Samples were probed with antibodies against pKAβ (C-20; Santa Cruz), GSK3β (Cell Signaling), anti-cdk1/cdc2 (Upstate), cdk5 (J3; Santa Cruz), PCTAIRE 1 (gift of Dr. Julian Gannon and Dr. Tim Hunt) and β-actin (Sigma) according to the dilutions recommended by the providers. Antibodies raised in our laboratory including PCTAIRE 3 antibodies (1D3, 2C7 and 52G6) and tau antibodies (CP9, CP13, PHF1, CP3, PG5 and CP27) were used at a concentration of 1:20.