Determination of the role of viral and host factors in the budding of Ebola virus VP40 virus -like particles

The VP40 matrix protein of Ebola virus buds from cells in the form of virus-like particles (VLPs) and plays a central role in virus assembly and budding. VP40 contains overlapping L-domain sequences PTAP and PPEY at amino acids 7 to 13 (PTAPPEY). L-domains are thought to function by interacting with specific cellular proteins linked to the vacuolar protein sorting (vps) pathway. Using an in-depth mutational analysis of the PTAPPEY sequence of VP40, we demonstrate that both motifs contribute to efficient budding of VP40-containing VLPs. We also provide evidence of a role for host Nedd-4, tsg101, and vps4 in facilitating budding. In addition to host proteins, we assessed the contribution of additional viral proteins in promoting VP40 VLP release. We demonstrate that Ebola virus VP24 protein alone does not affect VP40 VLP release, whereas viral NP and GP enhance release of VP40 VLPs, individually and to a greater degree in concert. We have most recently begun to probe the mechanism for GP-enhanced VP40 VLP release. In all, these findings provide a more complete understanding of the role of VP40, additional Ebola virus proteins, as well as host cell machinery during viral budding.