Phospholipase A2 in macrophage plasma membrane releases arachidonic acid from phosphatidylinositol

1988 ◽  
Vol 971 (2) ◽  
pp. 121-126 ◽  
Author(s):  
Yasuko Shibata ◽  
Yoshimitsu Abiko ◽  
Hisashi Takiguchi
Keyword(s):  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Phospholipase A2

Cytosolic phospholipase A2-α associates with plasma membrane, endoplasmic reticulum and nuclear membrane in glomerular epithelial cells

2000 ◽  
Vol 353 (1) ◽  
pp. 79-90 ◽  
Author(s):  
Jianhong LIU ◽  
Tomoko TAKANO ◽  
Joan PAPILLON ◽  
Abdelkrim KHADIR ◽  
Andrey V. CYBULSKY
Keyword(s):  
Endoplasmic Reticulum ◽  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Epithelial Cells ◽  
Phospholipase A2 ◽  
Cytosolic Phospholipase A2 ◽  
Membrane Association ◽  
Cytosolic Phospholipase ◽  
Glomerular Epithelial Cells ◽  
In Cells

Eicosanoids mediate complement-dependent glomerular epithelial injury in experimental membranous nephropathy. The release of arachidonic acid from phospholipids by cytosolic phospholipase A2 (cPLA2) is the rate-limiting step in eicosanoid synthesis. The present study examines the association of cPLA2 with membranes of organelles. Glomerular epithelial cells were disrupted by homogenization in Ca2+-free buffer; organelles were separated by gradient centrifugation. The distribution of cPLA2 and organelles was analysed by immunoblotting with antibodies against cPLA2 and organelle markers, or by enzyme assay. In cells incubated with or without the Ca2+ ionophore ionomycin plus PMA, cPLA2 co-localized with plasma membrane, endoplasmic reticulum and nuclei, but not with mitochondria or Golgi. A greater amount of cPLA2 was associated with membranes in stimulated cells, but membrane-associated cPLA2 was readily detectable under resting conditions. The pattern of association of cPLA2 with membrane in cells treated with antibody and complement was similar to that in cells stimulated with ionomycin plus PMA; however, complement did not enhance the membrane association of cPLA2 protein. To determine the functional role of membrane association of cPLA2, phospholipids were labelled with [3H]arachidonic acid. Cells were then incubated with or without antibody and complement and were fractionated. Complement induced a loss of radioactivity from the plasma membrane, endoplasmic reticulum and nuclei, but not from the mitochondrial fraction. Thus the release of arachidonic acid by cPLA2 is due to the hydrolysis of phospholipids at multiple subcellular membrane sites, including the endoplasmic reticulum, plasma membrane and nucleus.

Phospholipase A2 inhibition results in sequestration of plasma membrane into electronlucent vesicles during IgG-mediated phagocytosis

1997 ◽  
Vol 110 (17) ◽  
pp. 2041-2052 ◽  
Author(s):  
M.R. Lennartz ◽  
A.F. Yuen ◽  
S.M. Masi ◽  
D.G. Russell ◽  
K.F. Buttle ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Phospholipase A2 ◽  
Time Course ◽  
Microscopy Imaging ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Bromoenol Lactone ◽  
Acid Release ◽  
Gold Marker

Arachidonic acid is essential for antibody-mediated phagocytosis but its role in this process has not been defined. The phospholipase A2 inhibitor bromoenol lactone decreases arachidonic acid release and arrests phagocytosis; this effect is bypassed by the addition of arachidonic acid to bromoenol lactone-treated cells. In this morphological study, monocytes treated with bromoenol lactone accumulate electronlucent vesicles in the cytoplasm underlying bound targets. The vesicles are not contiguous with the plasma membrane as they are not labeled with cationized ferritin and are not connected to the plasma membrane as determined by high voltage electron microscopy imaging. However, if the plasma membrane is decorated with wheat germ agglutinin-gold prior to vesicle formation, virtually all vesicles contain the gold marker, indicating that they are plasma membrane-derived. The number of vesicles decreases dramatically upon addition of arachidonic acid to phospholipase A2-inhibited monocytes and phagocytosis is restored. Time course studies reveal electronlucent regions surrounding targets at early timepoints and a morphology consistent with fusion of electronlucent vesicles into the developing phagosome. These results are consistent with the following model: during the early stages of antibody-mediated phagocytosis, plasma membrane is sequestered in intracellular vesicles that provide membrane for the forming phagosome via fusion events that require arachidonic acid.

