A Type III Secretion System in Vibrio cholerae Translocates a Formin/Spire Hybrid-like Actin Nucleator to Promote Intestinal Colonization

Department of Microbiology and Molecular Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA.
Cell host & microbe (Impact Factor: 12.33). 05/2007; 1(2):95-107. DOI: 10.1016/j.chom.2007.03.005
Source: PubMed


We have previously characterized a non-O1, non-O139 Vibrio cholerae strain, AM-19226, that lacks the known virulence factors but contains components of a type III secretion system (T3SS). In this study, we demonstrated that the T3SS is functional and is required for intestinal colonization in the infant mouse model. We also identified VopF, which is conserved among T3SS-positive V. cholerae strains, as an effector containing both formin homology 1-like (FH1-like) and WASP homology 2 (WH2) domains. Translocation of VopF by V. cholerae or expression by transfection altered the actin cytoskeletal organization of the eukaryotic host cells. In vitro domain analysis indicated that both FH1-like and WH2 domains are required for actin nucleation and polymerization activity. These data correlate with in vivo data, suggesting that VopF-mediated alteration of actin polymerization homeostasis is required for efficient intestinal colonization by T3SS+V. cholerae in the infant mouse model.

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Available from: Vincent Tam, Mar 28, 2014
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    • "VopF and its ortholog VopL are pathogen effectors that are injected in host eukaryotic cells by the T3SS secretion system of Vibrio cholerae and Vibrio parahaemolyticus, respectively . Once internalized, VopF and VopL harness the actin cytoskeleton of the host and induce filopodia and stress fibers, respectively [Liverman et al., 2007; Tam et al., 2007]. These proteins are made of three adjacent WH2 domains assembled in a homodimer by a C-terminal dimerization domain, whose crystal structure has been solved in VopL [Namgoong et al., 2011; Yu et al., 2011]. "
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    ABSTRACT: WH2 domains are multifunctional regulators of actin assembly that can either sequester G-actin or allow polarized barbed end growth. They all bind similarly to a hydrophobic pocket at the barbed face of actin. Depending on their electrostatic environment, WH2 domains can nucleate actin assembly by facilitating the formation of pre-nuclei dimers along the canonical spontaneous assembly pathway. They also modulate filament barbed end dynamics in a versatile fashion, acting either as barbed end cappers or assisting barbed end growth like profilin or uncapping barbed ends and potentially mediating processive elongation like formins when they are dimerized. Tandem repeats of WH2 domains can sever filaments and either remain bound to created barbed ends like gelsolin, or strip off an ADP-actin subunit from the severed polymer end, depending on their relative affinity for terminal ADP-F-actin or ADP-G-actin. In summary, WH2 domains recapitulate all known elementary regulatory functions so far found in individual actin-binding proteins. By combining different discrete sets of these multifunctional properties, they acquire specific functions in various actin-based processes, and participate in activities as diverse as filament branching, filopodia extension, or actin remodeling in ciliogenesis and asymmetric meiotic division. They also integrate these functions with other actin-binding motifs present either in the same protein or in a complex with another protein, expanding the range of complexity in actin regulation. The details of their molecular mechanisms and the underlying structural basis provide exciting avenues in actin research. © 2013 Wiley Periodicals, Inc.
    Cytoskeleton 10/2013; 70(10). DOI:10.1002/cm.21124 · 3.12 Impact Factor
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    • "Rickettsia rickettsii utilizes a formin mimic, Sca2, to promote intracellular motility and intercellular spreading (Haglund et al., 2010). Vibrio cholera utilizes a T3SS effector with formin-like activity, VopF, to promote intestinal colonization (Tam et al., 2007). Here, we demonstrate a role for formins early in the bacterial invasion process. "
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    ABSTRACT: Salmonella invade host cells using Type 3 secreted effectors, which modulate host cellular targets to promote actin rearrangements at the cell surface that drive bacterial uptake. The Arp2/3 complex contributes to Salmonella invasion but is not essential, indicating other actin regulatory factors are involved. Here, we show a novel role for FHOD1, a formin family member, in Salmonella invasion. FHOD1 and Arp2/3 occupy distinct microdomains at the invasion site and control distinct aspects of membrane protrusion formation. FHOD1 is phosphorylated during infection and this modification is required for promoting bacterial uptake by host cells. ROCK II, but not ROCK I, is recruited to the invasion site and is required for FHOD1 phosphorylation and for Salmonella invasion. Together, our studies reveal an important phospho-dependent FHOD1 actin polymerization pathway in Salmonella invasion.
    Cellular Microbiology 07/2013; 15(12). DOI:10.1111/cmi.12173 · 4.92 Impact Factor
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    • "Interestingly, valine is present at position 213 in the case of V. cholerae strain SC110 used in this study. The domain 2 of VopF from other strain AM-19226 contains methionine at position 213 (Tam et al., 2007, Fig. 2). It would be interesting to examine the result of restoration of the substituted residues "
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    ABSTRACT: VopF, the type III effector molecule, has been implicated in the pathogenesis of non-O1, non-O139 strains of Vibrio cholerae. It is a protein of 530 amino acids, comprises of one formin homology 1-like (FH1-like) domain and three WASP homology 2 (WH2) domains. Previous works have demonstrated that WH2 domains are crucial for VopF function as a modulator of cellular actin homeostasis. Furthermore, domain deletion analysis also suggests that VopF variant constituted with only WH2 domain 3 is more efficient in restricting the growth of budding yeast than its congeners containing either only domain 1 or domain 2. Interestingly, a good degree of sequence diversity is present within each WH2 domain of VopF. In order to ascertain the importance of different amino acids in each WH2 domain, a systemic alanine scanning mutagenesis was employed. Using a yeast model system, the alanine derivatives of each amino acid of WH2 domain 1 and 3 of VopF were examined for growth restricting activity. Taken together, our mutagenesis results reveal the identification of critical residues of WH2 domain 1 and 3 of VopF.
    Gene 05/2013; 525(1). DOI:10.1016/j.gene.2013.04.071 · 2.14 Impact Factor
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