Figure 8

PrP delays cell death induced by ER stress. (A) inset shows western blot of PrP and β-actin in siRNA transfected cells. Percentage of cell death assessed by pan-caspase FLICA (A) or by chromatin condensation (B) in MCF-7 cells transfected with control (siCtl) or PrP (siPrP) siRNAs for 24 hrs and treated with ER stressors or DMSO (control) during 6 hrs. Cell death was measured 18 hrs after the removal of ER stress. Data represent the mean ± SEM of three (A) or six (B) independent experiments. At least 150 cells were counted per experiment. * Indicates P ≤0.05 between PrP siRNA and control siRNA. (C-D) Percentage of cell death assessed by FLICA staining for active caspases (C) or by chromatin condensation in PrP^+/+ and PrP-/- hippocampal cell lines (D). Data represent the mean ± SEM of four independent experiments. At least 150 cells were counted per experiment. * Indicates P ≤0.05 between PrP+/+ and PrP-/- cells. C Inset: Western blot analysis of PrP with the R155 antibody and β-actin in protein extracts from mouse PrP+/+ and PrP-/- hippocampal cell lines. PrP-/- hippocampal cell lines were treated with 2.5 μg/ml of ER stressors. These concentrations were empirically determined to induce ER stress response without initially inducing strong toxic effects. (E) Relative fluorescence units (RFU) of FLICA activity representing pan-caspase activity in MDA-MB-231 (E) or HS578T (F) cells transfected with siCtl or siPrP.