China
Africa
Explore chapters and articles related to this topic
Synapses
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Electrical synapses, as commonly understood, have a direct connection between the cytoplasms of two cells by means of gap junctions consisting of at least several hundreds of channels (Figure 6.18). In vertebrates, these channels are made up of isoforms of the protein connexin having a molecular mass in the range of 26–57 kD, where a protein isoform is one of the different forms of the same protein. Six connexin molecules, not necessarily identical, form a hexameric hemichannel, or connexon, about 5–7.5 nm long and with an external diameter of about 7 nm. A connexon spans across the cell membrane and extends for 1–1.5 nm into the extracellular space. Each connexon has six protrusions, one from each of the connexin molecules, that fit into the depressions between the protrusions of the other connexon of the channel. A channel having a pore of 1.2–2 nm diameter is thus formed, with tight interlocking in the extracellular gap of 2–3.5 nm separating the membranes of the two cells. The tight interlocking is necessary to prevent leakage of ions between the channel and the extracellular space. The two connexons are held together noncovalently by hydrogen, hydrophobic, and ionic bonds between the extracellular loops of the connexin molecules.
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
Gap junctions are protein channels made of the protein connexin (Cx). Connexins have four hydrophobic membrane spanning domains: two conserved, extracellular domains involved in paired hemichannel docking and three cytoplasmic domains (Figure 13.1) (Saez et al. 2003). Intercellular channels are formed through oligomerization of six connexins into a hexameric hemichannel called a connexon, which is trafficked to the plasma membrane. Hemichannels allow communication between cytoplasm and extracellular space. On the membrane, the connexon floats laterally until it docks with a second connexon on the adjacent cell to form an intact gap junction channel. Groups of these channels form gap junctional plaques, allowing the flow of small molecules between the cytosol of neighboring 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.
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.