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Nature Structural & Molecular Biology Jul 2023The inhibitory neurotransmitter γ-aminobutyric acid (GABA) is cleared from the synaptic cleft by the sodium- and chloride-coupled GABA transporter GAT1. Inhibition of...
The inhibitory neurotransmitter γ-aminobutyric acid (GABA) is cleared from the synaptic cleft by the sodium- and chloride-coupled GABA transporter GAT1. Inhibition of GAT1 prolongs the GABAergic signaling at the synapse and is a strategy to treat certain forms of epilepsy. In this study, we present the cryo-electron microscopy structure of Rattus norvegicus GABA transporter 1 (rGAT1) at a resolution of 3.1 Å. The structure elucidation was facilitated by epitope transfer of a fragment-antigen binding (Fab) interaction site from the Drosophila dopamine transporter (dDAT) to rGAT1. The structure reveals rGAT1 in a cytosol-facing conformation, with a linear density in the primary binding site that accommodates a molecule of GABA, a displaced ion density proximal to Na site 1 and a bound chloride ion. A unique insertion in TM10 aids the formation of a compact, closed extracellular gate. Besides yielding mechanistic insights into ion and substrate recognition, our study will enable the rational design of specific antiepileptics.
Topics: Rats; Animals; GABA Plasma Membrane Transport Proteins; Cryoelectron Microscopy; Chlorides; gamma-Aminobutyric Acid; Binding Sites
PubMed: 37400654
DOI: 10.1038/s41594-023-01011-w -
BioRxiv : the Preprint Server For... Oct 2023Parkinson's disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The...
Parkinson's disease (PD) targets some dopamine (DA) neurons more than others. Sex differences offer insights, with females more protected from DA neurodegeneration. The mammalian vesicular glutamate transporter VGLUT2 and ortholog dVGLUT have been implicated as modulators of DA neuron resilience. However, the mechanisms by which VGLUT2/dVGLUT protects DA neurons remain unknown. We discovered DA neuron dVGLUT knockdown increased mitochondrial reactive oxygen species in a sexually dimorphic manner in response to depolarization or paraquat-induced stress, males being especially affected. DA neuron dVGLUT also reduced ATP biosynthetic burden during depolarization. RNA sequencing of VGLUT DA neurons in mice and flies identified candidate genes that we functionally screened to further dissect VGLUT-mediated DA neuron resilience across PD models. We discovered transcription factors modulating dVGLUT-dependent DA neuroprotection and identified dj-1β as a regulator of sex-specific DA neuron dVGLUT expression. Overall, VGLUT protects DA neurons from PD-associated degeneration by maintaining mitochondrial health.
PubMed: 37873436
DOI: 10.1101/2023.10.02.560584 -
Brain and Behavior Jul 2023Gastrointestinal symptoms are common in Parkinson's disease (PD), but their neurophysiological correlates are not well understood. We recently reported that functional...
BACKGROUND
Gastrointestinal symptoms are common in Parkinson's disease (PD), but their neurophysiological correlates are not well understood. We recently reported that functional gastrointestinal symptoms were not associated with asymmetry per se but might be associated with lower left striatal dopamine transporter (DAT) binding. The purpose of this study was to further investigate if specific gastrointestinal symptoms associate with monoamine transporter changes in specific striatal or extrastriatal areas.
METHODS
Ninety PD patients, who underwent DAT ¹ I-FP-CIT SPECT imaging, were assessed using the MDS-Unified Parkinson's Disease Rating Scale part III, Rome III, and Wexner constipation score. DAT binding was calculated from striatal subregions using region-to-occipital cortex ratio. Voxel-wise analysis was used to assess the relationship between gastrointestinal symptoms and striatal DAT and extrastriatal serotonin transporter (SERT) binding.
RESULTS
Irritable bowel syndrome (IBS) criteria were fulfilled in 17 patients and were linked to higher ¹ I-FP-CIT binding in the right posterior putamen and adjacent areas as compared to patients without IBS. No other significant associations between gastrointestinal symptoms and DAT or SERT binding were found.
CONCLUSIONS
These findings suggest that PD patients with IBS may have higher DAT binding in the right hemisphere. This finding implicates alterations of brain neurotransmitter physiology in the gastrointestinal symptoms of PD patients.
