Desmosomal Adhesion Research Articles

Pemphigus vulgaris autoantibodies induce an ER stress response.

Desmosomes are intercellular junctions that mediate cell-cell adhesion and are essential for maintaining tissue integrity. Pemphigus vulgaris (PV) is an autoimmune epidermal blistering disease caused by autoantibodies (IgG) targeting desmoglein 3 (Dsg3), a desmosomal cadherin. PV autoantibodies cause desmosome disassembly and loss of cell-cell adhesion, but the molecular signaling pathways that regulate these processes are not fully understood. Using high-resolution time-lapse imaging of live keratinocytes, we found that ER tubules make frequent and persistent contacts with internalizing Dsg3 puncta in keratinocytes treated with PV patient IgG. Biochemical experiments demonstrated that PV IgG activated ER stress signaling pathways, including both IRE1⍺ and PERK pathways, in cultured keratinocytes. Further, ER stress transcripts were upregulated in PV patient skin. Pharmacological inhibition of ER stress protected against PV IgG-induced desmosome disruption and loss of keratinocyte cell-cell adhesion, suggesting that ER stress may be an important pathomechanism and therapeutically targetable pathway for PV treatment. These data support a model in which desmosome adhesion is integrated with ER function to serve as a cell adhesion stress sensor that is activated in blistering skin disease.

Adhesion of pancreatic tumor cell clusters by desmosomal molecules enhances early liver metastases formation

Desmosomes are intercellular adhesion complexes providing mechanical coupling and tissue integrity. Previously, a correlation of desmosomal molecule expression with invasion and metastasis formation in several tumor entities was described together with a relevance for circulating tumor cell cluster formation. Here, we investigated the contribution of the desmosomal core adhesion molecule desmoglein-2 (DSG2) to the initial steps of liver metastasis formation by pancreatic cancer cells using a novel ex vivo liver perfusion mouse model. We applied the pancreatic ductal adenocarcinoma cell line AsPC-1 with and without a knockout (KO) of DSG2 and generated mouse lines with a hepatocyte-specific KO of the known interacting partners of DSG2 (DSG2 and desmocollin-2). Liver perfusion with DSG2 KO AsPC-1 cells led to smaller circulating cell clusters and a reduced number of cells adhering to murine livers compared to control cells. While this was independent of the expression levels of desmosomal adhesion molecules in hepatocytes, we show that increased cluster size of cancer cells, which correlates with stronger cell–cell adhesion and expression of desmosomal molecules, is a major factor contributing to the early phase of metastatic spreading. In conclusion, impaired desmosomal adhesion results in reduced circulating cell cluster size, which is relevant for seeding and attachment of metastatic cells to the liver.

DPM1 modulates desmosomal adhesion and epidermal differentiation through SERPINB5.

Glycosylation is essential to facilitate cell-cell adhesion and differentiation. We determined the role of the dolichol phosphate mannosyltransferase (DPM) complex, a central regulator for glycosylation, for desmosomal adhesive function and epidermal differentiation. Deletion of the key molecule of the DPM complex, DPM1, in human keratinocytes resulted in weakened cell-cell adhesion, impaired localization of the desmosomal components desmoplakin and desmoglein-2, and led to cytoskeletal organization defects in human keratinocytes. In a 3D organotypic human epidermis model, loss of DPM1 caused impaired differentiation with abnormally increased cornification, reduced thickness of non-corneal layers, and formation of intercellular gaps in the epidermis. Using proteomic approaches, SERPINB5 was identified as a DPM1-dependent interaction partner of desmoplakin. Mechanistically, SERPINB5 reduced desmoplakin phosphorylation at serine 176, which was required for strong intercellular adhesion. These results uncover a novel role of the DPM complex in connecting desmosomal adhesion with epidermal differentiation.

