Ephrin receptors (EphRs) comprise the largest subfamily of receptor tyrosine kinases (RTKs). Class EphB receptors bind to transmembrane ephrin-B ligands. There are six vertebrate EhpB receptors (EphB1-6), which display promiscuous interactions with three ephrin-B ligands. EphB2 plays a role in cell positioning in the gastrointestinal tract by being expressed in proliferating progenitor cells. It also has been implicated in colorectal cancer. A loss of EphB2, as well as EphA4, also precedes memory decline in a murine model of Alzheimers disease. 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.",