Ca2+ -independent cytosolic phospholipase A in HL-60 cells differentiating to granulocytes.
The release of various fatty acids (FAs) from permeabilized HL-60 cells, predominantly oleic acid (OA) rather than arachidonic acid, was greatly enhanced by GTP-gamma-S and vanadate [Tsujishita, Y., Asaoka, Y. and Nishizuka, Y., Proc. Natl. Acad. Sci. USA 91 (1994) 6274-62781. The present study shows that phospholipase A (A2/A1) activity which cleaves the acyl group from both sn-2 and sn-1 positions of phosphatidylethanolamine (PtdEtn) is increased in HL-60 cells during differentiation to granulocyte-like cells. This enzyme does not require Ca2+ and releases various FAs, preferentially OA from PtdEtn and, to lesser extent, from lysoPtdEtn. Other phospholipids including phosphatidylcholine and phosphatidic acid serve as very poor substrates. Although further studies are necessary to show the direct link of this enzyme activation to receptor stimulation, the results described here imply that this enzyme is responsible for the release of various FAs, particularly OA, from permeabilized HL-60 cells.
Hullin-Matsuda
F
F
Biosignal Research Center, Kobe University, Japan.
Tsujishita
Y
Y
Nishizuka
Y
Y
D002118:Calcium / Q000502:physiology; D002454:Cell Differentiation; D003600:Cytosol / Q000201:enzymology*; D005227:Fatty Acids / Q000378:metabolism; D006098:Granulocytes / Q000166:cytology / Q000201:enzymology*; D018922:HL-60 Cells; D006801:Humans; D019301:Oleic Acid / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D013379:Substrate Specificity
D005227:Fatty Acids; D010714:Phosphatidylethanolamines; D019301:Oleic Acid; D010741:Phospholipases A; D002118:Calcium