Role Of Desmosomes Research Articles

The role of desmosomes in the ear plug formation in the bowhead whale (Balaena mysticetus).

The external acoustic meatus (EAM) of most baleen whales accumulates cellular debris annually in the lumen as whales age, forming a lamellated ear plug. The bowhead whale ear plug is formed from annually molting lining of the EAM as the entire epithelium releases at the level of the stratum basale during the spring migration. Epithelial regeneration is mostly completed by the fall migration, remaining intact for 6-7 months before being torn off the following spring. Desmosomes are integral to cell-cell adhesion with connecting desmosomal cadherins desmoglein (dsg) and desmocollin (dsc). Paraffin sections of the oral cavity and EAM lining of spring and fall adult bowhead whales, as well as the EAM of spring-caught juvenile, were immunohistochemically examined for the presence of these cadherins. In all fall specimens, both cadherins occurred in all layers except the superficial keratinous layer of the oral cavity. In spring, three different conditions existed: (a) oral cavity of spring-caught adults had reduced cadherins, with superficial fissuring in its keratinized layer and vacuolation in the upper stratum spinosum; (b) EAM of juvenile spring-caught whales displayed fissuring with accompanying reduction of both cadherins in its superficial lining; and (c) EAM lining of spring-caught adults displayed deep fissures, reduced cadherins, and absence of dsc1 in the fissuring zone. These results suggest that shedding of skin layers in mammals, whether normal molting, pathological, or the result of injury and wound repair all revolve around desmosome function. The specific role, structure, and location of these two cadherins need to be further addressed.

The role of desmosomes in carcinogenesis.

Desmosomes, which are intercellular adhesive complexes, are essential for the maintenance of epithelial homeostasis. They are located at the cell membrane, where they act as anchors for intermediate filaments. Downregulation of desmosome proteins in various cancers promotes tumor progression. However, the role of desmosomes in carcinogenesis is still being elucidated. Recent studies revealed that desmosome family members play a crucial role in tumor suppression or tumor promotion. This review focuses on studies that provide insights into the role of desmosomes in carcinogenesis and address their molecular functions.

Abstract 5054: Role and signaling of desmosomal DSP and PKP1 in ovarian cancer

Abstract Identification of driver genes/proteins in EOC tumorigenic processes is critical to increase the cure rate for late stage epithelial ovarian cancer (EOC), which has not been in improved over several decades. We have developed a highly aggressive EOC cell line (ID8-P1 or P1) from ID8-P0 (without in vivo passage, or P0) through in vivo passage in C57BL6 mice. Two genes encode important desmosome components, desmoplakin (Dsp) and plakophilin 1 (Pkp1) were found to be significantly over-expressed in P1 vs. P0 cells, as well as human EOC cells. DSP is an obligate component of functional desmosomes that anchors intermediate filaments to desmosomal plaques. Pkp1 encodes a member of the arm-repeat (armadillo) and plakophilin (PKP) gene families. Our understanding of the functions of desmosomes in cancer is just emerging and the role of desmosomes in EOC is totally unknown. Our data showed the novel functions of DSP in anoikis-resistance and SRC activation using shRNA-mediated DSP-knocked down (KD) stable cell lines. In addition, we found that ID8-P1 cells formed spheroids and P0 cells tended to be single cells when they were cultured in suspension. KD-Dsp dissociated spheroids, suggesting that desmosomes play an important role in spheroid formation, which may be directly related to anoikis-, drug-resistance, and/or the cancer stem cell (CSC) concepts. Moreover, we found that enhanced glycolysis was involved in the increased anoikis-resistance of ID8-P1 cells and an inhibitor of glycolysis, shikonin (SHK) was a potent anoikis-resistance inhibitor and P1 cells gained more drug-resistance, when compared to P0 cells, with the IC50s were 1.7 and 7.4 μM for P0 and P1 cells, respectively. Similarly, the IC50s were 2.4 and 8.1 μM for human EOC PE01 and PE04 cells, respectively. PE01 and PE04 cell lines are identified to represent high-grade serous ovarian cancer (HGSC), which were derived from the same patient before (PE01) and after (PE04) the onset of drug resistance to cis-platinum (CDDP), chlorambucil, and 5-fluorouracil. PP2 (a SRC nhibitor) and SHK were able to dissociate the cell-cells aggregates/spheroids in EOC cells. The previously unknown role of DSP and/or PKP1 in EOC may be related to their signaling activities outside desmosomes. Cells staining of PKP1 protein showed its cytosolic and perinuclear location, providing supporting and proof-of-concept data. Together, our data have suggested the novel links among DSP, PKP1, anoikis-resistance, SRC activation, cell-cell-aggregation, and drug-resistance. These data provide a basis for developing new modalities for EOC treatment. Citation Format: Yan Xu, Qingchun Cai. Role and signaling of desmosomal DSP and PKP1 in ovarian cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5054.

