Arrhythmogenic cardiomyopathy-related cadherin variants affect desmosomal binding kinetics.

Cadherins are calcium dependent adhesion proteins that establish and maintain the intercellular mechanical contact by bridging the gap between adjacent cells. Desmoglein-2 (Dsg2) and desmocollin-2 (Dsc2) are tissue specific cadherin isoforms of the cell-cell contact in cardiac desmosomes. Mutations in the DSG2-gene and in the DSC2-gene are related to arrhythmogenic right ventricular cardiomyopathy (ARVC) a rare but severe heart muscle disease. Here, several possible homophilic and heterophilic binding interactions of wild-type Dsg2, wild-type Dsc2, as well as one Dsg2- and two Dsc2-variants, each associated with ARVC, are investigated. Using single molecule force spectroscopy (SMFS) with atomic force microscopy (AFM) and applying Jarzynski's equality the kinetics and thermodynamics of Dsg2/Dsc2 interaction can be determined. The free energy landscape of Dsg2/Dsc2 dimerization exposes a high activation energy barrier, which is in line with the proposed strand-swapping binding motif. Although the binding motif is not affected by any of the mutations, the binding kinetics of the interactions differ significantly from the wild-type. While wild-type cadherins exhibit an average complex lifetime of approx. 0.3 s interactions involving a variant consistently show - lifetimes that are substantially larger. The lifetimes of the wild-type interactions give rise to the picture of a dynamic adhesion interface consisting of continuously dissociating and (re)associating molecular bonds, while the delayed binding kinetics of interactions involving an ARVC-associated variant might be part of the pathogenesis. Our data provide a comprehensive and consistent thermodynamic and kinetic description of cardiac cadherin binding, allowing detailed insight into the molecular mechanisms of cell adhesion.

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.

Desmocollin-1 is associated with pro-metastatic phenotype of luminal A breast cancer cells and is modulated by parthenolide.

BACKGROUND: Desmocollin-1 (DSC1) is a desmosomal transmembrane glycoprotein that maintains cell-to-cell adhesion. DSC1 was previously associated with lymph node metastasis of luminal A breast tumors and was found to increase migration and invasion of MCF7 cells in vitro. Therefore, we focused on DSC1 role in cellular and molecular mechanisms in luminal A breast cancer and its possible therapeutic modulation. METHODS: Western blotting was used to select potential inhibitor decreasing DSC1 protein level in MCF7 cell line. Using atomic force microscopy we evaluated effect of DSC1 overexpression and modulation on cell morphology. The LC-MS/MS analysis of total proteome on Orbitrap Lumos and RNA-Seq analysis of total transcriptome on Illumina NextSeq 500 were performed to study the molecular mechanisms associated with DSC1. Pull-down analysis with LC-MS/MS detection was carried out to uncover DSC1 protein interactome in MCF7 cells. RESULTS: Analysis of DSC1 protein levels in response to selected inhibitors displays significant DSC1 downregulation (p-value ≤ 0.01) in MCF7 cells treated with NF-κB inhibitor parthenolide. Analysis of mechanic cell properties in response to DSC1 overexpression and parthenolide treatment using atomic force microscopy reveals that DSC1 overexpression reduces height of MCF7 cells and conversely, parthenolide decreases cell stiffness of MCF7 cells overexpressing DSC1. The LC-MS/MS total proteome analysis in data-independent acquisition mode shows a strong connection between DSC1 overexpression and increased levels of proteins LACRT and IGFBP5, increased expression of IGFBP5 is confirmed by RNA-Seq. Pathway analysis of proteomics data uncovers enrichment of proliferative MCM_BIOCARTA pathway including CDK2 and MCM2-7 after DSC1 overexpression. Parthenolide decreases expression of LACRT, IGFBP5 and MCM_BIOCARTA pathway specifically in DSC1 overexpressing cells. Pull-down assay identifies DSC1 interactions with cadherin family proteins including DSG2, CDH1, CDH3 and tyrosine kinase receptors HER2 and HER3; parthenolide modulates DSC1-HER3 interaction. CONCLUSIONS: Our systems biology data indicate that DSC1 is connected to mechanisms of cell cycle regulation in luminal A breast cancer cells, and can be effectively modulated by parthenolide.

DSC2 Suppresses the Metastasis of Gastric Cancer through Inhibiting the BRD4/Snail Signaling Pathway and the Transcriptional Activity of ß-Catenin.

