However, two other pathways of the UPR (i.e., ATF6 and IRE1α) are not activated in APP/PS1 or prion-diseased mice (Ma et al., 2013; Moreno et al., 2013), and it currently remains unclear whether PERK overactivation found in AD animal models may be part of the UPR signaling (Endres and Reinhardt, 2013). Here, APP is linked to Alzheimer disease.