Topics: Humans; Parkinson Disease; Dopamine Plasma Membrane Transport Proteins; Irritable Bowel Syndrome; Brain; Corpus Striatum; Serotonin Plasma Membrane Transport Proteins
PubMed: 37254594
DOI: 10.1002/brb3.3097 -
Heliyon Nov 2023Vesicular monoamine transporters (VMATs) are key regulators of neurotransmitter release responsible for controlling numerous physiological, cognitive, emotional, and... (Review)
Review
Vesicular monoamine transporters (VMATs) are key regulators of neurotransmitter release responsible for controlling numerous physiological, cognitive, emotional, and behavioral functions. They represent important therapeutic targets for numerous pathological conditions. There are two isoforms of VMAT transporter proteins that function as secondary active transporters into the vesicle for storage and release via exocytosis: VMAT1 (SLC18A1) and VMAT2 (SLC18A2) which differ in their function, quantity, and regional expression. VMAT2 has gained considerable interest as a therapeutic target and diagnostic marker. Inhibitors of VMAT2 have been used as an effective therapy for a range of pathological conditions. Additionally, the functionality and phenotypic classification of classical and nonclassical catecholaminergic neurons are identified by the presence of VMAT2 in catecholaminergic neurons. Dysregulation of VMAT2 is also implicated in many neuropsychiatric diseases. Despite the complex role of VMAT2, many aspects of its function remain unclear. Therefore, our aim is to expand our knowledge of the role of VMAT with a special focus on VMAT2 in different systems and cellular pathways which may potentially facilitate development of novel, more specific therapeutic targets. The current review provides a summary demonstrating the mechanism of action of VMAT, its functional role, and its contribution to disease progression and utilization as therapeutic targets.
PubMed: 38034713
DOI: 10.1016/j.heliyon.2023.e22413 -
Journal of Clinical PsychopharmacologyThe purpose of this study was to review the association between the SLC6A4 5-HTTLPR polymorphism and antidepressant (AD)-associated treatment emergent mania (TEM) in... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The purpose of this study was to review the association between the SLC6A4 5-HTTLPR polymorphism and antidepressant (AD)-associated treatment emergent mania (TEM) in bipolar disorder alongside starting a discussion on the merits of developing risk stratification models to guide when not to provide AD treatment for bipolar depression.
METHODS
Studies that examined the association between clinical and genetic risk factors, specifically monoaminergic transporter genetic variation, and TEM were identified. A meta-analysis was performed using the odds ratio to estimate the effect size under the Der-Simonian and Laird model.
RESULTS
Seven studies, referencing the SLC6A4 5-HTTLPR polymorphism and TEM (total N = 1578; TEM+ =594, TEM- = 984), of 142 identified articles were included. The time duration between the start of the AD to emergence of TEM ranged from 4 to 12 weeks. There was a nominally significant association between the s allele of the 5-HTTLPR polymorphism and TEM (odds ratio, 1.434; 95% confidence interval, 1.001-2.055; P = 0.0493; I2 = 52%). No studies have investigated norepinephrine or dopamine transporters.
CONCLUSION
Although the serotonin transporter genetic variation is commercially available in pharmacogenomic decision support tools, greater efforts, more broadly, should focus on complete genome-wide approaches to determine genetic variants that may contribute to TEM. Moreover, these data are exemplary to the merits of developing risk stratification models, which include both clinical and biological risk factors, to guide when not to use ADs in bipolar disorder. Future studies will need to validate new risk models that best inform the development of personalized medicine best practices treating bipolar depression.
Topics: Humans; Antidepressive Agents; Bipolar Disorder; Mania; Pharmacogenetics; Polymorphism, Genetic; Serotonin Plasma Membrane Transport Proteins
PubMed: 37683232
DOI: 10.1097/JCP.0000000000001747 -
EMBO Reports Oct 2023Monoamine transporters retrieve serotonin (SERT), dopamine (DAT), and norepinephrine (NET) from the synaptic cleft. Transporter internalization contributes to the...
Monoamine transporters retrieve serotonin (SERT), dopamine (DAT), and norepinephrine (NET) from the synaptic cleft. Transporter internalization contributes to the regulation of their surface expression. Clathrin-mediated endocytosis of plasma membrane proteins requires adaptor protein-2 (AP2), which recruits cargo to the nascent clathrin cage. However, the intracellular portions of monoamine transporters are devoid of a conventional AP2-binding site. Here, we identify a MAD2 (mitotic arrest deficient-2) interaction motif in the C-terminus of SERT, which binds the closed conformation of MAD2 and allows for the recruitment of two additional mitotic spindle assembly checkpoint (SAC) proteins, BubR1 and p31 , and of AP2. We visualize MAD2, BubR1, and p31 in dorsal raphe neurons, and depletion of MAD2 in primary serotonergic rat neurons decreases SERT endocytosis in the soma. Our findings do not only provide mechanistic insights into transporter internalization but also allow for rationalizing why SAC proteins are present in post-mitotic neurons.