Downregulated DSC2 involved in the metastasis of cancers. Unfortunately, its role on the development of gastric cancer (GC) and the potential mechanisms remain unclear. Bioinformatics analysis, Western blot, qRT-PCR, and immunohistochemistry were performed to detect the DSC2 levels of human GC and normal stomach tissues. The role of DSC2 and the downstream signaling in gastric carcinogenesis were explored by using GC specimens, GC cells with different DSC2 expression, inhibitors, and mouse metastasis models. We found that the level of DSC2 decreased significantly in GC tissues and cells. Recovered DSC2 inhibited the invasion and migration of GC cells both in culture and in xenografts. Mechanistically, DSC2 could not only decrease Snail level and nuclear BRD4 level by forming DSC2/BRD4, but also inhibit nuclear translocation of ß-catenin. We concluded that DSC2 inhibited the metastasis of GC, and the underlying mechanisms were closely related to the regulation on nuclear translocation of BRD4 and ß-catenin. Our results suggest that DSC2 may serve as a novel therapeutic target for GC.

Autoantibodies to DSC3 in Pemphigus Exclusively Recognize Calcium-Dependent Epitope in Extracellular Domain 2.

Pemphigus is a group of autoimmune bullous diseases characterized by the presence of autoantibodies against adhesion molecules, desmogleins, and desmocollins (DSCs). The pathogenicity of anti-DSC3 antibodies in pemphigus has been demonstrated; however, its characteristics have not yet been elucidated. We aimed to analyze the characteristics of anti-DSC3 antibodies using DSC3 domain‒swapped desmoglein 2 molecules in which the prosequence and five extracellular (EC) domains of desmoglein 2 were replaced with the corresponding domains of human DSC3. Using these proteins, we established an ELISA and analyzed sera from 56 patients with pemphigus. In 34 pemphigus sera positive for DSC3 full-EC domains, 15 sera (44.1%) were positive for EC2 domain, whereas other domains were rarely positive. We assessed the reactivity to a calcium-dependent epitope in DSC3 by ELISA with EDTA. The reactivity with the EC2 domain was mostly compromised in the presence of EDTA. In the in vitro assay, IgG from patients with paraneoplastic pemphigus preadsorbed with EC2 prevented both reduction of DSC3 and keratinocyte dissociation as compared with that with EDTA-treated EC2. This study revealed a predominant recognition of calcium-dependent epitopes in EC2 domain by anti-DSC3 antibodies and its pathogenicity on keratinocyte adhesion through DSC3 depletion.

CircRAB11FIP1 promoted autophagy flux of ovarian cancer through DSC1 and miR-129.

At present, no systematic and in-depth study is available on the function and potential mechanisms of circular RNA in autophagy. This study aimed to screen the expression profiles of circRNA, miRNA, and mRNA of ovarian cancer cells induced by Torin 1 (10 µM). The expression profiles of circRNA, miRNA, and mRNA were analyzed with next-generation sequencing technology. CircRAB11FIP1 expression was elevated in epithelial ovarian cancer (EOC) tissues than in normal ovarian tissues. Silencing circRAB11FIP1 inhibited the autophagic flux of ovarian cancer SKOV3 cells. However, circRAB11FIP1 overexpression activated the autophagic flux of ovarian cancer A2780 cells. CircRAB11FIP1-induced autophagy accelerated EOC proliferation and invasion. Also, circRAB11FIP1 directly bound to miR-129 and regulated its targets ATG7 and ATG14. CircRAB11FIP1 bound to desmocollin 1to facilitate its interaction with ATG101. Also, circRAB11FIP1 directly bound to the mRNA of fat mass and obesity-associated protein and promoted its expression. Then, circRAB11FIP1 mediated mRNA expression levels of ATG5 and ATG7 depending on m6A. In general, this study demonstrated that circRAB11FIP1 regulated ATG7 and ATG14 by sponging miR-129. The data suggested that circRAB11FIP1 might serve as a candidate biomarker for EOC diagnosis and treatment.

Regulation of intestinal epithelial intercellular adhesion and barrier function by desmosomal cadherin desmocollin-2.

