RT Journal Article
SR Electronic
T1 EWI-2 Inhibits Cell-Cell Fusion at the HIV-1 Virological Presynapse
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 296251
DO 10.1101/296251
A1 Emily E. Whitaker
A1 Nicholas J. Matheson
A1 Sarah Perlee
A1 Phillip B. Munson
A1 Menelaos Symeonides
A1 Markus Thali
YR 2019
UL http://biorxiv.org/content/early/2019/10/15/296251.abstract
AB Cell-to-cell transfer of virus particles at the Env-dependent virological synapse (VS) is a highly efficient mode of HIV-1 transmission. While cell-cell fusion could be triggered at the VS, leading to the formation of syncytia and preventing exponential growth of the infected cell population, this is strongly inhibited by both viral (Gag) and host (ezrin and tetraspanins) proteins. Here, we identify EWI-2, a protein that was previously shown to associate with ezrin and tetraspanins, as a host factor that contributes to the inhibition of Env-mediated cell-cell fusion. Using quantitative fluorescence microscopy, shRNA knockdowns, and cell-cell fusion assays, we show that EWI-2 accumulates at the presynaptic terminal (i.e. the producer cell side of the VS), where it contributes to the fusion-preventing activities of the other viral and cellular components. We also find that EWI-2, like tetraspanins, is downregulated upon HIV-1 infection, mostly by Vpu. Despite strong inhibition of fusion at the VS, T cell-based syncytia do form in vivo and in physiologically relevant culture systems, but they remain small. In regard to that, we demonstrate that EWI-2 and CD81 levels are restored on the surface of syncytia, where they (presumably) continue to act as fusion inhibitors. This study documents a new role for EWI-2 as an inhibitor of HIV-1-induced cell-cell fusion, and provides novel insight into how syncytia are prevented from fusing indefinitely.