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Ha HTT, Sukumar VK, Chua JWB, Nguyen DT, Nguyen TQ, Lim LHK, Cazenave-Gassiot A, Nguyen LN. Mfsd7b facilitates choline transport and missense mutations affect choline transport function. Cell Mol Life Sci 2023; 81:3. [PMID: 38055060 PMCID: PMC11072022 DOI: 10.1007/s00018-023-05048-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 11/09/2023] [Accepted: 11/09/2023] [Indexed: 12/07/2023]
Abstract
MFSD7b belongs to the Major Facilitator Superfamily of transporters that transport small molecules. Two isoforms of MFSD7b have been identified and they are reported to be heme exporters that play a crucial role in maintaining the cytosolic and mitochondrial heme levels, respectively. Mutations of MFSD7b (also known as FLVCR1) have been linked to retinitis pigmentosa, posterior column ataxia, and hereditary sensory and autonomic neuropathy. Although MFSD7b functions have been linked to heme detoxification by exporting excess heme from erythroid cells, it is ubiquitously expressed with a high level in the kidney, gastrointestinal tract, lungs, liver, and brain. Here, we showed that MFSD7b functions as a facilitative choline transporter. Expression of MFSD7b slightly but significantly increased choline import, while its knockdown reduced choline influx in mammalian cells. The influx of choline transported by MFSD7b is dependent on the expression of choline metabolizing enzymes such as choline kinase (CHKA) and intracellular choline levels, but it is independent of gradient of cations. Additionally, we showed that choline transport function of Mfsd7b is conserved from fly to man. Employing our transport assays, we showed that missense mutations of MFSD7b caused reduced choline transport functions. Our results show that MFSD7b functions as a facilitative choline transporter in mammalian cells.
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Affiliation(s)
- Hoa Thi Thuy Ha
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
| | - Viresh Krishnan Sukumar
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
| | - Jonathan Wei Bao Chua
- Immunology Program, Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore
| | - Dat T Nguyen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
| | - Toan Q Nguyen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
| | - Lina Hsiu Kim Lim
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
- Immunology Program, Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore
| | - Amaury Cazenave-Gassiot
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore
| | - Long N Nguyen
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 119228, Singapore.
- Immunology Program, Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore.
- Singapore Lipidomics Incubator (SLING), Life Sciences Institute, National University of Singapore, Singapore, 117456, Singapore.
- Cardiovascular Disease Research (CVD) Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117545, Singapore.
- Immunology Translational Research Program, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117456, Singapore.
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2
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Perego MC, McMichael BD, McMurry NR, Ventrello SW, Bain LJ. Arsenic Impairs Differentiation of Human Induced Pluripotent Stem Cells into Cholinergic Motor Neurons. TOXICS 2023; 11:644. [PMID: 37624150 PMCID: PMC10458826 DOI: 10.3390/toxics11080644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/04/2023] [Accepted: 07/14/2023] [Indexed: 08/26/2023]
Abstract
Arsenic exposure during embryogenesis can lead to improper neurodevelopment and changes in locomotor activity. Additionally, in vitro studies have shown that arsenic inhibits the differentiation of sensory neurons and skeletal muscle. In the current study, human-induced pluripotent stem (iPS) cells were differentiated into motor neurons over 28 days, while being exposed to up to 0.5 μM arsenic. On day 6, neuroepithelial progenitor cells (NEPs) exposed to arsenic had reduced transcript levels of the neural progenitor/stem cell marker nestin (NES) and neuroepithelial progenitor marker SOX1, while levels of these transcripts were increased in motor neuron progenitors (MNPs) at day 12. In day 18 early motor neurons (MNs), choline acetyltransferase (CHAT) expression was reduced two-fold in cells exposed to 0.5 μM arsenic. RNA sequencing demonstrated that the cholinergic synapse pathway was impaired following exposure to 0.5 μM arsenic, and that transcript levels of genes involved in acetylcholine synthesis (CHAT), transport (solute carriers, SLC18A3 and SLC5A7) and degradation (acetylcholinesterase, ACHE) were all downregulated in day 18 early MNs. In day 28 mature motor neurons, arsenic significantly downregulated protein expression of microtubule-associated protein 2 (MAP2) and ChAT by 2.8- and 2.1-fold, respectively, concomitantly with a reduction in neurite length. These results show that exposure to environmentally relevant arsenic concentrations dysregulates the differentiation of human iPS cells into motor neurons and impairs the cholinergic synapse pathway, suggesting that exposure impairs cholinergic function in motor neurons.
