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Journal of Chemical Neuroanatomy Oct 2017The neurotransmitter dopamine (DA) plays a key role in several biological processes including reward, mood, motor activity and attention. Synaptic DA homeostasis is... (Review)
Review
The neurotransmitter dopamine (DA) plays a key role in several biological processes including reward, mood, motor activity and attention. Synaptic DA homeostasis is controlled by the dopamine transporter (DAT) which transports extracellular DA into the presynaptic neuron after release and regulates its availability to receptors. Many neurological disorders such as schizophrenia, bipolar disorder, Parkinson disease and attention-deficit hyperactivity disorder are associated with imbalances in DA homeostasis that may be related to DAT dysfunction. DAT is also a target of psychostimulant and therapeutic drugs that inhibit DA reuptake and lead to elevated dopaminergic neurotransmission. We have recently demonstrated the acute and chronic modulation of DA reuptake activity and DAT stability through S-palmitoylation, the linkage of a 16-carbon palmitate group to cysteine via a thioester bond. This review summarizes the properties and regulation of DAT palmitoylation and describes how it serves to affect various transporter functions. Better understanding of the role of palmitoylation in regulation of DAT function may lead to identification of therapeutic targets for modulation of DA homeostasis in the treatment of dopaminergic disorders.
Topics: Animals; Dopamine Plasma Membrane Transport Proteins; Humans; Lipoylation; Protein Processing, Post-Translational
PubMed: 28115272
DOI: 10.1016/j.jchemneu.2017.01.002 -
Science Translational Medicine May 2021Most inherited neurodegenerative disorders are incurable, and often only palliative treatment is available. Precision medicine has great potential to address this unmet...
Most inherited neurodegenerative disorders are incurable, and often only palliative treatment is available. Precision medicine has great potential to address this unmet clinical need. We explored this paradigm in dopamine transporter deficiency syndrome (DTDS), caused by biallelic loss-of-function mutations in , encoding the dopamine transporter (DAT). Patients present with early infantile hyperkinesia, severe progressive childhood parkinsonism, and raised cerebrospinal fluid dopamine metabolites. The absence of effective treatments and relentless disease course frequently leads to death in childhood. Using patient-derived induced pluripotent stem cells (iPSCs), we generated a midbrain dopaminergic (mDA) neuron model of DTDS that exhibited marked impairment of DAT activity, apoptotic neurodegeneration associated with TNFα-mediated inflammation, and dopamine toxicity. Partial restoration of DAT activity by the pharmacochaperone pifithrin-μ was mutation-specific. In contrast, lentiviral gene transfer of wild-type human complementary DNA restored DAT activity and prevented neurodegeneration in all patient-derived mDA lines. To progress toward clinical translation, we used the knockout mouse model of DTDS that recapitulates human disease, exhibiting parkinsonism features, including tremor, bradykinesia, and premature death. Neonatal intracerebroventricular injection of human using an adeno-associated virus (AAV) vector provided neuronal expression of human DAT, which ameliorated motor phenotype, life span, and neuronal survival in the substantia nigra and striatum, although off-target neurotoxic effects were seen at higher dosage. These were avoided with stereotactic delivery of AAV2.SLC6A3 gene therapy targeted to the midbrain of adult knockout mice, which rescued both motor phenotype and neurodegeneration, suggesting that targeted AAV gene therapy might be effective for patients with DTDS.
Topics: Animals; Disease Models, Animal; Dopamine Plasma Membrane Transport Proteins; Genetic Therapy; Humans; Induced Pluripotent Stem Cells; Mice; Parkinsonian Disorders; Substantia Nigra
PubMed: 34011628
DOI: 10.1126/scitranslmed.aaw1564 -
Handbook of Experimental Pharmacology 2021Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medications for psychiatric disorders, yet they leave the majority of patients without...
Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed medications for psychiatric disorders, yet they leave the majority of patients without full symptom relief. Therefore, a major research challenge is to identify novel targets for the improved treatment of these disorders. SSRIs act by blocking the serotonin transporter (SERT), the high-affinity, low-capacity, uptake-1 transporter for serotonin. Other classes of antidepressant work by blocking the norepinephrine or dopamine transporters (NET and DAT), the high-affinity, low-capacity uptake-1 transporters for norepinephrine and dopamine, or by blocking combinations of SERT, NET, and DAT. It has been proposed that uptake-2 transporters, which include organic cation transporters (OCTs) and the plasma membrane monoamine transporter (PMAT), undermine the therapeutic utility of uptake-1 acting antidepressants. Uptake-2 transporters for monoamines have low affinity for these neurotransmitters, but a high capacity to transport them. Thus, activity of these transporters may limit the increase of extracellular monoamines thought to be essential for ultimate therapeutic benefit. Here preclinical evidence supporting a role for OCT2, OCT3, and PMAT in behaviors relevant to psychiatric disorders is presented. Importantly, preclinical evidence revealing these transporters as targets for the development of novel therapeutics for psychiatric disorders is discussed.
Topics: Antidepressive Agents; Cations; Dopamine Plasma Membrane Transport Proteins; Humans; Mental Disorders; Organic Cation Transport Proteins; Serotonin Plasma Membrane Transport Proteins; Selective Serotonin Reuptake Inhibitors
PubMed: 34282486
DOI: 10.1007/164_2021_473 -
European Journal of Pharmacology Oct 2015The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however,... (Review)
Review
The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however, that these drugs produce their effects by enhancing dopamine neurotransmission in the brain, especially in limbic areas such as the nucleus accumbens, by inducing dopamine transporter-mediated reverse transport and/or blocking dopamine reuptake though the dopamine transporter. Here, we present the evidence that aside from dopamine transporter, non-dopamine transporter-mediated mechanisms also participate in psychostimulant-induced dopamine release and contribute to the behavioral effects of these drugs, such as locomotor activation and reward. Accordingly, psychostimulants could increase norepinephrine release in the prefrontal cortex, the latter then alters the firing pattern of dopamine neurons resulting in changes in action potential-dependent dopamine release. These alterations would further affect the temporal pattern of dopamine release in the nucleus accumbens, thereby modifying information processing in that area. Hence, a synaptic input to a nucleus accumbens neuron may be enhanced or inhibited by dopamine depending on its temporal relationship to dopamine release. Specific temporal patterns of dopamine release may also be required for certain forms of synaptic plasticity in the nucleus accumbens. Together, these effects induced by psychostimulants, mediated through a non-dopamine transporter-mediated mechanism involving norepinephrine and the prefrontal cortex, may also contribute importantly to the reinforcing properties of these drugs.
Topics: Action Potentials; Adrenergic Neurons; Amphetamine; Animals; Brain; Central Nervous System Stimulants; Cocaine; Dopamine; Dopamine Plasma Membrane Transport Proteins; Dopaminergic Neurons; Humans; Kinetics; Neuronal Plasticity; Norepinephrine; Nucleus Accumbens; Prefrontal Cortex
PubMed: 26209364
DOI: 10.1016/j.ejphar.2015.07.044 -
ENeuro May 2023With a wide variety of dopamine transporter (DAT) antibodies available commercially, it is important to validate which antibodies provide sufficient immunodetection for...
With a wide variety of dopamine transporter (DAT) antibodies available commercially, it is important to validate which antibodies provide sufficient immunodetection for reproducibility purpose and for accurate analysis of DAT levels and/or location. Commercially available DAT antibodies that are commonly used were tested in western blotting (WB) on wild-type (WT) and DAT-knock-out (DAT-KO) brain tissue and with immunohistology (IH) techniques against coronal slices of unilaterally lesioned 6-OHDA rats, in addition to wild-type and DAT-knock-out mice. DAT-KO mice and unilateral 6-OHDA lesions in rats were used as a negative control for DAT antibody specificity. Antibodies were tested at various concentrations and rated based on signal detection varying from no signal to optimal signal detection. Commonly used antibodies, including AB2231 and PT-22 524-1-AP, did not provide specific DAT signals in WB and IH. Although certain antibodies provided a good DAT signal, such as SC-32258, D6944, and MA5-24796, they also presented nonspecific bands in WB. Many DAT antibodies did not detect the DAT as advertised, and this characterization of DAT antibodies may provide a guide for immunodetection of DAT for molecular studies.
