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Current Biology : CB Aug 2021The epidermis is a stratified epithelium in which structural and functional features are polarized across multiple cell layers. This type of polarity is essential for...
The epidermis is a stratified epithelium in which structural and functional features are polarized across multiple cell layers. This type of polarity is essential for establishing the epidermal barrier, but how it is created and sustained is poorly understood. Previous work identified a role for the classic cadherin/filamentous-actin network in establishment of epidermal polarity. However, little is known about potential roles of the most prominent epidermal intercellular junction, the desmosome, in establishing epidermal polarity, in spite of the fact that desmosome constituents are patterned across the apical to basal cell layers. Here, we show that desmosomes and their associated intermediate filaments (IFs) are key regulators of mechanical polarization in epidermis, whereby basal and suprabasal cells experience different forces that drive layer-specific functions. Uncoupling desmosomes and IF or specific targeting of apical desmosomes through depletion of the superficial desmosomal cadherin, desmoglein 1, impedes basal stratification in an in vitro competition assay and suprabasal tight junction barrier functions in 3D reconstructed epidermis. Surprisingly, disengaging desmosomes from IF also accelerated the expression of differentiation markers, through precocious activation of the mechanosensitive transcriptional regulator serum response factor (SRF) and downstream activation of epidermal growth factor receptor family member ErbB2 by Src family kinase (SFK)-mediated phosphorylation. This Dsg1-SFK-ErbB2 axis also helps maintain tight junctions and barrier function later in differentiation. Together, these data demonstrate that the desmosome-IF network is a critical contributor to the cytoskeletal-adhesive machinery that supports the polarized function of the epidermis.
Topics: Cadherins; Desmoplakins; Desmosomes; Epidermal Cells; Epidermis
PubMed: 34107301
DOI: 10.1016/j.cub.2021.05.021 -
Cellular and Molecular Life Sciences :... Apr 2022Desmosomes are intercellular junctions which mediate cohesion and communication in tissues exposed to mechanical strain by tethering the intermediate filament...
Desmosomes are intercellular junctions which mediate cohesion and communication in tissues exposed to mechanical strain by tethering the intermediate filament cytoskeleton to the plasma membrane. While mature desmosomes are characterized by a hyperadhesive, Ca-independent state, they transiently loose this state during wound healing, pathogenesis and tissue regeneration. The mechanisms controlling the hyperadhesive state remain incompletely understood. Here, we show that upon Ca-induced keratinocyte differentiation, expression of keratin 17 (K17) prevents the formation of stable and hyperadhesive desmosomes, accompanied by a significant reduction of desmoplakin (DP), plakophilin-1 (PKP1), desmoglein-1 (Dsg1) and -3 (Dsg3) at intercellular cell borders. Atomic force microscopy revealed that both increased binding strength of desmoglein-3 molecules and amount of desmoglein-3 oligomers, known hallmarks of hyperadhesion, were reduced in K17- compared to K14-expressing cells. Importantly, overexpression of Dsg3 or DPII enhanced their localization at intercellular cell borders and increased the formation of Dsg3 oligomers, resulting in stable, hyperadhesive desmosomes despite the presence of K17. Notably, PKP1 was enriched in these desmosomes. Quantitative image analysis revealed that DPII overexpression contributed to desmosome hyperadhesion by increasing the abundance of K5/K17-positive keratin filaments in the proximity of desmosomes enriched in desmoglein-3. Thus, our data show that hyperadhesion can result from recruitment of keratin isotypes K5/K17 to desmosomes or from enhanced expression of DP and Dsg3 irrespective of keratin composition. The notion that hyperadhesive desmosomes failed to form in the absence of keratins underscores the essential role of keratins and suggest bidirectional control mechanisms at several levels.
