Structural determinants for calcium mobilization by prostaglandin E2 and prostaglandin F2α glyceryl esters in RAW 264.7 cells and H1819 cells

2-Arachidonoylglycerol is oxygenated by cyclooxygenase-2 to form prostaglandin glyceryl esters. Previous work in this laboratory has suggested that PGE2-G activates a novel G protein-coupled receptor in a murine macrophage-like cell line, RAW 264.7. To probe the structural determinants for the putative receptor in RAW 264.7 cells, a panel of 10 analogs was tested for their ability to increase intracellular calcium. These analogs included PGE2- and PGF2α-ethanolamide, 4 PGE2 glyceryl ester analogs, and 4 PGF2α glyceryl ester analogs. The glyceryl ester analogs differed in the positioning of the hydroxyl groups in the glycerol moiety and the type of linker (ester, amide, or thioester) of the prostaglandin to the glycerol moiety. Compounds were also evaluated in a human non-small cell lung cancer cell line (H1819). The glycerol moiety was required for the calcium response. All glyceryl ester analogs but not ethanolamides caused a concentration-dependent increase in calcium levels in both RAW 264.7 and H1819 cells. An amide or ester linkage was preferable to a thioester linkage. The EC50 values did not significantly change when the positioning of the hydroxyls was varied. This calcium response induced by the glyceryl ester analogs appears to be independent of the putative hydrolysis products, PGE2 and PGF2α, and appears to represent a novel signaling pathway.