Identification of the Major Prostaglandin Glycerol Ester Hydrolase in Human Cancer Cells [Enzymology]

October 9th, 2014 by Manna, J. D., Wepy, J. A., Hsu, K., Chang, J. W., Cravatt, B. F., Marnett, L. J.

Prostaglandin glycerol esters (PG-Gs) are produced as a result of the oxygenation of the endocannabinoid, 2-arachidonoylglycerol (2-AG), by cyclooxygenase 2. Understanding the role that PG-Gs play in a biological setting has been difficult because of their sensitivity to enzymatic hydrolysis. By comparing PG-G hydrolysis across human cancer cell lines to serine hydrolase activities determined by activity-based protein profiling, we identified lysophospholipase A2 (LYPLA2) as a major enzyme responsible for PG-G hydrolysis. The principal role played by LYPLA2 in PGE2-G hydrolysis was confirmed by siRNA knockdown. Purified, recombinant LYPLA2 hydrolyzed PG-Gs in the following order of activity - PGE2-G > PGF2α-G > PGD2-G; LYPLA2 hydrolyzed 1-AG but not 2-AG or arachidonoylethanolamide (AEA). Chemical inhibition of LYPLA2 in the mouse macrophage-like cell line, RAW264.7, elicited an increase in PG-G production. Our data indicate that LYPLA2 serves as a major PG-G hydrolase in human cells. Perturbation of this enzyme should enable selective modulation of PG-Gs without alterations in endocannabinoids, thereby providing a means to decipher the unique functions of PG-Gs in biology and disease.