Desmoglein 2 and desmocollin 2 depletions promote malignancy through distinct mechanisms in triple-negative and luminal breast cancer.

BACKGROUND: Aberrant expressions of desmoglein 2 (Dsg2) and desmocollin 2(Dsc2), the two most widely distributed desmosomal cadherins, have been found to play various roles in cancer in a context-dependent manner. Their specific roles on breast cancer (BC) and the potential mechanisms remain unclear. METHODS: The expressions of Dsg2 and Dsc2 in human BC tissues and cell lines were assessed by using bioinformatics analysis, immunohistochemistry and western blotting assays. Wound-healing and Transwell assays were performed to evaluate the cells' migration and invasion abilities. Plate colony-forming and MTT assays were used to examine the cells' capacity of proliferation. Mechanically, Dsg2 and Dsc2 knockdown-induced malignant behaviors were elucidated using western blotting assay as well as three inhibitors including MK2206 for AKT, PD98059 for ERK, and XAV-939 for ß-catenin. RESULTS: We found reduced expressions of Dsg2 and Dsc2 in human BC tissues and cell lines compared to normal counterparts. Furthermore, shRNA-mediated downregulation of Dsg2 and Dsc2 could significantly enhance cell proliferation, migration and invasion in triple-negative MDA-MB-231 and luminal MCF-7 BC cells. Mechanistically, EGFR activity was decreased but downstream AKT and ERK pathways were both activated maybe through other activated protein tyrosine kinases in shDsg2 and shDsc2 MDA-MB-231 cells since protein tyrosine kinases are key drivers of triple-negative BC survival. Additionally, AKT inhibitor treatment displayed much stronger capacity to abolish shDsg2 and shDsc2 induced progression compared to ERK inhibition, which was due to feedback activation of AKT pathway induced by ERK inhibition. In contrast, all of EGFR, AKT and ERK activities were attenuated, whereas ß-catenin was accumulated in shDsg2 and shDsc2 MCF-7 cells. These results indicate that EGFR-targeted therapy is not a good choice for BC patients with low Dsg2 or Dsc2 expression. Comparatively, AKT inhibitors may be more helpful to triple-negative BC patients with low Dsg2 or Dsc2 expression, while therapies targeting ß-catenin can be considered for luminal BC patients with low Dsg2 or Dsc2 expression. CONCLUSION: Our finding demonstrate that single knockdown of Dsg2 or Dsc2 could promote proliferation, motility and invasion in triple-negative MDA-MB-231 and luminal MCF-7 cells. Nevertheless, the underlying mechanisms were cellular context-specific and distinct.

Hemi- and Homozygous Loss-of-Function Mutations in DSG2 (Desmoglein-2) Cause Recessive Arrhythmogenic Cardiomyopathy with an Early Onset.

About 50% of patients with arrhythmogenic cardiomyopathy (ACM) carry a pathogenic or likely pathogenic mutation in the desmosomal genes. However, there is a significant number of patients without positive familial anamnesis. Therefore, the molecular reasons for ACM in these patients are frequently unknown and a genetic contribution might be underestimated. Here, we used a next-generation sequencing (NGS) approach and in addition single nucleotide polymor-phism (SNP) arrays for the genetic analysis of two independent index patients without familial medical history. Of note, this genetic strategy revealed a homozygous splice site mutation (DSG2-c.378+1G>T) in the first patient and a nonsense mutation (DSG2-p.L772X) in combination with a large deletion in DSG2 in the second one. In conclusion, a recessive inheritance pattern is likely for both cases, which might contribute to the hidden medical history in both families. This is the first report about these novel loss-of-function mutations in DSG2 that have not been previously identi-fied. Therefore, we suggest performing deep genetic analyses using NGS in combination with SNP arrays also for ACM index patients without obvious familial medical history. In the future, this finding might has relevance for the genetic counseling of similar cases.

A homozygous DSC2 deletion associated with arrhythmogenic cardiomyopathy is caused by uniparental isodisomy.

