The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Marc G Caron - One of the best experts on this subject based on the ideXlab platform.
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Monoamine TRANSPORTERS: From Genes to Behavior
Annu. Rev. Pharmacol. Toxicol, 2003Co-Authors: Marc G CaronAbstract:s Abstract Modulation of fast neurotransmission by Monoamines is critically in-volved in numerous physiological functions and pathological conditions. Plasma membrane Monoamine transporters provide one of the most efficient mechanisms controlling functional extracellular Monoamine concentrations. These transporters for dopamine (DAT), serotonin (SERT), and norepinephrine (NET), which are expressed selectively on the corresponding neurons, are established targets of many psychostimu-lants, antidepressants, and neurotoxins. Recently, genetic animal models with targeted disruption of these transporters have become available. These mice have provided opportunities to investigate the functional importance of transporters in homeostatic control of Monoaminergic transmission and to evaluate, in an in vivo model system, their roles in physiology and pathology. The use of these mice as test subjects has been helpful in resolving several important issues on specificity and mechanisms of action of certain pharmacological agents. In the present review, we summarize recent advances in understanding the physiology and pharmacology of Monoamine transporters gained in mice with targeted genetic deletion of DAT, SERT, and NET.
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differential quantal release of histamine and 5 hydroxytryptamine from mast cells of vesicular Monoamine transporter 2 knockout mice
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Eric R Travis, Marc G Caron, Yanmin Wang, Darren J Michael, Mark R WightmanAbstract:Abstract The recent availability of mice lacking the neuronal form of the vesicular Monoamine transporter 2 (VMAT2) affords the opportunity to study its roles in storage and release. Carbon fiber microelectrodes were used to measure individual secretory events of histamine and 5-hydroxytryptamine (5-HT) from VMAT2-expressing mast cells as a model system for quantal release. VMAT2 is indispensable for Monoamine storage because mast cells from homozygous (VMAT2−/−) mice, while undergoing granule-cell fusion, do not release Monoamines. Cells from heterozygous animals (VMAT2+/−) secrete lower amounts of Monoamine per granule than cells from wild-type controls. Investigation of corelease of histamine and 5-HT from granules in VMAT2+/− cells revealed 5-HT quantal size was reduced more than that of histamine. Thus, although vesicular transport is the limiting factor determining quantal size of 5-HT and histamine release, intragranular association with the heparin matrix also plays a significant role.
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knockout of the vesicular Monoamine transporter 2 gene results in neonatal death and supersensitivity to cocaine and amphetamine
Neuron, 1997Co-Authors: Y Wang, Gary W Miller, Raul R Gainetdinov, Fabio Fumagalli, Sara R Jones, Mark R Wightman, Fei Xu, Cheryl B Bock, Marc G CaronAbstract:Abstract Vesicular Monoamine transporters are known to transport Monoamines from the cytoplasm into secretory vesicles. We have used homologous recombination to generate mutant mice lacking the vesicular Monoamine transporter 2 (VMAT2), the predominant form expressed in the brain. Newborn homozygotes die within a few days after birth, manifesting severely impaired Monoamine storage and vesicular release. In heterozygous adult mice, extracellular striatal dopamine levels, as well as K + - and amphetamine-evoked dopamine release, are diminished. The observed changes in presynaptic homeostasis are accompanied by a pronounced supersensitivity of the mice to the locomotor effects of the dopamine agonist apomorphine, the psychostimulants cocaine and amphetamine, and ethanol. Importantly, VMAT2 heterozygous mice do not develop further sensitization to repeated cocaine administration. These observations stress the importance of VMAT2 in the maintenance of presynaptic function and suggest that these mice may provide an animal model for delineating the mechanisms of vesicular release, Monoamine function, and postsynaptic sensitization associated with drug abuse.
Joanne Wang - One of the best experts on this subject based on the ideXlab platform.