Cardiac desmosomal adhesion relies on ideal-, slip- and catch bonds

The cardiac muscle consists of individual cardiomyocytes that are mechanically linked by desmosomes. Desmosomal adhesion is mediated by densely packed and organized cadherins which, in presence of Ca2+, stretch out their extracellular domains (EC) and dimerize with opposing binding partners by exchanging an N-terminal tryptophan. The strand-swap binding motif of cardiac cadherins like desmocollin 2 (Dsc2) (and desmoglein2 alike) is highly specific but of low affinity with average bond lifetimes in the range of approximately 0.3 s. Notably, despite this comparatively weak interaction, desmosomes mediate a stable, tensile-resistant bond. In addition, force mediated dissociation of strand-swap dimers exhibit a reduced bond lifetime as external forces increase (slip bond). Using atomic force microscopy based single molecule force spectroscopy (AFM-SMFS), we demonstrate that Dsc2 has two further binding modes that, in addition to strand-swap dimers, most likely play a significant role in the integrity of the cardiac muscle. At short interaction times, the Dsc2 monomers associate only loosely, as can be seen from short-lived force-independent bonds. These ideal bonds are a precursor state and probably stabilize the formation of the self-inhibiting strand-swap dimer. The addition of tryptophan in the measurement buffer acts as a competitive inhibitor, preventing the N-terminal strand exchange. Here, Dsc2 dimerizes as X-dimer which clearly shows a tri-phasic slip-catch-slip type of dissociation. Within the force-mediated transition (catch) regime, Dsc2 dimers switch between a rather brittle low force and a strengthened high force adhesion state. As a result, we can assume that desmosomal adhesion is mediated not only by strand-swap dimers (slip) but also by their precursor states (ideal bond) and force-activated X-dimers (catch bond).

Binding to the neonatal Fc receptor enhances the pathogenicity of anti-desmoglein-3 antibodies in keratinocytes.

The neonatal Fc receptor (FcRn) is important for numerous cellular processes that involve antibody recycling and trafficking. A major function of FcRn is IgG recycling and half-life prolongation, and FcRn blockade results in a reduction of autoantibodies in IgG-mediated autoimmune diseases. In epithelial cells, FcRn functions in processes different from IgG recycling, such as antibody transcytosis in intestinal cells. In pemphigus vulgaris, an autoimmune disease of the epidermis, IgG autoantibodies directed against desmosomal adhesion proteins, especially desmoglein-3 and -1, cause loss of keratinocyte adhesion. We have previously demonstrated that FcRn blockade with efgartigimod, a human Fc fragment with enhanced FcRn binding, significantly reduces the keratinocyte monolayer fragmentation caused by anti-desmoglein-3 antibodies. This points to a direct function of FcRn in keratinocytes, beyond IgG recycling, but the mechanisms have not yet been elucidated in detail. Here, we show that FcRn binding is required for the full pathogenicity of recombinant anti-desmoglein-3 antibodies in keratinocytes, and that antibodies that exhibit enhanced or reduced FcRn affinity due to targeted substitutions in their Fc region, as well as F(ab')2 fragments not binding to FcRn display different degrees of pathogenicity. Blockade of FcRn by efgartigimod only shows a protective effect on keratinocyte adhesion against antibodies capable of binding to FcRn. Furthermore, antibody-induced degradation of desmoglein-3 in keratinocytes does not depend on FcRn, demonstrating that desmoglein-3 degradation and acantholysis are functionally disconnected processes. Our data suggest that the role of FcRn in autoimmune diseases is likely to be versatile and cell-type dependent, thus stressing the importance of further studies on FcRn function in autoimmune diseases.

Downregulation of γ-Catenin by miR-195-5p Inhibits Colon Cancer Progression, Regulating Desmosome Function.

Desmosomes are essential structures for ensuring tissue functions, and their deregulation is involved in the development of colorectal cancer (CRC). JUP (γ-catenin) is a desmosome adhesion component that also acts as a signaling hub, suggesting its potential involvement in CRC progression. In this context, we recently demonstrated that miR-195-5p regulated JUP and desmosome cadherins expression. In addition, miR-195-5p gain of function indirectly modulated the expression of key effectors of the Wnt pathway involved in JUP-dependent signaling. Here, our purpose was to demonstrate the aberrant expression of miR-195-5p and JUP in CRC patients and to functionally characterize the role of miR-195-5p in the regulation of desmosome function. First, we showed that miR-195-5p was downregulated in CRC tumors compared to adjacent normal tissue. Then, we demonstrated that JUP expression was significantly increased in CRC tissues compared to adjacent normal tissues. The effects of miR-195-5p on CRC progression were assessed using in vitro transient transfection experiments and in vivo miRNA administration. Increased miR-195-5p in colonic epithelial cells strongly inhibits cell proliferation, viability, and invasion via JUP. In vivo gain of function of miR-195-5p reduced the numbers and sizes of tumors and significantly ameliorated the histopathological changes typical of CRC. In conclusion, our findings indicate a potential pharmacological target based on miR-195-5p replacement as a new therapeutic approach in CRC.

