Mechanisms of Virulence Regulation in Porphyromonas gingivalis W83

The expression of extracellular proteolytic activities is highly regulated in both prokaryotic and eukaryotic systems. This regulation can occur at multiple levels including expression of the protease genes, secretion, processing of an inactive secreted precursor to its active form and/or the posttranslational glycosylation of the proteins. These regulatory mechanisms are vital to ensure that expression is tightly controlled. Porphyromonas gingivalis has been associated with adult periodontitis and in the development of many systematic diseases. The major virulence factors of P. gingivalis, the gingipains, are responsible for pathogenesis including degradation of complement and immunoglobulin, inactivation of cytokines and their receptors, aggregation of platelets, attenuation of neutrophil antibacterial activities, and increase in vascular permeability and blood clotting prevention. How these gingipains are regulated is poorly understood. We focused on identifying possible regulators and/or mechanisms P. gingivalis possesses for the regulation/activation of the gingipains, in addition to other virulence factors. We have identified and characterized three novel genes, vimA, vimE and vimF, which are involved in the maturation/activation of the virulence factors of P. gingivalis. The identification of the production of inactive gingipains and altered carbohydrate modification of these gingipains from these isogenic mutants suggests gingipain maturation may be dependent upon proper carbohydrate biogenesis. We have also provided evidence for the importance of carbohydrate biogenesis in anchorage of the gingipains to the cell surface. Protein interaction studies demonstrated the interaction of the gingipains with VimA and VimE, further suggesting the involvement of VimA and VimE in a pathway for gingipain maturation. We have also identified other regulatory proteins in P. gingivalis that interacts with the VimA and VimE proteins. We have also demonstrated that the periplasmic serine protease, HtrA, and the newly identified RegT, may play a role in regulating the gingipains and/or growth of P. gingivalis under stressful environmental conditions. Immunoblot analysis of P. gingivalis challenged mice and/or periodontitis patients have identified the VimA and/or VimE proteins as excellent candidates for a therapeutic approach against this periodontal pathogen. Taken together, we have provided evidence that VimA, VimE and VimE, in addition to proper carbohydrate biogenesis, play a role in gingipain regulation