Neurotransmitter transporter

Class of membrane transport proteins

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.[1]

Vesicular transporters move neurotransmitters into synaptic vesicles, regulating the concentrations of substances within them.[2] Vesicular transporters rely on a proton gradient created by the hydrolysis of adenosine triphosphate (ATP) in order to carry out their work: v-ATPase hydrolyzes ATP, causing protons to be pumped into the synaptic vesicles and creating a proton gradient. Then the efflux of protons from the vesicle provides the energy to bring the neurotransmitter into the vesicle.[3]

Neurotransmitter transporters frequently use electrochemical gradients that exist across cell membranes to carry out their work. For example, some transporters use energy obtained by the cotransport, or symport, of Na+ in order to move glutamate across membranes. Such neurotransporter cotransport systems are highly diverse, as recent development indicates that uptake systems are generally selective and associate with a specific neurotransmitter.[4]

Normally, transporters in the synaptic membrane serve to remove neurotransmitters from the synaptic cleft and prevent their action or bring it to an end. However, on occasion transporters can work in reverse, transporting neurotransmitters into the synapse, allowing these neurotransmitters to bind to their receptors and exert their effect. This "nonvesicular release" of neurotransmitters is used by some cells, such as amacrine cells in the retina, as a normal form of neurotransmitter release.[5]

## Types

[edit]

Postsynaptic
density

Voltage-
gated Ca++
channel

Synaptic
vesicle

Neurotransmitter
transporter

Receptor

Neurotransmitter

Axon terminal

Synaptic cleft

Dendrite

Structure of a typical chemical synapse

Specific types of neurotransmitter transporters include the following:

* Glutamate/aspartate transporters, including:
* Excitatory amino acid transporter 1 (EAAT1)
* Excitatory amino acid transporter 2 (EAAT2)
* Excitatory amino acid transporter 3 (EAAT3)
* Excitatory amino acid transporter 4 (EAAT4)
* Excitatory amino acid transporter 5 (EAAT5)
* Vesicular glutamate transporter 1 (VGLUT1)
* Vesicular glutamate transporter 2 (VGLUT2)
* Vesicular glutamate transporter 3 (VGLUT3)
* GABA transporters, including:
* GABA transporter type 1 (GAT1)
* GABA transporter type 2 (GAT2)
* GABA transporter type 3 (GAT3)
* Betaine transporter (BGT1)
* Vesicular GABA transporter (VGAT)
* Glycine transporters, including:
* Glycine transporter type 1 (GlyT1)
* Glycine transporter type 2 (GlyT2)
* Monoamine transporters, including:
* Dopamine transporter (DAT)
* Norepinephrine transporter (NET)
* Serotonin transporter (SERT)
* Vesicular monoamine transporter 1 (VMAT1)
* Vesicular monoamine transporter 2 (VMAT2)
* Adenosine transporters, including:
* Equilibrative nucleoside transporter 1 (ENT1)
* Equilibrative nucleoside transporter 2 (ENT2)
* Equilibrative nucleoside transporter 3 (ENT3)
* Equilibrative nucleoside transporter 4 (ENT4)
* Vesicular acetylcholine transporter (VAChT)[6]

Note that there is no plasmalemmal acetylcholine transporter, as acetylcholine is terminated via rapid metabolism into choline by cholinesterase enzymes, and choline is subsequently transported back into the cell and reconverted into acetylcholine.

Transporters associated with histamine and the endocannabinoids have not yet been identified.

## Clinical significance

[edit]

A variety of neurotransmitter reuptake transporters are pharmacotherapeutic targets for modulating the synaptic neurotransmitter concentration, and therefore neurotransmission.

* Antidepressants such as SSRIs, SNRIs and TCAs suppress the activity of serotonin and/or norepinephrine transporters, preventing the reuptake of targeted neurotransmitters from the synaptic cleft.
* Psychostimulants like cocaine, amphetamines, and methylphenidate act by inhibiting and/or reversing the dopamine and/or norepinephrine transporters. Some dissociatives like phencyclidine and ketamine are also dopamine transporter inhibitors.
* Tiagabine, a drug used as an anticonvulsant, acts by inhibiting the GABA transporter 1.