AIMS: We aimed to unravel the genetic, molecular and cellular pathomechanisms of DSC2 truncation variants leading to arrhythmogenic cardiomyopathy (ACM). METHODS AND RESULTS: We report a homozygous 4-bp DSC2 deletion variant c.1913_1916delAGAA, p.Q638LfsX647hom causing a frameshift carried by an ACM patient. Whole exome sequencing and comparative genomic hybridization analysis support a loss of heterozygosity in a large segment of chromosome 18 indicating segmental interstitial uniparental isodisomy (UPD). Ultrastructural analysis of the explanted myocardium from a mutation carrier using transmission electron microscopy revealed a partially widening of the intercalated disc. Using qRT-PCR we demonstrated that DSC2 mRNA expression was substantially decreased in the explanted myocardial tissue of the homozygous carrier compared to controls. Western blot analysis revealed absence of both full-length desmocollin-2 isoforms. Only a weak expression of the truncated form of desmocollin-2 was detectable. Immunohistochemistry showed that the truncated form of desmocollin-2 did not localize at the intercalated discs. In vitro, transfection experiments using induced pluripotent stem cell derived cardiomyocytes and HT-1080 cells demonstrated an obvious absence of the mutant truncated desmocollin-2 at the plasma membrane. Immunoprecipitation in combination with fluorescence measurements and Western blot analyses revealed an abnormal secretion of the truncated desmocollin-2. CONCLUSION: In summary, we unraveled segmental UPD as the likely genetic reason for a small homozygous DSC2 deletion. We conclude that a combination of nonsense mediated mRNA decay and extracellular secretion is involved in DSC2 related ACM.

Plakophilin3 increases desmosome assembly, size and stability by increasing expression of desmocollin2.

Previous reports show that the desmosomal plaque protein plakophilin3 (PKP3) is essential for desmosome formation. Here, we report that PKP3 over-expression decreases calcium dependency for de novo desmosome formation and makes existing cell-cell adhesion junctions more resilient in low calcium medium due to an increase in desmocollin2 expression. PKP3 overexpression increases the stability of other desmosomal proteins independently of the increase in DSC2 levels and regulates desmosome formation and stability by a multimodal mechanism affecting transcription, protein stability and cell border localization of desmosomal proteins.

Cardiomyopathy related desmocollin-2 prodomain variants affect the intracellular cadherin transport and processing.

Background: Arrhythmogenic cardiomyopathy can be caused by genetic variants in desmosomal cadherins. Since cardiac desmosomal cadherins are crucial for cell-cell-adhesion, their correct localization at the plasma membrane is essential. Methods: Nine desmocollin-2 variants at five positions from various public genetic databases (p.D30N, p.V52A/I, p.G77V/D/S, p.V79G, p.I96V/T) and three additional conserved positions (p.C32, p.C57, p.F71) within the prodomain were investigated in vitro using confocal microscopy. Model variants (p.C32A/S, p.V52G/L, p.C57A/S, p.F71Y/A/S, p.V79A/I/L, p.I96l/A) were generated to investigate the impact of specific amino acids. Results: We revealed that all analyzed positions in the prodomain are critical for the intracellular transport. However, the variants p.D30N, p.V52A/I and p.I96V listed in genetic databases do not disturb the intracellular transport revealing that the loss of these canonical sequences may be compensated. Conclusion: As disease-related homozygous truncating desmocollin-2 variants lacking the transmembrane domain are not localized at the plasma membrane, we predict that some of the investigated prodomain variants may be relevant in the context of arrhythmogenic cardiomyopathy due to disturbed intracellular transport.

Syncope in the athlete - Minor changes, major diagnosis!

We report the case of a 17-year-old athlete who resorted to the emergency department for palpitations and dizziness while exercising. He mentioned two exercise-associated episodes of syncope in the last six months. He was tachycardic and hypotensive. The electrocardiogram showed regular wide complex tachycardia, left bundle branch block morphology with superior axis restored to sinus rhythm after electrical cardioversion. In sinus rhythm, it showed T-wave inversion in V1-V5. Transthoracic echocardiography revealed mild dilation and dysfunction of the right ventricle (RV) with global hypocontractility. Cardiac magnetic resonance (CMR) revealed a RV end diastolic volume indexed to body surface area of 180 ml/m2, global hypokinesia and RV dyssynchrony, subepicardial late enhancement in the distal septum and in the middle segment of the inferoseptal wall. The patient underwent a genetic study which showed a mutation in the gene that encodes the desmocolin-2 protein (DSC-2), which is involved in the pathogenesis of arrhythmogenic right ventricular cardiomyopathy (ARVC). According to the modified Task Force Criteria for this diagnosis, the patient presented four major criteria for ARVC. Thus, a subcutaneous cardioverter was implanted, and the patient was followed up at the cardiology department. Arrhythmogenic right ventricular cardiomyopathy diagnosis is based on structural, functional, electrophysiological and genetic criteria reflecting underlying histological changes. This case depicts the essential characteristics for disease recognition.

