Structural and functional characterization of tenascin-R (restrictin), an extracellular matrix glycoprotein of glial cells and neurons.

Tenascin-R (TN-R) is an extracellular matrix protein associated with the surface of neurons and glial cells. Immunohistological studies reveal that TN-R shows a restricted expression pattern in the developing nervous system. TN-R is the smallest member of the tenascin family and is composed of four structural motifs: a cysteine-rich segment at the N-terminus is followed by 4.5 EGF-like repeats. This region is followed by 9 consecutive fibronectin type III (FNIII)-like domains and at the C-terminus TN-R is related to the beta- and gamma- chains of fibrinogen. TN-R forms oligomeric structures as revealed by rotary shadowing electron microscopy of immunoaffinity-purified TN-R. TN-R interacts with the axon-associated F11 protein which results in an enhancement of F11 mediated neurite extension in in vitro assays. In short-term adhesion assays it was found that neural but not fibroblastic cells attach effectively on immobilized TN-R. The cell attachment site within TN-R was allocated to FNIII domain 8 while the site interacting with the F11 protein could be mapped to FNIII domain 2-3.