title: Cytokine secretion is distinct from secretion of cytotoxic granules in NK cells.
abstract: NK cells are renowned for their ability to kill virally infected or transformed host cells by release of cytotoxic granules containing granzymes and perforin. NK cells also have important regulatory capabilities chiefly mediated by secretion of cytokines, such as IFN-gamma and TNF. The secretory pathway for the release of cytokines in NK cells is unknown. In this study, we show localization and trafficking of IFN-gamma and TNF in human NK cells in compartments and vesicles that do not overlap with perforin or other late endosome granule markers. Cytokines in post-Golgi compartments colocalized with markers of the recycling endosome (RE). REs are functionally required for cytokine release because inactivation of REs or mutation of RE-associated proteins Rab11 and vesicle-associated membrane protein-3 blocked cytokine surface delivery and release. In contrast, REs are not needed for release of perforin from preformed granules but may be involved at earlier stages of granule maturation. These findings suggest a new role for REs in orchestrating secretion in NK cells. We show that the cytokines IFN-gamma and TNF are trafficked and secreted via a different pathway than perforin. Although perforin granules are released in a polarized fashion at lytic synapses, distinct carriers transport both IFN-gamma and TNF to points all over the cell surface, including within the synapse, for nonpolarized release.
authors.affiliation: Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Esther
authors.initials: E
authors.lastname: Reefman
authors.forename: Jason G
authors.initials: JG
authors.lastname: Kay
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Wood
authors.forename: Carolin
authors.initials: C
authors.lastname: Offenhäuser
authors.forename: Darren L
authors.initials: DL
authors.lastname: Brown
authors.forename: Sandrine
authors.initials: S
authors.lastname: Roy
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Stanley
authors.forename: Pei Ching
authors.initials: PC
authors.lastname: Low
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Manderson
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Stow
mesh_terms: D000328:Adult; D002451:Cell Compartmentation / Q000276:immunology; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D016764:Cell Polarity / Q000276:immunology; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000276:immunology* / Q000378:metabolism*; D003601:Cytotoxicity Tests, Immunologic / Q000379:methods; D011992:Endosomes / Q000276:immunology / Q000378:metabolism; D006801:Humans; D054992:Immunological Synapses / Q000378:metabolism; D007371:Interferon-gamma / Q000096:biosynthesis / Q000378:metabolism*; D020014:K562 Cells; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism*; D008213:Lymphocyte Activation / Q000276:immunology; D054353:Perforin / Q000096:biosynthesis / Q000378:metabolism*; D021381:Protein Transport / Q000276:immunology; D022142:Secretory Vesicles / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D014409:Tumor Necrosis Factor-alpha; D054353:Perforin; D007371:Interferon-gamma