Fig. 1: Inhibition of cathepsin S induces ER stress.

a Human renal carcinoma Caki cells were treated with 0.5, 1, or 2 μM ZFL for 8 h (p.c. positive control; brefeldin A for 8 h). b Caki cells were transfected with siRNA against control or cathepsin S for 24 h (p.c.; brefeldin A for 8 h). c Caki cells were treated with 2 μM ZFL for 24, 48, or 72 h (p.c.; 20 ng/mL TNF-α plus 5 μg/mL CHX for 24 h). d, e Caki cells were treated with 2 μM ZFL or 4 μM thapsigargin (TG) for the indicated time periods. Flow cytometry was used to detect the sub-G1 population, and western blotting was used to detect protein levels of PARP, GRP78, ATF4, REDD1, CHOP, and/or actin. The data in (c, d) are presented as the mean ± SD of three independent samples; *p < 0.01 compared to the control