In agreement with that notion, we found the levels of phosphorylation of both PERK at Thr980 and eIF2α at Ser51 markedly increased in the cortex of the 12-months old 3xTg-AD mice, whereas the protein levels of other components of the UPR analyzed such as BIP, PDI, IRE1α or CHOP remained unchanged. Here, ERN1 is linked to Alzheimer disease.