CA2-INDEPENDENT CYTOSOLIC PHOSPHOLIPASE-A IN HL-60 CELLS DIFFERENTIATING TO GRANULOCYTES()

The release of various fatty acids (FAs) from permeabilized HL-60 cell s, predominantly oleic acid (OA) rather than arachidonic acid, was gre atly enhanced by GTP-gamma-S and vanadate [Tsujishita, Y., Asaoka, Y. and Nishizuka, Y., Proc, Natl, Acad, Sci. USA 91 (1994) 6274-6278]. Th e present study shows that phospholipase A (A(2)/A(1)) activity which cleaves the acyl group from both sn-2 and sn-l positions of phosphatid ylethanolamine (PtdEtn) is increased in HL-60 cells during differentia tion to granulocyte-like cells, This enzyme does not require Ca2+ and releases various FAs, preferentially OA from PtdEtn and, to lesser ext ent, from lysoPtdEtn. Other phospholipids including phosphatidylcholin e and phosphatidic acid serve as very poor substrates, Although furthe r studies are necessary to show the direct link of this enzyme activat ion to receptor stimulation, the results described here imply that thi s enzyme is responsible for the release of various FAs, particularly O A, from permeabilized HL-60 cells. (C) 1997 Federation of European Bio chemical Societies.