RNA interference suggests a primary role for monoacylglycerol lipase in the degradation of the endocannabinoid 2-arachidonoylglycerol.
The endogenous cannabinoid 2-arachidonoylglycerol (2-AG) is produced by neurons and other cells in a stimulus-dependent manner and undergoes rapid biological inactivation through transport into cells and catalytic hydrolysis. The enzymatic pathways responsible for 2-AG degradation are only partially understood. We have shown previously that overexpression of monoacylglycerol lipase (MGL), a cytosolic serine hydrolase that cleaves 1- and 2-monoacylglycerols to fatty acid and glycerol, reduces stimulus-dependent 2-AG accumulation in primary cultures of rat brain neurons. We report here that RNA interference-mediated silencing of MGL expression greatly enhances 2-AG accumulation in HeLa cells. After stimulation with the calcium ionophore ionomycin, 2-AG levels in MGL-silenced cells were comparable with those found in cells in which 2-AG degradation had been blocked using methyl arachidonyl fluorophosphonate, a nonselective inhibitor of 2-AG hydrolysis. The results indicate that MGL plays an important role in the degradation of endogenous 2-AG in intact HeLa cells. Furthermore, immunodepletion experiments show that MGL accounts for at least 50% of the total 2-AG-hydrolyzing activity in soluble fractions of rat brain, suggesting that this enzyme also contributes to 2-AG deactivation in the central nervous system.
Department of Pharmacology, University of California, Irvine, 360 Med Surge II, Irvine, CA 92697, USA.
Thien P
TP
Dinh
Satish
S
Kathuria
Daniele
D
Piomelli
D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism*; D001921:Brain / Q000201:enzymology; D063385:Cannabinoid Receptor Modulators / Q000378:metabolism; D002478:Cells, Cultured; D063388:Endocannabinoids; D020868:Gene Silencing / Q000187:drug effects; D005989:Glycerides / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D008994:Monoacylglycerol Lipases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009841:Oligonucleotides / Q000494:pharmacology; D034622:RNA Interference / Q000502:physiology*; D051381:Rats
D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D063388:Endocannabinoids; D005989:Glycerides; D009841:Oligonucleotides; C094503:glyceryl 2-arachidonate; D008994:Monoacylglycerol Lipases