NACHO Engages N-Glycosylation ER Chaperone Pathways for α7 Nicotinic Receptor Assembly.

The alpha 7 nicotinic acetylcholine receptor participates in diverse aspects of brain physiology and disease. Neurons tightly control alpha 7 assembly, which relies upon NACHO, an endoplasmic reticulum (ER)-localized integral membrane protein. By constructing alpha 7 chimeras and mutants, we find that NACHO requires the alpha 7 ectodomain to promote receptor assembly and surface trafficking. Also critical are two amino acids in the alpha 7 second transmembrane domain. NACHO-mediated assembly is independent and separable from that induced by cholinergic ligands or RIC-3 protein, the latter of which acts on the large alpha 7 intracellular loop. Proteomics indicates that NACHO associates with the ER oligosaccharyltransferase machinery and with calnexin. Accordingly, NACHO-mediated effects on alpha 7 assembly and channel function require N-glycosylation and calnexin chaperone activity. These studies identify ER pathways that mediate alpha 7 assembly by NACHO and provide insights into novel pharmacological strategies for these crucial nicotinic receptors.