Dynamic properties of endosomal membranes: implications for endocytic sorting and viral infection

Abstract

Like other enveloped viruses, vesicular stomatitis virus infects cells through endosomes. There, the viral envelope undergoes fusion with endosomal membranes, thereby releasing the nucleocapsid into the cytoplasm and allowing infection to proceed. Here, we report that the viral envelope fuses preferentially with the membrane of vesicles present within multivesicular endosomes. Then, these intra-endosomal vesicles (containing nucleocapsids) are transported to late endosomes, where back-fusion with the endosome limiting membrane delivers the nucleocapsid into the cytoplasm. Presumably, export of cargo proteins from within endosomes also occurs "via" back-fusion with the limiting membrane, so that they become available for subsequent transport to their final destination. We further find out that this back-fusion process is altered by cholesterol accumulation and is regulated by the ESCRT component Tsg101, the endosomal lipid lysobisphosphatidic acid under the control of Ali/Vps31p and by phosphatidylinositol-3-phosphate "via" SNX16