A Comprehensive Profile of Brain Enzymes that Hydrolyze the Endocannabinoid 2‐Arachidonoylglycerol

Abstract

The endocannabinoid system is the signaling network hijacked by the active component of marijuana, tetrahydrocannibinol (THC), which elicits its effects by activating the cannabinoid (CB) receptors. The endogenous ligands of the CB receptors (“endocannabinoids”) include the lipid transmitters anandamide and 2‐arachidonoyl glycerol (2‐AG). Endocannabinoids have been implicated a wide range of physiological processes including appetite, pain, anxiety and cognition. Endocannabinoid levels in the central nervous system are tightly controlled by enzymatic biosynthesis and degradation. Inactivation of anandamide by fatty acid amide hydrolase (FAAH) has been well characterized, but less is known about the degradation of 2‐AG, which can be hydrolyzed by multiple enzymes in vitro including FAAH and monoacylglyceride lipase (MAGL). We adopted a functional proteomic strategy including activity‐based protein profiling (ABPP) and pharmacological inhibition studies to comprehensively profile 2‐AG hydrolases in the mouse brain. Our results reveal that ~85% of 2‐AG hydrolase activity in mouse brain membranes is performed by MAGL, with the remaining ~15% being catalyzed by two previously uncharacterized enzymes ABHD6 and ABHD12. We determined that MGL, ABHD6, and ABHD12 occupy distinct subcellular localizations, suggesting that they may be responsible for regulating distinct pools of 2‐AG in the nervous system. This work was supported by the National Institutes of Health grants DA015197 and DA017259 (B.F.C), a Fletcher Jones Foundation Scholarship (J.L.B.), the Daniel Koshland Fellowship in Enzyme Biochemistry (G.M.S.), the Skaggs Institute for Chemical Biology, and the Helen L. Dorris Institute for the Study of Neurological and Psychiatric Disorders of Children and Adolescents.