Structure of the PTB domain of tensin1 and a model for its recruitment to fibrillar adhesions.

Tensin is a cytoskeletal protein that links integrins to the actin cytoskeleton at sites of cell-matrix adhesion. Here we describe the crystal structure of the phosphotyrosine-binding (PTB) domain of tensin1, and show that it binds integrins in an NPxY-dependent fashion. Alanine mutagenesis of both the PTB domain and integrin tails supports a model of integrin binding similar to that of the PTB-like domain of talin. However, we also show that phosphorylation of the NPxY tyrosine, which disrupts talin binding, has a negligible effect on tensin binding. This suggests that tyrosine phosphorylation of integrin, which occurs during the maturation of focal adhesions, could act as a switch to promote the migration of tensin-integrin complexes into fibronectin-mediated fibrillar adhesions.