Abstract
Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication. The HIV-1 accessory protein viral protein U (Vpu) enhances release of the virus from host cells by down-regulating the cell-surface expression of the host restriction factor tetherin. However, the exact mechanism of Vpu-mediated suppression of antiviral host responses is unclear. To further understand the role of host proteins in Vpu's function, here we carried out yeast two-hybrid screening and identified the V0 subunit C of vacuolar ATPase (ATP6V0C) as a Vpu-binding protein. To examine the role of ATP6V0C in Vpu-mediated tetherin degradation and HIV-1 release, we knocked down ATP6V0C expression in HeLa cells and observed that ATP6V0C depletion impairs Vpu-mediated tetherin degradation, resulting in defective HIV-1 release. We also observed that ATP6V0C overexpression stabilizes tetherin expression. This stabilization effect was specific to ATP6V0C, as overexpression of another subunit of the vacuolar ATPase, ATP6V0C″, had no effect on tetherin expression. ATP6V0C overexpression did not stabilize CD4, another target of Vpu-mediated degradation. Immunofluorescence localization experiments revealed that the ATP6V0C-stabilized tetherin is sequestered in a CD63- and lysosome-associated membrane protein 1 (LAMP1)-positive intracellular compartment. These results indicate that the Vpu-interacting protein ATP6V0C plays a role in down-regulating cell-surface expression of tetherin and thereby contributes to HIV-1 assembly and release.
Highlights
Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication
Because ATP6V0C is involved in lysosomal degradation and viral protein U (Vpu) promotes the lysosomal degradation of tetherin, we investigated the effect of ATP6V0C depletion on HIV-1 particle production in the presence and absence of Vpu
We investigated the role of another Vpu-interacting protein, ATP6V0C, in Vpu-mediated tetherin degradation and HIV-1 release
Summary
Host proteins with antiviral activity have evolved as first-line defenses to suppress viral replication. Our results demonstrate that the Vpu-interacting protein ATP6V0C plays a role in Vpu-mediated tetherin degradation and HIV-1 release. We investigated the role of another Vpu-interacting protein, ATP6V0C, in Vpu-mediated tetherin degradation and HIV-1 release.
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