title: Internalin must be on the bacterial surface to mediate entry of Listeria monocytogenes into epithelial cells.
abstract: Entry of Listeria monocytogenes into cultured epithelial cells requires production of internalin, a protein with features characteristic of some Gram-positive bacterial surface proteins, in particular an LPXTG motif preceding a hydrophobic sequence and a few basic residues at its C-terminal end. By immunofluorescence and immunogold labelling, we show that in wild-type L. monocytogenes, internalin is present on the cell surface and has a polarized distribution similar to that of ActA, another surface protein of L. monocytogenes involved in actin assembly. Through a genetic analysis, we establish that the C-terminal region of internalin is necessary for cell-surface association, and that although internalin is partially released in the culture medium, its location on the bacterial surface is required to promote entry. Finally, using a 'domain-swapping' strategy-replacement of the cell wall anchor of IniA by the membrane anchor of ActA- we show that the reduced ability to adhere and enter cells of strains expressing IniA-ActA correlates with a lower amount of surface-exposed internalin. Taken together, these results suggest that internalin exposed on the bacterial surface mediates direct contact between the bacterium and the host cell.
authors.affiliation: Unité des Interactions Bactéries-Cellules, Institut Pasteur, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Lebrun
authors.forename: J
authors.initials: J
authors.lastname: Mengaud
authors.forename: H
authors.initials: H
authors.lastname: Ohayon
authors.forename: F
authors.initials: F
authors.lastname: Nato
authors.forename: P
authors.initials: P
authors.lastname: Cossart
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism; D004847:Epithelial Cells; D006801:Humans; D008089:Listeria monocytogenes / Q000378:metabolism* / Q000472:pathogenicity; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; C069761:internalin protein, Bacteria; C072980:actA protein, Listeria monocytogenes