Mechanisms of adherence of P.gingivalis to matrix proteins via fimbrial cryptie receptor

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Porphyromonas gingivalis 381, a suspected periodontopathogen, possesses fimbriae on its cell surface. The organism is known to produce proteases which can degrade the host cell surface matrix proteins. In this study, we investigated the effect of protease on the binding of the purified P.gingivalis fimbriae to cultures fibroblasts or matrix proteins. A protease that can hydrolyze benzoyl-L-arginine p-nitro-anilide was obtained from P.gingivalis 381 cells by sonication in phosphate-buffered 0.2% Triton X-100 and was purified by column chromatography. The protease degrade various host proteins, including collagen and fibronectin, and cleave the C-terminus of the arginine residue in peptides. However, P.gingivalis fimbriae were not degraded by this protease activity. When cultured fibroblasts were partially treated with the protease, the binding of the purified P.gingivalis fimbriae to the fibroblast monolayr was increased significantly. Similarly, binding of the fimbriae to the collagen … More or fibronectin immobilized on the microtiter wells was also enhanced. Addition of these host matrix proteins efficiently inhibited the binding of fimbriae to the fibroblast monolayr. The binding assay of fimbriae using dipeptidyl ligand affinity column chromatography demonstrated a clear interaction between fimbriae and the arginine residue. We then analyzed the interaction of fimbriae and immobilized fibronectins (intact or partially degraded fibronectin by the purified protease) by using the BIAcore system. BIAcore profiles demonstrated an enhanced interaction between fimbriae and protease-degraded fibronectin. We also showed specific binding of fimbriae to the degraded fibronectin by means of BIAcore analysis. The binding of biotinylated fimbriae to immobilized fibronectin was examined by enzyme-linked biotin-avidin assay. The purified protease enhanced the fimbrial binding to the immobilized fibronectin. The enhancement was inhibited by the addition of L-Arg, or oligopeptides containing the Arg residue at the C-terminus, suggesting than the P.gingivalis fimbriae may potentially have an ability to bind tightly to the Arg residue at C-terminus. Taken together, these studies indicate that P.gingivalis arginine-specific protease can expose a cryptitope in the matrix protein molecules, i.e.the C-terminal Arg residue of the host matrix proteins, so that the organism can adhere to the surface layr in the oral cavity through fimbriae-Arg interaction (a novel host-parasite relation ship). Less