Recombinant Mouse NCAM-1/CD56 Protein, CF

Neural cell adhesion molecule 1 (NCAM-1; also CD56) is a membrane-bound glycoprotein that plays an important role in nervous system development and function (1, 2). Mature mouse NCAM-1 consists of a 692 amino acid (aa) extracellular domain (ECD) with five tandem Ig-like domains and two fibronectin type III domains, an 18 aa transmembrane segment, and a 386 aa cytoplasmic domain (3). Three major splice variants of NCAM-1 are expressed: the 180 kDa full length NCAM-180 isoform, the 140 kDa NCAM-140 isoform which lacks most of the cytoplasmic domain, and the 120 kDa GPI-anchored NCAM-120 isoform that includes the ECD only. Splicing is tissue specific and developmentally regulated (4 - 6). Within the ECD, mouse NCAM-1 shares 94% and 95% aa sequence identity with human and rat NCAM-1, respectively. It is expressed on neurons and glial cells, skeletal muscle, and immune NK cells (5, 7 - 9). NCAM-1 is extensively modified with polysialic acid (PSA) during development, but this addition is decreased in adult tissues (5, 6, 8). Polysialylation of NCAM-1 is retained in the adult hippocampus where it is important for synaptic plasticity and memory formation (10). The PSA moiety also participates in the binding of NCAM-1 to heparan sulfate proteoglycans and NCAM-1 mediated migration of olfactory neurons (11, 12). Proteolytic shedding of NCAM-1 liberates a soluble ECD fragment that can inhibit cortical neurite branching and growth (6). The NCAM-140 isoform is preferentially expressed on NK cells that robustly secrete cytokines upon activation (9, 13). Selective up‑regulation of the NCAM-140 isoform in a variety of tumors initiates epithelial-mesenchymal transition (EMT) and promotes tumor cell invasion (14, 15). Finally, NCAM-1 is known to interact with a number of transmembrane and extracellular molecules. NK cell NCAM-1 binds to T cell FGF R1, co-stimulating IL-2 production by T cells (16). NCAM-1 also forms a noncovalent membrane complex with GFR alpha1, 2 and 4, generating a receptor for GDNF, NTN and PSP, respectively (17). And NCAM-1 is reported to form homophilic trans-interactions, and to interact with L1 CAM in cis, and with HSPGs (agrin and collagen XVIII) in trans. In general, these interactions are involved in cell adhesion, migration, and/or process extension (18).