title: Tetraspanins regulate cell-to-cell transmission of HIV-1.
abstract: BACKGROUND
  The presence of the tetraspanins CD9, CD63, CD81 and CD82 at HIV-1 budding sites, at the virological synapse (VS), and their enrichment in HIV-1 virions has been well-documented, but it remained unclear if these proteins play a role in the late phase of the viral replication cycle. Here we used overexpression and knockdown approaches to address this question.
  
  
  RESULTS
  Neither ablation of CD9, CD63 and/or CD81, nor overexpression of these tetraspanins was found to affect the efficiency of virus release. However, confirming recently reported data, tetraspanin overexpression in virus-producing cells resulted in the release of virions with substantially reduced infectivity. We also investigated the roles of these tetraspanins in cell-to-cell transmission of HIV-1. Overexpression of CD9 and CD63 led to reduced cell-to-cell transmission of this virus. Interestingly, in knockdown experiments we found that ablation of CD63, CD9 and/or CD81 had no effect on cell-free infectivity. However, knockdown of CD81, but not CD9 and CD63, enhanced productive particle transmission to target cells, suggesting additional roles for tetraspanins in the transmission process. Finally, tetraspanins were found to be downregulated in HIV-1-infected T lymphocytes, suggesting that HIV-1 modulates the levels of these proteins in order to maximize the efficiency of its transmission within the host.
  
  
  CONCLUSIONS
  Altogether, these results establish an active role of tetraspanins in HIV-1 producer cells.
authors: Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, VT 05405, USA. dkrement@uvm.edu
authors: Dimitry N
authors: DN
authors: Krementsov
authors: Jia
authors: J
authors: Weng
authors: Marie
authors: M
authors: Lambelé
authors: Nathan H
authors: NH
authors: Roy
authors: Markus
authors: M
authors: Thali
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D024882:Drug Resistance, Viral; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology*; D019427:HIV Integrase / Q000235:genetics*; D019428:HIV Integrase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D011110:Polymorphism, Genetic; D017422:Sequence Analysis, DNA
chemical_list: D019428:HIV Integrase Inhibitors; D019427:HIV Integrase; C514801:p31 integrase protein, Human immunodeficiency virus 1