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)

A major part of the present understanding of the molecular basis of signal transduction has been gained from in vitro studies using classical biochemical methods. In this study, we used 31P NMR spectroscopy to investigate the response of live M2R mouse melanoma cells to stimulation by melanocyte-stimulating hormone (MSH; melanotropin). In the presence of 3-isobutyl-1-methylxanthine and a synergistic dose of forskolin (1.67 microM), MSH induced a transient (approximately 60-min) rise in the cellular concentration of 3',5'-cyclic adenosine monophosphate (cAMP), which coincided in time with an equivalent decrease (approximately 40%) in ATP. However, no detectable change in phosphocreatine concentration was observed. Concomitantly, MSH induced a striking and unexpected increase in the concentration of three phosphomonoester (PME) metabolites (approximately 2-fold increase in total PME signal area); one signal has been assigned to phosphoethanolamine. The levels of the PMEs remained high for 2-4 hr and declined slowly (approximately 10 hr) to basal level, following perfusion with fresh culture medium. The increase in PME was also observed after stimulation with MSH alone. In contrast, stimulation with a high dose of forskolin (50 microM) and isobutylmethylxanthine (0.2 mM), although effective in stimulating the production of cAMP, did not induce the PME response. Evaluation of the cells' energetics indicated that the enhanced production of phosphoethanolamine is probably not due to ethanolamine phosphorylation. Therefore, it is likely to result from hydrolysis of phosphatidylethanolamine by a specific phospholipase C. The response of the PMEs appears to be regulated by a cAMP-independent process, suggesting the existence of an alternative transduction pathway controlled by MSH.
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PMID:Stimulation of cAMP and phosphomonoester production by melanotropin in melanoma cells: 31P NMR studies. 170 40

Necessity of newly synthesized ATP by creatine kinase for synthesis of ATP as an energy source for smooth muscle contraction was studied in permeabilized longitudinal muscle preparations of rat proximal colon. In alpha-toxin-permeabilized preparations, Ca++ induced "phasic type" contraction in a normal bath solution containing 4 mM ATP and 5 mM phosphocreatine. Omission of phosphocreatine from the solution resulted in significant decrease in phasic contraction, and omission of ATP resulted in loss of the response to Ca++. When ADP, but not adenosine-5-O-(2-thiodiphosphate), with phosphocreatine was added as a substitute for ATP, Ca++ induced the same type of contraction as with ATP. The maximum tensions of the phasic and tonic phases of the contraction with ADP were approximately 60% of, and almost the same, respectively as those with ATP. A selective inhibitor of creatine kinase, 2,4-dinitrofluorobenzene, inhibited the phasic contraction induced by Ca++. After irreversible inhibition of endogenous creatine kinase by DNFB in beta-escin-permeabilized preparations, treatment of the preparations with exogenous creatine kinase restored Ca(++)-induced contraction. These findings suggest that ATP synthesized from ADP and phosphocreatine by creatine kinase was necessary for phasic contraction of permeabilized smooth muscle and that exogenous ATP was mainly used after its hydrolysis to ADP.
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PMID:Necessity of newly synthesized ATP by creatine kinase for contraction of permeabilized longitudinal muscle preparations of rat proximal colon. 756 81

