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At least 523 records · Page 29Linked to original sources
PubMed1986

Carbachol induces a rapid and sustained hydrolysis of polyphosphoinositide in bovine tracheal smooth muscle measurements of the mass of polyphosphoinositides, 1,2-diacylglycerol, and phosphatidic acid.

The effects of carbachol on polyphosphoinositides and 1,2-diacylglycerol metabolism were investigated in bovine tracheal smooth muscle by measuring both lipid mass and the turnover of [3H]inositol-labeled phosphoinositides. Carbachol induces a rapid reduction in the mass of phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate and a rapid increase in the mass of 1,2-diacylglycerol and phosphatidic acid. These changes in lipid mass are sustained for at least 60 min. The level of phosphatidylinositol shows a delayed and progressive decrease during a 60-min period of carbachol stimulation. The addition of atropine reverses these responses completely. Carbachol stimulates a rapid loss in [3H]inositol radioactivity from phosphatidylinositol 4,5-bisphosphate and phosphatidylinositol 4-monophosphate associated with production of [3H]inositol trisphosphate. The carbachol-induced change in the mass of phosphoinositides and phosphatidic acid is not affected by removal of extracellular Ca2+ and does not appear to be secondary to an increase in intracellular Ca2+. These results indicate that carbachol causes phospholipase C-mediated polyphosphoinositide breakdown, resulting in the production of inositol trisphosphate and a sustained increase in the actual content of 1,2-diacylglycerol. These results strongly suggest that carbachol-induced contraction is mediated by the hydrolysis of polyphosphoinositides with the resulting generation of two messengers: inositol 1,4,5-trisphosphate and 1,2-diacylglycerol.

Animals↗
PubMed1986

Cholinergic stimulation of arachidonic acid and phosphatidic acid metabolism in C62B glioma cells.

Glioma C62B cells were incubated for 18 h with [1-14C]arachidonic acid. Most (80%) of the added [1-14C] arachidonic acid was taken into the intracellular pool; less than 1% of the intracellular [1-14C]arachidonic acid remained unesterified; the rest was present in glycerophospholipids. Acetylcholine stimulation of the prelabeled cells resulted in the rapid accumulation of free [1-14C]arachidonic acid, presumably liberated by hydrolysis from phospholipids. Labeled unesterified [1-14C]arachidonic acid peaked by 90 s and returned to basal levels by 5 min. Paralleling the transient increase of unesterified [1-14C]arachidonic acid were increases in level of radioactivity in an unidentified lipoxygenase metabolite of arachidonic acid and of radioactive phosphatidic acid. The release of arachidonic acid induced by acetylcholine or carbachol was blocked by muscarinic but not nicotinic receptor antagonists; adrenergic or histaminergic receptor agonists were ineffective at stimulating arachidonic acid liberation. In contrast to the transient effects of stimulation with cholinergic agonists, stimulation with the divalent cation ionophore A23187 resulted in a linear increase in the accumulation of liberated arachidonic acid for at least 1 h. Furthermore, the pattern of metabolites synthesized from arachidonic acid in response to ionophore stimulation was more complex than that observed following cholinergic stimulation and included also several metabolites derived from cyclooxygenase activity. We conclude that muscarinic receptor agonists rapidly induce specific changes in arachidonic acid and phosphatidic acid metabolism in a glioma cell line and suggest that similar responses may occur in glial cells and play a physiologically significant role in neural metabolism.

Acetylcholine↗
PubMed1985

[Binding and entrapment of insulin by lecithin-phosphatidic acid liposomes in acid solutions].

Microvesicles made of mixtures of lecithin and phosphatidic acid were precipitated by insulin in acid solution. Insulin was bound by the precipitates up to saturation, that was governed by the portion of phosphatidic acid in the liposomal matrix. The amount of bound insulin was described by a binding isotherm for a bivalent ligand. In neutral solutions the precipitates were repeptised thereby releasing bound insulin. An increase of the particle size, observed by gel filtration analysis, was explained by liposome fusion. If the liposomes were generated in acid solutions of insulin by sonication, up to 50% of the insulin remained entrapped even in the neutralized solution. Especially with cholesterol as a lipid component the entrapped insulin was highly protected from the proteolytic attack by pronase.

