The Eph family of receptors.

Eph receptor tyrosine kinases have recently been identified as instructive molecules that guide the topographic movement of cells and growth cones. The activation of Eph receptors by their ligands, which are membrane-anchored molecules, involves a cell-cell recognition event that often causes cell repulsion. Therefore, Eph receptors mediate signals that can override cell adhesion. Transmembrane ligands for Eph receptors also exhibit properties of signal transducing molecules, suggesting that bidirectional signaling occurs when receptor-expressing cells contact ligand-expressing cells.