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Son Y, Kenny TC, Khan A, Birsoy K, Hite RK. Structural basis of lipid head group entry to the Kennedy pathway by FLVCR1. Nature 2024; 629:710-716. [PMID: 38693265 DOI: 10.1038/s41586-024-07374-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 04/02/2024] [Indexed: 05/03/2024]
Abstract
Phosphatidylcholine and phosphatidylethanolamine, the two most abundant phospholipids in mammalian cells, are synthesized de novo by the Kennedy pathway from choline and ethanolamine, respectively1-6. Despite the essential roles of these lipids, the mechanisms that enable the cellular uptake of choline and ethanolamine remain unknown. Here we show that the protein encoded by FLVCR1, whose mutation leads to the neurodegenerative syndrome posterior column ataxia and retinitis pigmentosa7-9, transports extracellular choline and ethanolamine into cells for phosphorylation by downstream kinases to initiate the Kennedy pathway. Structures of FLVCR1 in the presence of choline and ethanolamine reveal that both metabolites bind to a common binding site comprising aromatic and polar residues. Despite binding to a common site, FLVCR1 interacts in different ways with the larger quaternary amine of choline in and with the primary amine of ethanolamine. Structure-guided mutagenesis identified residues that are crucial for the transport of ethanolamine, but dispensable for choline transport, enabling functional separation of the entry points into the two branches of the Kennedy pathway. Altogether, these studies reveal how FLVCR1 is a high-affinity metabolite transporter that serves as the common origin for phospholipid biosynthesis by two branches of the Kennedy pathway.
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Affiliation(s)
- Yeeun Son
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA
- BCMB Allied Program, Weill Cornell Graduate School, New York, NY, USA
| | - Timothy C Kenny
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Artem Khan
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Kıvanç Birsoy
- Laboratory of Metabolic Regulation and Genetics, The Rockefeller University, New York, NY, USA
| | - Richard K Hite
- Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
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2
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Guerra G, Segrado F, Pasanisi P, Bruno E, Lopez S, Raspagliesi F, Bianchi M, Venturelli E. Circulating choline and phosphocholine measurement by a hydrophilic interaction liquid chromatography-tandem mass spectrometry. Heliyon 2023; 9:e21921. [PMID: 38027764 PMCID: PMC10665723 DOI: 10.1016/j.heliyon.2023.e21921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 10/31/2023] [Accepted: 10/31/2023] [Indexed: 12/01/2023] Open
Abstract
Background Given the growing interest in studying the role of choline and phosphocholine in the development and progression of tumor pathology, in this study we describe the development and validation of a fast and robust method for the simultaneous analysis of choline and phosphocholine in human plasma. Methods Choline and phosphocholine quantification in human plasma was obtained using a hydrophilic interaction liquid chromatography-tandem mass spectrometry technique. Assay performance parameters were evaluated using EMA guidelines. Results Calibration curve ranged from 0.60 to 38.40 μmol/L (R2 = 0.999) and 0.08-5.43 μmol/L (R2 = 0.998) for choline and phosphocholine, respectively. The Limit Of Detection of the method was 0.06 μmol/L for choline and 0.04 μmol/L for phosphocholine. The coefficient of variation range for intra-assay precision is 2.2-4.1 % (choline) and 3.2-15 % (phosphocholine), and the inter-assay precision range is < 1-6.5 % (choline) and 6.2-20 % (phosphocholine). The accuracy of the method was below the ±20 % benchmarks at all the metabolites concentration levels. In-house plasma pool of apparently healthy adults was tested, and a mean concentration of 15.97 μmol/L for Choline and 0.34 μmol/L for Phosphocholine was quantified. Conclusions The developed method shows good reliability in quantifying Choline and Phosphocholine in human plasma for clinical purposes.
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Affiliation(s)
- Giulia Guerra
- Nutrition Research and Metabolomics Unit, Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Francesco Segrado
- Nutrition Research and Metabolomics Unit, Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Patrizia Pasanisi
- Nutrition Research and Metabolomics Unit, Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Eleonora Bruno
- Nutrition Research and Metabolomics Unit, Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Salvatore Lopez
- Unit of Oncological Gynecology, Department of Oncologycal Surgery, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Francesco Raspagliesi
- Unit of Oncological Gynecology, Department of Oncologycal Surgery, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Michela Bianchi
- Nutrition Research and Metabolomics Unit, Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Elisabetta Venturelli
- Nutrition Research and Metabolomics Unit, Department of Experimental Oncology, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
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Latif S, Kang YS. Blood-Brain Barrier Solute Carrier Transporters and Motor Neuron Disease. Pharmaceutics 2022; 14:2167. [PMID: 36297602 PMCID: PMC9608738 DOI: 10.3390/pharmaceutics14102167] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 09/22/2022] [Accepted: 10/04/2022] [Indexed: 01/21/2024] Open
Abstract
Defective solute carrier (SLC) transporters are responsible for neurotransmitter dysregulation, resulting in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). We provided the role and kinetic parameters of transporters such as ASCTs, Taut, LAT1, CAT1, MCTs, OCTNs, CHT, and CTL1, which are mainly responsible for the transport of essential nutrients, acidic, and basic drugs in blood-brain barrier (BBB) and motor neuron disease. The affinity for LAT1 was higher in the BBB than in the ALS model cell line, whereas the capacity was higher in the NSC-34 cell lines than in the BBB. Affinity for MCTs was lower in the BBB than in the NSC-34 cell lines. CHT in BBB showed two affinity sites, whereas no expression was observed in ALS cell lines. CTL1 was the main transporter for choline in ALS cell lines. The half maximal inhibitory concentration (IC50) analysis of [3H]choline uptake indicated that choline is sensitive in TR-BBB cells, whereas amiloride is most sensitive in ALS cell lines. Knowledge of the transport systems in the BBB and motor neurons will help to deliver drugs to the brain and develop the therapeutic strategy for treating CNS and neurological diseases.
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Affiliation(s)
| | - Young-Sook Kang
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Sookmyung Women’s University, 100 Cheongpa-ro 47-gil, Yongsan-gu, Seoul 04310, Korea
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4
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Donovan E, Avila C, Klausner S, Parikh V, Fenollar-Ferrer C, Blakely RD, Sarter M. Disrupted Choline Clearance and Sustained Acetylcholine Release In Vivo by a Common Choline Transporter Coding Variant Associated with Poor Attentional Control in Humans. J Neurosci 2022; 42:3426-3444. [PMID: 35232764 PMCID: PMC9034784 DOI: 10.1523/jneurosci.1334-21.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2021] [Revised: 02/20/2022] [Accepted: 02/23/2022] [Indexed: 11/21/2022] Open
Abstract
Transport of choline via the neuronal high-affinity choline transporter (CHT; SLC5A7) is essential for cholinergic terminals to synthesize and release acetylcholine (ACh). In humans, we previously demonstrated an association between a common CHT coding substitution (rs1013940; Ile89Val) and reduced attentional control as well as attenuated frontal cortex activation. Here, we used a CRISPR/Cas9 approach to generate mice expressing the I89V substitution and assessed, in vivo, CHT-mediated choline transport, and ACh release. Relative to wild-type (WT) mice, CHT-mediated clearance of choline in male and female mice expressing one or two Val89 alleles was reduced by over 80% in cortex and over 50% in striatum. Choline clearance in CHT Val89 mice was further reduced by neuronal inactivation. Deficits in ACh release, 5 and 10 min after repeated depolarization at a low, behaviorally relevant frequency, support an attenuated reloading capacity of cholinergic neurons in mutant mice. The density of CHTs in total synaptosomal lysates and neuronal plasma-membrane-enriched fractions was not impacted by the Val89 variant, indicating a selective impact on CHT function. When challenged with a visual disruptor to reveal attentional control mechanisms, Val89 mice failed to adopt a more conservative response bias. Structural modeling revealed that Val89 may attenuate choline transport by altering conformational changes of CHT that support normal transport rates. Our findings support the view that diminished sustained cholinergic signaling capacity underlies perturbed attentional performance in individuals expressing CHT Val89. The CHT Val89 mouse serves as a valuable model to study heritable risk for cognitive disorders arising from cholinergic dysfunction.SIGNIFICANCE STATEMENT Acetylcholine (ACh) signaling depends on the functional capacity of the neuronal choline transporter (CHT). Previous research demonstrated that humans expressing the common CHT coding variant Val89 exhibit attentional vulnerabilities and attenuated fronto-cortical activation during attention. Here, we find that mice engineered to express the Val89 variant exhibit reduced CHT-mediated choline clearance and a diminished capacity to sustain ACh release. Additionally, Val89 mice lack cognitive flexibility in response to an attentional challenge. These findings provide a mechanistic and cognitive framework for interpreting the attentional phenotype associated with the human Val89 variant and establish a model that permits a more invasive interrogation of CNS effects as well as the development of therapeutic strategies for those, including Val89 carriers, with presynaptic cholinergic perturbations.
