Recombinant Human Tenascin R Protein, CF

Tenascin R (TNR) is an extracellular matrix glycoprotein belonging to the tenascin family of adhesion proteins (1 - 3). TNR is expressed in the central nervous system by oligodendrocytes and selected inhibitory interneurons. It shows highest expression during the postnatal period of active myelination and promotes neurite outgrowth and synaptic functions (1, 2). It is essential for formation of perineuronal nets, the mesh-like network of extracellular matrix (ECM) molecules that surrounds some neurons (4). The 180 kDa, 1327 amino acid (aa) form of human TNR contains a signal sequence, three heptad repeats that mediate coiled-coil trimer formation, five EGF-like repeats, nine fibronectin type III repeats (FN), and a C-terminal Ca²⁺-binding fibrinogen-related domain. TNR isoform 2 (160 kDa) lacks a portion of FN#6(aa 773 - 862) (3). Mature human TNR isoform 1 shows 94%, 94%, 93%, 93% and 76% aa identity with bovine, mouse, rat, canine and chicken TNR, respectively. Experiments using recombinant TNR fragments indicate that EGF-like domains are counteradhesive for neurons and microglia and contribute to their migration (1, 5 - 7). This region interacts with immunoglobulin superfamily molecules including contactin, phosphacan and voltage-gated sodium channel beta subunits. However, the fibronectin domains are adhesive for the lectican family of chondroitin sulfate proteoglycans (brevican, aggrican, versican and neurocan; FN 3 - 5), contactin (FN 2 - 3) and sodium channel beta subunits (FN 6 - 8) (6 - 9). These adhesive interactions can compete with each other, but can also contribute to crosslinking of lecticans and contactin with other ECM molecules to form perineuronal nets (9, 10). Post-translational modification of TNR can differ with time and location (11). Notably, glycosylation may include GalNAc-4-SO₄, O-linked sialylated glycans, “brain-type” neutral N-glycans and the HNK-1 carbohydrate epitope that is thought to be involved in regulation of synaptic plasticity (11, 12).