Glycerophosphodiesterase 3 (GDE3) is a lysophosphatidylinositol-specific ectophospholipase C acting as an endocannabinoid signaling switch

• Published in: The Journal of biological chemistry
• Main Authors: Briand-Mésange, Fabienne, Pons, Véronique, Allart, Sophie, Masquelier, Julien, Chicanne, Gaëtan, Beton, Nicolas, Payrastre, Bernard, Muccioli, Giulio, Ausseil, Jérôme, Davignon, Jean-Luc, Salles, Jean-Pierre, Chap, Hugues
• Format: Journal Article
• Language: English
• Published: (United States) New York, NY Elsevier Inc. on behalf of American Society for Biochemistry and Molecular Biology 2020
• Subjects: 2-arachidonoylglycerol; Amino Acid Sequence; Animals; Arachidonic Acids; CB1; CB1/CB2; CB2; Endocannabinoid; Endocannabinoids; Female; G-protein–coupled receptor (GPCR); GDPD2; Glycerides; Glycerophosphodiesterase 3 (GDE3); GPR55; HEK293 Cells; Humans; Hydrolysis; Inositol Phosphates; Lysophosphatidylinositol; Lysophospholipid; Lysophospholipids; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Monoacylglycerol; Monoglycerides; Phospholipase C; Phosphoric Diester Hydrolases; Receptor, Cannabinoid, CB2; Receptors, Cannabinoid; Sequence Alignment; Signal Transduction; Spleen
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA120.015278

Endocannabinoid signaling plays a regulatory role in various (neuro)biological functions. 2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid, and although its canonical biosynthetic pathway involving phosphoinositide-specific phospholipase C and diacylglycerol lipase α is known, alternative pathways remain unsettled. Here, we characterize a noncanonical pathway implicating glycerophosphodiesterase 3 (GDE3, from gene). Human GDE3 expressed in HEK293T cell membranes catalyzed the conversion of lysophosphatidylinositol (LPI) into monoacylglycerol and inositol-1-phosphate. The enzyme was equally active against 1-acyl and 2-acyl LPI. When using 2-acyl LPI, where arachidonic acid is the predominant fatty acid, LC-MS analysis identified 2-AG as the main product of LPI hydrolysis by GDE3. Furthermore, inositol-1-phosphate release into the medium occurred upon addition of LPI to intact cells, suggesting that GDE3 is actually an ecto-lysophospholipase C. In cells expressing G-protein-coupled receptor GPR55, GDE3 abolished 1-acyl LPI-induced signaling. In contrast, upon simultaneous ex-pression of GDE3 and cannabinoid receptor CB2, 2-acyl LPI evoked the same signal as that induced by 2-AG. These data strongly suggest that, in addition to degrading the GPR55 LPI ligand, GDE3 can act as a switch between GPR55 and CB2 signaling. Coincident with a major expression of both GDE3 and CB2 in the spleen, spleens from transgenic mice lacking GDE3 displayed doubling of LPI content compared with WT mice. Decreased production of 2-AG in whole spleen was also observed, supporting the relevance of our findings. These data thus open a new research avenue in the field of endocannabinoid generation and reinforce the view of GPR55 and LPI being genuine actors of the endocannabinoid system.