APP and Alzheimer disease: Aβ is derived from amyloidogenic cleavage of membrane bound amyloid precursor protein (APP) by β- and γ-secretase.3 Amyloidogenic processing of the APP leads to the production of Aβ peptides of different length, of which the Aβ1–40 is the major species and the Aβ1–42 is the most fibrillogenic and predominant component in AD plaques.4