Molecular basis of keratinocyte desmosomes and acantholysis using imunoelectron microscopy

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Pemphigus vulgaris(PV) is an autoimmune blistering skin disease caused by binding of autoantibodies to the desmosomal desmoglein 3 (Dsg3). Although it has been confirmed that the autoantibodies themselves are pathogenic and plays a central role of this disease, the mechanism of blister formation in the epidermis alter binding autoantibodies to the autoantigen has not been clarified, yet. In this project, we have investigated the molecular changes in the desmosomes using PV model mice, which produce anti-Dsg3 autoantibodies as well as clinical, histological and immunological phenotype of PV, Dsg3 knockout(-/-) mice, which produce clinical and histological phenotype mimicking PV, and respective control mice. Desmosomal components including Dsg 1, desmocollin(Dsc) 1, Dsc3, plakoglobin(PG), plakophilin 1(Pp1), desmoplakin (DP) were immunolocalized using post-embedding immunogold electron microscopy in each mouse. All the labeling was measured in terms of distance from plasma membrane and number of labeling per desmosome, and statistically analyzed. As results, in Dsg3 -/- mice, the localization of DP shifted 11 nm toward intracellular direction, suggesting a close relationship between Dsg3 and DP. In addition, number of PG in Dsg3 -/- mice decreased significantly. This might be due to the disturbed recruitment of PG in desmosomal formation by lacking Dsg3. The small shift of DP might be caused by the decrease of PG, which is a major ligand of DP to the desmosomal attachment plaque.On the other hand, in PV models mice, DP shifted 24 nm, more markedly than Dsg3 -/- mice, but the number of PG labeling showed no significant changes. This suggests that binding of autoantibody to the Dsg3 may transfer some signals to the cytoplasm and keratin retraction may occur accompanying DP. In conclusion, we have shown that molecular mechanism of blister formation underlying PV model mice and Dsg3 -/- mice is different and that cytoplasmic change did occur after autoantibody binding.