MAPK3 and Alzheimer disease: ERK is required for TAU hyperphosphorylation in mice (Le Corre et al, 2006), while ERK1/2 activity, but not total protein levels, was previously found to be elevated in human AD brain (Ferrer et al, 2001) concomitantly with initial TAU deposition, reflecting one of the earliest events in disease pathogenesis (Stygelbout et al, 2014).