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. 1999 Sep;19(9):5991–6002. doi: 10.1128/mcb.19.9.5991

FIG. 6.

FIG. 6

Caspase 8 and caspase 3 activities in FasR-stimulated cells are affected by modulation of MAPK activity. (A) To analyze the kinetics of FasR-induced caspase activation in the presence and absence PD 98059, HeLa cells were treated as outlined in the legend to Fig. 1. Caspase activation can be observed as the appearance of active fragments of the caspase proforms of caspase 8 (a) and caspase 3 (b) (see text for details). No significant activation occurred in the absence of PD 98059. (B) To test the effect of MAPK activation on the activity of the apoptotic initiator, caspase 8, the cell line with the constitutively active MKK1 (MKK1 S218E/S222D) was incubated for 3 days in the presence or absence of tetracycline and then treated for 24 h as described for Fig. 1. The MKK1-negative cells detached during this treatment and were washed off. The remaining cells were scraped off the culture flasks, centrifuged, washed, and lysed prior to immunoblotting with antibodies to caspase 8 as described in Materials and Methods. Each well was loaded with 25 μg of protein.

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