Dopamine Active Transporter
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The dopamine transporter (DAT, also sodium-dependent dopamine transporter) is a membrane-spanning protein coded for in humans by the ''SLC6A3''
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
(also known as ''DAT1''), that pumps the
neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotra ...
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
out of the
synaptic cleft Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in neuromuscular junction, muscles or glands. Chemical synapses allow neurons to form biological neural ...
back into
cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...
. In the cytosol, other transporters sequester the dopamine into
vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle In a neuron, synaptic vesicles (or neurotransmitter vesicles) s ...
for storage and later release. Dopamine reuptake via DAT provides the primary mechanism through which dopamine is cleared from
synapse In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending o ...
s, although there may be an exception in the
prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. It is the association cortex in the frontal lobe. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, ...
, where evidence points to a possibly larger role of the
norepinephrine transporter 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. NET is a monoamine transporter and is responsible for the sodium ...
. DAT is implicated in a number of dopamine-related disorders, including
attention deficit hyperactivity disorder Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple con ...
,
bipolar disorder Bipolar disorder (BD), previously known as manic depression, is a mental disorder characterized by periods of Depression (mood), depression and periods of abnormally elevated Mood (psychology), mood that each last from days to weeks, and in ...
,
clinical depression Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Intro ...
,
eating disorder An eating disorder is a mental disorder defined by abnormal eating behaviors that adversely affect a person's health, physical or mental health, mental health. These behaviors may include eating too much food or too little food. Types of eatin ...
s, and
substance use disorder Substance use disorder (SUD) is the persistent use of drugs despite substantial harm and adverse consequences to self and others. Related terms include ''substance use problems'' and ''problematic drug or alcohol use''. Along with substance-ind ...
s. The gene that encodes the DAT protein is located on
chromosome 5 Chromosome 5 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 5 spans about 182 million base pairs (the building blocks of DNA) and represents almost 6% of the total DNA in cells. Ch ...
, consists of 15 coding
exons An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence i ...
, and is roughly 64 kbp long. Evidence for the associations between DAT and dopamine related disorders has come from a type of
genetic polymorphism A gene is said to be polymorphic if more than one allele occupies that gene's locus within a population. In addition to having more than one allele at a specific locus, each allele must also occur in the population at a rate of at least 1% to ge ...
, known as a
variable number tandem repeat A variable number tandem repeat (or VNTR) is a location in a genome where a short nucleotide sequence is organized as a tandem repeat. These can be found on many chromosomes, and often show variations in length (number of repeats) among indivi ...
, in the ''SLC6A3'' gene, which influences the amount of protein expressed.


Function

DAT is an
integral membrane protein An integral, or intrinsic, membrane protein (IMP) is a type of membrane protein that is permanently attached to the biological membrane. All transmembrane proteins can be classified as IMPs, but not all IMPs are transmembrane proteins. IMPs comp ...
that removes dopamine from the
synaptic cleft Chemical synapses are biological junctions through which neurons' signals can be sent to each other and to non-neuronal cells such as those in neuromuscular junction, muscles or glands. Chemical synapses allow neurons to form biological neural ...
and deposits it into surrounding cells, thus terminating the signal of the neurotransmitter.
Dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
underlies several aspects of cognition, including reward, and DAT facilitates regulation of that signal.


Mechanism

DAT is a
symporter A symporter is an integral membrane protein that is involved in the transport of two (or more) different molecules across the cell membrane in the same direction. The symporter works in the plasma membrane and molecules are transported across th ...
that moves dopamine across the cell membrane by coupling the movement to the energetically-favorable movement of sodium ions moving from high to low concentration into the cell. DAT function requires the sequential binding and
co-transport In cellular biology, active transport is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. Active transport requires cellula ...
of two Na+
ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s and one Cl ion with the dopamine substrate. The driving force for DAT-mediated dopamine reuptake is the ion concentration gradient generated by the plasma membrane Na+/K+ ATPase. In the most widely accepted
model A model is an informative representation of an object, person, or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin , . Models can be divided in ...
for
monoamine transporter Monoamine transporters (MATs) are proteins that function as integral Cell membrane, plasma-membrane Neurotransmitter transporter, transporters to regulate concentrations of extracellular monoamine neurotransmitters. The three major classes are se ...
function, sodium ions must bind to the extracellular domain of the transporter before dopamine can bind. Once dopamine binds, the protein undergoes a conformational change, which allows both sodium and dopamine to unbind on the intracellular side of the membrane. Studies using
electrophysiology Electrophysiology (from ee the Electron#Etymology, etymology of "electron" ; and ) is the branch of physiology that studies the electrical properties of biological cell (biology), cells and tissues. It involves measurements of voltage change ...
and radioactive-labeled dopamine have confirmed that the dopamine transporter is similar to other monoamine transporters in that one molecule of neurotransmitter can be transported across the membrane with one or two sodium ions. Chloride ions are also needed to prevent a buildup of positive charge. These studies have also shown that transport rate and direction is totally dependent on the sodium gradient. Because of the tight coupling of the
membrane potential Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. It equals the interior potential minus the exterior potential. This is th ...
and the sodium gradient, activity-induced changes in membrane polarity can dramatically influence transport rates. In addition, the transporter may contribute to dopamine release when the neuron depolarizes.


