FIG. 4.

Activation of GRP94/GRP78 by SARS-CoV S protein requires PERK and eIF2α phosphorylation. 293FT cells were cotransfected with pGRP78/94-Luc and expression vectors for the indicated combinations of proteins. Cells were harvested for dual luciferase assay as described for Fig. 2 (A to D). The steady-state levels of phosphorylated (*) and total (#) eIF2α in cells treated with DMSO (lanes 1 and 7) or Tg (300 nM; lanes 2 and 8), mock infected (lanes 3 and 9) or infected with SARS-CoV (lanes 4 and 10), and transfected with pLenti-Topo empty vector alone (lanes 5 and 11) or with pLenti-S (lanes 6 and 12) were verified by Western blotting (E). Treatment with Tg was used as a positive control in this experiment. WT, wild type.