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Eitan E Zahavi,
Joshua A Lieberman,
Michael S Donnenberg,
Mor Nitzan, Kobi Baruch,
Ilan Rosenshine,
Jerrold R Turner,
Naomi Melamed-Book,
Naomi Feinstein,
Efrat Zlotkin-Rivkin,
Benjamin Aroeti
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Eitan E Zahavi,
Joshua A Lieberman,
Michael S Donnenberg,
Mor Nitzan, Kobi Baruch,
Ilan Rosenshine,
Jerrold R Turner,
Naomi Melamed-Book,
Naomi Feinstein,
Efrat Zlotkin-Rivkin,
Benjamin Aroeti
[show abstract]
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ABSTRACT: Enteropathogenic Escherichia coli (EPEC) is an important human pathogen that causes acute infantile diarrhea. The type IV bundle-forming pili (BFP) of typical EPEC strains are dynamic fibrillar organelles that can extend out and retract into the bacterium. The bfpF gene encodes for BfpF, a protein that promotes pili retraction. The BFP are involved in bacterial autoaggregation and in mediating the initial adherence of the bacterium with its host cell. Importantly, BFP retraction is implicated in virulence in experimental human infection. How pili retraction contributes to EPEC pathogenesis at the cellular level remains largely obscure, however. In this study, an effort has been made to address this question using engineered EPEC strains with induced BFP retraction capacity. We show that the retraction is important for tight-junction disruption and, to a lesser extent, actin-rich pedestal formation by promoting efficient translocation of bacterial protein effectors into the host cells. A model is proposed whereby BFP retraction permits closer apposition between the bacterial and the host cell surfaces, thus enabling timely and effective introduction of bacterial effectors into the host cell via the type III secretion apparatus. Our studies hence suggest novel insights into the involvement of pili retraction in EPEC pathogenesis.
Molecular biology of the cell 05/2011; 22(14):2436-47. · 5.98 Impact Factor
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Kobi Baruch,
Lihi Gur-Arie,
Chen Nadler,
Simi Koby,
Gal Yerushalmi,
Yinon Ben-Neriah,
Orli Yogev,
Eitan Shaulian,
Chen Guttman,
Raz Zarivach,
Ilan Rosenshine
[show abstract]
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ABSTRACT: Two major arms of the inflammatory response are the NF-κB and c-Jun N-terminal kinase (JNK) pathways. Here, we show that enteropathogenic Escherichia coli (EPEC) employs the type III secretion system to target these two signalling arms by injecting host cells with two effector proteins, NleC and NleD. We provide evidence that NleC and NleD are Zn-dependent endopeptidases that specifically clip and inactivate RelA (p65) and JNK, respectively, thus blocking NF-κB and AP-1 activation. We show that NleC and NleD co-operate and complement other EPEC effectors in accomplishing maximal inhibition of IL-8 secretion. This is a remarkable example of a pathogen using multiple effectors to manipulate systematically the host inflammatory response signalling network.
The EMBO Journal 01/2011; 30(1):221-31. · 9.20 Impact Factor
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Kobi Baruch,
Lihi Gur-Arie,
Chen Nadler,
Simi Koby,
Gal Yerushalmi,
Yinon Ben-Neriah,
Orli Yogev,
Eitan Shaulian,
Chen Guttman,
Raz Zarivach,
Ilan Rosenshine
[show abstract]
[hide abstract]
ABSTRACT: Two major arms of the inflammatory response are the NF-κB and c-Jun N-terminal kinase (JNK) pathways. Here, we show that enteropathogenic
The EMBO Journal 11/2010; 30(1):221-231. · 9.20 Impact Factor
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Chen Nadler, Kobi Baruch,
Simi Kobi,
Erez Mills,
Gili Haviv,
Marganit Farago,
Irit Alkalay,
Sina Bartfeld,
Thomas F Meyer,
Yinon Ben-Neriah,
Ilan Rosenshine
[show abstract]
[hide abstract]
ABSTRACT: The complex host-pathogen interplay involves the recognition of the pathogen by the host's innate immune system and countermeasures taken by the pathogen. Detection of invading bacteria by the host leads to rapid activation of the transcription factor NF-kappaB, followed by inflammation and eradication of the intruders. In response, some pathogens, including enteropathogenic Escherichia coli (EPEC), acquired means of blocking NF-kappaB activation. We show that inhibition of NF-kappaB activation by EPEC involves the injection of NleE into the host cell. Importantly, we show that NleE inhibits NF-kappaB activation by preventing activation of IKKbeta and consequently the degradation of the NF-kappaB inhibitor, IkappaB. This NleE activity is enhanced by, but is not dependent on, a second injected effector, NleB. In conclusion, this study describes two effectors, NleB and NleE, with no similarity to other known proteins, used by pathogens to manipulate NF-kappaB signaling pathways.
