Direct measurement of near-nano-Newton forces developed by self-organizing actomyosin fibers bound α-catenin.

Background Information: Actin cytoskeleton contractility plays a critical role in morphogenetic processes by generating forces that are then transmitted to cell-cell and cell-ECM adhesion complexes. In turn, mechanical properties of the environment are sensed and transmitted to the cytoskeleton at cell adhesion sites, influencing cellular processes such as cell migration, differentiation and survival. Anchoring of the actomyosin cytoskeleton to adhesion sites is mediated by adaptor proteins such as talin or α-catenin that link F-actin to transmembrane cell adhesion receptors, thereby allowing mechanical coupling between the intracellular and extracellular compartments.

Talin dissociates from RIAM and associates to vinculin sequentially in response to the actomyosin force.

Cells reinforce adhesion strength and cytoskeleton anchoring in response to the actomyosin force. The mechanical stretching of talin, which exposes cryptic vinculin-binding sites, triggers this process. The binding of RIAM to talin could regulate this mechanism.

Integrin-bound talin head inhibits actin filament barbed-end elongation.

Focal adhesions (FAs) mechanically couple the extracellular matrix to the dynamic actin cytoskeleton, via transmembrane integrins and actin-binding proteins. The molecular mechanisms by which protein machineries control force transmission along this molecular axis ( modulating integrin activation and controlling actin polymerization) remain largely unknown. Talin is a major actin-binding protein that controls both the inside-out activation of integrins and actin filament anchoring and thus plays a major role in the establishment of the actin-extracellular matrix mechanical coupling.