Effect of Z-IE(Ot-Bu)A-leucinal on Aβ and APPα secretion by stably transfected HEK293 expressing CTF-PS1 and CTF-PS2. Stable transfectants overexpressing CTF-PS1 (CPS1-6 and CPS1-17) and CTF-PS2 (CPS2-1 and CPS2-8) were grown as described in Materials and Methods then APPα secretion was initiated in the absence (−) or presence (+) of Z-IE(Ot-Bu)A-leucinal. APPα was immunoprecipitated after 5 hr by means of 207 antibody and revealed with mAb10D5C (A). Stable transfectants overexpressing wt-βAPP751 (WT) were transiently transfected with CTF-PS1 (ct-1) or CTF-PS2 (ct-2) cDNAs. Secreted total Aβ was obtained after immunoprecipitation with FCA18 and revealed with mAbWO2 as described in Materials and Methods (C). Densitometric analyses of APPα (B) or Aβ (D) [normalized for CTF-PS1/2 (A) or ct-1/2 (C)] secretions are expressed as the percent of control corresponding to secretion obtained in absence of inhibitor. Values are the mean of independent experiments carried out on the indicated independent clones.