title: Exit of intracellular Porphyromonas gingivalis from gingival epithelial cells is mediated by endocytic recycling pathway.
abstract: Gingival epithelial cells function as an innate host defence system to prevent intrusion by periodontal bacteria. Nevertheless, Porphyromonas gingivalis, the most well-known periodontal pathogen, can enter gingival epithelial cells and pass through the epithelial barrier into deeper tissues. However, it is poorly understood how this pathogen exits from infected cells for further transcellular spreading. The present study was performed to elucidate the cellular machinery exploited by P. gingivalis to exit from immortalized human gingival epithelial cells. P. gingivalis was shown to be internalized with early endosomes positive for the FYVE domain of EEA1 and transferrin receptor, and about half of the intracellular bacteria were then sorted to lytic compartments, including autolysosomes and late endosomes/lysosomes, while a considerable number of the remaining organisms were sorted to Rab11- and RalA-positive recycling endosomes. Inhibition experiments revealed that bacterial exit was dependent on actin polymerization, lipid rafts and microtubule assembly. Dominant negative forms and RNAi knockdown of Rab11, RalA and exocyst complex subunits (Sec5, Sec6 and Exo84) significantly disturbed the exit of P. gingivalis. These results strongly suggest that the recycling pathway is exploited by intracellular P. gingivalis to exit from infected cells to neighbouring cells as a mechanism of cell-to-cell spreading.
authors.affiliation: Department of Oral Frontier Biology, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takeuchi
authors.forename: Nobumichi
authors.initials: N
authors.lastname: Furuta
authors.forename: Ichijiro
authors.initials: I
authors.lastname: Morisaki
authors.forename: Atsuo
authors.initials: A
authors.lastname: Amano
mesh_terms: D000199:Actins / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement; D004705:Endocytosis; D011992:Endosomes / Q000276:immunology; D004847:Epithelial Cells / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D005881:Gingiva / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology*; D006801:Humans; D007113:Immunity, Innate; D042541:Intracellular Space / Q000276:immunology; D008247:Lysosomes; D021962:Membrane Microdomains / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism; D016966:Porphyromonas gingivalis / Q000276:immunology* / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D011990:Receptors, Transferrin; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020725:ral GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D000099193:rab11 GTP-Binding Proteins
chemical_list: D000199:Actins; D034741:RNA, Small Interfering; D011990:Receptors, Transferrin; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D020725:ral GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C093846:early endosome antigen 1; C492198:RALA protein, human