Abstract
The endocannabinoid system (ECS) is considered to be an endogenous protective system in various neurodegenerative diseases. Niemann-Pick type C (NPC) is a neurodegenerative disease in which the role of the ECS has not been studied yet. Most of the endocannabinoid enzymes are serine hydrolases, which can be studied using activity-based protein profiling (ABPP). Here, we report the serine hydrolase activity in brain proteomes of a NPC mouse model as measured by ABPP. Two ABPP methods are used: a gel-based method and a chemical proteomics method. The activities of the following endocannabinoid enzymes were quantified: diacylglycerol lipase (DAGL) α, α/β-hydrolase domain-containing protein 4, α/β-hydrolase domain-containing protein 6, α/β-hydrolase domain-containing protein 12, fatty acid amide hydrolase, and monoacylglycerol lipase. Using the gel-based method, two bands were observed for DAGL α. Only the upper band corresponding to this enzyme was significantly decreased in the NPC mouse model. Chemical proteomics showed that three lysosomal serine hydrolase activities (retinoid-inducible serine carboxypeptidase, cathepsin A, and palmitoyl-protein thioesterase 1) were increased in Niemann-Pick C1 protein knockout mouse brain compared to wild-type brain, whereas no difference in endocannabinoid hydrolase activity was observed. We conclude that these targets might be interesting therapeutic targets for future validation studies.
Highlights
The endocannabinoid system (ECS) consists of the cannabinoid type 1 and 2 receptors (CB1R and CB2R) and their endogenous ligands: the endocannabinoids
The fluorescence intensity of the bands corresponding to DAGLα (∼120 kDa), ABHD12 (∼50 kDa), ABHD6 (∼35 kDa), and Fatty acid amide hydrolase (FAAH) (∼60 kDa) were quantified to determine the relative enzyme activity between knockout and wildtype (Figure 2B)
We used activity-based protein profiling (ABPP) to quantify the activity of the endocannabinoid hydrolases FAAH, ABHD6, ABHD12, ABHD4, and monoacylglycerol lipase (MAGL) in Niemann-Pick C1 protein (NPC1) knockout mice and found that their activity is not affected in wild-type vs. NPC1 knockout mice
Summary
The endocannabinoid system (ECS) consists of the cannabinoid type 1 and 2 receptors (CB1R and CB2R) and their endogenous ligands: the endocannabinoids. The enzymes responsible for endocannabinoid biosynthesis and degradation are Abbreviations: ABHD, α/β-hydrolase domain-containing protein; ABPP, activity-based protein profiling; AEA, anandamide; 2-AG, 2-arachidonoylglycerol; CBxR, cannabinoid type x receptor; CTSA, cathepsin A; DAGL, diacylglycerol lipase; ECS, endocannabinoid system; FAAH, fatty acid amide hydrolase; FP, fluorophosphonate; GBA2, non-lysosomal glucosylceramidase; MAGL, monoacylglycerol lipase; NAPE, N-acylphospatidylethanolamine; NPC, Niemann-Pick type C; PLA2G4E, phospholipase A2 group 4E; PLD, phospholipase D; PPT1, palmitoyl-protein thioesterase 1; SCPEP1, retinoid-inducible serine carboxypeptidase; SDS-PAGE, sodium dodecyl sulfate polyacrylamide gel electrophoresis; THL, tetrahydrolipstatin. Frontiers in Neuroscience | www.frontiersin.org van Rooden et al. Chemical Proteomics of NPC Mouse part of the ECS, with most endocannabinoid degrading enzymes belonging to the serine hydrolase family (Figure 1; Blankman and Cravatt, 2013). Fatty acid amide hydrolase (FAAH) terminates AEA signaling by hydrolysis of its amide bond
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