HIV-1 Gag can assemble and generate virions at the plasma membrane, but it is also present in endosomes where its role remains incompletely characterized. Here, we show that HIV-1 RNAs and Gag are transported on endosomal vesicles positive for TiVamp, a v-SNARE involved in fusion events with the plasma membrane. Inhibition of endosomal traffic did not prevent viral release. However, inhibiting lysosomal degradation induced an accumulation of Gag in endosomes and increased viral production 7-fold, indicating that transport of Gag to lysosomes negatively regulates budding. This also suggested that endosomal Gag-RNA complexes could access retrograde pathways to the cell surface and indeed, depleting cells of TiVamp-reduced viral production. Moreover, inhibition of endosomal transport prevented the accumulation of Gag at sites of cellular contact. HIV-1 Gag could thus generate virions using two pathways, either directly from the plasma membrane or through an endosome-dependent route. Endosomal Gag-RNA complexes may be delivered at specific sites to facilitate cell-to-cell viral transmission.
Endosomal trafficking of HIV-1 gag and genomic RNAs regulates viral egress
Molle, D.; Segura-Morales, C.; Camus, G.; Berlioz-Torrent, C.; Kjems, J.; Basyuk, E.; Bertrand, E.
J Biol Chem
2009-07-17 / vol 284 / pages 19727-43
10.1074/jbc.M109.019844 M109.019844 [pii]
0021-9258 (Print) 0021-9258 (Linking)
Cell Line, Tumor; Humans; RNA, Small Interfering/genetics; Time Factors; Blotting, Western; Fluorescent Antibody Technique; Recombinant Fusion Proteins/genetics/metabolism; Transfection; In Situ Hybridization, Fluorescence; Biological Transport/drug effects; Calcium Chloride/pharmacology; Chloroquine/pharmacology; Endosomes/*metabolism/ultrastructure/virology; gag Gene Products, Human Immunodeficiency Virus/genetics/*metabolism; HIV-1/genetics/isolation & purification/*metabolism; Ionophores/pharmacology; Luminescent Proteins/genetics/metabolism; Microscopy, Electron; Monensin/pharmacology; Nocodazole/pharmacology; RNA Transport/drug effects; RNA, Viral/genetics/*metabolism; SNARE Proteins/genetics/metabolism