Topics: Cell Adhesion; Cytoskeleton; Desmogleins; Desmosomes; Keratinocytes; Keratins
PubMed: 35380280
DOI: 10.1007/s00018-022-04244-y -
Experimental Cell Research Jun 2007Epidermal keratins, a diverse group of structural proteins, form intermediate filament networks responsible for the structural integrity of keratinocytes. The networks... (Review)
Review
Epidermal keratins, a diverse group of structural proteins, form intermediate filament networks responsible for the structural integrity of keratinocytes. The networks extend from the nucleus of the epidermal cells to the plasma membrane where the keratins attach to linker proteins which are part of desmosomal and hemidesmosomal attachment complexes. The expression of specific keratin genes is regulated by differentiation of the epidermal cells within the stratifying squamous epithelium. Progress in molecular characterization of the epidermal keratins and their linker proteins has formed the basis to identify mutations which are associated with distinct cutaneous manifestations in patients with genodermatoses. The precise phenotype of each disease apparently reflects the spatial level of expression of the mutated genes, as well as the types and positions of the mutations and their consequences at mRNA and protein levels. Identification of specific mutations in keratinization disorders has provided the basis for improved diagnosis and subclassification with prognostic implications and has formed the platform for prenatal testing and preimplantation genetic diagnosis. Finally, precise knowledge of the mutations is a prerequisite for development of gene therapy approaches to counteract, and potentially cure, these often devastating and currently intractable diseases.
Topics: Animals; DNA Mutational Analysis; Desmosomes; Epidermis; Gene Expression Regulation; Humans; Intermediate Filaments; Keratinocytes; Keratins; Mutation; Skin Diseases
PubMed: 17531221
DOI: 10.1016/j.yexcr.2007.03.029 -
The Journal of Cell Biology Apr 2003Plakophilin 3 (PKP3) is a recently described armadillo protein of the desmosomal plaque, which is synthesized in simple and stratified epithelia. We investigated the...
Plakophilin 3 (PKP3) is a recently described armadillo protein of the desmosomal plaque, which is synthesized in simple and stratified epithelia. We investigated the localization pattern of endogenous and exogenous PKP3 and fragments thereof. The desmosomal binding properties of PKP3 were determined using yeast two-hybrid, coimmunoprecipitation and colocalization experiments. To this end, novel mouse anti-PKP3 mAbs were generated. We found that PKP3 binds all three desmogleins, desmocollin (Dsc) 3a and -3b, and possibly also Dsc1a and -2a. As such, this is the first protein interaction ever observed with a Dsc-b isoform. Moreover, we determined that PKP3 interacts with plakoglobin, desmoplakin (DP) and the epithelial keratin 18. Evidence was found for the presence of at least two DP-PKP3 interaction sites. This finding might explain how lateral DP-PKP interactions are established in the upper layers of stratified epithelia, increasing the size of the desmosome and the number of anchoring points available for keratins. Together, these results show that PKP3, whose epithelial and epidermal desmosomal expression pattern and protein interaction repertoire are broader than those of PKP1 and -2, is a unique multiprotein binding element in the basic architecture of a vast majority of epithelial desmosomes.
Topics: Animals; Cell Adhesion; Cell Adhesion Molecules; Cell Membrane; Cytoskeletal Proteins; Desmocollins; Desmogleins; Desmoplakins; Desmosomes; Epithelial Cells; Fluorescent Antibody Technique; Humans; Keratins; Membrane Glycoproteins; Mice; Mice, Inbred C57BL; Molecular Sequence Data; Plakophilins; Protein Isoforms; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Tumor Cells, Cultured; Two-Hybrid System Techniques; gamma Catenin
PubMed: 12707304
DOI: 10.1083/jcb.200303036 -
Frontiers in Immunology 2022Desmosomes are important epidermal adhesion units and signalling hubs, which play an important role in pemphigus pathogenesis. Different expression patterns of the...
Desmosomes are important epidermal adhesion units and signalling hubs, which play an important role in pemphigus pathogenesis. Different expression patterns of the pemphigus autoantigens desmoglein (Dsg)1 and Dsg3 across different epidermal layers have been demonstrated. However, little is known about changes in desmosome composition in different epidermal layers or in patient skin. The aim of this study was thus to characterize desmosome composition in healthy and pemphigus skin using super-resolution microscopy. An increasing Dsg1/Dsg3 ratio from lower basal (BL) to uppermost granular layer (GL) was observed. Within BL desmosomes, Dsg1 and Dsg3 were more homogeneously distributed whereas superficial desmosomes mostly comprised one of the two molecules or domains containing either one but not both. Extradesmosomal, desmoplakin (Dp)-independent, co-localization of Dsg3 with plakoglobin (Pg) was found mostly in BL and extradesmosomal Dsg1 co-localization with Pg in all layers. In contrast, in the spinous layer (SL) most Dsg1 and Dsg3 staining was confined to desmosomes, as revealed by the co-localization with Dp. In pemphigus patient skin, Dsg1 and Dsg3 immunostaining was altered especially along blister edges. The number of desmosomes in patient skin was reduced significantly in basal and spinous layer keratinocytes with only few split desmosomes found. In addition, Dsg1-Pg co-localization at the apical BL and Dsg3-Pg co-localization in SL were significantly reduced in patients, suggesting that that extradesmosomal Dsg molecules were affected. These results support the hypothesis that pemphigus is a desmosome assembly disease and may help to explain histopathologic differences between pemphigus phenotypes.
