Decreased insulin-induced activation of the insulin receptor, Akt and GSK-3β in fibroblasts harboring the M146V Psen1 FAD mutation. In panel A, human wild type Psen1 (HuPS1Wt) or M146V FAD mutant cell lines were serum starved overnight and then stimulated with insulin for the indicated times. Western blotting for the phosphorylated IR receptor β (Tyr 1150/1151) or total IR is shown in experiments run in duplicate. The pro-insulin receptor and processed IR are indicated. In panel B, duplicate experiments are shown following Western blotting for p-Akt (Ser473) and total Akt. p-Akt panels are shown at two different exposures. Lower panel shows the blot reprobed for β-tubulin as a loading control. In panel C, the extracts were blotted and probed for p-GSK-3β (Ser9) and total GSK-3β. In panels D, E and F the relative increase in p-IR/total IR (D), p-Akt/total Akt (E) and p-GSK-3β/total GSK-3β (F) are shown for the experiments in A-C.