Chemistry, Pharmaceutical↗
PubMed1984

Regulatory role of phosphatidate phosphatase in triacylglycerol synthesis of Saccharomyces cerevisiae.

The regulatory mechanism of triacylglycerol synthesis in Saccharomyces cerevisiae was studied. The triacylglycerol content increased markedly during the entry of cells into the stationary growth phase, whereas the content of phospholipids remained unchanged. Pulse-labeling experiments to measure [14C]acetate incorporation into triacylglycerol revealed that the synthesis of triacylglycerol increased in the stationary growth phase. An increase in fatty acid synthesis was observed only in the later stage of the stationary growth phase and thus does not seem to be the principal causative factor for the triacylglycerol accumulation. Among various triacylglycerol-synthetic enzymes tested, the increase in the phosphatidate phosphatase (EC 3.1.3.4) activity was most closely correlated with the accumulation of triacylglycerol in the stationary phase. Our results show that phosphatidate phosphatase plays an important role in the regulation of triacylglycerol synthesis in S. cerevisiae.

Acetates↗
PubMed1982

Insulin acutely increases phospholipids in the phosphatidate-inositide cycle in rat adipose tissue.

Administration of insulin in vivo provoked rapid (near maximal in 30 min) increases (65-90%) in the concentrations of phosphatidic acid, phosphatidylinositol, and polyphosphoinositides in rat adipose tissue. Insulin also increased phosphatidylinositol levels in adipocytes incubated in vitro. Dose-response relationships suggested that these effects of insulin were physiologically relevant. The enrichment of membranes with acidic phospholipids in the phosphatidate-inositide cycle may play a role in the action of insulin in adipocytes.

Adipose Tissue↗
PubMed1981

Phytomitogen-induced stimulation of syntheses de novo of phosphatidylinositol, phosphatidic acid and diacylglycerol in rat and human lymphocytes.

The biosynthetic route of phosphatidylinositol in lymphocytes stimulated with either concanavalin A or Phaseolus vulgaris hemagglutinin is examined by the determination of the [2-3H]glycerol and 32PO4 incorporations into glycerolipids of rat and human lymphocytes. In rat lymph-node cells, the [2-3H]glycerol incorporation into phosphatidylinositol was accelerated 23-fold by 50 microgram concanavalin A/ml culture; the same cells exhibited a 37-fold concanavalin A-induced stimulation in 32PO4 incorporation into the phospholipid. Moreover, concanavalin A markedly stimulated [2-3H]glycerol incorporation into phosphatidic acid and diacylglycerol. [2-3H]Glycerol incorporation into the other glycerolipids was affected to a very small degree by concanavalin A. In human peripheral blood lymphocytes, concanavalin A and P. vulgaris hemagglutinin enhanced the rate of the [2-3H]glycerol incorporation into phosphatidylinositol to almost the same degree (4--8-fold) as the rate of the 32PO4 incorporation into the phospholipid. The [2-3H]glycerol incorporation into phosphatidic acid and phosphatidylserine was markedly stimulated after addition of these lectins; the enhancement was 3--4-times higher than the enhancement found in the 32PO4 incorporation into these lipids. The [2-3H]glycerol incorporation into diacylglycerol was enhanced 4--5-fold by these lectins. These mitogenic lectins stimulated the [2-3H]glycerol and 32PO4 incorporation into phosphatidylcholine and phosphatidylethanolamine to a smaller degree. Our results indicate that phosphatidylinositol in phytomitogen-stimulated lymphocytes is synthesized mainly via the de novo pathway, in contrast to the previously postulated pathway involving turnover of the inositol and phosphate moieties of phosphatidylinositol while conserving the diacylglycerol portion of this molecule.