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Affiliation(s)
- Eryn Donovan
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
| | - Cassandra Avila
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
| | - Sarah Klausner
- Department of Psychology, University of Michigan, Ann Arbor, Michigan 48109
| | - Vinay Parikh
- Department of Psychology & Neuroscience Program, Temple University, Philadelphia, Pennsylvania 19122
| | - Cristina Fenollar-Ferrer
- Laboratory of Molecular Genetics, Section of Human Genetics, National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland 20892
| | - Randy D Blakely
- Stiles-Nicholson Brain Institute and Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, Florida 33458
| | - Martin Sarter
- Department of Psychology, Neuroscience Program and Department of Neurology, University of Michigan, Ann Arbor, Michigan 48109
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Petrov K, Wierbowski BM, Liu J, Salic A. Distinct Cation Gradients Power Cholesterol Transport at Different Key Points in the Hedgehog Signaling Pathway. Dev Cell 2020; 55:314-327.e7. [PMID: 32860743 DOI: 10.1016/j.devcel.2020.08.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 05/07/2020] [Accepted: 07/30/2020] [Indexed: 01/20/2023]
Abstract
Cholesterol plays two critical roles in Hedgehog signaling, a fundamental pathway in animal development and cancer: it covalently modifies the Sonic hedgehog (SHH) ligand, restricting its release from producing cells, and directly activates Smoothened in responding cells. In both contexts, a membrane protein related to bacterial RND transporters regulates cholesterol: Dispatched1 controls release of cholesterylated SHH, and Patched1 antagonizes Smoothened activation by cholesterol. The mechanism and driving force for eukaryotic RND proteins, including Dispatched1 and Patched1, are unknown. Here, we show that Dispatched1 acts enzymatically to catalyze SHH release. Dispatched1 uses the energy of the plasma membrane Na+ gradient, thus functioning as an SHH/Na+ antiporter. In contrast, Patched1 repression of Smoothened requires the opposing K+ gradient. Our results clarify the transporter activity of essential eukaryotic RND proteins and demonstrate that the two main cation gradients of animal cells differentially power cholesterol transport at two crucial steps in the Hedgehog pathway.
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Gyimesi G, Pujol-Giménez J, Kanai Y, Hediger MA. Sodium-coupled glucose transport, the SLC5 family, and therapeutically relevant inhibitors: from molecular discovery to clinical application. Pflugers Arch 2020; 472:1177-1206. [PMID: 32767111 PMCID: PMC7462921 DOI: 10.1007/s00424-020-02433-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 06/24/2020] [Accepted: 07/02/2020] [Indexed: 02/06/2023]
Abstract
Sodium glucose transporters (SGLTs) belong to the mammalian solute carrier family SLC5. This family includes 12 different members in human that mediate the transport of sugars, vitamins, amino acids, or smaller organic ions such as choline. The SLC5 family belongs to the sodium symporter family (SSS), which encompasses transporters from all kingdoms of life. It furthermore shares similarity to the structural fold of the APC (amino acid-polyamine-organocation) transporter family. Three decades after the first molecular identification of the intestinal Na+-glucose cotransporter SGLT1 by expression cloning, many new discoveries have evolved, from mechanistic analysis to molecular genetics, structural biology, drug discovery, and clinical applications. All of these advances have greatly influenced physiology and medicine. While SGLT1 is essential for fast absorption of glucose and galactose in the intestine, the expression of SGLT2 is largely confined to the early part of the kidney proximal tubules, where it reabsorbs the bulk part of filtered glucose. SGLT2 has been successfully exploited by the pharmaceutical industry to develop effective new drugs for the treatment of diabetic patients. These SGLT2 inhibitors, termed gliflozins, also exhibit favorable nephroprotective effects and likely also cardioprotective effects. In addition, given the recent finding that SGLT2 is also expressed in tumors of pancreas and prostate and in glioblastoma, this opens the door to potential new therapeutic strategies for cancer treatment by specifically targeting SGLT2. Likewise, further discoveries related to the functional association of other SGLTs of the SLC5 family to human pathologies will open the door to potential new therapeutic strategies. We furthermore hope that the herein summarized information about the physiological roles of SGLTs and the therapeutic benefits of the gliflozins will be useful for our readers to better understand the molecular basis of the beneficial effects of these inhibitors, also in the context of the tubuloglomerular feedback (TGF), and the renin-angiotensin system (RAS). The detailed mechanisms underlying the clinical benefits of SGLT2 inhibition by gliflozins still warrant further investigation that may serve as a basis for future drug development.
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Affiliation(s)
- Gergely Gyimesi
- Membrane Transport Discovery Lab, Department of Nephrology and Hypertension, and Department of Biomedical Research, Inselspital, University of Bern, Kinderklinik, Office D845, Freiburgstrasse 15, CH-3010, Bern, Switzerland
| | - Jonai Pujol-Giménez
- Membrane Transport Discovery Lab, Department of Nephrology and Hypertension, and Department of Biomedical Research, Inselspital, University of Bern, Kinderklinik, Office D845, Freiburgstrasse 15, CH-3010, Bern, Switzerland
| | - Yoshikatsu Kanai
- Department of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Matthias A Hediger
- Membrane Transport Discovery Lab, Department of Nephrology and Hypertension, and Department of Biomedical Research, Inselspital, University of Bern, Kinderklinik, Office D845, Freiburgstrasse 15, CH-3010, Bern, Switzerland.
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7
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Iyer KA, Alix K, Eltit JM, Solis E, Pan X, Argade MD, Khatri S, De Felice LJ, Sweet DH, Schulte MK, Dukat M. Multi-modal antidepressant-like action of 6- and 7-chloro-2-aminodihydroquinazolines in the mouse tail suspension test. Psychopharmacology (Berl) 2019; 236:2093-2104. [PMID: 30805668 DOI: 10.1007/s00213-019-05203-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Accepted: 02/14/2019] [Indexed: 01/08/2023]
Abstract
RATIONALE 2-Amino-6-chloro-3,4-dihydroquinazoline (e.g., A6CDQ) represents a novel putative antidepressant originally thought to act through a 5-HT3 serotonin receptor antagonist mechanism. Here, we investigated this further by examining a positional isomer of A6CDQ (i.e., A7CDQ). MATERIALS AND METHODS 5-HT3 receptor and transporter activity (uptake-1 and uptake-2) were investigated using a variety of in vitro assays and the in vivo mouse tail suspension test (TST). RESULTS Although A7CDQ binds at 5-HT3 receptors with low affinity (Ki = 1975 nM) compared to A6CDQ (Ki = 80 nM), it retained 5-HT3 receptor antagonist action (IC50 = 5.77 and 0.26 μM, respectively). In the mouse TST A7CDQ produced antidepressant-like actions (ED50 = 0.09 mg/kg) comparable to that of A6CDQ. In addition, A6CDQ was found to be a 5-HT releasing agent (Km = 2.8 μM) at hSERT and a reuptake inhibitor (IC50 = 1.8 μM) at hNET, whereas A7CDQ was a weak reuptake inhibitor (Km = 43.6 μM) at SERT but a releasing agent (EC50 = 3.3 μM) at hNET. Moreover, A6CDQ and A7CDQ were potent inhibitors of uptake-2 (e.g.; OCT3 IC50 = 3.9 and 5.9 μM, respectively). CONCLUSIONS A simple shift of a substituent in a common quinazoline scaffold from one position to another (i.e., a chloro group from the 6- to the 7-position) resulted in a common action in the TST but via a somewhat different mechanism. A6CDQ and A7CDQ might represent the first members of a new class of potential antidepressants with a unique multi-modal mechanism of action.
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Affiliation(s)
- Kavita A Iyer
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA
| | - Katie Alix
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA
| | - Jose M Eltit
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Ernesto Solis
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Xiaolei Pan
- Department of Pharmaceutics, School of Pharmacy, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Malaika D Argade
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA
| | - Shailesh Khatri
- Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of Sciences, Philadelphia, PA, 19104, USA
| | - Louis J De Felice
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Douglas H Sweet
- Department of Pharmaceutics, School of Pharmacy, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Marvin K Schulte
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, Kasiska Division of Health Sciences, Idaho State University, Pocatello, ID, 83209, USA
| | - Małgorzata Dukat
- Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, PO Box 980540, Richmond, VA, 23298-540, USA.
