Proteases have been used as a tool to investigate the role of surface molecules in fibronectin-mediated cell adhesion. Proteolytic digestion of membrane-proteins by pronase (1 mg/ml for 20 rain at 37°C) completely inhibited adhesion of baby hamster kidney (BHK) fibroblasts on fibronectin-coated plastic dishes. Various degrees of inhibition were also obtained after treatment with proteinase K, chymotrypsin, papain, subtilopeptidase A, and thermolysin. Protein synthesis was required to restore the adhesive properties of pronase-treated cells, showing the protein nature of the molecules involved in adhesion to fibronectin. A peculiar feature of these proteins was their resistance to cleavage by trypsin. After prolonged trypsin treatment (1 mg/ml for 20 min at 37°C), cells adhered and spread on fibronectin-coated dishes, even when protein synthesis was inhibited by 4/-M cycloheximide. Under these conditions only three glycoproteins (gp) of molecular weight 130,000, 120,000, and 80,000 were left on the cell surface. These were precipitated by a rabbit antiserum against BHK cells that also inhibited adhesion of trypsin-treated cells, gp120 and gp80 were left at the cell surface after mild pronase digestion (0.2 mg/ml for 20 min at 37°C), under conditions not affecting adhesion. These data suggest that these glycoproteins may be involved in fibronectinmediated cell adhesion in some as yet unknown way.
ASJC Scopus subject areas
- Cell Biology