APP and Alzheimer disease: From a pathology perspective, the presence of extracellular plaques, mainly composed of amyloid beta peptide (Aβ), a 39- to 42-aminoacid residue peptide, derived from the processing of amyloid precursor protein (APP), and intraneuronal neurofibrillary tangles, consisting of tau protein aggregates, constitute, important hallmarks of the disease and serve, as a dividing line between AD and other dementias [1–4].