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Liu R, Crawford J, Callahan PM, Terry AV, Constantinidis C, Blake DT. Intermittent Stimulation of the Nucleus Basalis of Meynert Improves Working Memory in Adult Monkeys. Curr Biol 2017; 27:2640-2646.e4. [PMID: 28823679 PMCID: PMC5759307 DOI: 10.1016/j.cub.2017.07.021] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 06/07/2017] [Accepted: 07/11/2017] [Indexed: 10/19/2022]
Abstract
Acetylcholine in the neocortex is critical for executive function [1-3]. Degeneration of cholinergic neurons in aging and Alzheimer's dementia is commonly treated with cholinesterase inhibitors [4-7]; however, these are modestly effective and are associated with side effects that preclude effective dosing in many patients [8]. Electrical activation of the nucleus basalis (NB) of Meynert, the source of neocortical acetylcholine [9, 10], provides a potential method of improving cholinergic activation [11, 12]. Here we tested whether NB stimulation would improve performance of a working memory task in a nonhuman primate model. Unexpectedly, intermittent stimulation proved to be most beneficial (60 pulses per second, for 20 s every minute), whereas continuous stimulation often impaired performance. Pharmacological experiments confirmed that the effects depended on cholinergic activation. Donepezil, a cholinesterase inhibitor, restored performance in animals impaired by continuous stimulation but did not improve performance further during intermittent stimulation. Intermittent stimulation was rendered ineffective by either nicotinic or muscarinic receptor antagonists. In the months after stimulation began, performance also improved in sessions without stimulation. Our results reveal that intermittent NB stimulation can improve working memory, a finding that has implications for restoring cognitive function in aging and Alzheimer's dementia.
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Affiliation(s)
- Ruifeng Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China; Brain and Behavior Discovery Institute, Department of Neurology, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA
| | - Jonathan Crawford
- Brain and Behavior Discovery Institute, Department of Neurology, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA
| | - Patrick M Callahan
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA
| | - Alvin V Terry
- Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA
| | - Christos Constantinidis
- Department of Neurobiology and Anatomy, Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - David T Blake
- Brain and Behavior Discovery Institute, Department of Neurology, Medical College of Georgia, Augusta University, 1120 15th Street, Augusta, GA 30912, USA.
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Dobrovinskaya O, Valencia-Cruz G, Castro-Sánchez L, Bonales-Alatorre EO, Liñan-Rico L, Pottosin I. Cholinergic Machinery as Relevant Target in Acute Lymphoblastic T Leukemia. Front Pharmacol 2016; 7:290. [PMID: 27630569 PMCID: PMC5005329 DOI: 10.3389/fphar.2016.00290] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 08/18/2016] [Indexed: 12/17/2022] Open
Abstract
Various types of non-neuronal cells, including tumors, are able to produce acetylcholine (ACh), which acts as an autocrine/paracrine growth factor. T lymphocytes represent a key component of the non-neuronal cholinergic system. T cells-derived ACh is involved in a stimulation of their activation and proliferation, and acts as a regulator of immune response. The aim of the present work was to summarize the data about components of cholinergic machinery in T lymphocytes, with an emphasis on the comparison of healthy and leukemic T cells. Cell lines derived from acute lymphoblastic leukemias of T lineage (T-ALL) were found to produce a considerably higher amount of ACh than healthy T lymphocytes. Additionally, ACh produced by T-ALL is not efficiently hydrolyzed, because acetylcholinesterase (AChE) activity is drastically decreased in these cells. Up-regulation of muscarinic ACh receptors was also demonstrated at expression and functional level, whereas nicotinic ACh receptors seem to play a less important role and not form functional channels in cells derived from T-ALL. We hypothesized that ACh over-produced in T-ALL may act as an autocrine growth factor and play an important role in leukemic clonal expansion through shaping of intracellular Ca2+ signals. We suggest that cholinergic machinery may be attractive targets for new drugs against T-ALL. Specifically, testing of high affinity antagonists of muscarinic ACh receptors as well as antagomiRs, which interfere with miRNAs involved in the suppression of AChE expression, may be the first choice options.
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Affiliation(s)
- Oxana Dobrovinskaya
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, México
| | - Georgina Valencia-Cruz
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, México
| | - Luis Castro-Sánchez
- Centro Universitario de Investigaciones Biomédicas, Universidad de ColimaColima, México; Consejo Nacional de Ciencia y TecnologíaMéxico City, México
| | | | - Liliana Liñan-Rico
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, México
| | - Igor Pottosin
- Centro Universitario de Investigaciones Biomédicas, Universidad de Colima Colima, México
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10
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Bertron JL, Ennis EA, Tarr CJ, Wright J, Dickerson JW, Locuson CW, Blobaum AL, Rook JM, Blakely RD, Lindsley CW. Optimization of the choline transporter (CHT) inhibitor ML352: Development of VU6001221, an improved in vivo tool compound. Bioorg Med Chem Lett 2016; 26:4637-4640. [PMID: 27575469 DOI: 10.1016/j.bmcl.2016.08.062] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 08/17/2016] [Accepted: 08/19/2016] [Indexed: 12/11/2022]
Abstract
This Letter describes the further lead optimization of the CHT inhibitor probe, ML352 (VU0476201), and the development of VU6001221, an improved in vivo tool. A multi-dimensional optimization effort encountered steep SAR, and ultimately, subtle tuning of the electronics of the central phenyl core provided VU6001221, a CHT inhibitor with comparable potency for choline uptake inhibition as ML352, yet improved PK and CNS penetration. Moreover, VU6001221 enabled evaluation, for the first time, of a CHT inhibitor in a standard preclinical rodent cognition model, novel object recognition (NOR). We observed VU6001221 to elicit a dose-responsive increase in NOR, raising the possibility of agonism of synaptic α7 nicotinic ACh receptors by elevated extracellular choline, that if confirmed would represent a novel molecular strategy to enhance cognition.
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Affiliation(s)
- Jeanette L Bertron
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Elizabeth A Ennis
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Christopher J Tarr
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jane Wright
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jonathan W Dickerson
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Charles W Locuson
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Anna L Blobaum
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Jerri M Rook
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Randy D Blakely
- FAU Brain Institute, Charles E. Schmidt College of Medicine, Florida Atlantic University, Jupiter, FL 33458, USA.
| | - Craig W Lindsley
- Vanderbilt Center for Neuroscience Drug Discovery, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Chemistry, Vanderbilt University, Nashville, TN 37232, USA.
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Solis E Jr, Suyama JA, Lazenka MF, DeFelice LJ, Negus SS, Blough BE, Banks ML. Dissociable effects of the prodrug phendimetrazine and its metabolite phenmetrazine at dopamine transporters. Sci Rep 2016; 6:31385. [PMID: 27514281 DOI: 10.1038/srep31385] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Accepted: 07/19/2016] [Indexed: 11/28/2022] Open
Abstract
Phendimetrazine (PDM) is a clinically available anorectic and a candidate pharmacotherapy for cocaine addiction. PDM has been hypothesized to function as a prodrug that requires metabolism to the amphetamine-like monoamine transporter substrate phenmetrazine (PM) to produce its pharmacological effects; however, whether PDM functions as an inactive prodrug or has pharmacological activity on its own remains unclear. The study aim was to determine PDM pharmacological mechanisms using electrophysiological, neurochemical, and behavioral procedures. PDM blocked the endogenous basal hDAT (human dopamine transporter) current in voltage-clamped (−60 mV) oocytes consistent with a DAT inhibitor profile, whereas its metabolite PM induced an inward hDAT current consistent with a DAT substrate profile. PDM also attenuated the PM-induced inward current during co-application, providing further evidence that PDM functions as a DAT inhibitor. PDM increased nucleus accumbens dopamine levels and facilitated electrical brain stimulation reinforcement within 10 min in rats, providing in vivo evidence supporting PDM pharmacological activity. These results demonstrate that PDM functions as a DAT inhibitor that may also interact with the pharmacological effects of its metabolite PM. Overall, these results suggest a novel mechanism for PDM therapeutic effects via initial PDM DAT inhibition followed by PM DAT substrate-induced dopamine release.
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12
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Ennis EA, Blakely RD. Choline on the Move: Perspectives on the Molecular Physiology and Pharmacology of the Presynaptic Choline Transporter. Adv Pharmacol 2016; 76:175-213. [PMID: 27288078 DOI: 10.1016/bs.apha.2016.03.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Genetic, biochemical, physiological, and pharmacological approaches have advanced our understanding of cholinergic biology for over 100 years. High-affinity choline uptake (HACU) was one of the last features of cholinergic signaling to be defined at a molecular level, achieved through the cloning of the choline transporter (CHT, SLC5A7). In retrospect, the molecular era of CHT studies initiated with the identification of hemicholinium-3 (HC-3), a potent, competitive CHT antagonist, though it would take another 30 years before HC-3, in radiolabeled form, was used by Joseph Coyle's laboratory to identify and monitor the dynamics of CHT proteins. Though HC-3 studies provided important insights into CHT distribution and regulation, another 15 years would pass before the structure of CHT genes and proteins were identified, a full decade after the cloning of most other neurotransmitter-associated transporters. The availability of CHT gene and protein probes propelled the development of cell and animal models as well as efforts to gain insights into how human CHT gene variation affects the risk for brain and neuromuscular disorders. Most recently, our group has pursued a broadening of CHT pharmacology, elucidating novel chemical structures that may serve to advance cholinergic diagnostics and medication development. Here we provide a short review of the transformation that has occurred in HACU research and how such advances may promote the development of novel therapeutics.