Animals↗
PubMed1993

Suppressive effect of T cell proliferation via the CD29 molecule. The CD29 mAb 1 "K20" decreases diacylglycerol and phosphatidic acid levels in activated T cells.

We had previously reported that the CD29 mAb "K20," presented in a soluble form, blocks peripheral T cell proliferation/activation induced by a CD3 mAb. To better characterize the negative signal delivered by soluble K20, we have investigated its effects on the phospholipid metabolism, both in Jurkat and CD4+ T cells. In CD3-activated T cells, K20 inhibited the increase of diacylglycerol (DAG) and phosphatidic acid levels, but did not modify phosphatidylinositol 4,5-bisphosphate levels, cytosolic Ca2+ raise, and inositolphosphates formation, indicating that K20 did not inhibit phosphatidylinositol 4,5-bisphosphate hydrolysis by phospholipase C-gamma. Moreover, in these conditions, K20 increased phosphatidylethanolamine levels, without variation of phosphatidylcholine, phosphatidylserine, and phosphatidylinositol, suggesting that K20 specifically increased the phosphatidylethanolamine biosynthesis from DAG. Thus, the effects of K20 on DAG and phosphatidic acid levels resulted from an accelerated catabolism rather than from a defect of synthesis. That K20 acts solely at an early step of T cell activation, namely before the binding of IL-2 to its receptor, is supported by the observation that adding exogenous rIL-2 increased proliferation in spite of K20. These results suggest that the beta 1 integrin molecules interact with the membrane phospholipid metabolism and they appear to be the hallmark of a peculiar negative pathway of T cell activation, likely to play an important regulatory role mediated via the T cell integrin molecules.

Antigens, CD↗
PubMedDate not supplied

[The plasticity of the snail cholinoreceptor neurons following exposures to the inositol 1,4,5-triphosphate- and Ca2(+)-dependent mobilization of deposited Ca2(+) and the level of phosphatidic acid].

Effects of some substances (which influence on mobilization of deported Ca2+ and intracellular level of second messengers) on identified neurons RPa3 and LPa3 of Helix lucorum were studied using two-electrode voltage clamp technique. The action of inositol-1,4,5-trisphosphate (IP3), inositolhexakisphosphate (IP6), TMB-8 inhibitor of IP3-dependent Ca2+ mobilization), tetracaine (inhibitor of Ca(2+)-dependent mobilization of Ca2+), and phospholipase D (which catalyzes phosphatidic acid formation from membrane phosphatidylcholine) was studied. Participation of IP3, IP3-dependent-, Ca(2+)-dependent mobilized intracellular Ca2+ and phosphatidic acid in regulation of cholinoreceptor plasticity was shown in Helix neurons.

Animals↗
PubMed1994

Regulation of phosphatidic acid biosynthetic enzymes in Saccharomyces cerevisiae.

Phosphatidic acid is the biosynthetic precursor of all glycerolipids. To understand how phosphatidic acid biosynthesis is controlled in Saccharomyces cerevisiae, we studied the regulation of three enzyme activities involved in the synthesis of this glycerolipid precursor, i.e., glycerophosphate acyltransferase (GPAT), dihydroxyacetone phosphate acyltransferase (DHAPAT), and acyl DHAP reductase. GPAT activity was increased 3-fold, while DHAPAT activity was increased up to 9-fold in wild type cells grown in a nonfermentable carbon source compared to that of glucose-grown cells. The ratio of GPAT/DHAPAT activity was 12 in glucose-grown cells but only 4 in cells grown in glycerol/ethanol. In the previously characterized tpa1 mutant, (T. S. Tillman and R. M. Bell. 1986. J. Biol. Chem. 261: 9144-9149), GPAT was decreased 2-fold and DHAPAT 27-fold compared to activities in the wild type. Acyl DHAP reductase activity in both wild type and tpa1 cells grown on a nonfermentable carbon source was increased approximately 2-fold over that of glucose-grown cells. All three enzymatic activities increased as wild type cells grown on glucose entered the stationary phase of growth. Therefore, GPAT, DHAPAT, and acyl DHAP reductase activities appear to be regulated by the respiratory state of the cell. None of the activities was affected to a great extent by inositol, which is a key regulator of many enzymes involved in the synthesis of PtdOH-derived phospholipids in S. cerevisiae, nor by deletion of the mitochondrial genome.(ABSTRACT TRUNCATED AT 250 WORDS)

Acyltransferases↗
PubMed1994

Purification, characterization, and inhibition by phosphatidic acid of lysophospholipase transacylase from rat liver.

