Zyxin is a focal adhesion protein that has been implicated in the modulation of 
cell adhesion and motility, and is hypothesized to be a mechano-sensor in 
integrin-mediated responses to mechanical force. To test the functional role of 
zyxin in the mechanotransduction of microvascular smooth muscle cells (VSMC), we 
utilized atomic force microscopy (AFM) to apply localized pulling forces to VSMC 
through a fibronectin (FN) focal adhesion induced by a FN-coated bead on cell 
surface. Application of force with the AFM induced an increase of zyxin 
accumulation at the site of the FN-bead focal adhesion that accompanied the VSMC 
contractile response. Whereas, reduction of zyxin expression by using a 
zyxin-shRNA construct abolished the VSMC contractile response to AFM pulling 
forces, even though the zyxin-silenced VSMCs displayed increased adhesion to FN 
in both AFM adhesion assays and cell adhesion assays. The reduced zyxin 
expression significantly impaired cell spreading and reorganization of the actin 
cytoskeleton that could indicate a possible underlying reason for the loss of a 
contractile response to mechanical force. Consistent with these observations, in 
zyxin-silenced VSMC, we also observed a reduced expression of Rac1, which plays 
an important role in the actin reorganization in VSMC, but increased thyroid 
receptor-interacting proteins (TRIP6) and FAK expression, the latter being a 
major protein that promote cell adhesion. In conclusion, these data support an 
important enabling role for zyxin in VSMCs ability to mechanically respond to 
applied force.