Further Studies On The Purified Phospholipase A2 From Human Platelet Plasma Membranes

1981 ◽  
Author(s):  
R Apitz-Castro ◽  
M R Cruz ◽  
M Mas ◽  
M K Jain
Keyword(s):  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Phosphatidic Acid ◽  
Phospholipase A2 ◽  
Plasma Membranes ◽  
Specific Activity ◽  
Blood Platelets ◽  
Fold Increase ◽  
Biochemical Properties ◽  
Mole Percent

The activation of a phospholipase A2 has been postulated in the release of arachidonic acid from phospholipids of platelet plasma membrane. The present communication deals with the biochemical properties of a phospholipase A2 isolated from human blood platelets. Phospholipase A2 from human platelets have been isolated to homogeneity through an acid or salt extraction, followed by affinity chromatography purification. The enzyme is copurified with the platelet plasma membrane, It has a MW of about 50,000 Dalton. It shows an optimum pH at 9.4 and requires calcium for its activity. Although it attacks a variety of phospholipid substrates, there is a preference for unsaturated phospholipids. Diarachidonoy1-PC liposomes can be hydrolyzed in the absence of any additive. The specific activity is markedly affected by the quality of the interface, showing variations of more than 10 fold between different substrate forms. The purified enzyme is considerably more active on the aggregated form of the substrate than on the monomeric form. Saturation behavior, consistent with Michaelis-Menten type of kinetics is observed at higher concentration of the micellar substrate. A four-fold increase in rate is observed when the enzyme is assayed in the presence of fatty acid + lysophospholipid. Maximal rates are obtained at a 20 mole percent of products to substrate. 1,2-diglyceride and phosphatidic acid stimulates the hydrolysis of phosphatidylcholine by the purified enzyme, however, in these forms of substrate, neither the diglyceride nor phosphatidic acid is hydrolyzed. Under optimal condition, the phospholipase A2 activity corresponds to at least 13 nmol/min/109 platelets. Activation of this enzyme by some intermediate related to the phospholipase C pathway might play a role in the stimulus- linked release of platelet arachidonic acid.

Stimulation of Ca(2+)-dependent exocytosis of the sperm acrosome by cAMP acting downstream of phospholipase A2

Reproduction ◽  
2000 ◽  
pp. 57-68 ◽  
Author(s):  
J Garde ◽  
ER Roldan
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Phospholipase C ◽  
Phosphodiesterase Inhibitors ◽  
Dibutyryl Camp ◽  
Camp Phosphodiesterase ◽  
Ram Sperm ◽  
Camp Formation ◽  
Stimulation Of

Spermatozoa undergo exocytosis in response to agonists that induce Ca2+ influx and, in turn, activation of phosphoinositidase C, phospholipase C, phospholipase A2, and cAMP formation. Since the role of cAMP downstream of Ca2+ influx is unknown, this study investigated whether cAMP modulates phospholipase C or phospholipase A2 using a ram sperm model stimulated with A23187 and Ca2+. Exposure to dibutyryl-cAMP, phosphodiesterase inhibitors or forskolin resulted in enhancement of exocytosis. However, the effect was not due to stimulation of phospholipase C or phospholipase A2: in spermatozoa prelabelled with [3H]palmitic acid or [14C]arachidonic acid, these reagents did not enhance [3H]diacylglycerol formation or [14C]arachidonic acid release. Spermatozoa were treated with the phospholipase A2 inhibitor aristolochic acid, and dibutyryl-cAMP to test whether cAMP acts downstream of phospholipase A2. Under these conditions, exocytosis did not occur in response to A23187 and Ca2+. However, inclusion of dibutyryl-cAMP and the phospholipase A2 metabolite lysophosphatidylcholine did result in exocytosis (at an extent similar to that seen when cells were treated with A23187/Ca2+ and without the inhibitor). Inclusion of lysophosphatidylcholine alone, without dibutyryl-cAMP, enhanced exocytosis to a lesser extent, demonstrating that cAMP requires a phospholipase A2 metabolite to stimulate the final stages of exocytosis. These results indicate that cAMP may act downstream of phospholipase A2, exerting a regulatory role in the exocytosis triggered by physiological agonists.