DSC2 suppresses the growth of gastric cancer through the inhibition of nuclear translocation of γ-catenin and PTEN/PI3K/AKT signaling pathway.

BACKGROUND: Globally, gastric cancer (GC) is still a major leading cause of cancer-associated deaths. Downregulated desmocollin2 (DSC2) is considered to be closely related to tumor progression. However, the underlying mechanisms of DSC2 in GC progression require further exploration. METHOD: We initially constructed different GC cells based on DSC2 contents, established the mouse tumor xenografts, and subsequently performed clonal formation, MTT, Caspase-3 activity, and sperm DNA fragmentation assays to detect the functions of DSC2 in GC growth. Subsequently, we performed western blot, Co-IP, and immunofluorescence assays to investigate the underlying mechanisms through pretreatment with PI3K inhibitor, LY294002, and its activator, recombinant human insulin-like growth factor I (IGF1). RESULT: DSC2 could significantly inhibit the viability of GC cells at both in vitro and in vivo levels. The underlying mechanism may be that DSC2 binds the γ-catenin to decrease its nuclear level, thereby downregulating the anti-apoptotic factor BCL-2 expression and upregulating the pro-apoptotic factor P53 expression, which adjusts the PTEN/PI3K/AKT signaling pathway to promote the cancer cell apoptosis. CONCLUSIONS: Our finding suggests that DSC2 might be a potential therapeutic target for the treatment of cancers, most especially GC.

Desmocollin-2 inhibits cell proliferation and promotes apoptosis in hepatocellular carcinoma via the ERK/c-MYC signaling pathway.

Hepatocellular carcinoma (HCC) is one of the most common cancers around the world with a poor prognosis. The main reason for poor prognosis is early stage HCC is inconspicuous so it is difficult to detect and effective treatment strategies are lacking for advanced HCC. In this context, novel molecular targets are urgently needed for the diagnosis and therapy of HCC. In this study, we investigated the expression level, biological function, and relative mechanism of Desmocollin-2(DSC2) in HCC. DSC2 expression levels were decreased significantly in HCC cell lines SMMC-7721(7721), Huh7, HCC-LM3(LM3), and MHCC-97H(97H), especially in LM3 cells, compared with human liver cell line L02(L02). DSC2 overexpression in LM3 cells could inhibit the proliferation (in vitro and in vivo), colony formation, migration, and invasion abilities of HCC cells, and promote cell apoptosis, while DSC2 inhibition in 7721 cells performed the opposite effect. Consistent with these results, regulating DSC2 expression in 7721 and LM3 cells could affect the expression levels of apoptosis-related proteins (Bax, Bcl-2, c-Caspase-3, Caspase-3, Caspase-8, and Survivin) and cell cycle-related proteins (Cyclin D1, Cyclin B1, CDK1, and CDK2). Furthermore, DSC2 expression was significantly negatively correlated with the levels of p-ERK and c-MYC in both LM3 and 7721 cell lines. These findings confirmed that DSC2 overexpression could inhibit the proliferation, migration, and invasion abilities while promoting apoptosis of HCC cells via the ERK/c-MYC signaling pathway. In a conclusion, DSC2 was a tumor suppressor with low expression in liver cancer.

Efficient reprogramming of human fibroblasts using RNA reprogramming with DAPT and iDOT1L under normoxia conditions.

Introduction: Human induced pluripotent stem cells (hiPSCs) are generated through the reprogramming of somatic cells expressing a defined set of transcription factors. The advent of autologous iPSCs has enabled the generation of patient-specific iPSC lines and is expected to contribute to the exploration of cures and causes of diseases, drug screening, and tailor-made regenerative medicines. Efficient control of hiPSC derivation is beneficial for industrial applications. However, the mechanisms underlying somatic cell reprogramming remain unknown, while reprogramming efficiency remains extremely low, especially in human cells. Methods and results: We previously reported that chemical inhibition of the NOTCH signaling pathway and DOT1L promoted the generation of hiPSCs from keratinocytes, but the mechanisms and effect of this double inhibition on other types of cells remain to be investigated. Here, we found that the NOTCH/DOT1L inhibition markedly increased iPSC colony generation from human fibroblast cells via mRNA reprogramming, and mesenchymal to epithelial transition (MET)-related genes are significantly expressed in the early phase of the reprogramming. We successfully derived hiPSC lines using a single-cell sorting system under efficient reprogramming conditions. Conclusions: This user-friendly reprogramming approach paves the way for the development of hiPSC derivations in industrial applications of disease modeling and drug screening.

