Figure 2

Effect of Aβ42/40 ratio on PS1 conformation. (A) FLIM analysis of the PS1 conformation in primary neurons pretreated for 2 h with the mixtures of Aβ42 and Aβ40 peptides at (A) the varied ratios at the 1 µmol/L total Aβ concentration or (B) the varied ratios (1:9 or 4:6) at the 1 µmol/L total Aβ concentration or different absolute amounts of Aβ42 (0.1 µmol/L or 0.4 µmol/L). The graphs present the increase in FRET efficiency, corresponding to “closed” PS1 conformation, in neurons treated with Aβ42 to Aβ40 at the relatively high ratios. (A) n = 73 (vehicle), n = 77 (1:9), n = 74 (3:7), n = 157 (4:6), n = 152 (10:0), (B) n = 50 (vehicle), n = 50 (1:9), n = 49 (4:6), n = 51 (1:0), n = 50 (4:0), n = total number of neurons analyzed from three independent experiments, mean ± SEM; two-tailed unpaired Student t test. The data are normalized to the values recorded in neurons pre-treated with Aβ42 and Aβ40 peptides at the 1 to 9 ratio. The images present color-coded lifetime of the donor fluorophore. The red pixels correspond to the shorter donor fluorophore lifetimes, indicative of higher FRET efficiency (relative proximity) between the fluorescently labeled PS1 domains. The scale bar corresponds to 10 µm. Aβ — amyloid β; PS1 — presenilin 1; FRET — Förster resonance energy transfer.