Figure 1. Activation of ERK8 by As₂O₃ in a dose and time-dependent manner in Xpress-ERK8 transfected cells.

HEK293T cells were transfected with pcDNA4/HisMaxA control or pcDNA4/Xpress-ERK8 expression plasmids (6 μg). At 24 h post-transfection, they were cultured in serum-free medium for 24 h, after which they were sham exposed or exposed to As₂O₃ and monitored. (A) 1 to 10 μM As₂O₃ for 4 h; (B) 5 μM As₂O₃ for 1 to 8 h; and (C) 5 μM As₂O₃ for 4 h. Cells were lysed, and protein extracts were subjected to SDS-PAGE followed by immunobloting using antibodies against p-ERK8 (Thr¹⁷⁵/Tyr¹⁷⁷). After development, the membranes were stripped and reprobed with regular antibodies against ERK8, Xpress, ERK1/2, and β-actin to monitor the total level of ERK8, ERK1/2, and loading difference, respectively. The data are representative of three independent experiments.