Neurotransmitter sodium symporter

Last updated
Sodium:neurotransmitter symporter family
Identifiers
SymbolSNF
Pfam PF00209
InterPro IPR000175
PROSITE PDOC00533
SCOP2 2a65 / SCOPe / SUPFAM
TCDB 2.A.22
OPM superfamily 64
OPM protein 2a65
Available protein structures:
Pfam   structures / ECOD  
PDB RCSB PDB; PDBe; PDBj
PDBsum structure summary

A neurotransmitter sodium symporter (NSS) (TC# 2.A.22) is type of neurotransmitter transporter that catalyzes the uptake of a variety of neurotransmitters, amino acids, osmolytes and related nitrogenous substances by a solute:Na+ symport mechanism. [1] [2] The NSS family is a member of the APC superfamily. Its constituents have been found in bacteria, archaea and eukaryotes.

Contents

Function

Neurotransmitter transport systems are responsible for the release, re-uptake and recycling of neurotransmitters at synapses. High affinity transport proteins found in the plasma membrane of presynaptic nerve terminals and glial cells are responsible for the removal, from the extracellular space, of released-transmitters, thereby terminating their actions. [3]

The majority of the transporters constitute an extensive family of homologous proteins that derive energy from the co-transport of Na+ and Cl−, in order to transport neurotransmitter molecules into the cell against their concentration gradient.

Neurotransmitter sodium symporters (NSS) are targets for anti-depressants, psychostimulants and other drugs. [4]

Transport reaction

The generalized transport reaction for the members of this family is: [2]

solute (out) + Na+ (out) → solute (in) + Na+ (in).

Structure

The family has a common structure of 12 presumed transmembrane helices and includes carriers for gamma-aminobutyric acid (GABA), noradrenaline/adrenaline, dopamine, serotonin, proline, glycine, choline, betaine, taurine and other small molecules. [2]

NSS carriers are structurally distinct from the second more-restricted family of plasma membrane transporters, which are responsible for excitatory amino acid transport (see TC# 2.A.23). The latter couple glutamate and aspartate uptake to the cotransport of Na+ and the counter-transport of K+, with no apparent dependence on Cl−. [5] In addition, both of these transporter families are distinct from the vesicular neurotransmitter transporters. [6] [7] Sequence analysis of the Na+/Cl− neurotransmitter superfamily reveals that it can be divided into four subfamilies, these being transporters for monoamines, the amino acids proline and glycine, GABA, and a group of orphan transporters. [8]

Tavoulari et al. (2011) described conversion of the Cl− -independent prokaryotic tryptophan transporter TnaT (2.A.22.4.1) to a fully functional Cl− -dependent form by a single point mutation, D268S. Mutations in TnaT-D268S, in wild type TnaT and in a serotonin transporter (SERT; 2.A.22.1.1) provided direct evidence for the involvement of each of the proposed residues in Cl− coordination. In both SERT and TnaT-D268S, Cl− and Na+ mutually increase each other's potency, consistent with electrostatic interaction through adjacent binding sites. [9]

Crystal structures

There are several crystal structures available for a couple members of the NSS family:

Subfamilies

Several characterized proteins are classified within the NSS family and can be found in the Transporter Classification Database.

Human proteins containing this domain

SLC6A1, SLC6A2, SLC6A3, SLC6A4, SLC6A5, SLC6A6, SLC6A7, SLC6A8, SLC6A9, SLC6A11, SLC6A12, SLC6A13, SLC6A14, SLC6A15, SLC6A16, SLC6A17, SLC6A18, SLC6A19, SLC6A20

See also

Related Research Articles

<span class="mw-page-title-main">Reuptake</span> Reabsorption of a neurotransmitter by a neurotransmitter transporter

Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal or glial cell after it has performed its function of transmitting a neural impulse.

<span class="mw-page-title-main">Monoamine transporter</span> Proteins that function as integral plasma-membrane transporters

Monoamine transporters (MATs) are proteins that function as integral plasma-membrane transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are serotonin transporters (SERTs), dopamine transporters (DATs), and norepinephrine transporters (NETs) and are responsible for the reuptake of their associated amine neurotransmitters. MATs are located just outside the synaptic cleft (peri-synaptically), transporting monoamine transmitter overflow from the synaptic cleft back to the cytoplasm of the pre-synaptic neuron. MAT regulation generally occurs through protein phosphorylation and post-translational modification. Due to their significance in neuronal signaling, MATs are commonly associated with drugs used to treat mental disorders as well as recreational drugs. Compounds targeting MATs range from medications such as the wide variety of tricyclic antidepressants, selective serotonin reuptake inhibitors such as fluoxetine (Prozac) to stimulant medications such as methylphenidate (Ritalin) and amphetamine in its many forms and derivatives methamphetamine (Desoxyn) and lisdexamfetamine (Vyvanse). Furthermore, drugs such as MDMA and natural alkaloids such as cocaine exert their effects in part by their interaction with MATs, by blocking the transporters from mopping up dopamine, serotonin, and other neurotransmitters from the synapse.

