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Ben-Jemaa S, Boussaha M, Mandonnet N, Bardou P, Naves M. Uncovering structural variants in Creole cattle from Guadeloupe and their impact on environmental adaptation through whole genome sequencing. PLoS One 2024; 19:e0309411. [PMID: 39186744 PMCID: PMC11346954 DOI: 10.1371/journal.pone.0309411] [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: 07/05/2023] [Accepted: 08/12/2024] [Indexed: 08/28/2024] Open
Abstract
Structural variants play an important role in evolutionary processes. Besides, they constitute a large source of inter individual genetic variation that might represent a major factor in the aetiology of complex, multifactorial traits. Their importance in adaptation is becoming increasingly evident in literature. Yet, the characterization of the genomic landscape of structural variants in local breeds remains scarce to date. Herein, we investigate patterns and gene annotation of structural variants in the Creole cattle from Guadeloupe breed using whole genome sequences from 23 bulls representative of the population. In total, we detected 32821 ascertained SV defining 15258 regions, representing ~ 17% of the Creole cattle genome. Among these, 6639 regions have not been previously reported in the Database of Genomic Variants archive. Average number of structural variants detected per individual in the studied population is in the same order of magnitude of that observed in indicine populations and higher than that reported in taurine breeds. We observe an important within-individual variability where approximately half of the detected structural variants have low frequency (MAF < 0.25). Most of the detected structural variants (55%) occurred in intergenic regions. Genic structural variants overlapped with 7793 genes and the predicted effect of most of them is ranked as "modifier". Among the structural variants that were predicted to have a high functional impact on the protein, a 5.5 Kb in length, highly frequent deletion on chromosome 2, affects ALPI, a gene associated with the interaction between gut microbiota and host immune system. The 6639 newly identified structural variants regions include three deletions and three duplications shared by more than 80% of individuals that are significantly enriched for genes related to tRNA threonylcarbamoyladenosine metabolic process, important for temperature adaptation in thermophilic organisms, therefore suggesting a potential role in the thermotolerance of Creole cattle from Guadeloupe cattle to tropical climate. Overall, highly frequent structural variants that are specific to the Creole cattle population encompass olfactory receptor and immunity genes as well as genes involved in muscle tone, muscle development and contraction. Beyond mapping and characterizing structural variants in the Creole cattle from Guadeloupe breed, this study provides valuable information for a better understanding of the potential role of chromosomal rearrangements in adaptive traits in cattle.
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Affiliation(s)
- Slim Ben-Jemaa
- INRAE, ASSET, 97170, Petit-Bourg, France
- Institut National de la Recherche Agronomique de Tunisie, Laboratoire des Productions Animales et Fourragères, Université de Carthage, 2049, Ariana, Tunisia
| | - Mekki Boussaha
- Université Paris-Saclay, INRAE, AgroParisTech, GABI, 78350, Jouy-en-Josas, France
| | | | - Philippe Bardou
- GenPhySE, Université de Toulouse, INRA, Ecole Nationale Vétérinaire de Toulouse (ENVT), 31320, Castanet-Tolosan, France
- Sigenae, INRAE, 31320, Castanet-Tolosan, France
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Schaefer N, Harvey RJ, Villmann C. Startle Disease: New Molecular Insights into an Old Neurological Disorder. Neuroscientist 2023; 29:767-781. [PMID: 35754344 PMCID: PMC10623600 DOI: 10.1177/10738584221104724] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Startle disease (SD) is characterized by enhanced startle responses, generalized muscle stiffness, unexpected falling, and fatal apnea episodes due to disturbed feedback inhibition in the spinal cord and brainstem of affected individuals. Mutations within the glycine receptor (GlyR) subunit and glycine transporter 2 (GlyT2) genes have been identified in individuals with SD. Impaired inhibitory neurotransmission in SD is due to pre- and/or postsynaptic GlyR or presynaptic GlyT2 dysfunctions. Previous research has focused on mutated GlyRs and GlyT2 that impair ion channel/transporter function or trafficking. With insights provided by recently solved cryo-electron microscopy and X-ray structures of GlyRs, a detailed picture of structural transitions important for receptor gating has emerged, allowing a deeper understanding of SD at the molecular level. Moreover, studies on novel SD mutations have demonstrated a higher complexity of SD, with identification of additional clinical signs and symptoms and interaction partners representing key players for fine-tuning synaptic processes. Although our knowledge has steadily improved during the last years, changes in synaptic localization and GlyR or GlyT2 homeostasis under disease conditions are not yet completely understood. Combined proteomics, interactomics, and high-resolution microscopy techniques are required to reveal alterations in receptor dynamics at the synaptic level under disease conditions.
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Affiliation(s)
- Natascha Schaefer
- Institute of Clinical Neurobiology, University Hospital, Julius-Maximilians-University of Würzburg, Würzburg, Germany
| | - Robert J. Harvey
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Maroochydore DC, Australia
- Sunshine Coast Health Institute, Birtinya, Australia
| | - Carmen Villmann
- Institute of Clinical Neurobiology, University Hospital, Julius-Maximilians-University of Würzburg, Würzburg, Germany
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3
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Aguayo-Cerón KA, Sánchez-Muñoz F, Gutierrez-Rojas RA, Acevedo-Villavicencio LN, Flores-Zarate AV, Huang F, Giacoman-Martinez A, Villafaña S, Romero-Nava R. Glycine: The Smallest Anti-Inflammatory Micronutrient. Int J Mol Sci 2023; 24:11236. [PMID: 37510995 PMCID: PMC10379184 DOI: 10.3390/ijms241411236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 06/30/2023] [Indexed: 07/30/2023] Open
Abstract
Glycine is a non-essential amino acid with many functions and effects. Glycine can bind to specific receptors and transporters that are expressed in many types of cells throughout an organism to exert its effects. There have been many studies focused on the anti-inflammatory effects of glycine, including its abilities to decrease pro-inflammatory cytokines and the concentration of free fatty acids, to improve the insulin response, and to mediate other changes. However, the mechanism through which glycine acts is not clear. In this review, we emphasize that glycine exerts its anti-inflammatory effects throughout the modulation of the expression of nuclear factor kappa B (NF-κB) in many cells. Although glycine is a non-essential amino acid, we highlight how dietary glycine supplementation is important in avoiding the development of chronic inflammation.
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Affiliation(s)
- Karla Aidee Aguayo-Cerón
- Escuela Superior de Medicina, Instituto Politécnico Nacional, Sección de Estudios de Posgrado e Investigación, Ciudad de Mexico 11340, Mexico
| | - Fausto Sánchez-Muñoz
- Departamento de Inmunología, Instituto Nacional de Cardiología "Ignacio Chávez", Ciudad de Mexico 14080, Mexico
| | | | | | - Aurora Vanessa Flores-Zarate
- Escuela Superior de Medicina, Instituto Politécnico Nacional, Sección de Estudios de Posgrado e Investigación, Ciudad de Mexico 11340, Mexico
| | - Fengyang Huang
- Laboratorio de Investigación en Obesidad y Asma, Hospital Infantil de México Federico Gómez, Ciudad de Mexico 06720, Mexico
| | - Abraham Giacoman-Martinez
- Laboratorio de Framacología, Departamaneto de Ciencias de la Salud, DCBS, Universidad Autónoma Mteropolitana-Iztapalapa (UAM-I), Ciudad de Mexico 09340, Mexico
| | - Santiago Villafaña
- Escuela Superior de Medicina, Instituto Politécnico Nacional, Sección de Estudios de Posgrado e Investigación, Ciudad de Mexico 11340, Mexico
| | - Rodrigo Romero-Nava
- Escuela Superior de Medicina, Instituto Politécnico Nacional, Sección de Estudios de Posgrado e Investigación, Ciudad de Mexico 11340, Mexico
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Reid KM, Steel D, Nair S, Bhate S, Biassoni L, Sudhakar S, Heys M, Burke E, Kamsteeg EJ, Hameed B, Zech M, Mencacci NE, Barwick K, Topf M, Kurian MA. Loss-of-Function Variants in DRD1 in Infantile Parkinsonism-Dystonia. Cells 2023; 12:cells12071046. [PMID: 37048120 PMCID: PMC10093404 DOI: 10.3390/cells12071046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/23/2023] [Accepted: 03/26/2023] [Indexed: 04/03/2023] Open
Abstract
The human dopaminergic system is vital for a broad range of neurological processes, including the control of voluntary movement. Here we report a proband presenting with clinical features of dopamine deficiency: severe infantile parkinsonism-dystonia, characterised by frequent oculogyric crises, dysautonomia and global neurodevelopmental impairment. CSF neurotransmitter analysis was unexpectedly normal. Triome whole-genome sequencing revealed a homozygous variant (c.110C>A, (p.T37K)) in DRD1, encoding the most abundant dopamine receptor (D1) in the central nervous system, most highly expressed in the striatum. This variant was absent from gnomAD, with a CADD score of 27.5. Using an in vitro heterologous expression system, we determined that DRD1-T37K results in loss of protein function. Structure-function modelling studies predicted reduced substrate binding, which was confirmed in vitro. Exposure of mutant protein to the selective D1 agonist Chloro APB resulted in significantly reduced cyclic AMP levels. Numerous D1 agonists failed to rescue the cellular defect, reflected clinically in the patient, who had no benefit from dopaminergic therapy. Our study identifies DRD1 as a new disease-associated gene, suggesting a crucial role for the D1 receptor in motor control.