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Affiliation(s)
- E A Ennis
- Vanderbilt University School of Medicine, Nashville, TN, United States
| | - R D Blakely
- Vanderbilt University School of Medicine, Nashville, TN, United States.
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Ennis EA, Wright J, Retzlaff CL, McManus OB, Lin Z, Huang X, Wu M, Li M, Daniels JS, Lindsley CW, Hopkins CR, Blakely RD. Identification and characterization of ML352: a novel, noncompetitive inhibitor of the presynaptic choline transporter. ACS Chem Neurosci 2015; 6:417-27. [PMID: 25560927 PMCID: PMC4367188 DOI: 10.1021/cn5001809] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
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The high-affinity choline transporter
(CHT) is the rate-limiting
determinant of acetylcholine (ACh) synthesis, yet the transporter
remains a largely undeveloped target for the detection and manipulation
of synaptic cholinergic signaling. To expand CHT pharmacology, we
pursued a high-throughput screen for novel CHT-targeted small molecules
based on the electrogenic properties of transporter-mediated choline
transport. In this effort, we identified five novel, structural classes
of CHT-specific inhibitors. Chemical diversification and functional
analysis of one of these classes identified ML352 as a high-affinity
(Ki = 92 nM) and selective CHT inhibitor.
At concentrations that fully antagonized CHT in transfected cells
and nerve terminal preparations, ML352 exhibited no inhibition of
acetylcholinesterase (AChE) or cholineacetyltransferase (ChAT) and
also lacked activity at dopamine, serotonin, and norepinephrine transporters,
as well as many receptors and ion channels. ML352 exhibited noncompetitive
choline uptake inhibition in intact cells and synaptosomes and reduced
the apparent density of hemicholinium-3 (HC-3) binding sites in membrane
assays, suggesting allosteric transporter interactions. Pharmacokinetic
studies revealed limited in vitro metabolism and
significant CNS penetration, with features predicting rapid clearance.
ML352 represents a novel, potent, and specific tool for the manipulation
of CHT, providing a possible platform for the development of cholinergic
imaging and therapeutic agents.
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Affiliation(s)
| | | | | | - Owen B. McManus
- Johns Hopkins University Ion Channel Center, Baltimore, Maryland 21205, United States
| | - Zhinong Lin
- Johns Hopkins University Ion Channel Center, Baltimore, Maryland 21205, United States
| | - Xiaofang Huang
- Johns Hopkins University Ion Channel Center, Baltimore, Maryland 21205, United States
| | - Meng Wu
- Johns Hopkins University Ion Channel Center, Baltimore, Maryland 21205, United States
| | - Min Li
- Johns Hopkins University Ion Channel Center, Baltimore, Maryland 21205, United States
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14
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Bollinger SR, Engers DW, Ennis EA, Wright J, Locuson CW, Lindsley CW, Blakely RD, Hopkins CR. Synthesis and structure-activity relationships of a series of 4-methoxy-3-(piperidin-4-yl)oxy benzamides as novel inhibitors of the presynaptic choline transporter. Bioorg Med Chem Lett 2015; 25:1757-60. [PMID: 25801932 DOI: 10.1016/j.bmcl.2015.02.058] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 02/19/2015] [Accepted: 02/23/2015] [Indexed: 11/23/2022]
Abstract
The synthesis and SAR of 4-methoxy-3-(piperidin-4-yl) benzamides identified after a high-throughput screen of the MLPCN library is reported. SAR was explored around the 3-piperidine substituent as well as the amide functionality of the reported compounds. Starting from the initial lead compounds, 1-7, iterative medicinal chemistry efforts led to the identification of ML352 (10m). ML352 represents a potent and selective inhibitor of CHT based on a drug-like scaffold.
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15
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Abstract
Background The ion transport stoichiometry (q) of electrogenic transporters is an important determinant of their function. q can be determined by the reversal potential (Erev) if the transporter under study is the only electrogenic transport mechanism or a specific inhibitor is available. An alternative approach is to calculate delta reversal potential (ΔErev) by altering the concentrations of the transported substrates. This approach is based on the hypothesis that the contributions of other channels and transporters on the membrane to Erev are additive. However, Erev is a complicated function of the sum of different conductances rather than being additive. Results We propose a new delta current (ΔI) method based on a simplified model for electrogenic secondary active transport by Heinz (Electrical Potentials in Biological Membrane Transport, 1981). ΔI is the difference between two currents obtained from altering the external concentration of a transported substrate thereby eliminating other currents without the need for a specific inhibitor. q is determined by the ratio of ΔI at two different membrane voltages (V1 and V2) where q = 2RT/(F(V2 –V1))ln(ΔI2/ΔI1) + 1. We tested this ΔI methodology in HEK-293 cells expressing the elctrogenic SLC4 sodium bicarbonate cotransporters NBCe2-C and NBCe1-A, the results were consistent with those obtained with the Erev inhibitor method. Furthermore, using computational simulations, we compared the estimates of q with the ΔErev and ΔI methods. The results showed that the ΔErev method introduces significant error when other channels or electrogenic transporters are present on the membrane and that the ΔI equation accurately calculates the stoichiometric ratio. Conclusions We developed a ΔI method for estimating transport stoichiometry of electrogenic transporters based on the Heinz model. This model reduces to the conventional reversal potential method when the transporter under study is the only electrogenic transport process in the membrane. When there are other electrogenic transport pathways, ΔI method eliminates their contribution in estimating q. Computational simulations demonstrated that the ΔErev method introduces significant error when other channels or electrogenic transporters are present and that the ΔI equation accurately calculates the stoichiometric ratio. This new ΔI method can be readily extended to the analysis of other electrogenic transporters in other tissues.
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Affiliation(s)
- Xuesi M Shao
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 USA
| | - Liyo Kao
- Division of Nephrology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 USA
| | - Ira Kurtz
- Division of Nephrology, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 USA ; Brain Research Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095 USA
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Horie A, Ishida K, Watanabe Y, Shibata K, Hashimoto Y. Membrane transport mechanisms of choline in human intestinal epithelial LS180 cells. Biopharm Drug Dispos 2014; 35:532-42. [DOI: 10.1002/bdd.1917] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Revised: 08/27/2014] [Accepted: 09/15/2014] [Indexed: 01/11/2023]
Affiliation(s)
- Asuka Horie
- Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama, 2630 Sugitani; Toyama 930-0194 Japan
| | - Kazuya Ishida
- Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama, 2630 Sugitani; Toyama 930-0194 Japan
| | - Yuri Watanabe
- Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama, 2630 Sugitani; Toyama 930-0194 Japan
| | - Kaito Shibata
- Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama, 2630 Sugitani; Toyama 930-0194 Japan
| | - Yukiya Hashimoto
- Graduate School of Medicine and Pharmaceutical Sciences; University of Toyama, 2630 Sugitani; Toyama 930-0194 Japan
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17
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Abstract
This article summarizes molecular properties of the high-affinity choline transporter (CHT1) with reference to the historical background focusing studies performed in laboratories of the author. CHT1 is present on the presynaptic terminal of cholinergic neurons, and takes up choline which is the precursor of acetylcholine. The Na(+)-dependent uptake of choline by CHT1 is the rate-limiting step for synthesis of acetylcholine. CHT1 is the integral membrane protein with 13 transmembrane segments, belongs to the Na(+)/glucose co-transporter family (SLC5), and has 20-25% homology with members of this family. A single nucleotide polymorphism (SNP) for human CHT1 has been identified, which has a replacement from isoleucine to valine in the third transmembrane segment and shows the choline uptake activity of 50-60% as much as that of wild-type CHT1. The proportion of this SNP is high among Asians. Possible importance of choline diet for those with this SNP was discussed.
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Affiliation(s)
- Tatsuya Haga
- Tokyo University, 7-3-1 Hongo, Tokyo 113-8654, Japan
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18
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Kolanos R, Solis E, Sakloth F, De Felice LJ, Glennon RA. "Deconstruction" of the abused synthetic cathinone methylenedioxypyrovalerone (MDPV) and an examination of effects at the human dopamine transporter. ACS Chem Neurosci 2013; 4:1524-9. [PMID: 24116392 PMCID: PMC3867964 DOI: 10.1021/cn4001236] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 10/09/2013] [Indexed: 11/30/2022] Open
Abstract
Synthetic cathinones, β-keto analogues of amphetamine (or, more correctly, of phenylalkylamines), represent a new and growing class of abused substances. Several such analogues have been demonstrated to act as dopamine (DA) releasing agents. Methylenedioxypyrovalerone (MDPV) was the first synthetic cathinone shown to act as a cocaine-like DA reuptake inhibitor. MDPV and seven deconstructed analogues were examined to determine which of MDPV's structural features account(s) for uptake inhibition. In voltage-clamped (-60 mV) Xenopus oocytes transfected with the human DA transporter (hDAT), all analogues elicited inhibitor-like behavior shown as hDAT-mediated outward currents. Using hDAT-expressing mammalian cells we determined the affinities of MDPV and its analogues to inhibit uptake of [3H]DA by hDAT that varied over a broad range (IC50 values ca. 135 to >25,000 nM). The methylenedioxy group of MDPV made a minimal contribution to affinity, the carbonyl group and a tertiary amine are more important, and the extended α-alkyl group seems most important. Either a tertiary amine, or the extended α-alkyl group (but not both), are required for the potent nature of MDPV as an hDAT inhibitor.