DAT–Cav coupling

Preliminary evidence suggests that the dopamine transporter couples to L-type
voltage-gated calcium channels Voltage-gated calcium channels (VGCCs), also known as voltage-dependent calcium channels (VDCCs), are a group of voltage-gated ion channels found in the membrane of excitable cells (''e.g.'' muscle, glial cells, neurons) with a permeability to ...
(particularly Cav1.2 and Cav1.3), which are expressed in virtually all dopamine neurons. As a result of DAT–Cav coupling, DAT substrates that produce
depolarizing In biology, depolarization or hypopolarization is a change within a cell, during which the cell undergoes a shift in electric charge distribution, resulting in less negative charge inside the cell compared to the outside. Depolarization is esse ...
currents through the transporter are able to open calcium channels that are coupled to the transporter, resulting in a calcium influx in dopamine neurons. This calcium influx is believed to induce
CAMKII /calmodulin-dependent protein kinase II (CaM kinase II or CaMKII) is a serine/threonine-specific protein kinase that is regulated by the /calmodulin complex. CaMKII is involved in many signaling cascades and is thought to be an important mediat ...
-mediated
phosphorylation In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: : This equation can be writ ...
of the dopamine transporter as a downstream effect; since DAT phosphorylation by CAMKII results in dopamine efflux
in vivo Studies that are ''in vivo'' (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, an ...
, activation of transporter-coupled calcium channels is a potential mechanism by which certain drugs (e.g.,
amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
) trigger neurotransmitter release.


Protein structure

The initial determination of the membrane topology of DAT was based upon hydrophobic sequence analysis and sequence similarities with the GABA transporter. These methods predicted twelve
transmembrane domain A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain. TMDs may consist of one or several alpha-helices or a transmembrane beta barrel. Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in ...
s (TMD) with a large extracellular loop between the third and fourth TMDs. Further characterization of this protein used
proteases A protease (also called a peptidase, proteinase, or proteolytic enzyme) is an enzyme that catalyzes proteolysis, breaking down proteins into smaller polypeptides or single amino acids, and spurring the formation of new protein products. They do ...
, which digest proteins into smaller fragments, and
glycosylation Glycosylation is the reaction in which a carbohydrate (or ' glycan'), i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor) in order to form a glycoconjugate. In biology (but not ...
, which occurs only on extracellular loops, and largely verified the initial predictions of membrane topology. The exact structure of the
Drosophila melanogaster ''Drosophila melanogaster'' is a species of fly (an insect of the Order (biology), order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly" ...
dopamine transporter (dDAT) was elucidated in 2013 by
X-ray crystallography X-ray crystallography is the experimental science of determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to Diffraction, diffract in specific directions. By measuring th ...
.


