Epithelial sodium channel
| Epithelial sodium channel | ||
|---|---|---|
|
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| Schematic representation of an ENaC. | ||
| Mass / length primary structure | 1958 = 669 + 640 + 649 amino acids | |
| Secondary to quaternary structure | α + β + γ; multipass membrane protein | |
| Isoforms | 5α; 2β; 1γ | |
| Identifier | ||
| Gene name (s) | SCNN1A , SCNN1B , SCNN1G , SCNN1D | |
| Transporter classification | ||
| TCDB | 1.A.6.1.1 | |
| designation | ENaC family | |
The epithelial sodium channel (short: ENaC from English : epithelial Na channel; also SCNN1 from English: sodium channel non-neuronal 1 or ASSC from English: amiloride sensitive sodium channel) is a membrane-based ion channel that, in addition to Li + ions and Protons are especially permeable to Na + ions . In the basic state it is open, one speaks of a constitutively active channel.
The epithelial sodium channel is composed of three subunits (α, β, γ), which are probably built into a heterotrimer. Each of the three subunits has two transmembrane helices and an extracellular loop. The amino and carboxy termini of the polypeptide chains are each located in the cytosol. Mutations in the genes that code for the ENaC subunits can cause pseudohypoaldosteronism type 1 (α, β) and Liddle syndrome (β, γ).
Until recently it was assumed that ENaC is a heterotetramer, but the structure elucidation of the “acid-sensing ion channel 1” (ASIC1) gave cause to question this assumption. The elucidation of this related ion channel had shown that it is structured as a heterotrimer.
ENaC is located in the apical membranes of polar epithelial cells , especially in the kidneys , the lungs and the colon (colon). It is involved in the transepithelial transport of Na + ions, which it brings about together with the Na + / K + -ATPase. It plays an important role in maintaining Na + and K + concentrations in blood, epithelia and extraepithelial fluids by reabsorbing Na + ions from primary urine and intestinal lumen. The ENaC activity and expression in kidney and colon is in this case by the mineralogical corticosteroid aldosterone modulated. ENaC can be blocked by amiloride . This property is used in medicine by using amiloride as a diuretic .
ENaC is also found in taste cells . Here it plays an important role in the perception of the salty taste. While in rodents almost the entire salty taste is conveyed by ENaC, in humans only about a fifth of the perception can be attributed to ENaC.
There is another so-called δ-subunit which has great homology to the α-subunit and can replace it with the formation of a functional channel. Such δ, β, γ-tetramers occur, for example, in the pancreas , testes or ovaries , but their function is still unclear.
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- ↑ Hanukoglu I, Hanukoglu A: Epithelial sodium channel (ENaC) family: Phylogeny, structure-function, tissue distribution, and associated inherited diseases. . In: Genes . 579, No. 2, January 2016, pp. 95-132. doi : 10.1016 / j.gene.2015.12.061 . PMID 26772908 . PMC 4756657 (free full text).
- ↑ UniProt P37188 , UniProt P51168 , UniProt P51170
- ↑ Jasti J, Furukawa H, Gonzales EB, Gouaux E: Structure of acid-sensing ion channel 1 at 1.9 Å resolution and low pH . In: Nature . 449, 2007, pp. 316-322. doi : 10.1038 / nature06163 .
- ↑ Enuka Y, Hanukoglu I, Edelheit O, Vaknine H, Hanukoglu A: Epithelial sodium channels (ENaC) are uniformly distributed on motile cilia in the oviduct and the respiratory airways . In: Histochemistry and Cell Biology . 137, No. 3, March 2012, pp. 339-353. doi : 10.1007 / s00418-011-0904-1 . PMID 22207244 .