Ephrin receptors (EphRs) comprise the largest subfamily of receptor tyrosine kinases (RTKs). Class EphA receptors bind GPI-anchored ephrin-A ligands. There are ten vertebrate EphA receptors (EphA1-10), which display promiscuous interactions with six ephrin-A ligands. A loss of EphA4, as well as EphB2, precedes memory decline in a murine model of Alzheimers disease. EphA4 has been shown to have a negative effect on axon regeneration and functional restoration in corticospinal lesions and is downregulated in some cervical cancers. EphRs contain a ligand binding domain and two fibronectin repeats extracellularly, a transmembrane segment, and a cytoplasmic tyrosine kinase domain. Binding of the ephrin ligand to EphR requires cell-cell contact since both are anchored to the plasma membrane. The resulting downstream signals occur bidirectionally in both EphR-expressing cells (forward signaling) and ephrin-expressing cells (reverse signaling).
Jiyao W et al.(2023). "The conserved domain database in 2023.",