Comparison of fibronectin receptors from rat hepatocytes and fibroblasts

A cell-surface fibronectin receptor was isolated from primary rat hepatocytes by affinity chromatography on Sepharose conjugated with the cell-binding domain (105 kDa) of fibronectin. The receptor remained bound to the affinity column in the presence of 1 M NaCl but was eluted by 1.5 mM of glycl-arginyl-glycyl-aspartyl-seryl-cysteine peptide or by lowering the pH to 4. The eluted material migrated under nonreducing conditions in sodium dodecyl sulfate-polyacrylamide electrophoresis as two bands: the alpha- and beta-components had apparent Mrs of 155,000 and 115,000, respectively. After reduction the 155-kDa component gave rise to two peptides of Mrs 145,000 and 20,000, while the 115-kDa component shifted migration to an Mr of 130,000. Antibodies specifically recognizing the 155- and 115-kDa proteins from hepatocytes inhibited the attachment of these cells to fibronectin-coated dishes, whereas attachment to dishes coated with collagen or laminin was unaffected. A fibronectin receptor isolated from rat fibroblasts showed closely similar, but not identical, migration in sodium dodecyl sulfate-electrophoresis as the hepatocyte receptor. Furthermore, only the beta-subunit of the fibroblast receptor reacted with the antibodies. The results suggest that distinct alpha-subunits of the fibronectin receptors may be the basis for the different fibronectin-binding properties of these cells.