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Affiliation(s)
- M. Chiara Perego
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | | | - Nicholas R. McMurry
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | - Scott W. Ventrello
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | - Lisa J. Bain
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
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3
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Dvorak V, Superti-Furga G. Structural and functional annotation of solute carrier transporters: implication for drug discovery. Expert Opin Drug Discov 2023; 18:1099-1115. [PMID: 37563933 DOI: 10.1080/17460441.2023.2244760] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 08/01/2023] [Indexed: 08/12/2023]
Abstract
INTRODUCTION Solute carriers (SLCs) represent the largest group of membrane transporters in the human genome. They play a central role in controlling the compartmentalization of metabolism and most of this superfamily is linked to human disease. Despite being in general considered druggable and attractive therapeutic targets, many SLCs remain poorly annotated, both functionally and structurally. AREAS COVERED The aim of this review is to provide an overview of functional and structural parameters of SLCs that play important roles in their druggability. To do this, the authors provide an overview of experimentally solved structures of human SLCs, with emphasis on structures solved in complex with chemical modulators. From the functional annotations, the authors focus on SLC localization and SLC substrate annotations. EXPERT OPINION Recent progress in the structural and functional annotations allows to refine the SLC druggability index. Particularly the increasing number of experimentally solved structures of SLCs provides insights into mode-of-action of a significant number of chemical modulators of SLCs.
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Affiliation(s)
- Vojtech Dvorak
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna, Austria
- Center for Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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4
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Rizvi M, Truong TK, Zhou J, Batta M, Moran ES, Pappas J, Chu ML, Caluseriu O, Evrony GD, Leslie EM, Cordat E. Biochemical characterization of two novel mutations in the human high-affinity choline transporter 1 identified in a patient with congenital myasthenic syndrome. Hum Mol Genet 2023; 32:1552-1564. [PMID: 36611016 DOI: 10.1093/hmg/ddac309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/21/2022] [Accepted: 12/22/2022] [Indexed: 01/09/2023] Open
Abstract
Congenital myasthenic syndrome (CMS) is a heterogeneous condition associated with 34 different genes, including SLC5A7, which encodes the high-affinity choline transporter 1 (CHT1). CHT1 is expressed in presynaptic neurons of the neuromuscular junction where it uses the inward sodium gradient to reuptake choline. Biallelic CHT1 mutations often lead to neonatal lethality, and less commonly to non-lethal motor weakness and developmental delays. Here, we report detailed biochemical characterization of two novel mutations in CHT1, p.I294T and p.D349N, which we identified in an 11-year-old patient with a history of neonatal respiratory distress, and subsequent hypotonia and global developmental delay. Heterologous expression of each CHT1 mutant in human embryonic kidney cells showed two different mechanisms of reduced protein function. The p.I294T CHT1 mutant transporter function was detectable, but its abundance and half-life were significantly reduced. In contrast, the p.D349N CHT1 mutant was abundantly expressed at the cell membrane, but transporter function was absent. The residual function of the p.I294T CHT1 mutant may explain the non-lethal form of CMS in this patient, and the divergent mechanisms of reduced CHT1 function that we identified may guide future functional studies of the CHT1 myasthenic syndrome. Based on these in vitro studies that provided a diagnosis, treatment with cholinesterase inhibitor together with physical and occupational therapy significantly improved the patient's strength and quality of life.