Topics: Desmoglein 1; Desmoglein 3; Desmosomes; Epidermis; Humans; Pemphigus; Skin
PubMed: 35711465
DOI: 10.3389/fimmu.2022.884241 -
International Journal of Molecular... Aug 2019Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disease characterized by sudden death in young people and featured by fibro-adipose myocardium replacement,... (Review)
Review
Arrhythmogenic cardiomyopathy (ACM) is an inherited heart disease characterized by sudden death in young people and featured by fibro-adipose myocardium replacement, malignant arrhythmias, and heart failure. To date, no etiological therapies are available. Mutations in desmosomal genes cause abnormal mechanical coupling, trigger pro-apoptotic signaling pathways, and induce fibro-adipose replacement. Here, we discuss the hypothesis that the ACM causative mechanism involves a defect in the expression and/or activity of the cardiac Ca handling machinery, focusing on the available data supporting this hypothesis. The Ca toolkit is heavily remodeled in cardiomyocytes derived from a mouse model of ACM defective of the desmosomal protein plakophilin-2. Furthermore, ACM-related mutations were found in genes encoding for proteins involved in excitation‒contraction coupling, e.g., type 2 ryanodine receptor and phospholamban. As a consequence, the sarcoplasmic reticulum becomes more eager to release Ca, thereby inducing delayed afterdepolarizations and impairing cardiac contractility. These data are supported by preliminary observations from patient induced pluripotent stem-cell-derived cardiomyocytes. Assessing the involvement of Ca signaling in the pathogenesis of ACM could be beneficial in the treatment of this life-threatening disease.
Topics: Animals; Arrhythmias, Cardiac; Calcium; Calcium Signaling; Cardiomyopathies; Desmosomes; Humans; Myocytes, Cardiac; Plakophilins; Ryanodine Receptor Calcium Release Channel
PubMed: 31426283
DOI: 10.3390/ijms20163986 -
Proceedings of the National Academy of... Nov 2020Desmosomes are cell-cell junctions that link tissue cells experiencing intense mechanical stress. Although the structure of the desmosomal cadherins is known, the...
Desmosomes are cell-cell junctions that link tissue cells experiencing intense mechanical stress. Although the structure of the desmosomal cadherins is known, the desmosome architecture-which is essential for mediating numerous functions-remains elusive. Here, we recorded cryo-electron tomograms (cryo-ET) in which individual cadherins can be discerned; they appear variable in shape, spacing, and tilt with respect to the membrane. The resulting sub-tomogram average reaches a resolution of ∼26 Å, limited by the inherent flexibility of desmosomes. To address this challenge typical of dynamic biological assemblies, we combine sub-tomogram averaging with atomistic molecular dynamics (MD) simulations. We generate models of possible cadherin arrangements and perform an in silico screening according to biophysical and structural properties extracted from MD simulation trajectories. We find a truss-like arrangement of cadherins that resembles the characteristic footprint seen in the electron micrograph. The resulting model of the desmosomal architecture explains their unique biophysical properties and strength.
