Dengue infection activates the ATF6 pathway. (A) A549 cells were transiently transfected with GFP-ATF6 plasmid. After 24 h, the cells were left untreated or infected with DENV2 virus at 10 MOI. Twenty four hours post-infection, immunocytochemistry analysis was performed to detect GFP-ATF6 (green), the viral E protein (red), and cell nuclei were detected by DAPI staining (blue). (B) A549 cells were either treated with thapsigargin (TG) or infected with DENV1 and DENV2 and total mRNA was extracted and analyzed for XBP1 expression by RT-PCR as in Figure 5. The XBP1 mRNA level was quantified by densitometry as the total of all spliced forms of XBP1 and expressed as fold increase compared to untreated cells (Ctrl).