title: The dual role of tetraspanin CD63 in HIV-1 replication.
abstract: BACKGROUND
  Previously, we showed that the tetraspanin membrane protein CD63 mediates both early and post-integration stages of the HIV-1 replication cycle. The temporal roles of CD63 were discerned using monoclonal antibodies and small interfering RNAs (siRNAs) to block CD63 function, and determining which of the sequential steps in HIV-1 replication were disrupted. Inhibition was shown to occur during early infection, suggestive of involvement in virus entry or reverse transcription. In addition, we have shown that treatment with CD63 siRNA post-infection, significantly inhibited virus production in supernatant, suggesting an important role for CD63 in macrophages during HIV-1 replication events occurring after proviral integration, and possibly during egress.
  
  
  RESULTS
  In this study we used CD63 siRNA to investigate the infectivity of pseudotyped viruses (carrying an NL4-3 Env-negative luciferase backbone) in primary human macrophages. We demonstrated that lab adapted R5- and R5X4-tropic HIV-1 strains are significantly inhibited by CD63 silencing. However, the infectivity of MLV or VSV-pseudotyped strains, which enter though receptor-mediated endocytosis, is unaffected by silencing CD63. These results indicate that CD63 may support Env-mediated entry or fusion events facilitated though CD4 and CCR5. Also, antibody and siRNA-based CD63 inhibition studies indicate a potential role for CD63 following proviral integration. Further, we show that CD63 expression is key for efficient replication in primary CD4⁺ T cells, complementing our prior studies with primary human macrophages and immortalized cell lines.
  
  
  CONCLUSIONS
  Collectively, these findings indicate that CD63 may support Env-mediated fusion as well as a late (post-integration) step in the HIV-1 replication cycle.
authors: Guangyu
authors: G
authors: Li
authors: Mark A
authors: MA
authors: Endsley
authors: Anoma
authors: A
authors: Somasunderam
authors: Sonia L
authors: SL
authors: Gbota
authors: Maryann I
authors: MI
authors: Mbaka
authors: James L
authors: JL
authors: Murray
authors: Department of Internal Medicine, Division of Infectious Diseases, School of Medicine, University of Texas Medical Branch, Galveston, Texas 77555-0435, USA. mrfergus@utmb.edu.
authors: Monique R
authors: MR
authors: Ferguson
mesh_terms: D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D015497:HIV-1 / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D060149:Tetraspanin 30 / Q000378:metabolism*; D059470:Tetraspanins / Q000378:metabolism*; D053586:Virus Internalization; D014779:Virus Replication
chemical_list: C554586:CD63 protein, human; D060149:Tetraspanin 30; D059470:Tetraspanins