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5
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Talvio K, Minkeviciene R, Townsley KG, Achuta VS, Huckins LM, Corcoran P, Brennand KJ, Castrén ML. Reduced LYNX1 expression in transcriptome of human iPSC-derived neural progenitors modeling fragile X syndrome. Front Cell Dev Biol 2022; 10:1034679. [PMID: 36506088 PMCID: PMC9731341 DOI: 10.3389/fcell.2022.1034679] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 11/04/2022] [Indexed: 11/22/2022] Open
Abstract
Lack of FMR1 protein results in fragile X syndrome (FXS), which is the most common inherited intellectual disability syndrome and serves as an excellent model disease to study molecular mechanisms resulting in neuropsychiatric comorbidities. We compared the transcriptomes of human neural progenitors (NPCs) generated from patient-derived induced pluripotent stem cells (iPSCs) of three FXS and three control male donors. Altered expression of RAD51C, PPIL3, GUCY1A2, MYD88, TRAPPC4, LYNX1, and GTF2A1L in FXS NPCs suggested changes related to triplet repeat instability, RNA splicing, testes development, and pathways previously shown to be affected in FXS. LYNX1 is a cholinergic brake of tissue plasminogen activator (tPA)-dependent plasticity, and its reduced expression was consistent with augmented tPA-dependent radial glial process growth in NPCs derived from FXS iPSC lines. There was evidence of human iPSC line donor-dependent variation reflecting potentially phenotypic variation. NPCs derived from an FXS male with concomitant epilepsy expressed differently several epilepsy-related genes, including genes shown to cause the auditory epilepsy phenotype in the murine model of FXS. Functional enrichment analysis highlighted regulation of insulin-like growth factor pathway in NPCs modeling FXS with epilepsy. Our results demonstrated potential of human iPSCs in disease modeling for discovery and development of therapeutic interventions by showing early gene expression changes in FXS iPSC-derived NPCs consistent with the known pathophysiological changes in FXS and by revealing disturbed FXS progenitor growth linked to reduced expression of LYNX1, suggesting dysregulated cholinergic system.
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Affiliation(s)
- Karo Talvio
- Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Rimante Minkeviciene
- Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Kayla G. Townsley
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States,Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States,Graduate School of Biomedical Science, Icahn School of Medicine at Mount Sinai, New York, NY, United States
| | | | - Laura M. Huckins
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States,Division of Molecular Psychiatry, Department of Psychiatry, Yale University, New Haven, CT, United States
| | - Padraic Corcoran
- Array and Analysis Facility, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Kristen J. Brennand
- Pamela Sklar Division of Psychiatric Genomics, Department of Genetics and Genomics, Icahn Institute of Genomics and Multiscale Biology, Icahn School of Medicine at Mount Sinai, New York, NY, United States,Nash Family Department of Neuroscience, Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States,Division of Molecular Psychiatry, Department of Psychiatry, Yale University, New Haven, CT, United States,Department of Genetics, Yale University, New Haven, CT, United States
| | - Maija L. Castrén
- Department of Physiology, Faculty of Medicine, University of Helsinki, Helsinki, Finland,*Correspondence: Maija L. Castrén,
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Anne A, Saxena S, Mohan KN. Genome-wide methylation analysis of post-mortem cerebellum samples supports the role of peroxisomes in autism spectrum disorder. Epigenomics 2022; 14:1015-1027. [PMID: 36154275 DOI: 10.2217/epi-2022-0184] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Aim: We tested the hypothesis that a subset of patients with autism spectrum disorder (ASD) contains candidate genes with high DNA methylation differences (effective values) that potentially affect one of the two alleles. Materials & methods: Genome-wide DNA methylation comparisons were made on cerebellum samples from 30 patients and 45 controls. Results: 12 genes with high effective values, including GSDMD, MMACHC, SLC6A5 and NKX6-2, implicated in ASD and other neuropsychiatric disorders were identified. Monoallelic promoter methylation and downregulation were observed for SERHL (serine hydrolase-like) and CAT (catalase) genes associated with peroxisome function. Conclusion: These data are consistent with the hypothesis implicating impaired peroxisome function/biogenesis for ASD. A similar approach holds promise for identifying rare epimutations in ASD and other complex disorders.
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Affiliation(s)
- Anuhya Anne
- Molecular Biology and Genetics Laboratory, Department of Biological Sciences, Birla Institute of Technology & Science, Pilani - Hyderabad Campus, 500 078, India.,Centre for Human Disease Research, Birla Institute of Technology & Science, Pilani - Hyderabad Campus, 500 078, India
| | - Sonal Saxena
- Molecular Biology and Genetics Laboratory, Department of Biological Sciences, Birla Institute of Technology & Science, Pilani - Hyderabad Campus, 500 078, India
| | - Kommu Naga Mohan
- Molecular Biology and Genetics Laboratory, Department of Biological Sciences, Birla Institute of Technology & Science, Pilani - Hyderabad Campus, 500 078, India.,Centre for Human Disease Research, Birla Institute of Technology & Science, Pilani - Hyderabad Campus, 500 078, India
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7
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Aboheimed GI, AlRasheed MM, Almudimeegh S, Peña-Guerra KA, Cardona-Londoño KJ, Salih MA, Seidahmed MZ, Al-Mohanna F, Colak D, Harvey RJ, Harvey K, Arold ST, Kaya N, Ruiz AJ. Clinical, genetic, and functional characterization of the glycine receptor β-subunit A455P variant in a family affected by hyperekplexia syndrome. J Biol Chem 2022; 298:102018. [PMID: 35526563 PMCID: PMC9241032 DOI: 10.1016/j.jbc.2022.102018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 04/21/2022] [Accepted: 04/27/2022] [Indexed: 12/01/2022] Open
Abstract
Hyperekplexia is a rare neurological disorder characterized by exaggerated startle responses affecting newborns with the hallmark characteristics of hypertonia, apnea, and noise or touch-induced nonepileptic seizures. The genetic causes of the disease can vary, and several associated genes and mutations have been reported to affect glycine receptors (GlyRs); however, the mechanistic links between GlyRs and hyperekplexia are not yet understood. Here, we describe a patient with hyperekplexia from a consanguineous family. Extensive genetic screening using exome sequencing coupled with autozygome analysis and iterative filtering supplemented by in silico prediction identified that the patient carries the homozygous missense mutation A455P in GLRB, which encodes the GlyR β-subunit. To unravel the physiological and molecular effects of A455P on GlyRs, we used electrophysiology in a heterologous system as well as immunocytochemistry, confocal microscopy, and cellular biochemistry. We found a reduction in glycine-evoked currents in N2A cells expressing the mutation compared to WT cells. Western blot analysis also revealed a reduced amount of GlyR β protein both in cell lysates and isolated membrane fractions. In line with the above observations, coimmunoprecipitation assays suggested that the GlyR α1-subunit retained coassembly with βA455P to form membrane-bound heteromeric receptors. Finally, structural modeling showed that the A455P mutation affected the interaction between the GlyR β-subunit transmembrane domain 4 and the other helices of the subunit. Taken together, our study identifies and validates a novel loss-of-function mutation in GlyRs whose pathogenicity is likely to cause hyperekplexia in the affected individual.
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Affiliation(s)
- Ghada I Aboheimed
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia; Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia; Department of Pharmacology, The School of Pharmacy, University College London, London, United Kingdom
| | - Maha M AlRasheed
- Department of Clinical Pharmacy, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - Sultan Almudimeegh
- Department of Pharmacology, The School of Pharmacy, University College London, London, United Kingdom; Department of Pharmacology and Toxicology, College of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - Karla A Peña-Guerra
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
| | - Kelly J Cardona-Londoño
- Computational Bioscience Research Center, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
| | - Mustafa A Salih
- Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Kingdom of Saudi Arabia
| | - Mohammed Z Seidahmed
- Department of Pediatrics, Security Forces Hospital, Riyadh, Kingdom of Saudi Arabia
| | - Futwan Al-Mohanna
- Department of Cell Biology, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia
| | - Dilek Colak
- Department of Molecular Oncology, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia
| | - Robert J Harvey
- School of Health and Behavioural Sciences, University of the Sunshine Coast, Maroochydore, Queensland, Australia; Sunshine Coast Health Institute, Birtinya, Queensland, Australia
| | - Kirsten Harvey
- Department of Pharmacology, The School of Pharmacy, University College London, London, United Kingdom
| | - Stefan T Arold
- Department of Pediatrics, College of Medicine, King Saud University, Riyadh, Kingdom of Saudi Arabia; Centre de Biologie Structurale, CNRS, INSERM, Université de Montpellier, Montpellier, France
| | - Namik Kaya
- Department of Translational Genomics, Center for Genomic Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Kingdom of Saudi Arabia.
| | - Arnaud J Ruiz
- Department of Pharmacology, The School of Pharmacy, University College London, London, United Kingdom.
