Roles of Porphyromonas gulae proteases in bacterial and host cell biology.

Porphyromonas gulae, an animal-derived periodontal pathogen, expresses several virulence factors, including fimbria, lipopolysaccharide (LPS), and proteases. We previously reported that its invasive efficiency was dependent on fimbriae types. In addition, P. gulae LPS increased inflammatory responses via toll-like receptors. The present study was conducted to investigate the involvement of P. gulae proteases in bacterial and host cell biology. P. gulae strains showed an ability to agglutinate mouse erythrocytes and also demonstrated coaggregation with Actinomyces viscosus, while the protease inhibitors antipain, PMSF, TLCK, and leupeptin diminished P. gulae proteolytic activity, resulting in inhibition of hemagglutination and coaggregation with A. viscosus. In addition, specific proteinase inhibitors were found to reduce bacterial cell growth. P. gulae inhibited Ca9-22 cell proliferation in a multiplicity of infection- and time-dependent manner. Additionally, P. gulae-induced decreases in cell contact and adhesion-related proteins were accompanied by a marked change in cell morphology from well spread to rounded. In contrast, inhibition of protease activity prevented degradation of proteins, such as E-cadherin, β-catenin, and focal adhesion kinase, and also blocked inhibition of cell proliferation. Together, these results indicate suppression of the amount of human proteins, such as γ-globulin, fibrinogen and fibronectin, by P. gulae proteases, suggesting that a novel protease complex contributes to bacterial virulence. This article is protected by copyright. All rights reserved.