Location and distribution

Regional distribution of DAT has been found in areas of the brain with established dopaminergic circuitry, including the nigrostriatal, mesolimbic, and mesocortical pathways. The nuclei that make up these pathways have distinct patterns of expression. Gene expression patterns in the adult mouse show high expression in the
substantia nigra The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra a ...
pars compacta. DAT in the
mesocortical pathway The mesocortical pathway is a dopaminergic pathway that connects the ventral tegmentum to the prefrontal cortex. It is one of the four major dopamine pathways in the brain. It is essential to the normal cognitive function of the dorsolateral pre ...
, labeled with radioactive antibodies, was found to be enriched in dendrites and cell bodies of neurons in the
substantia nigra The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra a ...
pars compacta and
ventral tegmental area The ventral tegmental area (VTA) (tegmentum is Latin for ''covering''), also known as the ventral tegmental area of Tsai, or simply ventral tegmentum, is a group of neurons located close to the midline on the floor of the midbrain. The VTA is th ...
. This pattern makes sense for a protein that regulates dopamine levels in the synapse. Staining in the
striatum The striatum (: striata) or corpus striatum is a cluster of interconnected nuclei that make up the largest structure of the subcortical basal ganglia. The striatum is a critical component of the motor and reward systems; receives glutamat ...
and
nucleus accumbens The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the ''nucleus accumbens septi'', Latin for ' nucleus adjacent to the septum') is a region in the basal forebrain rostral to the preoptic area of the hypo ...
of the mesolimbic pathway was dense and heterogeneous. In the striatum, DAT is localized in the plasma membrane of axon terminals. Double
immunocytochemistry Immunocytochemistry (ICC) is a common laboratory technique that is used to anatomically visualize the localization of a specific protein or antigen in cells by use of a specific primary antibody that binds to it. The primary antibody allows vis ...
demonstrated DAT colocalization with two other markers of nigrostriatal terminals,
tyrosine hydroxylase Tyrosine hydroxylase or tyrosine 3-monooxygenase is the enzyme responsible for catalyzing the conversion of the amino acid L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA). It does so using molecular oxygen (O2), as well as iron (Fe2+) and ...
and D2 dopamine receptors. The latter was thus demonstrated to be an
autoreceptor An autoreceptor is a type of Receptor (biochemistry), receptor located in the cell membrane, membranes of neuron, nerve cells. It serves as part of a negative feedback loop in signal transduction. It is only sensitive to the neurotransmitters or ...
on cells that release dopamine.
TAAR1 Trace amine-associated receptor 1 (TAAR1) is a trace amine-associated receptor (TAAR) protein that in humans is encoded by the ''TAAR1'' gene. TAAR1 is a primarily intracellular amine-activated and G protein-coupled receptor (GPCR) that is p ...
is a presynaptic intracellular receptor that is also colocalized with DAT and which has the opposite effect of the D2 autoreceptor when activated; i.e., it internalizes dopamine transporters and induces efflux through reversed transporter function via
PKA In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction :H ...
and PKC signaling. Surprisingly, DAT was not identified within any synaptic active zones. These results suggest that striatal dopamine reuptake may occur outside of synaptic specializations once dopamine diffuses from the synaptic cleft. In the
substantia nigra The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. ''Substantia nigra'' is Latin for "black substance", reflecting the fact that parts of the substantia nigra a ...
, DAT is localized to axonal and dendritic (i.e., pre- and post-synaptic) plasma membranes. Within the perikarya of
pars compacta The pars compacta (SNpc, SNc) is one of two subdivisions of the ''substantia nigra'' of the midbrain (the other being the pars reticulata); it is situated medial to the ''pars reticulata''. It is formed by dopaminergic neurons. It projects to th ...
neurons, DAT was localized primarily to rough and smooth endoplasmic reticulum,
Golgi complex The Golgi apparatus (), also known as the Golgi complex, Golgi body, or simply the Golgi, is an organelle found in most eukaryotic Cell (biology), cells. Part of the endomembrane system in the cytoplasm, it protein targeting, packages proteins ...
, and multivesicular bodies, identifying probable sites of synthesis, modification, transport, and degradation.


Genetics and regulation

The
gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...
for DAT, known as DAT1, is located on chromosome 5p15. The protein encoding region of the gene is over 64 kb long and comprises 15 coding segments or
exons An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequence i ...
. This gene has a
variable number tandem repeat A variable number tandem repeat (or VNTR) is a location in a genome where a short nucleotide sequence is organized as a tandem repeat. These can be found on many chromosomes, and often show variations in length (number of repeats) among indivi ...
(VNTR) at the 3’ end ( rs28363170) and another in the
intron An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e., a region inside a gene."The notion of the cistron .e., gen ...
8 region. Differences in the VNTR have been shown to affect the basal level of expression of the transporter; consequently, researchers have looked for associations with dopamine-related disorders.
Nurr1 The nuclear receptor 4A2 (NR4A2) (nuclear receptor subfamily 4 group A member 2) also known as nuclear receptor related 1 protein (NURR1) is a protein that in humans is encoded by the ''NR4A2'' gene. NR4A2 is a member of the nuclear receptor fami ...
, a
nuclear receptor In the field of molecular biology, nuclear receptors are a class of proteins responsible for sensing steroids, thyroid hormones, vitamins, and certain other molecules. These intracellular receptors work with other proteins to regulate the ex ...
that regulates many dopamine-related genes, can bind the promoter region of this gene and induce expression. This promoter may also be the target of the
transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription (genetics), transcription of genetics, genetic information from DNA to messenger RNA, by binding t ...
Sp-1. While transcription factors control which cells express DAT, functional regulation of this protein is largely accomplished by
kinases In biochemistry, a kinase () is an enzyme that catalysis, catalyzes the transfer of phosphate groups from High-energy phosphate, high-energy, phosphate-donating molecules to specific Substrate (biochemistry), substrates. This process is known as ...
.
MAPK A mitogen-activated protein kinase (MAPK or MAP kinase) is a type of serine/threonine-specific protein kinases involved in directing cellular responses to a diverse array of stimuli, such as mitogens, osmotic stress, heat shock and proinflamm ...
,
CAMKII /calmodulin-dependent protein kinase II (CaM kinase II or CaMKII) is a serine/threonine-specific protein kinase that is regulated by the /calmodulin complex. CaMKII is involved in many signaling cascades and is thought to be an important mediat ...
,
PKA In chemistry, an acid dissociation constant (also known as acidity constant, or acid-ionization constant; denoted ) is a quantitative measure of the strength of an acid in solution. It is the equilibrium constant for a chemical reaction :H ...
, and PKC can modulate the rate at which the transporter moves dopamine or cause the internalization of DAT. Co-localized
TAAR1 Trace amine-associated receptor 1 (TAAR1) is a trace amine-associated receptor (TAAR) protein that in humans is encoded by the ''TAAR1'' gene. TAAR1 is a primarily intracellular amine-activated and G protein-coupled receptor (GPCR) that is p ...
is an important regulator of the dopamine transporter that, when activated, phosphorylates DAT through
protein kinase A In cell biology, protein kinase A (PKA) is a family of serine-threonine kinases whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, in ...
(PKA) and
protein kinase C In cell biology, protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and t ...
(PKC) signaling.
Phosphorylation In biochemistry, phosphorylation is described as the "transfer of a phosphate group" from a donor to an acceptor. A common phosphorylating agent (phosphate donor) is ATP and a common family of acceptor are alcohols: : This equation can be writ ...
by either protein kinase can result in DAT
internalization Internalization may refer to: * Internalization (sociology) *Internalization (psychology) ** Internalizing disorder *Internalization (biology) Endocytosis is a cellular process in which substances are brought into the cell. The material to be ...
( reuptake inhibition), but phosphorylation alone induces reverse transporter function (dopamine efflux). Dopamine autoreceptors also regulate DAT by directly opposing the effect of TAAR1 activation. The human dopamine transporter (hDAT) contains a high affinity extracellular
zinc Zinc is a chemical element; it has symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic tabl ...
binding site In biochemistry and molecular biology, a binding site is a region on a macromolecule such as a protein that binds to another molecule with specificity. The binding partner of the macromolecule is often referred to as a ligand. Ligands may includ ...
which, upon zinc binding, inhibits dopamine
reuptake Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal (i.e., the pre-synaptic neuron at a synapse) or glial cell after it has performed its function of transmi ...
and amplifies
amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
-induced dopamine efflux ''
in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...
''. In contrast, the human
serotonin transporter The serotonin transporter (SERT or 5-HTT) 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 t ...
(hSERT) and human
norepinephrine transporter 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. NET is a monoamine transporter and is responsible for the sodium ...
(hNET) do not contain zinc binding sites.
Zinc supplementation Zinc deficiency is defined either as insufficient body levels of zinc to meet the needs of the body, or as a zinc blood level below the normal range. However, since a decrease in blood concentration is only detectable after long-term or severe ...
may reduce the minimum effective dose of amphetamine when it is used for the treatment of
attention deficit hyperactivity disorder Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple con ...
.


