Recombinant Human Ephrin-A1 Fc Chimera Protein, CF

Ephrin-A1, also known as B61 and LERK-1, is a member of the Ephrin-A family of GPI-anchored ligands that bind and induce the tyrosine autophosphorylation of Eph receptors. Ephrin-A ligands are structurally related to the extracellular domains of the transmembrane Ephrin-B ligands. Eph-Ephrin interactions are widely involved in the regulation of cell migration, tissue morphogenesis, and cancer progression (1, 2). Human Ephrin-A1 is synthesized with an 18 amino acid (aa) signal peptide, a 164 aa mature chain, and a 23 aa C‑terminal propeptide which is removed prior to GPI linkage of Ephrin-A1 to the membrane (3, 4). It can also be released as a soluble molecule (3, 5, 6). The mature 21 ‑ 25 kDa human Ephrin-A1 shares 85% aa sequence identity with mouse and rat Ephrin-A1. Alternate splicing generates an additional isoform that lacks 22 aa in the juxtamembrane region (7).
This short isoform is also expressed on the cell surface and exhibits weakened binding to EphA2 (7). Ephrin-A1 is widely expressed on endothelial and epithelial cells, particularly in the lung, intestine, liver, and skin (4, 8). It is expressed on resting CD4⁺ T cells but is down‑regulated following activation (9, 10). Ligation of Ephrin-A1 on CD4⁺ T cells inhibits cell proliferation and activation, although soluble Ephrin-A1 can promote T cell chemotaxis (9, 10). In cancer, Ephrin-A1 is expressed by tumor cells as well as on the tumor‑associated vasculature (5, 6, 11). It inhibits tumor cell proliferation and migration but also supports tumor growth by promoting angiogenesis (12 ‑ 14). Soluble Ephrin-A1 additionally promotes neuronal survival and neurite extension (15).