title: NK cell activation by dendritic cells is dependent on LFA-1-mediated induction of calcium-calmodulin kinase II: inhibition by HIV-1 Tat C-terminal domain.
abstract: In this study, we show that binding to autologous dendritic cells (DC) induces a calcium influx in NK cells, followed by activation of the calcium-calmodulin kinase II (CAMKII), release of perforin and granzymes, and IFN-gamma secretion. CAMKII is induced via LFA-1: indeed, oligomerization of LFA-1 leads to CAMKII induction in NK cells. Moreover, release of lytic enzymes and cytotoxic activity is strongly reduced by masking LFA-1 or by adding CAMKII inhibitors such as KN62 and KN93, at variance with the inactive compound KN92. NK cell-mediated lysis of DC and IFN-gamma release by NK cells upon NK/DC contact are inhibited by exogenous HIV-1 Tat: the protein blocks calcium influx and impairs CAMKII activation elicited via LFA-1 in NK cells, eventually inhibiting degranulation. Experiments performed with synthetic, overlapping Tat-derived peptides showed that the C-terminal domain of the protein is responsible for inhibition. Finally, both KN62 and Tat reduced the extension of NK/DC contacts, possibly affecting NK cell granule polarization toward the target. These data provide evidence that exogenous Tat inhibits NK cell activation occurring upon contact with DC: this mechanism might contribute to the impairment of natural immunity in HIV-1 infection.
authors.affiliation: Laboratory of Immunology, National Institute for Cancer Research, Genoa, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Poggi
authors.forename: Roberta
authors.initials: R
authors.lastname: Carosio
authors.forename: Grazia Maria
authors.initials: GM
authors.lastname: Spaggiari
authors.forename: Claudio
authors.initials: C
authors.lastname: Fortis
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Tambussi
authors.forename: Giacomo
authors.initials: G
authors.lastname: Dell'Antonio
authors.forename: Elena
authors.initials: E
authors.lastname: Dal Cin
authors.forename: Anna
authors.initials: A
authors.lastname: Rubartelli
authors.forename: M Raffaella
authors.initials: MR
authors.lastname: Zocchi
mesh_terms: D020013:Calcium Signaling; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D015550:Cell Degranulation; D002478:Cells, Cultured; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic; D003713:Dendritic Cells / Q000276:immunology* / Q000648:ultrastructure; D004789:Enzyme Activation; D015696:Gene Products, tat / Q000737:chemistry / Q000494:pharmacology*; D015497:HIV-1; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology* / Q000648:ultrastructure; D008213:Lymphocyte Activation; D016169:Lymphocyte Function-Associated Antigen-1 / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D017434:Protein Structure, Tertiary; D012697:Serine Endopeptidases / Q000378:metabolism; D014407:Tumor Cells, Cultured; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015696:Gene Products, tat; D016169:Lymphocyte Function-Associated Antigen-1; D008562:Membrane Glycoproteins; D052899:Pore Forming Cytotoxic Proteins; D054322:tat Gene Products, Human Immunodeficiency Virus; D054353:Perforin; D007371:Interferon-gamma; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D012697:Serine Endopeptidases