PLoS Pathogens 01/2010; 6(1):e1000743. · 9.13 Impact Factor
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Yulia Shifrin,
Adi Peleg,
Ophir Ilan,
Chen Nadler,
Simi Kobi, Kobi Baruch,
Gal Yerushalmi,
Tatiana Berdichevsky,
Shoshy Altuvia,
Maya Elgrably-Weiss,
Cecilia Abe,
Stuart Knutton,
Chihiro Sasakawa,
Jennifer M Ritchie,
Matthew K Waldor,
Ilan Rosenshine
[show abstract]
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ABSTRACT: Enterohemorrhagic and enteropathogenic Escherichia coli (EHEC and EPEC, respectively) strains represent a major global health problem. Their virulence is mediated by the concerted activity of an array of virulence factors including toxins, a type III protein secretion system (TTSS), pili, and others. We previously showed that EPEC O127 forms a group 4 capsule (G4C), and in this report we show that EHEC O157 also produces a G4C, whose assembly is dependent on the etp, etk, and wzy genes. We further show that at early time points postinfection, these G4Cs appear to mask surface structures including intimin and the TTSS. This masking inhibited the attachment of EPEC and EHEC to tissue-cultured epithelial cells, diminished their capacity to induce the formation of actin pedestals, and attenuated TTSS-mediated protein translocation into host cells. Importantly, we found that Ler, a positive regulator of intimin and TTSS genes, represses the expression of the capsule-related genes, including etp and etk. Thus, the expression of TTSS and G4C is conversely regulated and capsule production is diminished upon TTSS expression. Indeed, at later time points postinfection, the diminishing capsule no longer interferes with the activities of intimin and the TTSS. Notably, by using the rabbit infant model, we found that the EHEC G4C is required for efficient colonization of the rabbit large intestine. Taken together, our results suggest that temporal expression of the capsule, which is coordinated with that of the TTSS, is required for optimal EHEC colonization of the host intestine.
Journal of bacteriology 08/2008; 190(14):5063-74. · 3.94 Impact Factor
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ABSTRACT: The emergence of pathogenic strains of enteric bacteria and their adaptation to unique niches are associated with the acquisition of foreign DNA segments termed 'genetic islands'. We explored these islands for the occurrence of small RNA (sRNA) encoding genes. Previous systematic screens for enteric bacteria sRNAs were mainly carried out using the laboratory strain Escherichia coli K12, leading to the discovery of approximately 80 new sRNA genes. These searches were based on conservation within closely related members of enteric bacteria and thus, sRNAs, unique to pathogenic strains were excluded. Here we describe the identification and characterization of 19 novel unique sRNA genes encoded within the 'genetic islands' of the virulent strain Salmonella typhimurium. We show that the expression of many of the island-encoded genes is associated with stress conditions and stationary phase. Several of these sRNA genes are induced when Salmonella resides within macrophages. One sRNA, IsrJ, was further examined and found to affect the translocation efficiency of virulence-associated effector proteins into nonphagocytic cells. In addition, we report that unlike the majority of the E. coli sRNAs that are trans regulators, many of the island-encoded sRNAs affect the expression of cis-encoded genes. Our study suggests that the island encoded sRNA genes play an important role within the network that regulates bacterial adaptation to environmental changes and stress conditions and thus controls virulence.
