mature NCT, N: N-glycosylated, NTF: N-terminal fragment, O: O-glycosylated. (TIF) Figure S2 APP-CTF profiles in WT MEF, MEF PS1/22/2 and c - PS1/2 transduced with the SPA4CT construct. WT MEF, MEF PS1/22/2 and c - PS1/2 were transduced with an APP-based substrate corresponding to the 99 C-terminal residues of human APP fused to the APP signal peptide in N- terminus (SPA4CT [36]). Cell proteins were extracted in 1% NP40-HEPES buffer, separated by SDS-PAGE on 12% Tris- Glycine gels and analysed by immunostaining with an antibody targeting the C-terminal part of APP (A8717). (TIF) Figure S3 APH1 isoforms expressed in MEF PS1/22/2. Total RNAs were extracted from presenilin double-knockout MEFs, using standard procedures (Qiagen RNAeasy kit) and were quantified by spectrophotometry. One microgram of total RNAs was reverse transcribed for 1 h at 42uC by using the ImProm-II reverse transcription system (Promega) and oligo-dT primer in a final volume of 20 mL. 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