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Affiliation(s)
- Midhat Rizvi
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Tina K Truong
- Center for Human Genetics and Genomics, New York University Grossman School of Medicine, New York, NY, USA
| | - Janet Zhou
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Manav Batta
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Ellen S Moran
- Clinical Genetics, New York University Langone Orthopedic Hospital, New York, NY, USA
| | - John Pappas
- Division of Clinical Genetics, Department of Pediatrics, New York University Grossman School of Medicine, New York, NY, USA
| | - Mary Lynn Chu
- Department of Neurology, New York University School of Medicine, New York, NY, USA
| | - Oana Caluseriu
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Gilad D Evrony
- Center for Human Genetics and Genomics, New York University Grossman School of Medicine, New York, NY, USA
- Department of Pediatrics, Department of Neuroscience and Physiology, New York University Grossman School of Medicine, New York, NY, USA
| | - Elaine M Leslie
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Emmanuelle Cordat
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada
- Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
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5
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Zhang H, Liu C, Hua W, Ghislain LP, Liu J, Aschenbrenner L, Noell S, Dirico KJ, Lanyon LF, Steppan CM, West M, Arnold DW, Covey TR, Datwani SS, Troutman MD. Acoustic Ejection Mass Spectrometry for High-Throughput Analysis. Anal Chem 2021; 93:10850-10861. [PMID: 34320311 DOI: 10.1021/acs.analchem.1c01137] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We describe a mass spectrometry (MS) analytical platform resulting from the novel integration of acoustic droplet ejection (ADE) technology, an open-port interface (OPI), and electrospray ionization (ESI)-MS that creates a transformative system enabling high-speed sampling and label-free analysis. The ADE technology delivers nanoliter droplets in a touchless manner with high speed, precision, and accuracy. Subsequent sample dilution within the OPI, in concert with the capabilities of modern ESI-MS, eliminates the laborious sample preparation and method development required in current approaches. This platform is applied to a variety of experiments, including high-throughput (HT) pharmacology screening, label-free in situ enzyme kinetics, in vitro absorption, distribution, metabolism, elimination, pharmacokinetic and biomarker analysis, and HT parallel medicinal chemistry.
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Affiliation(s)
- Hui Zhang
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Chang Liu
- SCIEX, 71 Four Valley Drive, Concord, Ontario L4K 4V8, Canada
| | - Wenyi Hua
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Lucien P Ghislain
- Beckman Coulter Life Sciences Inc., San Jose, California 95134, United States
| | - Jianhua Liu
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Lisa Aschenbrenner
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Stephen Noell
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Kenneth J Dirico
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Lorraine F Lanyon
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Claire M Steppan
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Mike West
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
| | - Don W Arnold
- SCIEX, 71 Four Valley Drive, Concord, Ontario L4K 4V8, Canada
| | - Thomas R Covey
- SCIEX, 71 Four Valley Drive, Concord, Ontario L4K 4V8, Canada
| | - Sammy S Datwani
- Beckman Coulter Life Sciences Inc., San Jose, California 95134, United States
| | - Matthew D Troutman
- Pfizer Global Research and Development, Eastern Point Road, Groton, Connecticut 06340, United States
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6
