Immunoelectron Microscopic Evidence for Tetherin/BST2 as the Physical Bridge between HIV-1 Virions and the Plasma Membrane

• Type of Material: Article
• Authors: Jason Edward Hammonds, Emory University; Jaang-Jiun Wang, Emory University; Hong Yi, Emory University; Paul Spearman, Emory University
• Language: English
• Date: 2010-02-05
• Publisher: Public Library of Science
• Publication Version: Final Published Version
• Copyright Statement: © 2010 Hammonds et al.
• License: Creative Commons Attribution 3.0 Unported
• Final Published Version (URL): http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000749
• Title of Journal or Parent Work: PLoS Pathogens
• ISSN: 1553-7366
• Volume: 6
• Issue: 2
• Start Page: 1
• End Page: 11
• Grant/Funding Information: This work was supported by NIH R01 AI058828 (P.S.) and by a grant from the Emory-Egleston Child Health Research Center (EECRC) (J-J.W.).; This work was also supported in part by the Emory Center for AIDS Research (P30 AI050409) and by the Flow Cytometry Core Laboratory of the Emory-Children's Center.
• Research Categories: Biology, Microbiology; Health Sciences, Immunology

Abstract

Tetherin/BST2 was identified in 2008 as the cellular factor responsible for restricting HIV-1 replication at a very late stage in the lifecycle. Tetherin acts to retain virion particles on the plasma membrane after budding has been completed. Infected cells that express large amounts of tetherin display large strings of HIV virions that remain attached to the plasma membrane. Vpu is an HIV-1 accessory protein that specifically counteracts the restriction to virus release contributed by tetherin. Tetherin is an unusual Type II transmembrane protein that contains a GPI anchor at its C-terminus and is found in lipid rafts. The leading model for the mechanism of action of tetherin is that it functions as a direct physical tether bridging virions and the plasma membrane. However, evidence that tetherin functions as a physical tether has thus far been indirect. Here we demonstrate by biochemical and immunoelectron microscopic methods that endogenous tetherin is present on the viral particle and forms a bridge between virion particles and the plasma membrane. Endogenous tetherin was found on HIV particles that were released by partial proteolytic digestion. Immunoelectron microscopy performed on HIV-infected T cells demonstrated that tetherin forms an apparent physical link between virions and connects patches of virions to the plasma membrane. Linear filamentous strands that were highly enriched in tetherin bridged the space between some virions. We conclude that tetherin is the physical tether linking HIV-1 virions and the plasma membrane. The presence of filaments with which multiple molecules of tetherin interact in connecting virion particles is strongly suggested by the morphologic evidence.