Figure 2. Calpain, the cellular cysteine protease responsible for ACT cleavage into J774A.1 cells.

Effect of several inhibitors of cysteine proteases (100 µM calpeptin, 0.5 mM NEM and 78 nM SJA6017) on the proteolytic processing of ACT (35 nM) in macrophages, upon 10 minutes incubation of cells with the toxin, as assayed by Western blot of a cytosolic fraction purified from the ACT-treated cells. Cells were previously incubated with the various inhibitors for 30 min, before toxin addition (A) Densitometric quantification of the two major bands detected in the immunoblots (B). Levels of significance were determined by a two-tailed Student's t-test, and a confidence level of greater than 95% (p<0.05) was used to establish statistical significance. *p<0.001 with respect to 50 kDa band; #p<0.001 with respect to 45 kDa band.