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Gerbeth-Kreul C, Pommereau A, Ruf S, Kane JL, Kuntzweiler T, Hessler G, Engel CK, Shum P, Wei L, Czech J, Licher T. A Solid Supported Membrane-Based Technology for Electrophysical Screening of B 0AT1-Modulating Compounds. SLAS DISCOVERY 2021; 26:783-797. [PMID: 33955247 DOI: 10.1177/24725552211011180] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Classical high-throughput screening (HTS) technologies for the analysis of ionic currents across biological membranes can be performed using fluorescence-based, radioactive, and mass spectrometry (MS)-based uptake assays. These assays provide rapid results for pharmacological HTS, but the underlying, indirect analytical character of these assays can be linked to high false-positive hit rates. Thus, orthogonal and secondary assays using more biological target-based technologies are indispensable for further compound validation and optimization. Direct assay technologies for transporter proteins are electrophysiology-based, but are also complex, time-consuming, and not well applicable for automated profiling purposes. In contrast to conventional patch clamp systems, solid supported membrane (SSM)-based electrophysiology is a sensitive, membrane-based method for transporter analysis, and current technical developments target the demand for automated, accelerated, and sensitive assays for transporter-directed compound screening. In this study, the suitability of the SSM-based technique for pharmacological compound identification and optimization was evaluated performing cell-free SSM-based measurements with the electrogenic amino acid transporter B0AT1 (SLC6A19). Electrophysiological characterization of leucine-induced currents demonstrated that the observed signals were specific to B0AT1. Moreover, B0AT1-dependent responses were successfully inhibited using an established in-house tool compound. Evaluation of current stability and data reproducibility verified the robustness and reliability of the applied assay. Active compounds from primary screens of large compound libraries were validated, and false-positive hits were identified. These results clearly demonstrate the suitability of the SSM-based technique as a direct electrophysiological method for rapid and automated identification of small molecules that can inhibit B0AT1 activity.
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Affiliation(s)
- Carolin Gerbeth-Kreul
- In Vitro Biology & High-throughput Chemistry, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - Antje Pommereau
- In Vitro Biology & High-throughput Chemistry, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - Sven Ruf
- Synthetic Molecular Design, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - John L Kane
- Medicinal Chemistry, Integrated Drug Discovery, Sanofi-Genzyme, Waltham, MA, USA
| | - Theresa Kuntzweiler
- In Vitro Biology, Integrated Drug Discovery, Sanofi-Genzyme, Waltham, MA, USA
| | - Gerhard Hessler
- Synthetic Molecular Design, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - Christian K Engel
- Synthetic Molecular Design, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - Patrick Shum
- Medicinal Chemistry, Integrated Drug Discovery, Sanofi-Genzyme, Waltham, MA, USA
| | - LinLi Wei
- Medicinal Chemistry, Integrated Drug Discovery, Sanofi-Genzyme, Waltham, MA, USA
| | - Joerg Czech
- In Vitro Biology & High-throughput Chemistry, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
| | - Thomas Licher
- In Vitro Biology & High-throughput Chemistry, Integrated Drug Discovery, Sanofi-Aventis Deutschland GmbH, Frankfurt, Germany
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7
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McLaren DG, Shah V, Wisniewski T, Ghislain L, Liu C, Zhang H, Saldanha SA. High-Throughput Mass Spectrometry for Hit Identification: Current Landscape and Future Perspectives. SLAS DISCOVERY : ADVANCING LIFE SCIENCES R & D 2021; 26:168-191. [PMID: 33482074 DOI: 10.1177/2472555220980696] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
For nearly two decades mass spectrometry has been used as a label-free, direct-detection method for both functional and affinity-based screening of a wide range of therapeutically relevant target classes. Here, we present an overview of several established and emerging mass spectrometry platforms and summarize the unique strengths and performance characteristics of each as they apply to high-throughput screening. Multiple examples from the recent literature are highlighted in order to illustrate the power of each individual technique, with special emphasis given to cases where the use of mass spectrometry was found to be differentiating when compared with other detection formats. Indeed, as many of these examples will demonstrate, the inherent strengths of mass spectrometry-sensitivity, specificity, wide dynamic range, and amenability to complex matrices-can be leveraged to enhance the discriminating power and physiological relevance of assays included in screening cascades. It is our hope that this review will serve as a useful guide to readers of all backgrounds and experience levels on the applicability and benefits of mass spectrometry in the search for hits, leads, and, ultimately, drugs.
