• Open Access

The Bordetella type III secretion system effector BteA contains a conserved N-terminal motif that guides bacterial virulence factors to lipid rafts

Authors

  • Christopher T. French,

    1. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine,
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    • C.T.F. and E.M.P. contributed equally to this work.

  • Ekaterina M. Panina,

    1. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine,
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    • C.T.F. and E.M.P. contributed equally to this work.

    • Department of Molecular Oncology, Genentech, South San Francisco, CA 94080, USA.

  • Sylvia H. Yeh,

    1. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine,
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    • §

      Present addresses: UCLA Center for Vaccine Research, 1124 W., Carson St. Liu Research Building, Torrance, CA 90502, USA. Email syeh@uclacvr.labiomed.org;

  • Natasha Griffith,

    1. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine,
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  • Diego G. Arambula,

    1. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine,
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  • Jeff F. Miller

    Corresponding author
    1. Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine,
    2. the Molecular Biology Institute and
    3. the California Nanosystems Institute, University of California, Los Angeles, CA 90095, USA.
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*E-mail jfmiller@ucla.edu; Tel. (+1) 310 206 7926; Fax (+1) 310 206 3865.

Summary

The Bordetella type III secretion system (T3SS) effector protein BteA is necessary and sufficient for rapid cytotoxicity in a wide range of mammalian cells. We show that BteA is highly conserved and functionally interchangeable between Bordetella bronchiseptica, Bordetella pertussis and Bordetella parapertussis. The identification of BteA sequences required for cytotoxicity allowed the construction of non-cytotoxic mutants for localization studies. BteA derivatives were targeted to lipid rafts and showed clear colocalization with cortical actin, ezrin and the lipid raft marker GM1. We hypothesized that BteA associates with the cytoplasmic face of lipid rafts to locally modulate host cell responses to Bordetella attachment. B. bronchiseptica adhered to host cells almost exclusively to GM1-enriched lipid raft microdomains and BteA colocalized to these same sites following T3SS-mediated translocation. Disruption of lipid rafts with methyl-β-cyclodextrin protected cells from T3SS-induced cytotoxicity. Localization to lipid rafts was mediated by a 130-amino-acid lipid raft targeting domain at the N-terminus of BteA, and homologous domains were identified in virulence factors from other bacterial species. Lipid raft targeting sequences from a T3SS effector (Plu4750) and an RTX-type toxin (Plu3217) from Photorhabdus luminescens directed fusion proteins to lipid rafts in a manner identical to the N-terminus of BteA.

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