title: VAMP4- and VAMP7-expressing vesicles are both required for cytotoxic granule exocytosis in NK cells.
abstract: NK cells eliminate cancer and virus-infected cells through their cytolytic activity. The last step in NK-cell cytotoxicity, resulting in exocytosis of granule content, requires fusion of lytic granules with the plasma membrane. Proteins from the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family mediate membrane fusion events in the cell. Here, we show that NK cells express all members of the R-SNARE subgroup. Two of these R-SNARE proteins, VAMP4 and VAMP7, colocalize with lytic granules during cytotoxic interactions. However, only VAMP7 associates with perforin-containing granules in nonactivated cells, indicating that the two VAMPs have different functions in exocytosis. Using both the tumor NK-cell line YTS and the peripheral NK cells, we show that the disruption of expression of either VAMP4 or VAMP7 inhibits the release of lytic granules and severely impairs NK-cell cytotoxic activity. Furthermore, VAMP7 but not VAMP4 is involved in IFN-γ secretion in NK cells, indicating that VAMP7 is involved in many fusion processes and thus plays a more general function in NK-cell activity than VAMP4.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Konrad
authors.initials: K
authors.lastname: Krzewski
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Gil-Krzewska
authors.forename: James
authors.initials: J
authors.lastname: Watts
authors.forename: Joel N H
authors.initials: JN
authors.lastname: Stern
authors.forename: Jack L
authors.initials: JL
authors.lastname: Strominger
mesh_terms: D015153:Blotting, Western; D015550:Cell Degranulation / Q000276:immunology*; D002460:Cell Line; D003594:Cytoplasmic Granules / Q000276:immunology / Q000378:metabolism; D003602:Cytotoxicity, Immunologic / Q000276:immunology*; D005089:Exocytosis; D006801:Humans; D007694:Killer Cells, Natural / Q000276:immunology* / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology; D018613:Microscopy, Confocal; D050683:R-SNARE Proteins / Q000276:immunology* / Q000378:metabolism; D022142:Secretory Vesicles / Q000276:immunology* / Q000378:metabolism
chemical_list: D050683:R-SNARE Proteins; C476456:VAMP4 protein, human; C121241:VAMP7 protein, human