title: Cathepsin G enhances human natural killer cytotoxicity.
abstract: Cathepsin G is a serine protease located in the azurophil granules of neutrophils. In this study, we investigated the effect of cathepsin G on the functions of human natural killer (NK) cells in vitro. Cathepsin G enhanced NK cytotoxicity rapidly in a dose-dependent fashion. The ability to augment NK cytotoxicity was markedly reduced in the presence of the inhibitor, phenylmethanesulphonyl fluoride (PMSF) or chymostatin, demonstrating that the proteolytic activity of cathepsin G is essential for the induction of NK cytotoxicity. Granulocyte exocytosis is required for NK cell-dependent target killing. Cathepsin G induced the release of the granule enzyme, N-acetyl-beta-D-glucosaminidase, from human NK cells. Moreover, an increase in the cytosolic-free Ca2+ concentration was observed in NK cells after stimulation with cathepsin G. When human granulocytes were stimulated with cytochalasin B and N-formyl-methionyl-leucyl-phenylalanine (fMLP), cathepsin G was released. The cathepsin G released from granulocytes also caused enhancement of NK cytotoxicity. In the presence of serine protease inhibitor the supernatant including cathepsin G obtained from stimulated granulocytes did not enhance NK cytotoxicity, but the stimulated granulocytes did. Highly purified human NK cells treated with cathepsin G enhanced NK cytotoxicity, but NK-depleted lymphocytes did not, demonstrating that cathepsin G regulates NK cytotoxicity independently of other factors. We have shown recently that human cathepsin G binds to human NK cells. These combined data indicate that cathepsin G released from granulocytes binds to NK cells and augments NK cytotoxicity through its protease activity.
authors.affiliation: Department of Nutrition and Biochemistry, Institute of Public Health, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Y
authors.initials: Y
authors.lastname: Aoki
mesh_terms: D002118:Calcium / Q000378:metabolism; D056649:Cathepsin G; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis / Q000187:drug effects; D006098:Granulocytes / Q000276:immunology; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects* / Q000276:immunology; D009842:Oligopeptides / Q000494:pharmacology; D012697:Serine Endopeptidases / Q000494:pharmacology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D014105:Tosyl Compounds / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D009842:Oligopeptides; D015842:Serine Proteinase Inhibitors; D014105:Tosyl Compounds; C003614:4-toluenesulfonyl fluoride; C002101:chymostatin; D002403:Cathepsins; D012697:Serine Endopeptidases; C534094:CTSG protein, human; D056649:Cathepsin G; D002118:Calcium