Androgen downregulates desmocollin-2 in association with induction of mesenchymal transition of breast MDA-MB-453 cancer cells.

Desmosomes are cellular structures that are critical in cell-cell adhesion and in maintaining tissue architecture. Changes in the expression of desmocollin-2 (DSC2) have been noted during tumor progression into an invasive phenotype and as cells undergo epithelial-mesenchymal transition. We have previously reported that breast MDA-MB-453 cancer cells, a luminal androgen receptor (AR) model of triple-negative breast cancer, acquire mesenchymal features when treated with the AR agonist, dihydrotestosterone (DHT). We have therefore investigated androgen regulation of the expression and cellular localization of DSC2 in MDA-MB-453 cells. Treatment of the cells with DHT resulted in a dose-dependent reduction in DSC2 protein levels and dispersion of its membrane localization concomitant with AR- and ß-catenin-mediated mesenchymal transition of cells. A significant correlation was revealed between decreased expression of AR and increased expression of DSC2 in patient samples. In addition, whereas lower expression of AR was associated with a reduced overall and recurrence-free survival of breast cancer patients, higher expression of DSC2 was found in invasive breast tumors than in normal breast cells and was correlated with lower patient survival. Upon knocking down DSC2, the cells became elongated, mesenchymal-like, and slightly, but insignificantly, more migratory. The addition of DHT further stimulated cell elongation and migration. DSC2 siRNA-transfected cells reverted to a normal epithelial morphology upon inhibition of ß-catenin. These results highlight the role of DSC2 in maintaining the epithelial morphology of MDA-MB-453 cells and the negative regulation of the desmosomal protein by DHT during stimulation of the androgen-induced, ß-catenin-mediated mesenchymal transition of the cells.

sRNA23392 packaged by Porphyromonas gingivalis outer membrane vesicles promotes oral squamous cell carcinomas migration and invasion by targeting desmocollin-2.

Oral squamous cell carcinoma (OSCC) is the most common head and neck malignant tumor. Periodontitis, a common chronic inflammatory disease, has been proven to increase the risk of oral cancers. Porphyromonas gingivalis (P. gingivalis), the major pathogen in periodontal disease, was recently shown to promote the development of OSCC. However, the underlying mechanisms have not been defined. Emerging evidence suggests that P. gingivalis outer membrane vesicles (OMVs) contain different packaged small RNAs (sRNAs) with the potential to target host mRNA function and/or stability. In this study, we found that P. gingivalis OMVs promote the invasion and migration of OSCC cells in vitro. Further research showed that sRNA23392 was abundant in P. gingivalis OMVs and it promoted the invasion and migration of OSCC cells by targeting desmocollin-2 (DSC2). DSC2, a desmosomal cadherin family member, has been found to be involved in tumor progression. sRNA23392 inhibitors attenuated P. gingivalis OMV-induced migration and invasion of OSCC cells. Collectively, these findings are consistent with the hypothesis that sRNA23392 in P. gingivalis OMVs is a novel mechanism of the host-pathogen interaction, whereby P. gingivalis promotes the invasion and migration of OSCC.

Overlap phenotypes of the left ventricular noncompaction and hypertrophic cardiomyopathy with complex arrhythmias and heart failure induced by the novel truncated DSC2 mutation.

