Streptococcus pyogenes is responsible for a wide variety of cutaneous infections ranging from superficial impetigo to fulminant invasive necrotizing fasciitis. Dysfunction of desmosomes is associated with the pathogenesis of cutaneous diseases. We identified streptococcal pyrogenic exotoxin B (SpeB) as a proteolytic factor that cleaves the extracellular domains of desmoglein 1 and 3. In an epicutaneous infection model, lesional skin infected with an speB deletion mutant were significantly smaller as compared to those caused by the wild-type strain. Furthermore, immunohistological analysis indicated cleavage of desmogleins that developed around the invasion site of the wild-type strain. In contrast, the speB mutant was preferentially found on the epidermis surface layer. Taken together, our findings provide evidence that SpeB-mediated degradation of desmosomes has a pathogenic role in development of S. pyogenes cutaneous infection.

In a previous report we have demonstrated that the chymotryptic-like serine protease kallikrein 7 (KLK7/hK7) is overexpressed in pancreatic cancer. In normal skin, hK7 is thought to participate in skin desquamation by contributing in the degradation of desmosomal components, such as desmogleins. Thus, the ability of hK7 to degrade desmogleins was assessed and the effect of hK7 expression on desmoglein 2 was examined in cultured pancreatic cancer cells.

Desmogleins (Dsgs) are cadherin family adhesion molecules essential for epidermal integrity. Previous studies have shown that desmogleins associate with lipid rafts, but the significance of this association was not clear. Here, we report that the desmoglein transmembrane domain (TMD) is the primary determinant of raft association. Further, we identify a novel mutation in the DSG1 TMD (G562R) that causes severe dermatitis, multiple allergies, and metabolic wasting syndrome. Molecular modeling predicts that this G-to-R mutation shortens the DSG1 TMD, and experiments directly demonstrate that this mutation compromises both lipid raft association and desmosome incorporation. Finally, cryo-electron tomography indicates that the lipid bilayer within the desmosome is ∼10% thicker than adjacent regions of the plasma membrane. These findings suggest that differences in bilayer thickness influence the organization of adhesion molecules within the epithelial plasma membrane, with cadherin TMDs recruited to the desmosome via the establishment of a specialized mesoscale lipid raft-like membrane domain.

The expression of desmogleins (DSGs), which are known to be crucial for establishing and maintaining the cell-cell adhesion required for tissue integrity, has been well characterized in the epidermis and hair follicle; however, their expression in other epithelial tissues such as prostate is poorly understood. Although downregulation of classical cadherins, such as E-cadherin, has been described in prostate cancer tissue samples, the expression of desmogleins has only been previously reported in prostate cancer cell lines. In this study we characterized desmoglein expression in normal prostate tissues, and further investigated whether Desmoglein 2 (DSG2) expression specifically can serve as a potential clinical prognostic factor for patients diagnosed with primary prostate cancer.

Autoantibodies, immunoglobulins G (IgG) against the desmosomal proteins desmogleins 1 and 3, play a significant role in the pathogenesis of pemphigus vulgaris. The basic therapy for pemfigus includes systemic corticosteroids, but their use should be as brief as possible because of the severe side effects. In cases of corticosteroid- resistant pemfigus, adjuvant therapy, in particular extracorporeal methods, is used. The most effective and safest extracorporeal therapy is immunosorbtion. Immunosorbtion is based on the removal of pemphigus antibodies from the blood using an affinity sorbent during a therapeutic apheresis procedure. Existing immunosorbents are nonselective and increase the risk of infection. We designed an immunosorbent based on an agarose matrix, Affi-Gel 15, and human recombinant desmoglein 3, as a ligand, for a selective removal of autoantibodies from pemphigus patients' sera. It was shown on a pemphigus experimental model in vivo (neonatal Balb/c mouse model) and in vitro that the immunosorbent can effectively remove desmoglein 3-associated autoantibodies. The experimental results demonstrate that the solid-phase matrix immunosorbent Affi-Gel 15-Dsg3 is a promising product for the development of pemphigus therapy.

