Structural Insights into Ail-Mediated Adhesion in Yersinia pestis

Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-8030, USA.
Structure (Impact Factor: 5.62). 11/2011; 19(11):1672-82. DOI: 10.1016/j.str.2011.08.010
Source: PubMed


Ail is an outer membrane protein from Yersinia pestis that is highly expressed in a rodent model of bubonic plague, making it a good candidate for vaccine development. Ail is important for attaching to host cells and evading host immune responses, facilitating rapid progression of a plague infection. Binding to host cells is important for injection of cytotoxic Yersinia outer proteins. To learn more about how Ail mediates adhesion, we solved two high-resolution crystal structures of Ail, with no ligand bound and in complex with a heparin analog called sucrose octasulfate. We identified multiple adhesion targets, including laminin and heparin, and showed that a 40 kDa domain of laminin called LG4-5 specifically binds to Ail. We also evaluated the contribution of laminin to delivery of Yops to HEp-2 cells. This work constitutes a structural description of how a bacterial outer membrane protein uses a multivalent approach to bind host cells.

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    • "The extracellular matrix (ECM) proteins fibronectin and laminin are substrates for Y. pestis Ail and these Ail-ECM interactions are important for adhesion to host cells and Yop delivery [12], [13], [35]. The crystal structure of Ail from Y. pestis has been determined [13] and it belongs to the OmpX family of proteins described as having a flattened β-barrel with four extracellular loops extending above the surface of the bacteria [36], [37]. The four extracellular loops of Y. pestis Ail contain 10–21 amino acids each. "
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    ABSTRACT: The Yersinia pestis adhesin Ail mediates host cell binding and facilitates delivery of cytotoxic Yop proteins. Ail from Y. pestis and Y. pseudotuberculosis is identical except for one or two amino acids at positions 43 and 126 depending on the Y. pseudotuberculosis strain. Ail from Y. pseudotuberculosis strain YPIII has been reported to lack host cell binding ability, thus we sought to determine which amino acid difference(s) are responsible for the difference in cell adhesion. Y. pseudotuberculosis YPIII Ail expressed in Escherichia coli bound host cells, albeit at ∼50% the capacity of Y. pestis Ail. Y. pestis Ail single mutants, Ail-E43D and Ail-F126V, both have decreased adhesion and invasion in E. coli when compared to wild-type Y. pestis Ail. Y. pseudotuberculosis YPIII Ail also had decreased binding to the Ail substrate fibronectin, relative to Y. pestis Ail in E. coli. When expressed in Y. pestis, there was a 30-50% decrease in adhesion and invasion depending on the substitution. Ail-mediated Yop delivery by both Y. pestis Ail and Y. pseudotuberculosis Ail were similar when expressed in Y. pestis, with only Ail-F126V giving a statistically significant reduction in Yop delivery of 25%. In contrast to results in E. coli and Y. pestis, expression of Ail in Y. pseudotuberculosis led to no measurable adhesion or invasion, suggesting the longer LPS of Y. pseudotuberculosis interferes with Ail cell-binding activity. Thus, host context affects the binding activities of Ail and both Y. pestis and Y. pseudotuberculosis Ail can mediate cell binding, cell invasion and facilitate Yop delivery.
    Full-text · Article · Dec 2013 · PLoS ONE
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    • "YitA and YipA were detected using anti-YitA or anti-YipA serum. Mouse antiserum against the constitutively expressed Y. pestis outer membrane protein Ail [37] was used for a sample loading control. Goat anti-rabbit IgG or goat anti-mouse IgG antibodies conjugated to alkaline phosphatase (Life Technologies) and BCIP/NBT-Blue liquid substrate (Sigma-Aldrich, St. Louis, MO) were used to visualize protein bands. "
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    ABSTRACT: Background Toxin complex (Tc) family proteins were first identified as insecticidal toxins in Photorhabdus luminescens and have since been found in a wide range of bacteria. The genome of Yersinia pestis, the causative agent of bubonic plague, contains a locus that encodes the Tc protein homologues YitA, YitB, YitC, and YipA and YipB. Previous microarray data indicate that the Tc genes are highly upregulated by Y. pestis while in the flea vector; however, their role in the infection of fleas and pathogenesis in the mammalian host is unclear. Results We show that the Tc proteins YitA and YipA are highly produced by Y. pestis while in the flea but not during growth in brain heart infusion (BHI) broth at the same temperature. Over-production of the LysR-type regulator YitR from an exogenous plasmid increased YitA and YipA synthesis in broth culture. The increase in production of YitA and YipA correlated with the yitR copy number and was temperature-dependent. Although highly synthesized in fleas, deletion of the Tc proteins did not alter survival of Y. pestis in the flea or prevent blockage of the proventriculus. Furthermore, YipA was found to undergo post-translational processing and YipA and YitA are localized to the outer membrane of Y. pestis. YitA was also detected by immunofluorescence microscopy on the surface of Y. pestis. Both YitA and YipA are produced maximally at low temperature but persist for several hours after transfer to 37°C. Conclusions Y. pestis Tc proteins are highly expressed in the flea but are not essential for Y. pestis to stably infect or produce a transmissible infection in the flea. However, YitA and YipA localize to the outer membrane and YitA is exposed on the surface, indicating that at least YitA is present on the surface when Y. pestis is transmitted into the mammalian host from the flea.
    Full-text · Article · Dec 2012 · BMC Microbiology
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    • "Ail-mediated binding of Y. pestis or E. coli to the regions between the host cells during in vitro cell culturing indicates that the protein also interacts with the components of the ECM (Kolodziejek et al., 2007; Felek and Krukonis, 2009; Tsang et al., 2010; Yamashita et al., 2011). Purified Ail and Ail-expressing E. coli bind specifically to laminin, fibronectin, negatively charged HSPGs, but not collagen I or IV (Tsang et al., 2010; Yamashita et al., 2011). In vitro models employing human cell lines and Y. pestis show that the bacterium binds to fibronectin and laminin via Ail (Tsang et al., 2010; Yamashita et al., 2011); however, Ail is not the only protein that participates in binding of fibronectin by Y. pestis (Tsang et al., 2010). "
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    ABSTRACT: Yersinia pestis is one of the most virulent bacteria identified. It is the causative agent of plague-a systemic disease that has claimed millions of human lives throughout history. Y. pestis survival in insect and mammalian host species requires fine-tuning to sense and respond to varying environmental cues. Multiple Y. pestis attributes participate in this process and contribute to its pathogenicity and highly efficient transmission between hosts. These include factors inherited from its enteric predecessors; Y. enterocolitica and Y. pseudotuberculosis, as well as phenotypes acquired or lost during Y. pestis speciation. Representatives of a large Enterobacteriaceae Ail/OmpX/PagC/Lom family of outer membrane proteins (OMPs) are found in the genomes of all pathogenic Yersiniae. This review describes the current knowledge regarding the role of Ail in Y. pestis pathogenesis and virulence. The pronounced role of Ail in the following areas are discussed (1) inhibition of the bactericidal properties of complement, (2) attachment and Yersinia outer proteins (Yop) delivery to host tissue, (3) prevention of PMNL recruitment to the lymph nodes, and (4) inhibition of the inflammatory response. Finally, Ail homologs in Y. enterocolitica and Y. pseudotuberculosis are compared to illustrate differences that may have contributed to the drastic bacterial lifestyle change that shifted Y. pestis from an enteric to a vector-born systemic pathogen.
    Full-text · Article · Aug 2012 · Frontiers in Cellular and Infection Microbiology
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