title: Helicobacter pylori type IV secretion apparatus exploits beta1 integrin in a novel RGD-independent manner.
abstract: Translocation of the Helicobacter pylori (Hp) cytotoxin-associated gene A (CagA) effector protein via the cag-Type IV Secretion System (T4SS) into host cells is a major risk factor for severe gastric diseases, including gastric cancer. However, the mechanism of translocation and the requirements from the host cell for that event are not well understood. The T4SS consists of inner- and outer membrane-spanning Cag protein complexes and a surface-located pilus. Previously an arginine-glycine-aspartate (RGD)-dependent typical integrin/ligand type interaction of CagL with alpha5beta1 integrin was reported to be essential for CagA translocation. Here we report a specific binding of the T4SS-pilus-associated components CagY and the effector protein CagA to the host cell beta1 Integrin receptor. Surface plasmon resonance measurements revealed that CagA binding to alpha5beta1 integrin is rather strong (dissociation constant, K(D) of 0.15 nM), in comparison to the reported RGD-dependent integrin/fibronectin interaction (K(D) of 15 nM). For CagA translocation the extracellular part of the beta1 integrin subunit is necessary, but not its cytoplasmic domain, nor downstream signalling via integrin-linked kinase. A set of beta1 integrin-specific monoclonal antibodies directed against various defined beta1 integrin epitopes, such as the PSI, the I-like, the EGF or the beta-tail domain, were unable to interfere with CagA translocation. However, a specific antibody (9EG7), which stabilises the open active conformation of beta1 integrin heterodimers, efficiently blocked CagA translocation. Our data support a novel model in which the cag-T4SS exploits the beta1 integrin receptor by an RGD-independent interaction that involves a conformational switch from the open (extended) to the closed (bent) conformation, to initiate effector protein translocation.
authors.affiliation: Max von Pettenkofer-Institute for Hygiene and Medical Microbiology, Ludwig-Maximilians-Universität, München, Germany.
authors.forename: Luisa F
authors.initials: LF
authors.lastname: Jiménez-Soto
authors.forename: Stefan
authors.initials: S
authors.lastname: Kutter
authors.forename: Xaver
authors.initials: X
authors.lastname: Sewald
authors.forename: Claudia
authors.initials: C
authors.lastname: Ertl
authors.forename: Evelyn
authors.initials: E
authors.lastname: Weiss
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kapp
authors.forename: Manfred
authors.initials: M
authors.lastname: Rohde
authors.forename: Torsten
authors.initials: T
authors.lastname: Pirch
authors.forename: Kirsten
authors.initials: K
authors.lastname: Jung
authors.forename: S Francesco
authors.initials: SF
authors.lastname: Retta
authors.forename: Laurent
authors.initials: L
authors.lastname: Terradot
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fischer
authors.forename: Rainer
authors.initials: R
authors.lastname: Haas
mesh_terms: D000942:Antigens, Bacterial / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D010861:Fimbriae, Bacterial; D006367:HeLa Cells; D016480:Helicobacter pylori / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D008954:Models, Biological; D009842:Oligopeptides / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D055571:Secretory Pathway; D018709:Statistics, Nonparametric
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D019012:Integrin beta1; D009842:Oligopeptides; C080866:cagA protein, Helicobacter pylori; C047981:arginyl-glycyl-aspartic acid