Pemphigus is a rare but life-threatening autoimmune skin disease characterized by blistering on skin and/or mucous membranes. The physiological process of blister formation involves IgG antibodies against the desmogleins (Dsgs) and desmocollins (Dscs). Additional autoAbs have also been suggested to mediate the disease heterogeneity, such as anti-thyroid peroxidase (anti-TPO) and antithyroglobulin (anti-Tg) antibodies, the essential culprits of the immune system in autoimmune thyroid diseases.

Desmosomes are adhesion plaques that mediate cell-cell adhesion in many tissues, including the epidermis, and generate mechanical resistance to tissues. The extracellular domains of desmosomal cadherin proteins, desmogleins and desmocollins, are required for the interaction with cadherins of the neighbouring cells, whereas their cytoplasmic tails associate with cytoplasmic proteins which mediate connection to intermediate filaments. Disruption of desmosomal adhesion by mutations, autoantibodies or bacterial toxins results in severe human disorders of e.g. the skin and the heart. Despite the vital role of desmosomes in various tissues, the details of their molecular assembly are not clear. We here show that the two members of the flotillin protein family directly interact with the cytoplasmic tails of desmogleins. Depletion of flotillins in human keratinocytes results in weakened desmosomal adhesion and reduced expression of desmoglein-3, most likely due to a reduction in the desmosomal pool due to increased turnover. In the absence of flotillins, desmoglein-3 shows an altered localisation pattern in the cell-cell junctions of keratinocytes, which is highly similar to the localisation observed upon treatment with pemphigus vulgaris autoantibodies. Thus, our data show that flotillins, which have previously been connected to the classical cadherins, are also of importance for the desmosomal cell adhesion.

Cell adhesion and communication are interdependent aspects of cell behavior that are critical for morphogenesis and tissue architecture. In the skin, epidermal adhesion is mediated in part by specialized cell-cell junctions known as desmosomes, which are characterized by the presence of desmosomal cadherins, known as desmogleins and desmocollins. We identified a cadherin family member, desmoglein 4, which is expressed in the suprabasal epidermis and hair follicle. The essential role of desmoglein 4 in skin was established by identifying mutations in families with inherited hypotrichosis, as well as in the lanceolate hair mouse. We also show that DSG4 is an autoantigen in pemphigus vulgaris. Characterization of the phenotype of naturally occurring mutant mice revealed disruption of desmosomal adhesion and perturbations in keratinocyte behavior. We provide evidence that desmoglein 4 is a key mediator of keratinocyte cell adhesion in the hair follicle, where it coordinates the transition from proliferation to differentiation.

Several sporadic cases, in which direct and indirect immunofluorescence studies simultaneously detected IgG and IgA autoantibodies to keratinocyte cell surfaces, have been reported mainly under the name of IgG/IgA pemphigus. However, there have been no systematic studies for this condition. In this study, we collected 30 cases of this condition from our cohort of more than 5,000 autoimmune bullous disease cases, which were consulted for our diagnostic methods from other institutes, and summarized their clinical and immunological findings. Clinically, there was no male-female prevalence, mean age of disease onset was 55.6 years, and mean duration before this condition was suspected was 18 months. The patients showed clinically bullous and pustular skin lesions preferentially on the trunk and extremities, and histopathologically intraepidermal pustules and blisters with infiltration of neutrophils and eosinophils. Immunologically, ELISAs frequently detected IgG and IgA autoantibodies to both desmogleins and desmocollins. From the characteristic clinical, histopathological, and immunological features, which are considerably different from those in classical IgG types of pemphigus, we propose this disease as a new disease entity with preferential name of intercellular IgG/IgA dermatosis (IGAD). This was the largest study of IGAD to date.

