HSPA5 and tauopathy: A recent study of late-stage AD, PiD, and PSP found no significant difference in XBP-1s, phosphorylated eIF2α, BiP, or CCAAT-enhancer-binding-protein homologous protein (CHOP) compared to non-demented controls29, further supporting the notion that UPRER activation is involved in the early stages of tauopathy.