Fig. 2.

The cleaved caspase-4 small subunit p10 occurs early in IFNα expressing cells which co-localizes with the ER. A, Cleaved caspase-4 cells (red) are seen in only IFNα expressing cells (green) 48 h after Ad-IFNα treatment and both co-localize with the enhanced ER signals (blue).

B, The small subunit p10 of caspase 4 (green) was detected in the Ad-IFNα transfected cells (red) 12 hr after Ad-IFNα infection whereas caspases 3 was not activated at the same time point. At 24hr after Ad-IFNα treatment, both cleaved caspase 4 (green) and caspase 3 (blue) forms were stained. The active form of caspase 3 was detected in both Ad-IFNα-expressing (solid arrow) and non-expressing cells (dashed arrow) whereas caspase 4 was only seen in IFNα expressing cells. This indicates that caspase 4 was activated only in cells which were infected with Ad-IFNα whereas caspase 3 was activated by both Ad-IFNα infection and bystander factors. Nuclei were counterstained with DAPI (grey-white). HeLa cells are shown in this experiment but similar results were seen in UC-9 cells. Original Magnification × 400.