EGFR Inhibition by Erlotinib Rescues Desmosome Ultrastructure and Keratin Anchorage and Protects Against Pemphigus Vulgaris IgG-Induced Acantholysis in Human Epidermis.

Pemphigus is a severe blistering disease caused by autoantibodies primarily against the desmosomal cadherins desmoglein (DSG)1 and DSG3 which impair desmosome integrity. Especially for the acute phase, additional treatment options allowing to reduce corticosteroids would fulfill an unmet medical need. Here, we provide evidence that epidermal growth factor receptor (EGFR) inhibition by erlotinib ameliorates pemphigus vulgaris immunoglobulin G (PV-IgG) -induced acantholysis in intact human epidermis. PV-IgG caused phosphorylation of EGFR (Y845) and SRC in human epidermis. In line with that, a phosphotyrosine kinome analysis revealed a robust response associated with EGFR and SRC family kinase signaling in response to PV-IgG but not pemphigus foliaceus autoantibodies. Erlotinib inhibited PV-IgG-induced epidermal blistering and EGFR phosphorylation, loss of desmosomes as well as ultrastructural alterations of desmosome size, plaque symmetry, keratin filament insertion and restored the desmosome midline considered as hallmark of mature desmosomes. Erlotinib enhanced both single molecule DSG3 binding frequency and strength and delayed DSG3 fluorescence recovery supporting that EGFR inhibition increases DSG3 availability and cytoskeletal anchorage. Our data indicate that EGFR is a promising target for pemphigus therapy due to its link to several signaling pathways known to be involved in pemphigus pathogenesis.

A comprehensive analysis of mRNA expression profiles of Esophageal Squamous Cell Carcinoma reveals downregulation of Desmoglein 1 and crucial genomic targets.

AIM: Esophageal Squamous Cell Carcinoma (ESCC) is a histological subtype of esophageal cancer that begins in the squamous cells in the esophagus. In only 19% of the ESCC-diagnosed patients, a five-year survival rate has been seen. This necessitates the identification of high-confidence biomarkers for early diagnosis, prognosis, and potential therapeutic targets for the mitigation of ESCC. METHOD: We performed a meta-analysis of 10 mRNA datasets and identified consistently perturbed genes across the studies. Then, integrated with ESCC ATLAS to segregate 'core' genes to identify consequences of primary gene perturbation events leading to gene-gene interactions and dysregulated molecular signaling pathways. Further, by integrating with toxicogenomics data, inferences were drawn for gene interaction with environmental exposures, trace elements, chemical carcinogens, and drug chemicals. We also deduce the clinical outcomes of candidate genes based on survival analysis using the ESCC related dataset in The Cancer Genome Atlas. RESULT: We identified 237 known and 18 novel perturbed candidate genes. Desmoglein 1 (DSG1) is one such gene that we found significantly downregulated (Fold Change =-1.89, p-value = 8.2e-06) in ESCC across six different datasets. Further, we identified 31 'core' genes (that either harbor genetic variants or are regulated by epigenetic modifications) and found regulating key biological pathways via adjoining genes in gene-gene interaction networks. Functional enrichment analysis showed dysregulated biological processes and pathways including "Extracellular matrix", "Collagen trimmer" and "HPV infection" are significantly overrepresented in our candidate genes. Based on the toxicogenomic inferences from Comparative Toxicogenomics Database we report the key genes that interacted with risk factors such as tobacco smoking, zinc, nitroso benzylmethylamine, and drug chemicals such as cisplatin, Fluorouracil, and Mitomycin in relation to ESCC. We also point to the STC2 gene that shows a high risk for mortality in ESCC patients. CONCLUSION: We identified novel perturbed genes in relation to ESCC and explored their interaction network. DSG1 is one such gene, its association with microbiota and a clinical presentation seen commonly with ESCC hints that it is a good candidate for early diagnostic marker. Besides, in this study we highlight candidate genes and their molecular connections to risk factors, biological pathways, drug chemicals, and the survival probability of ESCC patients.

Serologic Biomarkers in Pemphigus Monitoring: C-reactive Protein, Macrophage Migration Inhibitory Factor, and Prolactin Levels Versus Autoantibody Assays.

