The long-term goal of this project is to understand how cadherins function to influence cellular behavior. In particular, we are interested in how N-cadherin increases the cell motility and invasive behavior of human epithelial tumor cells. The cadherins are the transmembrane components of the adherens junction, a cell-cell adhesive structure in epithelia and other cells. Thus, the idea that an adhesion protein may be involved in increasing cell motility is a novel one. Cadherins are expressed in a tissue specific manner in normal tissues. Our laboratory discovered that expression of an inappropriate cadherin by an epithelial cell (in this case, N-cadherin rather than the normally expressed E-cadherin) resulted in a cell with increased cell motility and increased invasion.
The specific aims of this proposal are focused on understanding the role N-cadherin plays in modulating cell motility. Specifically, we propose to: 1. Determine the molecular basis of N-cadherin-mediated cell motility. 2. Use a transgenic mouse model to investigate the role of N-cadherin in tumor progression. 3. Determine if N-cadherin plays a role in angiogenesis by modulating the motility of endothelial cells. To accomplish these goals, we will make use of molecular constructs, often made up of chimeric molecules. These constructs will be expressed in cells to observe their effect on cellular behavior and phenotype. Protein-protein interactions will be determined by several means which include coimmunoprecipitation reactions, co-localization in tissue culture cells and yeast two hybrid analysis. Protein-protein interactions will also be analyzed by co-transfecting interaction domains of two proteins into eukaryotic cells followed by co-localization in intact cells (immunofluorescence) and co-immunoprecipitation of cell extracts. We will use a mouse model system to examine the effects of expressing N-cadherin in otherwise normal breast epithelial cells to determine if N-cadherin influences cell behavior only in the contex of a tumor cell. Finally, we will examine the role N-cadherin may play in motility of normal endothelial cells. We predict we will clearly identify regions on n-cadherin that mediate cell motility without effecting cell adhesion. This knowledge may make it possible to generate reagents that could be used to inhibit tumor cell motility without inhibiting cell adhesion. Such reagents might be useful to prevent metastasis of tumor cells and/or angiogenesis of endothelial cells.
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