Neurotransmitter transporters inhibitors

Vesicular transporters could provide an alternative therapeutic target for the modulation of chemical neurotransmission, as the activity of these transporters could affect the quantity of neurotransmitter released.[7]

* Vesamicol, for example, is an inhibitor of the vesicular acetylcholine transporter. It prevents the loading of ACh into the presynaptic vesicles, causing a fall in the amount that is released in response to a neuronal action potential. It is not used clinically, but provides a useful tool for research into the behaviour of neurotransmitter vesicles.[8]

## References

[edit]

1. ^ Iversen L (July 2000). "Neurotransmitter transporters: fruitful targets for CNS drug discovery". Mol. Psychiatry. 5 (4): 357–62\. doi:10.1038/sj.mp.4000728. PMID 10889545.
2. ^ Johnson J, Tian N, Caywood MS, Reimer RJ, Edwards RH, Copenhagen DR (January 2003). "Vesicular neurotransmitter transporter expression in developing postnatal rodent retina: GABA and glycine precede glutamate". J. Neurosci. 23 (2): 518–29\. doi:10.1523/JNEUROSCI.23-02-00518.2003. PMC 6741860. PMID 12533612.
3. ^ Kandel ER, Schwartz JH, Jessell TM (2000). Principles of neural science (4th ed.). New York: McGraw-Hill. p. 287. ISBN 0-8385-7701-6.`{{cite book}}`: CS1 maint: multiple names: authors list (link)
4. ^ Amara, Susan G.; Kuhar, Michael J. (1993). "Neurotransmitter Transporters:Recent Progress". Annual Review of Neuroscience. 16 (1): 73–93\. doi:10.1146/annurev.ne.16.030193.000445. PMID 8096377.
5. ^ Kandel ER, Schwartz JH, Jessell TM (2000). Principles of neural science (4th ed.). New York: McGraw-Hill. p. 295. ISBN 0-8385-7701-6.`{{cite book}}`: CS1 maint: multiple names: authors list (link)
6. ^ Weihe E, Tao-Cheng JH, Schäfer MK, Erickson JD, Eiden LE (April 1996). "Visualization of the vesicular acetylcholine transporter in cholinergic nerve terminals and its targeting to a specific population of small synaptic vesicles". Proc Natl Acad Sci USA. 93 (8): 3547–52\. Bibcode:1996PNAS...93.3547W. doi:10.1073/pnas.93.8.3547. PMC 39647. PMID 8622973.
7. ^ Varoqui H, Erickson JD (October 1997). "Vesicular neurotransmitter transporters. Potential sites for the regulation of synaptic function". Molecular Neurobiology. 15 (2): 165–91\. doi:10.1007/BF02740633. PMID 9396009. S2CID 26111849.
8. ^ Prior C, Marshall IG, Parsons SM (November 1992). "The pharmacology of vesamicol: an inhibitor of the vesicular acetylcholine transporter". General Pharmacology. 23 (6): 1017–22\. doi:10.1016/0306-3623(92)90280-w. PMID 1487110.

## External links

[edit]

Wikimedia Commons has media related to Neurotransmitter transporters.

* Neurotransmitter+Transporters at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
* Clearing Your Mind of Neurotransmitters: Functional Impact of Neurotransmitter Transporter Gene Variants \- a videocast of the lecture by Randy Blakely, Ph.D., Vanderbilt University. Part of NIH Neuroscience Seminar series. 450 Mb file, .m4v format.
* The Blakely Lab \- Laboratory exploring the molecular basis for neurotransmitter transporter structure, function and regulation.

* v
* t
* e

Neurotransmitters

Amino acid-derived|

| Major excitatory /
inhibitory systems|

| Glutamate system|

* Agmatine
* Aspartic acid (aspartate)
* Glutamic acid (glutamate)
* Glutathione
* Glycine
* GSNO
* GSSG
* Kynurenic acid
* NAA
* NAAG
* Proline
* Serine

|

GABA system|

* GABA
* GABOB
* GHB

Glycine system|

* α-Alanine
* β-Alanine
* Glycine
* Hypotaurine
* Proline
* Sarcosine
* Serine
* Taurine

GHB system|

* GHB
* T-HCA (GHC)

Biogenic amines|

| Monoamines|

* 6-OHM
* Dopamine
* Epinephrine (adrenaline)
* NAS (normelatonin)
* Norepinephrine (noradrenaline)
* Serotonin (5-HT)

|

Trace amines|

* 3-Iodothyronamine
* N-Methylphenethylamine
* N-Methyltryptamine
* m-Octopamine
* p-Octopamine
* Phenylethanolamine
* Phenethylamine
* Synephrine
* Tryptamine
* m-Tyramine
* p-Tyramine

Others|

* Histamine

Neuropeptides|

* See here instead.