The role of desmosomal cadherin desmocollin-2 (Dsc2) in regulating barrier function in intestinal epithelial cells (IECs) is not well understood. Here, we report the consequences of silencing Dsc2 on IEC barrier function in vivo using mice with inducible intestinal-epithelial-specific Dsc2 knockdown (KD) (Dsc2ERΔIEC). While the small intestinal gross architecture was maintained, loss of epithelial Dsc2 influenced desmosomal plaque structure, which was smaller in size and had increased intermembrane space between adjacent epithelial cells. Functional analysis revealed that loss of Dsc2 increased intestinal permeability in vivo, supporting a role for Dsc2 in the regulation of intestinal epithelial barrier function. These results were corroborated in model human IECs in which Dsc2 KD resulted in decreased cell-cell adhesion and impaired barrier function. It is noteworthy that Dsc2 KD cells exhibited delayed recruitment of desmoglein-2 (Dsg2) to the plasma membrane after calcium switch-induced intercellular junction reassembly, while E-cadherin accumulation was unaffected. Mechanistically, loss of Dsc2 increased desmoplakin (DP I/II) protein expression and promoted intermediate filament interaction with DP I/II and was associated with enhanced tension on desmosomes as measured by a Dsg2-tension sensor. In conclusion, we provide new insights on Dsc2 regulation of mechanical tension, adhesion, and barrier function in IECs.

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.

Desmocollin-2 promotes intestinal mucosal repair by controlling integrin-dependent cell adhesion and migration.

The intestinal mucosa is lined by a single layer of epithelial cells that forms a tight barrier, separating luminal antigens and microbes from underlying tissue compartments. Mucosal damage results in a compromised epithelial barrier that can lead to excessive immune responses as observed in inflammatory bowel disease. Efficient wound repair is critical to reestablish the mucosal barrier and homeostasis. Intestinal epithelial cells (IEC) exclusively express the desmosomal cadherins, Desmoglein-2 and Desmocollin-2 (Dsc2) that contribute to mucosal homeostasis by strengthening intercellular adhesion between cells. Despite this important property, specific contributions of desmosomal cadherins to intestinal mucosal repair after injury remain poorly investigated in vivo. Here we show that mice with inducible conditional knockdown (KD) of Dsc2 in IEC (Villin-CreERT2; Dsc2 fl/fl) exhibited impaired mucosal repair after biopsy-induced colonic wounding and recovery from dextran sulfate sodium-induced colitis. In vitro analyses using human intestinal cell lines after KD of Dsc2 revealed delayed epithelial cell migration and repair after scratch-wound healing assay that was associated with reduced cell-matrix traction forces, decreased levels of integrin ß1 and ß4, and altered activity of the small GTPase Rap1. Taken together, these results demonstrate that epithelial Dsc2 is a key contributor to intestinal mucosal wound healing in vivo.

Proteomics Identification and Validation of Desmocollin-1 and Catechol-O-Methyltransferase as Proteins Associated with Breast Cancer Cell Migration and Metastasis.

Biological treatment of many cancers currently targets membrane bound receptors located on a cell surface. To identify novel membrane proteins associated with migration and metastasis of breast cancer cells, a more migrating subpopulation of MDA-MB-231 breast cancer cell line is selected and characterized. A high-resolution quantitative mass spectrometry with SILAC labeling is applied to analyze their surfaceome and it is compared with that of parental MDA-MB-231 cells. Among 824 identified proteins (FDR < 0.01), 128 differentially abundant cell surface proteins with at least one transmembrane domain are found. Of these, i) desmocollin-1 (DSC1) is validated as a protein connected with lymph node status of luminal A breast cancer, tumor grade, and Her-2 status by immunohistochemistry in the set of 96 primary breast tumors, and ii) catechol-O-methyltransferase is successfully verified as a protein associated with lymph node metastasis of triple negative breast cancer as well as with tumor grade by targeted data extraction from the SWATH-MS data of the same set of tissues. The findings indicate importance of both proteins for breast cancer development and metastasis and highlight the potential of biomarker validation strategy via targeted data extraction from SWATH-MS datasets.

Immunohistochemical staining of skin-expressed proteins to identify exfoliated epidermal cells for forensic purposes.

The determination of cell type in biological casework samples would be helpful to identify the type of body fluids and interpret the DNA source in forensic laboratories. Exfoliated epidermal cells are considered to be a reasonable source of touch DNA; therefore, we developed and assessed an immunohistochemistry (IHC) procedure for identifying exfoliated epidermal cells as a screening test of touch DNA samples. Among five candidate protein markers investigated in this study, keratin 10 and kallikrein-related peptidase 5 were strongly expressed in the stratum corneum layer of the skin; however, their specificity was insufficient to identify epidermal cells. In contrast, IHC for corneodesmosin (CDSN), desmocollin 1 (DSC1), and filaggrin (FLG) was considered to be applicable because of their detectability and specificity on skin swab samples. Actually, CDSN and DSC1 could be good markers for exfoliated epidermal cells on touched contact traces that were contaminated with many unidentified impurities. Besides, positivity for FLG on mock casework samples appeared to be lower than for the other markers, which might be caused by its instability. Finally, the relationship between positivity for IHC and DNA yield was analyzed using skin swab samples. Although it was difficult to determine these correlations quantitatively because of the heterogeneous distribution of cells and the presence of cell-free DNA, the DNA-quantifiable samples analyzed in this study contained at least some of IHC-positive epidermal cells. In conclusion, IHC detection of skin-enriched proteins, especially CDSN and DSC1, could be useful for screening samples that have been handled or touched by someone before DNA analysis.

