The mechanism(s) by which neural tumor cells, specifically rat C6 glioma and rat B104 or mouse C1300 neuroblastoma cells, adhere to a model extracellular matrix--the serum-coated tissue culture dish--is being studied with special interest in formation of growth cone adhesions permitting neurite formation with neuroblastoma cells. Detachment of these cells from the dish leaves adhesion sites behind as substratum-attached material (SAM) enriched in glycosaminoglycan (GAG)-containing components, a fibronectin-like glycoprotein (Co), and cell type-specific cytoskeletal proteins. The SAM of neurite-containing cells is unique in containing an uncharacterized high molecular weight polysaccharide (Io). We will determine the SAM composition of three classes of behavioral variants of rat neuroblastoma cells under various growth and attachment conditions. Many approaches will be used to biochemically characterize the Io polysaccaride and the relatedness of the Co glycoprotein to authentic fibroblast fibronectin. The cell surface distribution of some of these components will also be studied. We will determine which of the GAG's exist in the adhesion site as proteoglycans, as well as the reversible formation of supramolecular aggregates of these proteoglycans after dissociative or associative extraction from SAM and the possible binding of Co and Io to these aggregates. Cell-type or neurite-specific aggregates will be of particular interest. These studies should help to elucidate how these two cell types of central nervous system origin adhere to one type of extracellular matrix and whether generation of neurites results from a differing biochemical interaction with the substratum.
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