Inhibition of store-operated calcium channels by N-arachidonoyl glycine (NAGly): no evidence for the involvement of lipid-sensing G protein coupled receptors

Abstract

n-arachidonoyl glycine (nAGly) is an endogenous lipid deriving from the endocannabinoid anandamide (AEA). Identified as a ligand of several G-protein coupled receptors (GPCRs), it can however exert biological responses independently of GPCRs. NAGly was recently shown to depress store-operated ca 2+ entry (SOCE) but its mechanism of action remains elusive. The major aim of this study was to gain a better knowledge on the NAGly-dependent impairment of SOCE in neurons of the central nervous system (CNS) from mice. First, we examined the expression of genes encoding for putative lipid sensing GPCRs using transcriptomic data publicly available. This analysis showed that the most abundant GPCRs transcripts present in the cerebral cortices of embryonic brains were coding for lysophosphatidic acid (LPA) and sphingosine-1 phosphate (S1P) receptors. Next, the presence of functional receptors was assessed with live-cell calcium imaging experiments. In primary cortical cells S1P and LPA mobilize ca 2+ from internal stores via a mechanism sensitive to the S1P and LPA receptor antagonists Ex26, H2L5186303, or Ki16425. However, none of these compounds prevented or attenuated the NAGlydependent impairment of Soce. We found no evidence for the requirement of lipid sensing GpcRs in this inhibitory process, indicating that NAGly is an endogenous modulator interfering with the core machinery of Soce. Moreover, these data also raise the intriguing possibility that the depression of SOCE could play a role in the central effects of NAGly.

Receptor-Dependent and Independent Regulation of Voltage-Gated Ca2+ Channels and Ca2+-Permeable Channels by Endocannabinoids in the Brain

“…In addition, NAGly was able to release Ca 2+ from the ER potentiating the passive calcium leak. Similar results were obtained in another study on mice primary cortical cells confirming that NAGly can serve as an endogenous modulator interfering with the core machinery of SOCE [ 163 ].…”

Transcriptomic Profiling of Ca2+ Transport Systems during the Formation of the Cerebral Cortex in Mice

“…These experiments were conducted with the Ca 2+ probe Fluo4 as previously described [ 13 , 16 , 17 ]. Briefly, cells were loaded with 5 µM Fluo4/AM for 25 min, washed, and kept for another 5–10 min in a standard recording saline solution containing (in mM) 150 NaCl, 5 KCl, 1 MgCl 2 , 2 CaCl 2 , 5.5 glucose, and 10 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) (pH 7.4).…”