Lysophospholipase transacylase was purified 214,360-fold to homogeneity from the rat liver 100,000 x g supernatant. After DEAE chromatography, total activity increased 12.9-fold, due to the removal of endogenous inhibitors. The inhibitors were isolated and identified as phosphatidic acid and fatty acid. The final preparation showed a single band on SDS-polyacrylamide electrophoresis with an M(r) of 60,000. Gel filtration through Sephacryl S-200 gave a similar value, suggesting that the enzyme exists as a monomer. Activity was highest at pH 6.0 and was not affected by Ca2+, Mg2+, and EDTA. The enzyme produced glycerophosphocholine (GPC), palmitic acid, and dipalmitoyl-GPC on incubation with 1-palmitoyl-GPC, indicating that the enzyme catalyzed both deacylation and transacylation. The relative rates of deacylation and transacylation were 1:0.3 under standard assay conditions. Km for 1-palmitoyl-GPC and Vmax of hydrolase activity were 91 microM and 12.9 mumol/min/mg, respectively. The enzyme was selective for choline lysophospholipid. Ethanolamine, inositol, and serine lysophospholipids were not good substrates of the enzyme. Phosphatidic acid was a potent, competitive inhibitor of the enzyme with Ki of about 10 microM as determined with 1-stearoyl-2-arachidonoyl glycerophosphate. Although less potent, lysophosphatidic acid, palmitoyl-L-carnitine, and fatty acid were also inhibitory to the enzyme.

Acyltransferases↗
PubMed1994

Type I phosphatidylinositol 4-phosphate 5-kinase isoforms are specifically stimulated by phosphatidic acid.

A phosphatidylinositol 4-phosphate (PIP) kinase was isolated and purified to near homogeneity from bovine erythrocyte membranes. The PIP kinase was extracted from bovine erythrocyte membranes with a high salt wash, followed by phosphocellulose and phenyl-Sepharose chromatography. The predominant protein after phenyl-Sepharose purification had a molecular size of 68 kDa. Renaturation of PIP kinase activity after SDS-PAGE showed that a 68-kDa protein was able to phosphorylate PIP. An antibody developed against the 68-kDa protein Western blots the 68-kDa protein and is able to immunoprecipitate the 68-kDa protein and PIP kinase activity from membrane extracts. Based on functional studies, the 68-kDa protein is indistinguishable from the type I PIP kinase previously characterized from human erythrocyte membranes (Bazenet, C. E., Ruano, A.R., Brockman, J.L., and Anderson, R.A. (1990) J. Biol. Chem. 265, 18012-18022). These studies also show that the type I PIP kinases, but not the type II PIP kinase, are stimulated by phosphatidic acid, suggesting alternative roles for these enzymes. Two immunoreactive isoforms of the type I PIP kinase, of 68 and 90 kDa, were identified in rat brain and partially purified. Both of these isoforms are also stimulated by phosphatidic acid.

Animals↗
PubMed1977

Analogs of natural lipids. IV. Synthesis and properties of cyclopentanoid analogs of phosphatidic acid.

