The Enteropathogenic E. coli Effector EspB Facilitates Microvillus Effacing and Antiphagocytosis by Inhibiting Myosin Function

Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan.
Cell host & microbe (Impact Factor: 12.19). 01/2008; 2(6):383-92. DOI: 10.1016/j.chom.2007.09.012
Source: PubMed

ABSTRACT Enteropathogenic Escherichia coli (EPEC) destroys intestinal microvilli and suppresses phagocytosis by injecting effectors into infected cells through a type III secretion system (TTSS). EspB, a component of the TTSS, is also injected into the cytoplasm of host cells. However, the physiological functions of EspB within the host cell cytoplasm remain unclear. We show that EspB binds to myosins, which are a superfamily of proteins that interact with actin filaments and mediate essential cellular processes, including microvillus formation and phagocytosis. EspB inhibits the interaction of myosins with actin, and an EspB mutant that lacks the myosin-binding region maintained its TTSS function but could not induce microvillus effacing or suppress phagocytosis. Moreover, the myosin-binding region of EspB is essential for Citrobacter rodentium, an EPEC-related murine pathogen, to efficiently infect mice. These results suggest that EspB inhibits myosin functions and thereby facilitates efficient infection by EPEC.

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Available from: Hiroshi Handa, Aug 27, 2015
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    • "EHEC colonizes the intestine with the aid of a type III secretion system (T3SS) which enables the bacteria to establish a tight adherence to enterocytes and to modify their cytoskeletal proteins, leading to the characteristic attaching and effacing lesion [8]. EspB is a T3SS protein that plays a central role in mediating the EHEC enterocyte adherence [8] [9] [10] [11] [12]. Moreover, EspB is highly immunogenic in human patients [13] [14] [15] and in infected or vaccinated animals [13] [16]. "
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    ABSTRACT: Enterohemorrhagic Escherichia coli (EHEC) have been responsible for several outbreaks of hemolytic-uremic syndrome (HUS) worldwide. HUS is the most common cause of acute renal failure in children and results in fatalities as high as 50% in the elderly. Currently, neither a specific treatment nor a vaccine is available for EHEC. Lactococcus lactis is a generally regarded as safe “GRAS” bacterium that offers a valuable platform for oral vaccine delivery. Toward the development of an oral vaccine against EHEC, we have previously constructed a recombinant L. lactis strain expressing the EHEC antigen, EspB in the cytoplasmic compartment. However, oral immunization of mice with this strain induced weak priming of the immune system. This outcome was attributed to the rather low levels of EspB expressed by this recombinant strain. Therefore, in the present study we optimized the expression of EspB in L. lactis by secreting the antigen either under constitutive or nisin-inducible control. Indeed, oral immunization of mice with the EspB-secreting strains successfully induced specific mucosal and systemic antibody responses. These responses were associated with mixed Th1/Th2 cell responses in Peyer's Patches and mesenteric lymph nodes. Moreover, immunized mice exhibited significant protection against E. coli O157:H7 colonization, as indicated by the reduced amount and/or duration of the bacterial fecal shedding. Our results demonstrate the protective potential of EspB as an oral vaccine against EHEC infection. Additionally, the study demonstrates the efficient delivery of recombinant EspB by the “GRAS” bacterium, L. lactis. The safety profile of L. lactis as a vaccine vehicle can particularly be beneficial to children and elderly as high-risk groups for HUS incidence.
    Vaccine 05/2014; 32(31). DOI:10.1016/j.vaccine.2014.05.054 · 3.49 Impact Factor
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    • "*Indicates statistical significance (P < 0.05) using oneway ANOVA followed by Tukey's multiple comparison test of TirMC- Ub transfected cells compared to untreated and TirMC transfected host cells. proposed to block EPEC uptake by macrophages via a Tir-independent mechanism (Celli et al., 2000; Iizumi et al., 2007; Dong et al., 2010). It is not understood whether this is the case with infections of nonphagocytes but could constitute another tactic to avoid internalization . "
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    ABSTRACT: Enteropathogenic Escherichia coli (EPEC) is an extracellular pathogen that alters many host subcellular components during its infectious processes. We have previously shown that EPEC hijacks a large assortment of host cell endocytic components and uses these proteins to form protruding structures called "pedestals" rather than triggering internalization of the bacteria. Other invasive pathogens that also recruit similar endocytic components have been shown to enter their host cells on the ubiquitylation of their host cell receptors. Therefore, we hypothesize that EPEC remains extracellular by maintaining its receptor, translocated intimin receptor (Tir), in an unubiquitylated state. Using immunoprecipitation-Western blots, we demonstrate no association of ubiquitin with Tir. To further elucidate the effect Tir ubiquitylation would have on EPEC during their infections, we engineered Tir-ubiquitin fusion constructs, expressed them in host epithelial cells, and infected them with Δtir EPEC. We found these cells induced a significant increase in EPEC invasion as compared with cells that expressed the Tir construct that lacked ubiquitin conjugation. Our results indicate that the lack of EPEC receptor ubiquitylation is a contributing factor that these microbes use to prevent their internalization into epithelial cells.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 08/2012; 295(8):1230-8. DOI:10.1002/ar.22503 · 1.53 Impact Factor
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    • "IgG-and complement receptor-mediated phagocytosis, but the mechanism remains completely unknown (Marches et al, 2008). The TTSS translocator protein EspB does this by targeting the host myosin (Iizumi et al, 2007), but it is neither solely responsible nor sufficient for the antiphagocytosis function of EPEC (Dean and Kenny, 2009). Therefore, EspH might function together with EspF and EspB to block macrophage phagocytosis by targeting different host processes, thereby promoting bacterial survival in the host. "
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    ABSTRACT: Bacterial pathogens often harbour a type III secretion system (TTSS) that injects effector proteins into eukaryotic cells to manipulate host processes and cause diseases. Identification of host targets of bacterial effectors and revealing their mechanism of actions are crucial for understating bacterial virulence. We show that EspH, a type III effector conserved in enteric bacterial pathogens including enteropathogenic Escherichia coli (EPEC), enterohaemorrhagic E. coli and Citrobacter rodentium, markedly disrupts actin cytoskeleton structure and induces cell rounding up when ectopically expressed or delivered into HeLa cells by the bacterial TTSS. EspH inactivates host Rho GTPase signalling pathway at the level of RhoGEF. EspH directly binds the DH-PH domain in multiple RhoGEFs, which prevents their binding to Rho and thereby inhibits nucleotide exchange-mediated Rho activation. Consistently, infection of mouse macrophages with EPEC harbouring EspH attenuates phagocytosis of the bacteria as well as FcgammaR-mediated phagocytosis. EspH represents the first example of targeting RhoGEFs by bacterial effectors, and our results also reveal an unprecedented mechanism used by enteric pathogens to counteract the host defence system.
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