Use of IgG4 Immunohistochemistry as a Diagnostic Tool for Pemphigus

Pemphigus belongs to the group of antibody mediated autoimmune vesiculobullous disease (AIBD) of skin and mucous membranes. Antibodies are directed against the desmosomal adhesion proteins and IgG4 is the predominant subclass. It is a rare disease associated with significant mortality and morbidity. DIF is the gold standard test for AIBD. It requires fresh frozen section which is a major technical issue in most centres. The aim of this research was to study the diagnostic accuracy of IgG4 immunohistochemistry in pemphigus. The study was conducted as a diagnostic test evaluation in a tertiary care hospital. Paraffin blocks of histopathologically diagnosed AIBD were used for doing immunohistochemistry. The findings were compared with DIF findings. Statistical analysis was performed using SPSS, version 20.0. 48 paraffin blocks of AIBD were selected, DIF of all cases were already done from outside centre. There were 21 cases of pemphigus, 25 cases of bullous pemphigoid and one case each of epidermolysis bullosa acquisita and dermatitis herpetiformis. The sensitivity of IgG4 IHC was found to be 85.7%, specificity 96.3%, positive predictive value of 94.7% and negative predictive value 89.7%. So, we conclude that IgG4 IHC done on paraffin sections can be used as a diagnostic tool for pemphigus.

Abstract P2169: Identification Of Pro-adhesive Drugs By A Novel High-throughput Approach

Defective cell-cell adhesion contributes to the patho-mechanism of various diseases. In line with this, a mouse model recently developed by our group demonstrate that loss of cell-cell adhesion is an important initial step leading to Arrhythmogenic Cardiomyopathy (ACM), a disease which presents with severe arrhythmia, ventricular fibrosis and impaired cardiac function. Derived from the central role of defective cell-cell adhesion for the patho-mechanism, we here aim to identify new compounds, which restore intercellular adhesion and could serve as potential therapeutics. To screen a high number of agents, we developed an adhesion-based high-throughput approach by adapting a standard cell-cell dissociation assay to 96-well plate format including establishment of an automated acquisition and analysis pipeline. To model loss of intercellular adhesion, cells deficient for the desmosomal adhesion molecule desmoglein-2 were used. After establishing settings to sensitively detect changes in cell-cell adhesion, this method was applied to screen a library of 1946 FDA-approved drugs in three concentrations. Several new compounds strengthening intercellular adhesion were identified in addition to known pro-adhesive drugs, confirming the robustness of our assay. The increased adhesiveness of selected top hits was confirmed in cells expressing ACM patient mutations. In conclusion, we here developed an adhesion-based high-throughput approach capable of identifying adhesion modulators which have the potential to be used as therapeutics for diseases with defective desmosomal adhesion such as ACM.

Abstract GS.12: A New Mouse Model To Investigate The Early Steps Of Arrhythmogenic Cardiomyopathy