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selective transport of Monoamine neurotransmitters by human plasma membrane Monoamine transporter and organic cation transporter 3
Journal of Pharmacology and Experimental Therapeutics, 2010Co-Authors: Haichuan Duan, Joanne WangAbstract:The plasma membrane Monoamine transporter (PMAT) and organic cation transporter 3 (OCT3) are the two most prominent low-affinity, high-capacity (i.e., uptake2) transporters for endogenous biogenic amines. Using the Flp-in system, we expressed human PMAT (hPMAT) and human OCT3 (hOCT3) at similar levels in human embryonic kidney 293 cells. Parallel and detailed kinetics analysis revealed distinct and seemingly complementary patterns for the two transporters in transporting Monoamine neurotransmitters. hPMAT is highly selective toward serotonin (5-HT) and dopamine, with the rank order of transport efficiency (Vmax/Km) being: dopamine, 5-HT ≫ histamine, norepinephrine, epinephrine. The substrate preference of hPMAT toward these amines is substantially driven by large (up to 15-fold) distinctions in its apparent binding affinities (Km). In contrast, hOCT3 is less selective than hPMAT toward the Monoamines, and the Vmax/Km rank order for hOCT3 is: histamine > norepinephrine, epinephrine > dopamine >5-HT. It is noteworthy that hOCT3 demonstrated comparable (≤2-fold difference) Km toward all amines, and distinctions in Vmax played an important role in determining its differential transport efficiency toward the Monoamines. Real-time reverse transcription-polymerase chain reaction revealed that hPMAT is expressed at much higher levels than hOCT3 in most human brain areas, whereas hOCT3 is selectively and highly expressed in adrenal gland and skeletal muscle. Our results suggest that hOCT3 represents a major uptake2 transporter for histamine, epinephrine, and norepinephrine. hPMAT, on the other hand, is a major uptake2 transporter for 5-HT and dopamine and may play a more important role in transporting these two neurotransmitters in the central nervous system.
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identification and characterization of a novel Monoamine transporter in the human brain
Journal of Biological Chemistry, 2004Co-Authors: Karen Engel, Mingyan Zhou, Joanne WangAbstract:Abstract Precise control of Monoamine neurotransmitter levels in the extracellular fluids of the brain is critical in maintaining efficient and robust neurotransmission. High affinity transporters in the solute carrier SLC6A family function in removing Monoamines from the neurosynaptic cleft. Emerging evidence suggests that these transporters are only one part of a system of transporters that work in concert to maintain brain homeostasis of Monoamines. Here we report the cloning and characterization of a new human plasma membrane Monoamine transporter, PMAT. The PMAT cDNA encodes a protein of 530 amino acid residues with 10–12 transmembrane segments. PMAT is not homologous to known neurotransmitter transporters but exhibits low homology to members of the equilibrative nucleoside transporter family. When expressed in Madin-Darby canine kidney cells and Xenopus laevis oocytes, PMAT efficiently transports serotonin (Km = 114 μm), dopamine (Km = 329 μm), and the neurotoxin 1-methyl-4-phenylpyridinium (Km = 33 μm). In contrast, there is no significant interaction of PMAT with nucleosides or nucleobases. PMAT-mediated Monoamine transport does not require Na+ or Cl– but appears to be sensitive to changes in membrane potential. Northern blot analysis showed that PMAT is predominantly expressed in the human brain and widely distributed in the central nervous system. These studies demonstrate that PMAT may be a novel low affinity transporter for biogenic amines, which, under certain conditions, might supplement the role of the high affinity transporters in the brain.
Gary W Miller - One of the best experts on this subject based on the ideXlab platform.