Evaluation and monitoring of pemphigus vulgaris (PV) typically involve autoantibody detection by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence (IIF). We aimed to determine the levels of antipemphigus immunoglobulin (Ig) G autoantibodies using ELISA and IIF (as standard biomarkers), and compare it to prolactin, macrophage migration inhibitory factor (MIF), and C-reactive protein (CRP) (as nonstandard biomarkers) to determine which of these non-standard biomarkers is appropriate for PV monitoring. The experiment was performed before and during therapy. Anti-Dsg immunoglobulin G autoantibodies were measured using ELISA and IIF (as standard biomarkers) versus prolactin, MIF, and CRP (nonstandard), before 1 and 3 months after the treatment. Before beginning the treatment, the severity of the disease was determined using the pemphigus disease area Index (PDAI). We enrolled 60 newly diagnosed patients with PV (32 men and 28 women; mean age=43.8±14.2 years). Before treatment, the levels of anti-Dsg1, anti-Dsg3, and IIF were high and had a significant relationship with PDAI. PDAI also had a connection with the levels of CRP and prolactin. The anti-Dsg1, anti-Dsg3, IIF, and CRP titers decreased in patients treated with conventional (prednisolone plus azathioprine) and rituximab therapy during and after treatment. In conclusion, anti-Dsg1, anti-Dsg3, and IIF autoantibody titers remain standard biomarkers for assessing disease activity, severity, and PV monitoring. The trend of CRP was similar to that of anti-Dsg1, anti-Dsg3, and IIF. Thus, CRP may be used for PV monitoring.

Desmosomal Cadherins in Health and Disease.

Desmosomal cadherins are a recent evolutionary innovation that make up the adhesive core of highly specialized intercellular junctions called desmosomes. Desmosomal cadherins, which are grouped into desmogleins and desmocollins, are related to the classical cadherins, but their cytoplasmic domains are tailored for anchoring intermediate filaments instead of actin to sites of cell-cell adhesion. The resulting junctions are critical for resisting mechanical stress in tissues such as the skin and heart. Desmosomal cadherins also act as signaling hubs that promote differentiation and facilitate morphogenesis, creating more complex and effective tissue barriers in vertebrate tissues. Interference with desmosomal cadherin adhesive and supra-adhesive functions leads to a variety of autoimmune, hereditary, toxin-mediated, and malignant diseases. We review our current understanding of how desmosomal cadherins contribute to human health and disease, highlight gaps in our knowledge about their regulation and function, and introduce promising new directions toward combatting desmosome-related diseases.

Double-filtration plasmapheresis combined with immunosuppressive treatment for severe pemphigus: 10 years' experience of a single center in China.

BACKGROUND: Pemphigus is a group of rare and severe autoimmune blistering disease mediated by pathogenic autoantibodies against desmogleins. Plasmapheresis can directly remove autoantibodies from circulation, which has been applied to the treatment of pemphigus as an adjuvant therapy. But the results of the researches are controversial. This study aims to evaluate the efficacy and safety of double filtration plasmapheresis (DFPP) combined with immunosuppressive treatment for patients with severe pemphigus in our single center. METHODS: We retrospectively analyzed 17 patients with severe pemphigus who were unresponsive to high-dose corticosteroid and received DFPP treatment between January 2010 and January 2020. The information on demographic characteristics, clinical and laboratory data, treatment regimens, and clinical outcomes were collected. RESULTS: All the patients were diagnosed as severe pemphigus and had a period of at least 1 week of high-dose prednisone (1-1.5 mg/kg/day), but they were unresponsive to corticosteroid and immunosuppressants treatment. They received DFPP treatment as an adjuvant therapy. After DFPP treatment, the titers of desmogleins antibodies significantly decreased (P < .001), Nikolsky's sign became negative and no new blisters appeared. The dosage of corticosteroid could begin to taper down rapidly in 9 ± 4 days. On discharge, the dosage of prednisone decreased significantly (51 ± 3 mg/day, P < .001). No major adverse events happened that could lead to the termination of DFPP treatment. CONCLUSION: Double filtration plasmapheresis combined with immunosuppressive treatment is an effective and safe therapeutic regimen for severe pemphigus. DFPP can also contribute to the dosage reduction of steroid to avoid more drug-related side effect.