Arrhythmogenic Cardiomyopathy (ACM) is characterized by progressive loss of cardiomyocytes with fibrosis, systolic dysfunction and life-threatening arrhythmias. Mutations in genes of the desmosomal adhesion complex such as desmoglein-2 (Dsg2) are the major cause, but the underlying mechanisms leading to the disease are not well understood. Accordingly, only symptomatic treatment is available. Here, we establish an inducible Dsg2-W2A knock-in mouse model with temporal control of disease onset as new approach to analyse the early processes underlying the ACM phenotype. We have previously characterized a constitutive Dsg2-W2A knock-in model which develops a cardiac phenotype bearing all major criteria of ACM directly after birth. To control the onset of disease, we now generated a mouse line bearing the Dsg2-W2A mutation and a loxP -flanked Dsg2 on separate alleles, leading to functional hemizygosity of the Dsg2-W2A mutation upon tamoxifen-induced Cre expression. Detailed characterization of this iDsg2-W2A model revealed early repolarization changes in ECG recordings starting directly after induction and progression to extensive impairment of electrical conduction over 10 weeks. These changes were paralleled with the appearance of ventricular and supraventricular arrhythmias. Starting two weeks after induction, reduced cardiac output function of the right and later of the left ventricle was detectable via echocardiography. Finally, these mice developed structural changes with loss of cardiomyocytes and ventricular fibrosis similar to ACM patients. This study gives detailed insight on the early steps of ACM showing a sequence from changes in conduction, occurrence of arrhythmia to functional impairment, starting in the right and progressing to the left ventricle, together with structural changes of the heart. We expect this model to be valuable to discern patho-mechanisms in detail and to identify and test novel treatment options for ACM.

Catalytic antibodies in arrhythmogenic cardiomyopathy patients cleave desmoglein 2 and N-cadherin and impair cardiomyocyte cohesion

AimsArrhythmogenic cardiomyopathy (AC) is a severe heart disease predisposing to ventricular arrhythmias and sudden cardiac death caused by mutations affecting intercalated disc (ICD) proteins and aggravated by physical exercise. Recently, autoantibodies targeting ICD proteins, including the desmosomal cadherin desmoglein 2 (DSG2), were reported in AC patients and were considered relevant for disease development and progression, particularly in patients without underlying pathogenic mutations. However, it is unclear at present whether these autoantibodies are pathogenic and by which mechanisms show specificity for DSG2 and thus can be used as a diagnostic tool.Methods and ResultsIgG fractions were purified from 15 AC patients and 4 healthy controls. Immunostainings dissociation assays, atomic force microscopy (AFM), Western blot analysis and Triton X-100 assays were performed utilizing human heart left ventricle tissue, HL-1 cells and murine cardiac slices. Immunostainings revealed that autoantibodies against ICD proteins are prevalent in AC and most autoantibody fractions have catalytic properties and cleave the ICD adhesion molecules DSG2 and N-cadherin, thereby reducing cadherin interactions as revealed by AFM. Furthermore, most of the AC-IgG fractions causing loss of cardiomyocyte cohesion activated p38MAPK, which is known to contribute to a loss of desmosomal adhesion in different cell types, including cardiomyocytes. In addition, p38MAPK inhibition rescued the loss of cardiomyocyte cohesion induced by AC-IgGs.ConclusionOur study demonstrates that catalytic autoantibodies play a pathogenic role by cleaving ICD cadherins and thereby reducing cardiomyocyte cohesion by a mechanism involving p38MAPK activation. Finally, we conclude that DSG2 cleavage by autoantibodies could be used as a diagnostic tool for AC.

Retromer Chaperones: Potential Therapeutics for Treatment of Skin Disease?

Retromer Chaperones: Potential Therapeutics for Treatment of Skin Disease?

Unraveling Mechanisms of Autoimmune Skin Blistering: Applying Single-Cell Transcriptomics to Pemphigus B Cells

Unraveling Mechanisms of Autoimmune Skin Blistering: Applying Single-Cell Transcriptomics to Pemphigus B Cells

The Importance of Patient-Focused Drug Development in Pemphigus and Pemphigoid

The Importance of Patient-Focused Drug Development in Pemphigus and Pemphigoid

Mouse models of pemphigus: valuable tools to investigate pathomechanisms and novel therapeutic interventions.