Ghosts prepared from rat basophilic leukemia cells (RBL cell ghosts) and permeabilized with alpha-toxin from S. aureus are a simplified system for the study of Fc epsilon RI-mediated activation of phospholipase C (PLC). This activity is dependent upon ATP and magnesium, and is enhanced by the addition of another compound containing an energetic phosphate group, either phosphoenolpyruvate (PEP) or phosphocreatine (PCr). This effect appears to be specific for PEP and PCr in that other compounds with energetic phosphate bonds including fructose 1,6-bisphosphate and additional ATP are not effective. On the contrary, GTP-gamma-S, an activator of G proteins, activates PLC in the presence of ATP alone and this is not further enhanced by the addition of PEP. In addition to Fc epsilon RI and GTP-gamma-S, two other stimuli lead to enhanced activity of PLC in permeabilized RBL cell ghosts: 1) an inhibitor of tyrosine phosphatases (Na3VO4) and 2) an analog of adenosine (NECA). Data presented here extend previous results to show that activation of PLC by GTP-gamma-S is not enhanced either by the addition of PCr or by the addition of a more MgATP. Further new findings include the observations that activation of PLC by Na3VO4 is augmented by PEP and PCr in a fashion similar to that observed for Fc epsilon RI-mediated activation of PLC and that activation of PLC by NECA shows even more marked dependency on PEP than does activation by Fc epsilon RI or Na3VO4.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:ATP-dependent activation of phospholipase C by antigen, NECA, Na3VO4, and GTP-gamma-S in permeabilized RBL cell ghosts: differential augmentation by ATP, phosphoenolpyruvate and phosphocreatine. 756 46

Rabbit portal veins were permeabilized using Staphylococcus aureus alpha-toxin, and adenosinetriphosphatase (ATPase) was measured as the formation of [3H]ADP, [3H]AMP, and [3H]adenosine from [3H]ATP in the solution bathing the muscle. The resting ATPase (1.96 +/- 0.15 mM/min, n = 13) is approximately 5-10 times higher than that measured in Triton X-100-permeabilized muscles (0.28 +/- 0.01 mM/min, n = 4), with nucleotide accumulating as ADP, AMP, and adenosine. The ATPase activity is also seen when the intact muscle is incubated in a Krebs solution containing 1 mM MgATP (2.76 +/- 0.10 mM/min, n = 73). This suggests that it is due primarily to an ecto-ATPase. The ectoenzyme is capable of hydrolyzing both ATP and ADP, and in both cases there is a higher rate at 3 than at 1 mM nucleotide. The high resting ATPase compromises the control of nucleotide concentrations within the permeabilized tissue even in the presence of an ATP-regenerating system consisting of phosphocreatine (PCr, 35mM) and creatine kinase (1 mg/ml). Treatment of the intact muscle with the ectonucleotidase inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) followed by alpha-toxin permeabilization and inclusion of sodium azide in subsequent solutions reduces the ecto-ATPase by approximately 70%. Addition of PCr and creatine kinase then results in the maintenance of high [ATP] and low [ADP] in the muscle, and importantly, there are no significant changes in [ATP], [ADP], [adenosine/AMP], or the ADP-to-ATP ratio upon activation of the muscle in pCa 4.5. In general, the force output in high Ca2+ increased as the metabolic profile of the muscle improved. When ATPase was measured as the appearance of [32P]Pi from [32P]PCr and [gamma-32P]ATP, the alpha-toxin-permeabilized muscle subjected to the above treatment showed only approximately 30% higher total ATPase under activated conditions compared with the freeze-glycerinated Triton-treated portal vein. The suprabasal ATPase is similar in both preparations. We conclude that the reduction of the basal ATPase by the DIDS-azide treatment permits both rigorous control of nucleotide contents and accurate measurement of ATPase activity in alpha-toxin-permeabilized smooth muscle.
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PMID:Metabolic characteristics of alpha-toxin-permeabilized smooth muscle. 802 97

The objective of the present experiments was to correlate changes in cellular energy metabolism, dissipative ion fluxes, and lipolysis during the first 90 s of ischemia and, hence, to establish whether phospholipase A2 or phospholipase C is responsible for the early accumulation of phospholipid hydrolysis products. Ischemia was induced for 15-90 s in rats, extracellular K+ (K+e) was recorded, and neocortex was frozen in situ for measurements of labile tissue metabolites, free fatty acids, and diacylglycerides. Ischemia of 15- and 30-s duration gave rise to a decrease in phosphocreatine concentration and a decline in the ATP/free ADP ratio. Although these changes were accompanied by an activation of K+ conductances, there were no changes in free fatty acids until after 60 s, when free arachidonic acid accumulated. An increase in other free fatty acids and in total diacylglceride content did not occur until after anoxic depolarization. The results demonstrate that the early functional changes, such as activation of K+ conductances, are unrelated to changes in lipids or lipid mediators. They furthermore suggest that the initial lipolysis occurs via both phospholipase A2 and phospholipase C, which are activated when membrane depolarization leads to influx of calcium into cells.
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PMID:Coupling among energy failure, loss of ion homeostasis, and phospholipase A2 and C activation during ischemia. 822 87

