Structure and function of skin
Roger L. McMullen in Antioxidants and the Skin, 2018
Desmosomes are disc-shape structures that are located on the outside surface of the cell where they serve as cellular junctions that provide a link between adjacent keratinocyte cells. They are connected to the intermediate filaments within the cell and are primarily composed of proteins that come from three different gene families: cadherins, armadillo proteins, and plakins. Molecules from these families are joined together and are located at the surface of the cell (at the cell membrane) and extend to the interior of the cell, where they anchor to intermediate filaments. Inside the cell, intermediate filaments are connected to the plakins. The plakins, located closer to the cell membrane than the intermediate filaments, are connected to proteins from the armadillo family. The cadherins are transmembrane proteins—they cross the cell membrane and are connected to an armadillo protein at its host cell and to another cadherin molecule at a neighboring keratinocyte. Thus, the junction point between two cells begins with the binding of two cadherin proteins and extends into the cytoplasm of each cell, ultimately connecting to intermediate filaments.10
The Ultrastructure And Pathobiology Of Urinary Bladder Cancer
George T. Bryan, Samuel M. Cohen in The Pathology of Bladder Cancer, 2017
Historically, desmosomes were the first class of cell junctions to be implicated in strong cell-to-cell adhesion.82,103,106 This led to their designation as adherens junctions.123 In all likelihood, all categories of cell junctions are sites of strong intercellular adhesion.82,106 The absolute contribution of each type of cell junction (i.e., occludens, adherens, gap, etc.) to adhesion is technically difficult to measure, especially since several types of junctions are present at the surfaces of most kinds of epithelial cells. Further, the contribution of specific nonjunctional plasma membrane components to cell adhesion under physiological conditions is a matter for speculation at the present time. Ultrastructural observations provide some evidence that the plasma membrane of neighboring epithelial cells are adherent at nonjunctional sites as well as at cell junctions, since the width of the extracellular space tends to remain constant in various physiological states, such as contraction and dilatation of the bladder. On the other hand, cells in epithelia are easily separated by relatively mild perturbations, at nonjunctional sites, but not at cell junctions, indicating that the nonjunctional plasma membranes of neighboring cells are weakly interadherent, at least under artificial conditions.106
Lung Defenses
Sunit K. Singh in Human Respiratory Viral Infections, 2014
Epithelials provide a mucosal barrier and contribute to the mucociliary clearance function already mentioned. Lining the luminal surface of the airways, they are attached to neighboring cells by several structures: tight junctions, intermediate junctions, gap junctions, and desmosomes.9 These structures form a barrier between the luminal space and the pulmonary parenchyma. Desmosomes mediate mechanical adhesion of cells to their neighbors and tight junctions completely obliterate the intercellular spaces just below the luminal surface.10 Transport through gap junctions may be a means for the cells to provide their neighbors with defense molecules, such as antioxidants.11 This organization of epithelial cells creates an effective mechanical barrier and allows for polarity in function, thus, maintaining an ionic gradient for bidirectional secretion of many substances.
AMPK in regulation of apical junctions and barrier function of intestinal epithelium
Published in Tissue Barriers, 2018
Mei-Jun Zhu, Xiaofei Sun, Min Du
Epithelial cells are joined by a series of intercellular junctions and polarized into the apical and the basolateral domains.30,31 The apical domain of epithelial cells is linked with adjacent epithelial cells through TJs and AJs, which are also referred to as apical junctions (Fig. 1). The assembly of apical junctions is indispensable for the formation and maintenance of epithelial barrier integrity.1,32 Desmosomes are intercellular junctions located below AJs on the lateral membrane and link to intermediate filaments to stabilize the epithelial layer and provide mechanical strength to tissues.33,34 On the basolateral membrane, hemidesmosomes connect to intermediate filament and facilitate epithelial cell adhesion to extracellular matrix in the basal lamina.35 In addition, epithelial cells communicate with surrounding cells through gap junctions (Fig. 1) that are composed of connexins and assembled into hexameric pore-forming channels.36
Epithelial maturity influences EPEC-induced desmosomal alterations
Published in Gut Microbes, 2019
Jennifer Lising Roxas, Gayatri Vedantam, V.K. Viswanathan
Desmosomes are protein complexes comprised of desmosomal cadherins, armadillo proteins and plakins, which are stabilized at paracellular junctions by the tethering of intermediate filaments (IF).1 Desmosomes connect the walls of adjacent host cells at multiple discrete regions forming “spot-welds” that provide tensile strength to the cell layer. Much of our current understanding of the formation and maintenance of desmosomes is based on studies on the epidermis and on cardiomyocytes. However, desmosomal plaque composition, as well as spatial organization of cells held together by desmosomes, differ in various tissue types (Figure 1).2–6 In contrast to the stratified epithelial cells of the skin and the branched myocytes of the heart, a single layer of simple columnar epithelial cells blankets the intestinal mucosa. Moreover, while all desmosomal cadherin isoforms are expressed in the skin albeit in different combinations and abundances through the epidermal layers, only desmoglein-2 (DSG2) and desmocolin-2 (DSC2) are found in normal intestinal epithelium and in cardiac muscles.1,5
Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties
Published in Tissue Barriers, 2018
Lisa Bierbaumer, Uwe Yacine Schwarze, Reinhard Gruber, Winfried Neuhaus
A list of immortalized cell lines that have been established from different compartments of the oral mucosa and their primary applications are given in Table 2. Analysis of monocultures revealed that immortalized keratinocytes can show functional characteristics of the epithelial barrier. Gröger et al. established immortalized human gingival keratinocyte cell lines with cytokeratin expression patterns comparable to that of primary gingival keratinocytes. Cells formed multi-layered structures, were able to develop TEER and showed expression of claudin-1, claudin-2 and occludin.254–256 One of those cell lines, namely Gie-No3B11, was used to study the influence of retinoic acid (RA) on human gingival epithelial barriers, showing increased TEER, increased claudin-4 and occludin expression, while ZO-1 was downregulated by RA treatment.256 The effect of RA on cell junctions of the gingival epithelium was also studied using the immortalized gingival cell line GE1, which was established from transgenic mice harboring a temperature-sensitive SV40T gene.257 GE1 cells form multilayered structures that are connected by desmosomes.257 Studies by Hatakeyama et al. revealed that RA treatment a) altered TJ expression of claudin-1, claudin-4, occludin and ZO-1258; b) decreased the expression of connexin gap junction Cx31.1259 and c) induced downregulation of desmosomes and loss of hemidesmosomes.260
Related Knowledge Centers
- Bladder
- Cadherin
- Cell Adhesion
- Cell Junction
- Desmoglein
- Epithelium
- Cell Membrane
- Cardiac Muscle
- Cell
- Gastrointestinal Wall