EIF2AK3 and Parkinson disease: As ER stress markers, the phosphorylated pancreatic ER kinase (p-PERK) and phosphorylated eukaryotic initiation factor 2alpha (p-eIF2alpha) have been detected in the substantia nigra of PD patients, suggesting that the UPR’s activation is closely related to the accumulation of alpha-synuclein aggregates [26].