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genetic or toxicant induced disruption of vesicular Monoamine storage and global metabolic profiling in caenorhabditis elegans
Toxicological Sciences, 2021Co-Authors: Joshua M Bradner, Vrinda Kalia, Fion K Lau, Monica Sharma, Meghan L Bucher, Michelle A Johnson, Merry Chen, Douglas I Walker, Dean P Jones, Gary W MillerAbstract:The proper storage and release of Monoamines contributes to a wide range of neuronal activity. Here, we examine the effects of altered vesicular Monoamine transport in the nematode Caenorhabditis elegans. The gene cat-1 is responsible for the encoding of the vesicular Monoamine transporter (VMAT) in C. elegans and is analogous to the mammalian vesicular Monoamine transporter 2 (VMAT2). Our laboratory has previously shown that reduced VMAT2 activity confers vulnerability on catecholamine neurons in mice. The purpose of this article was to determine whether this function is conserved and to determine the impact of reduced VMAT activity in C. elegans. Here we show that deletion of cat-1/VMAT increases sensitivity to the neurotoxicant 1-methyl-4-phenylpyridinium (MPP+) as measured by enhanced degeneration of dopamine neurons. Reduced cat-1/VMAT also induces changes in dopamine-mediated behaviors. High-resolution mass spectrometry-based metabolomics in the whole organism reveals changes in amino acid metabolism, including tyrosine metabolism in the cat-1/VMAT mutants. Treatment with MPP+ disrupted tryptophan metabolism. Both conditions altered glycerophospholipid metabolism, suggesting a convergent pathway of neuronal dysfunction. Our results demonstrate the evolutionarily conserved nature of Monoamine function in C. elegans and further suggest that high-resolution mass spectrometry-based metabolomics can be used in this model to study environmental and genetic contributors to complex human disease.
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genetic or toxicant induced disruption of vesicular Monoamine storage and global metabolic profiling in caenorhabditis elegans
bioRxiv, 2020Co-Authors: Joshua M Bradner, Vrinda Kalia, Fion K Lau, Monica Sharma, Meghan L Bucher, Michelle A Johnson, Merry Chen, Douglas I Walker, Dean P Jones, Gary W MillerAbstract:The proper storage and release of Monoamines contributes to a wide range of neuronal activity. Here, we examine the effects of altered vesicular Monoamine transport in the nematode C. elegans. The gene cat-1 is responsible for the encoding of the vesicular Monoamine transporter (VMAT) in C. elegans and is analogous to the mammalian vesicular Monoamine transporter 2 (VMAT2). Our laboratory has previously shown that reduced VMAT2 activity confers vulnerability on catecholamine neurons in mice. The purpose of this paper was to determine whether this function is conserved and to determine the impact of reduced VMAT activity in C. elegans. Here we show that deletion of cat-1/VMAT increases sensitivity to the neurotoxicant 1-methyl-4-phenylpyridinium (MPP+) as measured by enhanced degeneration of dopamine neurons. Reduced cat-1/VMAT also induces changes in dopamine-mediated behaviors. High-resolution mass spectrometry-based metabolomics in the whole organism reveals changes in amino acid metabolism, including tyrosine metabolism in the cat-1/VMAT mutants. Treatment with MPP+ disrupted tryptophan metabolism. Both conditions altered glycerophospholipid metabolism, suggesting a convergent pathway of neuronal dysfunction. Our results demonstrate the evolutionarily conserved nature of Monoamine function in C. elegans and further suggest that HRMS-based metabolomics can be used in this model to study environmental and genetic contributors to complex human disease
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a fluorescent based assay for live cell spatially resolved assessment of vesicular Monoamine transporter 2 mediated neurotransmitter transport
