Influence of CTF-PS1 and CTF-PS2 on Aβ secretion. Stable transfectants expressing wt-βAPP751 (WT) or empty pcDNA3 (Mock) are transiently transfected with empty pcDNA3 (m) or coding for CTF-PS1 (ct-1) or CTF-PS2 (ct-2) fragments (A). Secreted Aβ was immunoprecipitated with FCA18 antibody then detected with mAbWO2 as described in Materials and Methods. Bars in B correspond to densitometric analysis of secreted Aβ (normalized for et-1 and ct-2 expression) and are expressed as the percent of control corresponding to Mock and WT cells transiently transfected with empty pcDNA (m). Values are the mean ± SEM of 3 independent experiments. In C, stably transfected HEK293 cells overexpressing CTF-PS1 (CPS 1–6), CTF-PS2 (CPS2-8), or with empty pcDNA3 (Mock) were examined for Aβ secretion after transient transfection with wt-βAPP751 (wt) or empty pcDNA3 (m). Total Aβ was obtained after immunoprecipitation with FCA18 and revelation with mAbW02 as described in Materials and Methods. Bars in D correspond to densitometric analysis of Aβ expressed as the percent of control corresponding to stable Mock cells transiently transfected with pcDNA3 (m) or βAPP751 (wt).