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Fischer FP, Kasture AS, Hummel T, Sucic S. Molecular and Clinical Repercussions of GABA Transporter 1 Variants Gone Amiss: Links to Epilepsy and Developmental Spectrum Disorders. Front Mol Biosci 2022; 9:834498. [PMID: 35295842 PMCID: PMC7612498 DOI: 10.3389/fmolb.2022.834498] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Accepted: 02/01/2022] [Indexed: 12/15/2022] Open
Abstract
The human γ-aminobutyric acid (GABA) transporter 1 (hGAT-1) is the first member of the solute carrier 6 (SLC6) protein superfamily. GAT-1 (SLC6A1) is one of the main GABA transporters in the central nervous system. Its principal physiological role is retrieving GABA from the synapse into neurons and astrocytes, thus swiftly terminating neurotransmission. GABA is a key inhibitory neurotransmitter and shifts in GABAergic signaling can lead to pathological conditions, from anxiety and epileptic seizures to schizophrenia. Point mutations in the SLC6A1 gene frequently give rise to epilepsy, intellectual disability or autism spectrum disorders in the afflicted individuals. The mechanistic routes underlying these are still fairly unclear. Some loss-of-function variants impair the folding and intracellular trafficking of the protein (thus retaining the transporter in the endoplasmic reticulum compartment), whereas others, despite managing to reach their bona fide site of action at the cell surface, nonetheless abolish GABA transport activity (plausibly owing to structural/conformational defects). Whatever the molecular culprit(s), the physiological aftermath transpires into the absence of functional transporters, which in turn perturbs GABAergic actions. Dozens of mutations in the kin SLC6 family members are known to exhort protein misfolding. Such events typically elicit severe ailments in people, e.g., infantile parkinsonism-dystonia or X-linked intellectual disability, in the case of dopamine and creatine transporters, respectively. Flaws in protein folding can be rectified by small molecules known as pharmacological and/or chemical chaperones. The search for such apt remedies calls for a systematic investigation and categorization of the numerous disease-linked variants, by biochemical and pharmacological means in vitro (in cell lines and primary neuronal cultures) and in vivo (in animal models). We here give special emphasis to the utilization of the fruit fly Drosophila melanogaster as a versatile model in GAT-1-related studies. Jointly, these approaches can portray indispensable insights into the molecular factors underlying epilepsy, and ultimately pave the way for contriving efficacious therapeutic options for patients harboring pathogenic mutations in hGAT-1.
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Affiliation(s)
- Florian P. Fischer
- Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
- Department of Epileptology and Neurology, University of Aachen, Aachen, Germany
| | - Ameya S. Kasture
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Thomas Hummel
- Department of Neuroscience and Developmental Biology, University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
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The presynaptic glycine transporter GlyT2 is regulated by the Hedgehog pathway in vitro and in vivo. Commun Biol 2021; 4:1197. [PMID: 34663888 PMCID: PMC8523746 DOI: 10.1038/s42003-021-02718-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 09/22/2021] [Indexed: 01/20/2023] Open
Abstract
The identity of a glycinergic synapse is maintained presynaptically by the activity of a surface glycine transporter, GlyT2, which recaptures glycine back to presynaptic terminals to preserve vesicular glycine content. GlyT2 loss-of-function mutations cause Hyperekplexia, a rare neurological disease in which loss of glycinergic neurotransmission causes generalized stiffness and strong motor alterations. However, the molecular underpinnings controlling GlyT2 activity remain poorly understood. In this work, we identify the Hedgehog pathway as a robust controller of GlyT2 expression and transport activity. Modulating the activation state of the Hedgehog pathway in vitro in rodent primary spinal cord neurons or in vivo in zebrafish embryos induced a selective control in GlyT2 expression, regulating GlyT2 transport activity. Our results indicate that activation of Hedgehog reduces GlyT2 expression by increasing its ubiquitination and degradation. This work describes a new molecular link between the Hedgehog signaling pathway and presynaptic glycine availability. By modulating the activation state of the Hedgehog pathway, de la Rocha-Muñoz et al demonstrate that Hedgehog signaling controls the expression and transport activity of the neuronal glycine transporter GlyT2. This work begins to reveal a potential link between the Hedgehog signaling pathway and presynaptic glycine availability.
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10
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Zhan FX, Wang SG, Cao L. Advances in hyperekplexia and other startle syndromes. Neurol Sci 2021; 42:4095-4107. [PMID: 34379238 DOI: 10.1007/s10072-021-05493-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 07/14/2021] [Indexed: 02/03/2023]
Abstract
Startle, a basic alerting reaction common to all mammals, is described as a sudden involuntary movement of the body evoked by all kinds of sudden and unexpected stimulus. Startle syndromes are heterogeneous groups of disorders with abnormal and exaggerated responses to startling events, including hyperekplexia, stimulus-induced disorders, and neuropsychiatric startle syndromes. Hyperekplexia can be attributed to a genetic, idiopathic, or symptomatic cause. Excluding secondary factors, hereditary hyperekplexia, a rare neurogenetic disorder with highly genetic heterogeneity, is characterized by neonatal hypertonia, exaggerated startle response provoked by the sudden external stimuli, and followed by a short period of general stiffness. It mainly arises from defects of inhibitory glycinergic neurotransmission. GLRA1 is the major pathogenic gene of hereditary hyperekplexia, along with many other genes involved in the function of glycinergic inhibitory synapses. While about 40% of patients remain negative genetic findings. Clonazepam, which can specifically upgrade the GABARA1 chloride channels, is the main and most effective administration for hereditary hyperekplexia patients. In this review, with the aim at enhancing the recognition and prompting potential treatment for hyperekplexia, we focused on discussing the advances in hereditary hyperekplexia genetics and the expound progress in pathogenic mechanisms of the glycinergic-synapse-related pathway and then followed by a brief overview of other common startle syndromes.
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Affiliation(s)
- Fei-Xia Zhan
- Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yi Shan Road, Shanghai, 200233, China
| | - Shi-Ge Wang
- Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yi Shan Road, Shanghai, 200233, China
| | - Li Cao
- Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, 600 Yi Shan Road, Shanghai, 200233, China.
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11
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Neupert DG, Rathke KM, Mikati MA. Teaching Video Neuroimages: Hereditary Hyperekplexia Mimicking Tonic Seizures in an Infant. Neurology 2021; 97:e2248-e2249. [PMID: 34266921 DOI: 10.1212/wnl.0000000000012538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Hereditary hyperekplexia is a rare neurological disorder characterized by an exaggerated startle response with profound muscle stiffness. Given the nature of the spells, this condition is often misdiagnosed as epilepsy. Mutations in glycine receptors and transporters are the primary cause of this syndrome. We present an example of stimulus induced hyperekplexia captured on video EEG in a 7-week-old girl with compound heterozygous variants in the presynaptic glycine transporter gene SLC6A5.
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Affiliation(s)
- Derek G Neupert
- Department of Neurology, Duke University School of Medicine, Durham, NC
| | - Kevin M Rathke
- Division of Pediatric Neurology, Department of Pediatrics, Duke University School of Medicine, Durham, NC
| | - Mohamad A Mikati
- Division of Pediatric Neurology, Department of Pediatrics, Duke University School of Medicine, Durham, NC
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12
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Inhibition of Glycine Re-Uptake: A Potential Approach for Treating Pain by Augmenting Glycine-Mediated Spinal Neurotransmission and Blunting Central Nociceptive Signaling. Biomolecules 2021; 11:biom11060864. [PMID: 34200954 PMCID: PMC8230656 DOI: 10.3390/biom11060864] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 12/23/2022] Open
Abstract
Among the myriad of cellular and molecular processes identified as contributing to pathological pain, disinhibition of spinal cord nociceptive signaling to higher cortical centers plays a critical role. Importantly, evidence suggests that impaired glycinergic neurotransmission develops in the dorsal horn of the spinal cord in inflammatory and neuropathic pain models and is a key maladaptive mechanism causing mechanical hyperalgesia and allodynia. Thus, it has been hypothesized that pharmacological agents capable of augmenting glycinergic tone within the dorsal horn may be able to blunt or block aberrant nociceptor signaling to the brain and serve as a novel class of analgesics for various pathological pain states. Indeed, drugs that enhance dysfunctional glycinergic transmission, and in particular inhibitors of the glycine transporters (GlyT1 and GlyT2), are generating widespread interest as a potential class of novel analgesics. The GlyTs are Na+/Cl−-dependent transporters of the solute carrier 6 (SLC6) family and it has been proposed that the inhibition of them presents a possible mechanism by which to increase spinal extracellular glycine concentrations and enhance GlyR-mediated inhibitory neurotransmission in the dorsal horn. Various inhibitors of both GlyT1 and GlyT2 have demonstrated broad analgesic efficacy in several preclinical models of acute and chronic pain, providing promise for the approach to deliver a first-in-class non-opioid analgesic with a mechanism of action differentiated from current standard of care. This review will highlight the therapeutic potential of GlyT inhibitors as a novel class of analgesics, present recent advances reported for the field, and discuss the key challenges associated with the development of a GlyT inhibitor into a safe and effective agent to treat pain.
