Nuclear diacylglycerol lipase‐α in rat brain cortical neurons: evidence of 2‐arachidonoylglycerol production in concert with phospholipase C‐β activity

In this report, we describe the localization of diacylglycerol lipase‐α (DAGLα) in nuclei from adult cortical neurons, as assessed by double‐immunofluorescence staining of rat brain cortical sections and purified intact nuclei and by western blot analysis of subnuclear fractions. Double‐labeling assays using the anti‐DAGLα antibody and NeuN combined with Hoechst staining showed that only nuclei of neuronal origin were DAGLα positive. At high resolution, DAGLα‐signal displayed a punctate pattern in nuclear subdomains poor in Hoechst's chromatin and lamin B1 staining. In contrast, SC‐35‐ and NeuN‐signals (markers of the nuclear speckles) showed a high overlap with DAGLα within specific subdomains of the nuclear matrix. Among the members of the phospholipase C‐β (PLCβ) family, PLCβ1, PLCβ2, and PLCβ4 exhibited the same distribution with respect to chromatin, lamin B1, SC‐35, and NeuN as that described for DAGLα. Furthermore, by quantifying the basal levels of 2‐arachidonoylglycerol (2‐AG) by liquid chromatography and mass spectrometry (LC‐MS), and by characterizing the pharmacology of its accumulation, we describe the presence of a mechanism for 2‐AG production, and its PLCβ/DAGLα‐dependent biosynthesis in isolated nuclei. These results extend our knowledge about subcellular distribution of neuronal DAGLα, providing biochemical grounds to hypothesize a role for 2‐AG locally produced within the neuronal nucleus. We report that phosphatidylinositol‐phospholipase C (PtdIns‐PLC) and diacylglycerol lipase (DAGL) activities are co‐compartmentalized in isolated adult cortical neuronal nuclei, leading to a nuclear‐localized production of the endocannabinoid 2‐AG. Our results provide biochemical grounds to hypothesize a role for 2‐AG locally produced within the neuronal nucleus. 2‐AG, 2‐arachidonoylglycerol; AA, arachidonic acid; ABHD6, α‐β‐hydrolase domain‐6; COX‐2, cyclooxygenase‐2; DAGK, diacylglycerol kinase; DAGs, diacylglycerols; LPP, lipid phosphate phosphatase; MAGL, monoacylglycerol lipase; NAM, N‐arachidonoylmaleimide; PA, phosphatidic acid; PGG2‐G, prostaglandin G2‐glycerol; PLD, phospholipase D; PtdCho, phosphatidylcholine; PtdInsP2, phosphatidylinositol‐4,5‐bisphosphate; THL, tetrahydrolipstatin. We report that phosphatidylinositol‐phospholipase C (PtdIns‐PLC) and diacylglycerol lipase (DAGL) activities are co‐compartmentalized in isolated adult cortical neuronal nuclei, leading to a nuclear‐localized production of the endocannabinoid 2‐AG. Our results pr