Topics: Rats; Animals; Serotonin Plasma Membrane Transport Proteins; Mad2 Proteins; Nuclear Proteins; Cell Cycle Proteins; Adaptor Proteins, Signal Transducing; Endocytosis; Spindle Apparatus; Clathrin
PubMed: 37530743
DOI: 10.15252/embr.202153408 -
The Journal of Biological Chemistry Nov 2023Chloride intracellular channels (CLICs) are a family of proteins that exist in soluble and transmembrane forms. The newest discovered member of the family CLIC6 is...
Chloride intracellular channels (CLICs) are a family of proteins that exist in soluble and transmembrane forms. The newest discovered member of the family CLIC6 is implicated in breast, ovarian, lung gastric, and pancreatic cancers and is also known to interact with dopamine-(D(2)-like) receptors. The soluble structure of the channel has been resolved, but the exact physiological role of CLIC6, biophysical characterization, and the membrane structure remain unknown. Here, we aimed to characterize the biophysical properties of this channel using a patch-clamp approach. To determine the biophysical properties of CLIC6, we expressed CLIC6 in HEK-293 cells. On ectopic expression, CLIC6 localizes to the plasma membrane of HEK-293 cells. We established the biophysical properties of CLIC6 by using electrophysiological approaches. Using various anions and potassium (K) solutions, we determined that CLIC6 is more permeable to chloride-(Cl) as compared to bromide-(Br), fluoride-(F), and K ions. In the whole-cell configuration, the CLIC6 currents were inhibited after the addition of 10 μM of IAA-94 (CLIC-specific blocker). CLIC6 was also found to be regulated by pH and redox potential. We demonstrate that the histidine residue at 648 (H648) in the C terminus and cysteine residue in the N terminus (C487) are directly involved in the pH-induced conformational change and redox regulation of CLIC6, respectively. Using qRT-PCR, we identified that CLIC6 is most abundant in the lung and brain, and we recorded the CLIC6 current in mouse lung epithelial cells. Overall, we have determined the biophysical properties of CLIC6 and established it as a Cl channel.
Topics: Animals; Humans; Mice; Anions; Chloride Channels; Chlorides; Epithelial Cells; HEK293 Cells
PubMed: 37838179
DOI: 10.1016/j.jbc.2023.105349 -
BioRxiv : the Preprint Server For... Oct 2023The nematode, , is an advantageous model for studying developmental toxicology due to its homology to humans and well-defined developmental stages. Similarly to humans,...
The nematode, , is an advantageous model for studying developmental toxicology due to its homology to humans and well-defined developmental stages. Similarly to humans, utilize dopamine as a neurotransmitter to regulate motor behavior. We have previously reported behavioral deficits in a genetic model of (OK411) that lack the neurotransmitter transporter necessary for packaging dopamine into synaptic vesicles. Anecdotally, we observed these appeared to have a smaller body size, which is supported by prior studies that observed a larger body size in that lack the enzyme that catalyzes dopamine synthesis, suggesting a complex regulatory system in which dopamine mediates body size in . However, the question of whether body size abnormalities apparent in with disruptions to their dopamine system are developmental or purely based on body size remains unanswered. Here, we present data characterizing the effect of gene mutations in dopamine-related proteins on body size, development, and behavior. We analyzed that lack the ability to sequester dopamine (OK411), that overproduce dopamine (UA57), and a novel strain (MBIA) generated through crossing OK411 and UA57, which lacks the ability to sequester dopamine into vesicles and additionally endogenously overproduces dopamine. This novel strain was generated to address the hypothesis that an endogenous increase in production of dopamine can rescue deficits caused by a lack of vesicular dopamine sequestration. Compared to wild type, OK411 have shorter body lengths and behavioral deficits in early life stages. In contrast, the MBIA strain have similar body lengths to wild-type by early adulthood and display similar behavior to wild-type by early adulthood. Our data suggests that endogenously increasing the production of dopamine is able to mitigate deficits in lacking the ability to package dopamine into synaptic vesicles. These results provide evidence that the dopamine system impacts development, growth, and reproduction in .
