Abstract
It has been well established that intra- and extracellular mechanical environments affect development of focal adhesions (FAs), however, little is known about its molecular mechanisms. FA is a site where actin polymerizes, and the assembly of produced F-actin at FAs is thought to be crucial for FA development. Therefore, certain actin-modulating proteins at FAs may be involved in the mechanical regulation of FA development. In this study, we focused on zyxin, an FA-associated protein having actin polymerizing capability, as a candidate molecule and examined its distribution in response to changes in the mechanical environment in cultured fibloblasts. When cell contractility was inhibited by the myosin II inhibitor, blebbistatin, zyxin dislocated from FAs, which was the earliest remarkable event we could notice. This result suggested that the zyxin assembly at FAs is regulated by the forces applied to FAs. To confirm this idea, we applied uniaxial 50%-stretch to the blebbistatin-treated cells and found that zyxin was reaccumulated at FAs. When fluorescent-labeled G-actin was introduced into permeabilized cells, G-actin was incorporated at zyxin-positive FAs but not at zyxin-negative ones. Incorporation of G-actin at FAs was not observed in the blebbistatin-treated cells, while application of uniaxial stretch restored the G-actin incorporation. These results suggest that zyxin is associated with certain mechano-sensitive machinery at FAs and may regulate actin polymerization at FAs in a force-dependent manner. [J Physiol Sci. 2007;57 Suppl:S118]
