Introduction to Cell Biology
Anthony R. Mundy, John M. Fitzpatrick, David E. Neal, Nicholas J. R. George in The Scientific Basis of Urology, 2010
Cells that are structurally bound within a tissue must first disassemble their cell-cell contacts to become motile. Between neighboring cells, a number of junctions exist that facilitate adhesion, communication, and structural support. Adherens junctions are supported by the calcium-regulated binding of the extracellular domain of cadherin molecules of adjacent cells. The expression pattern of cadherins is highly specific for different cell types, for example, epithelial cells express E-cadherin and vascular endothelial cells express VE-cadherin. Cadherin molecules are bound by their cytoplasmic domain to β-catenin and via interactions with a-catenin and other actin-binding molecules; the complex is bridged to the actin cytoskeleton. Tight junctions are portions of plasma membrane between adjacent cells that appear to be fused together at points, providing an impermeable barrier to small hydrophilic molecules and ions. Tight junctions also prevent the diffusion of membrane-bound proteins between the apical and basolateral surface; thus they maintain functional polarity. Gap junctions are small pores between adjacent cells that allow for diffusion of small molecules and ions. Finally, desmosomes comprise specific cadherins known as desmoglein and desmocollin that are bound to intermediate filaments via the cytosolic plakoglobin and desmoplakins, providing mechanical strength. Likewise, intermediate filament bundles secure adhesion to the extracellular matrix through structures called hemidesmosomes.
Endocardial Endothelial Modulation of Myocardial Contraction
Malcolm J. Lewis, Ajay M. Shah in Endothelial Modulation of Cardiac Function, 2020
The EE cells have extensive intercellular overlapping (Figure 1-2) and the intercellular clefts between EE cells are significantly longer than between coronary capillary endothelial cells (Andries, 1994). One or two junctional points, tight junctions, obliterating the intercellular cleft have been seen in rat and cat. Tight junctions act as a selective barrier to small molecules and as a total barrier to large molecules. The tight junction permeability is modulated by the peripheral actin band present in EE cells. Gap junctions, sites of low electrical resistance between adjacent cells, are present between EE cells and are prominent in junctional areas with extensive overlap (Anversa, Giacomeli and Wiener, 1975). The presence of gap junctions suggests electrochemical coupling of EE cells whereby second messengers released by activation of a single EE cell could traverse gap junctions and activate neighbouring EE cells and thus amplify the release of endothelial factors.
Immune function of epithelial cells
Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald in Principles of Mucosal Immunology, 2020
Intercellular junctions between adjacent epithelial cells are of course required for barrier function. Intercellular junctions are located along the lateral surfaces of the epithelial cells. They are composed of the most apically oriented tight junctions, and the subjacent adherens junction and desmosome (Figure 5.2). While the latter are required for physical integrity of the epithelial monolayer, movement across tight junctions is the rate-limiting barrier for solute and particle transport. Tight junctions are physiologically dynamic and regulate the access of small solutes, water, and macromolecules into the paracellular space. Movement across tight junctions can be considered to occur via two routes, the pore pathway and the transcellular pathway. The pore pathway is a high-capacity route that is exquisitely size selective, excluding molecules with Stokes radii greater than ∼5 Å, and are also charge selective. Intestinal tight junctions allow cations to cross via the pore pathway at rates up to 10-fold greater than anions. While this cation selectivity is critical for normal physiologic function and can be reversed to anion selectivity by modifying tight junction protein expression, it is far less than that exhibited by transmembrane ion channels. Nevertheless, the paracellular channels that define the pore pathway are actively gated, i.e., they open and close, in a manner similar to transmembrane ion channels.
The intestinal quorum sensing 3-oxo-C12:2 Acyl homoserine lactone limits cytokine-induced tight junction disruption
Published in Tissue Barriers, 2020
Doriane Aguanno, Garance Coquant, Barbara G. Postal, Céline Osinski, Margaux Wieckowski, Daniel Stockholm, Jean-Pierre Grill, Véronique Carrière, Philippe Seksik, Sophie Thenet
Tight junctions (TJ) seal the paracellular space and thus control the flux of molecules or solutes between adjacent cells. We thus investigated whether TJ reorganization accompanied the effects described above on paracellular permeability. Representative images of immunofluorescence staining (Figure 3a), and quantification of the fluorescence (Figure 3(b,c)), showed that treatment with 3-oxo-C12 AHL alone tended to reduce the signal of both transmembrane proteins occludin (Figure 3(a,b)), −19% vs control) and tricellulin (Figure 3(a,c)), −16% vs control), respectively at bicellular or tricellular cell contacts. On the contrary, in the presence of 3-oxo-C12:2, occludin or tricellulin staining remained similar to control (Figure 3(a,b,c)), confirming an absence of deleterious effect on the barrier function.
Claudin-18.2 as a therapeutic target in cancers: cumulative findings from basic research and clinical trials
Published in Tissue Barriers, 2022
Daisuke Kyuno, Akira Takasawa, Kumi Takasawa, Yusuke Ono, Tomoyuki Aoyama, Kazufumi Magara, Yuna Nakamori, Ichiro Takemasa, Makoto Osanai
Tight junction molecules have intercellular adhesion functions in all cell types. Recently, the dynamics of these proteins in cancer cells have attracted attention. Epithelial cells are held together by several major classes of intracellular junctions, and adherens and tight junctions play essential roles in the development and maintenance of epithelial cells. Tight junctions are typically located on the apical side of epithelial cells, and their components interact with those of neighboring cells. Tight junction proteins are often dysfunctional or altered in various types of cancer cells, and their controlled paracellular permeation and polarity are lost in cancer cells1. Altered tight junction proteins also modulate cytoskeletal elements and signaling molecules bound to these proteins, resulting in the loss of regulated cell migration and proliferation.2
Distribution and translocation of micro- and nanoplastics in fish
Published in Critical Reviews in Toxicology, 2021
Cuizhu Ma, Qiqing Chen, Jiawei Li, Bowen Li, Weiwenhui Liang, Lei Su, Huahong Shi
Previous studies suggest that particles enter the intercellular space, and then translocate into the blood or stay in the tissue intercellular space. In vitro researches indicate that PS short chains (25 monomers) incorporate in the membrane and alter the cell membrane structure and dynamics (Bochicchio et al. 2022). Von Moos et al. (2012) detected particles in the blood lacunae of the gills and in the areas of lamellar tight junctions, where two cells are closely connected. The tight junction is useful to close the gap between adjacent cells and prevent foreign materials from entering tissue through paracellular penetration. These so-called tight junctions are found elsewhere in the circulatory system, intestine epithelial cells, and testis, but they are especially tight in the brain. Researchers design antibodies or antibody fragments that bind to receptors on the endothelial cells to safely penetrate BBB’s defenses and to reach the brain (Shen 2017). Laboratory studies have indicated that NPs (39.4–180 nm) enter brain tissues (Kashiwada 2006; Mattsson et al. 2017; Zhang et al. 2019). Nanoparticles are either negatively charged on the surface, or capable of binding to receptors on the cell surface in order to cross the tissue barriers (Sweeney et al. 2019), but we still do not know how environmental NPs open the tight connections and penetrate the BBB.
Related Knowledge Centers
- Actin
- Cell Junction
- Claudin
- Cytoskeleton
- Epithelium
- Endothelium
- Septate Junction
- Jam2
- Junctional Adhesion Molecule
- Pdz Domain