Lipid-derived|

| Endocannabinoids|

* 2-AG
* 2-AGE (noladin ether)
* 2-ALPI
* 2-OG
* AA-5-HT
* Anandamide (AEA)
* DEA
* LPI
* NADA
* NAGly
* OEA
* Oleamide
* PEA
* RVD-Hpα
* SEA
* Virodhamine (O-AEA)

|

Neurosteroids|

* See here instead.

Nucleobase-derived|

| Nucleosides|

| Adenosine system|

* ADP
* AMP
* ATP

|

Vitamin-derived|

|

Miscellaneous|

| Cholinergic system|

* Acetylcholine

|

Gasotransmitters|

* Carbon monoxide (CO)
* Hydrogen sulfide (H2S)
* Nitric oxide (NO)

|

Candidates|

* Acetaldehyde
* Ammonia (NH3)
* Carbonyl sulfide (COS)
* Nitrous oxide (N2O)
* Sulfur dioxide (SO2)

|

* v
* t
* e

Pharmacomodulation

Types|

* ♦ Enzyme: Inducer
* Inhibitor

* ♦ Ion channel: Opener
* Blocker

* ♦ Receptor: Agonist
* Partial agonist
* Antagonist
* Inverse agonist
* Positive allosteric modulator (PAM)
* Negative allosteric modulator (NAM)

* ♦ Transporter [Reuptake vs Efflux]: Enhancer (RE)
* Inhibitor (RI)
* Releaser (RA)

* ♦ Miscellaneous: Precursor
* Cofactor

Classes|

| Enzyme|

see Enzyme inhibition

|

Ion channel|

See Ion channel modulators

Receptor &
transporter|

| BA/M|

| Adrenergic|

* Adrenergic receptor agonist (α
* β (1
* 2))
* Adrenergic receptor antagonist (α (1
* 2)
* β)
* Norepinephrine reuptake inhibitor (NRI)

|

Dopaminergic|

* Dopamine receptor agonist
* Dopamine receptor antagonist
* Dopamine reuptake inhibitor (DRI)

Histaminergic|

* Histamine receptor agonist
* Histamine receptor antagonist (H1
* H2
* H3)

Serotonergic|

* Serotonin receptor agonist
* Serotonin receptor antagonist (5-HT3)
* Serotonin reuptake inhibitor (SRI)

AA|

| GABAergic|

* GABA receptor agonist
* GABA receptor antagonist
* GABA reuptake inhibitor (GRI)

|

Glutamatergic|

* Glutamate receptor agonist (AMPA)
* Glutamate receptor antagonist (NMDA)
* Glutamate reuptake inhibitor

Cholinergic|

* Acetylcholine receptor agonist (Muscarinic
* Nicotinic)
* Cholinesterase inhibitor
* Acetylcholine receptor antagonist (Muscarinic
* Nicotinic (Ganglionic
* Muscular))

Cannabinoidergic|

* Cannabinoid receptor agonist
* Cannabinoid receptor antagonist
* Endocannabinoid enhancer (eCBE)
* Endocannabinoid reuptake inhibitor (eCBRI)

Opioidergic|

* Opioid modulator
* Opioid receptor agonist
* Opioid receptor antagonist
* Enkephalinase inhibitor

Other|

* Adenosine reuptake inhibitor (AdoRI)
* Angiotensin II receptor antagonist
* Endothelin receptor antagonist
* NK1 receptor antagonist
* Vasopressin receptor antagonist

Miscellaneous|

* Cofactor (see Enzyme cofactors)
* Precursor (see Amino acids)

* v
* t
* e

Membrane proteins, carrier proteins: membrane transport proteins solute carrier (TC 2A)

By group

SLC1–10

| (1):|

* high affinity glutamate and neutral amino-acid transporter
* SLC1A1
* 2
* 3
* 4
* 5
* 6
* 7

|

(2):|

* facilitative GLUT transporter
* SLC2A1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* 9
* 10
* 11
* 12
* 13
* 14

(3):|

* heavy subunits of heterodimeric amino-acid transporters
* SLC3A1
* 2

(4):|

* bicarbonate transporter
* SLC4A1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* 9
* 10
* 11

(5):|

* sodium glucose cotransporter
* SLC5A1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* 9
* 10
* 11
* 12

(6):|

* sodium\- and chloride\- dependent sodium:neurotransmitter symporters
* SLC6A1
* SLC6A2
* SLC6A3
* SLC6A4
* SLC6A5
* SLC6A6
* SLC6A7
* SLC6A8
* SLC6A9
* SLC6A10
* SLC6A11
* SLC6A12
* SLC6A13
* SLC6A14
* SLC6A15
* SLC6A16
* SLC6A17
* SLC6A18
* SLC6A19
* SLC6A20

