Net activity of phospholipase A2 in brain and the lack of stimulation of the phospholipase A2-acylation stem.
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ABSTRACT:
SUBMITTER: Rowe CE
PROVIDER: S-EPMC1164788 | biostudies-other | 1977 Apr
REPOSITORIES: biostudies-other
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Project description:Hydrolysis of phosphatidylcholine by phospholipase A2 of synaptic membranes i n Tris-CHl buffer was stimulated by cyclic AMP, cyclic GMP, cyclic CMP, cyclic UMP and adenosine (0.1 mm). In the presence of 1 mm-NaF and cofactors, the same cyclic nucleotides and adenosine (10 mm) stimulated the incorporation of added oleate into the choline glycerophospholipids of synaptic membranes. Cyclic AMP and noradrenaline stimulated the incorporation of added oleate into position 2 of choline glycerophospholipid. Stimulation of net acylation was increased by preincubation in conditions which stimulated hydrolysis of phosphatidylcholine. Cyclic AMP only slightly stimulated the transfer of oleate from oleoyl-CoA into choline glycerophospholipid. The optimum concentration of CaCl2 for the stimulation of hydrolysis by phospholipase A2 by cyclic AMP was 1 mum. Stimulation of the incorporation of added oleate was maximal in the CaCl2 concentration range 1 mum-1mm. MgCl2 also enhanced stimulations, maximum effects being obtained with concentrations of 10 mum and 0.5 mm for hydrolysis by phospholipase A2 and incorporation of added oleate respectively. ATP enhanced the stimulation of incorporation of oleate but had no effect on the cyclic nucleotide stimulation of hydrolysis of added phosphatidylcholine by phospholipase A2. Adenosine, guanosine, ADP and 5'-AMP (all at 1 mm) inhibited the stimulation of incorporation of oleate by cyclic nucleotides and inhibited the transfer of oleate from oleoyl-CoA to phospholipid. They did not inhibit the stimulation of hydrolysis of added phosphatidylcholine (by phospholipase A2) by cyclic nucleotides, but inhibited the stimulation by noradrenaline, acetylcholine, 5-hydroxytryptamine, dopamine (3,4-dihydroxyphenethylamine) and histamine. Preincubation of synaptic membranes in the water or buffer increased the net activity of phospholipase A2. Preincubation with a mixture of ATP and MgCl2 increased the initial rate of acylation of membrane lipid.
| S-EPMC1165578 | biostudies-other
Project description:1. The distribution of the hydrolyses of phosphatidylcholine by phospholipase A2 and phospholipase A1, and the hydrolysis of lysophosphatidylcholine by lysophospholipase, in subcellular and subsynaptosomal fractions of cerebral cortices of guinea-pig brain, was determined. 2. Noradrenaline stimulated hydrolysis by phospholipase A2 in whole synaptosomes, synaptic membranes and fractions containing synaptic vesicles. 3. Stimulation of hydrolysis by phospholipase A2 in synaptic membranes by noradrenaline was enhanced by CaCl2, and by a mixture of ATP and MgCl2. The optimum concentration of CaCl2, in the presence of ATP and MgCl2, for stimulation by 10 muM-noradrenaline was in the range 1-10muM. The optimum concentration for ATP-2MgCl2 in the presence of 1 muM-CaCl2 was in the range 0.1-1mM. 4. Hydrolysis by phospholipase A2 of synaptic membranes was also stimulated by acetylcholine, carbamoylcholine, 5-hydroxytryptamine, dopamine (3,4-dihydroxyphenethylamine), histamine, psi-aminobutyric acid, glutamic acid and aspartic acid. With appropriate concentrations of cofactors, sigmoidal dose-response curves were obtained, half-maximum stimulations being obtained with concentrations of stimulant in the range 0.1-1muM. 5. Taurine also stimulated hydrolysis of phosphatidylcholine by phospholipase A2. There were only slight stimulations with methylamine, ethylenediamine or spermidine. No stimulation was obtained with glucagon.
