ERN1 and Parkinson disease: The UPR activation markers, including phosphorylation of PERK, eIF2α, and IRE1α, are observed in neuromelanin-containing DA neurons in the postmortem SNpc of PD patients rather than age-matched controls (Hoozemans et al., 2007; Hoozemans et al., 2012; Heman-Ackah et al., 2017).