Involvement of chondroitin sulfates on brain-derived tenascin-R in carbohydrate-dependent interactions with fibronectin and tenascin-C.

Tenascin-R (TN-R), a matrix glycoprotein of the central nervous system (CNS), has been implicated in a variety of cell-matrix interactions involved in the control of axon growth, myelination and cell adhesion to fibronectin during development and regeneration. While most of the functional analyses have concentrated exclusively on the role of the core protein, the contribution of TN-R glycoconjugates present on many potential sites for N- and O-glycosylation is presently unknown. Here we provide evidence that TN-R derived from adult mouse brain expresses chondroitin sulfate (CS) glycosaminoglycans (GAGs), i.e. C-6S and C-4S, that are recognized by the CS/dermatan sulfate-specific monoclonal antibodies 473 HD and CS-56. Using ligand-binding, cell adhesion and neurite outgrowth assays, we show that TN-R-linked CS GAGs (i) are involved in the interaction with the heparin-binding sites of fibronectin and are responsible for TN-R-mediated inhibition of cell adhesion to a 33/66-kD heparin-binding fibronectin fragment or to FN-C/H I and FN-C/H II peptides, known to participate in fibronectin binding to cell surface proteoglycans; and (ii) partially contribute to the interaction between TN-R and TN-C which, however, does not lead to an interference with TN-R- and TN-C-mediated inhibition of neurite outgrowth when the two molecules are offered as a mixed substrate in culture. Our findings suggest the functional implication of TN-R-linked CS GAGs in matrix interactions with fibronectin and TN-C that are likely to contribute to a modulation of cellular behavior and the macromolecular organization of matrix components in the developing or injured adult CNS.