title: Shigella IpaH7.8 E3 ubiquitin ligase targets glomulin and activates inflammasomes to demolish macrophages.
abstract: When nucleotide-binding oligomerization domain-like receptors (NLRs) sense cytosolic-invading bacteria, they induce the formation of inflammasomes and initiate an innate immune response. In quiescent cells, inflammasome activity is tightly regulated to prevent excess inflammation and cell death. Many bacterial pathogens provoke inflammasome activity and induce inflammatory responses, including cell death, by delivering type III secreted effectors, the rod component flagellin, and toxins. Recent studies indicated that Shigella deploy multiple mechanisms to stimulate NLR inflammasomes through type III secretion during infection. Here, we show that Shigella induces rapid macrophage cell death by delivering the invasion plasmid antigen H7.8 (IpaH7.8) enzyme 3 (E3) ubiquitin ligase effector via the type III secretion system, thereby activating the NLR family pyrin domain-containing 3 (NLRP3) and NLR family CARD domain-containing 4 (NLRC4) inflammasomes and caspase-1 and leading to macrophage cell death in an IpaH7.8 E3 ligase-dependent manner. Mice infected with Shigella possessing IpaH7.8, but not with Shigella possessing an IpaH7.8 E3 ligase-null mutant, exhibited enhanced bacterial multiplication. We defined glomulin/flagellar-associated protein 68 (GLMN) as an IpaH7.8 target involved in IpaH7.8 E3 ligase-dependent inflammasome activation. This protein originally was identified through its association with glomuvenous malformations and more recently was described as a member of a Cullin ring ligase inhibitor. Modifying GLMN levels through overexpression or knockdown led to reduced or augmented inflammasome activation, respectively. Macrophages stimulated with lipopolysaccharide/ATP induced GLMN puncta that localized with the active form of caspase-1. Macrophages from GLMN(+/-) mice were more responsive to inflammasome activation than those from GLMN(+/+) mice. Together, these results highlight a unique bacterial adaptation that hijacks inflammasome activation via interactions between IpaH7.8 and GLMN.
authors.affiliation: Department of Microbiology and Immunology, Division of Bacterial Infection Biology, and Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109;
authors.forename: Shiho
authors.initials: S
authors.lastname: Suzuki
authors.affiliation: Department of Microbiology and Immunology, Division of Bacteriology, Department of Infectious Diseases Control, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan;
authors.forename: Hitomi
authors.initials: H
authors.lastname: Mimuro
authors.affiliation: Department of Microbiology and Immunology, Division of Bacterial Infection Biology, and.
authors.forename: Minsoo
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Microbiology and Immunology.
authors.forename: Michinaga
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Department of Microbiology and Immunology, Division of Bacterial Infection Biology, and.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ashida
authors.affiliation: Department of Microbiology and Immunology.
authors.forename: Takahito
authors.initials: T
authors.lastname: Toyotome
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109;
authors.forename: Luigi
authors.initials: L
authors.lastname: Franchi
authors.affiliation: Department of Microbiology and Immunology.
authors.forename: Masato
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Microbiology and Immunology, Division of Bacteriology, Department of Infectious Diseases Control, International Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, Tokyo 108-8639, Japan;
authors.forename: Takahito
authors.initials: T
authors.lastname: Sanada
authors.affiliation: Department of Microbiology and Immunology, Department of Molecular Bacteriology and Immunology, Graduate School of Medicine, University of the Ryukyus, Okinawa 903-0125, Japan;
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Department of Microbiology, Hyogo College of Medicine, Hyogo 663-8501, Japan;
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tsutsui
authors.affiliation: Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109;
authors.forename: Gabriel
authors.initials: G
authors.lastname: Núñez
authors.affiliation: Department of Microbiology and Immunology, Division of Bacterial Infection Biology, and Nippon Institute for Biological Science, Tokyo 198-0024, Japan; and Medical Mycology Research Center, Chiba University, Chiba 260-8673, Japan sasakawa@ims.u-tokyo.ac.jp.
authors.forename: Chihiro
authors.initials: C
authors.lastname: Sasakawa
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D005260:Female; D057809:HEK293 Cells; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D015151:Immunoblotting; D058847:Inflammasomes / Q000378:metabolism*; D019169:Jurkat Cells; D008264:Macrophages / Q000378:metabolism* / Q000382:microbiology; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012763:Shigella flexneri / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D020798:Two-Hybrid System Techniques
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D058847:Inflammasomes; D009124:Muscle Proteins; C493011:glomulin protein, mouse; C063500:ipaH protein, Shigella flexneri
keywords: TTSS effector; pyroptosis