Nanoscale structure and function of desmosomes

Project Summary Desmosomes are macromolecular cell-cell adhesive junctions that provide robust mechanical integrity to the epidermis. They are composed of transmembrane desmosomal cadherins, which mediate cell-cell adhesion, and intracellular plaque proteins including desmoplakin, which couple the complex to the intermediate filament cytoskeleton. The functional importance of desmosomes in the skin is highlighted by a variety of inherited human disorders with erosive skin and mucosal phenotypes, that also may affect hair or heart, for which there are limited treatment options. To understand the interplay between desmosome structure and function, it is crucial to appreciate how individual proteins contribute to the overall organization of the desmosome. Yet, due to the size and molecular complexity of desmosomes, there is a lack of tools to study this structure-function relationship, creating a critical barrier in this field. To address this challenge, we will use a multi-disciplinary approach to test the hypothesis that the biophysical organization of proteins in the desmosome provides a mechanism to regulate adhesion. We developed two highly innovative and complementary super-resolution fluorescence microscopy approaches to study protein architecture in desmosomes. Our goal is to elucidate how the order and organization of proteins impact the adhesive function of desmosomes in healthy and disease states. In Aim 1 we will define the mechanism and driving desmoplakin architectural changes and the role of desmoplakin architecture in providing mechanical integrity. In Aim 2 we will define the mechanism that confers order to desmosomal cadherins. In both aims genetic disease associated variants will be introduced to identify architectural contributions to disease mechanism. We will combine innovative fluorescence microscopy with primary human keratinocytes, mechanical stimuli, protein chimeras, and disease associated variants to test the hypothesis that desmosome architecture is inseparably linked to adhesive function. Completion of these goals will provide insight into the fundamental mechanisms of protein architecture that driving desmosome function in healthy and disease states.