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Affiliation(s)
- Renata Kolanos
- Department
of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Ernesto Solis
- Department
of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Farhana Sakloth
- Department
of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Louis J. De Felice
- Department
of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298, United States
| | - Richard A. Glennon
- Department
of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond, Virginia 23298, United States
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19
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: transporters. Br J Pharmacol 2013; 170:1706-96. [PMID: 24528242 PMCID: PMC3892292 DOI: 10.1111/bph.12450] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Transporters are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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20
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Cameron KN, Kolanos R, Solis E, Glennon RA, De Felice LJ. Bath salts components mephedrone and methylenedioxypyrovalerone (MDPV) act synergistically at the human dopamine transporter. Br J Pharmacol 2013; 168:1750-7. [PMID: 23170765 DOI: 10.1111/bph.12061] [Citation(s) in RCA: 94] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 10/20/2012] [Accepted: 11/09/2012] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND AND PURPOSE Bath salts is the street name for drug combinations that contain synthetic cathinone analogues, among them possibly mephedrone (MEPH) and certainly methylenedioxypyrovalerone (MDPV). In animal studies, cathinone and certain cathinone analogues release dopamine (DA), similar to the action of amphetamine (AMPH) and methamphetamine (METH). AMPH and METH act on the human DA transporter (hDAT); thus, we investigated MEPH and MDPV acting at hDAT. EXPERIMENTAL APPROACH We recorded electrical currents mediated by hDAT expressed in Xenopus laevis oocytes and exposed to: DA, METH, a known hDAT stimulant and DA releaser, MEPH, MDPV, MEPH + MDPV, or cocaine, a known hDAT inhibitor. KEY RESULTS DA, METH and MEPH induce an inward current (depolarizing) when the oocyte is held near the resting potential (-60 mV), therefore acting as excitatory hDAT substrates. Structurally analogous MDPV induces an outward (hyperpolarizing) current similar to cocaine, therefore acting as an inhibitory non-substrate blocker. CONCLUSIONS AND IMPLICATIONS Two components of bath salts, MEPH and MDPV, produce opposite effects at hDAT that are comparable with METH and cocaine, respectively. In our assay, MEPH is nearly as potent as METH; however, MDPV is much more potent than cocaine and its effect is longer lasting. When applied in combination, MEPH exhibits faster kinetics than MDPV, viz., the MEPH depolarizing current occurs seconds before the slower MDPV hyperpolarizing current. Bath salts containing MEPH (or a similar drug) and MDPV might then be expected initially to release DA and subsequently prevent its reuptake via hDAT. Such combined action possibly underlies some of the reported effects of bath salts abuse.
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Affiliation(s)
- Krasnodara N Cameron
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA
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21
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Holmstrand EC, Lund D, Cherian AK, Wright J, Martin RF, Ennis EA, Stanwood GD, Sarter M, Blakely RD. Transgenic overexpression of the presynaptic choline transporter elevates acetylcholine levels and augments motor endurance. Neurochem Int 2013; 73:217-28. [PMID: 24274995 DOI: 10.1016/j.neuint.2013.11.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 11/11/2013] [Accepted: 11/13/2013] [Indexed: 10/26/2022]
Abstract
The hemicholinium-3 (HC-3) sensitive, high-affinity choline transporter (CHT) sustains cholinergic signaling via the presynaptic uptake of choline derived from dietary sources or from acetylcholinesterase (AChE)-mediated hydrolysis of acetylcholine (ACh). Loss of cholinergic signaling capacity is associated with cognitive and motor deficits in humans and in animal models. Whereas genetic elimination of CHT has revealed the critical nature of CHT in maintaining ACh stores and sustaining cholinergic signaling, the consequences of elevating CHT expression have yet to be studied. Using bacterial artificial chromosome (BAC)-mediated transgenic methods, we generated mice with integrated additional copies of the mouse Slc5a7 gene. BAC-CHT mice are viable, appear to develop normally, and breed at wild-type (WT) rates. Biochemical studies revealed a 2 to 3-fold elevation in CHT protein levels in the CNS and periphery, paralleled by significant increases in [(3)H]HC-3 binding and synaptosomal choline transport activity. Elevations of ACh in the BAC-CHT mice occurred without compensatory changes in the activity of either choline acetyltransferase (ChAT) or AChE. Immunohistochemistry for CHT in BAC-CHT brain sections revealed markedly elevated CHT expression in the cell bodies of cholinergic neurons and in axons projecting to regions known to receive cholinergic innervation. Behaviorally, BAC-CHT mice exhibited diminished fatigue and increased speeds on the treadmill test without evidence of increased strength. Finally, BAC-CHT mice displayed elevated horizontal activity in the open field test, diminished spontaneous alteration in the Y-maze, and reduced time in the open arms of the elevated plus maze. Together, these studies provide biochemical, pharmacological and behavioral evidence that CHT protein expression and activity can be elevated beyond that seen in wild-type animals. BAC-CHT mice thus represent a novel tool to examine both the positive and negative impact of constitutively elevated cholinergic signaling capacity.
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Affiliation(s)
- Ericka C Holmstrand
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - David Lund
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Ajeesh Koshy Cherian
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA; Department of Neuroscience, University of Michigan, Ann Arbor, MI, USA
| | - Jane Wright
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Rolicia F Martin
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Elizabeth A Ennis
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Gregg D Stanwood
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Martin Sarter
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA; Department of Neuroscience, University of Michigan, Ann Arbor, MI, USA
| | - Randy D Blakely
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN, USA; Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, TN, USA.
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22
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Cameron K, Kolanos R, Vekariya R, De Felice L, Glennon RA. Mephedrone and methylenedioxypyrovalerone (MDPV), major constituents of "bath salts," produce opposite effects at the human dopamine transporter. Psychopharmacology (Berl) 2013; 227:493-9. [PMID: 23371489 DOI: 10.1007/s00213-013-2967-2] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 01/04/2013] [Indexed: 10/27/2022]
Abstract
RATIONALE Psychoactive "bath salts" represent a relatively new drug of abuse combination that was placed in Schedule I in October 2011. Two common ingredients of bath salts include the cathinone analogs: mephedrone and methylenedioxypyrovalerone (MDPV). The mechanism of action of these synthetic cathinone analogs has not been well investigated. MATERIALS AND METHODS Because cathinone and methcathinone are known to act as releasing agents at the human dopamine transporter (hDAT), mephedrone and MDPV were investigated at hDAT expressed in Xenopus oocytes. RESULTS Whereas mephedrone was found to have the signature of a dopamine-releasing agent similar to methamphetamine or methcathinone, MDPV behaved as a cocaine-like reuptake inhibitor of dopamine. CONCLUSIONS Mephedrone and MDPV produce opposite electrophysiological signatures through hDAT expressed in oocytes. Implications are that the combination (as found in bath salts) might produce effects similar to a combination of methamphetamine and cocaine.
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24
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Rengstl D, Diat O, Klein R, Kunz W. Influence of chain length and double bond on the aqueous behavior of choline carboxylate soaps. Langmuir 2013; 29:2506-2519. [PMID: 23368901 DOI: 10.1021/la304431c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In preceding studies, we demonstrated that choline carboxylates ChC(m) with alkyl chain lengths of m = 12 - 18 are highly water-soluble (for m = 12, soluble up to 93 wt % soap and 0 °C). In addition, choline soaps are featured by an extraordinary lyotropic phase behavior. With decreasing water concentration, the following phases were found: micellar phase (L(1)), discontinuous cubic phase (I(1)' and I(1)"), hexagonal phase (H(1)), bicontinuous cubic phase (V(1)), and lamellar phase (L(α)). The present work is also focused on the lyotropic phase behavior of choline soaps but with shorter alkyl chains or different alkyl chain properties. We have investigated the aqueous phase behavior of choline soaps with C(8) and C(10) chain-lengths (choline octanoate and choline decanoate) and with a C(18) chain-length with a cis-double bond (choline oleate). We found that choline decanoate follows the lyotropic phase behavior of the longer-chain homologues mentioned above. Choline octanoate in water shows no discontinuous cubic phases, but an extended, isotropic micellar solution phase. In addition, choline octanoate is at the limit between a surfactant and a hydrotrope. The double bond in choline oleate leads also to a better solubility in water and a decrease of the solubilization temperature. It also influences the Gaussian curvature of the aggregates which results in a loss of discontinuous cubic phases in the binary phase diagram. The different lyotropic mesophases were identified by the penetration scan technique with polarizing light microscope and visual observations. To clarify the structural behavior small (SAXS) and wide (WAXS) angle X-ray scattering were performed. To further characterize the extended, isotropic micellar solution phase in the binary phase diagram of choline octanoate viscosity and conductivity measurements were also carried out.
