Project 3: Mechanical and molecular states of adhesions

点击翻译按钮获取中文摘要

Cell migration is regulated by signals that emanate from cell-matrix adhesions. These signals converge on the activation of Rho family GTPases, which regulate actin polymerization and branching, actomyosin contraction, and microtubule dynamics and thereby control the fundamental processes that drive cell migration, e.g., protrusion, adhesion, and polarity^ In turn, the assembly, maturation and signaling of adhesions depend on the forces transmitted through and sensed by adhesions^ (Fig. 1). The feedback between adhesion signaling and force sensing is poorly understood and hence is the focus of this study. The forces on adhesions can arise extracellularly or intracellularly, for example, by contraction of myosin II containing actin filament networks. As a result of the complex interplay between force generation, sensing and signaling (Fig. 1), migrating cells show a spectrum of adhesion morphologies and compositions that appear to represent a continuum of maturation states and signaling differences(3-5. Nascent adhesions form in the lamellipodium, independently of myosin 11 activity, and are precursors to other adhesion types. They signal to Rac to promote actin polymerization and the formation of new nascent adhesions. Paxillin is a major adapter that functions as a Rac signaling hub. When phosphorylated, it brings together signaling components like Cas/Dock180 and GIT1,2/Pix that activate Rac . Large focal adhesions, in contrast, signal to Rho and inhibit phosphorylation of adhesion components like paxillin. FAK is a major scaffold that regulates Rho activity through binding of molecules like p190Rhe-GEF and p190Rho-GAP[10]. Myosin 11 is a major Rho effector whose activity promotes adhesion maturation(11).