<span class="mw-page-title-main">Serotonin transporter</span> Mammalian protein found in humans

The serotonin transporter also known as the sodium-dependent serotonin transporter and solute carrier family 6 member 4 is a protein that in humans is encoded by the SLC6A4 gene. SERT is a type of monoamine transporter protein that transports the neurotransmitter serotonin from the synaptic cleft back to the presynaptic neuron, in a process known as serotonin reuptake.

<span class="mw-page-title-main">Uniporter</span>

Uniporters, also known as solute carriers or facilitated transporters, are a type of membrane transport protein that passively transports solutes across a cell membrane. It uses facilitated diffusion for the movement of solutes down their concentration gradient from an area of high concentration to an area of low concentration. Unlike active transport, it does not require energy in the form of ATP to function. Uniporters are specialized to carry one specific ion or molecule and can be categorized as either channels or carriers. Facilitated diffusion may occur through three mechanisms: uniport, symport, or antiport. The difference between each mechanism depends on the direction of transport, in which uniport is the only transport not coupled to the transport of another solute.

<span class="mw-page-title-main">Cotransporter</span> Type of membrane transport proteins

Cotransporters are a subcategory of membrane transport proteins (transporters) that couple the favorable movement of one molecule with its concentration gradient and unfavorable movement of another molecule against its concentration gradient. They enable coupled or cotransport and include antiporters and symporters. In general, cotransporters consist of two out of the three classes of integral membrane proteins known as transporters that move molecules and ions across biomembranes. Uniporters are also transporters but move only one type of molecule down its concentration gradient and are not classified as cotransporters.

<span class="mw-page-title-main">Norepinephrine transporter</span> Protein-coding gene in the species Homo sapiens

The norepinephrine transporter (NET), also known as noradrenaline transporter (NAT), is a protein that in humans is encoded by the solute carrier family 6 member 2 (SLC6A2) gene.

The Na–K–Cl cotransporter (NKCC) is a transport protein that aids in the secondary active transport of sodium, potassium, and chloride into cells. In humans there are two isoforms of this membrane transport protein, NKCC1 and NKCC2, encoded by two different genes. Two isoforms of the NKCC1/Slc12a2 gene result from keeping or skipping exon 21 in the final gene product.

Neurotransmitter transporters are a class of membrane transport proteins that span the cellular membranes of neurons. Their primary function is to carry neurotransmitters across these membranes and to direct their further transport to specific intracellular locations. There are more than twenty types of neurotransmitter transporters.

<span class="mw-page-title-main">GABA transporter type 1</span> Protein-coding gene in the species Homo sapiens

GABA transporter 1 (GAT1) also known as sodium- and chloride-dependent GABA transporter 1 is a protein that in humans is encoded by the SLC6A1 gene and belongs to the solute carrier 6 (SLC6) family of transporters. It mediates gamma-aminobutyric acid's translocation from the extracellular to intracellular spaces within brain tissue and the central nervous system as a whole.

An amino acid transporter is a membrane transport protein that transports amino acids. They are mainly of the solute carrier family.

<span class="mw-page-title-main">Sodium- and chloride-dependent glycine transporter 1</span> Protein-coding gene in the species Homo sapiens

Sodium- and chloride-dependent glycine transporter 1, also known as glycine transporter 1, is a protein that in humans is encoded by the SLC6A9 gene which is promising therapeutic target for treatment of diabetes and obesity.

<span class="mw-page-title-main">Reuptake inhibitor</span> Type of drug

Reuptake inhibitors (RIs) are a type of reuptake modulators. It is a drug that inhibits the plasmalemmal transporter-mediated reuptake of a neurotransmitter from the synapse into the pre-synaptic neuron. This leads to an increase in extracellular concentrations of the neurotransmitter and an increase in neurotransmission. Various drugs exert their psychological and physiological effects through reuptake inhibition, including many antidepressants and psychostimulants.

GABA transporters are a family of neurotransmitter / sodium symporters, belonging to the solute carrier 6 (SLC6) family. They are found in various regions of the brain in different cell types, such as neurons and astrocytes.

<span class="mw-page-title-main">Sodium-solute symporter</span> Group of transport proteins

Members of the Solute:Sodium Symporter (SSS) Family (TC# 2.A.21) catalyze solute:Na+ symport. The SSS family is within the APC Superfamily. The solutes transported may be sugars, amino acids, organo cations such as choline, nucleosides, inositols, vitamins, urea or anions, depending on the system. Members of the SSS family have been identified in bacteria, archaea and eukaryotes. Almost all functionally well-characterized members normally catalyze solute uptake via Na+ symport.

