Fig. 2

PS1 γ-secretase has higher processivity than PS2 γ-secretase on APP. a IP-MS of Aβ peptide in cell culture media. APPsw was transiently transfected into WT, PS1, PS2, and DKO HEK cells, and secreted Aβ peptides were immunoprecipitated with Ab5 antibody. b IP-MS of Aβ peptide in cell-free assay using WT, PS1, PS2, and DKO membranes with cC100sub as substrate. c IP-MS of CTF in cell-free assay. CTF was immunoprecipitated with anti-FLAG M2 antibody. d, e Summary results from mass spectrometry analysis presented in a, b. Histogram plots of the ratio of Aβ38 to Aβ40 in cell-based and cell-free assay (n = 3, one-way ANOVA, Tukey’s multiple comparisons test using Prism GraphPad version 8 software). f Transient transfection of PS1 and PS2 DNA into DKO cells shows similar processivity difference of PS1 and PS2. 0.5 μg PS1, PS2, or PS1+PS2 were co-transfected with 2 μg APPsw into DKO cells. IP-MS of Aβ peptide in conditioned media with Ab5 antibody. All experiments were repeated 3 times. Mass spectra from PS1-transfected cell show unidentified peaks (*)