While protein phosphatase 1 (PP1), PP2A, PP2B, PP2C and PP5 have all been implicated in the dephosphorylation of tau, the main regulator of tau phosphorylation is PP2A, which accounts for ~70% of the total tau phosphatase activity in the human brain and its activity is reduced in the AD brain[2, 34, 35]. This evidence concerns the gene PTPA and Alzheimer disease.