Biological role and disorders

The rate at which DAT removes dopamine from the synapse can have a profound effect on the amount of dopamine in the cell. This is best evidenced by the severe cognitive deficits, motor abnormalities, and hyperactivity of mice with no dopamine transporters. These characteristics have striking similarities to the symptoms of
ADHD Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by symptoms of inattention, hyperactivity, impulsivity, and emotional dysregulation that are excessive and pervasive, impairing in multiple ...
. Differences in the functional VNTR have been identified as risk factors for bipolar disorder and ADHD. Data has emerged that suggests there is also an association with stronger withdrawal symptoms from
alcoholism Alcoholism is the continued drinking of alcohol despite it causing problems. Some definitions require evidence of dependence and withdrawal. Problematic use of alcohol has been mentioned in the earliest historical records. The World He ...
, although this is a point of controversy. An
allele An allele is a variant of the sequence of nucleotides at a particular location, or Locus (genetics), locus, on a DNA molecule. Alleles can differ at a single position through Single-nucleotide polymorphism, single nucleotide polymorphisms (SNP), ...
of the DAT gene with normal protein levels is associated with non-smoking behavior and ease of quitting. Additionally, male adolescents particularly those in high-risk families (ones marked by a disengaged mother and absence of maternal affection) who carry the 10-allele VNTR repeat show a statistically significant affinity for antisocial peers. Increased activity of DAT is associated with several different disorders, including
clinical depression Major depressive disorder (MDD), also known as clinical depression, is a mental disorder characterized by at least two weeks of pervasive low mood, low self-esteem, and loss of interest or pleasure in normally enjoyable activities. Intro ...
. Mutations in DAT have been shown to cause dopamine transporter deficiency syndrome, an
autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the Phenotype, effect of a different variant of the same gene on Homologous chromosome, the other copy of the chromosome. The firs ...
movement disorder Movement disorders are clinical syndromes with either an excess of movement or a paucity of voluntary and involuntary movements, unrelated to weakness or spasticity. Movement disorders present with extrapyramidal symptoms and are caused by basa ...
characterized by progressively worsening
dystonia Dystonia is a neurology, neurological Hyperkinesia, hyperkinetic Movement disorders, movement disorder in which sustained or repetitive muscle contractions occur involuntarily, resulting in twisting and repetitive movements or abnormal fixed po ...
and
parkinsonism Parkinsonism is a clinical syndrome characterized by tremor, bradykinesia (slowed movements), Rigidity (neurology), rigidity, and balance disorder, postural instability. Both hypokinetic features (bradykinesia and akinesia) and hyperkinetic f ...
.


