Comparative study of the dynamics of focal contacts in live epithelial and mesenchymal cells.

To further characterize the morphology and dynamics of focal contacts (FCs) in epithelial cells, we compared the size, number, localization, velocity, and turnover of FCs in epithelial and mesenchymal cell lines. Using immunocytochemistry, we found there were no significant differences between mesenchymal and epithelial cells in number and appearance whereas the location and size of FCs in each cell were different between mesenchymal and epithelial cells. FCs in mesenchymal cells localized at the cell periphery and cell center, but FCs were found only at the cell periphery in epithelial cells. The size of FCs in epithelial cells were significantly smaller than in mesenchymal cells. Next, we compared the dynamics of FCs in both mesenchymal and epithelial cells and found no significant difference between the two groups. Finally, we added inhibitors for the hemidesmosome (HD) proteins, α6 integrin and β4 integrin, to HaCat cell (epithelial) cultures and examined the number and size of FCs. Under these conditions, the size and localization of FCs in HaCat cells became comparable to that of mesenchymal cells. Therefore, we concluded the size and localization of FCs is regulated by the existence of HDs in epithelial cells.