Role of the M-receptor in attachment and spreading of human fibroblasts

Surface molecules are thought to be involved in the attachment and spreading of cells on a substratum coated with specific ligands (Rauvala et al., 1981; Carter et al., 1981; Michl et al., 1979). Since human fibroblasts carry a surface receptor for a 2 Macroglobulin-protease complexes (Van Leuven et al., 1979), we examined whether these cells would attach and spread selectively on a substratum coated with the specific ligand. The presence of the receptor on dissociated cells was demonstrated, as well as the stability of the protein coat on the substratum. Moreover, we determined that the a 2 M-T coat expressed the antigen observed only on molecules which interact selectively with the cells. Cell attachment occurred rapidly on complexed but at the same rate as on uncomplexed a 2 M and on a 2 M derivatized with mono-dansylcadaverine ( a 2 M-DC); the latter was shown not to interact specifically with the cells (Van Leuven et al., 1979). Cell spreading on a 2 M-T was limited and had the same extent as on a 2 M-DC. The cells remained capable of ingesting a 2 M-trypsin complexes during attachment, they did not ingest the a 2 M-trypsin substratum and their attachment or spreading was not inhibited by the addition of an excess a 2 M-trypsin in the attachment medium. Our results do suggest that the a 2 M receptor is not involved in attachment or spreading of fibroblasts on an a 2 M-coat or that its involvement does not result in facilitated spreading of the cells.