title: The N-Terminal Region of HIV-1 Tat Protein Binds CD127 in Human CD8 T Cells to Target the Receptor for Down Regulation Through Tat's Basic Region.
abstract: We have previously shown that soluble HIV-1 Tat protein down regulates surface expression of the interleukin (IL)-7 receptor alpha-chain (CD127) on human CD8 T cells resulting in impaired T cell proliferation and cytolytic capacity. Once taken up by CD8 T cells, Tat translocates to the inner leaflet of the plasma membrane where it interacts with the cytoplasmic tail of CD127 inducing receptor internalization and degradation by the proteasome. Here we characterized the regions of Tat required to interact with CD127 and induce receptor down regulation from the cell surface. To do this, a series of histidine-tagged Tat deletion mutants were generated and expressed as purified soluble protein, or cloned into a DNA expression vector and transfected into primary human CD8 T cells and a CD127 expressing Jurkat cell line. Protein-protein interactions were assessed by co-immunoprecipitation. Substitution of the first 10 Nterminal residues or deletion of residues 17-21 prevented Tat from interacting with and down regulating CD127 from the cell surface. Deletion of the basic region also prevented Tat from down regulating CD127 but did not prevent Tat from binding to the receptor. Notably, an endogenously expressed Tat variant lacking the basic region caused an accumulation of CD127 at the cell surface. We propose a model where Tat interacts with CD127 via its N-terminal region and recruits cellular factors via its basic region to down regulate CD127 from the cell surface.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Sugden
authors.affiliation: Division of Infectious Diseases, The Ottawa Hospital, General Campus, 501 Smyth Road, Ottawa, Ontario, K1H 8L6, Canada. pmacpherson@ottawahospital.on.ca.
authors.forename: Paul A
authors.initials: PA
authors.lastname: MacPherson
mesh_terms: D000328:Adult; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D015870:Gene Expression; D015497:HIV-1 / Q000276:immunology / Q000502:physiology*; D006801:Humans; D057131:Immune Evasion; D007108:Immune Tolerance; D047468:Immunoprecipitation; D053699:Interleukin-7 Receptor alpha Subunit / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017384:Sequence Deletion; D014162:Transfection; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000378:metabolism*
chemical_list: D053699:Interleukin-7 Receptor alpha Subunit; D054322:tat Gene Products, Human Immunodeficiency Virus