Cathepsin G, an enzyme released by stimulated polymorphonuclear neutrophils, and thrombin are two human proteinases which potently trigger platelet activation. Unlike thrombin, the mechanisms by which cathepsin G initiates platelet activation have yet to be elucidated. The involvement of the phospholipase C (PLC)/protein kinase C (PKC) pathway in cathepsin G-induced activation was investigated and compared with stimulation by thrombin. Exposure of 5-[14C]hydroxytryptamine-labelled platelets to cathepsin G, in the presence of acetylsalicylic acid and phosphocreatine/creatine kinase, induced platelet aggregation and degranulation in a concentration-dependent manner (0.1-3.0 microM). Time-course studies (0-180 s) comparing equivalent concentrations of cathepsin G (3 microM) and thrombin (0.5 unit/ml) resulted in very similar transient hydrolysis of phosphatidylinositol 4,5-bisphosphate and steady accumulation of phosphatidic acid. In addition cathepsin G, like thrombin, initiated the production of inositol phosphates. The neutrophil-derived proteinase also induced phosphorylation of both the myosin light chain and pleckstrin, a substrate for PKC, to levels similar to those observed in platelets challenged with thrombin. Inhibition of PKC by GF 109203X, a specific inhibitor, suppressed platelet aggregation and degranulation to the same extent for both proteinases. Using fura 2-loaded platelets, the rise in the cytosolic free Ca2+ concentration induced by cathepsin G was shown to result, as for thrombin, from both mobilization of internal stores and Ca2+ entry across the plasma membrane. These findings provide evidence that cathepsin G stimulates the PLC/PKC pathway as potently as does thrombin, independently of thromboxane A2 formation and ADP release, and that this pathway is required for platelet functional responses.
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PMID:The phospholipase C/protein kinase C pathway is involved in cathepsin G-induced human platelet activation: comparison with thrombin. 857 71

The role of newly synthesized ATP in cyclic GMP-induced relaxation was studied in membrane permeabilized longitudinal muscle preparations of the rat proximal colon. Cyclic GMP and 8 bromo cGMP induced concentration-dependent relaxation of alpha-toxin permeabilized preparations which were precontracted by 3 microM Ca2+ in the presence of 4 mM ATP and 5 mM phosphocreatine (PC). The relaxation by 8 bromo cGMP was inhibited by Rp-8-pCPT cGMPS, an inhibitor of cyclic GMP dependent protein kinase. The relaxation was inhibited by removal of PC from the bathing solution, in spite of the presence of ATP. The relaxation was also inhibited by dinitrofluorobenzene (DNFB), a selective inhibitor of creatine kinase. The removal of PC or treatment with DNFB is known to produce accumulation of ADP within smooth muscle cell, however, ADPbetaS did not affect the relaxation. After irreversible inhibition of endogenous creatine kinase by DNFB in beta-escin permeabilized preparations, treatment of the preparations with exogenous creatine kinase restored the relaxation. In the presence of ADP and PC but without ATP, 8-bromo cGMP induced the relaxation to the similar extent to that in the presence of ATP and PC. These results suggest that ATP newly synthesized from ADP and PC by creatine kinase is essential for cyclic GMP-induced relaxation of the smooth muscle preparations obtained from the proximal colon of rats.
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PMID:Essential role of newly synthesized ATP for cyclic GMP-induced relaxation in alpha-toxin permeabilized smooth muscle of rat proximal colon. 963 20