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Rescue of two trafficking-defective variants of the neuronal glycine transporter GlyT2 associated to hyperekplexia. Neuropharmacology 2021; 189:108543. [PMID: 33794243 DOI: 10.1016/j.neuropharm.2021.108543] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 03/25/2021] [Accepted: 03/26/2021] [Indexed: 11/21/2022]
Abstract
Hyperekplexia is a rare sensorimotor syndrome characterized by pathological startle reflex in response to unexpected trivial stimuli for which there is no specific treatment. Neonates suffer from hypertonia and are at high risk of sudden death due to apnea episodes. Mutations in the human SLC6A5 gene encoding the neuronal glycine transporter GlyT2 may disrupt the inhibitory glycinergic neurotransmission and cause a presynaptic form of the disease. The phenotype of missense mutations giving rise to protein misfolding but maintaining residual activity could be rescued by facilitating folding or intracellular trafficking. In this report, we characterized the trafficking properties of two mutants associated with hyperekplexia (A277T and Y707C, rat numbering). Transporter molecules were partially retained in the endoplasmic reticulum showing increased interaction with the endoplasmic reticulum chaperone calnexin. One transporter variant had export difficulties and increased ubiquitination levels, suggestive of enhanced endoplasmic reticulum-associated degradation. However, the two mutant transporters were amenable to correction by calnexin overexpression. Within the search for compounds capable of rescuing mutant phenotypes, we found that the arachidonic acid derivative N-arachidonoyl glycine can rescue the trafficking defects of the two variants in heterologous cells and rat brain cortical neurons. N-arachidonoyl glycine improves the endoplasmic reticulum output by reducing the interaction transporter/calnexin, increasing membrane expression and improving transport activity in a comparable way as the well-established chemical chaperone 4-phenyl-butyrate. This work identifies N-arachidonoyl glycine as a promising compound with potential for hyperekplexia therapy.
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Brill SE, Maraslioglu A, Kurz C, Kramer F, Fuhr MF, Singh A, Friauf E. Glycinergic Transmission in the Presence and Absence of Functional GlyT2: Lessons From the Auditory Brainstem. Front Synaptic Neurosci 2021; 12:560008. [PMID: 33633558 PMCID: PMC7900164 DOI: 10.3389/fnsyn.2020.560008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Accepted: 12/01/2020] [Indexed: 12/20/2022] Open
Abstract
Synaptic transmission is controlled by re-uptake systems that reduce transmitter concentrations in the synaptic cleft and recycle the transmitter into presynaptic terminals. The re-uptake systems are thought to ensure cytosolic concentrations in the terminals that are sufficient for reloading empty synaptic vesicles (SVs). Genetic deletion of glycine transporter 2 (GlyT2) results in severely disrupted inhibitory neurotransmission and ultimately to death. Here we investigated the role of GlyT2 at inhibitory glycinergic synapses in the mammalian auditory brainstem. These synapses are tuned for resilience, reliability, and precision, even during sustained high-frequency stimulation when endocytosis and refilling of SVs probably contribute substantially to efficient replenishment of the readily releasable pool (RRP). Such robust synapses are formed between MNTB and LSO neurons (medial nucleus of the trapezoid body, lateral superior olive). By means of patch-clamp recordings, we assessed the synaptic performance in controls, in GlyT2 knockout mice (KOs), and upon acute pharmacological GlyT2 blockade. Via computational modeling, we calculated the reoccupation rate of empty release sites and RRP replenishment kinetics during 60-s challenge and 60-s recovery periods. Control MNTB-LSO inputs maintained high fidelity neurotransmission at 50 Hz for 60 s and recovered very efficiently from synaptic depression. During 'marathon-experiments' (30,600 stimuli in 20 min), RRP replenishment accumulated to 1,260-fold. In contrast, KO inputs featured severe impairments. For example, the input number was reduced to ~1 (vs. ~4 in controls), implying massive functional degeneration of the MNTB-LSO microcircuit and a role of GlyT2 during synapse maturation. Surprisingly, neurotransmission did not collapse completely in KOs as inputs still replenished their small RRP 80-fold upon 50 Hz | 60 s challenge. However, they totally failed to do so for extended periods. Upon acute pharmacological GlyT2 inactivation, synaptic performance remained robust, in stark contrast to KOs. RRP replenishment was 865-fold in marathon-experiments, only ~1/3 lower than in controls. Collectively, our empirical and modeling results demonstrate that GlyT2 re-uptake activity is not the dominant factor in the SV recycling pathway that imparts indefatigability to MNTB-LSO synapses. We postulate that additional glycine sources, possibly the antiporter Asc-1, contribute to RRP replenishment at these high-fidelity brainstem synapses.
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Affiliation(s)
- Sina E Brill
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Ayse Maraslioglu
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Catharina Kurz
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Florian Kramer
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Martin F Fuhr
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
| | - Abhyudai Singh
- Electrical & Computer Engineering, University of Delaware, Newark, DE, United States
| | - Eckhard Friauf
- Animal Physiology Group, Department of Biology, University of Kaiserslautern, Kaiserslautern, Germany
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Bhat S, El-Kasaby A, Freissmuth M, Sucic S. Functional and Biochemical Consequences of Disease Variants in Neurotransmitter Transporters: A Special Emphasis on Folding and Trafficking Deficits. Pharmacol Ther 2020; 222:107785. [PMID: 33310157 PMCID: PMC7612411 DOI: 10.1016/j.pharmthera.2020.107785] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 12/02/2020] [Indexed: 01/30/2023]
Abstract
Neurotransmitters, such as γ-aminobutyric acid, glutamate, acetyl choline, glycine and the monoamines, facilitate the crosstalk within the central nervous system. The designated neurotransmitter transporters (NTTs) both release and take up neurotransmitters to and from the synaptic cleft. NTT dysfunction can lead to severe pathophysiological consequences, e.g. epilepsy, intellectual disability, or Parkinson’s disease. Genetic point mutations in NTTs have recently been associated with the onset of various neurological disorders. Some of these mutations trigger folding defects in the NTT proteins. Correct folding is a prerequisite for the export of NTTs from the endoplasmic reticulum (ER) and the subsequent trafficking to their pertinent site of action, typically at the plasma membrane. Recent studies have uncovered some of the key features in the molecular machinery responsible for transporter protein folding, e.g., the role of heat shock proteins in fine-tuning the ER quality control mechanisms in cells. The therapeutic significance of understanding these events is apparent from the rising number of reports, which directly link different pathological conditions to NTT misfolding. For instance, folding-deficient variants of the human transporters for dopamine or GABA lead to infantile parkinsonism/dystonia and epilepsy, respectively. From a therapeutic point of view, some folding-deficient NTTs are amenable to functional rescue by small molecules, known as chemical and pharmacological chaperones.
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Affiliation(s)
- Shreyas Bhat
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Ali El-Kasaby
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria.
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Crisp SJ, Dixon CL, Jacobson L, Chabrol E, Irani SR, Leite MI, Leschziner G, Slaght SJ, Vincent A, Kullmann DM. Glycine receptor autoantibodies disrupt inhibitory neurotransmission. Brain 2020; 142:3398-3410. [PMID: 31591639 PMCID: PMC6821286 DOI: 10.1093/brain/awz297] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 07/25/2019] [Accepted: 08/07/2019] [Indexed: 12/15/2022] Open
Abstract
Chloride-permeable glycine receptors have an important role in fast inhibitory neurotransmission in the spinal cord and brainstem. Human immunoglobulin G (IgG) autoantibodies to glycine receptors are found in a substantial proportion of patients with progressive encephalomyelitis with rigidity and myoclonus, and less frequently in other variants of stiff person syndrome. Demonstrating a pathogenic role of glycine receptor autoantibodies would help justify the use of immunomodulatory therapies and provide insight into the mechanisms involved. Here, purified IgGs from four patients with progressive encephalomyelitis with rigidity and myoclonus or stiff person syndrome, and glycine receptor autoantibodies, were observed to disrupt profoundly glycinergic neurotransmission. In whole-cell patch clamp recordings from cultured rat spinal motor neurons, glycinergic synaptic currents were almost completely abolished following incubation in patient IgGs. Most human autoantibodies targeting other CNS neurotransmitter receptors, such as N-methyl-d-aspartate (NMDA) receptors, affect whole cell currents only after several hours incubation and this effect has been shown to be the result of antibody-mediated crosslinking and internalization of receptors. By contrast, we observed substantial reductions in glycinergic currents with all four patient IgG preparations with 15 min of exposure to patient IgGs. Moreover, monovalent Fab fragments generated from the purified IgG of three of four patients also profoundly reduced glycinergic currents compared with control Fab-IgG. We conclude that human glycine receptor autoantibodies disrupt glycinergic neurotransmission, and also suggest that the pathogenic mechanisms include direct antagonistic actions on glycine receptors.
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Affiliation(s)
- Sarah J Crisp
- UCL Institute of Neurology, University College London, London, UK
| | | | - Leslie Jacobson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Elodie Chabrol
- UCL Institute of Neurology, University College London, London, UK
| | - Sarosh R Irani
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - M Isabel Leite
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Guy Leschziner
- Department of Neurology, Guy's and St Thomas' NHS Foundation Trust, London, UK.,Department of Clinical Neuroscience, King's College London, London, UK
| | - Sean J Slaght
- Wessex Neurological Centre, University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Angela Vincent
- UCL Institute of Neurology, University College London, London, UK.,Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
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Mostyn SN, Sarker S, Muthuraman P, Raja A, Shimmon S, Rawling T, Cioffi CL, Vandenberg RJ. Photoswitchable ORG25543 Congener Enables Optical Control of Glycine Transporter 2. ACS Chem Neurosci 2020; 11:1250-1258. [PMID: 32191428 PMCID: PMC7206614 DOI: 10.1021/acschemneuro.9b00655] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
![]()
Glycine
neurotransmission in the dorsal horn of the spinal cord
plays a key role in regulating nociceptive signaling, but in chronic
pain states reduced glycine neurotransmission is associated with the
development of allodynia and hypersensitivity to painful stimuli.
