PTPA and Alzheimer disease: Knock-down of PP2A catalytic subunit (Kins et al., 2001) or PP2A B’δ (or PPP2R5D) regulatory subunit (Louis et al., 2011), and expression of the methylation-site L309A C subunit mutant (Schild et al., 2006) all induce AD-like tau phosphorylation in transgenic mice.