PTPA and Alzheimer disease: Indeed, several abnormalities of PP2A have been reported in AD, including decreased mRNA and protein levels of the PP2A subunit C, decreased protein levels of the PP2A subunits A and B (B55α, B55γ, B56ε), reduced PP2A C methylation at Leu309 by leucine carboxyl methyltransferase 1 (LCMT1), down-regulation of expression of LCMT1, increased cleavage of PP2A regulator α4, and overexpression of SET and ANP32A [117,118].