Figure 1. Cell permeabilization with SLO induces formation of endosomes that increase in size over time.
Cells were incubated or not with 250 ng/mL SLO for 5 min at 4°C, washed and shifted to 37°C in the presence of Ca2+ for increasing periods of time in the presence of BSA-gold as an endocytic tracer. A) Representative TEM images of endosomes containing BSA-gold (arrowheads) at various time-points. BSA-gold-positive endosomes with flat electron-dense coats on their limiting membrane (arrows) increase in size and acquire internal vesicles over time. Bars = 100 nm. B) Quantification of BSA-gold-containing endosomes show a significant increase in newly formed endosomes from 1 to 15 min after permeabilization in SLO-treated cells, when compared to control cells. C) Endosome area is significantly larger in SLO-treated cells from 1 to 15 min after permeabilization, when compared to control cells. Results are expressed as mean ± SEM. **p < 0.01, unpaired Student’s t-test.