Desmogleins (Dsg2) are the major components of desmosomes. Dsg2 has five extracellular tandem cadherin domains (EC1-EC5) for cell-cell interaction. We had previously confirmed the Dsg2 antibody and its epitope (named KC21) derived from EC2 domain suppressing epithelial-mesenchymal transition and invasion in human cancer cell lines. Here, we screened six peptide fragments derived from EC2 domain and found that KR20, the parental peptide of KC21, was the most potent one on suppressing endothelial colony-forming cell (ECFC) tube-like structure formation. KC21 peptide also attenuated migration but did not disrupt viability and proliferation of ECFCs, consistent with the function to inhibit VEGF-mediated activation of p38 MAPK but not AKT and ERK. Animal studies showed that KC21 peptides suppressed capillary growth in Matrigel implant assay and inhibited oxygen-induced retinal neovascularization. The effects were comparable to bevacizumab (Bev). In conclusion, KC21 peptide is an angiogenic inhibitor potentially useful for treating angiogenesis-related diseases.

Scalp is a unique location for pemphigus because of the abundance of desmogleins localized in hair follicles. Scalp involvement is observed in up to 60% of patients in the course of pemphigus. The lesions may occasionally lead to alopecia. Unforced removal of anagen hairs in a pull test is a sign of high disease activity. Direct immunofluorescence of plucked hair bulbs is considered a reliable diagnostic method in patients with pemphigus. Follicular acantholysis is a characteristic histopathological feature of pemphigus lesions localized on the scalp. Trichoscopy may serve as a supplementary method in the diagnosis of pemphigus. This review summarizes the most recent data concerning scalp involvement in pemphigus vulgaris and pemphigus foliaceus. A systematic literature search was conducted in three medical databases: PubMed, Embase, and Web of Science. The analysis included literature data about desmoglein distribution in hair follicles, as well as information about clinical manifestations, histopathology, immunopathology, and trichoscopy of scalp lesions in pemphigus and their response to treatment.

Desmogleins (DSGs), with the ability to link adjacent cells, have been shown to participate in the development of malignancy. DSG3 was up-regulated in various cancers, including lung, head and neck, and esophagus squamous cell carcinoma, which contributed to the tumor progression. The role of DSG3 in pancreatic ductal adenocarcinoma (PDAC) still remains elusive. Here, the expression of DSG3 was found to be enhanced in pancreatic cancer cell lines in vitro. Functional assays showed that shRNA-mediated knockdown of DSG3 decreased cell viability of pancreatic cancer cells and retarded the cell proliferation, migration and invasion. However, pcDNA-mediated over-expression of DSG3 exhibited reversed effect on pancreatic cancer cell progression. In addition, the in vivo assay demonstrated that transfection of shDSG3 lentiviruses into pancreatic cancer cells repressed the tumorigenicity of PDAC after the cancer cells were transplanted into mice subcutaneously. Elevated DSG3 expression promoted the phosphorylation of Src (p-Src), focal adhesion kinase (p-FAK) and AKT (p-AKT) in vitro, while silence of DSG3 reduced the expression of p-Src, p-FAK and p-AKT both in vitro and in vivo. In conclusion, DSG3, as an oncogene, contributed to the tumorigenicity of PDAC through activating Src-FAK signaling.

The proteins of the galectin family are implicated in many cellular processes, including cell interactions, polarity, intracellular trafficking, and signal transduction. In human and mouse, galectin-7 is almost exclusively expressed in stratified epithelia, notably in the epidermis. Galectin-7 expression is also altered in several human tumors of epithelial origin. This study aimed at dissecting the consequences of galectin-7 overexpression on epidermis structure and functions in vivo.

Desmosomal cadherins, desmogleins (Dsgs) and desmocollins, make up the adhesive core of intercellular junctions called desmosomes. A critical determinant of epithelial adhesive strength is the level and organization of desmosomal cadherins on the cell surface. The Dsg subclass of desmosomal cadherins contains a C-terminal unique region (Dsg unique region [DUR]) with unknown function. In this paper, we show that the DUR of Dsg2 stabilized Dsg2 at the cell surface by inhibiting its internalization and promoted strong intercellular adhesion. DUR also facilitated Dsg tail-tail interactions. Forced dimerization of a Dsg2 tail lacking the DUR led to decreased internalization, supporting the conclusion that these two functions of the DUR are mechanistically linked. We also show that a Dsg2 mutant, V977fsX1006, identified in arrhythmogenic right ventricular cardiomyopathy patients, led to a loss of Dsg2 tail self-association and underwent rapid endocytosis in cardiac muscle cells. Our observations illustrate a new mechanism desmosomal cadherins use to control their surface levels, a key factor in determining their adhesion and signaling roles.

