Recombinant Mouse CRTAM Fc Chimera Protein, CF

CRTAM (Class I-restricted T cell-associated molecule) is a member of the nectin family of the immunoglobulin superfamily. It is expressed by activated CD8⁺ and NK T cells (1 - 4). NK activation receptor engagement, but not cytokines, also induces CRTAM expression on NK cells (4, 5). CRTAM is found in spleen, thymus, small intestine, peripheral blood, and surprisingly, in brain where it is highly expressed by Purkinje cells of the cerebellum (1, 2). Mouse CRTAM is a 388 amino acid (aa), 80 kDa type I transmembrane glycoprotein with a 17 aa signal sequence, a 266 aa extracellular domain (ECD) with a V-type followed by a C1-type Ig-like domain, a 25 aa transmembrane domain and an 80 aa cytoplasmic domain with a potential class I PDZ binding domain (1 - 5). Mouse CRTAM ECD shows 70%, 83% and 66% aa identity with human, rat and dog CRTAM ECD, respectively. The V-type Ig-like domain mediates interaction with the corresponding domain on another nectin family member, IGSF4 (also called TSLC-1, Necl-2, Syncam or SgIGSF) (4, 5). CRTAM is a homodimer on the cell surface but does not show homotypic binding in trans (3 - 5). The high affinity of CRTAM/IGSF4 adhesion allows CRTAM to disrupt IGSF4 homotypic interactions (3 - 5). IGSF4 and T cell receptor co-engagement of CRTAM-expressing CD8+ cells induces increased IFN-gamma or IL-22 production (3, 4). A role for CRTAM in cancer surveillance through NK cell-mediated rejection of IGSF4-expressing tumors has been proposed (3 - 5). IGSF4 is expressed broadly, including on epithelia, neurons, a subset of tonsillar B cells (4, 5), and a rare splenic T zone-restricted BCDA3⁺ dendritic cell population which interacts with CRTAM (3).