MAPT and Alzheimer disease: PKA is an important kinase that phosphorylates multiple sites of the tau protein, including serine 214, 396, and 356, alone or by sequential phosphorylation via cooperation with other kinases, such as GSK3β or CDK5, in the progression of AD (Jensen et al., 1999; Ksiezak-Reding et al., 2003; KyoungPyo et al., 2004; Wang et al., 2007).