Vinculin forms a directionally asymmetric catch bond with F-actin

Abstract

Vinculin is an actin-binding protein thought to reinforce cell-cell and cell-matrix adhesions. However, how mechanical load affects the vinculin/F-actin bond is unclear. Using a single-molecule optical trap assay, we found that vinculin forms a force-dependent catch bond with F-actin via its tail domain, but with lifetimes that depend strongly on the direction of the applied force. Force toward the pointed end of the actin filament resulted in a bond that was maximally stable at 8 pN, with a mean lifetime (12 s) 10-fold longer than the mean lifetime when force was applied toward the barbed end. A computational model of lamellipodial actin dynamics suggested that the directionality of the vinculin/F-actin bond could establish long-range order in the actin cytoskeleton. The directional and force-stabilized binding of vinculin to F-actin may provide a mechanism by which adhesion complexes maintain front-rear asymmetry in migrating cells.

Structural organization and energy storage in crosslinked actin-assemblies

“…binding proteins and crosslinkers demonstrate a "catchbond" behavior, i.e. their detachment rate decreases with strains in certain range [40,45,46]. Crosslinkers with "catch-bond" behavior in principle could store amounts of energy much greater than the values reached in our simulations.…”

Forced-rupture of Cell-Adhesion Complexes Reveals abrupt switch between two Brittle States

“…• The response of cell adhesion complexes to mechanical forces is diverse, [29][30][31]. Phenomenological theories, based on two state models [32,33], and microscopic theory [34,35] …”

Mechanosensation: A Catch Bond That Only Hooks One Way

“…Vt is a five-helix bundle [17] of which one helix, H1 (Figure 1, left, magenta), was found to unfold in the context of the Vt-actin complex, licensing structural rearrangements in the bundle to facilitate its actin binding and also forming a small additional interface on the filament surface (Figure 1, right, magenta). It is tempting to speculate that the state visualized by cryo-EM represents the strong binding state (state 2) observed by Dunn and colleagues [5]. Here (Figure 1, right), the connection between the talin-binding vinculin head domain (Vh) and Vt (dotted arrow) is directed toward the plus end of the actin filament, and a minus-end-directed force would pull H1 away from the bundle, reinforcing the unfolded state and a strong Vt-actin interaction.…”

“…However, it is well established that cells sense not only the magnitude, but also the direction of physical cues, by mechanisms that remain mysterious: flow-mediated shear stress on endothelia induces inflammatory or atheroprotective signaling depending on the flow direction [1]; left–right asymmetry of vertebrates is established by directional fluid flow in the ventral node of developing embryos [2]; several cell and tissue types re-orient their cytoskeletons and polarize relative to the direction of applied strain or shear stress [3]; and cell migration up extracellular matrix stiffness gradients is thought to mediate development and cancer metastasis [4]. In a recent study, Dunn and colleagues [5] provide important new insight into the molecular-scale basis of the cellular response to directional physical cues by showing differential bond dynamics and strength between two critical mechanotransduction proteins, actin and vinculin, depending on the direction of applied force.…”

“…In their recent paper, Dunn and colleagues [5] used a single-molecule, dual optical tweezers based technique to show that vinculin-actin binding is enhanced by force in a direction-dependent manner, providing the first demonstration of a directionally sensitive catch bond. In their assay, an actin filament suspended between beads held in calibrated optical traps is moved across immobilized vinculin molecules.…”