EspFU, an Enterohemorrhagic E. Coli Secreted Effector, Hijacks Mammalian Actin Assembly Proteins by Molecular Mimicry and Repetition: A Dissertation
Authors
Lai, YuShuan (Cindy)Faculty Advisor
John M. Leong, MD, PhDAcademic Program
MD/PhDUMass Chan Affiliations
Molecular Genetics and MicrobiologyDocument Type
Doctoral DissertationPublication Date
2014-04-25Keywords
Dissertations, UMMSActin Cytoskeleton
Actins
Calpain
Cytoskeletal Proteins
Enterohemorrhagic Escherichia coli
Escherichia coli Infections
Escherichia coli Proteins
Microvilli
Actin Cytoskeleton
Actins
Calpain
Cytoskeletal Proteins
Enterohemorrhagic Escherichia coli
Escherichia coli Infections
Escherichia coli Proteins
Microvilli
Bacterial Infections and Mycoses
Bacteriology
Cellular and Molecular Physiology
Microbial Physiology
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Show full item recordAbstract
Enterohemorrhagic E. coli (EHEC) is a major cause of food borne diarrheal illness worldwide. While disease symptoms are usually self-resolving and limited to severe gastroenteritis with bloody diarrhea, EHEC infection can lead to a life threatening complication known as Hemolytic Uremic Syndrome (HUS), which strikes children disproportionately and is the leading cause of kidney failure in children. Upon infection of gut epithelia, EHEC produces characteristic lesions called actin pedestals. These striking formations involve dramatic rearrangement of host cytoskeletal proteins. EHEC hijacks mammalian signaling pathways to cause destruction of microvilli and rebuilds the actin cytoskeleton underneath sites of bacterial attachment. Here, we present a brief study on a host factor, Calpain, involved in microvilli effacement, and an in depth investigation on a bacterial factor, EspFU, required for actin pedestal formation in intestinal cell models. Calpain is activated by both EHEC and the related pathogen, enteropathogenic E. coli (EPEC), during infection and facilitates microvilli disassembly by cleavage of a key membrane-cytoskeleton anchoring substrate, Ezrin. Actin pedestal formation is facilitated by the injection of two bacterial effectors, Tir and EspFU, into host cells, which work in concert to manipulate the host actin nucleators N-WASP and Arp2/3. EspFU hijacks key host signaling proteins N-WASP and IRTKS by mimetic displacement and has evolved to outcompete mammalian host ligands. Multiple repeats of key functional domains of EspFU are essential for actin pedestal activity through proper localization and competition against the an abundant host factor Eps8 for binding to IRTKS.DOI
10.13028/M2HW2HPermanent Link to this Item
http://hdl.handle.net/20.500.14038/32074Notes
Copyright by (Cindy) YuShuan Lai 2014 All Rights Reserved
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Copyright is held by the author, with all rights reserved.ae974a485f413a2113503eed53cd6c53
10.13028/M2HW2H
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EspFU is a translocated EHEC effector that interacts with Tir and N-WASP and promotes Nck-independent actin assemblyCampellone, Kenneth Geno; Robbins, Douglas; Leong, John M. (2004-08-07)Several microbial pathogens including enteropathogenic E. coli (EPEC) exploit mammalian tyrosine-kinase signaling cascades to recruit Nck adaptor proteins and activate N-WASP-Arp2/3-mediated actin assembly. To promote localized actin "pedestal formation," EPEC translocates the bacterial effector protein Tir into the plasma membrane, where it is tyrosine-phosphorylated and binds Nck. Enterohemorrhagic E. coli (EHEC) also generates Tir-dependent pedestals, but in the absence of phosphotyrosines and Nck recruitment. To identify additional EHEC effectors that stimulate phosphotyrosine-independent actin assembly, we systematically generated EHEC mutants containing specific deletions in putative pathogenicity-islands. Among 0.33 Mb of deleted sequences, only one ORF was critical for pedestal formation. It lies within prophage-U, and encodes a protein similar to the known effector EspF. This proline-rich protein, EspFU, is the only EHEC effector of actin assembly absent from EPEC. Whereas EHEC Tir cannot efficiently recruit N-WASP or trigger actin polymerization, EspFU associates with Tir, binds N-WASP, and potently stimulates Nck-independent actin assembly.
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