GLYCOSAMINOGLYCANS IN THE SUBSTRATE ADHESION SITES OF NORMAL AND VIRUS-TRANSFORMED MURINE CELLS

The substrate-attached material of Balb/c 3T3, SV40-transformed, and concanavalin A selected revertant variant cells was examined for its glycosaminoglycan (GAG) distribution during various cellular growth and attachment conditions. This material, the components of which are part of the tissue culture substrate adhesion sites of these cells, is left adherent to the substrate after cells are detached by EGTA treatment. The GAG distribution in substrate-attached material was also compared to the distributions found in the EGTA-detached cells and in the material solubilized during EGTA treatment. These comparisons revealed the following: (1) heparan sulfate accounts for over 80% of the glucosamine-radiolabeled GAG in the adhesion sites of reattaching cells, in contrast to its accounting for only 25-50% of the radiolabeled GAG in the adhesion sites of long-term or pulse-radiolabeled cells; (2) substrate-attached material is relatively enriched for chondroitin 4-sulfate and unsulfated chondroitin and highly depleted of dermatan sulfate when compared to the other cell fractions after long-term or pulse radiolabeling; (3) EGTA-soluble material is enriched for hyaluronic acid and depleted of heparan sulfate; and (4) the ratio of the chondroitins to hyaluronic acid is much higher in substrate-attached material than in cell-associated or EGTA-soluble material and is constant in substrate-attached material for all cell types examined under each set of radiolabeling conditions used. The relative distribution of GAG in all three cell types was remarkably similar. A consideration of these and other observations suggests that cellular adhesion to a tissue culture substrate may be mediated by cell-surface heparan sulfate interacting with a serum receptor protein(s) adsorbed to the substrate. Subsequent cellular detachment, which occurs when the cell body separates from its footpad adhesion sites, may be effected by the accumulation of un-dersulfated chondroitin sulfate-hyaluronic acid proteoglycan complexes at the adhesion site. © 1979, American Chemical Society. All rights reserved.