About EFN / Ephrin:
Ephrins go by many names and act as ligands to the Eph receptors, commonly known as Ephrin ligands or Eph family receptor-interacting proteins. The Eph receptors form the largest subfamily of receptor tyrosine kinases (RTKs). Ephrins are cell surface bond proteins. Their differing mode of membrane attachment and structural composition has led scientists to classify them into two subgroups: Ephrin-A and Ephrin-B.
Ephrin-A is anchored to the membrane’s outer leaflet by glycosylphosphatidylinositol (GPI) moiety and lacks a cytoplasmic domain. On the other hand, Ephrin-B is attached to the membrane by a single trans domain that contains a short cytoplasmic PDZ-binding tail. EFNA and EFNB are the genes that encode the Erphin A and Erphin B ligands. In effect, the Eph receptors are classified as EphA or EphB according to their extracellular surface sequence homology and their preference to react to either the EphA or EphB ligands. Today, fourteen Eph receptors have been identified and classified (eight type A receptors and six type B receptors).
Due to these proteins’ membrane-tethered nature, the binding and activation of the Ephrins intercellular signaling pathways can only occur upon cell-cell contact. The Ephrin signaling events such as axon growth cone guidance, tissue formation, cell migration, and segmentation play a vital role during the embryonic development process. These proteins are responsible for maintaining processes like long-term potentiation, angiogenesis, and stem cell differentiation in adulthood.