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Gastrointestinal System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Coupling between ICC and smooth muscle networks is essential for the entrainment of ECA to obtain coordinated muscle contraction. Gap junctions play an important role in intercellular communication since they provide direct electrical and metabolic coupling between the cytoplasm of neighboring cells (Chanson and Spray, 1995), but cells are also coupled by a variety of other structures (Daniel et al., 1976; Huizinga et al., 1992). ICC may be coupled to the smooth muscle by gap junctions as found at the inner border of the circular muscle layer in the canine colon (Berezin et al., 1988), but at other sites, such as between ICC and the muscle layers of the mouse small intestine, gap junctions were not found; however, there was an abundance of close apposition junctions (uneberg, 1982). Within certain muscle layers, no gap junctions can be recognized by electron microscopic techniques such as in the longitudinal muscle of the intestine and colon of a variety of species (Zamir and Hanani, 1990; Liu et al., 1998). In such tissues, close apposition junctions are always observed. Such contacts may contain small groups of connexons, which would allow electrical and metabolic communication although it could not be identi-ed as a gap junction; only a large aggregate of connexons can be recognized as a gap junction by electron microscopy. Nevertheless, electrical communication other than purely resistive is likely to occur.
Cell–Cell Communications through Gap Junctions and Cancer in 3D Systems
Published in Karen J.L. Burg, Didier Dréau, Timothy Burg, Engineering 3D Tissue Test Systems, 2017
Stephanie Nicole Shishido, Thu Annelise Nguyen
Adjacent cells may be connected to each other through tight junction, desmosomes, gap junctions, and adherens to facilitate passage of signaling molecules from cell to cell (Dréau 2010). Tight junctions, or zonula occludens, form a virtually impermeable barrier to fluid between closely associated cells by joining the membranes together. These are typically more apically located. Desmosomes, or macula adherens, support cell–cell adhesion by attaching to intermediate filaments of keratin in the cytosol. Adherens, or zonula adherens, form strong mechanical attachments by forming a bridge connecting the actin cytoskeleton of neighboring cells. These protein complexes are composed of cadherins and catenins, and are usually more basally located. Gap junctions form direct intracellular connections between adjacent cells allowing for intercellular communication via the transfer of low molecular weight molecules.
Centralized Endothelial Mechanobiology, Endothelial Dysfunction, and Atherosclerosis
Published in Jiro Nagatomi, Eno Essien Ebong, Mechanobiology Handbook, 2018
Ian Chandler Harding, Eno Essien Ebong
Cell-to-cell junctions are prime examples of decentralized mechanotransduction structures. They contain a variety of multiprotein complexes that are used to maintain contact between neighboring cells and to support physiological functions such as paracellular permeability and cell-to-cell communication. The major complexes at cell-to-cell junctions are adherens junctions, tight junctions, and gap junctions. Adherens junctions are protein complexes that create extracellular bridges between neighboring cells, initiate and stabilize cell-to-cell contact, and affect cellular processes such as intracellular signaling and transcriptional regulation [153]. Adherens junctions are formed by the transmembrane protein vascular endothelial cadherin (VE-cadherin) (Figure 7.4), which is then attached to the actin cytoskeleton through a series of catenin family proteins [154]. Another cell-to-cell junction, tight junctions, help regulate paracellular permeability. They are mainly composed of two transmembrane proteins, occludins and claudins, which are similarly linked to the actin cytoskeleton by linker proteins, mainly the zonula occludens (ZO) proteins 1, 2, and 3 (ZO-1, ZO-2, and ZO-3) [153]. Lastly, gap junctions are intercellular channels created by proteins called connexins [155]. These proteins allow for the diffusion of ions and small molecules, thereby allowing cellular communication [155]. Additionally, the aforementioned junctions and proteins are accompanied by other junctional proteins such as platelet endothelial cell adhesion molecule-1 (PECAM-1), which can both bridge ECs and serve as an anchor for circulating platelets and blood cells.