Nucleic Acids Research 05/2008; 36(6):1913-27. · 8.03 Impact Factor
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ABSTRACT: Bacteria use type III secretion systems (TTSS) to translocate effector proteins into host cells. Better understanding of the TTSS and its effectors' functions will require assays to measure their activities in vivo and in real time. We designed a real-time, high-throughput translocation assay that utilizes fusions of effector genes to the beta-lactamase reporter gene, positioned under the effector's native promoter and chromosomal location. Using this assay, we simultaneously and quantitatively analyzed the translocation kinetics of six core enteropathogenic E. coli effectors, EspF, EspG, EspH, EspZ, Map, and Tir. A distinct order in the efficiencies of effector translocation was observed. Translocation efficiency was determined by multiple factors, including the intrabacterial effector concentration, effector-chaperone interactions, the efficiency of bacterial attachment to the host cells, and possibly also by a translocation autoinhibition mechanism. The described real-time translocation assay could be easily adapted for varied applications in the study of bacterial pathogenesis.
Cell host & microbe 03/2008; 3(2):104-13. · 13.02 Impact Factor
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Adi Peleg,
Yulia Shifrin,
Ophir Ilan,
Chen Nadler-Yona,
Shani Nov,
Simi Koby, Kobi Baruch,
Shoshy Altuvia,
Maya Elgrably-Weiss,
Cecilia M Abe,
Stuart Knutton,
Mark A Saper,
Ilan Rosenshine
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ABSTRACT: Escherichia coli produces polysaccharide capsules that, based on their mechanisms of synthesis and assembly, have been classified into four groups. The group 4 capsule (G4C) polysaccharide is frequently identical to that of the cognate lipopolysaccharide O side chain and has, therefore, also been termed the O-antigen capsule. The genes involved in the assembly of the group 1, 2, and 3 capsules have been described, but those required for G4C assembly remained obscure. We found that enteropathogenic E. coli (EPEC) produces G4C, and we identified an operon containing seven genes, ymcD, ymcC, ymcB, ymcA, yccZ, etp, and etk, which are required for formation of the capsule. The encoded proteins appear to constitute a polysaccharide secretion system. The G4C operon is absent from the genomes of enteroaggregative E. coli and uropathogenic E. coli. E. coli K-12 contains the G4C operon but does not express it, because of the presence of IS1 at its promoter region. In contrast, EPEC, enterohemorrhagic E. coli, and Shigella species possess an intact G4C operon.
Journal of Bacteriology 09/2005; 187(15):5259-66. · 3.83 Impact Factor
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Chen Nadler, Kobi Baruch,
Simi Kobi,
Erez Mills,
Gili Haviv,
Marganit Farago,
Irit Alkalay,
Sina Bartfeld,
Thomas F Meyer,
Yinon Ben-Neriah,
Ilan Rosenshine
[show abstract]
[hide abstract]
ABSTRACT: The complex host-pathogen interplay involves the recognition of the pathogen by the host's innate immune system and countermeasures taken by the pathogen. Detection of invading bacteria by the host leads to rapid activation of the transcription factor NF-kappa B, followed by inflammation and eradication of the intruders. In response, some pathogens, including enteropathogenic Escherichia coli (EPEC), acquired means of blocking NF-kappa B activation. We show that inhibition of NF-kappa B activation by EPEC involves the injection of NleE into the host cell. Importantly, we show that NleE inhibits NF-kappa B activation by preventing activation of IKK beta and consequently the degradation of the NF-kappa B inhibitor, I kappa B. This NleE activity is enhanced by, but is not dependent on, a second injected effector, NleB. In conclusion, this study describes two effectors, NleB and NleE, with no similarity to other known proteins, used by pathogens to manipulate NF-kappa B signaling pathways.
PLoS Pathogens, v.6 (2010).
