Bid is dispensable for apoptosis triggered by the kinase inhibitor Staurosporine.

Control and HeLa Bid kd cells were pre-incubated with the pan-caspase inhibitor zVAD-fmk (100 µM) for 1 h before treatment with the indicated concentrations of Staurosporine for the indicated times. A) Caspase-3 like activity was measured by cleavage of the fluorogenic substrate Ac-DEVD-AMC. Data are means+/−SD from n = 3 separate experiments. n.s. = not significant versus control (Ctrl). B) Cells were treated as indicated and lysates were subjected to Western blotting with a polyclonal caspase-3, a monoclonal Poly-ADP-Ribose Polymerase (PARP) antibody and a monoclonal α-tubulin antibody. C, D) The small molecule Bid inhibitor BI6C9 mimics the effects of the knockdown of Bid in HeLa cells. Parental HeLa cells were pre-incubated with the indicated concentrations of BI6C9 for 16 h prior to treatment with an agonistic Fas antibody, Staurosporine (STS) or vehicle, for 6 h. Apoptosis was assessed by flow cytometric evaluation of Annexin-V FITC conjugated binding to phosphatidylserine in non-permeabilized cells. Data are means+/−SD from n = 3 separate experiments. ∗ p<0.05: difference from control cultures treated with Fas antibody or Staurosporine in the absence of BI6C9.