Protein disulfide isomerase (By similarity). Promotes the localization of acetylcholine receptors (AChRs) to the plasma membrane (By similarity). Catalyzes the rearrangement of -S-S- bonds in proteins. Additional isoforms seem to exist. Highly expressed in fetal lung, liver, kidney, adult heart, brain and skeletal muscle. Weakly expressed in placenta, fetal brain, and adult lung, liver, kidney and pancreas. Up-regulated by inducers of the unfolded protein response (UPR), including tunicamycin and thapsigargin. Disease susceptibility is associated with variants affecting the gene represented in this entry. Belongs to the CRELD family.