Fig. 3.

Knockdown of the PP2A expression level diminishes autophagosome and lysosome fusion. a Confocal microscopic images of anti-PP2A siRNA-transfected ARPE-19 cells with or without paraquat. Cells were stained with Alexa 555-Phalloidin-stained (red) and immunostained for KRT8 (green). Scale bar: 5 μm. b Immunoblots of PP2A, KRT8, p-KRT8, SQSTM1, and LC3B in anti-PP2A siRNA-transfected ARPE-19 cells. Cells were treated with paraquat for 24 h. Bar graphs indicate SQSTM1 expression level or the ratio of LC3B-II to LC3B-I. Each protein band intensity was normalized to GAPDH. Data are presented as the mean ± SEM, n = 3. *P < 0.05 ***P < 0.001. c Confocal microscopic images of mCherry-EGFP-LC3B-expressing ARPE-19 cells. Cells were transfected with anti-PP2A siRNA and incubated with paraquat for 24 h. Scale bar: 5 μm. Bar graph indicates the percentage of each fluorescence level in the merged images of mCherry-EGFP-LC3B under paraquat treatment condition. Data are presented as the mean ± SEM, n = 3. ***P < 0.001. d Confocal microscopic images of LysoTracker Red-stained and GFP-LC3B-transfected ARPE-19 cells. Cells were transfected with anti-PP2A siRNA and incubated with paraquat for 24 h. Scale bar: 5 μm. Bar graph indicates the percentage of each fluorescence level in the merged images of GFP-LC3B and Lysotracker Red under oxidative stress condition. Data are presented as the mean ± SEM, n = 3. ***P < 0.001