Pharmacology

The dopamine transporter is the target of
substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (aquatic environment), the earthy material that exi ...
s, dopamine releasers, transport inhibitors and
allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that a ...
s. Cocaine blocks DAT by binding directly to the transporter and reducing the rate of transport. In contrast, amphetamine enters the presynaptic neuron directly through the neuronal membrane or through DAT, competing for reuptake with dopamine. Once inside, it binds to or enters synaptic vesicles through . When amphetamine binds to TAAR1, it reduces the firing rate of the postsynaptic neuron and triggers
protein kinase A In cell biology, protein kinase A (PKA) is a family of serine-threonine kinases whose activity is dependent on cellular levels of cyclic AMP (cAMP). PKA is also known as cAMP-dependent protein kinase (). PKA has several functions in the cell, in ...
and
protein kinase C In cell biology, protein kinase C, commonly abbreviated to PKC (EC 2.7.11.13), is a family of protein kinase enzymes that are involved in controlling the function of other proteins through the phosphorylation of hydroxyl groups of serine and t ...
signaling, resulting in DAT phosphorylation. Phosphorylated DAT then either operates in reverse or withdraws into the presynaptic neuron and ceases transport. When amphetamine enters the synaptic vesicles through VMAT2, dopamine is released into the cytosol. Amphetamine also produces dopamine efflux through a second TAAR1-independent mechanism involving CAMKIIα-mediated phosphorylation of the transporter, which putatively arises from the activation of DAT-coupled L-type calcium channels by amphetamine. The dopaminergic mechanisms of each drug are believed to underlie the pleasurable feelings elicited by these substances.


Interactions

Dopamine transporter has been shown to
interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization advocating for the legal and human rights of children with intersex traits. The organization was founded in 2006 and fo ...
with: *
Alpha-synuclein Alpha-synuclein (aSyn) is a protein that in humans is encoded by the ''SNCA'' gene. It is a neuronal protein involved in the regulation of synaptic vesicle trafficking and the release of neurotransmitters. Alpha-synuclein is abundant in the brai ...
, *
PICK1 Protein Interacting with C Kinase - 1 is a protein that in humans is encoded by the ''PICK1'' gene. Function The protein encoded by this gene contains a PDZ domain, through which it interacts with protein kinase C, alpha ( PRKCA). This protei ...
, * Synaptogyrin-3, and *
TGFB1I1 Transforming growth factor beta-1-induced transcript 1 protein is a protein that in humans is encoded by the ''TGFB1I1'' gene. Often put together with and studied alongside TGFB1I1 is the mouse homologue HIC-5 ( Hydrogen Peroxide-Inducible Clone- ...
, Apart from these innate protein-protein interactions, recent studies demonstrated that viral proteins such as
HIV-1 The subtypes of HIV include two main subtypes, known as HIV type 1 (HIV-1) and HIV type 2 (HIV-2). These subtypes have distinct genetic differences and are associated with different epidemiological patterns and clinical characteristics. HIV-1 e ...
Tat protein interacts with the DAT and this binding may alter the dopamine homeostasis in HIV positive individuals which is a contributing factor for the
HIV-associated neurocognitive disorder HIV-associated neurocognitive disorders (HAND) are neurological disorders associated with HIV infection and AIDS. It is a syndrome of progressive deterioration of memory, cognition, behavior, and motor function in HIV-infected individuals during ...
s.


Ligands and modulators


Substrates

*
Dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. It is an amine synthesized ...
*
Norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic compound, organic chemical in the catecholamine family that functions in the brain and human body, body as a hormone, neurotransmitter and neuromodulator. The ...
* Substrate-type
dopamine releasing agent A dopamine releasing agent (DRA) is a type of drug which induces the release of dopamine in the Body (biology), body and/or brain. No binding selectivity, selective DRAs are currently known. However, non-selective DRAs, including norepinephrin ...
s (e.g.,
amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
) * Catecholaminergic activity enhancers (e.g.,
selegiline Selegiline, also known as L-deprenyl and sold under the brand names Eldepryl, Zelapar, and Emsam among others, is a medication which is used in the treatment of Parkinson's disease and major depressive disorder. It has also been studied and us ...
, PPAP, BPAP) * Certain
dopaminergic neurotoxin A monoamine neurotoxin, or monoaminergic neurotoxin, is a drug that selectively damages or destroys monoaminergic neurons. Monoaminergic neurons are neurons that signal via stimulation by monoamine neurotransmitters including serotonin, dopamine ...
s (e.g.,
MPTP MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) is an organic compound. It is classified as a tetrahydropyridine. It is of interest as a precursor to the monoaminergic neurotoxin MPP+, which causes permanent symptoms of Parkinson's dise ...
, 6-OHDA)


