The glyceryl ester of prostaglandin E2 mobilizes calcium and activates signal transduction in RAW264.7 cells

Glyceryl prostaglandins (PG-Gs) are generated by the oxygenation of the endocannabinoid, 2-arachidonylglycerol, by cyclooxygenase 2. The biological consequences of this selective oxygenation are uncertain because the cellular activities of PG-Gs have yet to be defined. We report that the glyceryl ester of PGE(2), PGE(2)-G, triggers rapid, concentration-dependent Ca2+ accumulation in a murine macrophage-like cell line, RAW264.7. Ca2+ mobilization is not observed after addition of PGE(2), PGD(2)-G, or PGF(2alpha)-G but is observed after addition of PGF(2alpha). Moreover, PGE(2)-G, but not PGE(2), stimulates a rapid but transient increase in the levels of inositol 1,4,5-trisphosphate (IP3) as well as the membrane association and activation of PKC. PGE(2)-G induces a concentration-dependent increase in the levels of phosphorylated extracellular signal regulated kinases 1 and 2 through a pathway that requires the activities of PKC, IP3 receptor, and phospholipase C beta. The results indicate that PGE(2)-G triggers Ca2+ mobilization, IP3 synthesis, and activation of PKC in RAW264.7 macrophage cells at low concentrations. These responses are independent of the hydrolysis of PGE(2)-G to PGE(2).