Pemphigus Vulgaris and Foliaceus IgG Autoantibodies Directly Block Heterophilic Transinteraction between Desmoglein and Desmocollin.

Anti-desmoglein (Dsg) 1 and Dsg3 IgG autoantibodies in pemphigus foliaceus and pemphigus vulgaris cause blisters through loss of desmosomal adhesion. It is controversial whether blister formation is due to direct inhibition of Dsg, intracellular signaling events causing desmosome destabilization, or both. Recent studies show that heterophilic binding between Dsg and desmocollin (Dsc) is the fundamental adhesive unit of desmosomes. To eliminate cellular contributions to potential pathogenicity of pemphigus antibodies, bead assays coated with recombinant Dsg1, Dsc1, Dsg3, or Dsc3 ectodomains were developed. A mixture of Dsg beads and Dsc beads formed large aggregates, confirming that the heterophilic binding is dominant. The pathogenic anti-Dsg1 and anti-Dsg3 mAbs, which bind the transadhesive interface, blocked the aggregation of Dsg1/Dsc1 and Dsg3/Dsc3 beads, respectively, whereas nonpathogenic mAbs did not. All sera tested from eight patients with pemphigus foliaceus and eight patients with mucosal pemphigus vulgaris with active disease inhibited the adhesion of Dsg1/Dsc1 and Dsg3/Dsc3 beads, respectively. When paired sera obtained from seven patients with pemphigus foliaceus and six patients with pemphigus vulgaris in active disease and remission were compared, the former inhibited aggregation better than the latter. These findings strongly suggest that steric hindrance of heterophilic transinteraction between Dsg and Dsc is important for disease pathology in both pemphigus foliaceus and pemphigus vulgaris.

Generation of an anti-desmoglein 3 antibody without pathogenic activity of pemphigus vulgaris for therapeutic application to squamous cell carcinoma.

It is ideal for the target antigen of a cytotoxic therapeutic antibody against cancer to be cancer-specific, but such antigens are rare. Thus an alternative strategy for target selection is necessary. Desmoglein 3 (DSG3) is highly expressed in lung squamous cell carcinoma, while it is well-known that anti-DSG3 antibodies cause pemphigus vulgaris, an autoimmune disease. We evaluated DSG3 as a novel target by selecting an epitope that exerts efficacy against cancer with no pathogenic effects in normal tissues. Pathogenic anti-DSG3 antibodies induce skin blisters by inhibiting the cell-cell interaction in a Ca2+-dependent manner. We screened anti-DSG3 antibodies that bind DGS3 independent of Ca2+ and have high antibody-dependent cell cytotoxicity (ADCC) activity against DSG3-expressing cells. These selected antibodies did not inhibit cell-cell interaction and showed ADCC activity against squamous cell carcinoma cell lines. Furthermore, one of the DSG3 antibodies showed anti-tumour activity in tumour mouse models but did not induce adverse effects such as blister formation in the skin. Thus it was possible to generate an antibody against DSG3 by using an appropriate epitope that retained efficacy with no pathogenicity. This approach of epitope selection may expand the variety of druggable target molecules.

Cell-cell adhesions and cell contractility are upregulated upon desmosome disruption.

Desmosomes are perturbed in a number of disease states - including genetic disorders, autoimmune and bacterial diseases. Here, we report unexpected changes in other cell-cell adhesion structures upon loss of desmosome function. We found that perturbation of desmosomes by either loss of the core desmosomal protein desmoplakin or treatment with pathogenic anti-desmoglein 3 (Dsg3) antibodies resulted in changes in adherens junctions consistent with increased tension. The total amount of myosin IIA was increased in desmoplakin-null epidermis, and myosin IIA became highly localized to cell contacts in both desmoplakin-null and anti-Dsg3-treated mouse keratinocytes. Inhibition of myosin II activity reversed the changes to adherens junctions seen upon desmosome disruption. The increased cortical myosin IIA promoted epithelial sheet fragility, as myosin IIA-null cells were less susceptible to disruption by anti-Dsg3 antibodies. In addition to the changes in adherens junctions, we found a significant increase in the expression of a number of claudin genes, which encode for transmembrane components of the tight junction that provide barrier function. These data demonstrate that desmosome disruption results in extensive transcriptional and posttranslational changes that alter the activity of other cell adhesion structures.

Desmoglein 3, its pathogenecity and a possibility for therapeutic target in pemphigus vulgaris.

INTRODUCTION: Desmoglein 3 (Dsg3) is one of desmosomal cadherins and functions in epidermal keratinocyte adhesion. IgG anti-Dsg3 autoantibodies are detected in pemphigus vulgaris, an autoimmune bullous disease showing blisters and erosions on the skin and oral mucosa. Other types of pemphigus also show anti-Dsg3 antibodies. Genetic disease of Dsg3 has not been reported. AREAS COVERED: Many in vitro and in vivo studies have indicated pathogenic role of anti-Dsg3 antibodies. Blisters in pemphigus vulgaris are thought to be developed by loss of keratinocyte adhesions by binding of anti-Dsg3 antibodies to Dsg3 through steric hindrance, internalization of Dsg3, changes in molecular integrity or signal transduction. There are pathogenic and nonpathogenic anti-Dsg3 antibodies reactive with different epitopes. Recent studies of pemphigus vulgaris include existence of non-Dsg3 autoantibodies, B cells and T cells reactive with Dsg3, involvement of TNF-α and IL-1 and activation of intracellular signaling. EXPERT OPINION: Although systemic corticosteroids and immunosuppressive agents are mainstays for treatment of pemphigus, intravenous immunoglobulin, plasmapheresis, immunoadsorption, rituximab and TNF-α inhibitors are emerging. Anti-Dsg3 antibody-targeting therapies are reported in mouse model, but they are not yet available clinically. Clarification of pathogenic role of anti-Dsg3 antibodies in pemphigus should provide us with safer and more effective therapies.

