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This article has been peer reviewed. It is the author’s final published version in Cell Reports, Volume 26, Issue 2, January 2019, Pages 330-337.e4.

The published version is available at Copyright © Brailoiu et al.


Sigma-1 receptors (Sig-1Rs) are integral ER membrane proteins. They bind diverse ligands, including psychoactive drugs, and regulate many signaling proteins, including the inositol 1,4,5-trisphosphate receptors (IP3Rs) that release Ca2+ from the ER. The endogenous ligands of Sig-1Rs are unknown. Phospholipase D (PLD) cleaves phosphatidylcholine to choline and phosphatidic acid (PA), with PA assumed to mediate all downstream signaling. We show that choline is also an intracellular messenger. Choline binds to Sig-1Rs, it mimics other Sig-1R agonists by potentiating Ca2+ signals evoked by IP3Rs, and it is deactivated by metabolism. Receptors, by stimulating PLC and PLD, deliver two signals to IP3Rs: IP3 activates IP3Rs, and choline potentiates their activity through Sig-1Rs. Choline is also produced at synapses by degradation of acetylcholine. Choline uptake by transporters activates Sig-1Rs and potentiates Ca2+ signals. We conclude that choline is an endogenous agonist of Sig-1Rs linking extracellular stimuli, and perhaps synaptic activity, to Ca2+ signals. © 2018 The Authors

Sigma-1 receptors respond to diverse stimuli and regulate many signaling proteins. Brailoiu et al. show that choline is an endogenous agonist of Sigma-1 receptors. Choline links receptors and cholinergic synaptic activity, through Sigma-1 receptors, to enhanced Ca2+ release through IP3 receptors. © 2018 The Authors

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