Pemphigus vulgaris

Abstract: Pemphigus vulgaris is a chronic autoimmune bullous dermatosis that results from the production of autoantibodies against desmogleins 1 and 3. It is the most frequent and most severe form of pemphigus, occurring universally, usually between 40 and 60 years of age. It usually begins with blisters and erosions on the oral mucosa, followed by lesions on other mucous membranes and flaccid blisters on the skin, which can be disseminated. There is a clinical variant, pemphigus vegetans, which is characterized by the presence of vegetating lesions in the large folds of the skin. Clinical suspicion can be confirmed by cytological examination, histopathological examination, and direct and indirect immunofluorescence tests. The treatment is performed with systemic corticosteroids, and immunosuppressive drugs may be associated, among them azathioprine and mycophenolate mofetil. More severe cases may benefit from corticosteroids in the form of intravenous pulse therapy, and recent studies have shown a beneficial effect of rituximab, an anti-CD20 immunobiological drug. It is a chronic disease with mortality around 10%, and septicemia is the main cause of death. Patients need long-term and multidisciplinary follow-up.

Characteristics of multicellular tumor spheroids formed by pancreatic cells expressing different adhesion molecules.

AIMS: Multicellular tumor spheroids (MCTS) produced by different methods vary in forms, sizes, and properties. The aim of this work was to characterize MCTS formed by six pancreatic cell lines on a non-adherent surface. MATERIALS AND METHODS: Human pancreatic cells were grown in 2D and 3D conditions and compared for the expression of E- and desmosomal cadherins (PCR, confocal microscopy), growth, cell cycling, apoptosis (flow cytometry), and a response to antitumor drugs doxorubicin and gemcitabine (MTT-assay). KEY FINDINGS: Three types of MCTS were identified: BxPC-3, T3M4 formed small number of large and dense spheroids representing type I MCTS; COLO-357 and AsPC-1 generated type II multiple and loose MCTS of different sizes while MiaPaCa-2 and PANC-1 represented type III cultures which grew almost as floating monolayer films. Formation of type I MCTS depended on the simultaneous expression of DSG3 and several DSC proteins; II MCTS expressed solely DSG2-DSC2 but not DSG3, while type III cells either did not express E-cadherin or a pair of DSG and DSC proteins. Cells in type I MCTS but not in types II and III ones quickly became quiescent which correlated with a decrease in the proliferation, increased apoptosis, and a higher resistance to antitumor drugs doxorubicin and gemcitabine. SIGNIFICANCE: Taken collectively, pancreatic cells significantly vary in the expression of desmosomal cadherins, resulting in the formation of MCTS with different characteristics. The sensitivity of MCTS to various drugs depends on the type of cells and the method of spheroid preparation used.

Desmoglein 4 gene mutation analysis in a pedigree with autosomal recessive hereditary monilethrix / 中华皮肤科杂志

A 3-year-old female proband presented with patchy follicular keratotic papules on the hairless scalp after birth. At about the age of 2 years, sparse hairs of non-uniform thickness began to grow, but they fell out intermittently and were broken easily. Some eyebrows and eyelashes of different lengths fell out or were broken. Physical examination revealed good condition of nutrition, normal height, weight and intelligence, with no obvious abnormalities in other systems. Skin examination showed sparse and broken hairs with follicular keratotic papules on the vertex and occiput. Teeth, nails, toenails and sweat glands were normal. Dermoscopy, optical microscopy and scanning electron microscopy all showed that affected hairs gave a beaded appearance. Gene sequencing showed that the proband carried heterozygous deletions of exons 2-16 in the desmoglein 4 (DSG4) gene, and a heterozygous mutation c.574T>C (p.S192p) (NM-177986) in the DSG4 gene, which were inherited from her father and mother respectively. None of the above mutations in the DSG4 gene were found in 100 healthy controls. According to the gene sequencing results and clinical phenotype, the patient was finally diagnosed with autosomal recessive hereditary monilethrix, and the c.574T>C mutation and heterozygous deletions of exons 2-16 of the DSG4 gene may contribute to autosomal recessive hereditary monilethrix in the child.

