FIG. 3.

Apoptosis is induced by the caspase 8 pathway. A. HT1080 cells were treated with LY294002 and Sendai virus as previously described. Whole-cell lysates were prepared, and Western blot assays were performed with antibodies against caspase 8 and caspase 9. The positions of the full-length (57- and 47-kDa) and cleaved (43/41- and 37/35-kDa) caspase 8 and caspase 9 are indicated. B. LY294002 pretreatment and Sendai virus infection of HT1080 cells were performed as described in the legend for Fig. 1. Cells were lysed at the indicated time points, and a caspase 8 Western blot assay was performed as described for panel A. C. HT1080 cells were pretreated with 100 μM of the general caspase inhibitor z-VAD, the caspase 8 inhibitor z-IETD, the caspase 9 inhibitor z-LEHD, or the DMSO solvent control 1 hour before virus addition. The PI3 kinase inhibitor LY294002 (50 μM) was added to all cells 30 min before virus addition. Cells were fixed and stained 6 h after infection.