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 have studied four strains of Tetrahymena thermophila, each of which expresses a different allele of the SerH gene and produces a distinctive surface protein of the immobilization antigen (i-antigen) class. Following exposure of the strains to [3H]ethanolamine or [3H]myristic acid, a protein corresponding in molecular mass to the characteristic i-antigen for that strain became highly labeled, as determined by mobility in sodium dodecylsulfate-polyacrylamide electrophoresis gels. Furthermore, antibodies raised to the i-antigens of the T. thermophila strains selectively immunoprecipitated radioactive proteins having molecular mass identical to that of the i-antigen characteristic for that particular strain. The lipid moieties labeled by [3H]myristate were not susceptible to hydrolysis by exogenous phosphatidylinositol-specific phospholipase C from bacteria. However, when protein extraction was carried out in the absence of phospholipase C inhibitors, radioactive fatty acids derived from [3H]myristate were rapidly cleaved from the putative i-antigens. On the basis of available data, it was concluded that T. thermophila i-antigens contain covalently-linked glycosyl-phosphatidylinositol anchors.
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PMID:Immobilization antigens from Tetrahymena thermophila are glycosyl-phosphatidylinositol-linked proteins. 145 61

In the kidney, adenosine plays important regulatory roles, including renal blood flow, glomerular filtration rate, renin secretion, tubuloglomerular feedback, tubular reabsorption of sodium and water, sympathetic neurotransmitter release, and erythropoietin secretion. These functions are mediated through adenosine 1 (A1)-receptors and adenosine 2 (A2)-receptors. These receptors couple to the inhibition and stimulation of adenylate cyclase, through Gi and Gs proteins, respectively. A variety of other effecter systems have been reported to be coupled to A1 receptors, including phospholipase C, phospholipase A2 and potassium, as well as Ca++ channels. Recently, A1 receptors, A2 receptors and novel A2 receptor have been cloned, sequenced and expressed. In association with the development of selective adenosine analogues, we are now ready to take up problems at the biochemical and molecular biological levels.
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PMID:[Adenosine and adenosine receptors in the kidney]. 149 49

1. In canine antrum, rhythmic electrical activity consists of a rapid upstroke phase followed by a plateau depolarization. In response to slow waves, cytosolic Ca2+ ([Ca2+]cyt) and tension increased. 2. Addition of sodium nitroprusside (SNP, 0.5 microM) decreased the amplitude of the plateau phase of slow waves without significant effects on the upstroke depolarization. SNP also inhibited changes in [Ca2+]cyt and tension associated with the plateau potential. SNP induced a negative chronotropic effect at concentrations above 0.1 microM. 3. Similar to the effects of SNP, illumination of muscles during slow waves with ultraviolet (UV) light caused premature repolarization. UV illumination is known to release NO in some tissues. 4. L-NG-monomethyl-arginine (L-NMMA, 300 microM), Methylene Blue (MB, 5 microM) and oxyhaemoglobin (oxy-Hb, 5 microM) increased the force of contractions. In contrast, L-arginine (L-Arg, 300 microM) decreased contractile force and antagonized the effects of L-NMMA. 5. During the upstroke phase, SNP caused a small reduction in [Ca2+]cyt and a large reduction in force, suggesting that SNP caused a decrease in Ca2+ sensitivity. 6. In muscles permeabilized by alpha-toxin, cyclic GMP (100 microM) and UV illumination inhibited Ca(2+)-induced contraction (at pCa 5.5). 7. These data suggest that NO or NO-related compounds are spontaneously released in gastric muscles. These agents have two effects on excitation-contraction coupling: (i) inhibition (directly and/or indirectly) of the voltage-dependent Ca2+ channels that participate in the plateau phase of slow waves, and (ii) reduction in the Ca2+ sensitivity of the contractile element.
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PMID:Spontaneous release of nitric oxide inhibits electrical, Ca2+ and mechanical transients in canine gastric smooth muscle. 150 Nov 33