BACKGROUND: The left ventricular noncompaction cardiomyopathy (LVNC) is a rare subtype of cardiomyopathy associated with a high risk of heart failure (HF), thromboembolism, arrhythmia, and sudden cardiac death. METHODS: The proband with overlap phenotypes of LVNC and hypertrophic cardiomyopathy (HCM) complicates atrial fibrillation (AF), ventricular tachycardia (VT), and HF due to the diffuse myocardial lesion, which were diagnosed by electrocardiogram, echocardiogram and cardiac magnetic resonance imaging. Peripheral blood was collected from the proband and his relatives. DNA was extracted from the peripheral blood of proband for high-throughput target capture sequencing. The Sanger sequence verified the variants. The protein was extracted from the skin of the proband and healthy volunteer. The expression difference of desmocollin2 was detected by Western blot. RESULTS: The novel heterozygous truncated mutation (p.K47Rfs*2) of the DSC2 gene encoding an important component of desmosomes was detected by targeted capture sequencing. The western blots showed that the expressing level of functional desmocollin2 protein (~ 94kd) was lower in the proband than that in the healthy volunteer, indicating that DSC2 p.K47Rfs*2 obviously reduced the functional desmocollin2 protein expression in the proband. CONCLUSION: The heterozygous DSC2 p.K47Rfs*2 remarkably and abnormally reduced the functional desmocollin2 expression, which may potentially induce the overlap phenotypes of LVNC and HCM, complicating AF, VT, and HF.

Targeting desmosomal adhesion and signalling for intestinal barrier stabilization in inflammatory bowel diseases-Lessons from experimental models and patients.

Inflammatory bowel diseases (IBD) such as Crohn's disease (CD) and Ulcerative colitis (UC) have a complex and multifactorial pathogenesis which is incompletely understood. A typical feature closely associated with clinical symptoms is impaired intestinal epithelial barrier function. Mounting evidence suggests that desmosomes, which together with tight junctions (TJ) and adherens junctions (AJ) form the intestinal epithelial barrier, play a distinct role in IBD pathogenesis. This is based on the finding that desmoglein (Dsg) 2, a cadherin-type adhesion molecule of desmosomes, is required for maintenance of intestinal barrier properties both in vitro and in vivo, presumably via Dsg2-mediated regulation of TJ. Mice deficient for intestinal Dsg2 show increased basal permeability and are highly susceptible to experimental colitis. In several cohorts of IBD patients, intestinal protein levels of Dsg2 are reduced and desmosome ultrastructure is altered suggesting that Dsg2 is involved in IBD pathogenesis. In addition to its adhesive function, Dsg2 contributes to enterocyte cohesion and intestinal barrier function. Dsg2 is also involved in enterocyte proliferation, barrier differentiation and induction of apoptosis, in part by regulation of p38MAPK and EGFR signalling. In IBD, the function of Dsg2 appears to be compromised via p38MAPK activation, which is a critical pathway for regulation of desmosomes and is associated with keratin phosphorylation in IBD patients. In this review, the current findings on the role of Dsg2 as a novel promising target to prevent loss of intestinal barrier function in IBD patients are discussed.

[Genetics of complex and syndromic palmoplantar keratoderma]. / Génétique des kératodermies palmoplantaires complexes et syndromiques.

Palmoplantar keratodermas (PPK) comprise a heterogenous group of acquired and hereditary disorders marked by excessive thickening of the epidermis of palms and soles. Hereditary PPKs can be classified into 3 groups: 1) isolated non-syndromic PPKs; 2) complex non-syndromic PPKs associated with other ectodermal defects; and 3) syndromic PPKs associated with extracutaneous manifestations. All types of inheritance have been observed: autosomal dominant, autosomal recessive, X-linked recessive, and mitochondrial. Some of these disorders are restricted to geographic isolates. This review describes the different genetic causes of hereditary syndromic and complex PPKs for which the genes have been identified. The identification of pathogenic variants has consequences in terms of genetic counseling, appropriate medical care and follow-up, especially for PPKs predisposing to hearing loss, cardiomyopathies, benign tumors or carcinomas. In addition, the development of targeted therapies based on pathophysiology of disorders should allow a more effective treatment of these conditions in the near future.

G790del mutation in DSC2 alone is insufficient to develop the pathogenesis of ARVC in a mouse model.

