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Description

Tenascin-R (UniProt: Q00546, also known as TN-R, Restrictin) is encoded by the TNR gene (Gene ID: 396213) in chicken. Tenascins are a family of four large glycoproteins (Tenascin-C, R, X, and W) that share a cysteine-rich N-terminus, a sequence of fibronectin type III domains, and homologies to fibronectin-b at the C-terminus. Tenascin-R (TN-R), the smallest member of the tenascin family that can exist as homodimer or homotrimer. It interacts with different cells and matrix components and is involved in neural cell adhesion and neurite formation. Its interaction with contactin-1 enhances neurite outgrowth. It is expressed weakly in E6 embryo and reaches a maximum at E16 and declines in the adult. Its expression is observed in oligodendrocytes during myelination, and it accumulates at Ranvier nodes and by a subpopulation of neurons, including cerebellar stellate/basket cells, motoneurons in the spinal cord, and hippocampal interneurons. TN-R is synthesized with a signal peptide (aa 1-33), which is subsequently cleaved off to generate the mature form. Its N-terminal region contains a cysteine-rich segment that it shares with other members of tenascin family. Within this segment there is a stretch of 20 amino acids that form three heptad repeats of hydrophobic amino acids in an a-helix that might generate a triple-stranded coiled coil to link three or two TN-R polypeptides to trimers or dimers. It also contains four EGF-like domains and nine fibronectin type-III (Fn-III) domains. Fn-III 9 mediates cell attachment and Fn-III 2-5 are reported to mediate neurofascin binding. It also contains a fibrinogen C-terminal domain (aa 1124-1339) that mediates its interaction with chondroitin Sulfate Proteoglycan 5. (Ref.: Nörenberg, U., et al. (1995). J. Cell Biol. 130(2), 473-484, Rathjen, FG., et al. (1991). Development.113(1), 151-164).