Desmosome regulation and signaling in disease.

Desmosomes are cell-cell adhesive organelles with a well-known role in forming strong intercellular adhesion during embryogenesis and in adult tissues subject to mechanical stress, such as the heart and skin. More recently, desmosome components have also emerged as cell signaling regulators. Loss of expression or interference with the function of desmosome molecules results in diseases of the heart and skin and contributes to cancer progression. However, the underlying molecular mechanisms that result in inherited and acquired disorders remain poorly understood. To address this question, researchers are directing their studies towards determining the functions that occur inside and outside of the junctions and the extent to which functions are adhesion-dependent or independent. This review focuses on recent discoveries that provide insights into the role of desmosomes and desmosome components in cell signaling and disease; wherever possible, we address molecular functions within and outside of the adhesive structure.

Desmosomal Adhesion In Vivo

Desmosomes are intercellular junctions that provide strong adhesion or hyper-adhesion in tissues. Here, we discuss the molecular and structural basis of this with particular reference to the desmosomal cadherins (DCs), their isoforms and evolution. We also assess the role of DCs as regulators of epithelial differentiation. New data on the role of desmosomes in development and human disease, especially wound healing and pemphigus, are briefly discussed, and the importance of regulation of the adhesiveness of desmosomes in tissue dynamics is considered.

Targeting DSG3: from pemphigus to squamous cell carcinoma

Desmosomes are specialized structures of the cell membrane that are crucial for the establishment and maintenance of cell–cell adhesion and tissue integrity. Transmembrane proteins of desmosomes, desmogleins, and desmocollins are responsible for extracellular binding and, thus, are important for interkeratinocyte cohesion. Desmoglein 3 (DSG3) is a member of the desmoglein subfamily of cadherin cell adhesion molecule superfamily. It is mainly expressed in stratified epithelia, including the basal and suprabasilar epidermal layers and throughout the oral epithelium layers. In the human autoimmune blistering disease pemphigus vulgaris, autoantibodies against DSG3 cause loss of cell–cell adhesion (acantholysis) with resultant epidermal and mucosal blisters. More recently, a potential role of desmosomes in cancer development has been hypothesized. To this regard, several investigations have focused on the possible contribution of DSG3 in carcinogenesis. In this article, the role of DSG3 in the process of squamous cell carcinogenesis and the controversies concerning this issue will be discussed.

Desmosomes: new perpetrators in tumour suppression

Adherens junctions, which are intercellular adhesive complexes that are crucial for maintaining epithelial homeostasis, are downregulated in many cancers to promote tumour progression. However, the role of desmosomes - adhesion complexes that are related to adherens junctions - in carcinogenesis has remained elusive. Recent studies using mouse genetic approaches have uncovered a role for desmosomes in tumour suppression, demonstrating that desmosome downregulation occurs before that of adherens junctions to drive tumour development and early invasion, suggesting a two-step model of adhesion dysfunction in cancer progression.

Crosstalk between desmoglein-2/desmocollin-2/Src kinase and coxsackie and adenovirus receptor/ZO-1 protein complexes, regulates blood-testis barrier dynamics

