FIG. 7.
GSK-3αβ and cdk5 activities are unaffected in transgenic mice expressing human mutant APPV717I-CT100 and/or tauV337M. Protein lysates extracted from the forebrain and hindbrain of wild-type mice (WT) and transgenic mice expressing human APPV717I-CT100 alone (CT100), human tauV337M alone (Tau), or both transgenes (COM) at 6 (A) and 12 (B) months of age were analyzed by Western blotting. GSK-3β expression remained unchanged between samples from all mouse models, as did the phosphorylation status of GSK-3αβ at S21/9 (GSK-PS) and Y279/216 (GSK-PY). The antibody to the total form of GSK-3 only recognizes the β isoform. The ratio of p25 to p35 also remained consistent, suggesting that the activity of cdk5 was unaffected by transgene expression. Consistency of protein loading was substantiated by the levels of β-actin (not shown). The chemiluminescence emitted for GSK-3αβ was quantified using the GeneGnome imaging system and normalized to the amount of β-actin in each sample. Values for forebrain and hindbrain samples at 6 (C) and 12 (D) months are expressed as a percentage of the mean WT value ± SEM for three independent samples per group. The WT value was set at 100%. Quantification is shown for the total levels of GSK-3β (open bars) and for GSK-3αβ forms phosphorylated at S21/9 (hatched bars) and Y216/279 (grey bars).