Desmoglein 2 Is Less Important than Desmoglein 3 for Keratinocyte Cohesion

Abstract

Desmosomes provide intercellular adhesive strength required for integrity of epithelial and some non-epithelial tissues. Within the epidermis, the cadherin-type adhesion molecules desmoglein (Dsg) 1–4 and desmocollin (Dsc) 1–3 build the adhesive core of desmosomes. In keratinocytes, several isoforms of these proteins are co-expressed. However, the contribution of specific isoforms to overall cell cohesion is unclear. Therefore, in this study we investigated the roles of Dsg2 and Dsg3, the latter of which is known to be essential for keratinocyte adhesion based on its autoantibody-induced loss of function in the autoimmune blistering skin disease pemphigus vulgaris (PV). The pathogenic PV antibody AK23, targeting the Dsg3 adhesive domain, led to profound loss of cell cohesion in human keratinocytes as revealed by the dispase-based dissociation assays. In contrast, an antibody against Dsg2 had no effect on cell cohesion although the Dsg2 antibody was demonstrated to interfere with Dsg2 transinteraction by single molecule atomic force microscopy and was effective to reduce cell cohesion in intestinal epithelial Caco-2 cells which express Dsg2 as the only Dsg isoform. To substantiate these findings, siRNA-mediated silencing of Dsg2 or Dsg3 was performed in keratinocytes. In contrast to Dsg3-depleted cells, Dsg2 knockdown reduced cell cohesion only under conditions of increased shear. These experiments indicate that specific desmosomal cadherins contribute differently to keratinocyte cohesion and that Dsg2 compared to Dsg3 is less important in this context.

Desmoglein 2 Compensates for Desmoglein 3 but Does Not Control Cell Adhesion via Regulation of p38 Mitogen-activated Protein Kinase in Keratinocytes

“…siRNA). In contrast, following Dsg3 knockdown (40.57 Ϯ 8.32%), Dsg2 levels were not altered (100.17 Ϯ 2.56%) which is in line with previous data (25) (Fig. 2, B-D).…”

“…Dependent on p38 MAPK Signaling-We have shown previously that Dsg2 is of minor importance for keratinocyte cohesion when compared with Dsg3 under conditions of low shear but contributed significantly to cell cohesion under higher mechanic stress (25). Moreover, we detected that Dsg3 forms a complex with p38 MAPK (20).…”

“…siRNA-mediated Gene Silencing-siRNA-mediated gene silencing was performed as described previously (25). ON-Target plus SMARTpool siRNA was purchased from Thermo Scientific/Dharmacon (Lafayette, CO) (human Dsg2 (catalog no.…”

“…Triton X-100 Protein Fractionation-Protein fractionation was carried out as described previously (25). Incubation of HaCaT cells with a buffering system containing 0.5% Triton X-100, 50 mmol/liter MES, 25 mmol/liter EGTA, and 5 mmol/ liter MgCl 2 for 15 min on ice under gentle shaking divided the whole protein pool into a cytoskeleton-anchored (Triton-insoluble) and a cytoskeleton-unanchored (Triton-soluble) fraction.…”

“…In intestinal epithelial cells, in which Dsg2 and Dsc2 are the only expressed desmosomal cadherin isoforms, Dsg2 is important for cell cohesion and maintaining intestinal epithelial barrier integrity (24). However, in keratinocytes, Dsg2 was shown to be important for cell cohesion under conditions of increased shear only (25). In keratinocytes, no specific role for Dsg2 in signaling cascades or overall cell cohesion has been described yet.…”