title: A key role for diacylglycerol lipase-alpha in metabotropic glutamate receptor-dependent endocannabinoid mobilization.
abstract: Activation of group I metabotropic glutamate (mGlu) receptors recruits the endocannabinoid system to produce both short- and long-term changes in synaptic strength in many regions of the brain. Although there is evidence that the endocannabinoid 2-arachidonoylglycerol (2-AG) mediates this process, the molecular mechanism underlying 2-AG mobilization remains unclear. In the present study, we used a combination of genetic and targeted lipidomic approaches to investigate the role of the postsynaptic membrane-associated lipase, diacylglycerol lipase type-alpha (DGL-alpha), in mGlu receptor-dependent 2-AG mobilization. DGL-alpha overexpression in mouse neuroblastoma Neuro-2a cells increased baseline 2-AG levels. This effect was accompanied by enhanced utilization of the 2-AG precursor 1-stearoyl,2-arachidonoyl-sn-glycerol and increased accumulation of the 2-AG breakdown product arachidonic acid. A similar, albeit less marked response was observed with other unsaturated and polyunsaturated monoacylglycerols, 1,2-diacylglycerols, and fatty acids. Silencing of DGL-alpha by RNA interference elicited lipidomic changes opposite those of DGL-alpha overexpression and abolished group I mGlu receptor-dependent 2-AG mobilization. Coimmunoprecipitation and site-directed mutagenesis experiments revealed that DGL-alpha interacts, via a PPxxF domain, with the coiled-coil (CC)-Homer proteins Homer-1b and Homer-2, two components of the molecular scaffold that enables group I mGlu signaling. DGL-alpha mutants that do not bind Homer maintained their ability to generate 2-AG in intact cells but failed to associate with the plasma membrane. The findings indicate that DGL-alpha mediates group I mGlu receptor-induced 2-AG mobilization. They further suggest that the interaction of CC-Homer with DGL-alpha is necessary for appropriate function of this lipase.
authors.affiliation: Department of Pharmacology, University of California, Irvine, CA 92697-4625, USA.
authors.forename: Kwang-Mook
authors.initials: KM
authors.lastname: Jung
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Astarita
authors.forename: Chenggang
authors.initials: C
authors.lastname: Zhu
authors.forename: Matthew
authors.initials: M
authors.lastname: Wallace
authors.forename: Ken
authors.initials: K
authors.lastname: Mackie
authors.forename: Daniele
authors.initials: D
authors.lastname: Piomelli
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000096:biosynthesis; D001095:Arachidonic Acids / Q000378:metabolism; D063385:Cannabinoid Receptor Modulators / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D063388:Endocannabinoids; D005989:Glycerides / Q000378:metabolism; D000072233:Homer Scaffolding Proteins; D006801:Humans; D007668:Kidney / Q000166:cytology; D008071:Lipoprotein Lipase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D009447:Neuroblastoma / Q000473:pathology; D010957:Plasmids; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection
chemical_list: D001095:Arachidonic Acids; D063385:Cannabinoid Receptor Modulators; D002352:Carrier Proteins; D063388:Endocannabinoids; D005989:Glycerides; C000606614:HOMER1 protein, human; D000072233:Homer Scaffolding Proteins; D034741:RNA, Small Interfering; D018094:Receptors, Metabotropic Glutamate; D011994:Recombinant Proteins; D016718:Arachidonic Acid; C094503:glyceryl 2-arachidonate; D008071:Lipoprotein Lipase