CELLULAR EVENTS CONCURRENT WITH PORPHYROMONAS-GINGIVALIS INVASION OF ORAL EPITHELIUM IN-VITRO

The aim of the present study was to elucidate events related to recept or function, signal transmission and cytoskeletal rearrangements concu rrent with Porphyromonas gingivalis invasion of oral epithelial cells in vitro. Porphyromonas gingivalis strain FDC 381 and the KB cell line (ATCC CCL 17) were used in a previously described antibiotic protecti on assay. The involvement of a receptor-mediated endocytosis pathway i n the internalization process was demonstrated after treatment of the epithelial cells with monodansylcadaverine and ouabain, substances tha t inhibit formation of coated pits, resulting in reduction in the numb er of invading P. gingivalis. Treatment of the epithelial cells with t he protein kinase (PK) inhibitor staurosporine and the tyrosine-specif ic PK inhibitor genistein was also found to significantly decrease the number of invading bacteria, suggesting involvement of tyrosine phosp horylation in signal transduction during invasion. This was further su pported by the identification of a 43 kD protein acting as a substrate for tyrosine phosphorylation subsequent to the microbial-host cell in teraction. Tyrosine phosphorylation of the 43 kD protein was strongly reduced by treatment with PK inhibitors. The decrease in invasion obse rved after treatment of epithelial cells with colchicine and nocodazol e, inhibitors of microtubuli polymerization, suggested that the bacter ial-receptor interaction and the phosphotyrosine-dependent intracellul ar signalling trigger an internalization process involving rearrangeme nts of cytoskeletal microtubuli.