HSPA5 and Parkinson disease: In order to investigate whether BAP31 mediates the effects of ER stress and apoptosis on PD, we first measured the protein expression of markers of ER stress and apoptosis, including glucose-regulated protein 78 (GRP78), C/EBP-homologous protein (CHOP), Bcl-2-associated X protein (Bax) and B-cell lymphoma-2 (Bcl-2) in vivo and in vitro via Western blotting.