PubMed: 37873331
DOI: 10.1101/2023.10.07.561350 -
ELife Jul 2023Midbrain dopamine (DA) neurons are key regulators of basal ganglia functions. The axonal domain of these neurons is highly complex, with a large subset of non-synaptic...
Midbrain dopamine (DA) neurons are key regulators of basal ganglia functions. The axonal domain of these neurons is highly complex, with a large subset of non-synaptic release sites and a smaller subset of synaptic terminals from which in addition to DA, glutamate or GABA are also released. The molecular mechanisms regulating the connectivity of DA neurons and their neurochemical identity are unknown. An emerging literature suggests that neuroligins, trans-synaptic cell adhesion molecules, regulate both DA neuron connectivity and neurotransmission. However, the contribution of their major interaction partners, neurexins (Nrxns), is unexplored. Here, we tested the hypothesis that Nrxns regulate DA neuron neurotransmission. Mice with conditional deletion of all Nrxns in DA neurons (DAT::NrxnsKO) exhibited normal basic motor functions. However, they showed an impaired locomotor response to the psychostimulant amphetamine. In line with an alteration in DA neurotransmission, decreased levels of the membrane DA transporter (DAT) and increased levels of the vesicular monoamine transporter (VMAT2) were detected in the striatum of DAT::NrxnsKO mice, along with reduced activity-dependent DA release. Strikingly, electrophysiological recordings revealed an increase of GABA co-release from DA neuron axons in the striatum of these mice. Together, these findings suggest that Nrxns act as regulators of the functional connectivity of DA neurons.
Topics: Mice; Animals; Dopaminergic Neurons; Synaptic Transmission; Presynaptic Terminals; Central Nervous System Stimulants; gamma-Aminobutyric Acid
PubMed: 37409563
DOI: 10.7554/eLife.87902 -
Environment International Nov 2023Previous studies have shown that F-53B exposure may be neurotoxic to animals, but there is a lack of epidemiological evidence, and its mechanism needs further...
BACKGROUND
Previous studies have shown that F-53B exposure may be neurotoxic to animals, but there is a lack of epidemiological evidence, and its mechanism needs further investigation.
METHODS
Serum F-53B concentrations and Wisconsin Card Sorting Test (WCST) were evaluated in 314 growing children from Guangzhou, China, and the association between them were analyzed. To study the developmental neurotoxicity of F-53B, experiments on sucking mice exposed via placental transfer and breast milk was performed. Maternal mice were orally exposed to 4, 40, and 400 μg/L of F-53B from postnatal day 0 (GD0) to postnatal day 21 (PND 21). Several genes and proteins related to neurodevelopment, dopamine anabolism, and synaptic plasticity were examined by qPCR and western blot, respectively, while dopamine contents were detected by ELISA kit in weaning mice.
RESULTS
The result showed that F-53B was positively associated with poor WCST performance. For example, with an interquartile range increase in F-53B, the change with 95 % confidence interval (CI) of correct response (CR), and non-perseverative errors (NPE) was -2.47 (95 % CI: -3.89, -1.05, P = 0.001), 2.78 (95 % CI: 0.79, 4.76, P = 0.007), respectively. Compared with the control group, the highest exposure group of weaning mice had a longer escape latency (35.24 s vs. 51.18 s, P = 0.034) and a lesser distance movement (34.81 % vs. 21.02 %, P < 0.001) in the target quadrant, as observed from morris water maze (MWM) test. The protein expression of brain-derived neurotrophic factor (BDNF) and growth associated protein-43 (GAP-43) levels were decreased, as compared to control (0.367-fold, P < 0.001; 0.366-fold, P < 0.001; respectively). We also observed the upregulation of dopamine transporter (DAT) (2.940-fold, P < 0.001) consistent with the trend of dopamine content (1.313-fold, P < 0.001) in the hippocampus.
CONCLUSION
Early life exposure to F-53B is associated with adverse neurobehavioral changes in developing children and weaning mice which may be modulated by dopamine-dependent synaptic plasticity.
Topics: Humans; Pregnancy; Child; Female; Animals; Mice; Alkanesulfonates; Alkanesulfonic Acids; Dopamine; Weaning; Zebrafish; Water Pollutants, Chemical; Fluorocarbons; Placenta
PubMed: 37890264
DOI: 10.1016/j.envint.2023.108272