Intra-carotid body inter-cellular communication
Published in Journal of the Royal Society of New Zealand, 2023
Liam P. Argent, Aabharika Bose, Julian F. R. Paton
Gap junctions are formed by the binding of a pair of connexons on apposed cell membranes and enable the direct exchange of information, in the form of signalling molecules, between two coupled cells. The diameter of the gap junction pore is estimated to be around 1.5nm (Weber et al. 2004), which is large enough to permit the passage of molecules up to 1KDa in size (Weber et al. 2004). The presence of functional gap junctions in the carotid body has been demonstrated using dye and current transfer experiments (Jiang and Eyzaguirre 2003, 2006) (Figure 1). Further, both connexin 43 (Cx43) (Abudara et al. 1999), the canonical glial connexin, and connexin 36 (Cx36) (Frinchi et al. 2013), the classical neuronal connexin, are expressed in the carotid body. The spatial distribution of reported immunohistochemistry staining patterns suggests glomus cells express both (Abudara et al. 1999; Frinchi et al. 2013), although further work is needed to confirm this. Petrosal ganglion neuron projections are another possibility. Importantly, homomer connexons formed of Cx36 are incompatible with homomer connexons formed of Cx43, meaning Cx36 / 43 heteromer gap junctions never assemble and so cannot couple cells. Homotypic Cx43 and Cx36 gap junctions are both possible.
Targeting gap junctional intercellular communication by hepatocarcinogenic compounds
Published in Journal of Toxicology and Environmental Health, Part B, 2020
Kaat Leroy, Alanah Pieters, Andrés Tabernilla, Axelle Cooreman, Raf Van Campenhout, Bruno Cogliati, Mathieu Vinken
Gap junctions are a group of cell-to-cell contacts composed of 2 hemichannels of adjacent cells, which in turn are built up by 6 connexin (Cx) proteins (Figure 1) (Cooreman et al. 2019). Thus far, more than 21 human connexin family members were identified, all that are expressed in a cell type-specific manner (Cooreman et al. 2019; Tachikawa et al. 2020). In liver, hepatocytes abundantly produce Cx32 and to a lesser extent Cx26, whereas non-parenchymal hepatic cell populations, including Kupffer cells, endothelial cells and stellate cells, mainly express Cx43 (Berthoud et al. 1992; Fischer et al. 2005; Greenwel et al. 1993; Saez 1997). Cx32 is uniformly produced by hepatocytes, while Cx26 is preferentially expressed in the periportal acinar area (Rosenberg, Spray, and Reid 1992). All connexin proteins are named after their respective molecular weight and share the same topology consisting of 4 transmembrane regions, 2 extracellular loops, 1 cytoplasmic loop and an intracellular C-terminus and N-terminus. Approximately 3% of the membrane surface of hepatocytes is covered with gap junctions, which are organized in plaques. A gap junction typically measures 180Å in length and 15Å in diameter, enabling passive diffusion of small and hydrophilic molecules, such as glutamate, glucose, inositol trisphosphate, glutathione, adenosine trisphosphate and cyclic adenosine monophosphate (cAMP), as well as ions, including calcium, potassium and sodium (Vinken et al. 2008b). Thus, gap junctions control all facets of the cellular life cycle ranging from cell growth to cell death (Vinken et al. 2006).
The impact of radicals in cold atmospheric plasma on the structural modification of gap junction: a reactive molecular dynamics study
Published in International Journal of Smart and Nano Materials, 2019
Rong-Guang Xu, Zhitong Chen, Michael Keidar, Yongsheng Leng
Gap junctions are specialized intercellular communication channels between neighboring cells with an apparent separation gap of 2–4 nm, which permit the exchange of various ions and small molecules through a regulated gate. A schematic picture of gap junction and connexins are shown in Figure 1. Each gap junction is composed of two apposed hemichannels termed as connexons contributed by each cell. Individual connexon is made up of six protein subunits called connexins (Cx) monomers formed from a family of 21 human proteins. The structure of connexin 26 (Cx26 – a typical connexin in humans) with molecular configuration can be obtained from protein data bank (accession no. 2Zw3) as shown in Figure 2. Connexin is a transmembrane protein with four transmembrane domains (TM1 to TM4). They are connected by two extracellular loops (EL-1 and EL-2) and one cytoplasmic loop (CL). Each connexin contains amino (NT) and carboxyl (CT) terminus in the cytoplasm.