Functional role of the type 1 pilus rod structure in mediating host-pathogen interactions
- Washington University School of Medicine, United States
- University of Virginia, United States
- Umeå University, Sweden
- Institut Pasteur, France
- Cited 17
- Views 3,288
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Abstract
Uropathogenic E. coli (UPEC), which cause urinary tract infections (UTI), utilize type 1 pili, a chaperone usher pathway (CUP) pilus, to cause UTI and colonize the gut. The pilus rod, comprised of repeating FimA subunits, provides a structural scaffold for displaying the tip adhesin, FimH. We solved the 4.2 Å resolution structure of the type 1 pilus rod using cryo-electron microscopy. Residues forming the interactive surfaces that determine the mechanical properties of the rod were maintained by selection based on a global alignment of fimA sequences. We identified mutations that did not alter pilus production in vitro but reduced the force required to unwind the rod. UPEC expressing these mutant pili were significantly attenuated in bladder infection and intestinal colonization in mice. This study elucidates an unappreciated functional role for the molecular spring-like property of type 1 pilus rods in host-pathogen interactions and carries important implications for other pilus-mediated diseases.
Article and author information
Author details
Henry Louis Schreiber
Funding
National Institutes of Health (GM122510)
- Edward H Egelman
Washington University School of Medicine (Monsanto Excellence Fund Graduate Fellowship)
- Henry Louis Schreiber
National Institutes of Health (AI048689)
- Scott Hultgren
National Institutes of Health (DK064540)
- Scott Hultgren
National Institutes of Health (1F31DK107057)
- Caitlin N Spaulding
National Institutes of Health (DK101171-02)
- Matt S Conover
Svenska Forskningsrådet Formas (621-2013-5379)
- Magnus Andersson
Agence Nationale de la Recherche (ANR-14-CE09-0004)
- Olivera Francetic
Paris Pasteur University (Graduate Research Fellowship)
- Areli Luna-Rico
Washington University School of Medicine (Lucille P. Markey Pathway for Pathobiology)
- Henry Louis Schreiber
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Ethics
Animal experimentation: The Washington University Animal Studies Committee approved all procedures used for the mouse experiments described in the present study (Protocol Application Number 20150226). Overall care of the animals was consistent with The Guide for the Care and Use of Laboratory Animals from the National Research Council and the USDA Animal Care Resource Guide. Every effort was made to minimize suffering.
Reviewing Editor
- Michael S Gilmore, Harvard Medical School, United States
Publication history
- Received: August 31, 2017
- Accepted: January 12, 2018
- Accepted Manuscript published: January 18, 2018 (version 1)
- Version of Record published: February 5, 2018 (version 2)
Copyright
© 2018, Spaulding et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Further reading
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- Cell Biology
- Structural Biology and Molecular Biophysics
The actin cytoskeleton mediates mechanical coupling between cells and their tissue microenvironments. The architecture and composition of actin networks are modulated by force; however, it is unclear how interactions between actin filaments (F-actin) and associated proteins are mechanically regulated. Here we employ both optical trapping and biochemical reconstitution with myosin motor proteins to show single piconewton forces applied solely to F-actin enhance binding by the human version of the essential cell-cell adhesion protein αE-catenin but not its homolog vinculin. Cryo-electron microscopy structures of both proteins bound to F-actin reveal unique rearrangements that facilitate their flexible C-termini refolding to engage distinct interfaces. Truncating α-catenin’s C-terminus eliminates force-activated F-actin binding, and addition of this motif to vinculin confers force-activated binding, demonstrating that α-catenin’s C-terminus is a modular detector of F-actin tension. Our studies establish that piconewton force on F-actin can enhance partner binding, which we propose mechanically regulates cellular adhesion through α-catenin.
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- Structural Biology and Molecular Biophysics
Cell-cell and cell-matrix junctions transmit mechanical forces during tissue morphogenesis and homeostasis. α-Catenin links cell-cell adhesion complexes to the actin cytoskeleton, and mechanical load strengthens its binding to F-actin in a direction-sensitive manner. Specifically, optical trap experiments revealed that force promotes a transition between weak and strong actin-bound states. Here, we describe the cryo-electron microscopy structure of the F-actin-bound αE-catenin actin-binding domain, which in solution forms a five-helix bundle. In the actin-bound structure, the first helix of the bundle dissociates and the remaining four helices and connecting loops rearrange to form the interface with actin. Deletion of the first helix produces strong actin binding in the absence of force, suggesting that the actin-bound structure corresponds to the strong state. Our analysis explains how mechanical force applied to αE-catenin or its homolog vinculin favors the strongly bound state, and the dependence of catch bond strength on the direction of applied force.
