HSPA5 and Parkinson disease: Baek et al. (2019) found that GRP78 mRNA levels are upregulated, but they also showed that the protein levels of GRP78 are decreased in several brain regions, including the cingulate gyrus in PD patients. Recently, similar findings suggested that both GRP78 and ATF4 protein levels are decreased in the SNpc in PD patients (Esteves and Cardoso, 2020).