Human/Mouse/Rat Contactin‑2/TAG1 Alexa Fluor™ Plus 555‑conjugated Antibody

Contactin-2 (CNTN2), also called TAG1 (transient axonal glycoprotein), TAX1 (transiently-expressed axonal glycoprotein), or axonin-1, is a 135 kDa glycosyl-phosphatidylinositol (GPI)- anchored cell adhesion molecule that belongs to the contactin subfamily within the immunoglobulin (Ig) protein superfamily (1-3). Mouse Contactin-2 cDNA encodes a 30 amino acid (aa) signal peptide, a 984 aa mature secreted protein with 6 Ig-like domains followed by 4 fibronectin type III-like repeats, and a 26 aa C-terminal GPI anchor pro-sequence. GPI-specific phospholipase activity can release soluble, active Contactin-2 from the membrane (2). Mature mouse Contactin-2 shares approximately 93%, 97%, and 77% aa sequence identity with human, rat, and chicken Contactin-2, respectively. During development, Contactin-2 is expressed by a subset of neuronal populations in the central nervous system (CNS) and peripheral nervous system (PNS), particularly during initial phases of axon outgrowth (3-5). Both the 135 kDa form and a 90 kDa form are also upregulated in response to CNS injury in the adult (6). Data support a role for Contactin-2 in axon pathfinding, neurite outgrowth and adhesion, especially in the CNS (3-6). In mature myelinated fibers, Contactin-2 is expressed by oligodendrocytes and Schwann cells, which are myelinating glial cells of the CNS and PNS, respectively (7, 8). It is enriched in the juxtaparanodal regions, where it recruits contactin-associated protein 2 (caspr2), a transmembrane neurexin involved in cell adhesion and intercellular communication (7-10). The axonal Contactin-2 interacts in cis with caspr2 and in trans with another Contactin-2 on the glial membrane (8). This ternary complex is required for the accumulation and organization of K⁺ channels in the juxtaparanodes (9).