Granzyme B is a novel interleukin-18 converting enzyme

• Published in: Journal of dermatological science 2010-08, Vol.59 (2), p.129-135
• Main Authors: Omoto, Youichi, Yamanaka, Keiichi, Tokime, Kazuya, Kitano, Shigehisa, Kakeda, Masato, Akeda, Tomoko, Kurokawa, Ichiro, Gabazza, Esteban C, Tsutsui, Hiroko, Katayama, Naoyuki, Yamanishi, Kiyofumi, Nakanishi, Kenji, Mizutani, Hitoshi
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Apoptosis; Apoptosis - physiology; Caspase 1 - pharmacology; CD8-Positive T-Lymphocytes - cytology; CD8-Positive T-Lymphocytes - drug effects; CD8-Positive T-Lymphocytes - metabolism; Cells, Cultured; Cytokine; Dermatology; Granzymes - metabolism; Granzymes - pharmacology; Humans; Inflammation; Inflammation - physiopathology; Interferon-gamma - metabolism; Interleukin-18 - metabolism; Keratinocytes - cytology; Keratinocytes - drug effects; Keratinocytes - metabolism; Leukocytes, Mononuclear - cytology; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - metabolism; Molecular Sequence Data; Skin
• ISSN: 0923-1811; 1873-569X
• DOI: 10.1016/j.jdermsci.2010.05.004

Abstract Background Granzyme B (GrB) is recognized to induce apoptosis; however, little is known about its possible role in other biological events. IL-18, a potent inflammatory cytokine, is produced as an inactive precursor (proIL-18). Several cells, including monocytes/macrophage lineage and non-hematopoietic cells such as keratinocytes, produce proIL-18. ProIL-18 requires appropriate processing to become active. Caspase-1 is the authentic IL-18 processing enzyme and is essential for IL-18 release from monocyte/macrophage lineage cells. However, caspase-1 is absent in non-hematopoietic cells, suggesting that there is another candidate to cleave proIL-18 except for caspase-1. Objective GrB can invade and be active in cytoplasm of non-hematopoietic cells via perforin, therefore we investigated whether GrB converts proIL-18 into the biologically active form. Methods Recombinant proIL-18 (rproIL-18) was produced and purified for protease reaction with GrB; this incubate was evaluated by immunoblotting. Biological activity of the proteolytic fragment cleaved by GrB was determined by IFN-γ assay using KG-1 cells. IFN-γ induction was also analyzed between extracts from GrB(+)/caspase-1(−) human CD8+ T cells and proIL-18 from normal human keratinocytes (NHK). Results The proteolytic fragment that GrB cleaved proIL-18 had the same sequence and biological activity compared with mature IL-18 cleaved by caspase-1. Culture extracts from CD8+ T cells was able to cleave proIL-18 into authentic mature IL-18. IFN-γ induction was also detected in NHK treated with CD8+ T cells. Conclusion GrB is a potent IL-18 converting enzyme and suggest that GrB secreted by CTLs and/or NK cells may initiate IL-18 release from target cells, leading to the development of inflammation.