title: A bacterial E3 ubiquitin ligase IpaH9.8 targets NEMO/IKKgamma to dampen the host NF-kappaB-mediated inflammatory response.
abstract: NF-kappaB (nuclear factor kappaB) has a pivotal role in many cellular processes, including the inflammatory and immune responses and, therefore, its activation is tightly regulated by the IKK (IkappaB kinase) complex and by IkappaBalpha degradation. When Shigella bacteria multiply within epithelial cells they release peptidoglycans, which are recognized by Nod1 and stimulate the NF-kappaB pathway, thus leading to a severe inflammatory response. Here, we show that IpaH9.8, a Shigella effector possessing E3 ligase activity, dampens the NF-kappaB-mediated inflammatory response to the bacterial infection in a unique way. IpaH9.8 interacts with NEMO/IKKgamma and ABIN-1, a ubiquitin-binding adaptor protein, promoting ABIN-1-dependent polyubiquitylation of NEMO. Consequently, polyubiquitylated NEMO undergoes proteasome-dependent degradation, which perturbs NF-kappaB activation. As NEMO is essential for NF-kappaB activation, we propose that the polyubiquitylation and degradation of NEMO during Shigella infection is a new bacterial strategy to modulate host inflammatory responses.
authors.affiliation: Department of Microbiology and Immunology, University of Tokyo, 4-6-1, Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ashida
authors.forename: Minsoo
authors.initials: M
authors.lastname: Kim
authors.forename: Marc
authors.initials: M
authors.lastname: Schmidt-Supprian
authors.forename: Averil
authors.initials: A
authors.lastname: Ma
authors.forename: Michinaga
authors.initials: M
authors.lastname: Ogawa
authors.forename: Chihiro
authors.initials: C
authors.lastname: Sasakawa
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D007249:Inflammation / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011014:Pneumonia / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C491731:IKBKG protein, human; D016328:NF-kappa B; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; C117046:TNIP1 protein, human; D025801:Ubiquitin; C063500:ipaH protein, Shigella flexneri; D008156:Luciferases; D051550:I-kappa B Kinase