Fig. 5. Bafilomycin A1 does not induce fragmentation of giant late endosomes in rab5(Q79L)-expressing cells. To investigate the effect of bafilomycin A1 (Baf) on the giant endosomes in rab5(Q79L)-expressing cells, late endosomes (le) were formed by a 1 hour/4 hour pulse-chase of 35 nm BSA-gold particles, and the same cells were then allowed to internalize 5 nm BSA-gold particles for 30 minutes in order to load mostly early endosomes (ee) (A). The two sizes of particles are found in different endosome populations, both representing quite large endosomes. Panel B corresponds to an inset of panel A, allowing a better visualization of early endosomes containing only 5 nm BSA-gold particles. The same experiment was repeated, with cells incubated in the presence of 500 nM bafilomycin A1 for 30 minutes after the pulse-chase of gold particles. In C, we show a large late endosome filled with 35 nm BSA-gold particles, while the 5 nm BSA-gold particles are now found in very small vesiculo-tubular structures, better seen at a higher magnification (D). Bars, 250 nm (A,C); 50 nm (B,D).

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