Early molecular events in the assembly of matrix adhesions at the leading edge of migrating cells

Cellular locomotion is driven by repeated cycles of protrusion of the leading edge, formation of new matrix adhesions and retraction of the trailing edge. In this study we addressed the molecular composition and dynamics of focal complexes, formed under the leading lamellae of motile cells, and their maturation into focal adhesions. We combined phase-contrast and fluorescence microscopy approaches to monitor the incorporation of phosphotyrosine and nine different focal adhesion proteins into focal complexes in endothelial cells, migrating into an in vitro 'wound'. We show that newly formed complexes are located posterior to an actin-, VASP- and alpha-actinin-rich region in the lammelipodium. They are highly…