Molecular chaperone which mediates the proper assembly and functional expression of the nicotinic acetylcholine receptors (nAChRs) throughout the brain (By similarity). Essential for the proper folding, assembly, function and surface trafficking of alpha-7 (CHRNA7), alpha-4-beta-2, alpha-3-beta-2 and alpha-3-beta-4 receptors (By similarity). Shedding may lead to a soluble peptide. Belongs to the DoxX family.