Enterohemorrhagic Escherichia coli Adhesins
- Authors: Brian D. McWilliams1, Alfredo G. Torres2
- Editors: Vanessa Sperandio3, Carolyn J. Hovde4
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VIEW AFFILIATIONS HIDE AFFILIATIONSAffiliations: 1: Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555; 2: Department of Pathology and Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX 77555; 3: University of Texas Southwestern Medical Center, Dallas, TX; 4: University of Idaho, Moscow, ID
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Received 30 April 2013 Accepted 29 July 2013 Published 20 June 2014
- Correspondence: Alfredo G. Torres, [email protected]

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Abstract:
Adhesins are a group of proteins in enterohemorrhagic Escherichia coli (EHEC) that are involved in the attachment or colonization of this pathogen to abiotic (plastic or steel) and biological surfaces, such as those found in bovine and human intestines. This review provides the most up-to-date information on these essential adhesion factors, summarizing important historical discoveries and analyzing the current and future state of this research. In doing so, the proteins intimin and Tir are discussed in depth, especially regarding their role in the development of attaching and effacing lesions and in EHEC virulence. Further, a series of fimbrial proteins (Lpf1, Lpf2, curli, ECP, F9, ELF, Sfp, HCP, and type 1 fimbria) are also described, emphasizing their various contributions to adherence and colonization of different surfaces and their potential use as genetic markers in detection and classification of different EHEC serotypes. This review also discusses the role of several autotransporter proteins (EhaA-D, EspP, Saa and Sab, and Cah), as well as other proteins associated with adherence, such as flagella, EibG, Iha, and OmpA. While these proteins have all been studied to varying degrees, all of the adhesins summarized in this article have been linked to different stages of the EHEC life cycle, making them good targets for the development of more effective diagnostics and therapeutics.
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Citation: McWilliams B, Torres A. 2014. Enterohemorrhagic Escherichia coli Adhesins. Microbiol Spectrum 2(3):EHEC-0003-2013. doi:10.1128/microbiolspec.EHEC-0003-2013.




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Abstract:
Adhesins are a group of proteins in enterohemorrhagic Escherichia coli (EHEC) that are involved in the attachment or colonization of this pathogen to abiotic (plastic or steel) and biological surfaces, such as those found in bovine and human intestines. This review provides the most up-to-date information on these essential adhesion factors, summarizing important historical discoveries and analyzing the current and future state of this research. In doing so, the proteins intimin and Tir are discussed in depth, especially regarding their role in the development of attaching and effacing lesions and in EHEC virulence. Further, a series of fimbrial proteins (Lpf1, Lpf2, curli, ECP, F9, ELF, Sfp, HCP, and type 1 fimbria) are also described, emphasizing their various contributions to adherence and colonization of different surfaces and their potential use as genetic markers in detection and classification of different EHEC serotypes. This review also discusses the role of several autotransporter proteins (EhaA-D, EspP, Saa and Sab, and Cah), as well as other proteins associated with adherence, such as flagella, EibG, Iha, and OmpA. While these proteins have all been studied to varying degrees, all of the adhesins summarized in this article have been linked to different stages of the EHEC life cycle, making them good targets for the development of more effective diagnostics and therapeutics.

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Figures

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FIGURE 1
Illustration of the EHEC prototype strain EDL933 LEE pathogenicity island. The five LEE operons are depicted, specifically emphasizing gene-encoded proteins associated with adhesion and A/E lesion formation. They include the genes encoding the regulatory proteins Ler, GrlA, and GrlR; the translocated receptor protein Tir; and the adhesin protein intimin.

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FIGURE 2
Time line and proposed roles of major fimbrial/afimbrial adhesin proteins in EHEC. In (A), Lpf is interacting with the extracellular membrane (ECM) proteins, such as laminin, collagen IV, and fibronectin. After the initial interaction with the intestine is established, EHEC is able to closely attach to the host cell (B) through an interaction of the surface protein intimin with the translocated receptor protein Tir and nucleolin. In (C), the interaction between Tir and intimin is established, initiating a host-cell actin rearrangement via participation of the translocated bacterial protein EspFu and the recruitment of several host proteins. In (D), ECP and HCP are proposed to interact with the surface of host intestinal cells, perhaps strengthening the colonization through the formation of microcolonies and/or biofilms. Further, curli is shown to contribute in the establishment of biofilms, though an interaction with ECP and HCP is not demonstrated. Finally in (E), dominant curli expression has been proposed as detrimental for the survival of EHEC in the intestine, suggesting that this surface structure might become important for the pathogen interaction with abiotic surfaces and during colonization of the surface of vegetable and plant leaves.
Tables

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TABLE 1
Major characteristics of the EHEC fimbrial proteins

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TABLE 2
EHEC autotransporters and their functions
Supplemental Material
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