Recombinant Human IGSF4D/CADM2 Protein, CF

IGSF4D is an immunoglobulin superfamily member that is also designated as synaptic cell adhesion molecule 2 (SynCAM 2) and nectin-like protein 3 (Necl-3) (1). The four IGSF4 proteins, designated A, B, C and D, are type I transmembrane glycoproteins expressed mainly in epithelial cells that contain one V-type Ig-like and two C2-type Ig-like domains in their extracellular regions. These domains are characteristically responsible for Ca⁺⁺-independent homophilic and heterophilic interactions in the brain, lung, kidney, bladder, prostate and testis (1-3). Based on homology with other family members, the 437 amino acid (aa) human IGSF4D contains a 355 aa extracellular domain (ECD) that shares > 99% aa identity with corresponding regions of canine and bovine, and 93% aa identity with rat and mouse IGSF4D. Rat and mouse IGSF4D lack an exon at the end of the putative ECD. If this exon is disregarded, aa identity with human IGSF4D rises to > 98%. IGSF4A, B, C and D proteins share 35‑50% aa identity within the ECD. Amino acids found to be critical in other IGSF4 proteins for adhesion and intracellular binding of MAGUK guanylate kinase subfamily proteins are conserved in IGSF4D (3). The expression and function of IGSF4D has not been well characterized. However, in-house quality control data at R&D Systems has shown that, like other family members, IGSF4D has a positive effect on in vitro outgrowth of cortical neurons.