A Cytoplasmic Tail Determinant in HIV-1 Vpu Mediates Targeting of Tetherin for Endosomal Degradation and Counteracts Interferon-Induced Restriction

PLoS Pathog. 2012;8(3):e1002609. doi: 10.1371/journal.ppat.1002609. Epub 2012 Mar 29.

Abstract

The HIV-1 accessory protein Vpu counteracts tetherin (BST-2/CD317) by preventing its incorporation into virions, reducing its surface expression, and ultimately promoting its degradation. Here we characterize a putative trafficking motif, EXXXLV, in the second alpha helix of the subtype-B Vpu cytoplasmic tail as being required for efficient tetherin antagonism. Mutation of this motif prevents ESCRT-dependent degradation of tetherin/Vpu complexes, tetherin cell surface downregulation, but not its physical interaction with Vpu. Importantly, this motif is required for efficient cell-free virion release from CD4+ T cells, particularly after their exposure to type-1 interferon, indicating that the ability to reduce surface tetherin levels and promote its degradation is important to counteract restriction under conditions that the virus likely encounters in vivo. Vpu EXXXLV mutants accumulate with tetherin at the cell surface and in endosomal compartments, but retain the ability to bind both β-TrCP2 and HRS, indicating that this motif is required for a post-binding trafficking event that commits tetherin for ESCRT-dependent degradation and prevents its transit to the plasma membrane and viral budding zones. We further found that while Vpu function is dependent on clathrin, and the entire second alpha helix of the Vpu tail can be functionally complemented by a clathrin adaptor binding peptide derived from HIV-1 Nef, none of the canonical clathrin adaptors nor retromer are required for this process. Finally we show that residual activity of Vpu EXXXLV mutants requires an intact endocytic motif in tetherin, suggesting that physical association of Vpu with tetherin during its recycling may be sufficient to compromise tetherin activity to some degree.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / immunology
  • Antigens, CD / metabolism*
  • Cytoplasm / metabolism
  • Endosomes / metabolism*
  • GPI-Linked Proteins / immunology
  • GPI-Linked Proteins / metabolism
  • Gene Expression Regulation, Viral
  • HEK293 Cells / metabolism
  • HEK293 Cells / virology
  • HIV-1 / drug effects
  • HIV-1 / metabolism
  • HIV-1 / pathogenicity*
  • HeLa Cells / metabolism
  • HeLa Cells / virology
  • Human Immunodeficiency Virus Proteins / genetics
  • Human Immunodeficiency Virus Proteins / metabolism*
  • Humans
  • Interferons / pharmacology*
  • Jurkat Cells / metabolism
  • Jurkat Cells / virology
  • Protein Interaction Domains and Motifs / physiology*
  • Protein Transport
  • Viral Regulatory and Accessory Proteins / genetics
  • Viral Regulatory and Accessory Proteins / metabolism*
  • Virion / metabolism
  • Virus Assembly
  • Virus Release / drug effects
  • Virus Replication

Substances

  • Antigens, CD
  • BST2 protein, human
  • GPI-Linked Proteins
  • Human Immunodeficiency Virus Proteins
  • Viral Regulatory and Accessory Proteins
  • vpu protein, Human immunodeficiency virus 1
  • Interferons