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 investigated the role of phospholipase A2 (PLA2) and phospholipase C (PLC) in myocardial phosholipid degradation and cellular injury during reperfusion of ischemic myocardium. For this purpose, isolated rat hearts were perfused with isotopic arachidonic acid to label its membrane phospholipids. Hearts preperfused with antiphospholipase A2 (anti-PLA2) retained a significantly higher amount of radiolabel in phosphatidylcholine and phosphatidylinositol and a corresponding lower amount of radiolabel in lysophosphatidylcholine and nonesterified fatty acids (P less than 0.05) after 30 min of reperfusion following 30 min of normothermic global ischemia compared with hearts preperfused with nonimmune immunoglobulin G. In similar experiments, antiphospholipase C (anti-PLC)-treated hearts were associated with significantly (P less than 0.05) higher radiolabel in all phospholipids and lower radiolabel in diacyglycerol compared with nonimmune immunoglobulin G-treated hearts. Measurement of phospholipase activity in subcellular organelles of these hearts showed decreased PLA2 activity in cytosol, mitochondria, and microsomes of anti-PLA2-treated hearts and decreased PLC activity of microsomes in anti-PLC-treated hearts. Furthermore, both the antiphospholipases attenuated the release of creatine kinase and lactate dehydrogenase into perfusate and increased contractility as well as coronary flow in the reperfused hearts. Results of this study suggest that both PLA2 and PLC are involved in the degradation of phospholipids and cellular injury that occur during reperfusion of ischemic myocardium.
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PMID:Role of phospholipases A2 and C in myocardial ischemic reperfusion injury. 200 Sep 82

Parathyroid hormone (PTH), which increases cAMP levels, also induces an increase in the activity of the brain isozyme of creatine kinase and in DNA synthesis in osteoblast-enriched bone cell cultures by a cAMP-independent mechanism. The following results lead us to the conclusion that PTH induction of brain isozyme of creatine kinase activity and DNA synthesis occurs by activation of membranal phospholipid metabolism leading to increased protein kinase C activity and Ca2+ mobilization, a mechanism demonstrated for several growth factors and other hormones. (1) Binding of membranal phospholipids by agents such as gentamycin or antiphospholipid antibodies abolishes the stimulation by PTH of creatine kinase activity and DNA synthesis but not of cAMP production. (2) Treatment of cell cultures with exogenous phospholipase C increases brain isozyme of creatine kinase activity and DNA synthesis, but not cAMP production; these stimulations are also blocked by serum containing anti-phospholipid antibodies. PTH has no additional effect on stimulation of creatine kinase activity by phospholipase C (and only a slight effect on DNA synthesis). (3) A synthetic diacylglycerol (1-oleyl-2-acetyl glycerol) or phorbol ester (phorbol 12-myristate 13-acetate) or Ca2+ ionophore, A23187 induces creatine kinase activity and DNA synthesis in the cultures. However, this effect is not blocked by antiphospholipid sera and PTH has no additional effect. (4) Inhibition of protein kinase C activity by drugs reported to inhibit the enzyme (retinoic acid, quercetin) abolishes the stimulation of brain isozyme of creatine kinase activity and of DNA synthesis by PTH.
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PMID:Parathyroid hormone induction of creatine kinase activity and DNA synthesis is mimicked by phospholipase C, diacylglycerol and phorbol ester. 282 42

Qualitative and quantitative changes in neural cell adhesion molecule (N-CAM) protein and mRNA forms were measured during myogenesis in G8-1 and C2 cell lines. Indirect immunofluorescence assay showed that N-CAM was constitutively expressed by myoblasts in culture and that myotubes appeared to be stained more strongly. These changes were quantified using a dot blot assay. N-CAM levels increased almost 4-fold in G8-1 cells and 15-fold in C2 cells during myogenesis. The kinetics of accumulation of N-CAM were not coordinate with other muscle markers such as creatine kinase or acetylcholine receptor levels, since N-CAM accumulated significantly ahead of these markers. Immunoblotting showed that myogenesis was not associated with changes in the extent of sialylation of N-CAM. However, distinct changes in desialo forms were observed after neuraminidase treatment. Myogenesis was accompanied by increases in 125- and 155-kD desialo forms with minor changes in 120- and 145-kD forms. Biosynthetic labeling studies showed that myoblasts specifically expressed a transmembrane isoform of 145 kD that was phosphorylated and was down-regulated in myotubes. Pulse-chase analysis of myotubes showed that the 120-kD isoform and an isoform of 145 kD that co-migrated with, but was distinct from, the 145 kD transmembrane isoform of myoblasts were precursors of the 125- and 155-kD isoforms, respectively, that accumulated in myotubes. The 125- and 155-kD isoforms in myotubes are linked to the cell membrane via phosphatidylinositol linkage and can be released by phospholipase C. Indirect immunofluorescence analysis showed that phosphatidylinositol specific phospholipase C specifically released N-CAM from the myotube membrane generating N-CAM-free myotubes, while myoblasts were unaffected by this treatment. Three N-CAM mRNA species were observed in mouse muscle cell lines. Myoblasts were characterized by their expression of 6.7- and 5.2-kb transcripts while myotubes express 5.2- and 2.9-kb transcripts. Thus, myogenesis is qualitatively associated with a down regulation of the 6.7-kb transcript and an up regulation of the 5.2- and 2.9-kb transcript.
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PMID:Skeletal muscle neural cell adhesion molecule (N-CAM): changes in protein and mRNA species during myogenesis of muscle cell lines. 365 57

