Differential Pathomechanisms of Desmoglein 1 Transmembrane Domain Mutations in Skin Disease.

Dominant and recessive mutations in the desmosomal cadherin, desmoglein (DSG) 1, cause the skin diseases palmoplantar keratoderma (PPK) and severe dermatitis, multiple allergies, and metabolic wasting (SAM) syndrome, respectively. In this study, we compare two dominant missense mutations in the DSG1 transmembrane domain (TMD), G557R and G562R, causing PPK (DSG1 _PPK-TMD ) and SAM syndrome (DSG1 _SAM-TMD ), respectively, to determine the differing pathomechanisms of these mutants. Expressing the DSG1 _TMD mutants in a DSG-null background, we use cellular and biochemical assays to reveal the differences in the mechanistic behavior of each mutant. Super-resolution microscopy and functional assays showed a failure by both mutants to assemble desmosomes due to reduced membrane trafficking and lipid raft targeting. DSG1 _SAM-TMD maintained normal expression levels and turnover relative to wildtype DSG1, but DSG1 _PPK-TMD lacked stability, leading to increased turnover through lysosomal and proteasomal pathways and reduced expression levels. These results differentiate the underlying pathomechanisms of these disorders, suggesting that DSG1 _SAM-TMD acts dominant negatively, whereas DSG1 _PPK-TMD is a loss-of-function mutation causing the milder PPK disease phenotype. These mutants portray the importance of the DSG TMD in desmosome function and suggest that a greater understanding of the desmosomal cadherin TMDs will further our understanding of the role that desmosomes play in epidermal pathophysiology.
(Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)