Figure 5.

Effect of other proteasome inhibitors on SH-SY5Y cells. Cells were treated with MG132 (1 and 10 µM), ALLN (20 and 40 µM) or dimethyl sulphoxide (vehicle; 0.1%) as a solvent. (A) Cell viability assayed 24 h after drug additions by assessing the state of chromatin using Hoechst 33342. Data were normalized to vehicle-treated cells (taken as 100%), and values were reported as the mean ± SEM; they are representative of at least three experiments, each performed in quadruplicate. Statistically significant differences from respective controls: *P < 0.05, **P < 0.01 (one way analysis of variance; Tukey's test). (B) Proteasome inhibitors induced green fluorescent protein (GFP)–Bax translocation. SH-SY5Y cells were transfected with GFP–Bax, incubated for 24 h to allow for sufficient GFP–Bax expression. After 12 h of exposure to proteasome inhibitors, the cells were fixed in 4% p-formaldehyde, and the number of cells with punctate Bax distribution was counted and expressed as a percentage of the total number of cells expressing GFP–Bax protein. Results are presented as the mean ± SEM; they are representative of at least four experiments, each performed in triplicate. Statistically significant difference from respective controls: *P < 0.05; **P < 0.01; ***P < 0.001 versus control conditions. Significance was determined by Student's t-test.