Journal of Neuroscience Methods, 2012Co-Authors: Alison I Bernstein, Kristen A Stout, Gary W MillerAbstract:The vesicular Monoamine transporter 2 (VMAT2; Slc18a2) packages Monoamines into synaptic vesicles. Monoamine homeostasis is highly regulated and dysfunction may play a role in Parkinson's disease, Huntington's disease, drug addiction, and neuropsychiatric disorders. The primary function of VMAT2 is to sequester Monoamine neurotransmitters into vesicles for subsequent release; it also sequesters toxicants away from cytosolic sites of action. Identification of compounds that modify the action of VMAT2 may be useful as therapeutic agents for preventing or reversing Monoamine-related toxicity. Current methods for measuring VMAT2 function are unable to assess uptake in intact cells. Here, we adapted the Neurotransmitter Uptake Assay (Molecular Devices) to develop a measure of VMAT2 function in live whole cells. This assay contains a fluorescent compound, which is transported into cells by the plasma membrane Monoamine transporters and has been marketed as a rapid, high-throughput, plate reader based assay for function of these plasma membrane transporters. We demonstrate a modified version of this assay that can be used to visualize and measure transport into vesicles by VMAT2. HEK293 cell lines stably expressing the dopamine transporter and a mCherry-VMAT2 fusion protein were generated. Confocal microscopy confirmed that the fluorescent compound is transported into mCherry-positive compartments. Furthermore, the VMAT2-specific inhibitor tetrabenazine (TBZ) blocks uptake into the mCherry-positive compartment. Confocal images can be analyzed to generate a measure of VMAT2 activity. In summary, we demonstrate a method for spatially resolved analysis of VMAT2-mediated uptake in live intact cells.
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knockout of the vesicular Monoamine transporter 2 gene results in neonatal death and supersensitivity to cocaine and amphetamine
Neuron, 1997Co-Authors: Y Wang, Gary W Miller, Raul R Gainetdinov, Fabio Fumagalli, Sara R Jones, Mark R Wightman, Fei Xu, Cheryl B Bock, Marc G CaronAbstract:Abstract Vesicular Monoamine transporters are known to transport Monoamines from the cytoplasm into secretory vesicles. We have used homologous recombination to generate mutant mice lacking the vesicular Monoamine transporter 2 (VMAT2), the predominant form expressed in the brain. Newborn homozygotes die within a few days after birth, manifesting severely impaired Monoamine storage and vesicular release. In heterozygous adult mice, extracellular striatal dopamine levels, as well as K + - and amphetamine-evoked dopamine release, are diminished. The observed changes in presynaptic homeostasis are accompanied by a pronounced supersensitivity of the mice to the locomotor effects of the dopamine agonist apomorphine, the psychostimulants cocaine and amphetamine, and ethanol. Importantly, VMAT2 heterozygous mice do not develop further sensitization to repeated cocaine administration. These observations stress the importance of VMAT2 in the maintenance of presynaptic function and suggest that these mice may provide an animal model for delineating the mechanisms of vesicular release, Monoamine function, and postsynaptic sensitization associated with drug abuse.
Gregory M. Miller - One of the best experts on this subject based on the ideXlab platform.
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the emerging role of trace amine associated receptor 1 in the functional regulation of Monoamine transporters and dopaminergic activity
Journal of Neurochemistry, 2011Co-Authors: Gregory M. MillerAbstract:It is now recognized that trace amine associated-receptor 1 (TAAR1) plays a functional role in the regulation of brain Monoamines and the mediation of action of amphetamine-like psychostimulants. Accordingly, research on TAAR1 opens the door to a new avenue of approach for medications development to treat drug addiction as well as the spectrum of neuropsychiatric disorders hallmarked by aberrant regulation of brain Monoamines. This overview focuses on recent studies which reveal a role for TAAR1 in the functional regulation of Monoamine transporters and the neuronal regulatory mechanisms that modulate dopaminergic activity.