| S-EPMC1165527 | biostudies-other
Project description:Recent reports demonstrated an association of human parvovirus B19 with inflammatory cardiomyopathy (iCMP), which is accompanied by endothelial dysfunction. As intracellular Ca(2+) activity is a key regulator of cell function and participates in mechanisms leading to endothelial dysfunction, the present experiments explored the effects of the B19 capsid proteins VP1 and VP2. A secreted phospholipase A2 (PLA2)-like activity has been located in the VP1 unique region of the B19 minor capsid protein. As PLA2 has recently been shown to activate the store-operated or capacitative Ca(2+) channel I(CRAC), we analyzed the impact of the viral PLA2 motif on Ca(2+) entry. We cloned the VP1 and VP2 genes isolated from a patient suffering from fatal B19 iCMP into eukaryotic expression vectors. We also generated a B19 replication-competent plasmid to demonstrate PLA2 activity under the control of the complete B19 genome. After the transfection of human endothelial cells (HMEC-1), cytosolic Ca(2+) activity was determined by utilizing Fura-2 fluorescence. VP1 and VP2 expression did not significantly modify basal cytosolic Ca(2+) activity or the decline of cytosolic Ca(2+) activity following the removal of extracellular Ca(2+). However, expression of VP1 and of the full-length B19 clone, but not of VP2, significantly accelerated the increase of cytosolic Ca(2+) activity following the readdition of extracellular Ca(2+) in the presence of thapsigargin, indicating an activation of I(CRAC.) The effect of VP1 was mimicked by the PLA2 product lysophosphatidylcholine and abolished by an inactivating mutation of the PLA2-encoding region of the VP1 gene. Our observations point to the activation of Ca(2+) entry by VP1 PLA2 activity, an effect likely participating in the pathophysiology of B19 infection.
| S-EPMC1642163 | biostudies-literature
Project description:Mass levels of lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), a leukocyte-derived enzyme involved in the metabolism of low-density lipoprotein to pro-inflammatory mediators, are associated with prognosis after stroke. Lp-PLA(2) mass correlates only moderately with levels of Lp-PLA(2) activity. The relationship of Lp-PLA(2) activity to risk of stroke recurrence is unknown. We hypothesized that Lp-PLA(2) activity levels would predict risk of recurrence.In the population-based Northern Manhattan Stroke Study, first ischemic stroke patients >or=40 years were followed for recurrent stroke. Levels of Lp-PLA(2) activity were assessed in 467 patients, and categorized by quartile. Cox proportional hazard models were used to calculate hazard ratios (HR) and 95% confidence intervals (95% CI) for risk of recurrent stroke associated with marker quartiles after adjusting for demographics, vascular risk factors, and high-sensitivity C-reactive protein (hsCRP).Mean age was 68.9 +/- 12.7 years; 54.6% were women; 53.3% Hispanic, 27.2% black, and 17.8% white. Median follow-up was 4.0 years, and there were 80 recurrent strokes. Compared to the lowest quartile of Lp-PLA(2) activity, those in the highest had an increased risk of recurrent stroke (adjusted HR 2.54, 95% CI 1.01-6.39).Stroke patients with Lp-PLA(2) activity levels in the highest quartile, compared to those in the lowest quartile, had an increased risk of recurrence after first ischemic stroke. Further studies are warranted to determine whether this biomarker has clinical utility in determining high-risk populations of stroke survivors, and whether anti-inflammatory strategies that reduce levels of activity of Lp-PLA(2) reduce the risk of stroke recurrence.
