MAPK3 and post-traumatic stress disorder: Taken together, all above data suggest that PTSD-like induction downregulates SGK1-related ERK1/2 activity and upregulates AKT/SGK1-related GSK3β activity, finally resulting in tau hyperphosphorylation at Ser202/Thr205 (AT8) and Ser404 but not at Ser199 or Ser396 epitopes in the hippocampus of SPS rats (Figure 5I).