Dopamine reuptake inhibitors (DRIs)


Typical or classical cocaine-like blockers

* Amfonelic acid *
Amineptine Amineptine, formerly sold under the brand name Survector among others, is an atypical antidepressant of the tricyclic antidepressant (TCA) family. It acts as a selective and mixed dopamine reuptake inhibitor and releasing agent, and to a le ...
*
BTCP Benocyclidine, also known as benzothiophenylcyclohexylpiperidine (BTCP), is a psychoactive recreational drug of the arylcyclohexylamine class which is related to phencyclidine (PCP). It was first described in a patent application naming Marc Car ...
*
Cocaethylene Cocaethylene (ethylbenzoylecgonine) is the ethyl ester of benzoylecgonine. It is structurally similar to cocaine, which is the methyl ester of benzoylecgonine. Cocaethylene is formed by the liver in small amounts when cocaine and ethanol coexi ...
*
Cocaine Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
* JJC8-088 *
Methylenedioxypyrovalerone Methylenedioxypyrovalerone (abbreviated MDPV, and also called monkey dust) is a stimulant of the cathinone class that acts as a norepinephrine–dopamine reuptake inhibitor (NDRI). It was first developed in the 1960s by a team at Boehringer In ...
(MDPV) *
Methylphenidate Methylphenidate, sold under the brand names Ritalin ( ) and Concerta ( ) among others, is a central nervous system (CNS) stimulant used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy. It may be taken Oral adm ...
*
Orphenadrine Orphenadrine (sold under many brand names) is an anticholinergic drug of the ethanolamine antihistamine class; it is closely related to diphenhydramine. It is a muscle relaxant that is used to treat muscle pain and to help with motor control in ...
*
Pethidine Pethidine, also known as meperidine and sold under the brand name Demerol among others, is a fully synthetic opioid pain medication of the phenylpiperidine class. Synthesized in 1938 as a potential anticholinergic agent by the German chemist Ot ...
(meperidine) *
Pipradrol Pipradrol, also known by its brand name Meratran, is a mild central nervous system stimulant that acts as a norepinephrine-dopamine reuptake inhibitor. Developed in the United States in the 1940s and patented in 1953, pipradrol was initially m ...
*
RTI-55 RTI(-''4229'')-55, also called RTI-55 or iometopane, is a phenyltropane-based stimulant, psychostimulant used in scientific research and in some medical applications. This drug was first cited in 1991. RTI-55 is a non-selective dopamine reuptake ...
*
Troparil Troparil (also known as (–)-2β-Carbomethoxy-3β-phenyltropane, WIN 35,065-2, or β-CPT) is a stimulant drug used in scientific research. Troparil is a phenyltropane-based dopamine reuptake inhibitor (DRI) that is derived from methylecgonidi ...
(WIN-35065) *
WIN-35428 WIN 35,428 (β-CFT, (–)-2-β-Carbomethoxy-3-β-(4-fluorophenyl)tropane) is a stimulant drug used in scientific research. CFT is a phenyltropane based dopamine reuptake inhibitor and is structurally derived from cocaine. It is around 3-10x more ...
(β-CFT) These agents may actually act as
dopamine releasing agent A dopamine releasing agent (DRA) is a type of drug which induces the release of dopamine in the Body (biology), body and/or brain. No binding selectivity, selective DRAs are currently known. However, non-selective DRAs, including norepinephrin ...
-esque DAT
negative allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimuli. Some of them, like benzodiazepines or alcohol, function as psychoactive drugs. The site that a ...
s or "
inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse agon ...
s".


