Figure 6. R70 and SyH7 promote ricin accumulation in Lamp-1⁺ vesicles.

Vero cells were treated at 4 °C with R70 or SyH7 and ricin-FITC, in the absence or presence of NH₄Cl to prevent lysosome acidification, and then shifted to 37 °C for 4.5 hr. (A) Vero cells were then fixed and stained with Alexa Fluor-647 labeled Lamp-1 antibodies. NH₄Cl treatment resulted in the accumulation of ricin-R70 or ricin-SyH7 containing vesicles that were positive for Lamp-1 (arrowheads within insets, bottom right panels). Scale bar, 5 μm. (B) The frequency of ricin (in the absence or presence of R70 or SyH7) colocalization with Lamp-1 in cells treated or not with NH₄Cl. Each bar represents the average of 25–30 cells (with SEM) per time point. ***p < 0.001, determined using a one-way ANOVA with Tukey’s post-test.