FIGURE 4.

p120ctn enhances E-cadherin but attenuates APP processing catalyzed by γ-secretase. A, membranes prepared from SW48 cell cultures transduced with either vector or p120ctn were prepared and used in in vitro γ-secretase assay as described above in the presence or absence of γ-secretase inhibitor L665,458. The upper panel was probed with anti-E-cadherin antibodies and the two lower panels with anti-APP R1 antibodies. The detected products are indicated at the right of the figure. APP/L, full-length APP. Expression of exogenous p120ctn increases the γ-secretase products of E-cadherin but decreases AICD, a γ-secretase product of APP. B, shown are the results from in vitro AICD assay in SW48 cells. AICD was detected in WBs with C-terminal anti-APP antibodies, and signals were quantified by densitometry using ImageJ software. In vitro production of AICD was estimated as the difference between the samples at 2 and 0 h. The effect of p120 on the in vitro production of AICD is statistically significant. Amounts of AICD are indicated in arbitrary units based on the subtracted value of the signal intensity at 0 and 2 h in both mock and p120ctn-transduced cells. The data represent the mean ± S.D. of five experiments. **, p < 0.005. C, secreted Aβ40 and Aβ42 from mock- and p120ctn-expressing SW48 cell cultures were analyzed by an Aβ sandwich enzyme-linked immunosorbent assay. The data represent the mean ± S.E. of five experiments. *, p < 0.05.