA acts on the coupling of a G protein(s) to the phospholipase C in the membrane transduction mechanism in isolated rat pancreatic acini.
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PMID:Mode of stimulatory action of deoxycholate in signal transduction system of isolated rat pancreatic acini. 169 4

Human erythroleukemia (HEL) cells phosphorylate [3H]inositol 1,4,5-trisphosphate to inositol 1,3,4,5-tetrakisphosphate; they also contain all the enzymes to sequentially dephosphorylate [3H]inositol 1,4,5-trisphosphate and [3H]inositol 1,3,4,5-tetrakisphosphate to inositol. alpha-Thrombin, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, and sodium fluoride caused the formation of [3H]inositol phosphates in HEL cells that were previously labeled with [3H]inositol. This indicates agonist-induced activation of phospholipase C and hydrolysis of the inositol phospholipids. Pretreatment of the HEL cells with iloprost, a prostacyclin analog that increases cellular cyclic AMP levels, dramatically reduced the formation of inositol phosphates and the increase of [3H]phosphatidylinositol 4,5-bisphosphate. The inhibitory effects of iloprost were associated with the phosphorylation of a 24-kDa protein, which was detected with an antiserum obtained against the rap 1 protein. The catalytic subunit of protein kinase A inhibited formation of polyphosphoinositides during phosphorylation of the rap 1 protein in membranes. This rap 1 protein might have functional relevance in the inhibition of agonist-induced inositide metabolism.
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PMID:Effect of protein kinase A on inositide metabolism and rap 1 G-protein in human erythroleukemia cells. 169 2

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.
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PMID:GTP-binding proteins mediate noradrenaline effects on calcium and chloride currents in rat portal vein myocytes. 170 Jan 11


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