The desmosomal cadherins, desmogleins (Dsgs) and desmocollins (Dscs), comprise the adhesive core of intercellular junctions known as desmosomes. Although these adhesion molecules are known to be critical for tissue integrity, mechanisms that coordinate their trafficking into intercellular junctions to regulate their proper ratio and distribution are unknown. We demonstrate that Dsg2 and Dsc2 both exhibit microtubule-dependent transport in epithelial cells but use distinct motors to traffic to the plasma membrane. Functional interference with kinesin-1 blocked Dsg2 transport, resulting in the assembly of Dsg2-deficient junctions with minimal impact on distribution of Dsc2 or desmosomal plaque components. In contrast, inhibiting kinesin-2 prevented Dsc2 movement and decreased its plasma membrane accumulation without affecting Dsg2 trafficking. Either kinesin-1 or -2 deficiency weakened intercellular adhesion, despite the maintenance of adherens junctions and other desmosome components at the plasma membrane. Differential regulation of desmosomal cadherin transport could provide a mechanism to tailor adhesion strength during tissue morphogenesis and remodeling.

Pemphigus vulgaris is an autoimmune blistering disease of the epidermis, caused by autoantibodies against desmosomal proteins, mainly desmogleins 1 and 3, which induce an impairment of desmosomal adhesion and blister formation. Recent findings have shown that inhibition of immunoglobulin G binding on the neonatal Fc receptor, FcRn, results in reduced autoantibody recycling and shortens their half-life, providing a valid treatment option for PV. We have here analyzed the role of FcRn in human keratinocytes treated with antibodies isolated from pemphigus vulgaris patient or with recombinant anti-desmoglein-3 antibodies that induce pathogenic changes in desmosomes, such as loss of monolayer integrity, aberrant desmoglein-3 localization and degradation of desmoglein-3. We show that blocking IgG binding on FcRn by efgartigimod, a recombinant Fc fragment undergoing clinical studies for pemphigus, stabilizes the keratinocyte monolayer, whereas the loss of desmoglein-3 is not prevented by efgartigimod. Our data show that FcRn may play a direct role in the pathogenesis of pemphigus at the level of the autoantibody target cells, the epidermal keratinocytes. Our data suggest that in keratinocytes, FcRn may have functions different from its known function in IgG recycling. Therefore, stabilization of keratinocyte adhesion by FcRn blocking entities may provide a novel treatment paradigm for pemphigus.

Cilia-related proteins are believed to be involved in a broad range of cellular processes. Retinitis pigmentosa GTPase regulator interacting protein 1-like (RPGRIP1L) is a ciliary protein required for ciliogenesis in many cell types, including epidermal keratinocytes. Here we report that RPGRIP1L is also involved in the maintenance of desmosomal junctions between keratinocytes. Genetically disrupting the Rpgrip1l gene in mice caused intraepidermal blistering, primarily between basal and suprabasal keratinocytes. This blistering phenotype was associated with aberrant expression patterns of desmosomal proteins, impaired desmosome ultrastructure, and compromised cell-cell adhesion in vivo and in vitro. We found that disrupting the RPGRIP1L gene in HaCaT cells, which do not form primary cilia, resulted in mislocalization of desmosomal proteins to the cytoplasm, suggesting a cilia-independent function of RPGRIP1L. Mechanistically, we found that RPGRIP1L regulates the endocytosis of desmogleins such that RPGRIP1L-knockdown not only induced spontaneous desmoglein endocytosis, as determined by AK23 labeling and biotinylation assays, but also exacerbated EGTA- or pemphigus vulgaris IgG-induced desmoglein endocytosis. Accordingly, inhibiting endocytosis with dynasore or sucrose rescued these desmosomal phenotypes. Biotinylation assays on cell surface proteins not only reinforced the role of RPGRIP1L in desmoglein endocytosis, but also suggested that RPGRIP1L may be more broadly involved in endocytosis. Thus, data obtained from this study advanced our understanding of the biological functions of RPGRIP1L by identifying its role in the cellular endocytic pathway.