Autoimmune blistering diseases (AIBD) are paradigms of autoantibody-mediated organ-specific autoimmune disorders that involve skin and/or mucous membranes. Compared to other autoimmune diseases, the pathogenicity of autoantibodies in AIBD is relatively well described. Pemphigus is a potentially lethal autoantibody driven autoimmune disorder with a strong HLA class II association. It is mainly characterized by IgG against the desmosomal adhesion molecules desmoglein 3 (Dsg3) and Dsg1. Several murine pemphigus models were developed subsequently, each allowing the analysis of a characteristic feature, such as pathogenic IgG or Dsg3-specific T or B cells. Thus, the models can be employed to preclinically evaluate potentially novel therapies. We here thoroughly summarize past and recent efforts in developing and utilizing pemphigus mouse models for pathomechanistic investigation and therapeutic interventions.

1422 Uncoupling desmosomal cadherin adhesion activates quiescent hair follicle stem cells and orchestrates self-organized regeneration through outside-in signaling

1422 Uncoupling desmosomal cadherin adhesion activates quiescent hair follicle stem cells and orchestrates self-organized regeneration through outside-in signaling

Abstract 881: Desmocollin-3 and tumor immune microenvironment: Bioinformatics evaluation

Abstract Desmocollin-3 (DSC3) is a desmosomal adhesion molecule responsible for integrity and cell adhesion under normal physiological condition. Its expression is altered during carcinogenesis. DSC3 is a p53 responsive gene. Like other adhesion molecules, it is described to provide barrier for immune infiltration of tumor. To identify a specific immune gene signature related to DSC3, spearman correlation coefficient was determined for 207 immune related genes using Cbioportal in cancer having high and low level of DSC3 gene expression .We classified renal adenocarcinoma lung, hepatocellular carcinoma and renal cancer as DSC3low and squamous lung cancer, cervical cancer and head and Neck cancer as DSC3high based on DSC3 gene expression level. In DSC3high group, six genes were found to be correlated (Spearman correlation ≥ 0.3) with DSC3 expression (Table), while none of the 207 immune related genes were correlated with DSC3low expression. Of genes with positive correlation, CD44 is a marker for stem cell and is associated with resistance to chemotherapy while S100A12 and TOLLIP are associated with carcinogenesis and inflammation. Of immune genes with negative correlation, GATA6 is a tumor suppressive gene, IL-12A is responsible for T-cell-independent induction of IFNγ and CD63 is associated with survival as described in lung cancer. This findings suggests DSC3high expression may be associated with poor prognosis compared DSC3low . DSC3 expression is specific for squamous lung cancer and is used to differentiate it from adenocarcinoma lung. Squamous lung cancer is also known to have poor prognosis compared to adenocarcinoma of lung. We will be presenting full details about 207 selected genes and their correlation with DSC3 in our presentation. Table: Spearman’s correlation of DSC3 with Immune genes DSC3 expression Immune genes with positive spearman’s correlation Immune genes with negative spearman’s correlation Cancer Median RSEM (N) CD44 S100A12 TOLLIP CD63 GATA6 IL12A LUSC 6208 (n=501) 0.4 0.3 0.4 -0.4 -0.3 -0.3 CESC 10086 (n=306) 0.6 0.6 0.6 -0.6 -0.4 -0.4 HNSC 15287(n=522) 0.3 0.3 0.3 -0.5 -0.3 -0.4 KIPAN 1.5 (n=720) < 0.3 < 0.3 < 0.3 < 0.3 < 0.3 < 0.3 LIHC 2.0 (n=231) < 0.3 < 0.3 < 0.3 < 0.3 < 0.3 < 0.3 LUAD 10 (n=496) < 0.3 < 0.3 < 0.3 < 0.3 < 0.3 < 0.3 Citation Format: Arpit Dheeraj, Bakulesh M. Khamar, Chandreshwar P. Shukla, Nayan K. Jain, Rajiv I. Modi. Desmocollin-3 and tumor immune microenvironment: Bioinformatics evaluation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 881.

Heterozygous ATP2A2 missense variant identified in a Shih Tzu with Darier disease.

