Human interleukin-3 stimulates a phosphatidylcholine specific phospholipase C and protein kinase C translocation.

Human interleukin-3 binds to a high affinity receptor composed of alpha- and beta-subunits. The beta-subunit is responsible for signal transduction but does not contain any intrinsic tyrosine kinase activity or other consensus motifs related to intracellular signaling. Previous work using IL-3 dependent MO7E cells has suggested a major role only for non-receptor tyrosine kinase activation in IL-3 signal transduction. We have shown, however, that engagement of the human interleukin-3 receptor induces the translocation of protein kinase C from the cytosol to the cell membrane in MO7E cells. This translocation is accompanied by rapid (2-5 min) accumulation of 1'2'-diacylglycerol (twice control values) in the absence of an increase in intracellular Ca2+. Prelabeling cells with [3H]glycerol or [3H]-choline demonstrated rapid release of [3H]phosphorylcholine and a decrease in [3H]glycerol-labeled phosphatidylcholine in response to IL-3 stimulation. In addition, IL-3 did not induce phosphatidic acid accumulation, and the IL-3 induced diacylglycerol accumulation was blocked by p-bromophenacylbromide (a phospholipase C inhibitor). It is thus likely that interleukin-3 is activating a phosphatidylcholine specific phospholipase C rather than a phospholipase D. Finally, genistein and herbimycin, specific tyrosine kinase inhibitors, inhibited both IL-3 induced protein kinase C translocation and the accumulation of diacylglycerol. Thus, IL-3 induced tyrosine phosphorylation may result in activation of a phosphatidylcholine phospholipase C and protein kinase C.