title: A lipid zipper triggers bacterial invasion.
abstract: Glycosphingolipids are important structural constituents of cellular membranes. They are involved in the formation of nanodomains ("lipid rafts"), which serve as important signaling platforms. Invasive bacterial pathogens exploit these signaling domains to trigger actin polymerization for the bending of the plasma membrane and the engulfment of the bacterium--a key process in bacterial uptake. However, it is unknown whether glycosphingolipids directly take part in the membrane invagination process. Here, we demonstrate that a "lipid zipper," which is formed by the interaction between the bacterial surface lectin LecA and its cellular receptor, the glycosphingolipid Gb3, triggers plasma membrane bending during host cell invasion of the bacterium Pseudomonas aeruginosa. In vitro experiments with Gb3-containing giant unilamellar vesicles revealed that LecA/Gb3-mediated lipid zippering was sufficient to achieve complete membrane engulfment of the bacterium. In addition, theoretical modeling elucidated that the adhesion energy of the LecA-Gb3 interaction is adequate to drive the engulfment process. In cellulo experiments demonstrated that inhibition of the LecA/Gb3 lipid zipper by either lecA knockout, Gb3 depletion, or application of soluble sugars that interfere with LecA binding to Gb3 significantly lowered P. aeruginosa uptake by host cells. Of note, membrane engulfment of P. aeruginosa occurred independently of actin polymerization, thus corroborating that lipid zippering alone is sufficient for this crucial first step of bacterial host-cell entry. Our study sheds new light on the impact of glycosphingolipids in the cellular invasion of bacterial pathogens and provides a mechanistic explication of the initial uptake processes.
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies, thorsten.eierhoff@bioss.uni-freiburg.de christian.fleck@wur.nl winfried.roemer@bioss.uni-freiburg.de.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Eierhoff
authors.affiliation: Centre for Biological Systems Analysis, and.
authors.forename: Björn
authors.initials: B
authors.lastname: Bastian
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies.
authors.forename: Roland
authors.initials: R
authors.lastname: Thuenauer
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies.
authors.forename: Josef
authors.initials: J
authors.lastname: Madl
authors.affiliation: Centre de Recherches sur les Macromolécules Végétales, Université Grenoble Alpes and Centre National de la Recherche Scientifique, F38000 Grenoble, France;
authors.forename: Aymeric
authors.initials: A
authors.lastname: Audfray
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies, International Max Planck Research School for Molecular and Cellular Biology, Max Planck Institute of Immunobiology and Epigenetics, 79108 Freiburg, Germany;
authors.forename: Sahaja
authors.initials: S
authors.lastname: Aigal
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies, Spemann Graduate School of Biology and Medicine, Albert Ludwigs University Freiburg, 79104 Freiburg, Germany;
authors.forename: Samuel
authors.initials: S
authors.lastname: Juillot
authors.affiliation: Department of Infectious Diseases, Section for Clinical Virology, University of Gothenburg, S-413 46 Gothenburg, Sweden;
authors.forename: Gustaf E
authors.initials: GE
authors.lastname: Rydell
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies.
authors.forename: Stefan
authors.initials: S
authors.lastname: Müller
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UMR7255 Centre National de la Recherche Scientifique and Aix Marseille University, Institut de Microbiologie de la Méditerranée, 13402 Marseille, France; and.
authors.forename: Sophie
authors.initials: S
authors.lastname: de Bentzmann
authors.affiliation: Centre de Recherches sur les Macromolécules Végétales, Université Grenoble Alpes and Centre National de la Recherche Scientifique, F38000 Grenoble, France;
authors.forename: Anne
authors.initials: A
authors.lastname: Imberty
authors.affiliation: Centre for Biological Systems Analysis, and Laboratory for Systems and Synthetic Biology, Wageningen University, 6703 HB, Wageningen, The Netherlands thorsten.eierhoff@bioss.uni-freiburg.de christian.fleck@wur.nl winfried.roemer@bioss.uni-freiburg.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Fleck
authors.affiliation: Faculty of Biology, BIOSS Centre for Biological Signalling Studies, Spemann Graduate School of Biology and Medicine, Albert Ludwigs University Freiburg, 79104 Freiburg, Germany; thorsten.eierhoff@bioss.uni-freiburg.de christian.fleck@wur.nl winfried.roemer@bioss.uni-freiburg.de.
authors.forename: Winfried
authors.initials: W
authors.lastname: Römer
mesh_terms: D000199:Actins / Q000378:metabolism*; D018829:Adhesins, Bacterial / Q000378:metabolism; D001422:Bacterial Adhesion / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism / Q000382:microbiology; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D006017:Glycolipids / Q000378:metabolism; D006028:Glycosphingolipids / Q000378:metabolism*; D008051:Lipid Bilayers / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism / Q000382:microbiology*; D008954:Models, Biological; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013107:Sphingolipids / Q000378:metabolism
chemical_list: D000199:Actins; D018829:Adhesins, Bacterial; D006017:Glycolipids; D006028:Glycosphingolipids; C102929:LecA protein, bacteria; D008051:Lipid Bilayers; D013107:Sphingolipids; C063288:globotriaosyl lysosphingolipid
keywords: glycolipid; infection; membrane curvature