Internalization of Non-Clustered Desmoglein 1 without Depletion of Desmoglein 1 from Adhesion Complexes in An Experimental Model of the Autoimmune Disease Pemphigus Foliaceus

Abstract

Serum antibodies against desmoglein 1 (Dsgl) are known to induce the clinical and histological manifestations of pemphigus foliaceus (PF), autoimmune bullous disease targeting skin. The basic pathophysiological phenomenon of PF blistering is the disruption of epithelial integrity in the granular layer of the epidermis due to separation of keratinocytes from one another, or acantholysis. In this report we investigate the changes in subcellular distribution of Dsgl in response to serum of patients with PF by using an in vitro model of PF. Immunofluorescence analysis on HaCaT cells indicates that non-clustered Dsgl is markedly internalized after exposure to serum. However, binding of PF IgG to Dsgl-rich adhesion complexes (desmosomes) does not cause disruption of such structures nor depletion of clustered Dsgl, as revealed by colocalization ofPF IgG and Dsgl in a punctate staining on cell membrane 24 hours after treatment. Furthermore, morphological studies demonstrate that the dramatic alterations induced by PF sera are not the result of apoptotic programs. Taken together, our data strongly suggest that antiDsgl antibodies from PF serum could cause the internalization of non-clustered Dsgl and perturb the formation of new desmosomes but not directly disrupt Dsgl-containing junctions when stable contacts are already formed.

Removal of amino-terminal extracellular domains of desmoglein 1 by staphylococcal exfoliative toxin is sufficient to initiate epidermal blister formation

“…Two previous reports showed that IgG in serum from patients with PF induces internalization of non-clustered Dsg1, but does not reduce Dsg1 adhesion in vitro [29,30]. In contrast, an in vitro study using cultured keratinocytes reported that IgG in PF serum does not inhibit homophilic trans-interaction of Dsg1 by steric hindrance.…”

Quantitative Analysis of Human Keratinocyte Cell Elasticity Using Atomic Force Microscopy (AFM)

“…Since in vitro cultures of primary human keratinocytes must be carried out under stringent culture requirements and are hindered by their short lifespan in vitro (only 10–15 population doublings before undergoing terminal differentiation), the HaCaT cell line, a spontaneously transformed human adult skin keratinocyte line that maintains full epidermal differentiation capacity and a near normal phenotype was used in the experiment [16]. HaCaT cells have been used extensively to study desmosomal cell junctions [17][18]. This keratinocyte cell line recapitulates normal human differentiation behavior in vitro, particularly in terms of desmosomal kinetics [19].…”

Ultrastructure of acantholysis in pemphigus foliaceus re‐examined from the current perspective

“…6,8,9 Also in PF, antibodies caused depletion of nonjunctional Dsg1 in cultured cells. 19 Although it has long been assumed that little or no Dsg1 is expressed in the basal epidermal layer, in normal human skin we observed a complete transepidermal staining pattern of Dsg1 with an increasing expression upwards from the basal layer. In skin of patients with PF, clustering of Dsg1 clearly starts in the basal layer.…”

“…From cell experiments with PV sera, it is known that PV IgG binds nonjunctional Dsg3, leading to its endocytosis 6,8,9 . Also in PF, antibodies caused depletion of nonjunctional Dsg1 in cultured cells 19 . Although it has long been assumed that little or no Dsg1 is expressed in the basal epidermal layer, in normal human skin we observed a complete transepidermal staining pattern of Dsg1 with an increasing expression upwards from the basal layer.…”