EphA3, also known as Cek4, Mek4, Hek, Tyro4, and Hek4, is a 135kD glycosylated member of the transmembrane Eph receptor tyrosine kinase family. The A and B classes of Eph proteins are distinguished by Ephrin ligand binding preference but have a common structural organization. EphA3 preferentially binds to Ephrin-A5. Eph-Ephrin interactions are widely involved in the regulation of cell migration, tissue morphogenesis, and cancer progression (1, 2). The 521aa extracellular domain (ECD) of human EphA3 contains an N-terminal Ephrin binding region, a cysteine-rich region, and two fibronectin type II domains. The 418 aa cytoplasmic domain contains the tyrosine kinase domain and a sterile alpha motif (SAM) (3, 4). Within the ECD, human EphA3 shares 96% aa sequence identity with mouse and rat EphA3. Alternate splicing generates a secreted isoform that consists of nearly the entire ECD. EphA3 is expressed in the developing forebrain, retinal axons, some spinal cord motor neurons, and the heart where it plays an important role in axonal repulsion and organ morphogenesis (5-8). It is upregulated on some hematopoietic and solid tumor cells and on astrocytes surrounding injured nervous tissue (3, 5, 9-11). EphA3 ligation inhibits cellular adhesion to fibronectin as well as cellular migration (9, 10). Transmembrane EphA3 associates in cis with ADAM10 which then promotes the cleavage in trans of Ephrin-A5 (12). It also associates in cis with Ephrin-A5 on retinal axons, thereby preventing the activation of EphA3 by Ephrin-A (13). Multiple tyrosine residues within the cytoplasmic region of EphA3 become phosphorylated during ligand-induced signaling (14, 15). Source: Recombinant corresponding to aa1-541 of human EphA3 at N-terminus and Human IgG1 aa100-330 at C-terminus, expressed in mouse myeloma cell line, NS0. Molecular Weight: ~85.4kD Endotoxin Level: 1EU/1ug (LAL) Biological Activity: Measured by its binding ability in a functional ELISA. When recombinant human EphA3 Fc Chimera is coated at 2ug/ml (100ul/well), the concentration of biotinylayed rhEphrin A5 Fc Chimera that produces 50% of the optimal binding response is found to be ~5-25ng/ml. Storage and Stability: Lyophilized and reconstituted products are stable for 6 months after receipt at -20C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
