Deficiency in endocannabinoid synthase DAGLB contributes to Parkinson’s disease and dopaminergic neuron dysfunction

Abstract

2-arachidonoyl-glycerol (2-AG), the most abundant endocannabinoid (eCB) in the brain, regulates diverse neural functions. However, whether 2-AG deficiency contributes to Parkinson's disease (PD) and nigral dopaminergic neurons (DANs) dysfunction is unclear. Diacylglycerol lipase A and B (DAGLA and DAGLB) mediate the biosynthesis of 2-AG. Using homozygosity mapping and whole-exome sequencing, we linked multiple homozygous loss-of-function mutations in DAGLB to a form of early-onset autosomal recessive PD. We then used RNA sequencing and fiber photometry with genetically encoded eCB sensors to demonstrate that DAGLB is the main 2-AG synthase in nigral DANs. Genetic knockdown of Daglb by CRISPR/Cas9 in mouse nigral DANs substantially reduces 2-AG levels in the substantia nigra (SN). The SN 2-AG levels are markedly correlated with the vigor of movement during the acquisition of motor skills, while Daglb-deficiency impairs motor learning. Conversely, pharmacological enhancement of 2-AG levels increases nigral DAN activity and dopamine release and improves motor learning. Together, we demonstrate that DAGLB-deficiency contributes to the etiopathogenesis of PD, reveal the importance of DAGLB-mediated 2-AG biosynthesis in nigral DANs in regulating neural activity and dopamine release, and provide preclinical evidence for the beneficial effects of 2-AG augmentation in PD treatment.

Pharmacological characterization of the endocannabinoid sensor GRABeCB2.0

“…17 Several laboratories reported that GRAB eCB2.0 signal increases within seconds when exogenously applying 2-AG or AEA to cells in culture, as well as when endogenously stimulating eCB production in cells in culture, mouse brain slices and behaving animals. 15;18–20…”

ABHD6 selectively controls metabotropic-dependent increases in 2-AG production

“…This technology leverages the high binding of endogenous ligands to specific receptors, which stabilizes a conformation to elicit fluorescence of a circularly permutated-green fluorescent protein (cpGFP) introduced in the third intracellular loop of the G protein-coupled receptors (GPCR) 9 . For example, GRAB eCB2.0 sensor detects changes in 2-AG levels with a sub second temporal resolution and its activation is described in mouse neurons in primary culture and brain slices, as well as in vivo during behavior [10][11][12][13] . Thus, the spatiotemporal properties of such sensors provide an opportunity to study the molecular mechanism of eCB signaling at the cellular level.…”