title: Roles of integrins and fibronectin in the entry of Streptococcus pyogenes into cells via protein F1.
abstract: Entry of group A streptococcus (GAS) into cells has been suggested as an important trait in GAS pathogenicity. Protein F1, a fibronectin (Fn) binding protein, mediates GAS adherence to cells and the extracellular matrix, and efficient cell internalization. We demonstrate that the cellular receptors responsible for protein F1-mediated internalization of GAS are integrins capable of Fn binding. In HeLa cells, bacterial entry is blocked by anti-beta1 integrin monoclonal antibody. In the mouse cell line GD25, a beta1 null mutant, the alphavbeta3 integrin promotes GAS entry. Internalization of these cells by GAS is blocked by a peptide that specifically binds to alphavbeta3 integrin. In both cell lines, entry of GAS requires the occupancy of protein F1 by Fn. Neither the 29 kDa nor the 70 kDa N-terminal fragments or the 120 kDa cell-binding fragment of Fn promote bacterial entry. Fn-coated beads are taken up efficiently by HeLa cells. Both the entry of GAS via protein F1 and the uptake of Fn-coated beads are blocked by anti-beta1 antibody but are unaffected by a large excess of soluble Fn. Internalization of HeLa cells by bacteria bearing increasing amounts of prebound Fn to protein F1 reveals a sigmoidal ultrasensitive curve. These suggest that the ability of particles to interact via Fn with multiple integrin sites plays a central role in their ability to enter cells.
authors.affiliation: Department of Clinical Microbiology, The Hebrew University-Hadassah Medical School, Jerusalem 91010, Israel.
authors.forename: V
authors.initials: V
authors.lastname: Ozeri
authors.forename: I
authors.initials: I
authors.lastname: Rosenshine
authors.forename: D F
authors.initials: DF
authors.lastname: Mosher
authors.forename: R
authors.initials: R
authors.lastname: Fässler
authors.forename: E
authors.initials: E
authors.lastname: Hanski
mesh_terms: D018829:Adhesins, Bacterial / Q000502:physiology*; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001426:Bacterial Proteins / Q000502:physiology; D004705:Endocytosis / Q000502:physiology; D005353:Fibronectins / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006801:Humans; D016023:Integrins / Q000502:physiology*; D008856:Microscopy, Fluorescence; D008863:Microspheres; D011485:Protein Binding / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000472:pathogenicity*
chemical_list: D018829:Adhesins, Bacterial; D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D005353:Fibronectins; D016023:Integrins; D011956:Receptors, Cell Surface; C078635:fibronectin-binding proteins, bacterial