title: HIV-1 Nef induces proinflammatory state in macrophages through its acidic cluster domain: involvement of TNF alpha receptor associated factor 2.
abstract: BACKGROUND
  HIV-1 Nef is a virulence factor that plays multiple roles during HIV replication. Recently, it has been described that Nef intersects the CD40 signalling in macrophages, leading to modification in the pattern of secreted factors that appear able to recruit, activate and render T lymphocytes susceptible to HIV infection. The engagement of CD40 by CD40L induces the activation of different signalling cascades that require the recruitment of specific tumor necrosis factor receptor-associated factors (i.e. TRAFs). We hypothesized that TRAFs might be involved in the rapid activation of NF-κB, MAPKs and IRF-3 that were previously described in Nef-treated macrophages to induce the synthesis and secretion of proinflammatory cytokines, chemokines and IFNβ to activate STAT1, -2 and -3.
  
  
  RESULTS
  Searching for possible TRAF binding sites on Nef, we found a TRAF2 consensus binding site in the AQEEEE sequence encompassing the conserved four-glutamate acidic cluster. Here we show that all the signalling effects we observed in Nef treated macrophages depend on the integrity of the acidic cluster. In addition, Nef was able to interact in vitro with TRAF2, but not TRAF6, and this interaction involved the acidic cluster. Finally silencing experiments in THP-1 monocytic cells indicate that both TRAF2 and, surprisingly, TRAF6 are required for the Nef-induced tyrosine phosphorylation of STAT1 and STAT2.
  
  
  CONCLUSIONS
  Results reported here revealed TRAF2 as a new possible cellular interactor of Nef and highlighted that in monocytes/macrophages this viral protein is able to manipulate both the TRAF/NF-κB and TRAF/IRF-3 signalling axes, thereby inducing the synthesis of proinflammatory cytokines and chemokines as well as IFNβ.
authors: Department of Biology, University Roma Tre, Rome, Italy.
authors: Giorgio
authors: G
authors: Mangino
authors: Zulema A
authors: ZA
authors: Percario
authors: Gianna
authors: G
authors: Fiorucci
authors: Gabriele
authors: G
authors: Vaccari
authors: Filippo
authors: F
authors: Acconcia
authors: Cristiano
authors: C
authors: Chiarabelli
authors: Stefano
authors: S
authors: Leone
authors: Alessia
authors: A
authors: Noto
authors: Florian A
authors: FA
authors: Horenkamp
authors: Santiago
authors: S
authors: Manrique
authors: Giovanna
authors: G
authors: Romeo
authors: Fabio
authors: F
authors: Polticelli
authors: Matthias
authors: M
authors: Geyer
authors: Elisabetta
authors: E
authors: Affabris
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018925:Chemokines / Q000096:biosynthesis; D016384:Consensus Sequence / Q000235:genetics; D005786:Gene Expression Regulation; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology*; D018836:Inflammation Mediators / Q000378:metabolism; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D016899:Interferon-beta / Q000096:biosynthesis; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism / Q000473:pathology*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019814:Myristic Acid / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D050791:STAT Transcription Factors / Q000378:metabolism; D013329:Structure-Activity Relationship; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D054311:nef Gene Products, Human Immunodeficiency Virus / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D018925:Chemokines; C494232:IRF3 protein, human; D018836:Inflammation Mediators; D050838:Interferon Regulatory Factor-3; D015850:Interleukin-6; D016328:NF-kappa B; D050791:STAT Transcription Factors; D047992:TNF Receptor-Associated Factor 2; D048029:TNF Receptor-Associated Factor 6; D014409:Tumor Necrosis Factor-alpha; D054311:nef Gene Products, Human Immunodeficiency Virus; D019814:Myristic Acid; D019000:Phosphotyrosine; D016899:Interferon-beta