Inhibitory effects of Porphyromonas gingivalis fimbriae on interactions between extracellular matrix proteins and cellular integrins

Porphyromonas gingivalis is a predominant periodontal pathogen, whose fimbriae are considered to be a major virulence factor, especially for bacterial adherence and invasion of host cells. In the present study, we investigated the influence of fimbriae on the interactions between αvβ3- and α5β1-integrins and their ligand extracellular matrix (ECM) proteins (vitronectin and fibronectin), using human αvβ3- and α5β1-integrin-overexpressing CHO cell lines (CHOαvβ3 and CHOα5β1, respectively). P. gingivalis was found to have significantly greater binding to CHOαvβ3 and CHOα5β1 than to control cells, whereas a fimbria-deficient mutant showed negligible binding to any of the tested cell lines. CHOαvβ3 and CHOα5β1 cells attached to the polystyrene culture dishes in the presence of their ligand ECM proteins, while fimbriae markedly inhibited those attachments in a dose-dependent manner, with the highest dose of fimbriae achieving complete inhibition. In addition, the binding of vitronectin and fibronectin to CHOαvβ3 and CHOα5β1 was inhibited by P. gingivalis cells. These results suggest that P. gingivalis fimbriae compete with ECM proteins for αvβ3- and α5β1-integrins, and inhibit integrin/ECM protein-related cellular functions.