Figure 1.

Synaptic APP processing following KCl depolarization. A, Cortical synaptoneurosomes from 10- to 14-d-old TgCRND8 mice were either stimulated by 40 mm KCl with no preincubation or stimulated by 40 mm KCl following a preincubation with 1 μm DAPT (γ-secretase inhibitor). After KCl stimulation with no preincubation, a rapid reduction in C99 and C83 levels was observed. DAPT pretreatment followed by KCl stimulation caused rapid accumulation of C99 (β-CTF) and C83 (α-CTF). Overall, this experiment shows that KCl depolarization coactivates α-, β-, and γ-secretases at the synapse. The representative Western blot images are from the KCl only (the upper bands in the doublets are phosphorylated C83 and C99) and the DAPT + KCl experiments. Control samples were collected from an unstimulated pool at 0 min (ctrl 0′) and 10 min (ctrl 10′). The values were normalized to the baseline (t = 0). n = 6 for each. B, Levels of Aβ₄₀ and Aβ₄₂ in the releasate were measured using ELISA. Both Aβ peptides were released from synaptoneurosomes after KCl depolarization. The values were normalized to the baseline (t = 0). n = 7 for Aβ₄₀; n = 8 for Aβ₄₂. Data are presented as means ± SEM. *p < 0.05; **p < 0.01; ^# p < 0.001; ^## p < 0.0001.