This suggests that restoration of glycine neurotransmission may be
therapeutic for the treatment of chronic pain. Glycine transporter
2 inhibitors have been demonstrated to enhance glycine neurotransmission
and provide relief from allodynia in rodent models of chronic pain.
In recent years, photoswitchable compounds have been developed to
provide the possibility of controlling the activity of target proteins
using light. In this study we have developed a photoswitchable noncompetitive
inhibitor of glycine transporter 2 that has different affinities for
the transporter at 365 nm compared to 470 nm light.
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Affiliation(s)
- Shannon N. Mostyn
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Subhodeep Sarker
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
| | - Parthasarathy Muthuraman
- Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, United States
| | - Arun Raja
- Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, United States
| | - Susan Shimmon
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Tristan Rawling
- School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, New South Wales 2007, Australia
| | - Christopher L. Cioffi
- Basic and Clinical Sciences and Pharmaceutical Sciences, Albany College of Pharmacy and Health Sciences, Albany, New York 12208, United States
| | - Robert J. Vandenberg
- Discipline of Pharmacology, School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Camperdown, New South Wales 2006, Australia
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A Novel Glycine Receptor Variant with Startle Disease Affects Syndapin I and Glycinergic Inhibition. J Neurosci 2020; 40:4954-4969. [PMID: 32354853 DOI: 10.1523/jneurosci.2490-19.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2019] [Revised: 03/24/2020] [Accepted: 04/24/2020] [Indexed: 11/21/2022] Open
Abstract
Glycine receptors (GlyRs) are the major mediators of fast synaptic inhibition in the adult human spinal cord and brainstem. Hereditary mutations to GlyRs can lead to the rare, but potentially fatal, neuromotor disorder hyperekplexia. Most mutations located in the large intracellular domain (TM3-4 loop) of the GlyRα1 impair surface expression levels of the receptors. The novel GLRA1 mutation P366L, located in the TM3-4 loop, showed normal surface expression but reduced chloride currents, and accelerated whole-cell desensitization observed in whole-cell recordings. At the single-channel level, we observed reduced unitary conductance accompanied by spontaneous opening events in the absence of extracellular glycine. Using peptide microarrays and tandem MS-based analysis methods, we show that the proline-rich stretch surrounding P366 mediates binding to syndapin I, an F-BAR domain protein involved in membrane remodeling. The disruption of the noncanonical Src homology 3 recognition motif by P366L reduces syndapin I binding. These data suggest that the GlyRα1 subunit interacts with intracellular binding partners and may therefore play a role in receptor trafficking or synaptic anchoring, a function thus far only ascribed to the GlyRβ subunit. Hence, the P366L GlyRα1 variant exhibits a unique set of properties that cumulatively affect GlyR functionality and thus might explain the neuropathological mechanism underlying hyperekplexia in the mutant carriers. P366L is the first dominant GLRA1 mutation identified within the GlyRα1 TM3-4 loop that affects GlyR physiology without altering protein expression at the whole-cell and surface levels.SIGNIFICANCE STATEMENT We show that the intracellular domain of the inhibitory glycine receptor α1 subunit contributes to trafficking and synaptic anchoring. A proline-rich stretch in this receptor domain forms a noncanonical recognition motif important for the interaction with syndapin I (PACSIN1). The disruption of this motif, as present in a human patient with hyperekplexia led to impaired syndapin I binding. Functional analysis revealed that the altered proline-rich stretch determines several functional physiological parameters of the ion channel (e.g., faster whole-cell desensitization) reduced unitary conductance and spontaneous opening events. Thus, the proline-rich stretch from the glycine receptor α1 subunit represents a multifunctional intracellular protein motif.
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Zhang Y, Wu LL, Zheng XL, Lin CM. C.292G>A, a novel glycine receptor alpha 1 subunit gene (GLRA1) mutation found in a Chinese patient with hyperekplexia: A case report. Medicine (Baltimore) 2020; 99:e19968. [PMID: 32332682 PMCID: PMC7220787 DOI: 10.1097/md.0000000000019968] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
INTRODUCTION Hyperekplexia is a rare hereditary neurological disorder; only 5 glycine receptor alpha 1 subunit gene (GLRA1) mutations have been reported in 5 Chinese patients. We report a Chinese infant with hyperekplexia and a novel mutation at c.292G > A. PATIENT CONCERNS A Chinese infant with hyperekplexia and a novel mutation at c.292G > A. DIAGNOSIS All exons of GLRA1 were sequenced in her parents and her, which revealed a mutation at c.1030C > T and another novel mutation at c.292G > A. Her diagnosis was confirmed as hereditary hyperekplexia with GlRA1 hybrid gene mutations based on the sequencing results. INTERVENTIONS She was treated with clonazepam. OUTCOMES Her muscle hypertonia recovered rapidly and the excessive startle reflex to unexpected stimuli was significantly reduced. CONCLUSION Genetic DNA sequencing is a crucial method for diagnosing hyperekplexia-related gene mutation.
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Wu Y, Chang YM, Polton G, Stell AJ, Szladovits B, Macfarlane M, Peters LM, Priestnall SL, Bacon NJ, Kow K, Stewart S, Sharma E, Goulart MR, Gribben J, Xia D, Garden OA. Gene Expression Profiling of B Cell Lymphoma in Dogs Reveals Dichotomous Metabolic Signatures Distinguished by Oxidative Phosphorylation. Front Oncol 2020; 10:307. [PMID: 32211332 PMCID: PMC7069556 DOI: 10.3389/fonc.2020.00307] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 02/20/2020] [Indexed: 11/13/2022] Open
Abstract
Gene expression profiling has revealed molecular heterogeneity of diffuse large B cell lymphoma (DLBCL) in both humans and dogs. Two DLBCL subtypes based on cell of origin are generally recognized, germinal center B (GCB)-like and activated B cell (ABC)-like. A pilot study to characterize the transcriptomic phenotype of 11 dogs with multicentric BCL yielded two molecular subtypes distinguished on the basis of genes important in oxidative phosphorylation. We propose a metabolic classification of canine BCL that transcends cell of origin and shows parallels to a similar molecular phenotype in human DLBCL. We thus confirm the validity of this classification scheme across widely divergent mammalian taxa and add to the growing body of literature suggesting cellular and molecular similarities between human and canine non-Hodgkin lymphoma. Our data support a One Health approach to the study of DLBCL, including the advancement of novel therapies of relevance to both canine and human health.
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Affiliation(s)
- Ying Wu
- Royal Veterinary College, London, United Kingdom
| | - Yu-Mei Chang
- Royal Veterinary College, London, United Kingdom
| | - Gerry Polton
- North Downs Specialist Referrals, Bletchingley, United Kingdom
| | | | | | | | | | | | | | - Kelvin Kow
- Fitzpatrick Referrals, Guildford, United Kingdom
| | | | - Eshita Sharma
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | | | - John Gribben
- Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Dong Xia
- Royal Veterinary College, London, United Kingdom
| | - Oliver A. Garden
- Royal Veterinary College, London, United Kingdom
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, United States
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Zou G, Xia J, Han Q, Liu D, Xiong W. The synthetic cannabinoid dehydroxylcannabidiol restores the function of a major GABA A receptor isoform in a cell model of hyperekplexia. J Biol Chem 2020; 295:138-145. [PMID: 31757808 PMCID: PMC6952599 DOI: 10.1074/jbc.ra119.011221] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 11/21/2019] [Indexed: 11/06/2022] Open
Abstract
The functions of the glycine receptor (GlyR) and GABAA receptor (GABAAR) are both impaired in hyperekplexia, a neurological disorder usually caused by GlyR mutations. Although emerging evidence indicates that cannabinoids can directly restore normal GlyR function, whether they affect GABAAR in hyperekplexia remains unknown. Here we show that dehydroxylcannabidiol (DH-CBD), a synthetic nonpsychoactive cannabinoid, restores the GABA- and glycine-activated currents (IGABA and IGly , respectively) in HEK293 cells coexpressing a major GABAAR isoform (α1β2γ2) and GlyRα1 carrying a human hyperekplexia-associated mutation (GlyRα1R271Q). Using coimmunoprecipitation and FRET assays, we found that DH-CBD disrupts the protein interaction between GABAAR and GlyRα1R271Q Furthermore, a point mutation of GlyRα1, changing Ser-296 to Ala-296, which is critical for cannabinoid binding on GlyR, significantly blocked DH-CBD-induced restoration of IGABA and IGly currents. This S296A substitution also considerably attenuated DH-CBD-induced disruption of the interaction between GlyRα1R271Q and GABAAR. These findings suggest that, because it restores the functions of both GlyRα1 and GABAAR, DH-CBD may represent a potentially valuable candidate drug to manage hyperekplexia.
