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

Abstract

Endocannaboid signaling plays a regulatory role in various (neuro)biological functions. 2-Arachidonoyglycerol (2-AG) is the most abundant endocannabinoid, and while its canonical biosynthetic pathway involving phosphoinositide-specific phospholipase C and diacylglycerol lipase α is known, alternative pathways remain unsettled. Here, we characterize a non-canonical pathway implicating glycerophosphodiesterase 3 (GDE3, from GDPD2 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 expression of GDE3 and cannabinoid receptor CB2, 2-acyl-LPI evoked the same signal as that induced by 2-AG. These data strongly suggest that, beside simply 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 spleen, spleens from transgenic mice lacking GDE3 displayed doubling of LPI content, compared to wild type mice. Decreased production of 2-AG in whole spleen was also observed, supporting the in vivo relevance of our findings. These data thus open a new research avenue in the field of endocannabinoid generation and reinforce the view of GPR55/LPI being genuine actors of endocannabinoid system.

Tiki proteins are glycosylphosphatidylinositol‐anchored proteases

“…In addition to PI-PLC, animal cells also express a family of GPI-specific glycerophosphodiesterases (GEDs or GDPDs) composed of GDE2, GDE3 and GDE6, which are membrane proteins with six transmembrane domains and a large extracellular catalytic domain [24,25]. GDEs play important roles in development and diseases by specifically shedding certain GPI-APs [24,[26][27][28][29]. To examine whether TIKI can be regulated by GDEs, TIKI1 or TIKI2 was expressed alone or together with each of the three GDEs in HEK293T cells.…”

Metabolic Consequences of Gestational Cannabinoid Exposure

“…There are data that suggest GPR55s association with the eCB system, as it can heterodimerize with CB2 [186]. In addition, glycerophosphodiesterase 3 can metabolize GPR55 ligand, arachidonoyl lysophosphatidylinositol (LPI), into 2-AG and also act as a signaling switch between GPR55 and CB2, thereby linking GRP55 to canonical cannabinoid receptors [187,188]. Moreover, neurological studies indicate that exogenous cannabinoids (i.e., CBD) also act on other noncanonical cannabinoid-sensitive receptors, such as transient receptor potential vanilloid 1 and opioid receptor µ and δ [189], that may be of interest in peripheral tissues.…”

An independent regulator of global release pathways in astrocytes generates a subtype of extracellular vesicles required for postsynaptic function

“…Cleavage of select GPI–anchored protein (GPI-AP) substrates by GDE3 inhibits cellular proliferation cells autonomously in OPCs and cancer cells ( 13 , 14 ). GDE3 can also metabolize lysophosphatidylinositol (LPI) lipids which may modulate endocannabinoid signaling ( 15 , 16 ). In addition to these functions, GDE3 was recently found to increase the release of the GPI-AP CNTFRα (ciliary neurotrophic factor receptor subunit alpha) in EVs through mechanisms independent of its enzymatic function ( 13 ); however, broader roles for GDE3 in EV biology have not been tested.…”