Domain-Specific Interactions of Talin with the Membrane-Proximal Region of the Integrin β3 Subunit

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Abstract
Activation (affinity regulation) of integrin adhesion receptors controls cell migration and extracellular matrix assembly. Talin connects integrins with actin filaments and influences integrin affinity by binding to the integrins' short cytoplasmic β-tail. The principal β-tail binding site in talin is a FERM domain, comprised of three subdomains (F1, F2, and F3). Previous studies of integrin αIIbβ3 have shown that both F2 and F3 bind the β3 tail, but only F3, or the F2−F3 domain pair, induces activation. Here, talin-induced perturbations of β3 NMR resonances were examined to explore integrin activation mechanisms. F3 and F2−F3, but not F2, distinctly perturbed the membrane-proximal region of the β3 tail. All domains also perturbed more distal regions of the β3 tail that appear to form the major interaction surface, since the β3(Y747A) mutation suppressed those effects. These results suggest that perturbation of the β3 tail membrane-proximal region is associated with talin-mediated integrin activation.