Figure 4. β-arrestin-2 promotes ER stress by suppressing BiP. (A) BiP was upregulated by more than 50% in the KO+NEC group compared with the WT+NEC group. (B) Specific siRNA reduced β-arrestin-2 expression, as determined by real-time PCR and Western blotting. (C) Plasmid transfection efficiently increased β-arrestin-2 expression, as determined by real-time PCR and Western blotting. (D) Flow cytometry analysis revealed that apoptosis increased when β-arrestin-2 was overexpressed and decreased when β-arrestin-2 was silenced. (E) A TUNEL assay revealed that apoptosis was attenuated when β-arrestin-2 was silenced. (F) Compared with control siRNA (Csi), siRNA against β-arrestin-2 reduced CC3 expression by 22% and increased BiP expression by 22% in LPS-treated cells. (G) Compared with the control vector (Vec), overexpression of β-arrestin-2 increased CC3 expression by 67% and reduced BiP expression by 35% in LPS-treated cells. (H, I) As a positive control, thapsigargin (THAP) yielded similar results to LPS.