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Affiliation(s)
- Doris Rengstl
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstrasse 31, D-93040 Regensburg, Germany
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25
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Butkiewicz M, Lowe EW Jr, Mueller R, Mendenhall JL, Teixeira PL, Weaver CD, Meiler J. Benchmarking ligand-based virtual High-Throughput Screening with the PubChem database. Molecules 2013; 18:735-56. [PMID: 23299552 DOI: 10.3390/molecules18010735] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 10/11/2012] [Accepted: 12/17/2012] [Indexed: 01/04/2023] Open
Abstract
With the rapidly increasing availability of High-Throughput Screening (HTS) data in the public domain, such as the PubChem database, methods for ligand-based computer-aided drug discovery (LB-CADD) have the potential to accelerate and reduce the cost of probe development and drug discovery efforts in academia. We assemble nine data sets from realistic HTS campaigns representing major families of drug target proteins for benchmarking LB-CADD methods. Each data set is public domain through PubChem and carefully collated through confirmation screens validating active compounds. These data sets provide the foundation for benchmarking a new cheminformatics framework BCL::ChemInfo, which is freely available for non-commercial use. Quantitative structure activity relationship (QSAR) models are built using Artificial Neural Networks (ANNs), Support Vector Machines (SVMs), Decision Trees (DTs), and Kohonen networks (KNs). Problem-specific descriptor optimization protocols are assessed including Sequential Feature Forward Selection (SFFS) and various information content measures. Measures of predictive power and confidence are evaluated through cross-validation, and a consensus prediction scheme is tested that combines orthogonal machine learning algorithms into a single predictor. Enrichments ranging from 15 to 101 for a TPR cutoff of 25% are observed.
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Okuda T, Osawa C, Yamada H, Hayashi K, Nishikawa S, Ushio T, Kubo Y, Satou M, Ogawa H, Haga T. Transmembrane topology and oligomeric structure of the high-affinity choline transporter. J Biol Chem 2012; 287:42826-34. [PMID: 23132865 DOI: 10.1074/jbc.m112.405027] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The high-affinity choline transporter CHT1 mediates choline uptake essential for acetylcholine synthesis in cholinergic nerve terminals. CHT1 belongs to the Na(+)/glucose cotransporter family (SLC5), which is postulated to have a common 13-transmembrane domain core; however, no direct experimental evidence for CHT1 transmembrane topology has yet been reported. We examined the transmembrane topology of human CHT1 using cysteine-scanning analysis. Single cysteine residues were introduced into the putative extra- and intracellular loops and probed for external accessibility for labeling with a membrane-impermeable, sulfhydryl-specific biotinylating reagent in intact cells expressing these mutants. The results provide experimental evidence for a topological model of a 13-transmembrane domain protein with an extracellular amino terminus and an intracellular carboxyl terminus. We also constructed a three-dimensional homology model of CHT1 based on the crystal structure of the bacterial Na(+)/galactose cotransporter, which supports our conclusion of CHT1 transmembrane topology. Furthermore, we examined whether CHT1 exists as a monomer or oligomer. Chemical cross-linking induces the formation of a higher molecular weight form of CHT1 on the cell surface in HEK293 cells. Two different epitope-tagged CHT1 proteins expressed in the same cells can be co-immunoprecipitated. Moreover, co-expression of an inactive mutant I89A with the wild type induces a dominant-negative effect on the overall choline uptake activity. These results indicate that CHT1 forms a homo-oligomer on the cell surface in cultured cells.
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Affiliation(s)
- Takashi Okuda
- Department of Pharmacology, Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato-ku, Tokyo, Japan.
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27
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Mustafa I, Elkamel A, Lohi A, Chen P, Elnashaie SS, Ibrahim G. Application of continuation method and bifurcation for the acetylcholine neurocycle considering partial dissociation of acetic acid. Comput Chem Eng 2012. [DOI: 10.1016/j.compchemeng.2012.07.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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28
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Ruggiero A, Wright J, Ferguson SM, Lewis M, Emerson K, Iwamoto H, Ivy MT, Holmstrand EC, Ennis EA, Weaver CD, Blakely RD. Nonoisotopic assay for the presynaptic choline transporter reveals capacity for allosteric modulation of choline uptake. ACS Chem Neurosci 2012; 3:767-81. [PMID: 23077721 PMCID: PMC3474274 DOI: 10.1021/cn3000718] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Accepted: 07/09/2012] [Indexed: 11/29/2022] Open
Abstract
Current therapies to enhance CNS cholinergic function rely primarily on extracellular acetylcholinesterase (AChE) inhibition, a pharmacotherapeutic strategy that produces dose-limiting side effects. The Na(+)-dependent, high-affinity choline transporter (CHT) is an unexplored target for cholinergic medication development. Although functional at the plasma membrane, CHT at steady-state is localized to synaptic vesicles such that vesicular fusion can support a biosynthetic response to neuronal excitation. To identify allosteric potentiators of CHT activity, we mapped endocytic sequences in the C-terminus of human CHT, identifying transporter mutants that exhibit significantly increased transport function. A stable HEK-293 cell line was generated from one of these mutants (CHT LV-AA) and used to establish a high-throughput screen (HTS) compatible assay based on the electrogenic nature of the transporter. We established that the addition of choline to these cells, at concentrations appropriate for high-affinity choline transport at presynaptic terminals, generates a hemicholinium-3 (HC-3)-sensitive, membrane depolarization that can be used for the screening of CHT inhibitors and activators. Using this assay, we discovered that staurosporine increased CHT LV-AA choline uptake activity, an effect mediated by a decrease in choline K(M) with no change in V(max). As staurosporine did not change surface levels of CHT, nor inhibit HC-3 binding, we propose that its action is directly or indirectly allosteric in nature. Surprisingly, staurosporine reduced choline-induced membrane depolarization, suggesting that increased substrate coupling to ion gradients, arising at the expense of nonstoichiometric ion flow, accompanies a shift of CHT to a higher-affinity state. Our findings provide a new approach for the identification of CHT modulators that is compatible with high-throughput screening approaches and presents a novel model by which small molecules can enhance substrate flux through enhanced gradient coupling.
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Affiliation(s)
- Alicia
M. Ruggiero
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - Jane Wright
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - Shawn M. Ferguson
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - Michelle Lewis
- Vanderbilt Institute
of Chemical
Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6304, United States
| | - Katie
S. Emerson
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - Hideki Iwamoto
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - Michael T. Ivy
- Department of Biological Sciences, Tennessee State University, Nashville, Tennessee 37209-1561,
United States
| | - Ericka C. Holmstrand
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - Elizabeth. A. Ennis
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
| | - C. David Weaver
- Vanderbilt Institute
of Chemical
Biology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-6304, United States
- Department
of Pharmacology, Vanderbilt University School of Medicine, Nashville,
Tennessee 37232-6600, United States
| | - Randy D. Blakely
- Center for Molecular
Neuroscience,
Department of Pharmacology, Vanderbilt University School
of Medicine, Nashville, Tennessee 37232-8548, United
States
- Department of Psychiatry, Vanderbilt
University School of Medicine, Nashville,
Tennessee 37232-8548, United States
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29
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Rodriguez-Menchaca AA, Solis E, Cameron K, De Felice LJ. S(+)amphetamine induces a persistent leak in the human dopamine transporter: molecular stent hypothesis. Br J Pharmacol 2012; 165:2749-57. [PMID: 22014068 DOI: 10.1111/j.1476-5381.2011.01728.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Wherever they are located, dopamine transporters (DATs) clear dopamine (DA) from the extracellular milieu to help regulate dopaminergic signalling. Exposure to amphetamine (AMPH) increases extracellular DA in the synaptic cleft, which has been ascribed to DAT reverse transport. Increased extracellular DA prolongs postsynaptic activity and reinforces abuse and hedonic behaviour. EXPERIMENTAL APPROACH Xenopus laevis oocytes expressing human (h) DAT were voltage-clamped and exposed to DA, R(-)AMPH, or S(+)AMPH. KEY RESULTS At -60mV, near neuronal resting potentials, S(+)AMPH induced a depolarizing current through hDAT, which after removing the drug, persisted for more than 30 min. This persistent leak in the absence of S(+)AMPH was in contrast to the currents induced by R(-)AMPH and DA, which returned to baseline immediately after their removal. Our data suggest that S(+)AMPH and Na(+) carry the initial S(+)AMPH-induced current, whereas Na+ and Cl(-) carry the persistent leak current. We propose that the persistent current results from the internal action of S(+)AMPH on hDAT because the temporal effect was consistent with S(+)AMPH influx, and intracellular S(+)AMPH activated the effect. The persistent current was dependent on Na(+) and was blocked by cocaine. Intracellular injection of S(+)AMPH also activated a DA-induced persistent leak current. CONCLUSIONS AND IMPLICATIONS We report a hitherto unknown action of S(+)AMPH on hDAT that potentially affects AMPH-induced DA release. We propose that internal S(+)AMPH acts as a molecular stent that holds the transporter open even after external S(+)AMPH is removed. Amphetamine-induced persistent leak currents are likely to influence dopaminergic signalling, DA release mechanisms, and amphetamine abuse.
