CONTROL OF EPITHELIAL CELL MOTILITY BY E CADHERIN

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Cell-cell contacts mediated by the calcium-dependent adhesion molecule, E-cadherin, strongly affect the polarity and differentiation of epithelial cells. We have found that E-cadherin also suppresses the movement of epithelial cells. Strikingly, this suppression does not require adhesion mediated by E-cadherin, but instead appears to involve generation of an intracellular motility- suppressing signal. We have determined that part of the E- cadherin cytoplasmic segment, the juxtamembrane 9JM) region, is essential for generating this signal. Our overall goals are to identify the components of this signaling pathway, to determine which aspects of cell motility are suppressed by the signal, and to define the importance of this signal during epidermal development and wound-healing. To define the boundaries of the JM domains, we will analyze the effects on cell movement of JM deletion mutants and dominant-negative forms of the JM region. Components that interact with the JM domain will be identified by comparing the pattern of proteins co-immunoprecipitated with forms of E-cadherin that contain or lack this region, by affinity purification with JM domain fusion proteins, and by use of the yeast two-hybrid system. We will test whether these JM- associated components are involved in the signaling pathway by expressing dominant-negative polypeptides that will block their binding to the JM domain. We will test whether homophilic E- cadherin binding activates MAP kinase. To define cellular responses that may be regulated by this signal, we will determine whether E-cadherin affects membrane ruffling and filopodial extension. Finally, to determine the role of this regulation of motility during skin development and wound-healing, we will create and analyze transgenic mice in which dominant-negative forms of E-cadherin are expressed specifically in basal karatinocytes. Together, these studies will result in a better understanding of the mechanisms by which cell-cell contact regulates epithelial cell motility. Such knowledge will prove useful for enhancing wound healing and controlling carcinoma cell invasion.