title: The Shigella flexneri effector OspI deamidates UBC13 to dampen the inflammatory response.
abstract: Many bacterial pathogens can enter various host cells and then survive intracellularly, transiently evade humoral immunity, and further disseminate to other cells and tissues. When bacteria enter host cells and replicate intracellularly, the host cells sense the invading bacteria as damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) by way of various pattern recognition receptors. As a result, the host cells induce alarm signals that activate the innate immune system. Therefore, bacteria must modulate host inflammatory signalling and dampen these alarm signals. How pathogens do this after invading epithelial cells remains unclear, however. Here we show that OspI, a Shigella flexneri effector encoded by ORF169b on the large plasmid and delivered by the type ΙΙΙ secretion system, dampens acute inflammatory responses during bacterial invasion by suppressing the tumour-necrosis factor (TNF)-receptor-associated factor 6 (TRAF6)-mediated signalling pathway. OspI is a glutamine deamidase that selectively deamidates the glutamine residue at position 100 in UBC13 to a glutamic acid residue. Consequently, the E2 ubiquitin-conjugating activity required for TRAF6 activation is inhibited, allowing S. flexneri OspI to modulate the diacylglycerol-CBM (CARD-BCL10-MALT1) complex-TRAF6-nuclear-factor-κB signalling pathway. We determined the 2.0 Å crystal structure of OspI, which contains a putative cysteine-histidine-aspartic acid catalytic triad. A mutational analysis showed this catalytic triad to be essential for the deamidation of UBC13. Our results suggest that S. flexneri inhibits acute inflammatory responses in the initial stage of infection by targeting the UBC13-TRAF6 complex.
authors.affiliation: Department of Infectious Disease Control, International Research Center for Infectious Diseases, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Takahito
authors.initials: T
authors.lastname: Sanada
authors.forename: Minsoo
authors.initials: M
authors.lastname: Kim
authors.forename: Hitomi
authors.initials: H
authors.lastname: Mimuro
authors.forename: Masato
authors.initials: M
authors.lastname: Suzuki
authors.forename: Michinaga
authors.initials: M
authors.lastname: Ogawa
authors.forename: Akiho
authors.initials: A
authors.lastname: Oyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ashida
authors.forename: Taira
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Koyama
authors.forename: Shinya
authors.initials: S
authors.lastname: Nagai
authors.forename: Yuri
authors.initials: Y
authors.lastname: Shibata
authors.forename: Jin
authors.initials: J
authors.lastname: Gohda
authors.forename: Jun-ichiro
authors.initials: J
authors.lastname: Inoue
authors.forename: Tsunehiro
authors.initials: T
authors.lastname: Mizushima
authors.forename: Chihiro
authors.initials: C
authors.lastname: Sasakawa
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000581:Amidohydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D000074018:B-Cell CLL-Lymphoma 10 Protein; D055162:Biocatalysis; D020169:Caspases / Q000378:metabolism; D020134:Catalytic Domain / Q000235:genetics; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000378:metabolism; D004252:DNA Mutational Analysis; D004075:Diglycerides / Q000037:antagonists & inhibitors / Q000378:metabolism; D004405:Dysentery, Bacillary / Q000382:microbiology; D018698:Glutamic Acid / Q000378:metabolism; D005973:Glutamine / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006639:Histidine / Q000378:metabolism; D006801:Humans; D007113:Immunity, Innate; D007249:Inflammation / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000074884:Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D012763:Shigella flexneri / Q000201:enzymology* / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D048029:TNF Receptor-Associated Factor 6 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000074018:B-Cell CLL-Lymphoma 10 Protein; C118591:BCL10 protein, human; D004075:Diglycerides; D016328:NF-kappa B; D009363:Neoplasm Proteins; D048029:TNF Receptor-Associated Factor 6; D037521:Virulence Factors; D005973:Glutamine; D001224:Aspartic Acid; D018698:Glutamic Acid; D006639:Histidine; D044763:Ubiquitin-Conjugating Enzymes; D020169:Caspases; C400109:MALT1 protein, human; D000074884:Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 Protein; D000581:Amidohydrolases; D003545:Cysteine