Porphyromonas gingivalis gingipains and adhesion to epithelial cells

Porphyromonas gingivalis is one of the principal organisms associated with adult periodontitis, Bacterial surface proteins such as fimbriae and gingip ain hemagglutinin domains have been implicated as adhesins that actuate col onization of epithelium lining the gingival sulcus, We investigated the gen etics of P, gingivalis adhesion to monolayers of epithelial cells using wil d-type and gingipain mutant strains. These experiments suggested that argin ine-specific gingipain (Rgp) catalytic activity modulated adhesion. From th e data obtained with rgp mutants, we constructed a working hypothesis predi cting that attachment and detachment of P. gingivalis to epithelial cells w ere mediated by gingipain adhesin and Rgp catalytic domains, respectively. A membrane-based epithelial cell binding assay used to locate adhesins in e xtracellular fractions of wild type and mutant strains, recognized gingipai n peptides as adhesins rather than fimbriae. We developed a capture assay t hat demonstrated the binding of gingipain adhesin peptides to oral epitheli al cells. The adherence of fimbrillin to epithelial cells was detected afte r heat denaturation of fell fractions. The prediction that Rgp catalytic ac tivities mediated detachment was substantiated when the high level of attac hment of an rgp mutant was reduced in the presence of wild-type cell fracti ons that contained gingipain catalytic activities.