Expression of mutant NE induces BiP expression in U937 cells. U937 cells were transiently transfected with vector alone (GFP), wild-type (WT), or mutant NE cDNAs, and 12 hours later GFP + cells were sorted by flow cytometry. BiP, NE, and ribosomal RNA (rRNA) were quantified by real-time RT-PCR. (A) Expression of BiP mRNA relative to rRNA is shown. (B) Expression of BiP mRNA to NE mRNA is shown. Data are normalized to WT-transfected cells, where the BiP to NE ratio in each experiment was defined as 1. Data represent the mean (± SD) of 5 independent experiments. *P < .05 compared with WT-transfected cells.