Interactions of 2-O-arachidonylglycerol ether and ibuprofen with the allosteric and catalytic subunits of human COX-2

• DOI: 10.1194/jlr.m067512
• Publication Date: 2016-04-09T04:04:31Z
• Authors: Liang Dong; Hechang Zou; Chong Yuan; Yu H. Hong; Charis L. Uhlson; Robert C. Murphy; William L. Smith
• Keywords: 0301 basic medicine; 0303 health sciences; Arachidonic Acid; Ibuprofen; Arachidonic Acids; Ether; Glycerides; 3. Good health; 03 medical and health sciences; Cyclooxygenase 2; Catalytic Domain; Humans; Prostaglandin H2; Allosteric Site; Endocannabinoids

Prostaglandin (PG) endoperoxide H synthase (PGHS)-2, also known as cyclooxygenase (COX)-2, can convert arachidonic acid (AA) to PGH2 in the committed step of PG synthesis. PGHS-2 functions as a conformational heterodimer composed of an allosteric (Eallo) and a catalytic (Ecat) monomer. Here we investigated the interplay between human (hu)PGHS-2 and an alternative COX substrate, the endocannabinoid, 2-arachidonoylglycerol (2-AG), as well as a stable analog, 2-O-arachidonylglycerol ether (2-AG ether). We also compared the inhibition of huPGHS-2-mediated oxygenation of AA, 2-AG, and 2-AG ether by the well-known COX inhibitor, ibuprofen. When tested with huPGHS-2, 2-AG and 2-AG ether exhibit very similar kinetic parameters, responses to stimulation by FAs that are not COX substrates, and modes of inhibition by ibuprofen. The 2-AG ether binds Ecat more tightly than Eallo and, thus, can be used as a stable Ecat-specific substrate to examine certain Eallo-dependent responses. Ibuprofen binding to Eallo of huPGHS-2 completely blocks 2-AG or 2-AG ether oxygenation; however, inhibition by ibuprofen of huPGHS-2-mediated oxygenation of AA engages a combination of both allosteric and competitive mechanisms.