APP and Alzheimer disease: A number of protein kinases responsible for phosphorylating APP at the T668-P motif are abnormally elevated in the AD brain, such as GSK3β, SAPK1b/JNK3, Cdc2, and Cdk5 (Zhou et al., 2000; Lee et al., 2003, 2011b; Lu and Zhou, 2007; Ma et al., 2012a).