Recombinant Human CXADR Fc Chimera Protein, CF

CXADR (coxsackie and adenovirus receptor), also known as CAR, is a 46 kDa type I transmembrane glycoprotein that belongs to the CTX family of the Ig superfamily (1 - 3). CXADR has received attention as a receptor that facilitates gene transfer mediated by most adenoviruses (1, 2). It is also an adhesion molecule within junctional complexes, notably between epithelial cells lining body cavities and within myocardial intercalated discs (1, 2, 4). CXADR is essential for normal cardiac development in the mouse (7). It is expressed throughout brain neuroepithelium during development, but mainly in ependymal cells in the adult (4 - 6). The 365 amino acid (aa) human CXADR contains a 19 aa signal sequence, a 218 aa extracellular domain (ECD) with a V-type (D1) and a C2-type (D2) Ig-like domain, a 21 aa transmembrane segment and a 107 aa intracellular domain. D1 is thought to be responsible for homodimer formation in trans within tight junctions (2). The fiber knob of adenoviruses attaches at a similar site, and evidence suggests that disruption of tight junctions facilitates virus binding (1, 2). The C-terminus interacts with several cytoplasmic junctional proteins, microtubules and the actin cytoskeleton (1, 8, 9). CXADR interaction with junctional adhesion molecule-like protein (JAML) has been shown to have important functional roles in immunity, inflammation, and tissue homeostatsis (10).The ECD of human CXADR shares 90% aa sequence identity with mouse, rat, and porcine CXADR, and 92% and 89% aa identity with bovine and canine CXADR, respectively. An alternately spliced isoform (CXADR2) that diverges in the C-terminal 15 aa shows a similar expression pattern (4, 11). Transcription of splice variants that produce soluble forms of CXADR has been detected, and secreted forms in serum and pleural fluid potentially block viral infection (12).