(7):|

* cationic amino-acid transporter/glycoprotein-associated
* SLC7A1
* SLC7A2
* SLC7A3
* SLC7A4
* glycoprotein-associated/light or catalytic subunits of heterodimeric amino-acid transporters
* SLC7A5
* SLC7A6
* SLC7A7
* SLC7A8
* SLC7A9
* SLC7A10
* SLC7A11
* SLC7A13
* SLC7A14

(8):|

* Na+/Ca2+ exchanger
* SLC8A1
* SLC8A2
* SLC8A3

(9):|

* Na+/H+ exchanger
* SLC9A1
* SLC9A2
* SLC9A3
* SLC9A4
* SLC9A5
* SLC9A6
* SLC9A7
* SLC9A8
* SLC9A9
* SLC9A10
* SLC9A11

(10):|

* sodium bile salt cotransport
* SLC10A1
* SLC10A2
* SLC10A3
* SLC10A4
* SLC10A5
* SLC10A6
* SLC10A7
* 10A1
* 10A2
* 10A3
* 10A7

SLC11–20

| (11):|

* proton coupled metal ion transporter
* SLC11A1
* SLC11A211A3

|

(12):|

* electroneutral cation-Cl cotransporter
* SLC12A1
* SLC12A2
* SLC12A3
* SLC12A4
* SLC12A5
* SLC12A6
* SLC12A7
* SLC12A8
* SLC12A9

(13):|

* human Na+-sulfate/carboxylate cotransporter
* SLC13A1
* SLC13A2
* SLC13A3
* SLC13A4
* SLC13A5

(14):|

* urea transporter
* SLC14A1
* SLC14A2

(15):|

* proton oligopeptide cotransporter
* SLC15A1
* SLC15A2
* SLC15A3
* SLC15A4

(16):|

* monocarboxylate transporter
* SLC16A1
* SLC16A2
* SLC16A3
* SLC16A4
* SLC16A5
* SLC16A6
* SLC16A7
* SLC16A8
* SLC16A9
* SLC16A10
* SLC16A11
* SLC16A12
* SLC16A13
* SLC16A14

(17):|

* Vesicular glutamate transporter 1
* SLC17A1
* SLC17A2
* SLC17A3
* SLC17A4
* SLC17A5
* SLC17A6
* SLC17A7
* SLC17A8
* SLC17A9

(18):|

* vesicular monoamine transporter
* SLC18A1
* SLC18A2
* SLC18A3

(19):|

* folate/thiamine transporter
* SLC19A1
* SLC19A2
* SLC19A3

(20):|

* type III Na+-phosphate cotransporter
* SLC20A1
* SLC20A2

SLC21–30

| (21):|

* Organic anion-transporting polypeptide
* SLCO1A2
* SLCO1B1
* SLCO1B3
* SLCO1B4
* SLCO1C1
*     * SLCO2A1
* SLCO2B1
*     * SLCO3A1
*     * SLCO4A1
* SLCO4C1
*     * SLCO5A1(SLCO6A1)

|

(22):|

* organic cation/anion/zwitterion transporter
* SLC22A1
* SLC22A2
* SLC22A3
* SLC22A4
* SLC22A5
* SLC22A6
* SLC22A7
* SLC22A8
* SLC22A9
* SLC22A10
* SLC22A11
* SLC22A12
* SLC22A13
* SLC22A14
* SLC22A15
* SLC22A16
* SLC22A17
* SLC22A18
* SLC22A19
* SLC22A20

(23):|

* Na+-dependent ascorbic acid transporter
* SLC23A1
* SLC23A2
* SLC23A3
* SLC23A4

(24):|

* Na+/(Ca2+-K+) exchanger
* SLC24A1
* SLC24A2
* SLC24A3
* SLC24A4
* SLC24A5
* SLC24A6

(25):|

* mitochondrial carrier
* SLC25A1
* SLC25A2
* SLC25A3
* SLC25A4
* SLC25A5
* SLC25A6
* SLC25A7
* SLC25A8
* SLC25A9
* SLC25A10
* SLC25A11
* SLC25A12
* SLC25A13
* SLC25A14
* SLC25A15
* SLC25A16
* SLC25A17
* SLC25A18
* SLC25A19
* SLC25A20
* SLC25A21
* SLC25A22
* SLC25A23
* SLC25A24
* SLC25A25
* SLC25A26
* SLC25A27
* SLC25A28
* SLC25A29
* SLC25A30
* SLC25A31
* SLC25A32
* SLC25A33
* SLC25A34
* SLC25A35
* SLC25A36
* SLC25A37
* SLC25A38
* SLC25A39
* SLC25A40
* SLC25A41
* SLC25A42
* SLC25A43
* SLC25A44
* SLC25A45
* SLC25A46