RNAi-mediated inhibition of the desmosomal cadherin (desmoglein 3) impairs epithelial cell proliferation.

OBJECTIVES: Desmoglein 3 (Dsg3) is a desmosomal adhesion protein expressed in basal and immediate suprabasal layers of skin. Importance of Dsg3 in cell-cell adhesion and maintenance of tissue integrity is illustrated by findings of keratinocyte dissociation in the autoimmune disease, pemphigus vulgaris, where autoantibodies target Dsg3 on keratinocyte surfaces and cause Dsg3 depletion from desmosomes. However, recognition of possible participation of involvement of Dsg3 in cell proliferation remains controversial. Currently, available evidence suggests that Dsg3 may have both anti- and pro-proliferative roles in keratinocytes. The aim of this study was to use RNA interference (RNAi) strategy to investigate effects of silencing Dsg3 in cell-cell adhesion and cell proliferation in two cell lines, HaCaT and MDCK. MATERIALS AND METHODS: Cells were transfected with siRNA, and knockdown of Dsg3 was assessed by western blotting, fluorescence-activated cell sorting and confocal microscopy. Cell-cell adhesion was analysed using the hanging drop/fragmentation assay, and cell proliferation by colony forming efficiency, BrdU incorporation, cell counts and organotypic culture. RESULTS: Silencing Dsg3 caused defects in cell-cell adhesion and concomitant reduction in cell proliferation in both HaCaT and MDCK cells. CONCLUSION: These findings suggest that Dsg3 depletion by RNAi reduces cell proliferation, which is likely to be secondary to a defect in cell-cell adhesion, an essential function required for cell differentiation and morphogenesis.

Peptides Targeting the Desmoglein 3 Adhesive Interface Prevent Autoantibody-induced Acantholysis in Pemphigus.

Pemphigus vulgaris (PV) autoantibodies directly inhibit desmoglein (Dsg) 3-mediated transinteraction. Because cellular signaling also seems to be required for PV pathogenesis, it is important to characterize the role of direct inhibition in pemphigus acantholysis to allow establishment of new therapeutic approaches. Therefore, we modeled the Dsg1 and Dsg3 sequences into resolved cadherin structures and predicted peptides targeting the adhesive interface of both Dsg3 and Dsg1. In atomic force microscopy single molecule experiments, the self-designed cyclic single peptide specifically blocked homophilic Dsg3 and Dsg1 transinteraction, whereas a tandem peptide (TP) consisting of two combined single peptides did not. TP did not directly block binding of pemphigus IgG to their target Dsg antigens but prevented PV-IgG-induced inhibition of Dsg3 transinteraction in cell-free (atomic force microscopy) and cell-based (laser tweezer) experiments, indicating stabilization of Dsg3 bonds. Similarly, PV-IgG-mediated acantholysis and disruption of Dsg3 localization in HaCaT keratinocytes was partially blocked by TP. This is the first evidence that direct inhibition of Dsg3 binding is important for PV pathogenesis and that peptidomimetics stabilizing Dsg transinteraction may provide a novel approach for PV treatment.

Oral mucosal disease: pemphigus.

Pemphigus defines a group of rare mucocutaneous autoimmune diseases of which pemphigus vulgaris (PV) is the most common. The aetiology and pathogenesis of PV are not completely clear, but there is a fairly strong genetic background: ethnic groups such as Ashkenazi Jews and people of Mediterranean and Indian origin are particularly susceptible and there is a link to HLA class II alleles. The initiating event in PV is not clear, but circulating IgG autoantibodies develop, directed particularly against the intercellular cadherin desmoglein 3 (Dsg3) in desmosomes of stratified squamous epithelium. Oral lesions often herald the disease and are initially vesiculobullous, but they rupture readily to leave ulcers. Involvement of other mucosa and skin is almost inevitable and PV is potentially life threatening. The diagnosis is confirmed by biopsy with histological examination and immunostaining. Management is largely by systemic immunosuppression with corticosteroids, usually azathioprine or other agents, but newer treatments with potentially fewer adverse effects look promising.

DSG3 is overexpressed in head neck cancer and is a potential molecular target for inhibition of oncogenesis.

To identify genes that could potentially serve as molecular therapeutic markers for human head and neck cancer (HNC), we employed differential display analysis to compare the gene expression profiles between HNC and histopathologically normal epithelial tissues. Using reverse transcription-polymerase chain reaction and Western blot analysis, desmoglein 3 (DSG3) was identified as being differentially expressed at both the RNA and protein levels. Of 56 patients assayed, 34 (61%) had overexpression of DSG3, which correlated statistically with T stage (P=0.009), N stage (P=0.047), overall stage (P=0.011), tumor depth (P=0.009) and extracapsular spread in lymph nodes (P=0.044), suggesting that DSG3 participates in carcinogenesis of HNC. Consistent with the clinical findings, inhibition of DSG3 by RNA interference (RNAi) significantly reduced cell growth and colony formation to 57-21% in three HNC cell lines. Use of an in vitro wound healing and Matrigel invasion assays, we found that cell migration and invasive ability were also inhibited to 30-48% in three cell lines tested. An in vivo xenograft study showed that administration of DSG3-RNAi plasmid significantly inhibited tumor growth for 2 months in BALB/C nude mice. In conclusion, DSG3 is identified overexpressed in HNC, with the degree of overexpression associated with clinicopathologic features of the tumor. Inhibition of DSG3 significantly suppresses carcinogenic potential in cellular and in vivo animal studies. These findings suggest that DSG3 is a potential molecular target in the development of adjuvant therapy for HNC.