Regulation of PERK Signaling and Leukemic Cell Survival by a Novel Cytosolic Isoform of the UPR Regulator GRP78/BiP
Figure 7
GRP78va protects HL-60 cells from ER stress-induced cell death.
A, B. Knockdown of GRP78va in HL-60 cells. RT-PCR (A, left panel) or quantitative real-time PCR (A, right panel) was used to determine the level of Grp78va transcript in HL-60 cells transfected with the indicated siRNA. Western blot. B was performed to determine the levels of the proteins indicated. C. Inhibition of Tg-induced eIF2α phosphorylation by knockdown of GRP78va. HL-60 cells were transfected with either siCtrl or siGrp78va. After treatment with Tg (300 nM) for the indicated time, phospho-eIF2α and total eIF2α were detected by Western blot (upper panel). The experiments were repeated three times. The results are summarized and the ratio of p-eIF2α/eIF2α is plotted with SD (lower panel). The ratio of the non-treated, siCtrl transfected cells was set as 1. P values are indicated. D. Western blot of caspase-7, cleaved caspase-3 and β-actin in siRNA-transfected HL-60 cells treated with Tg for 24 hours. E. Soft-agar clonogenic survival assay for HL-60 cells after transfection with the indicated siRNA for 72 hours and then treated with Tg (300 nM) for the indicated time.