Figure 9.

GA-induced redistribution of internalized trastuzumab. BT474 cells with surface-bound trastuzumab (trast, 15 nm gold) were incubated with GA for 3 h at 37°C and processed for double immunogold labeling. (A) Internalized trastuzumab is predominantly localized to internal vesicles of MVBs that are distinct from lysosomes (L) by morphology and CD63 (10 nm gold) labeling level. (B) Trastuzumab-positive MVBs have immature features: association with recycling tubules positive for TfR (10 nm gold, arrows) and frequent presence of bilayered coats. Inset: a recycling tubule (arrow) extends from a trastuzumab-positive endosome toward a group of TfR-containing recycling vesicles. Arrowheads, bilayered coats. Scale bars, 200 nm.