Pemphigus foliaceus IgG causes dissociation of desmoglein 1–containing junctions without blocking desmoglein 1 transinteraction
Jens Waschke, Paola Bruggeman, Werner Baumgartner, Detlef Zillikens, Detlev Drenckhahn
Jens Waschke, Paola Bruggeman, Werner Baumgartner, Detlef Zillikens, Detlev Drenckhahn
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Research Article Dermatology

Pemphigus foliaceus IgG causes dissociation of desmoglein 1–containing junctions without blocking desmoglein 1 transinteraction

Abstract

Autoantibodies against the epidermal desmosomal cadherins desmoglein 1 (Dsg1) and Dsg3 have been shown to cause severe to lethal skin blistering clinically defined as pemphigus foliaceus (PF) and pemphigus vulgaris (PV). It is unknown whether antibody-induced dissociation of keratinocytes is caused by direct inhibition of Dsg1 transinteraction or by secondary cellular responses. Here we show in an in vitro system that IgGs purified from PF patient sera caused cellular dissociation of cultured human keratinocytes as well as significant release of Dsg1-coated microbeads attached to Dsg-containing sites on the keratinocyte cellular surface. However, cell dissociation and bead release induced by PF-IgGs was not caused by direct steric hindrance of Dsg1 transinteraction, as demonstrated by single molecule atomic force measurements and by laser trapping of surface-bound Dsg1-coated microbeads. Rather, our experiments strongly indicate that PF-IgG–mediated dissociation events must involve autoantibody-triggered cellular signaling pathways, resulting in destabilization of Dsg1-based adhesive sites and desmosomes.

Authors

Jens Waschke, Paola Bruggeman, Werner Baumgartner, Detlef Zillikens, Detlev Drenckhahn

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Binding activity of Dsg1 in the presence or absence of PF-IgGs probed by...
Binding activity of Dsg1 in the presence or absence of PF-IgGs probed by AFM. (A) General working principle of force-distance cycles. Dsg1-Fc is covalently attached by PEG-linkers to the plate and cantilever tip of the AFM setup. Molecules are brought into contact by downward movement of the tip. During upward movement, a downward deflection of the cantilever will occur if plate- and tip-bound Dsg1 molecules undergo binding (left). Retrace and approach were subtracted, and the area below the resulting curve was integrated and taken as a measure for the average binding activity (right, gray). (B) Bar diagram shows binding activities of Dsg1 molecules in the presence or absence of antibodies. Binding activity was significantly reduced by incubation with EGTA (5 mM, 30 minutes) or the monoclonal antibody directed against Dsg1 (1:50). However, PF-IgGs (35 μg/ml, 30 min) did not reduce binding events in this cell-free system. Fab fragments from the PF-IgG fraction have been applied to rule out possible cross-linking effects of the PF-IgGs and were found not to reduce Dsg1-mediated binding (n = 4 for each condition).