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| S-EPMC2884554 | biostudies-literature
Project description:BackgroundPresynaptically neurotoxic phospholipases A(2) inhibit synaptic vesicle recycling through endocytosis.Principal findingsHere we provide insight into the action of a presynaptically neurotoxic phospholipase A(2) ammodytoxin A (AtxA) on clathrin-dependent endocytosis in budding yeast. AtxA caused changes in the dynamics of vesicle formation and scission from the plasma membrane in a phospholipase activity dependent manner. Our data, based on synthetic dosage lethality screen and the analysis of the dynamics of sites of endocytosis, indicate that AtxA impairs the activity of amphiphysin.ConclusionsWe identified amphiphysin and endocytosis as the target of AtxA intracellular activity. We propose that AtxA reduces endocytosis following a mechanism of action which includes both a specific protein-protein interaction and enzymatic activity, and which is applicable to yeast and mammalian cells. Knowing how neurotoxic phospholipases A(2) work can open new ways to regulate endocytosis.
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Project description:Secretory phospholipase A2 (sPLA2) is a critical component of insect and snake venoms and is secreted by mammalian leukocytes during inflammation. Elevated secretory PLA2 concentrations are associated with autoimmune diseases and septic shock. Many sPLA2's do not bind to plasma membranes of quiescent cells but bind and digest phospholipids on the membranes of stimulated or apoptotic cells. The capacity of these phospholipases to digest membranes of stimulated or apoptotic cells correlates to the exposure of phosphatidylserine. In the present study, the ability of the phosphatidyl-L-serine-binding protein, lactadherin to inhibit phospholipase enzyme activity has been assessed. Inhibition of human secretory phospholipase A2-V on phospholipid vesicles exceeded 90%, whereas inhibition of Naja mossambica sPLA2 plateaued at 50-60%. Lactadherin inhibited 45% of activity of Naja mossambica sPLA2 and >70% of human secretory phospholipase A2-V on the membranes of human NB4 leukemia cells treated with calcium ionophore A23187. The data indicate that lactadherin may decrease inflammation by inhibiting sPLA2.
| S-EPMC3806724 | biostudies-literature
Project description:A wealth of evidence suggests that Lipoprotein-associated phospholipase A2 (Lp-PLA2) plays a relevant role in atherogenesis and inflammation, which in turn are associated with the risk of developing dementia. The aim of this study was to evaluate whether serum Lp-PLA2 activity might be an early and/or late biomarker for different forms of dementia. Serum Lp-PLA2 activity was assessed in older patients with mild cognitive impairment (MCI, n = 166; median clinical follow-up = 29 months), Late-Onset Alzheimer's disease (LOAD, n = 176), vascular dementia (VAD, n = 43), dementia characterized by an overlap between LOAD and VAD (AD-VAD MIXED dementia) (n = 136), other dementia subtypes (n = 45), and cognitively normal controls (n = 151). We found a significant trend towards higher levels of Lp-PLA2 activity in VAD compared with the other groups (ANOVA, p = 0.028). Similarly, Lp-PLA2 activity was greater in MCI converting to VAD compared with those that did not or did convert to the other types of dementia (ANOVA, p = 0.011). After adjusting for potential confounders, high levels of Lp-PLA2 activity were associated with the diagnosis of VAD (O.R. = 2.38, 95% C.I. = 1.06-5.10), but not with other types of dementia. Our data suggest that increased serum Lp-PLA2 activity may represent a potential biomarker for the diagnosis of VAD.
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Project description:As saprophytes or disease causing microorganisms, fungi acquire nutrients from dead organic material or living host organisms. Lipids as structural components of cell membranes and storage compartments play an important role as energy-rich food source. In recent years, it also has become clear that lipids have a wide range of bioactive properties including signal transduction and cell to cell communication. Thus, it is not surprising that fungi possess a broad range of hydrolytic enzymes that attack neutral lipids and phospholipids. Especially during infection of a mammalian host, phospholipase A(2) (PLA(2)) enzymes released by fungi could play important roles not only for nutrient acquisition and tissue invasion, but for intricate modulation of the host's immune response. Sequencing of fungal genomes has revealed a wide range of genes encoding PLA(2) activities in fungi. We are just beginning to become aware of the significance these enzymes could have for the fungal cells and their interaction with the host.
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