Old World Arenaviruses Enter the Host Cell via the Multivesicular Body and Depend on the Endosomal Sorting Complex Required for Transport

Abstract

The highly pathogenic Old World arenavirus Lassa virus (LASV) and the prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) use α-dystroglycan as a cellular receptor and enter the host cell by an unusual endocytotic pathway independent of clathrin, caveolin, dynamin, and actin. Upon internalization, the viruses are delivered to acidified endosomes in a Rab5-independent manner bypassing classical routes of incoming vesicular trafficking. Here we sought to identify cellular factors involved in the unusual and largely unknown entry pathway of LASV and LCMV. Cell entry of LASV and LCMV required microtubular transport to late endosomes, consistent with the low fusion pH of the viral envelope glycoproteins. Productive infection with recombinant LCMV expressing LASV envelope glycoprotein (rLCMV-LASVGP) and LCMV depended on phosphatidyl inositol 3-kinase (PI3K) as well as lysobisphosphatidic acid (LBPA), an unusual phospholipid that is involved in the formation of intraluminal vesicles (ILV) of the multivesicular body (MVB) of the late endosome. We provide evidence for a role of the endosomal sorting complex required for transport (ESCRT) in LASV and LCMV cell entry, in particular the ESCRT components Hrs, Tsg101, Vps22, and Vps24, as well as the ESCRT-associated ATPase Vps4 involved in fission of ILV. Productive infection with rLCMV-LASVGP and LCMV also critically depended on the ESCRT-associated protein Alix, which is implicated in membrane dynamics of the MVB/late endosomes. Our study identifies crucial cellular factors implicated in Old World arenavirus cell entry and indicates that LASV and LCMV invade the host cell passing via the MVB/late endosome. Our data further suggest that the virus-receptor complexes undergo sorting into ILV of the MVB mediated by the ESCRT, possibly using a pathway that may be linked to the cellular trafficking and degradation of the cellular receptor.

Diseases of the central nervous system caused by lymphocytic choriomeningitis virus and other arenaviruses

“…GP1 mediates attachment of the virus to its cellular target and subsequent receptor-mediated endocytosis (Pasqual et al, 2011). Alpha-dystroglycan has been identified as a cell receptor for LCMV and Lassa fever (LF) virus while human transferrin receptor 1 is the cell receptor for Junin and several other New World viruses (Cao et al, 1998;Smelt et al, 2001;Rojek and Kunz, 2008).…”

Vaccinia Virus Infection Requires Maturation of Macropinosomes

“…In addition, there is conversion of phosphatidylinositol 3‐phosphate (PtdIns(3)P) to PtdIns(3,5)P 2 , and progressive luminal acidification 7, 8, 9, 10, 11. As virus penetration and uncoating relies on the environment within maturing endosomes, it is perhaps no surprise that for many viruses, infection depends on factors involved in the maturation process 12, 13, 14.…”

Quantitative imaging of endosome acidification and single retrovirus fusion with distinct pools of early endosomes

“…Those that are activated at less acidic pH (∼6.0) are thought to mediate fusion with early endosomes, whereas those with a lower pH threshold (∼5.0) appear to direct the virus entry from late endosomes (1,3). However, recent evidence implies that factors other than low pH, such as specific endosome-resident lipids, can determine the intracellular compartments from which the viral capsid is released into the cytosol (2,4,5). Progress in understanding the complex regulation of virus-endosome fusion has been hindered by poor accessibility of intracellular compartments and lack of direct techniques for monitoring this process in situ.…”