Morphological studies in the testis reported the presence of ‘desmosome-like’ junctions between Sertoli cells at the blood-testis barrier, whose function is also constituted by tight junctions and basal ectoplasmic specializations. Unfortunately, little is known about the role of desmosomes in blood-testis barrier dynamics. This study aims to fill this gap with the functional investigation of two desmosomal cadherins, desmoglein-2 and desmocollin-2, by their specific knockdown in Sertoli cells cultured in vitro. Reminiscent of the blood-testis barrier in vivo, desmosome-like structures were visible by electron microscopy when Sertoli cells were cultured at high density, thereby forming a polarized epithelium with functional cell junctions. At this point, we opted to focus our efforts on desmoglein-2 and desmocollin-2 based on results which illustrated desmosomal mRNAs to be expressed by Sertoli and germ cells, as well as on results which illustrated desmoglein-2 to co-immunoprecipitate with plakoglobin, c-Src and desmocollin-2. Simultaneous knockdown of desmoglein-2 and desmocollin-2 not only led to a reduction in and mislocalization of zonula occludens-1, but also perturbed the localization of c-Src and coxsackie and adenovirus receptor at the cell–cell interface, resulting in disruption of tight junction permeability barrier. We hereby propose a novel regulatory protein complex composed of desmoglein-2, desmocollin-2, c-Src, coxsackie and adenovirus receptor and zonula occludens-1 at the blood-testis barrier.

Ultrastructure of bronchial biopsies from patients with allergic and non-allergic asthma

Epithelial damage is commonly found in airways of asthma patients. The aim of this study was to investigate epithelial damage in allergic and non-allergic asthma at the ultrastructural level. Bronchial biopsies obtained from patients with allergic asthma (n=11), non-allergic asthma (n=7), and healthy controls (n=5) were studied by transmission electron microscopy. Epithelial damage was found to be extensive in both asthma groups. Both in basal and in columnar cells, relative desmosome length was reduced by 30-40%. In columnar cells, half-desmosomes (i.e., desmosomes of which only one side was present) were frequently noticed. Eosinophils showing piece-meal degranulation were commonly observed in allergic asthma. Degranulating mast cells were more often observed in allergic asthma. Goblet cell hyperplasia was only found in allergic asthma. Lymphocytes were increased in both groups. In both groups, the lamina densa of the basal lamina was thicker than the control by about 40-50%. In allergic asthma the lamina densa was irregular with focal thickening. While there was always a tendency for changes (epithelial damage, desmosomes, degranulating mast cells, basal lamina) to be more extensive in allergic asthma compared to non-allergic asthma, there was no significant difference between the two groups in this respect. Reduced desmosomal contact may be an important factor in the epithelial shedding observed in patients with asthma.

Desmosomal adhesion inhibits invasive behavior.

Recent studies of human disease and transgenic animal experiments have clearly demonstrated the importance of desmosomes in normal tissue architecture. Furthermore, desmosomal components are down-regulated in certain types of carcinomas, suggesting a possible role for desmosomes in suppression of invasion and metastasis. However, there is no functional evidence to support such a hypothesis. To obtain such evidence, we needed to generate desmosomal adhesion in an invasive cell line. We show that expression of multiple desmosomal components (the desmosomal cadherins, desmocollin and desmoglein, and the armadillo protein, plakoglobin) in nonadhesive L929 fibroblasts generates adhesion in aggregation assays. This adhesion is specifically blocked by short peptides corresponding to the putative cell adhesion recognition sites of desmocollin and desmoglein. This result provides an experimental demonstration of the functional importance of the cell adhesion recognition sites of desmocollin and desmoglein and indicates that both desmosomal cadherins are specifically involved in this adhesion. Moreover, whereas parental L929 cells are strongly invasive into collagen gels, we show that invasion is substantially inhibited in cells transfected with desmosomal components. Invasion is restored by treating the transfected cells with anti-adhesion peptides, indicating that desmosomal adhesion specifically blocks invasion in culture. Our results support the suggestion that desmosomes have a role in suppression of tumor spreading.

Plasma membrane differentiations of keratinizing cells of the wool follicle: II. Desmosomes

Desmosomes have been studied in selected cell lines in the keratinizing regions of the Romney wool follicle using thin section and freeze-etch methods. The numbers of desmosomes increased during differentiation of the cortex, Henle's layer, and the fiber cuticle. Henle's layer desmosomes were larger than cortical desmosomes at a level above the dermal papilla and were incorporated in part, at least, into the hardened cell surface. Cortical desmosomes reached their maximum numbers in the region above the dermal papilla, where they constituted about 5% of the plasma membrane surface area. Both cortical desmosomes and those associated with fiber cuticle cells dedifferentiated in the region where Henle's cells harden. A possible sequence of events during the formation and dedifferentiation of cortical desmosomes is presented. The role of desmosomes in intercellular adhesion and as a site for the attachment of cytoplasmic fibrils, particularly early macrofibrils, is discussed.