MAPK3 and Alzheimer disease: In summary, we have found in the present study that PTSD-like induction leads to tau hyperphosphorylation at specific AD-relevant sites in the hippocampus of SPS rats, which as a result of incongruous action between AKT-related GSK-3β activation and SGK1-related ERK1/2 inactivation resulted in the phosphorylation of tau at Ser202/Thr205 and Ser404 but not at Ser199 or Ser396.