Abstract: The endoplasmic reticulum (ER) performs the synthesis, posttranslational modification, and proper folding of proteins. A variety of conditions can be ER stress, causing the accumulation of unfolding or misfolding proteins in the ER. Eukaryotic cells have three different mechanisms for dealing with an accumulation of unfolded proteins in the ER known as the unfolded protein response (UPR): transcriptional induction, translational attenuation, and degradation. This paper focuses on the relationship between UPR and the pathogenesis of AD. Our results indicate a new mechanism by which PS1 mutations may affect the sensing of ER stress. Experimental manipulation of IRE1, PERK, or eIF2α phosphorylation or GRP78 expression might allow the development of therapeutic strategies for FAD.