Functional Alpha 6 Beta 4 Acetylcholine Receptor Expression Enables Pharmacological Testing Of Nicotinic Agonists With Analgesic Properties

The alpha 6 beta 4 nicotinic acetylcholine receptor (nAChR) is enriched in dorsal root ganglia neurons and is an attractive non-opioid therapeutic target for pain. However, difficulty expressing human alpha 6 beta 4 receptors in recombinant systems has precluded drug discovery. Here, genome-wide screening identified accessory proteins that enable reconstitution of human alpha 6 beta 4 nAChRs. BARP, an auxiliary subunit of voltage-dependent calcium channels, promoted alpha 6 beta 4 surface expression while IRE1 alpha, an unfolded protein response sensor, enhanced alpha 6 beta 4 receptor assembly. Effects on alpha 6 beta 4 involve BARP's N-terminal region and IRE1 alpha's splicing of XBP1 mRNA. Furthermore, clinical efficacy of nicotinic agents in relieving neuropathic pain best correlated with their activity on alpha 6 beta 4. Finally, BARP-knockout, but not NACHO-knockout mice lacked nicotine-induced antiallodynia, highlighting the functional importance of alpha 6 beta 4 in pain. These results identify roles for IRE1 alpha and BARP in neurotransmitter receptor assembly and unlock drug discovery for the previously elusive alpha 6 beta 4 receptor.