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Complexity and expression patterns of the desmosomal cadherins.

ABSTRACT: Desmosomes are intercellular junctions that contain two major kinds of transmembrane glycoproteins, desmoglein and desmocollins I and II, involved in cell-cell adhesion. Recent sequence analyses have shown that both desmosomal glycoproteins belong to the larger cadherin family of cell adhesion molecules, in which they represent two different subgroups characterized by their specific sequence and topogenesis. In analyses of cDNA sequences and Northern blot experiments we have now found that both desmoglein and desmocollins are not unique gene products but occur in different subtypes produced from different genes. Comparison of the complete amino acid sequences of type 1 and type 2 desmocollins and of two desmoglein subtypes shows considerable divergence. While the desmoglein genes can be differentially expressed in different cell types, both type 1 and type 2 desmocollins can coexist in the same cells of certain stratified epithelia as shown by in situ hybridization. We conclude that the cadherin composition of desmosomes is much more complex than assumed and can differ in the various epithelia.

SUBMITTER: Koch PJ

PROVIDER: S-EPMC48235 | biostudies-other | 1992 Jan

REPOSITORIES: biostudies-other

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Complexity and expression patterns of the desmosomal cadherins.

Koch P J PJ Goldschmidt M D MD Zimbelmann R R Troyanovsky R R Franke W W WW

Proceedings of the National Academy of Sciences of the United States of America 19920101 1

Desmosomes are intercellular junctions that contain two major kinds of transmembrane glycoproteins, desmoglein and desmocollins I and II, involved in cell-cell adhesion. Recent sequence analyses have shown that both desmosomal glycoproteins belong to the larger cadherin family of cell adhesion molecules, in which they represent two different subgroups characterized by their specific sequence and topogenesis. In analyses of cDNA sequences and Northern blot experiments we have now found that both ...[more]

PMID: 1729705

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Project description:Desmosomes are large, macromolecular protein assemblies that mechanically couple the intermediate filament cytoskeleton to sites of cadherin-mediated cell adhesion, thereby providing structural integrity to tissues that routinely experience large forces. Proper desmosomal adhesion is necessary for the normal development and maintenance of vertebrate tissues, such as epithelia and cardiac muscle, while dysfunction can lead to severe disease of the heart and skin. Therefore, it is important to understand the relationship between desmosomal adhesion and the architecture of the molecules that form the adhesive interface, the desmosomal cadherins (DCs). However, desmosomes are embedded in two plasma membranes and are linked to the cytoskeletal networks of two cells, imposing extreme difficulty on traditional structural studies of DC architecture, which have yielded conflicting results. Consequently, the relationship between DC architecture and adhesive function remains unclear. To overcome these challenges, we utilized excitation-resolved fluorescence polarization microscopy to quantify the orientational order of the extracellular and intracellular domains of three DC isoforms: desmoglein 2, desmocollin 2, and desmoglein 3. We found that DC ectodomains were significantly more ordered than their cytoplasmic counterparts, indicating a drastic difference in DC architecture between opposing sides of the plasma membrane. This difference was conserved among all DCs tested, suggesting that it may be an important feature of desmosomal architecture. Moreover, our findings suggest that the organization of DC ectodomains is predominantly the result of extracellular adhesive interactions. We employed azimuthal orientation mapping to show that DC ectodomains are arranged with rotational symmetry about the membrane normal. Finally, we performed a series of mathematical simulations to test the feasibility of a recently proposed antiparallel arrangement of DC ectodomains, finding that it is supported by our experimental data. Importantly, the strategies employed here have the potential to elucidate molecular mechanisms for diseases that result from defective desmosome architecture.

Project description: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. ?-catenin, a component protein of desmosomes, normally binds directly to desmocollin-2 and desmoglein-2. In this study, we found that CVB3 infection downregulated ?-catenin at the protein level but not the mRNA level in mouse HL-1 cardiomyocytes. We further found that this reduction of ?-catenin protein is a result of ubiquitin proteasome-mediated degradation, since the addition of proteasome inhibitor MG132 inhibited ?-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 ?-catenin from the desmosome into the cytosol, resulting in rapid degradation of ?-catenin. Since ?-catenin shares high sequence homology with ?-catenin in binding the TCF/LEF transcription factor, we further studied the effect of ?-catenin degradation on Wnt/?-catenin signaling. Luciferase assay showed that ?-catenin expression inhibited Wnt/?-catenin signaling. This finding was substantiated by qPCR to show that overexpression of ?-catenin downregulated transcription of Wnt signal target genes, c-myc and MMP9, while silencing ?-catenin upregulated these target genes. Finally, we demonstrated that ?-catenin expression inhibited CVB3 replication. In search for the underlying mechanism, we found that silencing ?-catenin caused down-regulation of interferon-? 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 ?-catenin protein, which in return promotes Wnt/?-catenin signaling and downregulates interferon-? stimulated immune responses.

Dataset Information

Complexity and expression patterns of the desmosomal cadherins.

Publications

Complexity and expression patterns of the desmosomal cadherins.

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