Effects of oxidative and thermal stresses on stress granule formation in human induced pluripotent stem cells
(A and B) SA and HS treatments induce eIF2α phosphorylation and SG formation in hiPSCs. (A) Representative Immuno-blots that show the levels of peIF2α (Ser51) and eIF2α in non-treated cells (No treat and 37°C) or cells treated with 125μM sodium arsenite and 250μM H2O2, or subjected to heat shock (42°C). (B) Bar graph representing the ratio of (normalized against β-actin loading controls) peIF2α (Ser51)/eIF2α for each treatment. Values are expressed as mean ± SEM from 4–5 experiments. Asterisks indicate a statistically significant change, *p<0.05, **p<0.001, and ***p<0.0001. (C-E) Representative fluorescence microscopy images showing hiPSCs treated with sodium arsenite (125μM), subjected to heat shock (42°C), or left untreated (No treat; 37°C), and stained with SG markers (C) TIAR (red)/eIF4E (green)/ eIF4A (white), (D) eIF3b (red)/eIF4G (green)/PABP (white), and (E) eIF3b (red)/YB1 (white) or PB marker (SK1, green). Insets are reproduced at the right as replicate views of SGs showing each marker separately and the merged view (yellow). Scale bar indicates 5μm.