ATP2A1 and Alzheimer disease: To study ER stress, we analyzed the expression of important ER-related genes like Ryr3, IP3r, Psen1, Serca1, Perk, Ire1a, Atf6, Gq, and Plcn1. Our analysis showed that ryanodine receptor 3 and inositol 3 phosphate receptor, which are calcium regulatory receptors, are upregulated in AD brain samples.