Structural Changes to Desmosome Architecture during Assembly and Maturation

Abstract

Desmosomes are macromolecular cell junctions important in maintaining adhesion and resisting mechanical stress in epithelial and cardiac tissue. Much is known about the structure and function of mature desmosomes however less is known about the desmosome architecture during the processes of assembly, disassembly, and recycling. To understand these processes, it is vital to relate the molecular architecture to its maturing state and adhesive function. Since the initiation of desmosome assembly is calcium dependent, we utilized a calcium switch model where we plate Madin-Darby Canine Kidney cells (MDCK) in low calcium media then switch to high calcium media to initiate and track desmosome assembly over the course of maturation. We confirm that nascent desmosomes are found to interact with the adherens junction protein E-cadherin while mature desmosomes do not. Using direct Stochastic Optical Reconstruction Microscopy (dSTORM), we observe that the nanoscale organization of the desmosomal protein desmoplakin (DP) is dynamically remodeled during the process of maturation as indicated by the narrowing of the plaque-to-plaque distance. These structural changes take place over the same time course as E-cadherin is sorted from the maturing desmosome. This correlation has led us to explore the influence of the membrane environment on corresponding organizational changes throughout desmosome maturation. Understanding desmosome architecture provides keen insight into an important aspect of maintaining epithelial integrity both in healthy states such as in wound repair as well as diseased states in skin like skin blistering or cancer metastasis.