<span class="mw-page-title-main">Sodium-dependent neutral amino acid transporter B(0)AT2</span> Protein-coding gene in the species Homo sapiens

Sodium-dependent neutral amino acid transporter B(0)AT2 is a protein that in humans is encoded by the SLC6A15 gene.

<span class="mw-page-title-main">Sodium:dicarboxylate symporter</span> Protein family

It has been shown that integral membrane proteins that mediate the uptake of a wide variety of molecules with the concomitant uptake of sodium ions can be grouped, on the basis of sequence and functional similarities into a number of distinct families. One of these families is known as the sodium:dicarboxylate symporter family (SDF).

GABA transporter 2 also known as sodium- and chloride-dependent GABA transporter 2 is one of four GABA transporters, GAT1 (SLC6A1), GAT2 (SLC6A13), GAT3 (SLC6A11) and BGT1 (SLC6A12). Note that GAT2 is different from BGT1 despite the fact that the latter transporter is sometimes referred at as (mouse) GAT-2.

<span class="mw-page-title-main">Bacterial Leucine Transporter</span>

Bacterial Leucine Transporter (LeuT) is a bundled twelve alpha helix protein which belongs to the family of transporters that shuttle amino acids in and out of bacterial cells. Specialized in small hydrophobic amino acids such as leucine and alanine, this transporter is powered by the gradient of sodium ions that is normally maintained by healthy cells across their membranes. LeuT acts as a symporter, which means that it links the passage of a sodium ion across the cell membrane with the transport of the amino acid in the same direction. It was first crystallized to understand the inner molecular mechanisms of antidepressant's work since it has a close resemblance with the human neurotransmitter transporters that these drugs block, thus inhibiting the reuptake of chemical messengers across the cell membrane of nerve axons and glial cells.

The amino acid-polyamine-organocation (APC) superfamily is the second largest superfamily of secondary carrier proteins currently known, and it contains several Solute carriers. Originally, the APC superfamily consisted of subfamilies under the transporter classification number. This superfamily has since been expanded to include eighteen different families.

The ion transporter (IT) superfamily is a superfamily of secondary carriers that transport charged substrates.

References

  1. ↑ Rudnick, G; Krämer, R; Blakely, RD; Murphy, DL; Verrey, F (January 2014). "The SLC6 transporters: perspectives on structure, functions, regulation, and models for transporter dysfunction" (PDF). Pflügers Archiv. 466 (1): 25–42. doi:10.1007/s00424-013-1410-1. PMC   3930102 . PMID   24337881.
  2. 1 2 3 Saier, MH Jr. "2.A.22 The Neurotransmitter:Sodium Symporter (NSS) Family". Transporter Classification Database.
  3. ↑ Attwell D, Bouvier M (1992). "Cloners quick on the uptake". Curr. Biol. 2 (10): 541–543. Bibcode:1992CBio....2..541A. doi:10.1016/0960-9822(92)90024-5. PMID   15336049. S2CID   2334406.
  4. ↑ Zomot, E; Bendahan, A; Quick, M; Zhao, Y; Javitch, JA; Kanner, BI (October 11, 2007). "Mechanism of chloride interaction with neurotransmitter:sodium symporters". Nature. 449 (7163): 726–30. Bibcode:2007Natur.449..726Z. doi: 10.1038/nature06133 . PMID   17704762. S2CID   4391735.
  5. ↑ Malandro MS, Kilberg MS (1996). "Molecular biology of mammalian amino acid transporters". Annu. Rev. Biochem. 65: 305–336. doi:10.1146/annurev.bi.65.070196.001513. PMID   8811182.
  6. ↑ Arriza JL, Amara SG (1993). "Neurotransmitter transporters: three distinct gene families". Curr. Opin. Neurobiol. 3 (3): 337–344. doi:10.1016/0959-4388(93)90126-J. PMID   8103691. S2CID   41721766.
  7. ↑ Uhl GR, Johnson PS (1994). "Neurotransmitter transporters: three important gene families for neuronal function". J. Exp. Biol. 196: 229–236. doi:10.1242/jeb.196.1.229. PMID   7823024.
  8. ↑ Nelson N, Lill H (1998). "Homologies and family relationships among Na+/Cl− neurotransmitter transporters". Neurotransmitter Transporters. Methods in Enzymology. Vol. 296. pp. 425–436. doi:10.1016/S0076-6879(98)96030-X. ISBN   978-0-12-182197-5. PMID   9779464.
  9. ↑ Tavoulari, S; Rizwan, AN; Forrest, LR; Rudnick, G (January 28, 2011). "Reconstructing a chloride-binding site in a bacterial neurotransmitter transporter homologue". Journal of Biological Chemistry. 286 (4): 2834–42. doi: 10.1074/jbc.M110.186064 . PMC   3024779 . PMID   21115480.
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