ESAM

Endothelial cell-selective adhesion molecule (ESAM) is a 55 kDa type I transmembrane glycoprotein that belongs to the JAM family of immunoglobulin superfamily molecules. Human ESAM is synthesized as a 390 amino acid (aa) protein composed of a 29 aa signal peptide, a 216 aa extracellular region, a putative 26 aa transmembrane segment, and a 119 aa cytoplasmic domain. The extracellular region contains one V type and one C2 type Ig domain and is involved in homophilic adhesion. In the cytoplasmic domain, there is a docking site for the multifunctional adaptor protein MAGI. The extracellular region of human ESAM shows 90%, 74%, 69% and 67% aa identity with monkey, canine, mouse and rat extracellular ESAM, respectively. ESAM is expressed on endothelial cells, activated platelets and megakaryocytes, and can be found associated with cellto cell junctions. Whether ESAM is restricted to a particular junctional type is not clear. ESAM deficient mice have no defect in vascularization but do have reduced angiogenic potential. This may be due to a decreased migratory response to FGF-2.