Zyxin[Edit]
Zyxin is enriched along actin filaments, stress fiber bundles, and at cell-cell or cell-matrix adhesion sites [1, 2].
Figure 1. Zyxin: This schematic diagram illustrates the molecular organization of zyxin and provides examples for how zyxin is represented in figures throughout this resource.
Zyxin is specifically found in more mature adhesions [3] and its absence in early adhesions is commonly used to distinguish the 'age' of an adhesion [4]. The main function of zyxin is to form a bridge between the adhesion components at the cell membrane and the internal cytoskeleton (reviewed in [5]). Zyxin is vital for coordinating matrix-dependent cues with actin dynamics; for example, within stress fibers and focal adhesions (FAs), zyxin acts as a mechanosensor that binds to areas where forces are applied [6, 7, 8]. Not only is zyxin binding proportional to the mechanical force (e.g. decreased traction reduces zyxin-binding) but its stability at adhesion sites is tension-dependent [9, 10]. Figure 2. Zyxin localization: A NIH3T3 cell, plated on a collagen coated glass slide and transfected with RFP-actin and GFP-zyxin. The basal surface of the cell was imaged using TIRF microscopy, on an Olympus IX81 Inverted microscope at 60x magnification. [Image captured by Machiyama Hiroaki, Mechanobiology Institute, Singapore]
Cellular adaptation to mechanical stress also involves redistribution of zyxin from FAs to stress fibers, which causes stress fiber thickening [11]. Mislocalization of zyxin leads to defects in cell migration and spreading [12, 13] and its absence leads to increased cellular motility [14] presumably through reduced adhesive strength [15]. Zyxin influences actin organization and assembly around FAs by recruiting Ena/VASP [13, 14, 16]; Ena/VASP may subsequently generate new actin filaments by an unknown mechanism that is initiation factor-independent, however, this has not been demonstrated in intact cells [17].