Mena binds α5 integrin directly and modulates α5β1 function

Mena is an Ena/VASP family actin regulator with roles in cell migration, chemotaxis, cell-cell adhesion, tumor cell invasion, and metastasis. Although enriched in focal adhesions, Mena has no established function within these structures. We find that Mena forms an adhesion-regulated complex with alpha 5 beta 1 integrin, a fibronectin receptor involved in cell adhesion, motility, fibronectin fibrillogenesis, signaling, and growth factor receptor trafficking. Mena bound directly to the carboxy-terminal portion of the alpha 5 cytoplasmic tail via a 91-residue region containing 13 five-residue LERER repeats. In fibroblasts, the Mena-alpha 5 complex was required for outside-in alpha 5 beta 1 functions, including normal phosphorylation of FAK and paxillin and formation of fibrillar adhesions. It also supported fibrillogenesis and cell spreading and controlled cell migration speed. Thus, fibroblasts require Mena for multiple alpha 5 beta 1-dependent processes involving bidirectional interactions between the extracellular matrix and cytoplasmic focal adhesion proteins.