β-Arrestin-2 enhances endoplasmic reticulum stress-induced glomerular endothelial cell injury by activating transcription factor 6 in diabetic nephropathy

Figure 6 β-Arrestin-2 enhances expression of activating transcription factor 6 and promotes activating transcription factor 6 translocation into the nucleus of glomerular endothelial cells treated with high glucose. A: Representative images and summarized data showing that knockdown of β-arrestin-2 reduced protein levels of BiP and CHOP, which was reversed by overexpression of activating transcription factor 6 (ATF6) [^aP < 0.05 vs scramble/control, ^bP < 0.01 vs scramble/control, ^dP < 0.05 vs scramble/high glucose (HG) treatment, ⁱP < 0.05 vs Si-β-arrestin-2/HG treatment]; B: Representative images and summarized data showing that knockdown of β-arrestin-2 recovered protein levels of ZO-1 and Occludin, which was reversed by overexpression of ATF6 (^aP < 0.05 vs scramble/control, ^dP < 0.05 vs scramble/HG treatment, ⁱP < 0.05 vs Si-β-arrestin-2/HG treatment); C: Flow cytometric analysis showing that knockdown of β-arrestin-2 reduced apoptosis of glomerular endothelial cells treated with HG was reversed by overexpression of ATF6; D: Representative images and summarized data showing that knockdown of β-arrestin-2 reduced apoptosis related protein expression, which was reversed by overexpression of ATF6. Silencing of β-arrestin-2 decreased expression of ATF6, but overexpression of ATF6 did not change expression of β-arrestin-2 (^aP < 0.05 vs scramble/control, ^dP < 0.05 vs scramble/HG treatment, ⁱP < 0.05 vs Si-β-arrestin-2/HG treatment); E: Representative Western blot images and summarized data showing expression of cleaved ATF6 in the nucleus of cells under different stimuli (^bP < 0.01 vs scramble/control, ^cP < 0.001 vs scramble/control, ^dP < 0.05 vs scramble/HG treatment, ^gP < 0.05 vs pCDNA-β-arrestin-2 treatment, ⁱP < 0.05 vs Si-β-arrestin-2/HG treatment); F: Relative mRNA levels of GRP78 (^aP < 0.05 vs scramble/control, ^bP < 0.01 vs scramble/control, ^dP < 0.05 vs scramble/HG treatment, ^fP < 0.05 vs TM/TG treatment, ^gP < 0.05 vs pCDNA-β-arrestin-2 treatment, ⁱP < 0.05 vs Si-β-arrestin-2/HG treatment). ATF6: Activating transcription factor 6; HG: High glucose; TM: Tunicamycin; 4-PBA: 4-Phenyl butyric acid.