Grp78 (also known as HSPA5) is important for endoplasmic reticulum (ER) protein folding; it was found to play a neuroprotective role in a rat model of Parkinson disease and was also identified as a new binding partner of spartin, mutations in which can cause SPG20 (Gorbatyuk et al., 2012; Milewska et al., 2009). This evidence concerns the gene HSPA5 and Parkinson disease.