Proteome analysis of Porphyromonas gingivalis cells placed in a subcutaneous chamber of mice

Introduction: Porphyromonas gingivalis, an oral anaerobic bacterium, is considered a major pathogen for chronic periodontitis. Pathogenic bacteria usually upregulate or downregulate gene expression to combat the protective responses of their hosts. Methods: To determine what protein is regulated when P. gingivalis cells invade host tissues, we analyzed the proteome of P. gingivalis cells that were placed in a mouse subcutaneous chamber by two-dimensional gel electrophoresis and mass spectrometry. Results: Fourteen proteins were upregulated, while four proteins were downregulated. We focused on three upregulated proteins, PG1089 (DNA-binding response regulator RprY), PG1385 (TPR domain protein), and PG2102 (immunoreactive 61-kDa antigen), and constructed mutant strains that were defective in these proteins. Mouse abscess model experiments revealed that the mutant strain defective in PG1385 was clearly less virulent than the wild-type parent strain. Conclusion: These results indicate that the PG1385 protein is involved in P. gingivalis virulence and that the method used here is useful when investigating the P. gingivalis proteins responsible for virulence.