Cytoskeletal and Membranous Alterations in Gingival Epithelial Cells Induced by Porphyromonas gingivalis Invasion

Porphyromonas gingivalis attaches to and invades primary gingival epithelial cells (GEC) in a fimbriae-dependent manner. GEC integrins were recently identified as the invasion associated receptor for P. gingivalis fimbriae. Objectives: to explore the subcellular localization of integrin associated signaling and focal adhesion molecules paxillin and Fak, and the assembly of the actin and microtubule cytoskeleton during P. gingivalis infection. Methods: GEC were grown on coverslips, infected with wild type and fimbriae-deficient mutant P. gingivalis, fixed and examined for redistribution and rearrangements of specific molecules during bacterial invasion by immunofluorescence microscopy. Images were captured with an attached cooled CCD camera. Results: Treatment of GEC with wild type P. gingivalis revealed significant activation of paxillin and Fak after 30 minutes. Paxillin and Fak, recruited from perinuclear space and cytosol, were redistributed along the cell cortex forming fine clusters and numerous lamellipodial-like protrusions. In contrast, fimbriae- deficient bacteria did not contribute significantly to activation of paxillin and Fak; however, they promoted a widespread cortical actin meshwork accompanied by extensions resembling filopodium and lamellipodium. After 24-hour the majority of paxillin and Fak was confined to the perinuclear area, and colocalized with internalized P. gingivalis. Remarkable disassembly and nucleation of actin and microtubule filamentous network was also observed. Conclusions: In GEC, P. gingivalis induces fimbriae-dependent redistribution of paxillin and Fak that later colocalize with the internalized bacteria. Subsequently, there is dramatic depolymerization of the actin and microtubule cytoskeleton within GEC. This work was supported by grant DE14168 from NIDCR .