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β phenylethylamine alters Monoamine transporter function via trace amine associated receptor 1 implication for modulatory roles of trace amines in brain
Journal of Pharmacology and Experimental Therapeutics, 2008Co-Authors: Zhihua Xie, Gregory M. MillerAbstract:Brain Monoamines include common biogenic amines (dopamine, norepinephrine, and serotonin) and trace amines [beta-phenylethylamine (beta-PEA), tyramine, tryptamine, and octopamine]. Common biogenic amines are well established as neurotransmitters, but the roles and functional importance of trace amines remain elusive. Here, we re-evaluated the interaction of trace amines with trace amine-associated receptor 1 (TAAR1) and investigated effects of beta-PEA on Monoamine transporter function and influence of Monoamine autoreceptors on TAAR1 signaling. We confirmed that TAAR1 was activated by trace amines and demonstrated that TAAR1 activation by beta-PEA significantly inhibited uptake and induced efflux of [3H]dopamine, [3H]norepinephrine, and [3H]serotonin in transfected cells. In brain synaptosomes, beta-PEA significantly inhibited uptake and induced efflux of [3H]dopamine and [3H]serotonin in striatal and [3H]norepinephrine in thalamic synaptosomes of rhesus monkeys and wild-type mice, but it lacked the same effects in synaptosomes of TAAR1 knockout mice. The effect of beta-PEA on efflux was blocked by transporter inhibitors in either the transfected cells or wild-type mouse synaptosomes. We also demonstrated that TAAR1 signaling was not affected by Monoamine autoreceptors at exposure to trace amines that we show to have poor binding affinity for the autoreceptors relative to common biogenic amines. These results reveal that beta-PEA alters Monoamine transporter function via interacting with TAAR1 but not Monoamine autoreceptors. The functional profile of beta-PEA may reveal a common mechanism by which trace amines exert modulatory effects on Monoamine transporters in brain.
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rhesus monkey trace amine associated receptor 1 signaling enhancement by Monoamine transporters and attenuation by the d2 autoreceptor in vitro
Journal of Pharmacology and Experimental Therapeutics, 2007Co-Authors: Zhihua Xie, Eric J Vallender, Guolin Chen, Susan V. Westmoreland, Mary E Bahn, Hong Yang, Weidong Yao, Bertha K Madras, Gregory M. MillerAbstract:Trace amine-associated receptor 1 (TAAR1) is a G protein-coupled receptor that directly responds to endogenous Monoamines as well as amphetamine-related psychostimulants, including methamphetamine. In the present study, we demonstrate TAAR1 mRNA and protein expression in rhesus monkey brain regions associated with Monoaminergic systems, variable cellular distribution of TAAR1 in rhesus monkey brain, and TAAR1 coexpression with the dopamine transporter (DAT) in a subset of dopamine neurons in both rhesus monkey and mouse substantia nigra. On this basis, we evaluated rhesus monkey TAAR1 activation by different compounds and its functional relation with Monoamine transporters and the dopamine D2 receptor (D2) short isoform (D2s) autoreceptor in vitro using a cAMP response element-luciferase assay. TAAR1 activation by Monoamines and amphetamine-related compounds was greatly enhanced by coexpression of dopamine, norepinephrine, or serotonin transporters, and the activation enhancement was blocked by Monoamine transporter inhibitors. This enhancement did not occur in control experiments in which the dopamine D1 receptor (D1) was substituted for TAAR1. Furthermore, activation of TAAR1 by dopamine was completely inhibited by D2s when coexpressed with TAAR1, and this inhibition was blocked by the D2 antagonist raclopride. Last, dopamine activation of TAAR1 could induce c-FOS-luciferase expression but only in the presence of DAT, whereas dopamine activation of D1 resulted in equivalent c-FOS expression in the presence or absence of DAT. Together, these data reveal a broad agonist spectrum for TAAR1, a functional relation of TAAR1 with Monoamine transporters and D2s, and a mechanism by which D2 receptor drugs can influence brain Monoaminergic function and have efficacy through affecting TAAR1 signaling.
Kazuhiko Yanai - One of the best experts on this subject based on the ideXlab platform.
