scholarly journals Diverse Functions of Secretory Phospholipases A2

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Preetha Shridas ◽  
Nancy R. Webb
Keyword(s):  
Arachidonic Acid ◽  
Platelet Activating Factor ◽  
Low Molecular Weight ◽  
Biological Processes ◽  
Calcium Dependent ◽  
Phospholipases A2 ◽  
Acid Release ◽  
Hydrolysis Of ◽  
Catalytic Dyad ◽  
Secreted Enzymes

Phospholipase A2 enzymes (PLA2s) catalyze the hydrolysis of glycerophospholipids at their sn-2 position releasing free fatty acids and lysophospholipids. Mammalian PLA2s are classified into several categories of which important groups include secreted PLA2s (sPLA2s) and cytosolic PLA2s (cPLA2s) that are calcium-dependent for their catalytic activity and calcium-independent cytosolic PLA2s (iPLA2s). Platelet-activating factor acetylhydrolases (PAF-AHs), lysosomal PLA2s, and adipose-specific PLA2 also belong to the class of PLA2s. Generally, cPLA2 enzymes are believed to play a major role in the metabolism of arachidonic acid, the iPLA2 family to membrane homeostasis and energy metabolism, and the sPLA2 family to various biological processes. The focus of this review is on recent research developments in the sPLA2 field. sPLA2s are secreted enzymes with low molecular weight (with the exception of GIII sPLA2), Ca2+-requiring enzymes with a His-Asp catalytic dyad. Ten enzymatically active sPLA2s and one devoid of enzymatic activity have been identified in mammals. Some of these sPLA2s are potent in arachidonic acid release from cellular phospholipids for the biosynthesis of eicosanoids, especially during inflammation. Individual sPLA2 enzymes exhibit unique tissue and cellular localizations and specific enzymatic properties, suggesting their distinct biological roles. Recent studies indicate that sPLA2s are involved in diverse pathophysiological functions and for most part act nonredundantly.

scholarly journals Selective hydrolysis of plasmalogens in endothelial cells following thrombin stimulation

1998 ◽  
Vol 275 (6) ◽  
pp. C1498-C1507 ◽  
Author(s):  
Michael H. Creer ◽  
Jane McHowat
Keyword(s):  
Endothelial Cells ◽  
Arachidonic Acid ◽  
Surrounding Medium ◽  
Selective Hydrolysis ◽  
Kinase C ◽  
Bromoenol Lactone ◽  
Acid Release ◽  
Induced Changes ◽  
Hydrolysis Of ◽  
Pkc Activation

The present study was performed to characterize thrombin-stimulated phospholipase A2(PLA2) activity and the resultant release of lysophospholipids from endothelial cells. The majority of PLA2 activity in endothelial cells was membrane associated, Ca2+ independent, and arachidonate selective. Incubation with thrombin increased membrane-associated PLA2 activity using both plasmenylcholine and alkylacyl glycerophosphocholine substrates in the absence of Ca2+, with no increase in activity observed with phosphatidylcholine substrate. The increased PLA2 activity was accompanied by arachidonic acid and lysoplasmenylcholine (LPlasC) release from endothelial cells into the surrounding medium. Thrombin-induced changes were duplicated by stimulation with the thrombin-receptor-directed peptide SFLLRNPNDKYEPF. Pretreatment with the Ca2+-independent PLA2 inhibitor bromoenol lactone blocked thrombin-stimulated increases in PLA2 activity, arachidonic acid, and LPlasC release. Stimulation of protein kinase C (PKC) increased basal PLA2 activity and LPlasC production. Thrombin-stimulated PLA2 activity and LPlasC production were enhanced with PKC activation and completely prevented with PKC downregulation. Thus thrombin treatment of endothelial cells activates a PKC-activated, membrane-associated, Ca2+-independent PLA2 that selectively hydrolyzes arachidonylated, ether-linked phospholipid substrates, resulting in LPlasC and arachidonic acid release.

scholarly journals Platelet activating factor stimulates arachidonic acid release in differentiated keratinocytes via arachidonyl non-selective phospholipase A2

2009 ◽  
Vol 302 (3) ◽  
pp. 221-227 ◽  
Author(s):  
Katarina Mariann Jørgensen ◽  
Hanne Solvang Felberg ◽  
Rolf K. Berge ◽  
Astrid Lægreid ◽  
Berit Johansen
Keyword(s):  
Arachidonic Acid ◽  
Phospholipase A2 ◽  
Platelet Activating Factor ◽  
Arachidonic Acid Release ◽  
Acid Release

scholarly journals Arachidonic acid release in rabbit neutrophils

1989 ◽  
Vol 257 (3) ◽  
pp. 633-637 ◽  
Author(s):  
W Tao ◽  
T F P Molski ◽  
R I Sha'afi
Keyword(s):  
Arachidonic Acid ◽  
Pertussis Toxin ◽  
Kinase Inhibitor ◽  
Regulatory Protein ◽  
Platelet Activating Factor ◽  
Arachidonic Acid Release ◽  
Membrane Perturbation ◽  
Acid Release ◽  
Guanine Nucleotide Regulatory Protein ◽  
Dose Dependent

[3H]Arachidonic acid is released after stimulation of rabbit neutrophils with fMet-Leu-Phe or platelet-activating factor (PAF). The release is rapid and dose-dependent, and is inhibited in phorbol 12-myristate 13-acetate (PMA)-treated rabbit neutrophils. The protein kinase C (PKC) inhibitor 1-(5-isoquinoline-sulphonyl)-2-methylpiperazine (H-7) prevents this inhibition. In addition, PMA increases arachidonic acid release in H-7-treated cells stimulated with fMet-Leu-Phe. [3H]Arachidonic acid release, but not the rise in the concentration of intracellular Ca2+, is inhibited in pertussis-toxin-treated neutrophils stimulated with PAF. The diacylglycerol kinase inhibitor R59022 increases the concentration of diacylglycerol and potentiates [3H]arachidonic acid release in neutrophils stimulated with fMet-Leu-Phe. This potentiation is not inhibited by H-7. These results suggest several points. (1) A rise in the intracellular concentration of free Ca2+ is not sufficient for arachidonic acid release in rabbit neutrophils stimulated by physiological stimuli. (2) A functional pertussis-toxin-sensitive guanine nucleotide regulatory protein and/or one or more of the changes produced by phospholipase C activation are necessary for arachidonic acid release produced by physiological stimuli. (3) Agents that stimulate PKC potentiate arachidonic acid release, and this potentiation is not inhibited by H-7. These agents produce their actions in part by direct membrane perturbation.

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