1. Independent of its effects on renal haemodynamics and glomerular filtration, angiotensin II (AII) has direct actions on the proximal tubule involving transepithelial Na+, H+, HCO3-, and water reabsorption, ammoniagenesis, gluconeogenesis and renal growth. 2. The effects of AII on water and electrolyte transport are biphasic and dose-dependent, such that low concentrations (10(-12)-10(-9) mol/L) stimulate reabsorption whereas high concentrations (10(-7)-10(-6) mol/L) inhibit reabsorption. Similar dose-response relations have been obtained for luminal and peritubular addition of AII. 3. The cellular responses to AII are mediated via an AT-1 receptor coupled via G-regulatory proteins to several parallel signal transduction pathways. Low doses inhibit the basolateral adenylate cyclase, lower intracellular cAMP and withdraw the inhibitory effect of protein kinase A on the luminal Na/H exchanger. Stimulation of this exchanger may also occur due to AII-receptor activation of phospholipase C to release diacyl glycerol, or by local transduction in the brush-border membrane involving phospholipase A2. 4. Inhibition of proximal fluid reabsorption is associated with increased intracellular Ca2+ released from intracellular stores, or entering via voltage-sensitive channels in response to the release of inositol-1,4,5-trisphosphate, or following Ca2+ channel opening induced by the arachidonic acid metabolite 5,6-epoxy-eicosatrienoic acid. 5. The stimulatory actions of peritubular AII on proximal transport are inhibited by physiological concentrations of atrial natriuretic factor (ANF) and by parathyroid hormone (PTH). 6. It is concluded that intrarenal AII acts to maintain optimal matching of fluid reabsorption and filtered load in response to changes in sodium balance, as well as to promote acidification of the urine during acidosis and perhaps to potentiate tubular growth following renal injury.
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PMID:Regulation of proximal tubule function by angiotensin. 151 68

The membrane-bound form of aminopeptidase P (aminoacylprolyl-peptide hydrolase) (EC 3.4.11.9) was purified to apparent homogeneity from bovine lung microsomes. The enzyme was solubilized using phosphatidylinositol-specific phospholipase C (Bacillus thuringiensis), indicating that bovine lung amino-peptidase P is attached to membranes via a glycosylphosphatidylinositol anchor. The enzyme was purified 1900-fold with a yield of 25% by chromatography on decyl-agarose, omega-aminodecyl-agarose, a second decylagarose column, DEAE-Sephacel, and an ultrafiltration step. Native gradient polyacrylamide gel electrophoresis revealed a single stained protein band whose position in the gel corresponded to cleavage of the Arg1-Pro2 bond of bradykinin. The Mr was 360,000 by gel permeation chromatography and 95,000 by reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The substrate specificity of aminopeptidase P was determined using approximately 50 peptides with proline in the second position. The enzyme could hydrolyze lower NH2-terminal homologs of bradykinin, including Arg-Pro-Pro, which was used as the routine substrate in a rapid fluorescence assay performed in the absence of added Mn2+. Some peptides having NH2-terminal amino acids other than arginine were also cleaved. Aminopeptidase P appeared to favor peptides that had 2 proline residues or proline analogs in positions 2 and 3 of the substrate. In general, tripeptides having a single proline residue in position 2 were poor substrates. Aminopeptidase P was inhibited by a series of peptides, 3-8 residues long, having an NH2-terminal Pro-Pro sequence. The enzyme was also inhibited by metal-chelating agents, 2-mercaptoethanol (4 mM), p-chloromercuribenzenesulfonic acid, and NaCl at concentrations greater than or equal to 0.25 M. The purified enzyme had a pH optimum of 6.5-7.0 and was most stable in the basic pH range. A role for membrane-bound aminopeptidase P in the pulmonary inactivation of circulating bradykinin is proposed.
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PMID:Membrane-bound aminopeptidase P from bovine lung. Its purification, properties, and degradation of bradykinin. 153 67

The effects of endothelin, a novel vasoconstrictive peptide, on the delayed rectifier K+ current (IK) were examined in single dialyzed cells from guinea pig ventricles. Either big endothelin or endothelin-1 enhanced IK at a dissociation constant of 2 nM with L-type Ca2+ current being unaffected. Under intracellular perfusion with pCa 7.6 solution, 3 nM big endothelin increased IK by 55 +/- 38.5%. Either pretreatment with 10 microM 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H 7) or a low Ca2+ [10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and minus CaCl2] internal solution diminished the enhancement. Preceding stimulation of protein kinase C (PKC) by 10-20 nM 12-O-tetradecanoylphorbol-13-acetate also reduced the degree of enhancement. When Na+ was eliminated from the solutions, endothelin increased IK distinctively in cells internally dialyzed with a low Ca2+ solution. This enhancement was not abolished by either pretreatment with H 7 or by removal of Ca2+ from the external perfusate but by increasing the internal EGTA concentration to 40 mM. Preincubation with ryanodine or internal perfusion with heparin also reduced the IK enhancement under Na(+)-free conditions. Intracellular application of 200 microM guanosine 5'-O-(3-thiotriphosphate) effectively attenuated the effect of endothelin. It is concluded that endothelin enhances IK via phospholipase C-mediated PKC activation and intracellular Ca2+ mobilization. GTP-binding protein is involved in these reactions.
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PMID:Endothelin enhances delayed potassium current via phospholipase C in guinea pig ventricular myocytes. 153 93

