Protein disulfide isomerase which associates with the unc-29 subunit of levamisole-sensitive nicotinic acetylcholine receptors (L-nAChR) to promote L-nAChR assembly in the endoplasmic reticulum at neuromuscular junctions. Promotes L-nAChR assembly in the endoplasmic reticulum at neuromuscular junctions. Catalyzes the rearrangement of -S-S- bonds in proteins. Interacts with unc-29. Ends with a KDEL sequence, which is an endoplasmic reticulum retention signal. Isoforms a: Widely expressed in tissues including body wall muscles, neurons, pharynx, hypodermis, seam cells, intestine and gonad (PubMed:30407909). Isoform b: Widely expressed in tissues including body wall muscles, neurons, pharynx, hypodermis, seam cells, intestine and gonad (PubMed:30407909). Viable, with no defects in coordination (PubMed:30407909). Decreased number of synaptic nicotinic acetylcholine receptors (nAChRs) at neuromuscular junctions (PubMed:30407909). Isoform a: Deletion leads to reduced sensitivity to the nAChR agonist levamisole (PubMed:30407909). Isoform b: Deletion leads to sensitivity to levamisole as in wild-type (PubMed:30407909). Belongs to the CRELD family.