Secreted Aβ40 and Aβ42(43) from cells expressing wild-type or N141I mutant PS2 genes. (A) Levels of Aβx-40, Aβx-42(43), Aβ1–40, and Aβ1–42(43) secreted from COS-1 cells doubly transfected with human βAPP and PS2 genes quantitated by two-site ELISAs. Mean values ± SE in three independent experiments are shown. Combinations of the transfected cDNAs are indicated below the columns: PS2, wild-type PS2; PS2N141I, N141I mutant PS2; APP, wild-type human βAPP695; APPNL, 595/596 (KM-NL) mutant human βAPP695; C100, C-terminal fragment of human βAPP. (B) Levels of Aβx-40 and Aβx-42(43) secreted from N2a cells stably transfected with PS2 cDNAs. Mean values ± SE (n = 4) from three independent cell lines (PS2.a–c transfected with wild-type PS2 and PS2N141I.a–c with N141I mutant PS2 cDNAs) are shown together with those from two nontransfected cell lines (Null.a and b) and cells transfected with empty vector (Vector.a and b).