title: Zipper-like internalization of Dr-positive Escherichia coli by epithelial cells is preceded by an adhesin-induced mobilization of raft-associated molecules in the initial step of adhesion.
abstract: We undertook a study of the mechanism by which Dr-positive bacteria invade epithelial cells. Our findings show that Dr-positive bacteria enter via a zipper-like mechanism that is independent of the Dr-induced mobilization of F-actin and of the signaling molecules that control Dr-induced F-actin rearrangements. We also observed that Dr-positive IH11128 bacteria entered cells that were positive for the caveola marker VIP21/caveolin (HeLa and Caco-2/Cav-1 cells) to the same extent as those that were not (parental Caco-2 cells). Using fluorescence labeling and confocal laser scanning microscopy, we provide evidence that during the adhesion step, the alpha5beta1 integrin, which plays a pivotal role in Afa/Dr diffusely adhering Escherichia coli bacterial entry, is mobilized around adhering Dr-positive bacteria. We show that the receptor for Afa/Dr adhesins, glycosylphosphatidylinositol-anchored CD55; the raft marker, ganglioside GM1; and VIP21/caveolin are all recruited around adhering Dr-positive bacteria. We also observed that extracting membrane cholesterol with methyl-beta-cyclodextrin (MBCD) did not affect the recruitment of CD55, GM1, or beta1 integrin to adhering Dr-positive bacteria. In contrast, extracting or changing membrane-bound cholesterol by means of drugs that modify lipid rafts (MBCD, filipin III, or mevalonate plus lovastatin plus MBCD) inhibited the entry of Dr-positive IH11128 both into cells that expressed VIP21/caveolin (HeLa and Caco-2/Cav-1 cells) and into those that did not (parental Caco-2 cells). Finally, restoring cholesterol within the cell membrane of MBCD-treated cells restored Dr-positive IH11128 internalization.
authors.affiliation: Unité 510 INSERM, Faculté de Pharmacie Paris XI, F-92296 Châtenay-Malabry, France.
authors.forename: Imad
authors.initials: I
authors.lastname: Kansau
authors.forename: Cédric
authors.initials: C
authors.lastname: Berger
authors.forename: Maxime
authors.initials: M
authors.lastname: Hospital
authors.forename: Raymonde
authors.initials: R
authors.lastname: Amsellem
authors.forename: Valérie
authors.initials: V
authors.lastname: Nicolas
authors.forename: Alain L
authors.initials: AL
authors.lastname: Servin
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Bernet-Camard
mesh_terms: D000199:Actins / Q000378:metabolism; D018830:Adhesins, Escherichia coli / Q000378:metabolism*; D001422:Bacterial Adhesion / Q000502:physiology*; D018938:Caco-2 Cells / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism / Q000382:microbiology; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006388:Hemagglutinins / Q000378:metabolism*; D006801:Humans; D039081:Integrin alpha5beta1 / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism* / Q000382:microbiology
chemical_list: D000199:Actins; D018830:Adhesins, Escherichia coli; C465564:Dr adhesin, E coli; D029968:Escherichia coli Proteins; D006388:Hemagglutinins; D039081:Integrin alpha5beta1; D002784:Cholesterol