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dc.contributor.authorPathe, Claudio
dc.date.accessioned2018-11-15T16:45:45Z
dc.date.available2018-11-15T16:45:45Z
dc.date.submitted2018-08-01
dc.identifier.urihttps://www.repository.cam.ac.uk/handle/1810/285110
dc.description.abstractShigella flexneri is a highly adapted pathogen that invades the host cytosol and causes bacillary dysentery. Shigella has evolved powerful countermeasures to disarm host defense mechanisms; amongst them a family of twelve bacterial E3 ubiquitin ligases (IpaH) that are structurally unrelated to eukaryotic enzymes. IpaH ligases are injected into the host cytosol via the bacterial type III secretion system (T3SS) to manipulate the host cell and counteract anti-bacterial defense pathways. My work demonstrated that IFN-induced guanylate-binding proteins (GBPs) are novel targets for IpaH9.8. GBPs inhibit actin-dependent motility and cell-to-cell spread of bacteria unless they are ubiquitylated by IpaH9.8 and consequently degraded by the proteasome. IpaH9.8 targets GBP1, GBP2, and GBP4, thereby causing a transient poly-ubiquitin coat comprising K48 and K27-linked chains around S. flexneri, which leads to the proteasome-dependent destruction of existing GBP coats and the re-establishment of bacterial motility and cell-to-cell spread. So far, ubiquitylation of bacteria has mostly been associated with anti-bacterial autophagy or immune signaling. However, the ubiquitin coat assembled around intracellular Shigella by IpaH effectors, in particular IpaH9.8, serves a pro-bacterial function, the first observed so far. In addition, I characterized IpaH1.4 and IpaH2.5 for their ability to prevent NF-κB activation by targeting LUBAC. I found that IpaH1.4 specifically binds the LUBAC component HOIP and mediates its proteasomal degradation, thus abolishing linear ubiquitylation of bacteria and consecutive NF-κB activation via NEMO and autophagy induction via optineurin. Lastly, I identified novel potential ubiquitylation targets for IpaH effectors in human cells using a mass spectrometry-based approach. The resulting IpaH interactome presents the groundwork for further investigations and will help to identify potentially unknown cellular defense mechanisms that are antagonized by Shigella flexneri.
dc.description.sponsorshipBoehringer Ingelheim Fonds
dc.language.isoen
dc.rightsAll rights reserved
dc.rightsAll Rights Reserveden
dc.rights.urihttps://www.rioxx.net/licenses/all-rights-reserved/en
dc.subjectcell-autonomous immunity
dc.subjectShigella flexneri
dc.subjectE3 ubiquitin ligase
dc.subjecthost-pathogen interaction
dc.titleFunctional analysis of Shigella encoded IpaH E3 ubiquitin ligases in cell-autonomous immunity
dc.typeThesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnameDoctor of Philosophy (PhD)
dc.publisher.institutionUniversity of Cambridge
dc.publisher.departmentMRC Laboratory of Molecular Biology
dc.date.updated2018-11-14T15:06:11Z
dc.identifier.doi10.17863/CAM.32480
dc.publisher.collegeGonville & Caius
dc.type.qualificationtitleDoctor of Philosophy
cam.supervisorRandow, Felix
cam.thesis.fundingtrue
rioxxterms.freetoread.startdate2024-08-01


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