title: Identification of SERPINB1 as a physiological inhibitor of human granzyme H.
abstract: The granzyme/perforin pathway is a major mechanism for cytotoxic lymphocytes to eliminate virus-infected and tumor cells. The balance between activation and inhibition of the proteolytic cascade must be tightly controlled to avoid self damage. Granzyme H (GzmH) is constitutively expressed in NK cells and induces target cell death; however, how GzmH activity is regulated remains elusive. We reported earlier the crystal structures of inactive D102N-GzmH alone and in complex with its synthetic substrate and inhibitor, as well as defined the mechanisms of substrate recognition and enzymatic activation. In this study, we identified SERPINB1 as a potent intracellular inhibitor for GzmH. Upon cleavage of the reactive center loop at Phe(343), SERPINB1 forms an SDS-stable covalent complex with GzmH. SERPINB1 overexpression suppresses GzmH- or LAK cell-mediated cytotoxicity. We determined the crystal structures of active GzmH and SERPINB1 (LM-DD mutant) in the native conformation to 3.0- and 2.9-Å resolution, respectively. Molecular modeling reveals the possible conformational changes in GzmH for the suicide inhibition. Our findings provide new insights into the inhibitory mechanism of SERPINB1 against human GzmH.
authors.affiliation: Chinese Academy of Sciences Key Laboratory of Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.forename: Lianfeng
authors.initials: L
authors.lastname: Wu
authors.forename: Shengwu
authors.initials: S
authors.lastname: Liu
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xuan
authors.initials: X
authors.lastname: Yang
authors.forename: Pingping
authors.initials: P
authors.lastname: Zhu
authors.forename: Honglian
authors.initials: H
authors.lastname: Zhang
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Jizhong
authors.initials: J
authors.lastname: Lou
authors.forename: Pingsheng
authors.initials: P
authors.lastname: Liu
authors.forename: Liang
authors.initials: L
authors.lastname: Tong
authors.forename: Fei
authors.initials: F
authors.lastname: Sun
authors.forename: Zusen
authors.initials: Z
authors.lastname: Fan
mesh_terms: D002384:Catalysis; D045744:Cell Line, Tumor; D002850:Chromatography, Gel; D018360:Crystallography, X-Ray; D003594:Cytoplasmic Granules / Q000201:enzymology; D003602:Cytotoxicity, Immunologic; D005822:Genetic Vectors; D053804:Granzymes / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D015979:Killer Cells, Lymphokine-Activated / Q000276:immunology; D008958:Models, Molecular; D009363:Neoplasm Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D011993:Recombinant Fusion Proteins / Q000502:physiology; D015843:Serpins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D013329:Structure-Activity Relationship
chemical_list: D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; D015843:Serpins; C075177:SERPINB1 protein, human; C069434:GZMH protein, human; D053804:Granzymes