Figure 3.

RL71 induces ER stress by targeting SERCA. (a) MDA-MB-468 cells were treated with various concentrations of RL71 or TG (1 μM) for 24 h. Then, the Ca²⁺-ATPase activity was measured according to the instruction. *P<0.05, **P<0.01 versus untreated controls. (b) Fura-2/AM loaded MDA-MB-468 cells were stimulated with or without RL71 (2 μM). The y axes represent the percentage of intracellular Ca²⁺ concentration. The x axes depict the time in seconds, with time 0 representing the time of RL71 addition. The data are representative of at least 3 experiments. (c) Changes of [Ca²⁺]_i after pretreatment with or without TG (5 μM), followed by stimulation with RL71 (2 μM). The data are representative of at least three experiments. (d) MDA-MB-468 cells were treated with 10 μM of RL71 for 2 h and stained with ER tracker. Confocal microscopy was performed after a 2 h incubation. Scale bar: 10 μm. (e) MDA-MB-468 were incubated with various concentrations of RL71 or TG (1 μM) for 24 h or in the presence of RL71 (2 μM) for different time courses. The protein levels of ubiquitin-linked proteins (Ub), Grp78, ATF4, CHOP and p-PERK were determined by western blot. β-Actin was used as a loading control. **P<0.01 versus untreated controls