title: Vpu antagonizes BST-2-mediated restriction of HIV-1 release via beta-TrCP and endo-lysosomal trafficking.
abstract: The interferon-induced transmembrane protein BST-2/CD317 (tetherin) restricts the release of diverse enveloped viruses from infected cells. The HIV-1 accessory protein Vpu antagonizes this restriction by an unknown mechanism that likely involves the down-regulation of BST-2 from the cell surface. Here, we show that the optimal removal of BST-2 from the plasma membrane by Vpu requires the cellular protein beta-TrCP, a substrate adaptor for a multi-subunit SCF E3 ubiquitin ligase complex and a known Vpu-interacting protein. beta-TrCP is also required for the optimal enhancement of virion-release by Vpu. Mutations in the DSGxxS beta-TrCP binding-motif of Vpu impair both the down-regulation of BST-2 and the enhancement of virion-release. Such mutations also confer dominant-negative activity, consistent with a model in which Vpu links BST-2 to beta-TrCP. Optimal down-regulation of BST-2 from the cell surface by Vpu also requires the endocytic clathrin adaptor AP-2, although the rate of endocytosis is not increased; these data suggest that Vpu induces post-endocytic membrane trafficking events whose net effect is the removal of BST-2 from the cell surface. In addition to its marked effect on cell-surface levels, Vpu modestly decreases the total cellular levels of BST-2. The decreases in cell-surface and intracellular BST-2 are inhibited by bafilomycin A1, an inhibitor of endosomal acidification; these data suggest that Vpu induces late endosomal targeting and partial degradation of BST-2 in lysosomes. The Vpu-mediated decrease in surface expression is associated with reduced co-localization of BST-2 and the virion protein Gag along the plasma membrane. Together, the data support a model in which Vpu co-opts the beta-TrCP/SCF E3 ubiquitin ligase complex to induce endosomal trafficking events that remove BST-2 from its site of action as a virion-tethering factor.
authors.affiliation: Department of Medicine, University of California San Diego, La Jolla, CA, USA.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Mitchell
authors.forename: Chris
authors.initials: C
authors.lastname: Katsura
authors.forename: Mark A
authors.initials: MA
authors.lastname: Skasko
authors.forename: Katie
authors.initials: K
authors.lastname: Fitzpatrick
authors.forename: David
authors.initials: D
authors.lastname: Lau
authors.forename: Autumn
authors.initials: A
authors.lastname: Ruiz
authors.forename: Edward B
authors.initials: EB
authors.lastname: Stephens
authors.forename: Florence
authors.initials: F
authors.lastname: Margottin-Goguet
authors.forename: Richard
authors.initials: R
authors.lastname: Benarous
authors.forename: John C
authors.initials: JC
authors.lastname: Guatelli
mesh_terms: D033962:Adaptor Protein Complex 2; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation; D011992:Endosomes / Q000378:metabolism; D058851:GPI-Linked Proteins; D015497:HIV-1 / Q000472:pathogenicity* / Q000502:physiology; D054298:Human Immunodeficiency Virus Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008247:Lysosomes / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D021381:Protein Transport; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics / Q000502:physiology*; D044844:beta-Transducin Repeat-Containing Proteins / Q000235:genetics / Q000378:metabolism*; D000074010:Bone Marrow Stromal Antigen 2; D000086082:Viroporin Proteins
chemical_list: D033962:Adaptor Protein Complex 2; D015703:Antigens, CD; D058851:GPI-Linked Proteins; D054298:Human Immunodeficiency Virus Proteins; D008562:Membrane Glycoproteins; D054334:Viral Regulatory and Accessory Proteins; D044844:beta-Transducin Repeat-Containing Proteins; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2; C514859:vpu protein, Human immunodeficiency virus 1; D000086082:Viroporin Proteins