Recombinant Mouse EphA1 Protein, CF

EphA1, also known as Eph and Esk, is a member of the Eph receptor tyrosine kinase family and binds several Ephrin-A ligands. The A and B class Eph proteins share a common structural organization (1 - 4). The mouse EphA1 cDNA encodes a 977 amino acid (aa) precursor that includes a 24 aa signal sequence, a 524 aa extracellular domain (ECD), a 21 aa transmembrane segment, and a 408 aa cytoplasmic domain. The ECD contains an N-terminal globular domain, a cysteine-rich domain, and two fibronectin type III domains. The cytoplasmic domain contains a juxtamembrane motif with two tyrosine residues which are the major autophosphorylation sites, a kinase domain, and a conserved sterile alpha motif (SAM) (5, 6). Within the ECD, mouse EphA1 shares 84% aa sequence identity with human EphA1, approximately 40% aa sequence identity with mouse EphA2, 3, 4, 6, 7, and 8, and 27% aa sequence identity with mouse EphA5. A splice variant of mouse EphA1 lacks the transmembrane segment and is predicted to exist as a soluble molecule (7). Membrane bound or clustered Ephrin ligands interact with EphA1 and activate its kinase domain which is capable of Ser, Thr, and Tyr phosphorylation (7). Reverse signaling is propagated through the Ephrin ligand. EphA1 is widely expressed in differentiated epithelial cells, particularly in bone marrow, spleen, thymus, and testes (5, 7). It is expressed on CD4⁺ T cells but not on CD19⁺ B cells (8). On T cells, EphA1 induces Tyr phosphorylation of PYK2 and promotes chemokine-induced chemotaxis (8). EphA1 is upregulated or downregulated in a variety of human carcinomas and is implicated in tumor invasiveness (2, 9, 10).