title: HIV-1 Tat enters T cells using coated pits before translocating from acidified endosomes and eliciting biological responses.
abstract: The HIV-1 Tat protein is secreted by infected cells. Extracellular Tat can affect bystander uninfected T cells and induce numerous biological responses such as apoptosis and cytokine secretion. Tat is likely involved in several immune disorders during AIDS. Nevertheless, it is not known whether Tat triggers cell responses directly upon binding to signaling receptors at the plasma membrane or after delivery to the cytosol. The pathway that enables Tat to reach the cytosol is also unclear. Here we visualized Tat within T-cell-coated pits and endosomes. Moreover, inhibitors of clathrin/AP-2-mediated uptake such as chlorpromazine, activated RhoA, or dominant-negative mutants of Eps15, intersectin, dynamin, or rab5 impaired Tat delivery to the cytosol by preventing its endocytosis. Molecules neutralizing low endosomal pH or Hsp90 inhibitors abolished Tat entry at a later stage by blocking its endosomal translocation, as directly shown using a cell-free translocation assay. Finally, endosomal pH neutralization prevented Tat from inducing T-cell responses such as NF-kappaB activation, apoptosis, and interleukin secretion, indicating that cytosolic delivery is required for Tat signaling. Hence, Tat enters T cells essentially like diphtheria toxin, using clathrin-mediated endocytosis before low-pH-induced and Hsp90-assisted endosomal translocation. Cell responses are then induced from the cytosol.
authors.affiliation: UMR 5539 CNRS, Département Biologie-Santé, Case 107, Université Montpellier II, 34095 Montpellier Cedex 5, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Vendeville
authors.forename: Fabienne
authors.initials: F
authors.lastname: Rayne
authors.forename: Anne
authors.initials: A
authors.lastname: Bonhoure
authors.forename: Nadir
authors.initials: N
authors.lastname: Bettache
authors.forename: Philippe
authors.initials: P
authors.lastname: Montcourrier
authors.forename: Bruno
authors.initials: B
authors.lastname: Beaumelle
mesh_terms: D002966:Clathrin / Q000378:metabolism; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism / Q000648:ultrastructure / Q000821:virology*; D003600:Cytosol / Q000000981:diagnostic imaging / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism / Q000821:virology*; D015696:Gene Products, tat / Q000032:analysis / Q000378:metabolism*; D015497:HIV-1; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D020672:I-kappa B Proteins / Q000032:analysis / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D019169:Jurkat Cells; D000072000:NF-KappaB Inhibitor alpha; D009687:Nuclear Proteins / Q000494:pharmacology; D021381:Protein Transport / Q000187:drug effects; D013601:T-Lymphocytes / Q000378:metabolism / Q000821:virology*; D015533:Transcriptional Activation; D014168:Transferrin / Q000032:analysis; D014463:Ultrasonography; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: C501959:BANF1 protein, human; D002966:Clathrin; D004268:DNA-Binding Proteins; D015696:Gene Products, tat; D018841:HSP90 Heat-Shock Proteins; D020672:I-kappa B Proteins; D007376:Interleukin-2; D016209:Interleukin-8; C000606204:NFKBIA protein, human; D009687:Nuclear Proteins; D014168:Transferrin; D054322:tat Gene Products, Human Immunodeficiency Virus; D000072000:NF-KappaB Inhibitor alpha; D020696:rab5 GTP-Binding Proteins