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Okuma H, Saijo-Hamano Y, Yamada H, Sherif AA, Hashizaki E, Sakai N, Kato T, Imasaki T, Kikkawa S, Nitta E, Sasai M, Abe T, Sugihara F, Maniwa Y, Kosako H, Takei K, Standley DM, Yamamoto M, Nitta R. Structural basis of Irgb6 inactivation by Toxoplasma gondii through the phosphorylation of switch I. Genes Cells 2024; 29:17-38. [PMID: 37984375 DOI: 10.1111/gtc.13080] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 10/12/2023] [Accepted: 10/29/2023] [Indexed: 11/22/2023]
Abstract
Irgb6 is a priming immune-related GTPase (IRG) that counteracts Toxoplasma gondii. It is known to be recruited to the low virulent type II T. gondii parasitophorous vacuole (PV), initiating cell-autonomous immunity. However, the molecular mechanism by which immunity-related GTPases become inactivated after the parasite infection remains obscure. Here, we found that Thr95 of Irgb6 is prominently phosphorylated in response to low virulent type II T. gondii infection. We observed that a phosphomimetic T95D mutation in Irgb6 impaired its localization to the PV and exhibited reduced GTPase activity in vitro. Structural analysis unveiled an atypical conformation of nucleotide-free Irgb6-T95D, resulting from a conformational change in the G-domain that allosterically modified the PV membrane-binding interface. In silico docking corroborated the disruption of the physiological membrane binding site. These findings provide novel insights into a T. gondii-induced allosteric inactivation mechanism of Irgb6.
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Affiliation(s)
- Hiromichi Okuma
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Yumiko Saijo-Hamano
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hiroshi Yamada
- Department of Neuroscience, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Aalaa Alrahman Sherif
- Department of Genome Informatics, Research Institute for Microbial Diseases, Osaka, Japan
- Laboratory of Systems Immunology, WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | - Emi Hashizaki
- Laboratory of Immunoparasitology, Osaka University, Osaka, Japan
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka, Japan
| | | | - Takaaki Kato
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Tsuyoshi Imasaki
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Satoshi Kikkawa
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Eriko Nitta
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Miwa Sasai
- Laboratory of Immunoparasitology, Osaka University, Osaka, Japan
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka, Japan
| | - Tadashi Abe
- Department of Neuroscience, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Fuminori Sugihara
- Core Instrumentation Facility, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan
| | - Yoshimasa Maniwa
- Division of Thoracic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan
| | - Hidetaka Kosako
- Division of Cell Signaling, Fujii Memorial Institute of Medical Sciences, Tokushima University, Tokushima, Japan
| | - Kohji Takei
- Department of Neuroscience, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan
| | - Daron M Standley
- Department of Genome Informatics, Research Institute for Microbial Diseases, Osaka, Japan
- Laboratory of Systems Immunology, WPI Immunology Frontier Research Center, Osaka University, Osaka, Japan
| | - Masahiro Yamamoto
- Laboratory of Immunoparasitology, Osaka University, Osaka, Japan
- Department of Immunoparasitology, Research Institute for Microbial Diseases, Osaka, Japan
| | - Ryo Nitta
- Division of Structural Medicine and Anatomy, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
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Ha HJ, Kim JH, Lee GH, Kim S, Park HH. Structural basis of IRGB10 oligomerization by GTP hydrolysis. Front Immunol 2023; 14:1254415. [PMID: 37705969 PMCID: PMC10495984 DOI: 10.3389/fimmu.2023.1254415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 08/11/2023] [Indexed: 09/15/2023] Open
Abstract
Immunity-related GTPase B10 (IRGB10) is a crucial member of the interferon (IFN)-inducible GTPases and plays a vital role in host defense mechanisms. Following infection, IRGB10 is induced by IFNs and functions by liberating pathogenic ligands to activate the inflammasome through direct disruption of the pathogen membrane. Despite extensive investigation into the significance of the cell-autonomous immune response, the precise molecular mechanism underlying IRGB10-mediated microbial membrane disruption remains elusive. Herein, we present two structures of different forms of IRGB10, the nucleotide-free and GppNHp-bound forms. Based on these structures, we identified that IRGB10 exists as a monomer in nucleotide-free and GTP binding states. Additionally, we identified that GTP hydrolysis is critical for dimer formation and further oligomerization of IRGB10. Building upon these observations, we propose a mechanistic model to elucidate the working mechanism of IRGB10 during pathogen membrane disruption.
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Affiliation(s)
- Hyun Ji Ha
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
| | - Ju Hyeong Kim
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul, Republic of Korea
| | - Gwan Hee Lee
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul, Republic of Korea
| | - Subin Kim
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul, Republic of Korea
| | - Hyun Ho Park
- College of Pharmacy, Chung-Ang University, Seoul, Republic of Korea
- Department of Global Innovative Drugs, Graduate School of Chung-Ang University, Seoul, Republic of Korea
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