APP and Alzheimer disease: In the terminal stage of AD, the activated astrocytes around Aβ plaques express amyloid precursor protein (APP), γ-secretase, and β-site amyloid precursor protein cleaving enzyme 1 (BACE-1), to increase the level of Aβ (Grolla et al., 2013; Hartlage-Rubsamen et al., 2003).