One of the remarkable features of cadherin adhesion is its plasticity. This feature is crucial in normal and pathological tissue remodeling. The long-term goal of this project is to define how cadherin-based adhesion combines the strength that keeps cells together with the plasticity that allows for the fast restructuring of cell-cell contacts. Our recent results, outlined in this proposal, suggested a conceptually new model of adherens junction assembly and functioning. We present strong evidence that the cooperative binding of the cadherin-associated protein α-catenin to actin filaments continuously generates cadherin clusters consisting of hundreds of molecules on the cell plasma membrane. The major feature of these clusters is that they are short-lived and are not necessarily engaged in trans-interactions. At the same time, they are highly adhesive because their adhesive interface is reinforced by the intracellular actin scaffold. We propose that such transient, but highly adhesive clusters could be of the basis for the adherens junction plasticity, allowing cells to readjust their junctions during morphogenetic processes. Our preliminary data show that these clusters, their formation, dynamics, and structural characteristics can be studied using advanced imaging techniques such as TIRF microscopy, speckle fluorescent microscopy, single molecule localization microscopy, and platinum replica electron microscopy. In conjunction with biophysical measurements and point mutagenesis, we will determine how actin filaments use these highly adhesive cadherin clusters to manage intercellular adhesion.

PROJECT NARRATIVE Our preliminary studies show that cell-cell adhesion is mediated by transient but highly adhesive cadherin clusters. These clusters are continuously generated by the actin cytoskeleton at the sites of adhesion. The goal of our proposal is to determine the molecular mechanism of this process. Some of the mutants obtained in our study are expected to stabilize cell-cell contacts. Using organotypic keratinocyte culture and Xenopus skin development, we will explore whether such mutants delay epidermal morphogenesis. These mutants will be also tested for rescue the adhesion defect induced by anti-desmosome antibodies. The study is a critical step toward the development of synthetic adhesion modulators and their application in medicine.