Desmoglein 4 gene mutation analysis in a pedigree with autosomal recessive hereditary monilethrix / 中华皮肤科杂志

A 3-year-old female proband presented with patchy follicular keratotic papules on the hairless scalp after birth.At about the age of 2 years,sparse hairs of non-uniform thickness began to grow,but they fell out intermittently and were broken easily.Some eyebrows and eyelashes of different lengths fell out or were broken.Physical examination revealed good condition of nutrition,normal height,weight and intelligence,with no obvious abnormalities in other systems.Skin examination showed sparse and broken hairs with follicular keratotic papules on the vertex and occiput.Teeth,nails,toenails and sweat glands were normal.Dermoscopy,optical microscopy and scanning electron microscopy all showed that affected hairs gave a beaded appearance.Gene sequencing showed that the proband carried heterozygous deletions of exons 2-16 in the desmoglein 4 (DSG4) gene,and a heterozygous mutation c.574T＞C(p.S192p)(NM-177986) in the DSG4 gene,which were inherited from her father and mother respectively.None of theabove mutations in the DSG4 gene were found in 100 healthy controls.According to the gene sequencing results and clinical phenotype,the patient was finally diagnosed with autosomal recessive hereditary monilethrix,and the c.574T ＞ C mutation and heterozygous deletions of exons 2-16 of the DSG4 gene may contribute to autosomal recessive hereditary monilethrix in the child.

Keratinocyte Binding Assay Identifies Anti-Desmosomal Pemphigus Antibodies Where Other Tests Are Negative.

The serological diagnosis of pemphigus relies on the detection of IgG autoantibodies directed against the epithelial cell surface by indirect immunofluorescence (IIF) on monkey esophagus and against desmoglein 1 (Dsg1) and Dsg3 by ELISA. Although being highly sensitive and specific tools, discrepancies can occur. It is not uncommon that sera testing positive by ELISA give a negative result by IIF and vice versa. This brings diagnostic challenges wherein pemphigus has to be ascertained or ruled out, especially when no biopsy is available. We utilized the ability of anti-Dsg3 and anti-Dsg1 IgG to bind in specific desmosomal patterns to living cells to investigate these discrepancies between IIF and ELISA. Living cultured primary normal human keratinocytes were grown under differentiating conditions to induce adequate expression of Dsg1 and Dsg3, incubated with patient serum for 1 h, and then stained to visualize bound IgG. We investigated two different groups; sera from patients with a positive direct immunofluorescence (DIF) and inconsistent serological findings (n = 43) and sera with positive ELISA or IIF but with negative DIF (n = 60). As positive controls we used 50 sera from patients who fulfilled all diagnostics criteria, and 10 sera from normal human subjects served as negative controls. In the DIF positive group, IgG from 39 of the 43 sera bound to the cells in a desmosomal pattern while in the DIF negative group none of the 60 sera bound to the cells. This shows that for pemphigus patients, ELISA and IIF can be negative while anti-desmosomal antibodies are present and vice versa that ELISA and IIF can be positive in non-pemphigus cases. In absence of a biopsy for DIF, such findings may lead to misdiagnosis.

Streptococcal Cysteine Protease-Mediated Cleavage of Desmogleins Is Involved in the Pathogenesis of Cutaneous Infection.

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.

A Case of Concomitant Pemphigus Foliaceus and Oral Pemphigus Vulgaris.

Pemphigus is a chronic autoimmune condition that can affect multiple areas of the body. The two main subtypes of pemphigus are pemphigus vulgaris (PV) and pemphigus foliaceus (PF) which can rarely occur concurrently or even transition from one to the other. The process of transition may be explained by qualitative changes in desmoglein autoantibody profile. We present a rare case of concomitant PF and oral PV and explore the literature on transitions between pemphigus subtypes and whether this case could represent a transition from PF to PV. Furthermore, the realities of multidisciplinary patient management are discussed.

Evaluating the Efficacy of Double-Filtration Plasmapheresis in Treating Five Patients With Drug-Resistant Pemphigus.

