Up-regulation of GSK-3β (Jin et al., 2015b), cdk5 (Lee et al., 2000), CK1ε and δ (Kannanayakal et al., 2006), and Dyrk1A (Jin et al., 2015a) and down-regulation of PKAcα and PKAcβ (Liang Z. et al., 2007) have been reported in AD brains. Here, CDK5 is linked to Alzheimer disease.