Figure 6. DISC1^D453G disrupts GSK3β signaling.

(A) Western blotting revealed comparable levels of DISC1 protein in whole brain homogenates from wild-type (+/+; n = 10, 5 male and 5 female) and DISC1^D453G (D453G/D453G; n = 10, 5 male and 5 female) mice (left side; mean of three gels). Representative blots of DISC1 and GAPDH loading control for male and female DISC1^D453G mice (right side). (B) The ability of DISC1 to complex with GSK3β was tested by co-immunoprecipitation (co-IP). DISC1^D453G significantly reduced DISC1-GSK3β binding in both male and female DISC1^D453G mice. (C) GSK3β protein levels were comparable between wild-type and DISC1^D453G mice of either sex. (D) Levels of S9 phosphorylated GSK3β (p-S9-GSK3β) normalized to total GSK3β were significantly decreased in whole brain homogenates from both male and female DISC1^D453G mice. (E) β-catenin protein levels were decreased in whole brain homogenates from DISC1^D453G mice of either sex. (F) Representative blots for male (left side) and female (right side) wild-type and DISC1^D453G mice. (G) Schematic model depicting the effects of D453G on GSK3β signaling. Mutation D453G reduces the interaction of DISC1 with GSK3β, and AKT-dependent phospho-inhibition of GSK3β at S9 is decreased. The less inhibited GSK3β phosphorylates more β-catenin, leading to more ubiquitin-mediated degradation of β-catenin, and reducing the cellular level of β-catenin. Red star: D453G mutation; T-shaped arrows: inhibition; magenta circles: phosphate group, size indicating degree of phospho-inhibition; curved broken arrow: ubiquitin-mediated degradation; brown circles: products of β-catenin proteolysis.