Double-filtration plasmapheresis is an effective and safe treatment for pemphigus. We retrospectively evaluated the decrease in autoantibody titer and pemphigus disease area index following double-filtration plasmapheresis in five patients with moderate to severe pemphigus, who were physically and/or serologically unresponsive to 1.0 mg/kg per day of prednisolone and other supportive drugs and ointments. The percentage reduction in autoantibodies 85.6 ± 14.4% (P = 0.00014), and that in pemphigus disease area index was 75.4 ± 24.3% (P = 0.0023). No side-effects were observed. All patients exhibited clinical improvement after undergoing double-filtration plasmapheresis, and the prednisolone dose was reduced by 41 ± 8.9 mg (P = 0.0005) approximately 3 months after double-filtration plasmapheresis. To our knowledge, this is the first report evaluating the efficacy of double-filtration plasmapheresis with pemphigus disease area index, and it demonstrated that double-filtration plasmapheresis is a safe "subtracting" treatment for patients with drug-resistant pemphigus.

Monopathogenic vs multipathogenic explanations of pemphigus pathophysiology.

This viewpoint highlights major, partly controversial concepts about the pathogenesis of pemphigus. The monopathogenic theory explains intra-epidermal blistering through the "desmoglein (Dsg) compensation" hypothesis, according to which an antibody-dependent disabling of Dsg 1- and/or Dsg 3-mediated cell-cell attachments of keratinocytes (KCs) is sufficient to disrupt epidermal integrity and cause blistering. The multipathogenic theory explains intra-epidermal blistering through the "multiple hit" hypothesis stating that a simultaneous and synchronized inactivation of the physiological mechanisms regulating and/or mediating intercellular adhesion of KCs is necessary to disrupt epidermal integrity. The major premise for a multipathogenic theory is that a single type of autoantibody induces only reversible changes, so that affected KCs can recover due to a self-repair. The damage, however, becomes irreversible when the salvage pathway and/or other cell functions are altered by a partnering autoantibody and/or other pathogenic factors. Future studies are needed to (i) corroborate these findings, (ii) characterize in detail patient populations with non-Dsg-specific autoantibodies, and (iii) determine the extent of the contribution of non-Dsg antibodies in disease pathophysiology.

Comparison of Serum Autoantibodies to Desmogleins I, III in Patients with Oral Lichen Planus and Healthy Controls.

BACKGROUND & OBJECTIVE: Lichen planus is a mucocutaneous disease which is relatively common and in 30-70% of patients, mucosal lesions can be seen and known as a precancerous lesion but its etiology is not completely understood. Desmogleins I and III are the main desmosomal transmembrane proteins. These proteins have been identified as the autoantigen of the autoimmune disease. The aim of this study was evaluation of serum autoantibodies against desmogleins Ι, ΙΙΙ in oral lichen planus . METHODS: We attempted to determine the etiology of this disease with evaluation of these serum factors. Thirty-five patients with oral lichen planus and 35 healthy controls were recruited and tested for serum autoantibodies against desmogleins Ι, ΙΙΙ and indirect immunofluorescence also performed. Data were analyzed by statistical-analytical methods (Independent sample t -test) with using the SPSS.15 software. RESULTS: Serum autoantibody against desmoglein Ι had no significant difference in the two groups ( P =0.31 ) but significant increase in serum autoantibody to desmoglein ΙΙΙ was found in patients with oral lichen planus ( P =0.00) . CONCLUSION: It seems that autoantibody against desmoglein III has a significant role in the pathogenesis of oral lichen planus.

Pénfigo vulgar oral: reporte de un caso clínico / Oral penphigus vulgaris: report of a clinical case

El pénfigo vulgar es el tipo más común de un grupo padecimientos crónicos autoinmunes identificados por la presencia de lesiones ampulosas situadas en las mucosas y piel. El pénfigo vulgar oral (PVO) se caracteriza por la presencia de ampollas localizadas en las encías, paladar blando, carrillos, pero cualquier sitio de la cavidad oral puede ser afectado. Estas lesiones se presentan primero en la cavidad oral y meses después en la piel, por lo que su diagnóstico temprano y oportuno es vital para el pronóstico. El propósito de este trabajo es presentar esta condición clínica en una persona adulta mayor.

Pemphigus vulgaris is the most common of a group of chronic autoim-mune conditions characterized by the presence of mucosal and dermal blisters. In the case of oral pemphigus vulgaris (OPV), these are typi-cally found on the gums, soft palate, and cheeks, though anywhere in the oral cavity can be affected. These lesions appear first in the oral cavity and then, months later, on the skin. Therefore, early diagnosis is crucial for prognosis. The aim of this paper is to present a case report of this condition in an older adul.

