Fig. 2
PSEN2 mutations significantly alter GSEC processivity, mirroring PSEN1 pathogenic mechanisms. A Schematic representation of PSEN2 primary structure highlighting residues affected by selected mutations studied in this report. Color-coding of mutations: blue (not classified/unclear significance), green (benign), red (pathogenic), orange (likely pathogenic). Mutations selected for this study are shown. Pathogenicity information taken from the Alzforum database. B Aβ profiles (showing the relative abundance of Aβ37, Aβ38, Aβ40, Aβ42, and Aβ43 peptides relative to total Aβ) generated by PSEN1 WT-, PSEN2 WT-, or mutant PSEN2-containing GSECs. Benign mutations (controls) are displayed on grey background. Mutations are classified based on Alzforum database in: pathogenic, likely pathogenic, uncertain significance/not classified or benign. Data presented as mean ± SD, N ≥ 3 independent experiments. C Efficiency of 4 th enzymatic GSEC turnover of APPC99 (estimate of GSEC processivity) quantified by the Aβ(37 + 38 + 40)/(42 + 43) ratio; data are normalised to PSEN2 WT (in bold and striped filled pattern). PSEN1 WT (in blue), PSEN2 WT and analysed variants in purple, benign variants (control) in light grey. Data presented as mean ± SD, N ≥ 3 independent experiments. Statistical significance determined by one-way ANOVA and Dunnett's post-hoc test compared to PSEN2 WT (p < 0.05); ****p < 0.0001, (F(DFn, DFd): F (29, 173) = 305.1). D Aβ40/42 ratio data normalised to PSEN2 WT (in bold and striped filled pattern). PSEN1 WT (in blue), PSEN2 WT and analysed variants in purple, benign variants (control) in light grey. Data presented as mean ± SD, N ≥ 3 independent experiments. Statistical significance determined by one-way ANOVA followed by Dunnett's post-hoc test compared to PSEN2 WT (p < 0.05); ****p < 0.0001, (F(DFn, DFd): F (29,173) = 123.1). E Correlation analysis between GSEC processivity (normalised to PSEN2 WT) and AAO. This analysis includes all PSEN2 variants showing significant differences compared to PSEN2 WT in the Aβ(37 + 38 + 40)/(42 + 43) ratio (panel C). Significant correlation found (equation: Y = 1.5*X – 67, R2 = 0.52). 95% confidence interval shown as light blue area. Error bars represent SD for the processivity ratio (x-axis) and AAO (y-axis). F Correlation analysis between the Aβ40/42 ratio (normalised to PSEN2 WT) and AAO. This analysis includes all PSEN2 variants showing significant differences compared to PSEN2 WT in the Aβ40/42 ratio (panel D). Significant correlation found (equation: Y = 1.4*X – 62, R2 = 0.50). 95% confidence interval shown as light blue area. Error bars represent SD for Aβ ratio (x-axis) and AAO (y-axis)