The present study specifically addresses the role of protein kinase C (PKC) activation in human endothelial cell Ca2+ mobilization, a response that is functionally coupled to the production of the potent arachidonate (AA) metabolite, prostacyclin (PGI2). Phorbol 12-myristate 13-acetate (PMA), alpha-thrombin, and sodium fluoride (NaF), a direct G-protein activator, produced a rapid and time-dependent translocation of PKC from the cytosol to the membrane. Activation of PKC by brief pretreatment of human umbilical vein endothelial cell (HUVEC) monolayers with PMA resulted in the inhibition of NaF-induced inositol phosphate increases and attenuation of both alpha-thrombin- and NaF-activated increases in intracellular Ca2+ (Ca2+i). Ca2+ mobilization induced by ionophore A23187 was not affected by PKC preactivation, suggesting PKC-dependent negative feedback inhibition of phosphatidylinositol (PI)-specific phospholipase C (PLC). Agonist-stimulated AA release and PGI2 synthesis in PMA-pretreated cultured human endothelial cells, however, was potentiated, and the enhanced PGI2 synthesis produced by A23187, NaF, and alpha-thrombin was dependent upon the dose of PMA. Treatment of HUVEC monolayers with an intracellular Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N'N'-tetraacetic acid-acetoxymethylester (BAPTA-AM), dramatically reduced alpha-thrombin-, NaF-, and A23187-induced PGI2 synthesis, demonstrating the importance of Ca2+i availability in PGI2 synthesis. BAPTA pretreatment did not inhibit PMA-induced PKC activation, and BAPTA-mediated inhibition of agonist-stimulated PGI2 synthesis was partially attenuated by prior PMA pretreatment. Staurosporine, a potent PKC inhibitor, at concentrations that inhibited PKC-induced phosphorylation of histone-1, augmented both alpha-thrombin- and NaF-induced production of inositol phosphates but markedly inhibited alpha-thrombin-, NaF-, and A23187-induced PGI2 synthesis. The downregulation of PKC activity by prolonged PMA treatment (18 h) produced similar inhibition of PGI2 synthesis by these agonists (approximately 50% inhibition). These studies indicate that the integrated phospholipase A2 and PLC activities are under complex regulation by factors that include both PKC activation and [Ca2+i]. PKC exerts dual effects on prostaglandin synthesis via negative regulation of Gp-coupled PI-specific PLC and positive feedback regulation of AA release and PGI2 synthesis. PKC is thus a critical determinant in the regulation of human endothelial cell prostaglandin synthesis by both receptor-mediated and G-protein-dependent cellular activation.
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PMID:Role of protein kinase C in the regulation of prostaglandin synthesis in human endothelium. 154 Mar 95

Clostridium septicum lethal (alpha-toxin) was purified and found to be a basic protein (pI 8.4) of approximately 48 kDa that is both lethal and hemolytic. The alpha-toxin had a hemolytic activity of approximately 2 x 10(7) hemolytic units per mg and a 50% lethal dose of approximately 10 micrograms/kg of body weight for mice. The alpha-toxin formed concentration-dependent, sodium dodecyl sulfate-resistant aggregates of approximately 230 kDa. Mice immunized with alpha-toxin showed a significant increase in survival time over mock-immunized mice when challenged with C. septicum. Rabbit polyclonal antibody was generated against the purified toxin and was used to confirm that toxin with the same molecular weight was present in seven different C. septicum isolates. No proteins in the supernatants from cultures of Clostridium perfringens, Clostridium histolyticum, Clostridium chauvoei, or Clostridium difficile were found to react with the C. septicum alpha-toxin-specific antibody.
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PMID:Purification and characterization of the lethal toxin (alpha-toxin) of Clostridium septicum. 154 52

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

Activation of phospholipase C (PLC) is considered to be one of the cellular signaling events involved in dopamine (DA)-mediated natriuresis. In the present study we have examined the role of renal cortical PLC in contributing to the increase in urinary sodium excretion during high sodium intake and its relationship with intrarenal DA synthesis. Rats were given either 1% NaCl (high sodium intake) or tap water (normal sodium intake) to drink for 24 h, and urine was collected over this time period. PLC activity in the renal cortex from these rats was measured by prelabeling cortical slices with myo-[2-3H]inositol and was expressed as fractional release (FR) of inositol (mono-, bis-, and tris-) phosphates. Acute increase in sodium intake produced 93 +/- 8% increase over control in urinary DA excretion. These changes were accompanied by significant increases (30 +/- 8%) in basal FR of inositol phosphates and 243 +/- 40 and 76 +/- 14% increases in urinary sodium and water excretion, respectively. The elevated basal PLC activity in rats with high sodium intake was significantly reduced in the presence of Sch 23390, a selective DA-1 receptor antagonist. Exogenously added DA (3 mM) also produced significant increases in PLC activity, although the magnitudes of increases were different in rats with high (37 +/- 8%) and normal (66 +/- 9%) sodium intake. However, Sch 23390 alone or carbidopa pretreatment did not affect the basal PLC activity in rats maintained on normal sodium intake.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Dopamine receptor-mediated activation of phospholipase C is associated with natriuresis during high salt intake. 155 66


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