AORTIC SMOOTH-MUSCLE CELLS INTERACT WITH TENASCIN-C THROUGH ITS FIBRINOGEN-LIKE DOMAIN

The extracellular matrix protein tenascin-C is a multidomain protein t hat regulates cell adhesion. We used two different smooth muscle cell subtypes derived hom adult and newborn rat aorta to investigate the in teraction of tenascin-C or its various domains with these cells using an adhesion assay. Newborn cells were three times more adherent to ten ascin-C than adult cells, Tenascin C-adhering cells remained round, wh ereas they spread rapidly on a fibronectin substrate. Adhesion assays showed the interaction between tenascin-C and newborn cells to be pred ominantly RGD-independent, Mg2+ increased newborn cell adhesion to ten ascin-C in a concentration-dependent manner, whereas Ca2+ had no effec t, To analyze the structure-function relationships of different domain s of tenascin-C, we used recombinant full-length fibronectin-like and fibrinogen-like domains and various subdomains corresponding to the al ternatively spliced regions of tenascin-C, The cells adhered to the fi brinogen-like domain but not to the fibronectin-like domain or its sub domains, As with the intact tenascin-C molecule, adherent cells remain ed round, and the Mg2+, but not Ca2+, promoted this interaction, The i nteraction of cells with the fibrinogen-like region was further mapped to a 30-amino acid peptide located near the carboxyl-terminal part of the tenascin-C molecule, The same 30-amino acid peptide was active in promoting cell migration, Our results provide a basis for understandi ng the mechanism of interaction of tenascin-C with smooth muscle cells and a framework for isolating membrane binding sites that mediate the cellular responses to this molecule.