CHARACTERIZATION OF FUNCTIONAL DOMAINS OF THE TENASCIN-R (RESTRICTIN)POLYPEPTIDE - CELL ATTACHMENT SITE, BINDING WITH F11, AND ENHANCEMENTOF F11-MEDIATED NEURITE OUTGROWTH BY TENASCIN-R

The extracellular matrix glycoprotein tenascin-R (TN-R) is a multidoma in protein implicated in neural cell adhesion. To analyze the structur e-function relationship of the different domains of TN-R, several reco mbinant TN-R fragments were expressed in bacterial cells. Two distinct binding regions were localized on the TN-R polypeptide: a region bind ing the axon-associated immunoglobulin (Ig)-like F11 protein and a cel l attachment site. The binding region of the glycosyl-phosphatidylinos itol (GPI)-anchored F11 was allocated to the second and third fibronec tin type III (FNIII)-like domain within TN-R. By using a mutant polype ptide of F11 containing only Ig-like domains, a direct interaction bet ween the Ig-like domains of F11 and FNIII-like domains 2-3 of TN-R was demonstrated. The interaction of TN-R with F11 in in vitro cultures e nhanced F11-mediated neurite outgrowth, suggesting that the combined a ction of F11 and TN-R might be of regulatory influence on axon extensi on. A cell attachment region was identified in the FNIII-like domain e ight of TN-R by domain-specific antibodies and fusion constructs. This site is distinct from the F11 binding site within TN-R.