Integrins β1 and β3 exhibit distinct dynamic nanoscale organizations inside focal adhesions.

Integrins in focal adhesions (FAs) mediate adhesion and force transmission to extracellular matrices essential for cell motility, proliferation and differentiation. Different fibronectin-binding integrins, simultaneously present in FAs, perform distinct functions. Yet, how integrin dynamics control biochemical and biomechanical processes in FAs is still elusive. Using single-protein tracking and super-resolution imaging we revealed the dynamic nano-organizations of integrins and talin inside FAs. Integrins reside in FAs through free-diffusion and immobilization cycles. Integrin activation promotes immobilization, stabilized in FAs by simultaneous connection to fibronectin and actin-binding proteins. Talin is recruited in FAs directly from the cytosol without membrane free-diffusion, restricting integrin immobilization to FAs. Immobilized β3-integrins are enriched and stationary within FAs, whereas immobilized β1-integrins are less enriched and exhibit rearward movements. Talin is enriched and mainly stationary, but also exhibited rearward movements in FAs, consistent with stable connections with both β-integrins. Thus, differential transmission of actin motion to fibronectin occurs through specific integrins within FAs.

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