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Gap junction
Cell-cell junction composed of innexins or connexins / From Wikipedia, the free encyclopedia
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Gap junctions are membrane channels between cells that allow the exchange of substances from the cytoplasm of one cell directly to the cytoplasm of an adjacent cell.[1] Substances exchanged include small molecules, substrates, and metabolites.[1]
![]() | This article's tone or style may not reflect the encyclopedic tone used on Wikipedia. (April 2024) |
Gap junction | |
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![]() Vertebrate gap junction | |
Identifiers | |
MeSH | D017629 |
TH | H1.00.01.1.02024 |
FMA | 67423 |
Anatomical terminology |
Gap junctions were first described as close appositions as other tight junctions, but following electron microscopy studies in 1967, they were renamed gap junctions to distinguish them from tight junctions.[2] The 2-4 nm gap that they bridge between cell membranes was noted.[3]
Gap junctions use protein complexes known as connexons to connect one cell to another. The proteins are called connexins. Gap junction proteins include the more than 26 types of connexin, and at least 12 non-connexin components that make up the gap junction complex or nexus.[4] These components include the tight junction protein 1 which holds the membranes together,[5] sodium channels,[6] and aquaporin.[7][8]
More gap junction proteins have become known due to the development of next-generation sequencing. Connexins were found to be structurally homologous between vertebrates and invertebrates but different in sequence.[9] As a result, the term innexin is used to differentiate invertebrate connexins.[10] There are more than 20 known innexins,[11] along with unnexins in parasites and vinnexins in viruses.
An electrical synapse is a gap junction that can transmit action potentials between neurons. Connexon pairs act as generalized regulated gates for ions and smaller molecules between cells. Hemichannel connexons form channels to the extracellular environment.[12][13][14][15]
A gap junction or macula communicans is different from an ephaptic coupling that involves electrical signals external to the cells.[16][17]