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predominant role of plasma membrane Monoamine transporters in Monoamine transport in 1321n1 a human astrocytoma derived cell line
Journal of Neurochemistry, 2014Co-Authors: Fumito Naganuma, Takeo Yoshikawa, Tadaho Nakamura, Tomomitsu Iida, Ryuichi Harada, Attayeb Mohsen, Yamato Miura, Kazuhiko YanaiAbstract:Monoamine neurotransmitters should be immediately removed from the synaptic cleft to avoid excessive neuronal activity. Recent studies have shown that astrocytes and neurons are involved in Monoamine removal. However, the mechanism of Monoamine transport by astrocytes is not entirely clear. We aimed to elucidate the transporters responsible for Monoamine transport in 1321N1, a human astrocytoma-derived cell line. First, we confirmed that 1321N1 cells transported dopamine, serotonin, norepinephrine, and histamine in a time- and dose-dependent manner. Kinetics analysis suggested the involvement of low-affinity Monoamine transporters, such as organic cation transporter (OCT) 2 and 3 and plasma membrane Monoamine transporter (PMAT). Monoamine transport in 1321N1 cells was not Na+/Cl− dependent but was inhibited by decynium-22, an inhibitor of low-affinity Monoamine transporters, which supported the importance of low-affinity transporters. RT-PCR assays revealed that 1321N1 cells expressed OCT3 and PMAT but no other neurotransmitter transporters. Another human astrocytoma-derived cell line, U251MG, and primary human astrocytes also exhibited the same gene expression pattern. Gene-knockdown assays revealed that 1321N1 and primary human astrocytes could transport Monoamines predominantly through PMAT and partly through OCT3. These results might indicate that PMAT and OCT3 in human astrocytes are involved in Monoamine clearance. Monoamine neurotransmitters should be immediately removed from the synaptic cleft to avoid excessive neuronal activity. Recent studies have shown that astrocytes and neurons are involved in Monoamine removal. We aimed to elucidate the transporters responsible for Monoamine transport by astrocytes in 1321N1, a human astrocytoma-derived cell line. Kinetics analysis suggested the involvement of low-affinity Monoamine transporters, e.g., organic cation transporter (OCT) 2 and 3 and plasma membrane Monoamine transporter (PMAT). Our results indicate that PMAT and OCT3 in human astrocytes are involved in Monoamine clearance.
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predominant role of plasma membrane Monoamine transporters in Monoamine transport in 1321n1 a human astrocytoma derived cell line
Journal of Neurochemistry, 2014Co-Authors: Fumito Naganuma, Takeo Yoshikawa, Tadaho Nakamura, Tomomitsu Iida, Ryuichi Harada, Attayeb Mohsen, Yamato Miura, Kazuhiko YanaiAbstract:Monoamine neurotransmitters should be immediately removed from the synaptic cleft to avoid excessive neuronal activity. Recent studies have shown that astrocytes and neurons are involved in Monoamine removal. However, the mechanism of Monoamine transport by astrocytes is not entirely clear. We aimed to elucidate the transporters responsible for Monoamine transport in 1321N1, a human astrocytoma-derived cell line. First, we confirmed that 1321N1 cells transported dopamine, serotonin, norepinephrine, and histamine in a time- and dose-dependent manner. Kinetics analysis suggested the involvement of low-affinity Monoamine transporters, such as organic cation transporter (OCT) 2 and 3 and plasma membrane Monoamine transporter (PMAT). Monoamine transport in 1321N1 cells was not Na(+) /Cl(-) dependent but was inhibited by decynium-22, an inhibitor of low-affinity Monoamine transporters, which supported the importance of low-affinity transporters. RT-PCR assays revealed that 1321N1 cells expressed OCT3 and PMAT but no other neurotransmitter transporters. Another human astrocytoma-derived cell line, U251MG, and primary human astrocytes also exhibited the same gene expression pattern. Gene-knockdown assays revealed that 1321N1 and primary human astrocytes could transport Monoamines predominantly through PMAT and partly through OCT3. These results might indicate that PMAT and OCT3 in human astrocytes are involved in Monoamine clearance.
