The molecular basis for substrate adhesion in fibroblastic cells will be analyzed in terms of two distinct adhesive cell- substrate contacts, the close and focal contacts, and at the level of three interacting components-the cytoplasmic, cell surface, and substrate ligands. An adhesion defective mutant cell line will be used to probe for critical components in contact formation. A time-resolved analysis of changes in structure and protein composition of the cytoplasmic precursor of the focal contact that occur before and after contact is made will define a sequence of potential functional interactions at the cytoplasmic face of the membrane. An analysis of the ability of natural matrix substrate-ligands to elicit focal and close contacts will define the role of the matrix in controlling expression of the contacts and identify different cell surface receptors involved in contact formation. The myosin affinity technique will be used to selectively isolate, on the basis of transmembrane linkage to actin, cell-surface glycoproteins functional in these two contacts. Collectively, the studies will provide an understanding of the molecular basis of adhesion that will permit future experiments on the regulation of adhesion at the level of transmembrane interations, and on the control of cell movement in development, through changes in adhesion.
