Fig. 4.

Complex internal organization of CPVs and connection with the endo-lysosomal pathway. (A) Metal replica of a RUBV factory processed by freeze-etching showing the interior of a CPV with a rigid membrane (black arrow) wrapping two large vacuoles (asterisks). (B and C) Ultra-thin sections of CPVs as visualized by TEM after staining. (B) Rigid membrane (arrows) contacting two vacuoles (asterisks). (C) A section along the rigid membrane showing features compatible with a close packing of particles (black arrow). The white arrow points to the spot where the rigid membrane interacts with the membrane of the large vacuole. (D to F) Computational slices (~ 0.6 nm for D and E, ~ 1.2 nm for F) of two tomograms of CPVs filtered with three rounds of a median filter. (D) Groups of particles associated with a large vacuole (arrow) and (E) stacked membranes (white dashed ellipse) are shown. (F) Openings to the cytosol (arrows) in the peripheral membrane of a CPV (frontal view). Thin-sections of lysosomes from control BHK-21 cells (G and H) and CPVs from stably transfected cells (I and J) after treatment with BSA-gold in culture and posterior fixation and embedding. Both lysosomes (lys) from control cells and CPVs contain BSA-gold particles (arrows). RER, rough endoplasmic reticulum; mi, mitochondria; Bars, 200 nm.