Cell attachment on replicas of SDS polyacrylamide gels reveals two adhesive plasma proteins.

Abstract

A novel procedure that detects adhesive proteins in complex mixtures was used to characterize such proteins in plasma. The proteins are separated by SDS PAGE [sodium dodecyl sulfate-polyacrylamide gel electrophoresis] and transferred to nitrocellulose filters. Cells incubated on these filters attach to those proteins that have adhesive properties. When applied to human plasma proteins this procedure reveals, in addition to fibronectin, a cell-attachment protein with a polypeptide MW of 70,000. A monoclonal antibody that inhibits attachment of [normal rat kidney NRK] cells to fibronectin shows that this polypeptide is not a fragment of fibronectin and evidence is presented that it is a component of the serum spreading factor. Therefore, as defined by the assay, this protein and fibronectin are the major attachment proteins for fibroblastic cells in plasma or serum.