title: The scaffolding protein Dlg1 is a negative regulator of cell-free virus infectivity but not of cell-to-cell HIV-1 transmission in T cells.
abstract: BACKGROUND
  Cell-to-cell virus transmission of Human immunodeficiency virus type-1 (HIV-1) is predominantly mediated by cellular structures such as the virological synapse (VS). The VS formed between an HIV-1-infected T cell and a target T cell shares features with the immunological synapse (IS). We have previously identified the human homologue of the Drosophila Discs Large (Dlg1) protein as a new cellular partner for the HIV-1 Gag protein and a negative regulator of HIV-1 infectivity. Dlg1, a scaffolding protein plays a key role in clustering protein complexes in the plasma membrane at cellular contacts. It is implicated in IS formation and T cell signaling, but its role in HIV-1 cell-to-cell transmission was not studied before.
  
  
  RESULTS
  Kinetics of HIV-1 infection in Dlg1-depleted Jurkat T cells show that Dlg1 modulates the replication of HIV-1. Single-cycle infectivity tests show that this modulation does not take place during early steps of the HIV-1 life cycle. Immunofluorescence studies of Dlg1-depleted Jurkat T cells show that while Dlg1 depletion affects IS formation, it does not affect HIV-1-induced VS formation. Co-culture assays and quantitative cell-to-cell HIV-1 transfer analyses show that Dlg1 depletion does not modify transfer of HIV-1 material from infected to target T cells, or HIV-1 transmission leading to productive infection via cell contact. Dlg1 depletion results in increased virus yield and infectivity of the viral particles produced. Particles with increased infectivity present an increase in their cholesterol content and during the first hours of T cell infection these particles induce higher accumulation of total HIV-1 DNA.
  
  
  CONCLUSIONS
  Despite its role in the IS formation, Dlg1 does not affect the VS and cell-to-cell spread of HIV-1, but plays a role in HIV-1 cell-free virus transmission. We propose that the effect of Dlg1 on HIV-1 infectivity is at the stage of virus entry.
authors.affiliation: INSERM, U1016, Institut Cochin, Paris, France.
authors.forename: Patrycja
authors.initials: P
authors.lastname: Nzounza
authors.forename: Maxime
authors.initials: M
authors.lastname: Chazal
authors.forename: Chloé
authors.initials: C
authors.lastname: Guedj
authors.forename: Alain
authors.initials: A
authors.lastname: Schmitt
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Massé
authors.forename: Clotilde
authors.initials: C
authors.lastname: Randriamampita
authors.forename: Claudine
authors.initials: C
authors.lastname: Pique
authors.forename: Bertha Cecilia
authors.initials: BC
authors.lastname: Ramirez
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002450:Cell Communication; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D018920:Coculture Techniques; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism; D000074288:Discs Large Homolog 1 Protein; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D054992:Immunological Synapses / Q000378:metabolism / Q000821:virology; D019169:Jurkat Cells; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D034622:RNA Interference; D013601:T-Lymphocytes / Q000378:metabolism* / Q000648:ultrastructure / Q000821:virology; D014779:Virus Replication / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D004279:DNA, Viral; D000074288:Discs Large Homolog 1 Protein; D008565:Membrane Proteins; D049452:Green Fluorescent Proteins; D002784:Cholesterol