Ephrin Receptor

The Eph receptor tyrosine kinase (RTK) family comprises the largest group of surface receptors and are categorized into EphA or EphB subclasses based on sequence homology and preferential binding to their ephrin-A and ephrin-B ligands, respectively.

In humans, nine EphA (EphA1-8,10) and five EphB (EphB1-4,6) receptors are expressed, along with five ephrin-A and three ephrin-B ligands. Unlike most RTKs, Eph receptors interact with ligands that are often membrane-bound, allowing both “forward signaling” in the receptor-bound cell and “reverse signaling” in the ephrin-bound cell. In addition to “forward signaling,” Eph receptors can signal in the absence of ligand binding and kinase activation through cross-talk with other RTKs, such as HER2.

Eph receptor tyrosine kinases and their ligands, the ephrins, play key roles in the regulation of migration and cell adhesion during development, thereby influencing cell fate, morphogenesis and organogenesis. By now, many Eph receptors and ephrins have also been found to play important roles in the progression of cancer. Therefore, the Eph/ephrin system is considered a promising therapeutic target.