Low pathogenicity of anti-desmoglein 3 immunoglobulin G autoantibodies contributes to the atypical clinical phenotypes in pemphigus.

The clinical phenotypes of pemphigus can be explained by the desmoglein (Dsg) compensation theory. However, some atypical cases such as cutaneous pemphigus vulgaris (cPV), in which patients have anti-Dsg3 antibodies without oral erosions, do not conform to this theory. To explain the discrepancy between clinical phenotypes and anti-Dsg antibody profiles, the pathogenic strength of immunoglobulin (Ig)G autoantibodies against Dsg3 must be taken into consideration. We analyzed the epitopes and blister-inducing pathogenic strength of the sera from three patients having IgG against Dsg3 without oral erosions with domain-swapped recombinant proteins and dissociation assay using cultured normal human epidermal keratinocytes. The results showed that all sera contained IgG directed against the amino terminal EC1 domain of Dsg3, as is found in most PV sera. However, dissociation assays revealed that the pathogenic strength of the anti-Dsg3 antibodies in all three cases was extremely lower than that of typical PV cases with mucosal involvement. In conclusion, when anti-Dsg3 IgG antibodies are not sufficient to inhibit the expression of Dsg3 in the oral mucosa, but can inhibit the expression in the skin, skin blisters can result. Therefore, the pathogenicity of anti-Dsg3 antibodies should be regarded as a key factor contributing to the clinical phenotype in pemphigus patients with conflicting antibody profiles.

Expression of desmogleins 1-3 and their clinical impacts on human lung cancer.

AIMS: Desmogleins (DSGs) are components of the cell-cell connecting desmosomes. Desmosomal proteins have been found dysregulated in various cancers. Here we studied the role of DSGs in human lung cancer. METHODS: Expression of DSG1-3 mRNA in lung cancer cell lines and human bronchial epithelial cells (HBEC) was examined by real time RT-PCR. Methylation status of DSG1-2 was evaluated by demethylation test and bisulfite sequencing (BS). Moreover, DSG1-3 protein expression was analysed in 112 primary lung tumor samples by immunohistochemistry (IHC) on tissue microarrays. RESULTS: It turned out that DSG1-3 was downregulated in most of the lung cancer cell lines. Reexpression of DSG2 and DSG3 was found in several cancer cell lines after demethylation treatment with 5-aza-2'-deoxycytidine (DAC), a DNA methyltransferase inhibitor. Complete or partial methylation of DSG2 promoter region was detected in 5 out of 6 cancer cell lines by BS. In primary lung tumors, higher protein expression of DSG2 and DSG3 correlated to the diagnosis of squamous cell lung carcinoma (SCC) (P=0.009 and P<0.001, respectively), additionally, a lower expression of DSG3 was significantly linked to higher tumor grade (P=0.012). CONCLUSIONS: Our data suggest that downregulation of DSG2 and DSG3 could be partially explained by DNA methylation. DSG2 and DSG3 might be potential diagnostic markers for SCC, and DSG3 could be a potential differentiation marker for lung cancer.

Desmosomes and extradesmosomal adhesive signaling contacts in pemphigus.

Desmosomes are adhering junctions present in all cells of simple and complex epithelia. They are most abundant in cells of tissues subjected to extensive mechanical stress such as keratinocytes and cardiomyocytes. The core of desmosomes is built up of desmosomal cadherins, cadherin-type adhesion molecules that are tethered to intermediate filaments via adaptor proteins of the armadillo and the plakin family. In addition, desmosomal cadherins are present outside of desmosomes. Recent investigations indicate that these molecules are involved in adhesion-dependent and adhesion-independent signaling and thus have functions different from the adhesive properties of their counterparts within desmosomes. Impaired adhesion of desmosomal cadherins both within and outside of desmosomes is the cause of the blistering skin disease pemphigus. Autoantibodies interfere with the binding of desmosomal cadherins and alter intracellular signaling pathways, the latter of which is necessary for loss of cell adhesion. Among the plethora of signaling molecules reported, altered activities of p38MAPK, protein kinase C, and epidermal growth factor receptor (EGFR) are most relevant. This review highlights the recent data on signaling by desmosomal cadherins and the mechanisms involved in pemphigus skin blistering.