Anti-Tetherin Activities of HIV-1 Vpu and Ebola Virus Glycoprotein Do Not Involve Removal of Tetherin from Lipid Rafts

Abstract

BST-2/tetherin is an interferon-inducible host restriction factor that blocks the release of newly formed enveloped viruses. It is enriched in lipid raft membrane microdomains, which are also the sites of assembly of several enveloped viruses. Viral anti-tetherin factors, such as the HIV-1 Vpu protein, typically act by removing tetherin from the cell surface. In contrast, the Ebola virus glycoprotein (GP) is unusual in that it blocks tetherin restriction without apparently altering its cell surface localization. We explored the possibility that GP acts to exclude tetherin from the specific sites of virus assembly without overtly removing it from the cell surface and that lipid raft exclusion is the mechanism involved. However, we found that neither GP nor Vpu had any effect on tetherin's distribution within lipid raft domains. Furthermore, GP did not prevent the colocalization of tetherin and budding viral particles. Contrary to previous reports, we also found no evidence that GP is itself a raft protein. Together, our data indicate that the exclusion of tetherin from lipid rafts is not the mechanism used by either HIV-1 Vpu or Ebola virus GP to counteract tetherin restriction.

Roles Played by Capsid-Dependent Induction of Membrane Curvature and Gag-ESCRT Interactions in Tetherin Recruitment to HIV-1 Assembly Sites

“…2A to C). While association of Vpu with lipid rafts is debated (17,62,63), such association could be a confounding factor in the experiments using HeLa cells. To directly examine the effect of tetherin, we used HT-1080 cells that do not express endogenous tetherin.…”

“…The ability of tetherin to form dimers or possibly higher-order multimers has also been shown to contribute to its antiviral function (11)(12)(13)(14)(15). As with other GPIanchored proteins, tetherin is thought to reside in lipid rafts, based on its resistance to detergent solubilization and cholesterol dependence of this detergent resistance (16)(17)(18). Tetherin is able to inhibit a broad range of unrelated enveloped viruses, ruling out a direct interaction with any particular viral protein as a requirement for restriction of virus release (19,20).…”

The role of BST‐2/Tetherin in host protection and disease manifestation

“…Although the function of BST‐2 glycosylation for inhibition of virus release is unclear 11, 22, this post‐translational modification is important for proper folding and trafficking of BST‐2 through the endoplasmic reticulum (ER) and the Golgi 23. BST‐2 molecule associates with lipid rafts 1, 9, 13, 24, 25, 26 through the GPI anchor 9 (Fig. 1).…”

The Size and Conservation of a Coiled-coil Structure in the Ectodomain of Human BST-2/Tetherin Is Dispensable for Inhibition of HIV-1 Virion Release

“…In addition, BST-2 is modified by N-linked glycosylation at two sites in the BST-2 ectodomain (20,23,29,30); however, the functional importance of BST-2 glycosylation for inhibition of virus release is under debate (29,30). Finally, BST-2 protein associates with lipid rafts at the cell surface and on internal membranes (23,(31)(32)(33)(34) and the C-terminal TM region has been implicated with raft targeting of BST-2 (23).…”