Figure 3

Vesicle components are internalized by lung cells, and internalization is inhibited by hypertonic sucrose and cyclodextrins. A, SDS-PAGE gel profiles of S470 vesicles before and after AF488 labeling. Total protein in unlabeled vesicles was visualized after SYPRO Ruby staining of the gel (R). AF488-labeled proteins were visualized by placing the unstained gel on a UV lightbox (F). The migration of molecular weight standards (kDa) and PaAP (arrow) is indicated. B, A549 cells incubated with 2.5 μg AF488-labeled S470 vesicles (green) for 1 h at 37°C. Cell surface was labeled using biotin and AF633-streptavidin (blue), fixed in 2% paraformaldehyde, and visualized by confocal microscopy. A549 cells were pretreated with 10 mM methyl-β-cyclodextrin (C), 10 mM α-cyclodextrin (D), or 0.45 M sucrose (E), for 30 minutes, and then incubated with 2.5 μg AF488-labeled S470 vesicles (green) for 1 h at 37°C. Cell surface was labeled using biotin and AF633-streptavidin (blue), fixed in 2% paraformaldehyde, and visualized by confocal microscopy. Bars indicate 25 μm.