MAPT and Alzheimer disease: GSK‐3β is a key kinase that plays a crucial role in AD‐like tau hyperphosphorylation.51, 52 GSK‐3β activation or conditionally overexpressed GSK‐3β has been previously reported to cause spatial memory deficits in animals and inhibiting GSK‐3β could revise AD‐like cognitive deficit.43, 53, 54 An in vitro study also shows that GSK‐3β is activated during ER stress.38 However, it is still not understood whether and how GSK‐3β plays an in vivo role in ER stress‐induced tau phosphorylation and cognitive alterations.