Cleavage of mitochondrial phosphatidylethanolamine (PE), phosphatidylcholine (PC) and cardiolipin (CL) by phospholipase A2 but not selective degradation of PE and PC by phospholipase C dissociates creatine kinase from rat heart mitochondria. Creatine kinase exhibits a high resistance against Triton X-100 solubilization up to concentrations of 0.05-0.1%. Scatchard plot of rebinding experiments using mitoplasts revealed the presence of both low and high affinity binding sites; the latter may account for the originally bound creatine kinase activity. It is suggested that creatine kinase is specifically bound to a CL containing domain of the inner mitochondrial membrane.
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PMID:Association of creatine kinase with rat heart mitochondria: high and low affinity binding sites and the involvement of phospholipids. 408 64

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

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

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

This study has shown that the maximal activation of the IP3-DAG regulatory circuit is observed on the 14th day of adaptation to repeated stresses. This activation is characterized by increased activity of phospholipase C and of the positive inotropic response of isolated heart to an alpha-agonist. Simultaneously, this activation is accompanied by the accumulation of five heat shock protein 70 (hsp70) isoforms. The IP3-DAG circuit activation and the hsp70 accumulation are accompanied by a significant increase in the cardiac resistance to post-ischemic reperfusion, as evidenced by a considerable decrease in the contracture, arrhythmias and the creatine kinase release into the perfusate. Continuation of the adaptation to repeated stresses for 28 days leads to complete reversal of the observed shifts.
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PMID:The role of hsp70 and IP3-DAG mechanism in the adaptive stabilization of structures and heart protection. 876 23

We investigated the early effects of the anti-idiotypic antibody (clone 1D5), which recognized the estrogen receptor (ER), on cytosolic free calcium concentration ([Ca2+]i) and its long term effects on creatine kinase (CK) specific activity in female human and rat osteoblasts. These actions were compared to the known membrane and genomic effects of 17 beta estradiol (E2). Like E2, clone 1D5 increased within 5 s [Ca2+]i in both cell types by two mechanisms: 1) Ca2+ influx through voltage-gated Ca2+ channels as shown by using EGTA a chelator of extracellular Ca2+, and nifedipine, a Ca2+ channel blocker; 2) Ca2+ mobilization from the endoplasmic reticulum as shown by using phospholipase C inhibitors, such as neomycin and U-73122, which involved a Pertussis toxin-sensitive G-protein. Clone 1D5 and E2 stimulated CK specific activity in human and rat osteoblasts with ten fold higher concentrations than those needed for the membrane effects (0.1 microgram/ml and 10 pM, respectively). Both effects were gender-specific since testosterone and 5 alpha-dihydotesterone were uneffective. Tamoxifen and Raloxifene, two estrogen nuclear antagonists, inhibited CK response to 1D5 and E2 and Ca2+ response to 1D5, but not Ca2+ response to E2. By contrast, (Fab')2 dimer, a proteolytic fragment of 1D5 with antagonist properties, inhibited both membrane and genomic effects of 1D5 and E2. In conclusion, these results imply that clone 1D5 has an estrogen like activity both at the membrane and nuclear levels in female human and rat osteoblasts. 1D5 must therefore interact with membrane binding sites, penetrate the cells, and reach the nuclear receptors by an as yet uncharacterized mechanism.
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PMID:Nongenomic effects of an anti-idiotypic antibody as an estrogen mimetic in female human and rat osteoblasts. 913 80

alpha-Toxin-permeabilized gastric glands represent a functional model in which acid secretion can be elicited by either adenosine 3',5'-cyclic monophosphate (cAMP) or ATP, with proven morphological and functional transition between resting and secretory states [X. Yao, S. M. Karam, M. Ramilo, Q. Rong, A. Thibodeau, and J. G. Forte. Am. J. Physiol. 271 (Cell Physiol. 40): C61-C73, 1996.] In this study we use alpha-toxin-permeabilized rabbit gastric glands to study energy metabolism and the interplay between nucleotides to support acid secretion, as indicated by the accumulation of aminopyrine (AP). When permeabilized glands were treated with a phosphodiesterase inhibitor, the secretory response to cAMP was inhibited, whereas the secretory response to ATP was potentiated. This implied that 1) ATP provided support not only as an energy source but also as substrate for adenylate cyclase, 2) activation of acid secretion by cAMP needed ATP, and 3) ATP and cAMP exchanged rapidly inside parietal cells. To address these issues, we tested the action of adenine nucleotides in the presence and absence of oxidizable substrates. All adenine nucleotides, including AMP, ADP, ATP, and cAMP, could individually enhance the glandular AP accumulation in the presence of substrates, whereas only a high concentration of ATP (5 mM) was able to support secretory activity in substrate-free buffer. Moreover, ATP could maintain 75-80% of maximal secretory activity in phosphate-free buffer; cAMP alone could not support secretion in phosphate-free buffer. In glands and in H(+)-K(+)-adenosinetriphosphatase-rich gastric microsomes, we showed the operation of adenylate kinase, creatine kinase, and ATP/ADP exchange activities. These enzymes, together with endogenous adenylate cyclase and phosphodiesterase, provide the recycling of nucleotides essential for the viability of alpha-toxin-permeabilized gastric glands and imply the importance of nucleotide recycling for energy metabolism in intact parietal cells.
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PMID:Nucleotide metabolism by gastric glands and H(+)-K(+)-ATPase-enriched membranes. 945 79


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