Fig. 3.

Calcium is required for caspase-1 activation by LT: target cell interaction and LF translocation into the cytosol. Macrophages were treated with LT or S. typhimurium (S.T) in Ca²⁺-free medium with 1 mM EDTA or in medium containing 150 μM verapamil, a Ca²⁺ channel blocker. (A) Macrophages containing active caspase-1 were identified by FAM-YVAD staining; means ± SD are shown. *, P < 0.05 versus medium. (B) Cleaved LF substrate MEK3 (arrow) in LT-intoxicated macrophages was detected by Western blot. Where indicated, macrophages treated with detergent released membrane-enclosed LF and cleaved MEK3 was detected by Western blot in the lysates.