Darier disease is caused by heterozygous loss of function variants in the ATP2A2 gene encoding the endoplasmic/sarcoplasmic reticulum Ca2+ pump ATP2A2. Defective intracellular calcium signaling in the epidermis results in a loss of desmosomal adhesion and the development of characteristic skin lesions. In this study, we investigated a Shih Tzu that developed erythematous papules on the ventrum and, over time, the dorsal neck and a nodule in the right ear canal with secondary ear infection. Histopathologic examination demonstrated discrete foci of acantholysis affecting suprabasal layers of the epidermis. Whole genome sequencing of the affected dog identified a heterozygous missense variant, p.N809H, affecting an evolutionarily conserved amino acid residue of the ATP2A2 protein. The highly characteristic clinical and histopathologic findings together with a plausible variant in the only known functional candidate gene establish the diagnosis of canine Darier disease in the studied dog and highlight the potential of genetic analyses as complementary diagnostic approach in veterinary medicine.

Cardiomyocyte cohesion is increased after ADAM17 inhibition.

A Disintegrin And Metalloprotease (ADAM) family proteins are involved in several cardiac diseases, and some ADAMs have been associated with cardiomyopathies. ADAM17 is known to cleave desmoglein 2 (DSG2), one of the proteins involved in the pathogenesis of arrhythmogenic cardiomyopathy (AC). Desmosomal stability is impaired in AC, an inheritable genetic disease, the underlying causes of which can be mutations in genes coding for proteins of the desmosome, such as DSG2, desmoplakin (DP), plakoglobin (PG), plakophilin 2 or desmocollin 2. Stabilizing desmosomal contacts can therefore be a treatment option. In the heart of the murine Jup -/- AC model, (Jup being the gene coding for PG) mice, elevated levels of p38MAPK, an activator of ADAM17, were found. However, ADAM17 levels were unaltered in Jup -/- mice hearts. Nonetheless, inhibition of ADAM17 led to enhanced cardiomyocyte cohesion in both Jup +/+ and Jup -/- mice, and in HL-1 cardiomyocytes. Further, enhanced cohesion in HL-1 cardiomyocytes after acute inhibition of ADAM17 was paralleled by enhanced localization of DSG2 and DP at the membrane, whereas no changes in desmosomal assembly or the desmosomal complex were observed. In conclusion, acute inhibition of ADAM17 might lead to reduced cleavage of DSG2, thereby stabilizing the desmosomal adhesion, evidenced by increased DSG2 and DP localization at cell borders and eventually cardiomyocyte cohesion. We believe that similar mechanisms exist in AC.

Apremilast prevents blistering in human epidermis and stabilizes keratinocyte adhesion in pemphigus

Pemphigus vulgaris is a life-threatening blistering skin disease caused by autoantibodies destabilizing desmosomal adhesion. Current therapies focus on suppression of autoantibody formation and thus treatments directly stabilizing keratinocyte adhesion would fulfill an unmet medical need. We here demonstrate that apremilast, a phosphodiesterase 4 inhibitor used in psoriasis, prevents skin blistering in pemphigus vulgaris. Apremilast abrogates pemphigus autoantibody-induced loss of keratinocyte cohesion in ex-vivo human epidermis, cultured keratinocytes in vitro and in vivo in mice. In parallel, apremilast inhibits keratin retraction as well as desmosome splitting, induces phosphorylation of plakoglobin at serine 665 and desmoplakin assembly into desmosomal plaques. We established a plakoglobin phospho-deficient mouse model that reveals fragile epidermis with altered organization of keratin filaments and desmosomal cadherins. In keratinocytes derived from these mice, intercellular adhesion is impaired and not rescued by apremilast. These data identify an unreported mechanism of desmosome regulation and propose that apremilast stabilizes keratinocyte adhesion and is protective in pemphigus.

043 A novel tool to analyse the pathogenic impact of IgG binding to extracellular domain 5 of Desmoglein 3

Pemphigus vulgaris (PV) is a severe autoimmune blistering disease characterized by autoantibodies (auto-ab) against the desmosomal adhesion molecules desmoglein3 (Dsg3) and Dsg1. Binding of Dsg specific auto-ab to target structures induces an interruption of the desmosomal integrity which ultimately results in the clinical manifestation of flaccid blisters and erosions in PV patients. Underlying mechanisms inducing blister formation upon binding of Dsg-specific auto-ab are largely unknown. Numerous studies demonstrated the pathogenicity of auto-ab specific for the amino-terminal region (extracellular domain 1, EC1) of Dsg3.