Polarized epithelial cells transport ions and solutes between biological compartments separated by the epithelium. These functions require cell- cell interactions and asymmetric distributions of ion channels and transporters between distinct plasma membrane domains that face different compartments. Our long term objectives are to define the roles of cell adhesion in the formation of plasma membrane domains in polarized epithelial cells, and to characterize the cellular machinery involved in targeting and retention of protein at those membrane domains. Our working hypothesis is that cadherin-mediated cell-cell adhesion provides a unique positional cue on the plasma membrane generates localized assembly sites for the membrane-cytoskeleton and membrane protein retention, and for the cellular machinery that specifies docking of cognate transport vesicles delivered from the Golgi complex. We propose five specific aims to critically test element of this hypothesis: 1). Investigate mechanisms involved in generating plasticity in Na/K- ATPase cell surface distributions in epithelial cells by cadherin-mediated adhesion. 2). Define sequential stages in cadherin/catenin and membrane-cytoskeleton (Na/K-ATPase) complex assembly at adhesion sites in vivo. 3). Define protein-protein interactions between cadherin/catenin and membrane-cytoskeleton (Na/K-ATPase) complexes in vitro, and examine functions of protein interactions with cadherin in vivo. 4). Develop an in vitro assay for induction of cadherin-dependent cell adhesion on recombinant-cadherin substrates. 5). Examine the role of cadherin- and integrin-mediated cell adhesion in generating a docking site for cognate transport vesicles. The significance of these studies is that they will elucidate mechanisms involved in generating plasticity in protein distributions in polarized cells, and define protein interactions at adhesion sites that regulate membrane-cytoskeleton recruitment and assembly (protein retention machinery), and formation of sites for binding cognate transport vesicles (vesicle docking machinery). These results will provide a strong foundation for understanding the role of cell adhesion in the generation and maintenance of epithelial cell polarity.