P4HB and amyotrophic lateral sclerosis: Independent studies identified two protein disulfide isomerase family members (PDIs), PDI and ERp57 (also known as PDIA3 or GRP58), among the main proteins induced in spinal cord of ALS rodents at different disease stages, suggesting that dysregulation of redox folding in the endoplasmic reticulum (ER) contributes to disease pathogenesis [9–11].