BACKGROUND: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart disease that causes heart failure and/or sudden cardiac death. Several desmosomal genes (DSC2, PKG, PKP2, DSP, and RyR2) are thought to be the causative gene involved in ARVC. Out of them, DSC2 mutations account for 2% of ARVC genetic abnormalities. This study aimed to clarify the effect of G790del mutation in DSC2 on the arrhythmogenic mechanism and cardiac function in a mouse model. RESULT: Neither the heterozygous +/G790del nor homozygous G790del/G790del mice showed structural and functional defects in the right ventricle (RV) or lethal arrhythmia. The homozygous G790del/G790del 6-month-old mice slightly showed left ventricular (LV) dysfunction. Cell shortening decreased with prolongation of intracellular Ca2+ transient in cardiomyocytes isolated from the homozygous G790del/G790del mice, and spontaneous Ca2+ transients were frequently observed in response to isoproterenol. CONCLUSIONS: G790del mutation in DSC2 was not relevant to the pathogenesis of ARVC, but showed a slight contractile dysfunction and Ca2+ dysregulation in the LV.

Cleavage of Desmosomal Cadherins Promotes γ-Catenin Degradation and Benefits Wnt Signaling in Coxsackievirus B3-Induced Destruction of Cardiomyocytes.

Coxsackievirus B3 (CVB3) is the primary etiologic agent of viral myocarditis, a major heart disease that occurs predominantly in children and young adolescents. In the heart, intercalated disks (ICD) are important structural formations that connect adjacent cardiomyocytes to maintain cardiac architecture and mediate signal communication. Deficiency in ICD components, such as desmosome proteins, leads to heart dysfunction. γ-catenin, a component protein of desmosomes, normally binds directly to desmocollin-2 and desmoglein-2. In this study, we found that CVB3 infection downregulated γ-catenin at the protein level but not the mRNA level in mouse HL-1 cardiomyocytes. We further found that this reduction of γ-catenin protein is a result of ubiquitin proteasome-mediated degradation, since the addition of proteasome inhibitor MG132 inhibited γ-catenin downregulation. In addition, we found that desmocollin-2 and desmoglein-2 were cleaved by both viral protease 3C and virus-activated cellular caspase, respectively. These cleavages led to the release of bound γ-catenin from the desmosome into the cytosol, resulting in rapid degradation of γ-catenin. Since γ-catenin shares high sequence homology with ß-catenin in binding the TCF/LEF transcription factor, we further studied the effect of γ-catenin degradation on Wnt/ß-catenin signaling. Luciferase assay showed that γ-catenin expression inhibited Wnt/ß-catenin signaling. This finding was substantiated by qPCR to show that overexpression of γ-catenin downregulated transcription of Wnt signal target genes, c-myc and MMP9, while silencing γ-catenin upregulated these target genes. Finally, we demonstrated that γ-catenin expression inhibited CVB3 replication. In search for the underlying mechanism, we found that silencing γ-catenin caused down-regulation of interferon-ß and its stimulated antiviral genes MDA5, MAVS, and ISG15. Taken together, our results indicate, for the first time, that CVB3 infection causes cardiomyocyte death through, at least in part, direct damage to the desmosome structure and reduction of γ-catenin protein, which in return promotes Wnt/ß-catenin signaling and downregulates interferon-ß stimulated immune responses.

Incorporation of desmocollin-2 into the plasma membrane requires N-glycosylation at multiple sites.

Desmocollin-2 (DSC2) is a desmosomal protein of the cadherin family. Desmosomes are multiprotein complexes, which are involved in cell adhesion of cardiomyocytes and of keratinocytes. The molecular structure of the complete extracellular domain (ECD) of DSC2 was recently described, revealing three disulfide bridges, four N-glycosylation sites, and four O-mannosylation sites. However, the functional relevance of these post-translational modifications for the protein trafficking of DSC2 to the plasma membrane is still unknown. Here, we generated a set of DSC2 mutants, in which we systematically exchanged all N-glycosylation sites, O-mannosylation sites, and disulfide bridges within the ECD and investigated the resulting subcellular localization by confocal laser scanning microscopy. Of note, all single and double N-glycosylation- deficient mutants were efficiently incorporated into the plasma membrane, indicating that the absence of these glycosylation sites has a minor effect on the protein trafficking of DSC2. However, the exchange of multiple N-glycosylation sites resulted in intracellular accumulation. Colocalization analysis using cell compartment trackers revealed that N-glycosylation- deficient DSC2 mutants were retained within the Golgi apparatus. In contrast, elimination of the four O-mannosylation sites or the disulfide bridges in the ECD has no obvious effect on the intracellular protein processing of DSC2. These experiments underscore the importance of N-glycosylation at multiple sites of DSC2 for efficient intracellular transport to the plasma membrane.

The aberrant expression or disruption of desmocollin2 in human diseases.

