ATF4 and Parkinson disease: They observed increased levels of phospho-R-like endoplasmic reticulum kinase (phospho-PERK) and phospho-inositol-requiring kinase 1 α-subunit (phosphor-eIF2α) proteins, as well as 78-kDA glucose-regulated protein (GRP78/BiP), activating transcription factor 4 (ATF4), and the transcription factor CHOP in SNpc from post mortem samples of patients with PD compared with controls [163,164].