Fig. 4.
Mechanosensing of the FA shows biphasic behavior with respect to the FA size. (A) Effective stiffness of a FA as a function of its size and the ECM modulus. (B) Normalized integrin force distribution for FAs of different sizes with EECM = 7.5 kPa. For small FAs, integrin force is almost uniformly distributed. The force is concentrated at the proximal edge as the FA becomes larger. (C) Influence of fiber recruitment index on the effective stiffness–FA size profile with EECM = 7.5 kPa. Fiber recruitment significantly increases the effective stiffness of FA–ECM complex. (D) Schematics for the influence of fiber recruitment: higher fiber recruitment index indicates more cross-link breakage, leading to more fibers and ligands, providing more integrins within the FA. Therefore, fiber recruitment significantly increases the effective stiffness. (E) Generic shape of the FA growth rate as a function of FA size, from which two quantities of central interest, i.e., the nucleation size for the nascent adhesions to develop into mature ones and the stable size for a fully developed FA, can be identified. The value of FA growth rate is only positive when FA size is between these two sizes. E reprinted with permission from ref. 24, with permission from Elsevier (www.sciencedirect.com/science/journal/00063495).