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Affiliation(s)
- Aldo A Rodriguez-Menchaca
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
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30
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Solis E, Zdravkovic I, Tomlinson ID, Noskov SY, Rosenthal SJ, De Felice LJ. 4-(4-(dimethylamino)phenyl)-1-methylpyridinium (APP+) is a fluorescent substrate for the human serotonin transporter. J Biol Chem 2012; 287:8852-63. [PMID: 22291010 DOI: 10.1074/jbc.m111.267757] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Monoamine transporters terminate synaptic neurotransmission and are molecular targets for antidepressants and psychostimulants. Fluorescent reporters can monitor real-time transport and are amenable for high-throughput screening. However, until now, their use has mostly been successful to study the catecholamine transporters but not the serotonin (5HT) transporter. Here, we use fluorescence microscopy, electrophysiology, pharmacology, and molecular modeling to compare fluorescent analogs of 1-methyl-4-phenylpyridinium (MPP(+)) as reporters for the human serotonin transporter (hSERT) in single cells. The fluorescent substrate 4-(4-(dimethylamino)phenyl)-1-methylpyridinium (APP(+)) exhibits superior fluorescence uptake in hSERT-expressing HEK293 cells than other MPP(+) analogs tested. APP(+) uptake is Na(+)- and Cl(-)-dependent, displaced by 5HT, and inhibited by fluoxetine, suggesting APP(+) specifically monitors hSERT activity. ASP(+), which was previously used to study catecholamine transporters, is 10 times less potent than APP(+) at inhibiting 5HT uptake and has minimal hSERT-mediated uptake. Furthermore, in hSERT-expressing oocytes voltage-clamped to -60 mV, APP(+) induced fluoxetine-sensitive hSERT-mediated inward currents, indicating APP(+) is a substrate, whereas ASP(+) induced hSERT-mediated outward currents and counteracted 5HT-induced hSERT currents, indicating ASP(+) possesses activity as an inhibitor. Extra-precise ligand receptor docking of APP(+) and ASP(+) in an hSERT homology model showed both ASP(+) and APP(+) docked favorably within the active region; accordingly, comparable concentrations are required to elicit their opposite electrophysiological responses. We conclude APP(+) is better suited than ASP(+) to study hSERT transport fluorometrically.
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Affiliation(s)
- Ernesto Solis
- Graduate Training Program in Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee 23235, USA.
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31
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Mustafa I, Elkamel A, Chen P, Ibrahim G, Elnashaie S. Effect of cholineacetyltransferase activity and choline recycle ratio on diffusion-reaction modeling, bifurcation and chaotic behavior of acetylcholine neurocycle and their relation to Alzheimer's and Parkinson's diseases. Chem Eng Sci 2012. [DOI: 10.1016/j.ces.2011.08.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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32
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Abstract
Cholinergic neurons are endowed with a high-affinity choline uptake system for efficient synthesis of acetylcholine at the presynaptic terminals. The high-affinity choline transporter CHT1 is responsible for choline uptake, the rate-limiting step in acetylcholine synthesis. However, endogenous physiological factors that affect CHT1 expression or function and consequently regulate the acetylcholine synthesis rate are essentially unknown. Here we demonstrate that extracellular substrate decreases the cell-surface expression of CHT1 in rat brain synaptosomes, primary cultures from the basal forebrain, and mammalian cell lines transfected with CHT1. Extracellular choline rapidly decreases cell-surface CHT1 expression by accelerating its internalization, a process that is mediated by a dynamin-dependent endocytosis pathway in HEK293 cells. Specific inhibitor hemicholinium-3 decreases the constitutive internalization rate and thereby increases cell-surface CHT1 expression. We also demonstrate that the constitutive internalization of CHT1 depends on extracellular pH in cultured cells. Our results collectively suggest that the internalization of CHT1 is induced by extracellular substrate, providing a novel feedback mechanism for the regulation of acetylcholine synthesis at the cholinergic presynaptic terminals.
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33
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Longpré JP, Gagnon DG, Coady MJ, Lapointe JY. The actual ionic nature of the leak current through the Na+/glucose cotransporter SGLT1. Biophys J 2010; 98:231-9. [PMID: 20338844 DOI: 10.1016/j.bpj.2009.10.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 10/07/2009] [Accepted: 10/08/2009] [Indexed: 11/28/2022] Open
Abstract
Expression of the Na(+)/glucose cotransporter SGLT1 in Xenopus oocytes is characterized by a phlorizin-sensitive leak current (in the absence of glucose) that was originally called a "Na(+) leak" and represents some 5-10% of the maximal Na(+)/glucose cotransport current. We analyzed the ionic nature of the leak current using a human SGLT1 mutant (C292A) displaying a threefold larger leak current while keeping a reversal potential (V(R)) of approximately -15 mV as observed for wt SGLT1. V(R) showed only a modest negative shift when extracellular Na(+) concentration ([Na(+)](o)) was lowered and it was completely insensitive to changes in extracellular Cl(-). When extracellular pH (pH(o)) was decreased from 7.5 to 6.5 and 5.5, V(R) shifted by +15 and +40 mV, respectively, indicating that protons may be the main charge carrier at low pH(o) but other ions must be involved at pH(o) 7.5. In the presence of 15 mM [Na(+)](o) (pH(o) = 7.5), addition of 75 mM of either Na(+), Li(+), Cs(+), or K(+) generated similar increases in the leak current amplitude. This observation, which was confirmed with wt SGLT1, indicates a separate pathway for the leak current with respect to the cotransport current. This means that, contrary to previous beliefs, the leak current cannot be accounted for by the translocation of the Na-loaded and glucose-free cotransporter. Using chemical modification and different SGLT1 mutants, a relationship was found between the cationic leak current and the passive water permeability suggesting that water and cations may share a common pathway through the cotransporter.
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Affiliation(s)
- Jean-Philippe Longpré
- Groupe d'Etude des Protéines Membranaires, Département de Physique, Université de Montréal, Montréal, Québec, Canada
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34
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Papke RL, Stokes C. Working with OpusXpress: methods for high volume oocyte experiments. Methods 2010; 51:121-33. [PMID: 20085813 DOI: 10.1016/j.ymeth.2010.01.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 01/13/2010] [Accepted: 01/13/2010] [Indexed: 11/17/2022] Open
Abstract
OpusXpress is a semi-automated system for high throughput voltage clamp recording from Xenopus oocytes. We participated in the development process for this system and were the only laboratory to field test a prototype. Subsequently, we obtained an early production model that we have used on a regular basis for the last seven years, conducting many thousands of experiments, publishing extensively, and carrying out collaborative research in drug discovery. In this article, we relate our experience with the OpusXpress recording system and large volume oocyte handling. We provide our standard operating procedures and outline the organization of our successful team. Some of our advice is specific to researchers fortunate enough to have access to an OpusXpress system, but most of it is applicable to any group using Xenopus oocytes for the heterologous expression of ion channels.
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Affiliation(s)
- Roger L Papke
- Department of Pharmacology and Therapeutics, University of Florida, College of Medicine, Gainesville, FL 32610, USA.
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35
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de Castro BM, De Jaeger X, Martins-Silva C, Lima RD, Amaral E, Menezes C, Lima P, Neves CM, Pires RG, Gould TW, Welch I, Kushmerick C, Guatimosim C, Izquierdo I, Cammarota M, Rylett RJ, Gomez MV, Caron MG, Oppenheim RW, Prado MA, Prado VF. The vesicular acetylcholine transporter is required for neuromuscular development and function. Mol Cell Biol 2009; 29:5238-50. [PMID: 19635813 DOI: 10.1128/MCB.00245-09] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The vesicular acetylcholine (ACh) transporter (VAChT) mediates ACh storage by synaptic vesicles. However, the VAChT-independent release of ACh is believed to be important during development. Here we generated VAChT knockout mice and tested the physiological relevance of the VAChT-independent release of ACh. Homozygous VAChT knockout mice died shortly after birth, indicating that VAChT-mediated storage of ACh is essential for life. Indeed, synaptosomes obtained from brains of homozygous knockouts were incapable of releasing ACh in response to depolarization. Surprisingly, electrophysiological recordings at the skeletal-neuromuscular junction show that VAChT knockout mice present spontaneous miniature end-plate potentials with reduced amplitude and frequency, which are likely the result of a passive transport of ACh into synaptic vesicles. Interestingly, VAChT knockouts exhibit substantial increases in amounts of choline acetyltransferase, high-affinity choline transporter, and ACh. However, the development of the neuromuscular junction in these mice is severely affected. Mutant VAChT mice show increases in motoneuron and nerve terminal numbers. End plates are large, nerves exhibit abnormal sprouting, and muscle is necrotic. The abnormalities are similar to those of mice that cannot synthesize ACh due to a lack of choline acetyltransferase. Our results indicate that VAChT is essential to the normal development of motor neurons and the release of ACh.
