Desmosomes undergo dynamic architectural changes during assembly and maturation

Abstract

Desmosomes are macromolecular cell-cell junctions critical for maintaining adhesion and resisting mechanical stress in epithelial tissue. Desmosome assembly and the relationship between maturity and molecular architecture are not well understood. To address this, we employed a calcium switch assay to synchronize assembly followed by quantification of desmosome nanoscale organization using direct Stochastic Optical Reconstruction Microscopy (dSTORM). We found that the organization of the desmoplakin rod/C-terminal junction changed over the course of maturation, as indicated by a decrease in the plaque-to-plaque distance, while the plaque length increased. In contrast, the desmoplakin N-terminal domain and plakoglobin organization (plaque-to-plaque distance) were constant throughout maturation. This structural rearrangement of desmoplakin was concurrent with desmosome maturation measured by E-cadherin exclusion and increased adhesive strength. Using two-color dSTORM, we showed that while the number of individual E-cadherin containing junctions went down with the increasing time in high Ca 2+ , they maintained a wider desmoplakin rod/C-terminal plaque-to-plaque distance. This indicates that the maturation state of individual desmosomes can be identified by their architectural organization. We confirmed these architectural changes in another model of desmosome assembly, cell migration. Desmosomes in migrating cells, closest to the scratch where they are assembling, were shorter, E-cadherin enriched, and had wider desmoplakin rod/C-terminal plaque-to-plaque distances compared to desmosomes away from the wound edge. Key results were demonstrated in three cell lines representing simple, transitional, and stratified epithelia. Together, these data suggest that there is a set of architectural programs for desmosome maturation, and we hypothesize that desmoplakin architecture may be a contributing mechanism to regulating adhesive strength.

Cytoskeletal anchorage of different Dsg3 pools revealed by combination of hybrid STED/SMFS-AFM

“…Moreover, as the Dsg3 pool at cell contacts is susceptible to PMA treatment, this suggests that these cadherin molecules are already in a complex with Dp. We propose that at this localization the mixed junction of Dsg3 together with E-Cad anchored to the actin cytoskeleton may evolve towards nascent desmosomes in a process where actin anchorage is replaced by Dp binding and intermediate filament cytoskeletal anchorage is paralleled by E-cadherin exclusion as was demonstrated before [47,48] (Fig. 5A).…”

Nanoarchitecture and molecular interactions of epithelial cell junction proteins revealed by super‐resolution microscopy

“…A recent study by Beggs et al indicates that desmoplakin protein goes through an architectural change during desmosome assembly using direct stochastic optical reconstruction microscopy. 44 This finding suggests that some junctional proteins undergo dynamic organizational changes over the course of junctional assembly and maturation processes.…”

Mechanisms Causing Acantholysis in Pemphigus-Lessons from Human Skin

“…Large blisters with associated ultrastructural changes in desmosomes including reduction in desmosome density and size as well as formation of split desmosomes and keratin filament uncoupling from desmosomes was observed in samples treated with PV-IgG (Figures 2A-C) (135) which shows that the skin model reflects the ultrastructural hallmarks known from pemphigus patients' lesions (137,138). Interestingly, the outer and inner plaque could not be differentiated after treatment with PV-IgG, an observation which requires further attention, especially because it has recently been shown that reorganization of the desmosomal plaque occurs during desmosome maturation and it is conceivable that these events may be reverted in pemphigus pathogenesis (139). Also, it must be noted that PV-IgG containing both autoantibodies against Dsg1 and Dsg3 were required for acantholysis whereas mucosal-dominant PV-IgG with autoantibodies against Dsg3 but not against Dsg1 similar to AK23, which is specific for Dsg3, were not sufficient (135).…”