EphrinB2, also known as HtkL,ELF2, LERK5,and NLERK1 (1), is a member of the ephrin ligand family which binds members of the Eph receptor family. All ligands share a conserved extracellular sequence, which most likely corresponds to the receptor binding domain. This conserved sequence consists of approximately 125 amino acids and includes four invariant cysteines. The Bclass ligands are transmembrane proteins which can become tyrosine phosphorylated upon receptor ligation. The cytoplasmic domains are approximately 80 amino acids long and are highly conserved, especially the last 33 amino acids. Several signaling molecules have been shown to interact with the cytoplasmic region, although specific signaling roles have yet to be elucidated. EphrinB2 has been shown to bind EphA4, EphB1, EphB2, EphB3, and EphB4 (2, 3). The extracellular domains of murine and human EphrinB2 share 98% amino acid identity. Only membranebound or Fcclustered ligands are capable of activating the receptor in vitro. While soluble monomeric ligands bind the receptor, they do not induce receptor autophosphorylation and activation (2). In vivo, the ligands and receptors display reciprocal expression (3). It has been found that nearly all the receptors and ligands are expressed in developing and adult neural tissue (3). The Ephrin/Eph families also appear to play a role in angiogenesis (3).
1. Eph Nomenclature Committee [letter]. (1997) Cell 90:403.
2. Flanagan, J.G. and P. Vanderhaeghen (1998) Annu. Rev. Neurosci. 21:309.
3. Pasquale, E.B. (1997) Curr. Opin. Cell Biol. 9:608.