XPNPEP2 and Alzheimer disease: Disruption of PP2 A/Bα-tau protein interactions likely contribute to tau deregulation in AD deregulation of PP2 A methylation with down-regulation of PP2 A/Bα, enhanced phosphorylation of tau and amyloid precursor protein, tau mislocalization, microtubule destabilization and neuritic defects (Sontag and Sontag 2014).