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36
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Mustafa I, Elkamel A, Ibrahim G, Chen P, Elnashaie S. Effect of choline and acetate substrates on bifurcation and chaotic behavior of acetylcholine neurocycle and Alzheimer's and Parkinson's diseases. Chem Eng Sci 2009. [DOI: 10.1016/j.ces.2009.01.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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37
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Darna M, Schmutz I, Richter K, Yelamanchili SV, Pendyala G, Höltje M, Albrecht U, Ahnert-Hilger G. Time of Day-dependent Sorting of the Vesicular Glutamate Transporter to the Plasma Membrane. J Biol Chem 2009; 284:4300-7. [DOI: 10.1074/jbc.m805480200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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38
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Mustafa I, Ibrahim G, Elkamel A, Elnashaie S, Chen P. Non-linear feedback modeling and bifurcation of the acetylcholine neurocycle and its relation to Alzheimer's and Parkinson's diseases. Chem Eng Sci 2009. [DOI: 10.1016/j.ces.2008.09.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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39
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Misawa H, Fujigaya H, Nishimura T, Moriwaki Y, Okuda T, Kawashima K, Nakata K, Ruggiero AM, Blakely RD, Nakatsu F, Ohno H. Aberrant trafficking of the high-affinity choline transporter in AP-3-deficient mice. Eur J Neurosci 2008; 27:3109-17. [PMID: 18554297 DOI: 10.1111/j.1460-9568.2008.06268.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The high-affinity choline transporter (CHT) is expressed in cholinergic neurons and efficiently transported to axon terminals where it controls the rate-limiting step in acetylcholine synthesis. Recent studies have shown that the majority of CHT is unexpectedly localized on synaptic vesicles (SV) rather than the presynaptic plasma membrane, establishing vesicular CHT trafficking as a basis for activity-dependent CHT regulation. Here, we analyse the intracellular distribution of CHT in the adaptor protein-3 (AP-3)-deficient mouse model mocha. In the mocha mouse, granular structures in cell bodies are intensely labelled with CHT antibody, indicating possible deficits in CHT trafficking from the cell body to the axon terminal. Western blot analyses reveal that CHT on SV in mocha mice is decreased by 30% compared with wild-type mice. However, no significant difference in synaptosomal choline uptake activity is detected, consistent with the existence of a large reservoir pool for CHT. To further characterize CHT trafficking, we established a PC12D-CHT cell line. In this line, CHT is found associated with a subpopulation of synaptophysin-positive synaptic-like microvesicles (SLMV). The amounts of CHT detected on SLMV are greatly reduced by treating the cell with agents that halt AP-dependent membrane trafficking. These results demonstrate that APs have important functions for CHT trafficking in neuronal cells.
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Affiliation(s)
- Hidemi Misawa
- Department of Pharmacology, Kyoritsu University of Pharmacy, Tokyo 105-8512, Japan.
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40
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Tomlinson ID, Chang J, Iwamoto H, De Felice LJ, Blakely RD, Rosenthal SJ. Targeting the human serotonin transporter (hSERT) with quantum dots. Proc SPIE Int Soc Opt Eng 2008; 6866:nihpa155701. [PMID: 19936040 DOI: 10.1117/12.782801] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
In this paper we report our work on the development of a human serotonin transporter (hSERT) antagonist that can be conjugated to quantum dots. This approach has been used to target and visualize the human serotonin transporter protein (hSERT). We demonstrate that labeling is blocked by the addition of high affinity hSERT antagonists such as paroxetine. This approach may be useful for the development of fluorescent assays to study the location and temporal dynamics of biogenic amine transporters and also holds promise for the development of plate-based high throughput assays used to identify novel transporter antagonists.
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Affiliation(s)
- I D Tomlinson
- Department of Chemistry,Vanderbilt University, Station B 311822, Nashville, Tennessee, 37235-1822
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41
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Coady MJ, Wallendorff B, Bourgeois F, Charron F, Lapointe JY. Establishing a definitive stoichiometry for the Na+/monocarboxylate cotransporter SMCT1. Biophys J 2007; 93:2325-31. [PMID: 17526579 PMCID: PMC1965447 DOI: 10.1529/biophysj.107.108555] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Several different stoichiometries have been proposed for the Na(+)/monocarboxylate cotransporter SMCT1, including variable Na(+)/substrate stoichiometry. In this work, we have definitively established an invariant 2:1 cotransport stoichiometry for SMCT1. By using two independent means of assay, we first showed that SMCT1 exhibits a 2:1 stoichiometry for Na(+)/lactate cotransport. Radiolabel uptake experiments proved that, unlike lactate, propionic acid diffuses passively through oocyte membranes and, consequently, propionate is a poor candidate for stoichiometric determination by these methods. Although we previously determined SMCT1 stoichiometry by measuring reversal potentials, this technique produced erroneous values, because SMCT1 simultaneously mediates both an inwardly rectifying cotransport current and an outwardly rectifying anionic leak current; the leak current predominates in the range where reversal potentials are observed. We therefore employed a method that compared the effect of halving the external Na(+) concentration to the effect of halving the external substrate concentration on zero-current potentials. Both lactate and propionate were cotransported through SMCT1 using 2:1 stoichiometries. The leak current passing through the protein has a 1 osmolyte/charge stoichiometry. Identification of cotransporter stoichiometry is not always a trivial task and it can lead to a much better understanding of the transport activity mediated by the protein in question.
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Affiliation(s)
- Michael J Coady
- Groupe d'étude des protéines membranaires and Département de Physique, Université de Montréal, Montréal, Canada.
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42
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Abstract
This review investigates some key aspects of transport mechanisms and recent advances in our understanding of this ubiquitous cellular process. The prevailing model of cotransport is the alternating access model, which suggests that large conformational changes in the transporter protein accompany cotransport. This model rests on decades of research and has received substantial support because many transporter characteristics are explained using its premises. New experiments, however, have revealed the existence of channels in transporters, an idea that is in conflict with traditional models. The alternating access model is the subject of previous detailed reviews. Here we concentrate on the relatively recent data that document primarily the channel properties of transporters. In some cases, namely, the observation of single-transporter currents, the evidence is direct. In other cases the evidence--for example, from fluctuation analysis or transporter currents too large to be described as anything other than channel-like--is indirect. Although the existence of channels in transporters is not in doubt, we are far from understanding the significance of this property. In the online Supplemental Material , we review some pertinent aspects of ion channel theory and cotransport physiology to provide background for the channels and transporters presented here. We discuss the existence of channels in transporters, and we speculate on the biological significance of this newly unveiled property of transport proteins.
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Affiliation(s)
- Louis J DeFelice
- Department of Pharmacology and Molecular Neuroscience, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
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43
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Panizzi JR, Jessen JR, Drummond IA, Solnica-Krezel L. New functions for a vertebrate Rho guanine nucleotide exchange factor in ciliated epithelia. Development 2007; 134:921-31. [PMID: 17267448 DOI: 10.1242/dev.02776] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Human ARHGEF11, a PDZ-domain-containing Rho guanine nucleotide exchange factor (RhoGEF), has been studied primarily in tissue culture, where it exhibits transforming ability, associates with and modulates the actin cytoskeleton, regulates neurite outgrowth, and mediates activation of Rho in response to stimulation by activated Galpha12/13 or Plexin B1. The fruit fly homolog, RhoGEF2, interacts with heterotrimeric G protein subunits to activate Rho, associates with microtubules, and is required during gastrulation for cell shape changes that mediate epithelial folding. Here, we report functional characterization of a zebrafish homolog of ARHGEF11 that is expressed ubiquitously at blastula and gastrula stages and is enriched in neural tissues and the pronephros during later embryogenesis. Similar to its human homolog, zebrafish Arhgef11 stimulated actin stress fiber formation in cultured cells, whereas overexpression in the embryo of either the zebrafish or human protein impaired gastrulation movements. Loss-of-function experiments utilizing a chromosomal deletion that encompasses the arhgef11 locus, and antisense morpholino oligonucleotides designed to block either translation or splicing, produced embryos with ventrally-curved axes and a number of other phenotypes associated with ciliated epithelia. Arhgef11-deficient embryos often exhibited altered expression of laterality markers, enlarged brain ventricles, kidney cysts, and an excess number of otoliths in the otic vesicles. Although cilia formed and were motile in these embryos, polarized distribution of F-actin and Na(+)/K(+)-ATPase in the pronephric ducts was disturbed. Our studies in zebrafish embryos have identified new, essential roles for this RhoGEF in ciliated epithelia during vertebrate development.
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Affiliation(s)
- Jennifer R Panizzi
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA
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