Topics: Rats; Mice; Animals; Dopamine Plasma Membrane Transport Proteins; Oxidopamine; Reproducibility of Results; Brain; Mice, Knockout
PubMed: 37142435
DOI: 10.1523/ENEURO.0341-22.2023 -
Journal of Neurogenetics Mar 2016The dopamine transporter (DAT) plays an important homeostatic role in the control of both the extracellular and intraneuronal concentrations of dopamine, thereby... (Review)
Review
The dopamine transporter (DAT) plays an important homeostatic role in the control of both the extracellular and intraneuronal concentrations of dopamine, thereby providing effective control over activity of dopaminergic transmission. Since brain dopamine is known to be involved in numerous neuropsychiatric disorders, investigations using mice with genetically altered DAT function and thus intensity of dopamine-mediated signaling have provided numerous insights into the pathology of these disorders and novel pathological mechanisms that could be targeted to provide new therapeutic approaches for these disorders. In this brief overview, we discuss recent investigations involving animals with genetically altered DAT function, particularly focusing on translational studies providing new insights into pathology and pharmacology of dopamine-related disorders. Perspective applications of these and newly developed models of DAT dysfunction are also discussed.
Topics: Animals; Disease Models, Animal; Dopamine Plasma Membrane Transport Proteins; Mice; Translational Research, Biomedical
PubMed: 27276191
DOI: 10.3109/01677063.2016.1144751 -
Nature Communications May 2022The dopamine transporter facilitates dopamine reuptake from the extracellular space to terminate neurotransmission. The transporter belongs to the...
The dopamine transporter facilitates dopamine reuptake from the extracellular space to terminate neurotransmission. The transporter belongs to the neurotransmitter:sodium symporter family, which includes transporters for serotonin, norepinephrine, and GABA that utilize the Na gradient to drive the uptake of substrate. Decades ago, it was shown that the serotonin transporter also antiports K, but investigations of K-coupled transport in other neurotransmitter:sodium symporters have been inconclusive. Here, we show that ligand binding to the Drosophila- and human dopamine transporters are inhibited by K, and the conformational dynamics of the Drosophila dopamine transporter in K are divergent from the apo- and Na-states. Furthermore, we find that K increases dopamine uptake by the Drosophila dopamine transporter in liposomes, and visualize Na and K fluxes in single proteoliposomes using fluorescent ion indicators. Our results expand on the fundamentals of dopamine transport and prompt a reevaluation of the impact of K on other transporters in this pharmacologically important family.
Topics: Animals; Dopamine; Dopamine Plasma Membrane Transport Proteins; Drosophila; Ion Transport; Ions; Neurotransmitter Agents; Potassium; Serotonin Plasma Membrane Transport Proteins; Sodium; Symporters
PubMed: 35508541
DOI: 10.1038/s41467-022-30154-5 -
Cells Nov 2022The dopamine transporter (DAT) is a member of the neurotransmitter:sodium symporter (NSS) family, mediating the sodium-driven reuptake of dopamine from the extracellular...
The dopamine transporter (DAT) is a member of the neurotransmitter:sodium symporter (NSS) family, mediating the sodium-driven reuptake of dopamine from the extracellular space thereby terminating dopaminergic neurotransmission. Our current structural understanding of DAT is derived from the resolutions of DAT from (dDAT). Despite extensive structural studies of purified dDAT in complex with a variety of antidepressants, psychostimulants and its endogenous substrate, dopamine, the molecular pharmacology of purified, full length dDAT is yet to be elucidated. In this study, we functionally characterized purified, full length dDAT in detergent micelles using radioligand binding with the scintillation proximity assay. We elucidate the consequences of Na and Cl binding on [H]nisoxetine affinity and use this to evaluate the binding profiles of substrates and inhibitors to the transporter. Additionally, the technique allowed us to directly determine a equilibrium binding affinity (K) for [H]dopamine to dDAT. To compare with a more native system, the affinities of specified monoamines and inhibitors was determined on dDAT, human DAT and human norepinephrine transporter expressed in COS-7 cells. With our gathered data, we established a pharmacological profile for purified, full length dDAT that will be useful for subsequent biophysical studies using dDAT as model protein for the mammalian NSS family of proteins.