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8
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Rodríguez Cruz PM, Hughes I, Manzur A, Munot P, Ramdas S, Wright R, Breen C, Pitt M, Pagnamenta AT, Taylor JC, Palace J, Beeson D. Presynaptic congenital myasthenic syndrome due to three novel mutations in SLC5A7 encoding the sodium-dependant high-affinity choline transporter. Neuromuscul Disord 2021; 31:21-28. [DOI: 10.1016/j.nmd.2020.10.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 10/13/2020] [Accepted: 10/15/2020] [Indexed: 01/14/2023]
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9
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Ojiakor O, Rylett R. Modulation of sodium-coupled choline transporter CHT function in health and disease. Neurochem Int 2020; 140:104810. [DOI: 10.1016/j.neuint.2020.104810] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/16/2020] [Accepted: 07/09/2020] [Indexed: 12/27/2022]
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10
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Ahmed Juvale II, Che Has AT. The evolution of the pilocarpine animal model of status epilepticus. Heliyon 2020; 6:e04557. [PMID: 32775726 PMCID: PMC7393986 DOI: 10.1016/j.heliyon.2020.e04557] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/05/2020] [Accepted: 07/22/2020] [Indexed: 02/02/2023] Open
Abstract
The pilocarpine animal model of status epilepticus is a well-established, clinically translatable model that satisfies all of the criteria essential for an animal model of status epilepticus: a latency period followed by spontaneous recurrent seizures, replication of behavioural, electrographic, metabolic, and neuropathological changes, as well as, pharmacoresistance to anti-epileptic drugs similar to that observed in human status epilepticus. However, this model is also characterized by high mortality rates and studies in recent years have also seen difficulties in seizure induction due to pilocarpine resistant animals. This can be attributed to differences in rodent strains, species, gender, and the presence of the multi-transporter, P-glycoprotein at the blood brain barrier. The current paper highlights the various alterations made to the original pilocarpine model over the years to combat both the high mortality and low induction rates. These range from the initial lithium-pilocarpine model to the more recent Reduced Intensity Status Epilepticus (RISE) model, which finally brought the mortality rates down to 1%. These modifications are essential to improve animal welfare and future experimental outcomes.
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Affiliation(s)
- Iman Imtiyaz Ahmed Juvale
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia
| | - Ahmad Tarmizi Che Has
- Department of Neurosciences, School of Medical Sciences, Universiti Sains Malaysia, Health Campus, 16150 Kubang Kerian, Kelantan, Malaysia
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11
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Abstract
Here, we present a protocol for the functional characterization of the H+-coupled human peptide transporter PepT1 and sufficient notes to transfer the protocol to the Na+-coupled sugar transporter SGLT1, the organic cation transporter OCT2, the Na+/Ca2+ exchanger NCX, and the neuronal glutamate transporter EAAT3.The assay was developed for the commercially available SURFE2R N1 instrument (Nanion Technologies GmbH) which applies solid supported membrane (SSM)-based electrophysiology. This technique is widely used for the functional characterization of membrane transporters with more than 100 different transporters characterized so far. The technique is cost-effective, easy to use, and capable of high-throughput measurements.SSM-based electrophysiology utilizes SSM-coated gold sensors to physically adsorb membrane vesicles containing the protein of interest. A fast solution exchange provides the substrate and activates transport. For the measurement of PepT1 activity, we applied a peptide concentration jump to activate H+/peptide symport. Proton influx charges the sensor. A capacitive current is measured reflecting the transport activity of PepT1 . Multiple measurements on the same sensor allow for comparison of transport activity under different conditions. Here, we determine EC50 for PepT1-mediated glycylglycine transport and perform an inhibition experiment using the specific peptide inhibitor Lys[Z(NO2)]-Val.