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Affiliation(s)
- Guichang Zou
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of the University of Science and Technology of China, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China
| | - Jing Xia
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of the University of Science and Technology of China, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China
| | - Qianqian Han
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Dan Liu
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
| | - Wei Xiong
- Institute on Aging and Brain Disorders, The First Affiliated Hospital of the University of Science and Technology of China, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei 230026, China; Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China; Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China.
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de la Rocha-Muñoz A, Núñez E, Arribas-González E, López-Corcuera B, Aragón C, de Juan-Sanz J. E3 ubiquitin ligases LNX1 and LNX2 are major regulators of the presynaptic glycine transporter GlyT2. Sci Rep 2019; 9:14944. [PMID: 31628376 PMCID: PMC6802383 DOI: 10.1038/s41598-019-51301-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Accepted: 09/27/2019] [Indexed: 12/15/2022] Open
Abstract
The neuronal glycine transporter GlyT2 is an essential regulator of glycinergic neurotransmission that recaptures glycine in presynaptic terminals to facilitate transmitter packaging in synaptic vesicles. Alterations in GlyT2 expression or activity result in lower cytosolic glycine levels, emptying glycinergic synaptic vesicles and impairing neurotransmission. Lack of glycinergic neurotransmission caused by GlyT2 loss-of-function mutations results in Hyperekplexia, a rare neurological disease characterized by generalized stiffness and motor alterations that may cause sudden infant death. Although the importance of GlyT2 in pathology is known, how this transporter is regulated at the molecular level is poorly understood, limiting current therapeutic strategies. Guided by an unbiased screening, we discovered that E3 ubiquitin ligase Ligand of Numb proteins X1/2 (LNX1/2) modulate the ubiquitination status of GlyT2. The N-terminal RING-finger domain of LNX1/2 ubiquitinates a cytoplasmic C-terminal lysine cluster in GlyT2 (K751, K773, K787 and K791), and this process regulates the expression levels and transport activity of GlyT2. The genetic deletion of endogenous LNX2 in spinal cord primary neurons causes an increase in GlyT2 expression and we find that LNX2 is required for PKC-mediated control of GlyT2 transport. This work identifies, to our knowledge, the first E3 ubiquitin-ligases acting on GlyT2, revealing a novel molecular mechanism that controls presynaptic glycine availability. Providing a better understanding of the molecular regulation of GlyT2 may help future investigations into the molecular basis of human disease states caused by dysfunctional glycinergic neurotransmission, such as hyperekplexia and chronic pain.
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Affiliation(s)
- A de la Rocha-Muñoz
- Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049, Madrid, Spain
- IdiPAZ, Hospital Universitario La Paz, Madrid, Spain
| | - E Núñez
- Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049, Madrid, Spain
- IdiPAZ, Hospital Universitario La Paz, Madrid, Spain
| | - E Arribas-González
- Instituto Cajal, Consejo Superior de Investigaciones Científicas, 28002, Madrid, Spain
| | - B López-Corcuera
- Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049, Madrid, Spain
- IdiPAZ, Hospital Universitario La Paz, Madrid, Spain
| | - C Aragón
- Centro de Biología Molecular "Severo Ochoa", Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049, Madrid, Spain.
- IdiPAZ, Hospital Universitario La Paz, Madrid, Spain.
| | - J de Juan-Sanz
- Sorbonne Université and Institut du Cerveau et de la Moelle Epinière (ICM) - Hôpital Pitié-Salpêtrière, Inserm, CNRS, Paris, France.
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Harvey RJ. Hijacking of GABAA Receptors by Mutant Glycine Receptors. Trends Mol Med 2019; 25:823-825. [DOI: 10.1016/j.molmed.2019.08.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Accepted: 08/29/2019] [Indexed: 11/24/2022]
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Kitzenmaier A, Schaefer N, Kasaragod VB, Polster T, Hantschmann R, Schindelin H, Villmann C. The P429L loss of function mutation of the human glycine transporter 2 associated with hyperekplexia. Eur J Neurosci 2019; 50:3906-3920. [DOI: 10.1111/ejn.14533] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 07/23/2019] [Accepted: 07/25/2019] [Indexed: 12/20/2022]
Affiliation(s)
- Alexandra Kitzenmaier
- Institute for Clinical Neurobiology Julius‐Maximilians‐University of Würzburg Würzburg Germany
| | - Natascha Schaefer
- Institute for Clinical Neurobiology Julius‐Maximilians‐University of Würzburg Würzburg Germany
| | - Vikram Babu Kasaragod
- Rudolf Virchow Centre for Experimental Biomedicine Julius‐Maximilians‐University of Würzburg Würzburg Germany
| | - Tilman Polster
- Pediatric Epileptology Mara Hospital Bethel Epilepsy Centre Bielefeld Germany
| | - Ralph Hantschmann
- Center for Developmental Pediatrics and Pediatric Neurology Hagen Germany
| | - Hermann Schindelin
- Rudolf Virchow Centre for Experimental Biomedicine Julius‐Maximilians‐University of Würzburg Würzburg Germany
| | - Carmen Villmann
- Institute for Clinical Neurobiology Julius‐Maximilians‐University of Würzburg Würzburg Germany
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25
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Erdem FA, Ilic M, Koppensteiner P, Gołacki J, Lubec G, Freissmuth M, Sandtner W. A comparison of the transport kinetics of glycine transporter 1 and glycine transporter 2. J Gen Physiol 2019; 151:1035-1050. [PMID: 31270129 PMCID: PMC6683666 DOI: 10.1085/jgp.201912318] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Revised: 04/16/2019] [Accepted: 06/17/2019] [Indexed: 12/20/2022] Open
Abstract
Erdem et al. compare the kinetics of the SLC6 family glycine transporters GlyT1 and GlyT2. Though the two transporters are rate-limited by distinct reaction steps, they both display high transport capacity, with the kinetics of GlyT1 sufficient to supply extracellular glycine to the NMDA receptor. Transporters of the solute carrier 6 (SLC6) family translocate their cognate substrate together with Na+ and Cl−. Detailed kinetic models exist for the transporters of GABA (GAT1/SLC6A1) and the monoamines dopamine (DAT/SLC6A3) and serotonin (SERT/SLC6A4). Here, we posited that the transport cycle of individual SLC6 transporters reflects the physiological requirements they operate under. We tested this hypothesis by analyzing the transport cycle of glycine transporter 1 (GlyT1/SLC6A9) and glycine transporter 2 (GlyT2/SLC6A5). GlyT2 is the only SLC6 family member known to translocate glycine, Na+, and Cl− in a 1:3:1 stoichiometry. We analyzed partial reactions in real time by electrophysiological recordings. Contrary to monoamine transporters, both GlyTs were found to have a high transport capacity driven by rapid return of the empty transporter after release of Cl− on the intracellular side. Rapid cycling of both GlyTs was further supported by highly cooperative binding of cosubstrate ions and substrate such that their forward transport mode was maintained even under conditions of elevated intracellular Na+ or Cl−. The most important differences in the transport cycle of GlyT1 and GlyT2 arose from the kinetics of charge movement and the resulting voltage-dependent rate-limiting reactions: the kinetics of GlyT1 were governed by transition of the substrate-bound transporter from outward- to inward-facing conformations, whereas the kinetics of GlyT2 were governed by Na+ binding (or a related conformational change). Kinetic modeling showed that the kinetics of GlyT1 are ideally suited for supplying the extracellular glycine levels required for NMDA receptor activation.
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Affiliation(s)
- Fatma Asli Erdem
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Marija Ilic
- Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Vienna, Austria
| | | | - Jakub Gołacki
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Gert Lubec
- Neuroproteomics, Paracelsus Private Medical University, Salzburg, Austria
| | - Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Walter Sandtner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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26
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Piard J, Umanah GKE, Harms FL, Abalde-Atristain L, Amram D, Chang M, Chen R, Alawi M, Salpietro V, Rees MI, Chung SK, Houlden H, Verloes A, Dawson TM, Dawson VL, Van Maldergem L, Kutsche K. A homozygous ATAD1 mutation impairs postsynaptic AMPA receptor trafficking and causes a lethal encephalopathy. Brain 2019; 141:651-661. [PMID: 29390050 DOI: 10.1093/brain/awx377] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 11/27/2017] [Indexed: 11/12/2022] Open
Abstract
Members of the AAA+ superfamily of ATPases are involved in the unfolding of proteins and disassembly of protein complexes and aggregates. ATAD1 encoding the ATPase family, AAA+ domain containing 1-protein Thorase plays an important role in the function and integrity of mitochondria and peroxisomes. Postsynaptically, Thorase controls the internalization of excitatory, glutamatergic AMPA receptors by disassembling complexes between the AMPA receptor-binding protein, GRIP1, and the AMPA receptor subunit GluA2. Using whole-exome sequencing, we identified a homozygous frameshift mutation in the last exon of ATAD1 [c.1070_1071delAT; p.(His357Argfs*15)] in three siblings who presented with a severe, lethal encephalopathy associated with stiffness and arthrogryposis. Biochemical and cellular analyses show that the C-terminal end of Thorase mutant gained a novel function that strongly impacts its oligomeric state, reduces stability or expression of a set of Golgi, peroxisomal and mitochondrial proteins and affects disassembly of GluA2 and Thorase oligomer complexes. Atad1-/- neurons expressing Thorase mutantHis357Argfs*15 display reduced amount of GluA2 at the cell surface suggesting that the Thorase mutant may inhibit the recycling back and/or reinsertion of AMPA receptors to the plasma membrane. Taken together, our molecular and functional analyses identify an activating ATAD1 mutation as a new cause of severe encephalopathy and congenital stiffness.
