APP and Alzheimer disease: Aβ peptides are derived from the sequential proteolytic processing of the amyloid precursor protein (APP) by β‐secretase (β‐site APP cleaving enzyme 1, BACE1) and γ‐secretase consisting of three major components: presenilin 1 (PS1), nicastrin, and Pen‐2, with this cleavage step contributing heavily to AD pathology (O'Brien & Wong, 2011).