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12
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Banerjee M, Arutyunov D, Brandwein D, Janetzki-Flatt C, Kolski H, Hume S, Leonard NJ, Watt J, Lacson A, Baradi M, Leslie EM, Cordat E, Caluseriu O. The novel p.Ser263Phe mutation in the human high-affinity choline transporter 1 (CHT1/SLC5A7) causes a lethal form of fetal akinesia syndrome. Hum Mutat 2019; 40:1676-1683. [PMID: 31299140 DOI: 10.1002/humu.23828] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2018] [Revised: 05/04/2019] [Accepted: 05/27/2019] [Indexed: 11/07/2022]
Abstract
A subset of a larger and heterogeneous class of disorders, the congenital myasthenic syndromes (CMS) are caused by pathogenic variants in genes encoding proteins that support the integrity and function of the neuromuscular junction (NMJ). A central component of the NMJ is the sodium-dependent high-affinity choline transporter 1 (CHT1), a solute carrier protein (gene symbol SLC5A7), responsible for the reuptake of choline into nerve termini has recently been implicated as one of several autosomal recessive causes of CMS. We report the identification and functional characterization of a novel pathogenic variant in SLC5A7, c.788C>T (p.Ser263Phe) in an El Salvadorian family with a lethal form of a congenital myasthenic syndrome characterized by fetal akinesia. This study expands the clinical phenotype and insight into a form of fetal akinesia related to CHT1 defects and proposes a genotype-phenotype correlation for the lethal form of SLC5A7-related disorder with potential implications for genetic counseling.
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Affiliation(s)
- Mayukh Banerjee
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Denis Arutyunov
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Daniel Brandwein
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | | | - Hanna Kolski
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Stacey Hume
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada
| | - Norma Jean Leonard
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada.,Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - James Watt
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
| | - Atilano Lacson
- Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Monica Baradi
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Elaine M Leslie
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada.,Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada
| | - Emmanuelle Cordat
- Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, Alberta, Canada
| | - Oana Caluseriu
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta, Canada.,Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
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13
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Leveridge M, Chung CW, Gross JW, Phelps CB, Green D. Integration of Lead Discovery Tactics and the Evolution of the Lead Discovery Toolbox. SLAS DISCOVERY 2018; 23:881-897. [PMID: 29874524 DOI: 10.1177/2472555218778503] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
There has been much debate around the success rates of various screening strategies to identify starting points for drug discovery. Although high-throughput target-based and phenotypic screening has been the focus of this debate, techniques such as fragment screening, virtual screening, and DNA-encoded library screening are also increasingly reported as a source of new chemical equity. Here, we provide examples in which integration of more than one screening approach has improved the campaign outcome and discuss how strengths and weaknesses of various methods can be used to build a complementary toolbox of approaches, giving researchers the greatest probability of successfully identifying leads. Among others, we highlight case studies for receptor-interacting serine/threonine-protein kinase 1 and the bromo- and extra-terminal domain family of bromodomains. In each example, the unique insight or chemistries individual approaches provided are described, emphasizing the synergy of information obtained from the various tactics employed and the particular question each tactic was employed to answer. We conclude with a short prospective discussing how screening strategies are evolving, what this screening toolbox might look like in the future, how to maximize success through integration of multiple tactics, and scenarios that drive selection of one combination of tactics over another.
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Affiliation(s)
- Melanie Leveridge
- 1 GlaxoSmithKline Drug Design and Selection, Platform Technology and Science, Stevenage, Hertfordshire, UK
| | - Chun-Wa Chung
- 1 GlaxoSmithKline Drug Design and Selection, Platform Technology and Science, Stevenage, Hertfordshire, UK
| | - Jeffrey W Gross
- 2 GlaxoSmithKline Drug Design and Selection, Platform Technology and Science, Collegeville, PA, USA
| | - Christopher B Phelps
- 3 GlaxoSmithKline Drug Design and Selection, Platform Technology and Science, Cambridge, MA, USA
| | - Darren Green
- 1 GlaxoSmithKline Drug Design and Selection, Platform Technology and Science, Stevenage, Hertfordshire, UK
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