title: Mechanism of HIV-1 virion entrapment by tetherin.
abstract: Tetherin, an interferon-inducible membrane protein, inhibits the release of nascent enveloped viral particles from the surface of infected cells. However, the mechanisms underlying virion retention have not yet been fully delineated. Here, we employ biochemical assays and engineered tetherin proteins to demonstrate conclusively that virion tethers are composed of the tetherin protein itself, and to elucidate the configuration and topology that tetherin adopts during virion entrapment. We demonstrate that tetherin dimers adopt an "axial" configuration, in which pairs of transmembrane domains or pairs of glycosylphosphatidyl inositol anchors are inserted into assembling virion particles, while the remaining pair of membrane anchors remains embedded in the infected cell membrane. We use quantitative western blotting to determine that a few dozen tetherin dimers are used to tether each virion particle, and that there is ∼3- to 5-fold preference for the insertion of glycosylphosphatidyl inositol anchors rather than transmembrane domains into tethered virions. Cumulatively, these results demonstrate that axially configured tetherin homodimers are directly responsible for trapping virions at the cell surface. We suggest that insertion of glycosylphosphatidyl inositol anchors may be preferred so that effector functions that require exposure of the tetherin N-terminus to the cytoplasm of infected cells are retained.
authors.affiliation: Howard Hughes Medical Institute, Laboratory of Retrovirology, Aaron Diamond AIDS Research Center, The Rockefeller University, New York, New York, United States of America.
authors.forename: Siddarth
authors.initials: S
authors.lastname: Venkatesh
authors.forename: Paul D
authors.initials: PD
authors.lastname: Bieniasz
mesh_terms: D015703:Antigens, CD / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000998:Antiviral Agents / Q000737:chemistry / Q000378:metabolism*; D019281:Dimerization; D058851:GPI-Linked Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000378:metabolism; D057809:HEK293 Cells; D015497:HIV-1 / Q000276:immunology / Q000502:physiology*; D006367:HeLa Cells; D054298:Human Immunodeficiency Virus Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / Q000378:metabolism; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics / Q000378:metabolism; D014771:Virion / Q000276:immunology / Q000502:physiology*; D053585:Virus Attachment; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000096:biosynthesis; D000074010:Bone Marrow Stromal Antigen 2; D000086082:Viroporin Proteins
chemical_list: D015703:Antigens, CD; D000998:Antiviral Agents; D058851:GPI-Linked Proteins; D017261:Glycosylphosphatidylinositols; D054298:Human Immunodeficiency Virus Proteins; D010446:Peptide Fragments; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D011993:Recombinant Fusion Proteins; D054334:Viral Regulatory and Accessory Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus; C094572:BST2 protein, human; D000074010:Bone Marrow Stromal Antigen 2; C514859:vpu protein, Human immunodeficiency virus 1; D000086082:Viroporin Proteins