Atypical non-psychostimulant blockers

*
Armodafinil Armodafinil, sold under the brand name Nuvigil, is a wakefulness-promoting medication which is used to treat excessive daytime sleepiness associated with obstructive sleep apnea, narcolepsy, and shift work disorder. It is also used off-label ...
*
Benztropine Benzatropine ( INN), known as benztropine in the United States and Japan, is a medication used to treat movement disorders like parkinsonism and dystonia, as well as extrapyramidal side effects of antipsychotics, including akathisia. It is ...
*
Bupropion Bupropion, formerly called amfebutamone, and sold under the brand name Wellbutrin among others, is an atypical antidepressant that is indicated in the treatment of major depressive disorder, seasonal affective disorder, and to support smo ...
(but some potential for cocaine-like actions) *
GBR-12935 GBR-12935 is a piperazine derivative which is a potent and selective dopamine reuptake inhibitor. It was originally developed in its tritium, 3H isotopic labelling, radiolabelled form for the purpose of mapping the distribution of dopaminergic n ...
* JHW-007 * JJC8-091 * Mazindol * (''S'')-MK-26 *
Modafinil Modafinil, sold under the brand name Provigil among others, is a central nervous system (CNS) stimulant and wakefulness-promoting agent, eugeroic (wakefulness promoter) medication used primarily to treat narcolepsy, a sleep disorder characteri ...
(but a few cases of misuse) *
Nomifensine Nomifensine, formerly sold under the brand names Merital and Alival, is a norepinephrine–dopamine reuptake inhibitor (NDRI) drug that was developed in the 1960s by Hoechst AG (now Sanofi-Aventis), who then test marketed it in the United States ...
(but some cases of misuse) *
Phenylpiracetam Phenylpiracetam, also known as fonturacetam () and sold under the brand names Phenotropil, Actitropil, and Carphedon among others, is a psychostimulant, stimulant and nootropic medication used in Russia and certain other Eastern European countr ...
* (''R'')-Phenylpiracetam (MRZ-9547) * RDS03-94 * Rimcazole * Sibutramine *
Solriamfetol Solriamfetol, sold under the brand name Sunosi, is a wakefulness-promoting medication used in the treatment of excessive sleepiness related to narcolepsy and sleep apnea. It is taken by mouth. Common side effects of solriamfetol include hea ...
*
Tamoxifen Tamoxifen, sold under the brand name Nolvadex among others, is a selective estrogen receptor modulator used to prevent breast cancer in women and men. It is also being studied for other types of cancer. It has been used for Albright syndrome ...
*
Tesofensine Tesofensine (NS2330) is a serotonin-noradrenaline-dopamine reuptake inhibitor, serotonin–noradrenaline–dopamine reuptake inhibitor from the phenyltropane family of drugs, which is being developed for the treatment of obesity. Tesofensine was ...
*
Vanoxerine Vanoxerine is an investigational drug which is being evaluated for the treatment of heart arrhythmias and cocaine dependence. Vanoxerine is a piperazine derivative which has multiple pharmacological activities including acting as an dopamine re ...
(GBR-12909) These agents may actually act as simple competitive DAT blockers without releaser-like "inverse agonist" activity.


Unsorted blockers

*
Indatraline Indatraline hydrochloride (Lu 19-005) is an antidepressive agent and non-selective monoamine transporter inhibitor that blocks the reuptake of dopamine, norepinephrine, and serotonin with similar efficacy to cocaine. This compound may be used t ...
* PRX-14040


Dopamine releasing agents (DRAs)

