Effects of ganglioside GM3 on phospholipid turnover of human leukemic J6-2 cells

Ganglioside GM(3) was reported to induce the differentiation of HL-60 cells to differentiate along the macrophage-monocytic route. We used human monocytoid leukemia J6-2 cells and successfully induced differentiation by GM(3). Because differentiation is accompanied by retarded growth rate and cell cycle is intimately related to phospholipid metabolism, so we explored how GM(3) was related to phospholipid metabolism. By using [(3)2P]Pi, [H-3-CH3]choline, [H-3-CH3]SAM, and [H-3]inositol as radioactive tracers, we studied the turnover changes of phospholipids and their metabolites induced by GM(3). For the morphological changes of differentiation to occur, the cells had to be treated with GM(3) at a concentration of 50 muM for 5-6 days, but the phospholipid changes occurred at a very early stage of GM(3) treatment (only 1 h). Our results indicate that GM(3) stimulated PE methylation pathway inhibited both CDP-choline pathway and PI cycle. The phospholipid changes may constitute the early events in differentiation induced by GM(3).