Recruitment of vimentin to the cell surface by β3 integrin and plectin mediates adhesion strength

Much effort has been expended on analyzing how microfilament and microtubule cytoskeletons dictate the interaction of cells with matrix at adhesive sites called focal adhesions (FAs). However, vimentin intermediate filaments (IFs) also associate with the cell surface at FAs in endothelial cells. Here, we show that IF recruitment to FAs in endothelial cells requires beta 3 integrin, plectin and the microtubule cytoskeleton, and is dependent on microtubule motors. In CHO cells, which lack beta 3 integrin but contain vimentin, IFs appear to be collapsed around the nucleus, whereas in CHO cells expressing beta 3 integrin (CHOwt beta 3), vimentin IFs extend to FAs at the cell periphery. This recruitment is regulated by tyrosine residues in the beta 3 integrin cytoplasmic tail. Moreover, CHOwt beta 3 cells exhibit significantly greater adhesive strength than CHO or CHO cells expressing mutated beta 3 integrin proteins. These differences require an intact vimentin network. Therefore, vimentin IF recruitment to the cell surface is tightly regulated and modulates the strength of adhesion of cells to their substrate.