The desmosome is a member of intercellular junctions that named 'anchoring junction', which contributes to the integrity and homeostasis of tissue structure and function of multicellular living organisms. As an important component of the desmosome and the most widely distributed isoform of desmocollins (DSCs), desmocollin2 (DSC2) has been demonstrated to be essential for the unity of epithelial cells, and served as a vital regulator in signaling processes such as epithelial morphogenesis, differentiation, wound healing, cell apoptosis, migration, and proliferation. Recent studies suggested that the aberrant expression or disruption of DSC2 might lead to some disorders, including heart disorders, certain cancers, and some other human diseases. The distinctions in expression and regulation mechanisms of DSC2 in different human diseases provided a potential target for diagnosis and individualized treatment. Further research is required to certify the signaling capacity of DSC2 and to shed light on the down-stream consequences of the signaling for us to understand the new area of DSC2 biology and the development of certain diseases. This review summarizes the molecular structure and dynamics of desmosome and DSC2, the relationship between the disruption or aberrant expression of DSC2 and human diseases and related molecular mechanisms, as well as the possible prospects.

MicroRNA-130a Regulation of Desmocollin 2 in a Novel Model of Arrhythmogenic Cardiomyopathy.

BACKGROUND: MicroRNAs are small noncoding RNA molecules that play a critical role in regulating physiological and disease processes. Recent studies have now recognized microRNAs as an important player in cardiac arrhythmogenesis. Molecular insight into arrhythmogenic cardiomyopathy (AC) has primarily focused on mutations in desmosome proteins. To our knowledge, models of AC due to microRNA dysregulation have not been reported. Previously, we reported on miR-130a mediated down-regulation of Connexin43. OBJECTIVE: Here, we investigate miR-130a-mediated translational repression of Desmocollin2 (DSC2), as it has a predicted target site for miR-130a. DSC2 is an important protein for cell adhesion, which has been shown to be dysregulated in human AC. METHOD & RESULTS: After induction of miR-130a, transgenic mice demonstrated right ventricular dilation. Surface ECG revealed spontaneous premature ventricular complexes confirming an arrhythmogenic phenotype in αMHC-miR130a mice. Using total protein from whole ventricular lysate, western blot analysis demonstrated an 80% reduction in DSC2 levels in transgenic myocardium. Furthermore, immunofluorescent staining confirmed downregulation of DSC2 in transgenic compared with littermate control myocardium. In transgenic hearts, histologic findings revealed fibrosis and lipid accumulation within both ventricles. To validate DSC2 as a direct target of miR-130a, we performed in vitro target assays in 3T3 fibroblasts, known to express miR-130a. Using a luciferase reporter fused to the 3UTR of DSC2 compared with a control, we found a 42% reduction in luciferase activity with the DSC2 3UTR. This reduction was reversed upon selective inhibition of miR-130a. CONCLUSION: Overexpression of miR-130a results in a disease phenotype characteristic of AC and therefore, may serve as potential model for microRNA-induced AC.

Desmocollin-2 alone forms functional desmosomal plaques, with the plaque formation requiring the juxtamembrane region and plakophilins.

The role of the juxtamembrane region of the desmocollin-2 cytoplasmic domain in desmosome formation was investigated by using gene knockout and reconstitution experiments. When a deletion construct of the desmocollin-2 juxtamembrane region was expressed in HaCaT cells, the mutant protein became localized linearly at the cell-cell boundary, suggesting the involvement of this region in desmosomal plaque formation. Then, desmocollin-2 and desmoglein-2 genes of epithelial DLD-1 cells were ablated by using the CRISPR/Cas9 system. The resultant knockout cells did not form desmosomes, but re-expression of desmocollin-2 in the cells formed desmosomal plaques in the absence of desmoglein-2 and the transfectants showed significant cell adhesion activity. Intriguingly, expression of desmocollin-2 lacking its juxtamembrane region did not form the plaques. The results of an immunoprecipitation and GST-fusion protein pull-down assay suggested the binding of plakophilin-2 and -3 to the region. Ablation of plakophilin-2 and -3 genes resulted in disruption of the plaque-like accumulation and linear localization of desmocollin-2 at intercellular contact sites. These results suggest that the juxtamembrane region of desmocollin-2 and plakophilins are involved in the desmosomal plaque formation, possibly through the interaction between this region and plakophilins.