In previous work from this laboratory, integral membrane glycoproteins of 120-160 kilodaltons were identified as being involved in cell-substratum adhesion in both mammalian fibroblasts and epithelial cells. More recently, we have been provided with a monoclonal antibody (CSAT Mab) raised against chick myoblast membranes which disrupts cell-matrix adhesion of myoblasts and more subtly perturbs the adhesion of fibroblasts. CSAT Mab recognizes a complex of 3 integral membrane glycoproteins of 120-160 kilodaltons (CSAT ag). In immunofluorescence studies, the CSAT ag complex localizes to leading lamellae, portions of actin containing stress fibers, and to the periphery of stress fiber termini in well spread fibroblasts. In the last location it colocalizes with fibronectin. These glycoproteins are thus located in positions consistent with their playing a direct role in cell-matrix adhesion. The experiments proposed in this application are designed to: (1) produce monoclonal antibodies specific for each member of the 120-160 kilodaltons cell-substratum adhesion glycoprotein complex; (2) localize the members of the glycoprotein complex with respect to one another in the surface membrane at the electron microscope level; (3) localize these glycoproteins with respect to potentially relevant cytoskeletal-association components and extracellular matrix-associated components at the electron microscope level; and (4) study the ultrastructural relationship of the cytoskeleton, surface membrane and extracellular matrix at adhesion sites rich in the CSAT ag using rapid freezing deep-etch techniques. These studies will be carried out on control fibroblasts and myoblasts, and these cells following perturbation of their adhesive properties. Antibodies will also be used to study the role of the CSAT ag in the migration of embryonic cells. Monospecific antibodies against the 120-160 kilodaltons glycoproteins of mammalian cells will also be made in order to study the organization of these adhesion glycoproteins in adherent melanoma cells and a nonadherent variant of these cells. This body of experiments should increase substantially our understanding of the transmembrane signalling mechanisms which determine the adhesive properties of normal, embryonic and malignant cells. (A)
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