Topics: Animals; Humans; Dopamine; Dopamine Plasma Membrane Transport Proteins; Drosophila melanogaster; Drosophila Proteins
PubMed: 36497070
DOI: 10.3390/cells11233811 -
Clinical and Translational Science Jun 2023Dopamine transporter (DAT) imaging is an in vivo tool to assess presynaptic dopaminergic function in the clinical practices of Parkinson's disease (PD). Current clinical...
Dopamine transporter (DAT) imaging is an in vivo tool to assess presynaptic dopaminergic function in the clinical practices of Parkinson's disease (PD). Current clinical practices focused on qualitatively visual interpretation of DAT imaging, whereas quantitative analyses are potentially more helpful when monitoring the progression of PD. Previous cross-sectional studies indicated certain motor and non-motor features were associated with striatal DAT binding, whereas limited data were reported in terms of the longitudinal correlation between clinical features of PD with striatal DAT binding. The purpose of our study is to clarify current and longitudinal correlations between striatal DAT binding and clinical measures. A total of 352 untreated PD individuals and 167 healthy controls with complete baseline clinical measures and neuroimaging data were identified from the Parkinson's Progression and Markers Initiative (PPMI) database. Patients with PD underwent DAT imaging at the screening visit and following months 12, 24, and 48. Multiple linear regression models and linear mixed-effect models were respectively conducted to investigate the cross-sectional and longitudinal correlation between clinical characteristics and DAT binding. Associations between changes in clinical characteristics and changes in DAT binding were further evaluated and the Spearman rank correlation coefficients were reported. In the cross-sectional analysis, baseline striatal DAT binding was significantly associated with the Hoehn and Yahr scale, the Movement Disorder Society-Sponsored Revision of the Unified Parkinson Disease Rating Scale (MDS-UPDRS) scores, the rigidity scores, and the axial scores in PD individuals (false discovery rate [FDR]-adjusted p = 0.0017 for all above). Patients who developed freezing of gait had lower striatal DAT binding (FDR-adjusted p = 0.0161). Healthy controls who had higher tremor scores and suffered more severe olfactory dysfunction had lower striatal DAT binding (FDR-adjusted p = 0.0257 for all above). Longitudinal analysis indicated that baseline severity of rapid-eye-movement sleep behavior disorder was significantly associated with longitudinal striatal DAT binding in patients with PD (FDR-adjusted p = 0.0120). Furthermore, changes in MDS-UPDRS scores and the State-Trait Anxiety Inventory (STAI) scores demonstrated significant correlations with changes in striatal DAT binding over 4 years (p = 0.005 and p = 0.032, respectively). Our findings clarified quantitative associations between certain motor and non-motor features with current and future striatal dopamine binding, suggesting the feasibility of using DAT images as a progression predictive marker for PD. Further studies are needed to investigate correlations between different regional dopamine binding with specific clinical features.
Topics: Humans; Parkinson Disease; Dopamine Plasma Membrane Transport Proteins; Dopamine; Cross-Sectional Studies; Gait Disorders, Neurologic
PubMed: 36915231
DOI: 10.1111/cts.13508 -
Neurochemistry International Feb 2019The dopamine transporter (DAT) plays a critical role in dopamine (DA) homeostasis by clearing transmitter from the extraneuronal space after vesicular release. DAT... (Review)
Review
The dopamine transporter (DAT) plays a critical role in dopamine (DA) homeostasis by clearing transmitter from the extraneuronal space after vesicular release. DAT serves as a site of action for a variety of addictive and therapeutic reuptake inhibitors, and transport dysfunction is associated with transmitter imbalances in disorders such as schizophrenia, attention deficit hyperactive disorder, bipolar disorder, and Parkinson disease. In this review, we describe some of the model systems that have been used for in vitro analyses of DAT structure, function and regulation, and discuss a potential relationship between transporter kinetic values and membrane cholesterol.
Topics: Animals; Attention Deficit Disorder with Hyperactivity; Dopamine; Dopamine Plasma Membrane Transport Proteins; Dopamine Uptake Inhibitors; Humans; Parkinson Disease; Schizophrenia
PubMed: 30179648
DOI: 10.1016/j.neuint.2018.08.015