Since it was suggested in our previous study that ATP newly synthesized from ADP and phosphocreatine (PCr) by creatine kinase had an important role in Ca2+-induced phasic contraction in alpha-toxin permeabilized smooth muscle of rat proximal colon, we studied the role of newly synthesized ATP on myosin ATPase activity, by assessing a rate of force development as an index of myosin ATPase activity. The alpha-toxin-permeabilized preparations were thiophosphorylated by treatment with ATPgammaS. After the thiophosphorylation, the contraction induced by ATP plus PCr in the absence of Ca2+ reached the maximum at 30 s. When PCr was omitted from the bathing solution, the initial rate of the contraction was significantly slower, while the level of myosin light chain thiophosphorylation remained unchanged. An inhibitor of creatine kinase slowed the initial contractile rate to a rate similar to that induced by ATP alone. ADPbetaS had no effect on ATP plus PCr-induced contraction, suggesting that accumulation of ADP does not affect the initial rate of the contraction. PCr alone did not contract the thiophosphorylated-preparations. However, in the presence of ADP, PCr induced contraction at the initial rate which was slower than that induced by ATP plus PCr. These results indicate that newly synthesized ATP together with preexisting ATP is utilized as a substrate for myosin ATPase.
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PMID:The site where newly synthesized ATP is necessary for tension development in alpha-toxin permeabilized preparations of rat proximal colon. 1271 56

In order to prescribe lithium appropriately to patients with bipolar disorder, predictors of lithium response are helpful. The present paper reviews the biological predictors of lithium response. As a positive predictor of lithium response, the following have been reported: strong loudness dependence of the auditory-evoked N1/P2-response; higher brain lithium concentration; lower inositol monophosphatase (IMPase) mRNA expression; higher serotonin-induced calcium mobilization; increased N-acetyl-aspartate peak and decreased myo-inositol peak; white matter hyperintensity; decreased intracellular pH; higher frequency of phospholipase C gamma-1 (PLCG1)-5 repeat and PLCG1-8 repeat; and C973A polymorphism in the inositol polyphosphate 1-phosphatase gene. In contrast the following have been reported as a predictor of negative lithium response: epileptiform abnormality of electroencephalography; human leukocyte antigen type A3; decreased phosphocreatine peak area after photic stimulation; and homozygotes for the short variant of the serotonin transporter gene. Most of the possible biological predictors of better lithium response, such as lower IMPase mRNA levels, white matter hyperintensity, lower brain intracellular pH, enhanced calcium response, and PLCG1-5 repeat had been detected as risk factors for bipolar disorder, suggesting that bipolar disorder responding well to maintenance lithium treatment is a distinct category having a certain neurobiological basis, although these findings need further replication. The search for biological predictors of lithium response is still in its infancy. Most of the laboratory or neuroimaging techniques used in these studies are not easily performed in clinical settings, so the development of an easy and useful laboratory test is needed.
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PMID:Biological predictors of lithium response in bipolar disorder. 1275 62

The role of ATP newly synthesized from ADP and phosphocreatine (PC) by creatine kinase (CK) in the contraction of tonic type smooth muscle, rat femoral artery was studied, since its necessity for phasic type smooth muscle was previously shown. In alpha-toxin-permeabilized preparations obtained from rat femoral artery, Ca(2+) induced a tonic type contraction in the presence of ATP and PC. Omission of PC inhibited significantly the contraction. Treatment of the preparations with 2,4-dinitrofluorobenzene, an inhibitor of CK, also inhibited the contraction. In the presence of ADP and PC, Ca(2+) also induced the contraction to a level comparable to that in the presence of ATP and PC. The extent of phosphorylated myosin light chain was fairly consistent with that of Ca(2+)-induced contraction under all experimental conditions planned above. These results suggest that ATP newly synthesized by CK essentially participates in the whole of the contraction in tonic type smooth muscle, although it participates only in a rapid phasic contraction in phasic type muscle as previously shown.
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PMID:Essential role of ATP synthesized by creatine kinase in contraction of alpha-toxin permeabilized preparations of tonic type smooth muscle. 1293 22


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