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Affiliation(s)
- Juliette Piard
- Centre de génétique humaine, Université de Franche-Comté, Besançon, France.,Integrative and Cognitive Neurosciences Research Unit EA481, University of Franche-Comté, Besançon, France
| | - George K Essien Umanah
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Frederike L Harms
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Leire Abalde-Atristain
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Cellular and Molecular Medicine Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Daniel Amram
- Unité fonctionnelle de génétique clinique, Centre hospitalier intercommunal, Créteil, France
| | - Melissa Chang
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Rong Chen
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Malik Alawi
- University Medical Center Hamburg-Eppendorf, Bioinformatics Core Facility, 20246 Hamburg, Germany.,Heinrich-Pette-Institute, Leibniz-Institute for Experimental Virology, Virus Genomics, Hamburg, Germany
| | - Vincenzo Salpietro
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Mark I Rees
- Neurology Research Group, Institute of Life Science, Swansea University Medical School, Swansea University, Swansea, UK
| | - Seo-Kyung Chung
- Neurology Research Group, Institute of Life Science, Swansea University Medical School, Swansea University, Swansea, UK
| | - Henry Houlden
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Alain Verloes
- Department of Genetics, Robert-Debré Hospital, Paris, France
| | - Ted M Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Cellular and Molecular Medicine Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Valina L Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Cellular and Molecular Medicine Graduate Program, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Lionel Van Maldergem
- Centre de génétique humaine, Université de Franche-Comté, Besançon, France.,Integrative and Cognitive Neurosciences Research Unit EA481, University of Franche-Comté, Besançon, France.,Clinical Investigation Center 1431, National Institute of Health and Medical Research (INSERM), University of Franche-Comté, Besançon, France
| | - Kerstin Kutsche
- Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
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27
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Benito-Muñoz C, Perona A, Abia D, Dos Santos HG, Núñez E, Aragón C, López-Corcuera B. Modification of a Putative Third Sodium Site in the Glycine Transporter GlyT2 Influences the Chloride Dependence of Substrate Transport. Front Mol Neurosci 2018; 11:347. [PMID: 30319354 PMCID: PMC6166138 DOI: 10.3389/fnmol.2018.00347] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 09/04/2018] [Indexed: 11/13/2022] Open
Abstract
Neurotransmitter removal from glycine-mediated synapses relies on two sodium-driven high-affinity plasma membrane GlyTs that control neurotransmitter availability. Mostly glial GlyT1 is the main regulator of glycine synaptic levels, whereas neuronal GlyT2 promotes the recycling of synaptic glycine and supplies neurotransmitter for presynaptic vesicle refilling. The GlyTs differ in sodium:glycine symport stoichiometry, showing GlyT1 a 2:1 and GlyT2 a 3:1 sodium:glycine coupling. Sodium binds to the GlyTs at two conserved Na+ sites: Na1 and Na2. The location of GlyT2 Na3 site remains unknown, although Glu650 has been involved in the coordination. Here, we have used comparative MD simulations of a GlyT2 model constructed by homology to the crystalized DAT from Drosophila melanogaster by placing the Na3 ion at two different locations. By combination of in silico and experimental data obtained by biochemical and electrophysiological analysis of GlyTs mutants, we provide evidences suggesting the GlyT2 third sodium ion is held by Glu-250 and Glu-650, within a region with robust allosteric properties involved in cation-specific sensitivity. Substitution of Glu650 in GlyT2 by the corresponding methionine in GlyT1 reduced the charge-to-flux ratio to the level of GlyT1 without producing transport uncoupling. Chloride dependence of glycine transport was almost abolished in this GlyT2 mutant but simultaneous substitution of Glu250 and Glu650 by neutral amino acids rescued chloride sensitivity, suggesting that protonation/deprotonation of Glu250 substitutes chloride function. The differential behavior of equivalent GlyT1 mutations sustains a GlyT2-specific allosteric coupling between the putative Na3 site and the chloride site.
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Affiliation(s)
- Cristina Benito-Muñoz
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Almudena Perona
- Smartligs, Parque Científico de Madrid, Campus de Cantoblanco, Madrid, Spain
| | - David Abia
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Helena G Dos Santos
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Enrique Núñez
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Carmen Aragón
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
| | - Beatriz López-Corcuera
- Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular, "Severo Ochoa" Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid, Spain
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28
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Kandasamy P, Gyimesi G, Kanai Y, Hediger MA. Amino acid transporters revisited: New views in health and disease. Trends Biochem Sci 2018; 43:752-789. [PMID: 30177408 DOI: 10.1016/j.tibs.2018.05.003] [Citation(s) in RCA: 252] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 02/09/2023]
Abstract
Amino acid transporters (AATs) are membrane-bound transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs have diverse functional roles ranging from neurotransmission to acid-base balance, intracellular energy metabolism, and anabolic and catabolic reactions. In cancer cells and diabetes, dysregulation of AATs leads to metabolic reprogramming, which changes intracellular amino acid levels, contributing to the pathogenesis of cancer, obesity and diabetes. Indeed, the neutral amino acid transporters (NATs) SLC7A5/LAT1 and SLC1A5/ASCT2 are likely involved in several human malignancies. However, a clinical therapy that directly targets AATs has not yet been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, their diverse physiological roles in different tissues and organs, their wide-ranging implications in human diseases and the emerging strategies and tools that will be necessary to target AATs therapeutically.
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Affiliation(s)
- Palanivel Kandasamy
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Gergely Gyimesi
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland
| | - Yoshikatsu Kanai
- Division of Bio-system Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan.
| | - Matthias A Hediger
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstrasse 28, CH-3012 Bern, Switzerland.
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29
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Rao CV, Farooqui M, Zhang Y, Asch AS, Yamada HY. Spontaneous development of Alzheimer's disease-associated brain pathology in a Shugoshin-1 mouse cohesinopathy model. Aging Cell 2018; 17:e12797. [PMID: 29943428 PMCID: PMC6052391 DOI: 10.1111/acel.12797] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 05/04/2018] [Accepted: 05/27/2018] [Indexed: 12/14/2022] Open
Abstract
Spontaneous late-onset Alzheimer's disease (LOAD) accounts for more than 95% of all human AD. As mice do not normally develop AD and as understanding on molecular processes leading to spontaneous LOAD has been insufficient to successfully model LOAD in mouse, no mouse model for LOAD has been available. Existing mouse AD models are all early-onset AD (EOAD) models that rely on forcible expression of AD-associated protein(s), which may not recapitulate prerequisites for spontaneous LOAD. This limitation in AD modeling may contribute to the high failure rate of AD drugs in clinical trials. In this study, we hypothesized that genomic instability facilitates development of LOAD and tested two genomic instability mice models in the brain pathology at the old age. Shugoshin-1 (Sgo1) haploinsufficient (∓) mice, a model of chromosome instability (CIN) with chromosomal and centrosomal cohesinopathy, spontaneously exhibited a major feature of AD pathology; amyloid beta accumulation that colocalized with phosphorylated Tau, beta-secretase 1 (BACE), and mitotic marker phospho-Histone H3 (p-H3) in the brain. Another CIN model, spindle checkpoint-defective BubR1-/+ haploinsufficient mice, did not exhibit the pathology at the same age, suggesting the prolonged mitosis-origin of the AD pathology. RNA-seq identified ten differentially expressed genes, among which seven genes have indicated association with AD pathology or neuronal functions (e.g., ARC, EBF3). Thus, the model represents a novel model that recapitulates spontaneous LOAD pathology in mouse. The Sgo1-/+ mouse may serve as a novel tool for investigating mechanisms of spontaneous progression of LOAD pathology, for early diagnosis markers, and for drug development.
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Affiliation(s)
- Chinthalapally V. Rao
- Center for Cancer Prevention and Drug DevelopmentDepartment of MedicineHematology/Oncology SectionUniversity of Oklahoma Health Sciences Center (OUHSC)Oklahoma CityOklahoma
| | - Mudassir Farooqui
- Center for Cancer Prevention and Drug DevelopmentDepartment of MedicineHematology/Oncology SectionUniversity of Oklahoma Health Sciences Center (OUHSC)Oklahoma CityOklahoma
| | - Yuting Zhang
- Center for Cancer Prevention and Drug DevelopmentDepartment of MedicineHematology/Oncology SectionUniversity of Oklahoma Health Sciences Center (OUHSC)Oklahoma CityOklahoma
| | - Adam S. Asch
- Stephenson Cancer CenterDepartment of MedicineHematology/Oncology SectionUniversity of Oklahoma Health Sciences Center (OUHSC)Oklahoma CityOklahoma
| | - Hiroshi Y. Yamada
- Center for Cancer Prevention and Drug DevelopmentDepartment of MedicineHematology/Oncology SectionUniversity of Oklahoma Health Sciences Center (OUHSC)Oklahoma CityOklahoma
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30
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López-Corcuera B, Arribas-González E, Aragón C. Hyperekplexia-associated mutations in the neuronal glycine transporter 2. Neurochem Int 2018; 123:95-100. [PMID: 29859229 DOI: 10.1016/j.neuint.2018.05.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 05/26/2018] [Accepted: 05/29/2018] [Indexed: 12/20/2022]
Abstract
Hyperekplexia or startle disease is a dysfunction of inhibitory glycinergic neurotransmission characterized by an exaggerated startle in response to trivial tactile or acoustic stimuli. Although rare, this disorder can have serious consequences, including sudden infant death. One of the most frequent causes of hyperekplexia are mutations in the SLC6A5 gene, encoding the neuronal glycine transporter 2 (GlyT2), a key component of inhibitory glycinergic presynapses involved in synaptic glycine recycling though sodium and chloride-dependent co-transport. Most GlyT2 mutations detected so far are recessive, but two dominant missense mutations have been described. The detailed analysis of these mutations has revealed structural cues on the quaternary structure of GlyT2, and opens the possibility that novel selective pharmacochaperones have potential therapeutic effects in hyperekplexia.
