Figure 7.

The assembly and disassembly of NAs is a force-dependent process. (A and B) Stochastic simulations of the number of bound integrins (thin black lines) and adaptor proteins (thin gray lines) during assembly and disassembly are shown. (A) Under high stress (σ = 0.92σ_c) and starting from the equilibrium S^∗ (thick black horizontal line), integrins within NAs undergo catastrophic unbinding upon crossing the stable manifold of the saddle U^∗ (dotted black horizontal line), leading to disassembly as they diffuse away from the adhesion area. (B) A long-lived NA state is formed, starting from a single integrin-adaptor protein complex, when the applied stress is low (σ = 0.25σ_c). This process is driven primarily by plaque growth toward the metastable state with $A={\tilde{A}}^{\text{∗}}$ (thick gray horizontal line), which, in conjunction with ligand binding, increases N_in, the number of integrins inside the NA, until it crosses the stable manifold of the saddle point U^∗. Beyond the stable manifold of U^∗, the trajectory flows to the stable steady state S^∗. Black horizontal lines are identical to those in (A).