Interaction between cortisol and arachidonic acid on the secretion of LH from ovine pituitary tissue

1991 ◽  
Vol 131 (1) ◽  
pp. 87-94 ◽  
Author(s):  
A. W. Nangalama ◽  
G. P. Moberg
Keyword(s):  
Arachidonic Acid ◽  
Plasma Membrane ◽  
Suppressive Effect ◽  
Inhibitory Effect ◽  
Adrenal Steroids ◽  
Membrane Phospholipids ◽  
Pituitary Tissue ◽  
Receptor Sites ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone

ABSTRACT In several species, glucocorticoids act directly on the pituitary gonadotroph to suppress the gonadotrophin-releasing hormone (GnRH)-induced secretion of the gonadotrophins, especially LH. A mechanism for this action of these adrenal steroids has not been established, but it appears that the glucocorticoids influence LH release by acting on one or more post-receptor sites. This study investigated whether glucocorticoids disrupt GnRH-induced LH release by altering the liberation of arachidonic acid from plasma membrane phospholipids, a component of GnRH-induced LH release. Using perifused ovine pituitary tissue, it was established that exposure of gonadotrophs to 1–1000 nmol cortisol/l for 4 h or longer significantly reduced GnRH-stimulated LH release with the maximal inhibitory effect being observed after 6 h of exposure to cortisol. This suppressive effect of cortisol could be reversed by administration of arachidonic acid, which in its own right could stimulate LH release from ovine pituitary tissue. Furthermore, the inhibitory effect of cortisol on GnRH-stimulated LH release could be directly correlated with decreased pituitary responsiveness to GnRH-stimulated arachidonic acid liberation, consistent with our hypothesis that glucocorticoids can suppress GnRH-induced secretion of LH by reducing the amount of arachidonic acid available for the exocytotic response of GnRH. Journal of Endocrinology (1991) 131, 87–94

scholarly journals Demonstration of calcium-dependent phospholipase A2 activity in membrane preparation of rabbit neutrophils. Absence of activation by fMet-Leu-Phe, phorbol 12-myristate 13-acetate and A-kinase

1988 ◽  
Vol 250 (2) ◽  
pp. 343-348 ◽  
Author(s):  
T Matsumoto ◽  
W Tao ◽  
R I Sha'afi
Keyword(s):  
Arachidonic Acid ◽  
Cyclic Amp ◽  
Phospholipase A2 ◽  
Kinase Inhibitor ◽  
Calcium Ionophore ◽  
Membrane Preparation ◽  
Free Calcium ◽  
Ionophore A23187 ◽  
Pla2 Activity ◽  
Intact Cells

The presence of a phospholipase A2 (PLA2) activity in rabbit neutrophil membrane preparation that is able to release [1-14C]oleic acid from labelled Escherichia coli has been demonstrated. The activity is critically dependent on the free calcium concentration and marginally stimulated by GTP gamma S. More than 80% of maximal activity is reached at 10 microM-Ca2+. The chemotactic factor, fMet-Leu-Phe, does not stimulate the PLA2 activity in this membrane preparation. Pretreatment of the membrane preparation, under various experimental conditions, or intact cells, before isolation of the membrane with phorbol 12-myristate 13-acetate (PMA), does not affect PLA2 activity. Addition of the catalytic unit of cyclic AMP-dependent kinase to membrane preparation has no effect on PLA2 activity. Pretreatment of the intact neutrophil with dibutyryl-cAMP before isolation of the membrane produces a small but consistent increase in PLA2 activity. The activity of PLA2 in membrane isolated from cells treated with the protein kinase inhibitor 1-(5-isoquinolinesulphonyl)-2-methyl piperazine dihydrochloride (H-7) is significantly decreased. Furthermore, although the addition of PMA to intact rabbit neutrophils has no effect on the release of [3H]arachidonic acid from prelabelled cells, it potentiates significantly the release produced by the calcium ionophore A23187. This potentiation is not due to an inhibition of the acyltransferase activity. H-7 inhibits the basal release of arachidonic acid but does not inhibit the potentiation by PMA. These results suggest several points. (1) fMet-Leu-Phe does not stimulate PLA2 directly, and its ability to release arachidonic acid in intact neutrophils is mediated through its action on phospholipase C. (2) The potentiating effect of PMA on A23187-induced arachidonic acid release is most likely due to PMA affecting either the environment of PLA2 and/or altering the organization of membrane phospholipids in such a way as to increase their susceptibility to hydrolysis. (3) The intracellular level of cyclic AMP probably does not directly affect the activity of PLA2.

Sign in / Sign up

Export Citation Format

Share Document