Discovered during the 1980s as precursor protein of A-beta (Aβ)—the main constituent of senile plaques—much effort has been made to understand the pathophysiology of Alzheimer’s disease (AD) and the physiological function of APP (Glenner and Wong, 1984; Kang et al., 1987). This evidence concerns the gene APP and early-onset autosomal dominant Alzheimer disease.