APP and Alzheimer disease: The amyloid-β (Aβ) peptide is a major component of plaques in the brain of Alzheimer’s disease patients and is produced through the processing of the amyloid precursor protein (APP) by β- and γ-secretases; Aβ1–40 is the most abundant peptide, and Aβ1–42 is a major component of amyloid plaques [3,4,5,6].