ON THE EXPRESSION OF CYTOSOLIC CALCIUM-INDEPENDENT PHOSPHOLIPASE A(2)(88 KDA) IN IMMATURE AND MATURE MYELOID CELLS AND ITS ROLE IN LEUKOTRIENE SYNTHESIS IN HUMAN GRANULOCYTES

The human calcium-independent phospholipase A(2) (iPLA(2); 88 kDa) has recently been cloned (Larsson, P.K.A., Claesson, H.-E. and Kennedy, B .P. (1998) J. Biol. Chem. 272, 207-214), Here we demonstrate the expre ssion of the human iPLA(2) mRNA and its splice variants in blood proge nitor cells, immature leukemic cells and mature granulocytes, Chromato graphical resolvable iPLA(2) activity was found in the cytosolic fract ion of granulocytes and the activity was inhibited by the iPLA(2) inhi bitor bromoenol lactone, This drug also inhibited leukotriene synthesi s in human granulocytes, induced by low concentration of calcium ionop hore A23187 (0.10-0.15 mu M) or opsonized zymosan, These results sugge st that iPLA(2) is involved in the regulation of the pool of arachidon ic acid destined for leukotriene synthesis in human granulocytes. (C) 1998 Federation of European Biochemical Societies.