Influence of Vitamin D on Corneal Epithelial Cell Desmosomes and Hemidesmosomes.

Purpose: We have observed noticably weak epithelial attachment in vitamin D receptor knockout mice (VDR KO) undergoing epithelial debridement. We hypothesized that VDR KO negatively affects corneal epithelial cell desmosomes and/or hemidesmosomes. Methods: Transcript levels of desmosome and hemidesmosome proteins in VDR KO corneas were assessed by qPCR. Western blotting and immunochemistry were used to detect proteins in cultured cells exposed to 1,25(OH)2D3 and 24R,25(OH)2D3. Results: VDR KO resulted in decreased corneal desmosomal desmoglein 1 (DSG1) and desmocollin 2 (DSC2) mRNA, and hemidesmosomal plectin mRNA. DSG1 and plectin protein expression were reduced in VDR KO corneas. DSG1 protein expression increased in VDR wild types (VDR WT) and VDR KO mouse primary epithelial cells (MPCEC) treated with 1,25(OH)2D3 and 24R,25(OH)2D3. 24R,25(OH)2D3 treatment resulted in increased plectin and integrin ß4 levels in VDR WT MPCEC, and decreased levels in VDR KO MPCEC. Treatment of human corneal epithelial cells (HCEC) with 1,25(OH)2D3 and 24R,25(OH)2D3 resulted in increased DSC2 and DSG1 protein expression. Plectin and integrin ß4 were only increased in 24R,25(OH)2D3 treated HCEC. Conclusions: VDR KO results in reduced desmosomal and hemidesmosomal mRNA and protein levels. 1,25(OH)2D3 and 24R,25(OH)2D3 increased DSG1 protein in all cells tested. For hemidesmosome proteins, 24R,25(OH)2D3 increased plectin and integrin ß4 protein expression in VDR WT and HCEC, with decreased expression in VDR KO MPCEC. Thus, vitamin D3 is involved in desmosome and hemidesmosome junction formation/regulation, and their decreased expression likely contributes to the loosely adherent corneal epithelium in VDR KO mice. Our data indicate the presence of a VDR-independent pathway.

Ultraviolet light degrades the mechanical and structural properties of human stratum corneum.

Prolonged exposure of human skin to sunlight causes photodamage, which induces the early onset of wrinkles and increased tissue fragility. While solar ultraviolet (UV) light is considered to have the most damaging effect, the UV range that is most harmful remains a topic of significant debate. In this study, we take a first step towards elucidating biomechanical photoageing effects by quantifying how exposure to different UV ranges and dosages impacts the mechanical and structural properties of human stratum corneum (SC), the most superficial skin layer. Mechanical testing reveals that irradiation of isolated human SC to UVA (365 nm), UVB (302 nm), or UVC (265 nm) light with dosages of up to 4000 J/cm2 notably alters the elastic modulus, fracture stress, fracture strain, and work of fracture. For equivalent incident dosages, UVC degrades SC the greatest. However, upon discounting reflected and transmitted components of the incident light, a generalized scaling law relating the photonic energy absorbed by the SC to the energy cost of tissue fracture emerges. This relationship indicates that no one UV range is more damaging than another. Rather, the magnitude of absorbed UV energy governs the degradation of tissue mechanical integrity. Subsequent structural studies are performed to elucidate the cause of this mechanical degradation. UV absorption scales with the spatial dispersion of desmoglein 1 (Dsg 1), a component of corneocyte cell-cell junctions, away from intercellular sites. Combining both scaling laws, we establish a mechanical-structural model capable of predicting UV induced tissue mechanical integrity from Dsg 1 dispersion.

Depot-medroxyprogesterone acetate reduces genital cell-cell adhesion molecule expression and increases genital herpes simplex virus type 2 infection susceptibility in a dose-dependent fashion.

