Eph signaling: a structural view

Eph receptors, the largest subfamily of receptor tyrosine kinases, and their ephrin ligands are important mediators of cell-cell communication regulating cell attachment, shape and mobility. Both Ephs and ephrins are membrane-bound and their interactions at sites of cell-cell contact initiate unique bidirectional signaling cascades, with information transduced in both the receptor-expressing and the ligand-expressing cells. Recent structural and biophysical studies summarized in this review reveal unique molecular features not previously observed in any other receptor-ligand families and explain many of the biochemical and signaling properties of Ephs and ephrins. Of particular importance is the insight into how approximation of ligand-expressing and receptor-expressing cells could lead to the formation and activation of highly ordered signaling centers at cell-cell interfaces.