BACE1 and Alzheimer disease: BACE1 (β-site APP cleaving enzyme 1) is a transmembrane aspartic protease that is localized to lipid rafts in human brains (Tun et al., 2002; Cordy et al., 2003; Ehehalt et al., 2003) and is upregulated in AD brains (Fukumoto et al., 2002; Ehehalt et al., 2003; Yang et al., 2003; Holsinger et al., 2006; Ahmed et al., 2010).