| SLC5A7 | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Aliases | SLC5A7, CHT, CHT1, HMN7A, hCHT, Choline transporter, solute carrier family 5 member 7, CMS20 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM:608761;MGI:1927126;HomoloGene:32516;GeneCards:SLC5A7;OMA:SLC5A7 - orthologs | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Thehigh-affinity choline transporter (ChT) also known assolute carrier family 5 member 7 is aprotein in humans that is encoded by theSLC5A7gene.[5] It is acell membranetransporter and carriescholine intoacetylcholine-synthesizingneurons.
Hemicholinium-3 is aninhibitor of the ChT and can be used to depleteacetylcholine stores, whilecoluracetam is anenhancer of the ChT and can increasecholinergicneurotransmission by enhancing acetylcholinesynthesis.
Choline is a direct precursor of acetylcholine (ACh), a neurotransmitter of the central and peripheral nervous system that regulates a variety of autonomic, cognitive, and motor functions. SLC5A7 is aNa(+)- and Cl(-)- dependent high-affinity transporter that mediates the uptake of choline for acetylcholine synthesis in cholinergic neurons.[5][6]
Mutations in theSLC5A7 gene have been associated withDistal spinal muscular atrophy with vocal cord paralysis (distal hereditary motor neuropathy type 7A).[7]
The ChT seems to be a site of action of some β-neurotoxins found insnake venoms, which disrupt peripheral cholinergic transmission by interfering with presynaptic acetylcholine synthesis. It is hypothesized that these toxins irreversibly block the ChT.[8][9]
Choline is a necessary reagent for the synthesis ofacetylcholine in the central nervous system. Neurons get their choline by specific protein transporters known as choline transporters. In the human brain microvascularendothelial cells, two systems initiate the choline absorption. The first system is known as the Choline transporter-like protein 1, or CTL1. The second system is the Choline transporter-like protein 2, or CTL2. Those two systems are found on the plasma membrane of the brain microvascular endothelial cells. They are also found on the mitochondrial membrane. CTL2 was found to be highly expressed on themitochondria. Meanwhile, CTL1 was mostly found on the plasma membrane of those microvascular cells.[10]
CTL2 is the main protein involved in the absorption of choline into the mitochondria for its oxidation, and CTL1 is the main protein for the choline uptake from the extracellular medium. CTL1 is a pH dependent protein. The absorption of choline through CTL1 proteins changes with the pH of the extracellular medium. When the pH of the medium is changed from 7.5 to 7.0-5.5, the rate of absorption of choline by CTL1 proteins decreases greatly. The choline uptake does not change upon the alkalinization of the extracellular medium. Moreover, it was found that the choline uptake is also influenced by the electronegativity of the plasma membrane. When the concentration of potassium ions is increased, the membrane becomes depolarized. The choline absorption decreases majorly as a result of the membranedepolarization by the potassium ions. The choline uptake was found to be only affected by the potassium ions. The sodium ions do not affect the affinity of CTL1 and CTL2 to choline.[10]
This article incorporates text from theUnited States National Library of Medicine, which is in thepublic domain.