Transmembrane proteins of the cadherin superfamily, the desmogleins and desmocollins, mediate intercellular adhesion in desmosomes. Autoantibodies to desmoglein 1 (dsg1) are a hallmark of pemphigus foliaceus (PF), a disease characterized by skin blistering resulting from keratinocyte cell detachment. The etiology and pathogenesis of this disease remain poorly understood; however, genetic susceptibility is clearly involved. The aim of this study was to verify if genetic variants of dsg1 influence susceptibility/resistance to endemic PF (fogo selvagem). Two single nucleotide polymorphisms (SNPs) were analyzed: 809 (C,T), a synonymous variation, and 1660 (A,C), a tyrosine<-->serine variation in the fifth extracellular domain. Allelic, haplotypic and genotypic frequencies did not differ significantly between the patient (n=134) and the control (n=227) population samples. Moreover, there is no evidence of interaction between the DSG1 and the HLA-DRB1 and IL6 genes, whose alleles had been found associated with differential susceptibility to PF. The results of this study agree with the described and predicted B- and T-cell epitopes of the dsg1 molecule, which seemingly are not affected by the allelic variation. We conclude that genetic diversity of the autoantigen dsg1 is not a major factor for PF pathogenesis in the Brazilian population.

A possible etiological link between the onset of endemic pemphigus in Tunisia and bites of Phlebotomus papatasi, the vector of zoonotic cutaneous leishmaniasis, has been previously suggested. We hypothesized that the immunodominant P. papatasi salivary protein PpSP32 binds to desmogleins 1 and 3 (Dsg1 and Dsg3), triggering loss of tolerance to these pemphigus target autoantigens. Here, we show using far-Western blot that the recombinant PpSP32 protein (rPpSP32) binds to epidermal proteins with a MW of approximately 170 kDa. Coimmunoprecipitation revealed the interaction of rPpSP32 with either Dsg1 or Dsg3. A specific interaction between PpSP32 and Dsg1 and Dsg3 was further demonstrated by ELISA assays. Finally, mice immunized with rPpSP32 twice per week exhibited significantly increased levels of anti-Dsg1 and -Dsg3 antibodies from day 75 to 120. Such antibodies were specific for Dsg1 and Dsg3 and were not the result of cross-reactivity to PpSP32. In this study, we demonstrated for the first time to our knowledge a specific binding between PpSP32 and Dsg1 and Dsg3, which might underlie the triggering of anti-Dsg antibodies in patients exposed to sand fly bites. We also confirmed the development of specific anti-Dsg1 and -Dsg3 antibodies in vivo after PpSP32 immunization in mice. Collectively, our results provide evidence that environmental factors, such as the exposure to P. papatasi bites, can trigger the development of autoimmune antibodies.

Plakophilin 3 (PKP3) is a recently described armadillo protein of the desmosomal plaque, which is synthesized in simple and stratified epithelia. We investigated the localization pattern of endogenous and exogenous PKP3 and fragments thereof. The desmosomal binding properties of PKP3 were determined using yeast two-hybrid, coimmunoprecipitation and colocalization experiments. To this end, novel mouse anti-PKP3 mAbs were generated. We found that PKP3 binds all three desmogleins, desmocollin (Dsc) 3a and -3b, and possibly also Dsc1a and -2a. As such, this is the first protein interaction ever observed with a Dsc-b isoform. Moreover, we determined that PKP3 interacts with plakoglobin, desmoplakin (DP) and the epithelial keratin 18. Evidence was found for the presence of at least two DP-PKP3 interaction sites. This finding might explain how lateral DP-PKP interactions are established in the upper layers of stratified epithelia, increasing the size of the desmosome and the number of anchoring points available for keratins. Together, these results show that PKP3, whose epithelial and epidermal desmosomal expression pattern and protein interaction repertoire are broader than those of PKP1 and -2, is a unique multiprotein binding element in the basic architecture of a vast majority of epithelial desmosomes.