Gap junctions

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Synonym(s)

Cell Channel; Cell channels; gap junction; macula communicans; membrane protein; Membrane Proteins; Nexus

General information
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Gap Junction are part of the system of cell contacts. Gap junctions (nexus, or macula communicans) consist of an accumulation ("plaques" or "clusters") of channels that run through the cell membranes from cell to cell. Gap junctions thus connect the cytoplasm of adjacent cells directly with each other. The membranes of the cells are fixed at a distance of only 2 to 4 nanometers from each other. Gap junctions, in contrast to tight junctions, leave an electron microscopically detectable gap between them.

The channels of the gap junction are formed by two half channels (Hemichannels, Connexons), of which each cell forms one half. Each connexon generally consists of 6 membrane-spanning proteins (in vertebrates these are formed by the protein family of connexins - also known as membrane proteins). The connexins are arranged in a hexagonal arrangement in such a way that a pore (gap) is left free in their centre.

The function of these cell-cell channels is to exchange signals between neighbouring cells. In this process, ions or small molecules as messenger substances are transported by diffusion directly from one cell into the neighbouring cell. Such messenger substances are e.g. potassium or calcium ions. Furthermore, so-called secondary messengers (second messengers) such as cAMP or cGMP, also metabolites such as glucose. The transfer of these messenger substances can be selective. Some gap junctions also transmit certain substances in only one direction.

Note(s)
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Disorders in the structure of gap junctions are found on the skin in various diseases. This is the case with the "Erythrokeratodermia figurata variabilis".

Literature
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  1. Blaydon DC et al (2014) Defective channels lead to an impaired skin barrier. J Cell Sci 127:4343-4350
  2. Boyden LM et al (2014) Dominant De Novo Mutations in GJA1 Cause Erythrokeratodermia Variabilis Et Progressiva, without Features of Oculodentodigital Dysplasia. J Invest Dermatol. PubMed PMID: 25398053.
  3. Hills CE et al (2014) Mind the gap: connexins and cell-cell communication in the diabetic kidney. Diabetologia. PubMed PMID: 25358446.
  4. Laird DW (2014) Syndromic and non-syndromic disease-linked Cx43 mutations. FEBS Lett 588:1339-1348
  5. Sáez PJ et al (2014) Regulation of hemichannels and gap junction channels by cytokines in antigen-presenting cells. Mediators Inflamm. PubMed PMID:25301274
  6. Sanchez HA et al (2014) Aberrant Cx26 hemichannels and keratitis-ichthyosis-deafness syndrome: insights into syndromic hearing loss. Front Cell Neurosci 8:354. doi: 10.3389/fncel.2014.00354.
  7. Takeuchi H et al (2014) Gap junctions and hemichannels composed of connexins: potential therapeutic targets for neurodegenerative diseases. Front Cell Neurosci PubMed Central PMCID: PMC4151093.
  8. Wang H et al (2014) Exome sequencing reveals mutation in GJA1 as a cause of keratoderma-hypotrichosis-leukonychia totalis syndrome. Hum Mol Genet PubMed PMID: 25168385.

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Last updated on: 29.10.2020