Topics: Cadherins; Desmosomes; Electron Microscope Tomography; Humans; Intercellular Junctions; Molecular Dynamics Simulation
PubMed: 33067392
DOI: 10.1073/pnas.2004563117 -
Trends in Cardiovascular Medicine Jul 2014Mutations in proteins of the desmosome are associated with arrhythmogenic cardiomyopathy (AC; also referred to as "ARVC" or "ARVD"). Life-threatening ventricular... (Review)
Review
Mutations in proteins of the desmosome are associated with arrhythmogenic cardiomyopathy (AC; also referred to as "ARVC" or "ARVD"). Life-threatening ventricular arrhythmias often occur in the concealed phase of the disease before the onset of structural changes. Among the various potential mechanisms for arrhythmogenesis in AC, in this article, we concentrate on the relation between desmosomes and sodium channel function. We review evidence indicating that (1) loss of desmosomal integrity (including mutations or loss of expression of plakophilin-2; PKP2) leads to reduced sodium current (INa), (2) the PKP2-INa relation could be partly consequent to the fact that PKP2 facilitates proper trafficking of proteins to the intercalated disc, and (3) PKP2 mutations can be present in patients diagnosed with Brugada syndrome (BrS), thus supporting the previously proposed notion that AC and BrS are not two completely separate entities, but "bookends" in a continuum of variable sodium current deficiency and structural disease.
Topics: Action Potentials; Animals; Arrhythmogenic Right Ventricular Dysplasia; Brugada Syndrome; Desmosomes; Genetic Predisposition to Disease; Heart Rate; Humans; Mutation; Phenotype; Plakophilins; Protein Transport; Sodium Channels
PubMed: 24656989
DOI: 10.1016/j.tcm.2014.02.001 -
Journal of Cell Science May 2014Adhesion between cells is established by the formation of specialized intercellular junctional complexes, such as desmosomes. Desmosomes contain isoforms of two members...
Adhesion between cells is established by the formation of specialized intercellular junctional complexes, such as desmosomes. Desmosomes contain isoforms of two members of the cadherin superfamily of cell adhesion proteins, desmocollins (Dsc) and desmogleins (Dsg), but their combinatorial roles in desmosome assembly are not understood. To uncouple desmosome assembly from other cell-cell adhesion complexes, we used micro-patterned substrates of Dsc2aFc and/or Dsg2Fc and collagen IV; we show that Dsc2aFc, but not Dsg2Fc, was necessary and sufficient to recruit desmosome-specific desmoplakin into desmosome puncta and produce strong adhesive binding. Single-molecule force spectroscopy showed that monomeric Dsc2a, but not Dsg2, formed Ca(2+)-dependent homophilic bonds, and that Dsg2 formed Ca(2+)-independent heterophilic bonds with Dsc2a. A W2A mutation in Dsc2a inhibited Ca(2+)-dependent homophilic binding, similar to classical cadherins, and Dsc2aW2A, but not Dsg2W2A, was excluded from desmosomes in MDCK cells. These results indicate that Dsc2a, but not Dsg2, is required for desmosome assembly through homophilic Ca(2+)- and W2-dependent binding, and that Dsg2 might be involved later in regulating a switch to Ca(2+)-independent adhesion in mature desmosomes.
Topics: Animals; Cadherins; Cell Adhesion; Cell Adhesion Molecules; Desmogleins; Desmosomes; Dogs; HEK293 Cells; Humans; Madin Darby Canine Kidney Cells; Spectrum Analysis
PubMed: 24610950
DOI: 10.1242/jcs.146316 -
Cell Adhesion & Migration 2008Desmosomes are intercellular junctions responsible for strong cell-cell adhesion in epithelia and cardiac muscle. Numerous studies have shown that the other major type...
Desmosomes are intercellular junctions responsible for strong cell-cell adhesion in epithelia and cardiac muscle. Numerous studies have shown that the other major type of epithelial cell adhesion, the adherens junction, is destabilized by src-induced tyrosine phosphorylation of two of its principal components, E-cadherin and beta-catenin. Here we show that treatment of epithelial cells with the potent tyrosine phosphatase inhibitor sodium pervanadate causes tyrosine phosphorylation of the major desmosomal components desmoglein 2 and plakoglobin in both the non-ionic detergent soluble and insoluble cell fractions and, surprisingly, stabilizes desmosomal adhesion, inducing the hyper-adhesive form normally found in tissues and confluent cell sheets. Taken together with the few other studies on desmosomes these results suggest that the effects of tyrosine phosphorylation on desmosomal adhesion are complex.
Topics: Animals; Cell Line; Desmosomes; Dogs; Phosphotyrosine; Vanadates
PubMed: 19262118
DOI: 10.4161/cam.2.3.6549