Objective: The aim of this study was to determine the effect of S. aureus FnBP on the adhesion, migration, cell cycle progression, and endogenous FN assembly of human keratinocytes (UP).
Methods: A recombinant histidine-tagged protein encompassing the D1-D4 repeat region of S. aureus FnBPB (rFnBPBD1-D4) was prepared. FN-coated plates and transwell membranes were double-coated with rFnBPBD1-D4 protein before adhesion and migration assays. For the wound assay, the extent of cell migration into the wound areas and cell cycle progression (BrdU incorporation) were determined at 20 h. For FN assembly, endogenous cellular FN was detected using the monoclonal antibody IST-9 at 24 h.
Results: The rFnBPBD1-D4 protein had no effect on the adhesion of UP cells to FN substrate. However, migration of UP cells was reduced by 17% (p=0.036) and 31% (p=0.017) in the presence of rFnBPBD1-D4 at 10 and 100 µg/ml respectively. In the wound assay, the migration area was reduced by 33% (p=0.009). Differences in BrdU uptake in rFnBPBD1-D4-treated cells and non-treated controls were not observed. In the presence of rFnBPBD1-D4, most of the cellular FN matrix on the cell surface and along the cell filopodia seen in untreated cells was absent.
Conclusion: rFnBPBD1-D4 inhibits endogenous FN polymerization and migration on FN of UP keratinocytes. Decreased migration of UP cells was not due to a decrease in the adhesion or proliferation of the cells. Interaction of rFnBPBD1-D4 with intact and fragments of FN may influence cell behaviour and may have a role to play in delayed epithelial closure in healing wounds.