436 The role of the endosomal trafficking complex, the retromer, in regulating desmoglein-1 localization

Abstract

Pemphigus vulgaris (PV) is an autoimmune bullous skin disease characterized by severe epidermal blistering and mucous membrane erosions. PV is caused by antibodies directed against the desmosomal cadherin desmoglein 3 (Dsg3), and in cases involving the skin, both Dsg3 and Dsg1. PV can be assessed clinically using the Pemphigus Disease Area Index (PDAI) and using an ELISA for Dsg IgG titers in patient sera. In vitro, PV IgG activity can be investigated by incubating normal human keratinocytes with PV patient IgG and monitoring changes in desmosomal protein organization and overall strength of cell-cell adhesion using a dispase-based cell-cell dissociation assay. However, the relationship between clinical PV assessments and in vitro activity of patient IgG have not been reported. In the present study, we compared the relationship between the in vitro pathogenicity of PV IgG from 23 patients to their PDAI score and ELISA titers. Overall, Dsg1 ELISA values showed a stronger correlation with PDAI scores (p<0.01) when compared to Dsg3 ELISA (p<0.02). However, the sum of Dsg3 and Dsg1 ELISA values exhibited a highly significant correlation to PDAI (p<0.0005). In vitro, treatment of keratinocytes with patient IgG resulted in a range of alterations in desmosomal protein organization that included Dsg3 clustering, the formation of linear arraylike structures, and endocytosis of Dsg3-PV IgG complexes. Interestingly, the loss of cell-cell adhesion strength as assessed using in vitro dispase cell dissociation assays exhibited a positive correlation with Dsg3 ELISA titers (p<0.005), supporting the validity of the dispase assay as a measure of PV pathogenicity . These findings confirm the association of Dsg ELISA values with PDAI and establish a relationship between Dsg IgG titers in patients and loss of adhesion in cultured keratinocytes.