* 2-Aminoindane (2-AI) * 5-Chloro-αMT *
α-Ethyltryptamine α-Ethyltryptamine (αET, AET), also known as etryptamine, is an entactogen and stimulant drug of the tryptamine family. It was originally developed and marketed as an antidepressant under the brand name Monase by Upjohn in the 1960s before bei ...
(αET) * α-Methyltryptamine (αMT) *
Aminorex Aminorex, sold under the brand names Menocil and Apiquel among others, is a weight loss (anorectic) stimulant drug. It was withdrawn from the market after it was found to cause pulmonary hypertension (PPH). In the United States, aminorex is a ...
*
Amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...
(both
dextro- Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circul ...
and
levoamphetamine Levoamphetamine is a stimulant medication which is used in the treatment of certain medical conditions. It was previously marketed by itself under the brand name Cydril, but is now available only in combination drug, combination with dextroam ...
) *
Benzylpiperazine Benzylpiperazine (BZP) is a substance often used as a recreational drug and is known to have euphoriant and stimulant properties. Several studies conducted between 2000 and 2011 found that the effects of BZP are similar to amphetamine, although ...
(BZP) *
Cathine Cathine, also known as -norpseudoephedrine or as (+)-norpseudoephedrine, is a psychoactive drug of the phenethylamine and amphetamine groups which acts as a stimulant. Along with cathinone, it is found naturally in ''Catha edulis'' (khat), and ...
*
Cathinone Cathinone (; also known as β-ketoamphetamine) is a monoamine alkaloid found in the shrub ''Catha edulis'' (khat) and is chemically similar to ephedrine, cathine, methcathinone and other amphetamines. It is probably the main contributor to t ...
*
Ephedrine Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent hypotension, low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred ...
*
Lisdexamfetamine Lisdexamfetamine, sold under the brand names Vyvanse and Elvanse among others, is a stimulant medication that is used as a treatment for attention deficit hyperactivity disorder (ADHD) in children and adults and for moderate-to-severe binge ...
(LDX) * Methylenedioxyamphetamine (MDA) *
Methylenedioxyethylamphetamine 3,4-Methylenedioxy-''N''-ethylamphetamine (MDEA; also called MDE and colloquially, Eve) is an empathogenic psychoactive drug. MDEA is a substituted amphetamine and a substituted methylenedioxyphenethylamine. MDEA acts as a serotonin, norepineph ...
(MDEA) *
Methylenedioxymethamphetamine 3,4-Methylenedioxymethamphetamine (MDMA), commonly known as ecstasy (tablet form), and molly (crystal form), is an empathogen–entactogenic drug with stimulant and minor psychedelic properties. In studies, it has been used alongside psych ...
(MDMA) *
Mephedrone Mephedrone, also known as , , and , is a synthetic stimulant drug belonging to the amphetamine and cathinone classes. It is commonly referred to by slang names such as drone, , white magic, meow meow, and bubble. Chemically, it is similar to ...
*
Methamphetamine Methamphetamine (contracted from ) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug use, recreational or Performance-enhancing substance, performance-enhancing drug and less commonly as a secon ...
*
Methylone Methylone, also known as 3,4-methylenedioxy-''N''-methylcathinone (MDMC), is an entactogen and stimulant drug of the amphetamine, cathinone, and benzodioxole families related to 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy"). It is th ...
*
Naphthylisopropylamine Naphthylaminopropane (NAP; code name PAL-287), also known as naphthylisopropylamine (NIPA), is an research chemical, experimental drug of the substituted amphetamine, amphetamine and substituted naphthylaminopropane, naphthylaminopropane famili ...
(PAL-287) *
Octopamine Octopamine (OA), also known as ''para''-octopamine and norsynephrine among synonyms, is an organic chemical closely related to norepinephrine, and synthesized biologically by a homologous pathway. Octopamine is often considered the major "fig ...
*
Pemoline Pemoline, formerly sold under the brand name Cylert among others, is a stimulant medication which was used in the treatment of attention deficit hyperactivity disorder (ADHD) and narcolepsy,- it has since been discontinued in most countries due ...
*
Phenethylamine Phenethylamine (PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans. In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace ami ...
*
Phenmetrazine Phenmetrazine, sold under the brand name Preludin among others, is a stimulant drug first chemical synthesis, synthesized in 1952 and originally used as an appetite suppressant, but withdrawn drug, withdrawn from the market in the 1980s due to ...
*
Phentermine Phentermine, sold under the brand name Adipex-P among others, is a medication used together with diet and exercise to treat obesity. It is available by itself or as the combination phentermine/topiramate. Phentermine is taken by mouth. Com ...
*
Phenylpropanolamine Phenylpropanolamine (PPA), sold under many brand names, is a sympathomimetic agent used as a decongestant and appetite suppressant. It was once common in prescription and over-the-counter cough and cold preparations. The medication is taken ...
(PPA) *
Pseudoephedrine Pseudoephedrine, sold under the brand name Sudafed among others, is a sympathomimetic medication which is used as a decongestant to treat nasal congestion. It has also been used off-label for certain other indications, like treatment of lo ...
*
Tryptamine Tryptamine is an indolamine metabolite of the essential amino acid tryptophan. The chemical structure is defined by an indole—a fused benzene and pyrrole ring, and a 2-aminoethyl group at the second carbon (third aromatic atom, with the firs ...
*
Tyramine Tyramine ( ) (also spelled tyramin), also known under several other names, is a naturally occurring trace amine derived from the amino acid tyrosine. Tyramine acts as a catecholamine releasing agent. Notably, it is unable to cross the bl ...
These agents are also known as substrate-type dopamine releasing agents and as DAT reversers.


Allosteric modulators


Positive allosteric modulators

*
Apigenin Apigenin (4′,5,7-trihydroxyflavone), found in many plants, is a flavone compound that is the aglycone of several naturally occurring glycosides. It is a yellow crystalline solid that has been used to dye wool. Apigenin is abundant in parsl ...
*
Luteolin Luteolin is a flavone, a type of flavonoid, with a yellow crystalline appearance. Luteolin is the main yellow dye from the '' Reseda luteola'' plant, used for dyeing since at least the first millennium B.C. Luteolin was first isolated in pure f ...
* SoRI-9804 (SRI-9804) * SoRI-20040 (SRI-20040)


Negative allosteric modulators

* Armesocarb (MLR-1019) *
Ibogaine Ibogaine is a psychoactive indole alkaloid derived from plants such as '' Tabernanthe iboga'', characterized by hallucinogenic and oneirogenic effects. Traditionally used by Central African foragers, it has undergone controversial research ...
* KM822 *
Mesocarb Mesocarb, sold under the brand name Sidnocarb or Sydnocarb and known by the developmental code name MLR-1017, is a psychostimulant medication which has been used in the treatment of psychiatric disorders and for a number of other indications in ...
(Sydnocarb; MLR-1017) *
MRS7292 MRS7292 is an experimental drug which acts as both a selective agonist of the adenosine A3 receptor with moderate affinity, and also a dopamine reuptake inhibitor, showing that these disparate mechanisms of action can both be produced in the sam ...
* SoRI-20041 (SRI-20041) * SRI-29574 * SRI-31142


See also


References


External links


Dopamine transporter-related Associations, Experiments, Publications and Clinical Trials
* * {{DEFAULTSORT:Dopamine Transporter Amphetamine Biology of attention deficit hyperactivity disorder Membrane proteins Neurotransmitter transporters Solute carrier family Dopamine