A new series of phosphatidic acid analogs has been synthesized in which the glycerol moiety of diacylglycerophosphoric acid is replaced by each of the three isomeric cyclopentane-1,2,3-triols (1,3/2, DL-1,2/3, and 1,2,3/0). Of the seven possible configurational and positional phosphatidic acid analogs of this series, five isomers have been obtained and characterized by spectroscopic methods and microanalysis. Four of the five isomers are 1-(or 3-)phosphoryl derivatives, while the fifth is a 2-phosphate. The analogs were prepared in configurationally pure form by unequivocal synthetic procedures involving selectively blocked intermediates: acyl migration was avoided by the use of mild deblocking procedures. The anhydrous lipid products, all of which are dipalmitoyl esters, are solids indefinitely stable at room temperature in the free acid or potassium salt form; they have chromographic mobility and melting points similar to dipalmitoyl glycerophosphoric acid the dipotassium salts bind water of hydration tenaciously, remaining hydrated after drying in vacuo at 100 degrees C. NMR spectra of dimethyl esters of some of the analogs show nonequivalence of the two methyl groups, consistent with the diastereotopic nature of those groups. In addition to their intrinsic interest as conformationally restricted acidic lipids, the analogs are now available as starting materials for the synthesis of the more complex acidic and amphoteric lipids required for our exploitation of these cyclopentanoid analogs as unique probes for the study of lipid-lipid and protein-lipid interactions.

Chemical Phenomena↗
PubMed2001

Monolayer Characteristics of Bacteriocin AS-48, pH Effect and Interactions with Dipalmitoyl Phosphatidic Acid at the Air-Water Interface.

Bacteriocin AS-48 produced by Enterococcus faecalis S-48 is a ribosomally synthesized cyclic peptide (7.4 kDa) of broad inhibitory spectrum against Gram-positive and Gram-negative bacteria. Simple monolayers of AS-48 and of dipalmitoyl phosphatidic acid (DPPA) at the air-water interface are studied. The AS-48 interfacial behavior in the function of pH explains the biological activity of the peptide. The lipid monolayers show the characteristic behavior of phosphatidic acid at the mentioned interface. The interactions between AS-48 and DPPA, a majority lipid of the bacterial cell membrane, are quantitatively investigated. The results indicate that only when the lipid molecules are charged enough (pH 10.5) is an attractive interaction between AS-48 and DPPA observed, although under these experimental conditions the results seem to indicate that a deformation of the peptide helical structure could take place. Copyright 2001 Academic Press.

Journal Article↗
PubMed1976

[Changes of the phosphatides and their fatty acids in the retina and in the fasciculus opticus after retinal detachment: investigations of human and animal retinae (author's transl)].

In this study the effect of an experimentally provoked retinal detachment on the pattern of the phosphatides and fatty acids of the retina and the optic nerve of adult rabbits was investigated. The analysis was performed one month, and 4 months after the operation, and the values were related to the findings in control animals of the same age, and of the age of one day and 30 days respectively. In this way changes in the total lipide, in the phosphatides and in their fatty acids could be revealed, with a tendency towards the developmental stage of the 20th up to the 30th day of life. Between retina and optic nerve no difference was found neither temporally nor regarding the quantitative reaction. In the detached human retinae the same reactions can be proved as in the animal experiment. The relationship of these findings to the recovery of the operatively reatached human retina is discussed.

Adult↗
PubMed1982

Investigations of the lipid metabolism of the white matter in multiple sclerosis: changes in glycero-phosphatides and lipid-splitting enzymes.

Phospho- and galacto- lipids and lipidhydrolyzing enzymes have been determined in the white matter of a young patient with a subacute course of multiple sclerosis (MS). Significant changes were observed for the concentration of glycerophosphatides and the fatty acid pattern of the normal appearing with matter surrounding MS-plaques. Among the individual glycerophosphatides a significant decrease of phosphatidylserine and phosphatidylinositol was found, whereas the ethanolamine containing phosphatides showed lower figures (non significant). The fatty acid pattern of the ethanolamine-phosphatide-fraction of the diseased tissue a decrease of the 18:1 and the sum of 20:1 and 18:3 fatty acids as compared to the normal control, whereas the highly unsaturated, long-chained fatty acids 20:4 (arachidonic acid) and 22:6 (docosahexaenic acid) were elevated. The measurement of lipidhydrolyzing enzymes resulted in an increased phospholipase A1 activity in the diseased tissue. The experimental data point to a decreased activity of the fatty acid elongation system in the course of MS. The decrease of the acidic glycerophosphatides might be due to the increased phospholipase A1 activity.