OBJECTIVE: Analyzing ectocervical biopsy tissue from women before and after they initiated use of depot-medroxyprogesterone acetate (DMPA), we previously reported this progestin reduces levels of the cell-cell adhesion molecule (CCAM) desmoglein-1 and increases genital mucosal permeability. We likewise saw treating mice with 1.0 mg of DMPA reduced vaginal CCAM expression and increased genital pathogen susceptibility. Herein, we used dose-response studies to delimit DMPA doses and serum MPA levels in mice associated with impaired genital mucosal barrier function and enhanced susceptibility to low-dose herpes simplex virus type 2 (HSV-2) infection. STUDY DESIGN: We compared genital CCAM expression, genital mucosal permeability, and susceptibility to genital inoculation with 103 plaque-forming units of HSV-2 among mice in estrus vs. after treatment with 0.01 mg, 0.1 mg, 0.3 mg, or 1.0 mg of DMPA. RESULTS: Compared to mice in estrus, DMPA treatment in a dose-dependent fashion significantly reduced desmoglein 1α (Dsg1a) and desmocollin-1 (Dsc1) gene expression, reduced DSG1 protein levels, and increased genital mucosal permeability to a low molecular weight molecule. While no mice infected with HSV-2 in estrus died, we respectively saw 50% and 100% mortality in mice administered 0.1 mg or 0.3 mg of DMPA. At time of infection, mean serum MPA levels in mice administered the 0.1 mg or 0.3 mg doses were 3.8 nM and 13.0 nM respectively (values comparable to trough and peak MPA serum levels in women using DMPA). CONCLUSIONS: Mice with pharmacologically relevant serum MPA concentrations display significant changes in genital CCAM expression, genital mucosal barrier function, and HSV-2 susceptibility.

MLS128 antibody-induced suppression of colon cancer cell growth is mediated by a desmocollin and a 110 kDa glycoprotein.

Protein glycosylation is a diverse form of post-translational modification. Two to three consecutive O-linked N-acetylgalactosamines (Tn-antigens) are recognized by antibodies such as MLS128. MLS128 mAb inhibited cell growth and bound to a 110 kDa glycoprotein (GP) in LS180 and HT29 colon cancer cells. However, purification and identification of the 110 kDa GP was unsuccessful due to its low abundance. The present study used a highly sophisticated and sensitive mass spectrometry method to identify proteins immunoprecipitated with MLS128 and separated by two-dimensional gel electrophoresis. Three desmosome components were identified. Of these, desmocollin and desmoglein shared many similar characteristics, including molecular mass, pI, and potential Tn-antigen sites. Western blotting analyses of LS180 cell lysates revealed a common 110 kDa band recognized by MLS128 and anti-desmocollin, but not by anti-desmoglein. Immunofluorescence microscopy of LS180 cells revealed that desmocollin is membrane-bound, while desmoglein is primarily localized in the cytosol. Confocal microscopy demonstrated colocalization of the desmocollin-specific antibody with the MLS128 antibody on the cell membrane, suggesting that desmocollin may contain Tn-antigens recognized by MLS128. Treatment of LS180 cells with siRNA to knock down desmocollin expression or a desmocollin-specific antibody decreased cell viability, suggesting a critical role for this protein in cell growth and survival. N-glycosidase F digestion of the 110 kDa GP and desmocollin suggested that although both proteins contain N-glycosylation sites, they are not identical. These findings suggest that desmocollin colocalizes with the 110 kDa GP and that growth inhibition induced by the MLS128 antibody may be mediated through a mechanism that involves desmocollin.

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.

Desmocollin 3 has a tumor suppressive activity through inhibition of AKT pathway in colorectal cancer.

Desmocollin 3 (DSC3) is a transmembrane adhesion protein of desmosomes and involved in carcinogenesis in various cancer types. Downregulation of DSC3 has been reported in colorectal cancer (CRC). However, the function of DSC3 in CRC has not yet been elucidated. In this study, we performed cell-based functional analysis after DSC3 overexpression by stable transfection and knockdown by siRNA in CRC cells. It turned out that overexpression of DSC3 reduced cell proliferation, colony forming ability, induced G0/G1 cell cycle arrest and promoted apoptosis. Further pathway analysis showed that overexpression of DSC3 significantly inhibited the activity of AKT pathway and increased the expression of E-cadherin as well as p53 and p21. In contrast, siRNA-mediated knockdown of DSC3 increased cell proliferation and colony formation, activated the AKT pathway and decreased the expression of E-cadherin as well as p53 and p21. Additionally, in primary CRC patient samples, the expression of DSC3 protein was significantly related to the expression of desmocollin 1 (DSC1) and desmocollin 2 (DSC2) as well as E-cadherin (p < 0.001 respectively). Taken together, our data reveal that DSC3 suppresses CRC cell growth through inhibition of AKT pathway and regulation of E-cadherin. DSC3 may serve as a novel therapeutic target for CRC.

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.