ERN1 and Parkinson disease: It should be noted that the p-PERK and p-IRE1α had colocalization with increased α-synuclein in PD DA neurons (Hoozemans et al., 2007; Heman-Ackah et al., 2017b), revealing that UPR activation is highly associated with the accumulation of misfolded α-synuclein in PD.