Biology Reference
In-Depth Information
Figure 5.8 A unifying model presenting roles of actin and microtubule systems in the development of focal adhesions. (A) Tension-dependent
assembly. Rho induces formation of focal adhesions by triggering ROCK and mDia1. The function of ROCK is to activate myosin II-driven cell
contraction via inhibition of myosin-light chain phosphatase (MLCP) and perhaps direct phosphorylation of myosin II light chain (crescent
symbols). Tension applied to mechanosensory focal adhesion plaque (black box) promotes incorporation of new components. Active mDia1
promotes nucleation of linear actin filaments. When tension is applied externally, mDia1 is the only Rho-target that is necessary for focal
adhesion growth. (B) Microtubule-dependent turnover. High levels of active mDia1 in the proximity of the mature focal adhesion lead to
alteration of microtubule dynamics at both plus- and minus-ends. ROCK activity is required for mDia1-induced microtubule minus-end
stabilization. Alteration of the microtubule dynamics may facilitate targeting of their plus-ends to mature focal adhesions. Concentration of
microtubules in the proximity of focal adhesion leads to local inhibition of the myosin-driven contractility in this region, and consequently to
cessation of growth or even disassembly of focal adhesions. Frame (A) is based on the study by Riveline et al. (2001), and is reproduced with
permission from Geiger and Bershadsky (2001)