(26):|

* multifunctional anion exchanger
* SLC26A1
* SLC26A2
* SLC26A3
* SLC26A4
* SLC26A5
* SLC26A6
* SLC26A7
* SLC26A8
* SLC26A9
* SLC26A10
* SLC26A11

(27):|

* fatty acid transport proteins
* SLC27A1
* SLC27A2
* SLC27A3
* SLC27A4
* SLC27A5
* SLC27A6

(28):|

* Na+-coupled nucleoside transport (SLC28A1
* SLC28A2
* SLC28A3

(29):|

* facilitative nucleoside transporter
* SLC29A1
* SLC29A2
* SLC29A3
* SLC29A4

(30):|

* zinc efflux
* SLC30A1
* SLC30A2
* SLC30A3
* SLC30A4
* SLC30A5
* SLC30A6
* SLC30A7
* SLC30A8
* SLC30A9
* SLC30A10

SLC31–40

| (31):|

* copper transporter
* SLC31A1

|

(32):|

* Vesicular glutamate transporter 1
* SLC32A1

(33):|

* Acetyl-CoA transporter
* SLC33A1

(34):|

* type II Na+-phosphate cotransporter
* SLC34A1
* SLC34A2
* SLC34A3

(35):|

* nucleoside-sugar transporter
* SLC35A1
* SLC35A2
* SLC35A3
* SLC35A4
* SLC35A5
*     * SLC35B1
* SLC35B2
* SLC35B3
* SLC35B4
*     * SLC35C1
* SLC35C2
*     * SLC35D1
* SLC35D2
* SLC35D3
*     * SLC35E1
* SLC35E2
* SLC35E3
* SLC35E4

(36):|

* proton-coupled amino-acid transporter
* SLC36A1
* SLC36A2
* SLC36A3
* SLC36A436A2

(37):|

* sugar-phosphate/phosphate exchanger
* SLC37A1
* SLC37A2
* SLC37A3
* SLC37A4

(38):|

* System A & N, sodium-coupled neutral amino-acid transporter
* SLC38A1
* SLC38A2
* SLC38A3
* SLC38A4
* SLC38A5
* SLC38A6
* SLC38A10

(39):|

* metal ion transporter
* SLC39A1
* SLC39A2
* SLC39A3
* SLC39A4
* SLC39A5
* SLC39A6
* SLC39A7
* SLC39A8
* SLC39A9
* SLC39A10
* SLC39A11
* SLC39A12
* SLC39A13
* SLC39A14

(40):|

* basolateral iron transporter
* SLC40A1

SLC41–48

| (41):|

* Magnesium transporter E
* SLC41A1
* SLC41A2
* SLC41A3

|

(42):|

* Ammonia transporter
* RhAG
* RhBG
* RhCG

(43):|

* Na+-independent, system-L like amino-acid transporter
* SLC43A1
* SLC43A2
* SLC43A3

(44):|

* Choline-like transporter
* SLC44A1
* SLC44A2
* SLC44A3
* SLC44A4
* SLC44A5

(45):|

* Putative sugar transporter
* SLC45A1
* SLC45A2
* SLC54A3
* SLC45A4

(46):|

* Folate transporter
* SLC46A1
* SLC46A2

(47):|

* multidrug and toxin extrusion
* SLC47A1
* SLC47A2

(48):|

* Heme transporter

SLCO1–4

* O1A2
* O1B1
* O1B3
* O2B1
* O431
* O4A1

Ion pumps

| Symporter, Cotransporter|

* Na+/K+,Cl−
* Na+/Pi3
* Na+/Cl−
* Na+/glucose
* Na+/I−
* Cl−/K+
* 4
* 5

|

Antiporter (exchanger)|

* Na+/H+
* Na+/Ca2+
* Na+/(Ca2+-K+) - Cl−/HCO−
3 (Band 3)
* Cl−-formate
* Cl−-oxalate

see also solute carrier disorders

* v
* t
* e

Membrane transport protein: neurotransmitter transporters (TC 2.A.1.2)

Vesicular|

* Vesicular monoamine
* VMAT1
* VMAT2
* Vesicular acetylcholine
* Vesicular glutamate
* Vesicular GABA

Other|

* Monoamine
* DAT
* NET
* SERT
* PMAT
* Excitatory amino-acid transporter
* GABA transporter

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template