Adult↗
PubMed1995

Studies on the synthesis of dehydroepiandrosterone (DHEA) phosphatide.

Synthetic dehydroepiandrosterone (DHEA) phosphatide 1c, (R = C15H31), was prepared by three methods. The most efficient of these involved the coupling of the commercially available DHEA 1a and commercially available phosphatidic acid 2, via mesitylene sulfonyl chloride and pyridine. Alternatively, DHEA-3-phosphate 1b was coupled with dipalmitoyl glycerol 3 in the same way. The third synthesis gave 1c by coupling DHEA with the cyclic phosphotriester 4 followed by deblocking.

Dehydroepiandrosterone↗
PubMed1970

Phosphatidic acid and phosphatidylinositol metabolism in Schizosaccharomyces pombe.

The phospholipid composition of Schizosaccharomyces pombe was not markedly affected by changes in the phosphate concentration of the medium or phase of growth. The major fatty acids in the total lipid extract and purified phosphatidylinositol were palmitic acid and oleic acid. Phosphatidic acid was synthesized by acylation of l-3-glycerophosphate in Schiz. pombe and phosphatidate phosphohydrolase was present. Phosphatidylinositol synthesis from inositol occurred in the absence of CDP-diglyceride. Even with dialysed cell-free preparations, the inositol lipid was synthesized by an apparently energy-independent route, at rates greater than would be required during cell growth. Phosphatidylinositol appeared to be broken down by a phospholipase D. All the enzymes examined were particulate; similar activities were found in Saccharomyces cerevisiae.

Cell-Free System↗
PubMed1983

Phosphatidic acid and phosphatidylinositol labelling in adipose tissue. The role of endogenously formed adenosine.

Incorporation of [32P]Pi into phosphatidic acid and phosphatidylinositol of hamster epididymal adipocytes was partially inhibited by 3-isobutyl-1-methylxanthine. This effect of 3-isobutyl-1-methylxanthine was antagonized by isopropyl-N6-phenyladenosine but not by 2',5'-dideoxyadenosine, prostaglandin E1 or clonidine. N6-Phenylisopropyladenosine did not affect incorporation of [32P]Pi into phosphatidic acid or phosphatidylinositol when 3-isobutyl-1-methylxanthine was not present. In contrast with 3-isobutyl-1-methylxanthine inhibition of [32P]Pi incorporation into phospholipids, which was blocked only by N6-phenylisopropyladenosine, accelerated lipolysis was blocked by prostaglandin E1, clonidine and 2',5'-dideoxyadenosine as well as by N6-phenylisopropyladenosine. Phospholipid labelling was also decreased in the presence of adenosine deaminase, but not in the presence of isoprenaline (isoproterenol). The stimulatory effect of N6-phenylisopropyladenosine on [32P]Pi incorporation into phospholipids in cells exposed to 3-isobutyl-1-methylxanthine was evident as soon as 3 min after addition of the adenosine analogue and maximum 10 min after its addition. As observed by others, [32P]Pi incorporation into phospholipids was increased by the alpha 1-selective agonist methoxamine. The stimulatory effect of methoxamine occurred with a time course similar to that of N6-phenylisopropyladenosine and was present at nearly equal magnitude in the absence or presence of 3-isobutyl-1-methylxanthine. The inhibitory effects of 3-isobutyl-1-methylxanthine and adenosine deaminase on phospholipid labelling are attributed to blockade of the action, or to the enzymic removal, of adenosine formed in and released from the fat-cells during their incubation. Supporting this view is the selective reversal of the actions of 3-isobutyl-1-methylxanthine and of adenosine deaminase by N6-phenylisopropyladenosine. These findings suggest an important role for endogenous adenosine in regulation of phospholipid turnover in adipocytes.

1-Methyl-3-isobutylxanthine↗