Focal Adhesions and Stress Fibres

In fibroblastic cells and platelets, Ena/VASP proteins are recruited to large protein complexes that anchor long anti-parallel bundles of actin filaments (stress fibres) to cell-matrix adhesion sites called focal adhesions. Several FP4 motif-containing proteins such as zyxin, vinculin, palladin, migfillin and RIAM localise to focal adhesions and are required to recruit Ena/VASP proteins to these sites (Brindle et al. 1996; Reinhard et al. 1996; Drees et al. 2000; Boukhelifa et al. 2004; Han et al. 2006; Jenzora et al. 2005; Zhang et al. 2006). Interestingly, vinculin can recruit both Ena/VASP and Arp2/3 (see below) to focal adhesions where barbed end growth has been observed (DeMali et al. 2002; Machesky and Hall 1997). Zyxin and palladin are also able to recruit Ena/ VASP proteins into a periodical pattern along stress fibres. Interestingly, VASP overexpression in endothelial cells led to an increased formation of stress fibres (Price and Brindle 2000). However, Ena/VASP proteins are not required for stress fibre formation, and the precise function of Ena/VASP in this process is unknown (Bear et al. 2000).

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