In vivo functional analysis reveals specific roles for the integrin-binding sites of talin.

Adhesion receptors play diverse roles during animal development and require precise spatiotemporal regulation, which is achieved through the activity of their binding partners. Integrins, adhesion receptors that mediate cell attachment to the extracellular matrix (ECM), connect to the intracellular environment through the cytoplasmic adapter protein talin. Talin has two essential functions: orchestrating the assembly of the intracellular adhesion complex (IAC), which associates with integrin, and regulating the affinity of integrins for the ECM. Talin can bind to integrins through two different integrin-binding sites (IBS-1 and IBS-2, respectively). Here, we have investigated the roles of each in the context of Drosophila development. We find that although IBS-1 and IBS-2 are partially redundant, they each have specialized roles during development: IBS-1 reinforces integrin attachment to the ECM, whereas IBS-2 reinforces the link between integrins and the IAC. Disruption of each IBS has different developmental consequences, illustrating how the functional diversity of integrin-mediated adhesion is achieved.