Fig. 5. Knockdown of STIM1 with siRNA does not reduce apoptosis triggered by BIRD-2 in SU-DHL-4 cells.

a Analysis of the cytosolic Ca²⁺ response in mock-transfected SU-DHL-4 cells, or cells transfected with scrambled siRNA or with siRNA against STIM1, using Fura-2 AM. Addition of 10 µM BIRD-2 is indicated by the dotted line. The curves represent the mean ± SEM of three independent experiments. The BIRD-2-provoked cytosolic Ca²⁺ rise is quantified by measuring the peak amplitude (∆ F₃₄₀/F₃₈₀), shown in b, and the time constant τ (s), which is shown in c. d Representative scatter plots from flow cytometry analysis detecting apoptosis in transfected SU-DHL-4 cells stained with Annexin V-FITC and 7-AAD. Cells were treated for 2 h with 10 µM BIRD-2, after which apoptotic cell death was detected by measuring the Annexin V-FITC-positive fraction. e Quantitative analysis of four independent experiments detecting apoptosis in mock-transfected SU-DHL-4 cells or cells transfected with scrambled siRNA or with STIM1 siRNA. Cells were treated for 2 h with 10 µM BIRD-2. In the scatter plots, data are represented as the mean ± SEM of at least three independent experiments. Statistically significant differences were determined with a one-way ANOVA. NS not significant.