Direct and Quantitative Probing of Desmosome Mechanotransduction - PROJECT SUMMARY Intercellular adhesive junctions, including desmosomes and adherens junctions, connect epithelial cells within a tissue to provide mechanical integrity, regulate cell sorting and migration, and control chemical signals that further instruct cell decisions. In particular, desmosomes resist mechanical stress and respond to mechanical cues to regulate complex cell behaviors to promote differentiation, facilitate migration and wound healing, and mediate other functions critical in development and in diseases of many tissues, including the skin and heart. While significant progress has been made identifying potential load-bearing elements within desmosomes, a huge knowledge gap exists about their roles in epithelial mechanics and mechanotransduction. Specifically, the mechanisms of force regulation across the desmosome-intermediate filament linkage are poorly understood. There is limited direct evidence for when and even whether the molecular components of desmosomes bear mechanical loads, the first step towards mechanotransduction. More importantly, still unaddressed is whether specific desmosome components act as mechanosensors that determine the strength and duration of chemical signaling pathways critical in adapting to mechanical stresses in tissues. Our previous studies showed the capacity of desmosome-intermediate filament linkage in regulating cell mechanics, a role that has long been regarded to belong solely to adherens junctions. This suggests the potential for desmosomal components to participate in force regulation. In this MIRA project, building on these findings and leveraging a newly developed single cell-cell adhesion interrogation platform, we will examine the important, but less studied, role that desmosomes play in epithelial mechanics and in mechanotransduction. We will focus on two major research thrust areas: 1) investigate the role desmosome plays in maintaining the mechanical integrity of epithelial cell- cell junctions and 2) determine its potential in transducing mechanical cues at the junction in coordination with mechanosensitive molecules at the adherens junctions and the actin network. Through a series of studies on epithelial cells with desmosomal components harboring loss- and gain-of-function mutations, we will quantify the contribution from each desmosomal protein in maintaining epithelial mechanical integrity in stressed conditions. We will answer the question: How does actin-based contractility affect desmosome regulation of tension within actin-based adhesive networks? We anticipate providing the first direct observation of desmosome serving as a mechanotransduction site at the cell-cell junction. The proposed studies will enhance our understanding of how desmosomes coordinate chemical and transcriptional pathways in response to mechanical tension in the epithelia, lay the groundwork for similar studies of desmosome mechanosensing in other tissues, and ultimately provide new knowledge to aid in developing treatments for disorders resulting from interference with these adhesive junctions and their mechanosensing pathways.
