Suppression of FAK Kinase Expression Decreases the Lifetime of Focal Adhesions and Inhibits Migration of Normal and Tumor Epitheliocytes in a Wound Healing Assay

Abstract

Focal adhesions (FAs) are mechanosensory structures that can convert physical stimuli into chemical signals guiding cell migration. There is a postulated correlation between FA features and cell motility parameters for individual migrating cells. However, which FA properties are essential for the movement of epithelial cells within a monolayer remains poorly elucidated. We used real-time cell visualization to describe the relationship between FA parameters and migration of immortalized epithelial keratinocytes (HaCaT) and lung carcinoma cells (A549) under inhibition or depletion of the FA proteins vinculin and FAK. To evaluate the relationship between FA morphology and cell migration, we used substrates of different elasticity in a wound healing assay. High FAK and vinculin mRNA expression, as well as largest FAs and maximal migration rate were described for cells on fibronectin, whereas cells plated on glass had minimal FA area and decelerated speed of migration into the wound. Both for normal and tumor cells, suppression of vinculin expression resulted in decreased FA size and fluorescence intensity, but had no effect on cell migration into the wound. Suppression of FAK expression or inhibition of FAK activity had no effect on FA size, but decreased FA lifetime and significantly slowed the rate of wound healing both for HaCaT and A549 cells. Our data indicates that FA lifetime, but not FA area is essential for epithelial cell migration within a monolayer. The effect of FAK kinase on the rate of cell migration within the monolayer makes FAK a promising target for antitumor therapy of lung adenocarcinoma.