Interleukin‐2 stimulates a late increase in phosphatidic acid production in the absence of phospholipase D activation

The signal transduction pathways involving phospholipid metabolism during T-cell proliferation remain partly undefined. Herein we show that interleukin-2 caused a late (> 12 h) rise in the intracellular phosphatidic acid content of CTLL-2 cells which was a consequence of the activation of the enzyme diacylglycerol kinase. No activation of phospholipase D was observed at similar times. Incubation of the cells with a recognized diacylglycerol kinase a isoform inhibitor, R59499, prior to interleukin-2 stimulation was able to block cell cycle entry, diacyglycerol kinase activation and phosphatidic acid accumulation. In contrast, when R59499 was added 3 h after interleukin-2, few or no observable effects on the above three parameters were noticed. These results suggest that the early signaling employed by IL-2 involving the alpha isoform of diacylglycerol kinase is sufficient to control the late increase in phosphatidic acid and that phosphatidic acid is a mitogenic agent in T-cells.