Porphyromonas gingivalis mediates the shedding and proteolysis of complement regulatory protein CD46 expressed by oral epithelial cells.
BACKGROUND
Human cells express membrane-bound complement regulatory proteins to prevent complement-mediated autologous tissue damage. In this study, we hypothesized that Porphyromonas gingivalis, the major etiological agent of chronic periodontitis, causes the shedding or proteolysis of the complement regulatory protein CD46 expressed by oral epithelial cells.


METHODS
Oral epithelial cells were treated with a culture of P. gingivalis before measurement of membrane-bound and shed CD46 by enzyme-linked immunosorbent assay (ELISA). The effect of soluble recombinant CD46 on secretion of interleukin-8 (IL-8) by epithelial cells was evaluated by ELISA. The susceptibility of soluble recombinant CD46 to proteolytic degradation by cells and purified Lys-gingipain of P. gingivalis was investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis/western immunoblotting analysis.


RESULTS
Oral epithelial cells treated with a culture of P. gingivalis showed a lower reactivity with antibodies directed to CD46. ELISA revealed that such a treatment resulted in increased amounts of CD46 in the conditioned media suggesting that P. gingivalis caused the shedding of membrane-anchored CD46. Stimulation of epithelial cells with soluble recombinant CD46 induced IL-8 secretion in a dose-dependent manner. Whole cells and purified Lys-gingipain of P. gingivalis degraded recombinant CD46 in a dose-dependent manner.


CONCLUSIONS
This study showed the ability of P. gingivalis to induce the shedding/ proteolysis of CD46 from the surface of oral epithelial cells. This may render host cells susceptible to the complement system and contribute to tissue damage and the inflammatory process in periodontitis.
Mahtout
H
H
Groupe de Recherche en Ecologie Buccale, Faculté de Médecine Dentaire, Université Laval, Quebec City, QC, Canada.
Chandad
F
F
Rojo
J M
JM
Grenier
D
D
D018829:Adhesins, Bacterial / Q000494:pharmacology; D000907:Antibodies, Bacterial / Q000032:analysis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000276:immunology; D017077:Culture Media, Conditioned; D003546:Cysteine Endopeptidases / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells / Q000276:immunology / Q000382:microbiology; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins / Q000494:pharmacology; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D051916:Membrane Cofactor Protein / Q000378:metabolism*; D008565:Membrane Proteins / Q000276:immunology; D009061:Mouth Mucosa / Q000276:immunology* / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000502:physiology*
D018829:Adhesins, Bacterial; D000907:Antibodies, Bacterial; C497857:CD46 protein, human; D017077:Culture Media, Conditioned; D000080867:Gingipain Cysteine Endopeptidases; D006388:Hemagglutinins; D016209:Interleukin-8; D051916:Membrane Cofactor Protein; D008565:Membrane Proteins; D003546:Cysteine Endopeptidases