Involvement of focal adhesion kinase in cell adhesion force on different substrate rigidity

We hypothesize that FAK is the rigidity sensor in response to different rigidity of substrates. In present study, we plate MDCK epithelial cell on glass surface, 1 kPa, and 30 kPa polyacrylamide gels, respectively. The FAK expression for substrate rigidity sensing and adhesion force management was studied by cytodetachment device and fluorescent microscopy. Different expression levels of FAK by gene overexpression (FAK-WT) and knock-out (FRNK) were also used to probe the function of FAK in rigidity sensing. The results indicate that cell spreading area, adhesion force, and work increased with increasing substrate rigidity. Except for cell area and normalized adhesion force, all parameters were significantly different between FAK-WT and FRNK cells. FAK can enhance cell spreading and increase the normalized adhesion force on 30 kPa and 1 kPa gels. The effect of FAK is weaker on stiffer substrate than on softer matrix.