Figure 1.

Proposed reaction cascade responsible for integrin clustering. Integrin activation by talin yields high-affinity integrin that binds to ECM, becomes immobilized, and creates a binding site for PIP kinase. PIP kinase produces PIP2, which activates talin and produces more high-affinity integrin. Cluster growth is facilitated by diffusion of active integrin or integrin-activating species (i.e., active talin, PIP2) away from the site of initial activation on the tails of bound integrins.