PTPA and Alzheimer disease: For example, we found that Ppp2ca mRNA, which encodes a catalytic subunit of PP2A down-regulated in AD (log fold change = −0.16, P = 2.49 × 10−25) (4), was likewise reduced by CREB3L2-ATF4 activation in neurons (log fold change = −0.15, P = 0.016; fig.