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Affiliation(s)
- Beatriz López-Corcuera
- Centro de Biología Molecular ''Severo Ochoa'', Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain.
| | - Esther Arribas-González
- Centro de Biología Molecular ''Severo Ochoa'', Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain
| | - Carmen Aragón
- Centro de Biología Molecular ''Severo Ochoa'', Universidad Autónoma de Madrid-Consejo Superior de Investigaciones Científicas, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid, Spain
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31
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Yang Z, Sun G, Yao F, Tao D, Zhu B. A novel compound mutation in GLRA1 cause hyperekplexia in a Chinese boy- a case report and review of the literature. BMC MEDICAL GENETICS 2017; 18:110. [PMID: 28985719 PMCID: PMC5631533 DOI: 10.1186/s12881-017-0476-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 10/03/2017] [Indexed: 11/10/2022]
Abstract
Background The pathogenesis of hereditary hyperekplexia is thought to involve abnormalities in the glycinergic neurotransmission system, the most of mutations reported in GLRA1. This gene encodes the glycine receptor α1 subunit, which has an extracellular domain (ECD) and a transmembrane domain (TMD) with 4 α-helices (TM1–TM4). Case presentation We investigated the genetic cause of hyperekplexia in a Chinese family with one affected member. Whole-exome sequencing of the 5 candidate genes was performed on the proband patient, and direct sequencing was performed to validate and confirm the detected mutation in other family members. We also review and analyse all reported GLRA1 mutations. The proband had a compound heterozygous GLRA1 mutation that comprised 2 novel GLRA1 missense mutations, C.569C > T (p.T190 M) from the mother and C.1270G > A (p.D424N) from the father. SIFT, Polyphen-2 and MutationTaster analysis identified the mutations as disease-causing, but the parents had no signs of hyperekplexia. The p.T190 M mutation is located in the ECD, while p.D424N is located in TM4. Conclusions Our findings contribute to a growing list GLRA1 mutations associated with hyperekplexia and provide new insights into correlations between phenotype and GLRA1 mutations. Some recessive mutations can induce hyperekplexia in combination with other recessive GLRA1 mutations. Mutations in the ECD, TM1, TM1-TM2 loop, TM3, TM3-TM4 loop and TM4 are more often recessive and part of a compound mutation, while those in TM2 and the TM2-TM3 loop are more likely to be dominant hereditary mutations. Electronic supplementary material The online version of this article (10.1186/s12881-017-0476-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zhiliang Yang
- Department of Pediatrics, The First Hospital of China Medical University, No. 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China.
| | - Guilian Sun
- Department of Pediatrics, The First Hospital of China Medical University, No. 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Fang Yao
- Department of Pediatrics, The First Hospital of China Medical University, No. 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Dongying Tao
- Department of Pediatrics, The First Hospital of China Medical University, No. 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
| | - Binlu Zhu
- Department of Pediatrics, The First Hospital of China Medical University, No. 155 Nanjing North Street, Heping District, Shenyang, 110001, Liaoning Province, People's Republic of China
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32
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Asjad HMM, Kasture A, El-Kasaby A, Sackel M, Hummel T, Freissmuth M, Sucic S. Pharmacochaperoning in a Drosophila model system rescues human dopamine transporter variants associated with infantile/juvenile parkinsonism. J Biol Chem 2017; 292:19250-19265. [PMID: 28972153 PMCID: PMC5702666 DOI: 10.1074/jbc.m117.797092] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 09/06/2017] [Indexed: 12/19/2022] Open
Abstract
Point mutations in the gene encoding the human dopamine transporter (hDAT, SLC6A3) cause a syndrome of infantile/juvenile dystonia and parkinsonism. To unravel the molecular mechanism underlying these disorders and investigate possible pharmacological therapies, here we examined 13 disease-causing DAT mutants that were retained in the endoplasmic reticulum when heterologously expressed in HEK293 cells. In three of these mutants, i.e. hDAT-V158F, hDAT-G327R, and hDAT-L368Q, the folding deficit was remedied with the pharmacochaperone noribogaine or the heat shock protein 70 (HSP70) inhibitor pifithrin-μ such that endoplasmic reticulum export of and radioligand binding and substrate uptake by these DAT mutants were restored. In Drosophila melanogaster, DAT deficiency results in reduced sleep. We therefore exploited the power of targeted transgene expression of mutant hDAT in Drosophila to explore whether these hDAT mutants could also be pharmacologically rescued in an intact organism. Noribogaine or pifithrin-μ treatment supported hDAT delivery to the presynaptic terminals of dopaminergic neurons and restored sleep to normal length in DAT-deficient (fumin) Drosophila lines expressing hDAT-V158F or hDAT-G327R. In contrast, expression of hDAT-L368Q in the Drosophila DAT mutant background caused developmental lethality, indicating a toxic action not remedied by pharmacochaperoning. Our observations identified those mutations most likely amenable to pharmacological rescue in the affected children. In addition, our findings also highlight the challenges of translating insights from pharmacochaperoning in cell culture to the clinical situation. Because of the evolutionary conservation in dopaminergic neurotransmission between Drosophila and people, pharmacochaperoning of DAT in D. melanogaster may allow us to bridge that gap.
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Affiliation(s)
- H M Mazhar Asjad
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ameya Kasture
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ali El-Kasaby
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Michael Sackel
- the Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Thomas Hummel
- the Department of Neurobiology, University of Vienna, A-1090 Vienna, Austria
| | - Michael Freissmuth
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Sonja Sucic
- From the Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
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33
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Cioffi CL. Modulation of Glycine-Mediated Spinal Neurotransmission for the Treatment of Chronic Pain. J Med Chem 2017; 61:2652-2679. [PMID: 28876062 DOI: 10.1021/acs.jmedchem.7b00956] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Chronic pain constitutes a significant and expanding worldwide health crisis. Currently available analgesics poorly serve individuals suffering from chronic pain, and new therapeutic agents that are more effective, safer, and devoid of abuse liabilities are desperately needed. Among the myriad of cellular and molecular processes contributing to chronic pain, spinal disinhibition of pain signaling to higher cortical centers plays a critical role. Accumulating evidence shows that glycinergic inhibitory neurotransmission in the spinal cord dorsal horn gates nociceptive signaling, is essential in maintaining physiological pain sensitivity, and is diminished in pathological pain states. Thus, it is hypothesized that agents capable of enhancing glycinergic tone within the dorsal horn could obtund nociceptor signaling to the brain and serve as analgesics for persistent pain. This Perspective highlights the potential that pharmacotherapies capable of increasing inhibitory spinal glycinergic neurotransmission hold in providing new and transformative analgesic therapies for the treatment of chronic pain.
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Affiliation(s)
- Christopher L Cioffi
- Departments of Basic and Clinical Sciences and Pharmaceutical Sciences , Albany College of Pharmacy and Health Sciences , 106 New Scotland Avenue , Albany , New York 12208 United States
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Kakizaki T, Sakagami H, Sakimura K, Yanagawa Y. A glycine transporter 2-Cre knock-in mouse line for glycinergic neuron-specific gene manipulation. IBRO Rep 2017; 3:9-16. [PMID: 30135938 PMCID: PMC6084908 DOI: 10.1016/j.ibror.2017.07.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/24/2017] [Accepted: 07/24/2017] [Indexed: 01/16/2023] Open
Abstract
Glycine is an inhibitory neurotransmitter in the brainstem and spinal cord. Glycine transporter 2 (GLYT2) is responsible for the uptake of extracellular glycine. GLYT2 is specifically expressed in glycinergic neurons and thus has been used as a marker of glycinergic neurons. Here, we generated GLYT2 promotor-driven Cre recombinase (Cre)-expressing mice (GLYT2-Cre knock-in mice) to develop a tool for manipulating gene expression in glycinergic neurons. Cre activity was examined by crossing the GLYT2-Cre knock-in mice with a Cre reporter mouse line, R26R, which express β-galactosidase (β-gal) in a Cre-dependent manner. X-gal staining of GLYT2-Cre/R26R double transgenic mouse brains and spinal cords revealed that the Cre activity was primarily distributed in the brainstem, cerebellum, and spinal cord. These areas are rich in glycinergic neurons. Furthermore, we performed immunohistochemistry for β-gal combined with in situ hybridization for GLYT2 in the GLYT2-Cre/R26R double transgenic mouse brains to determine whether Cre activity is specifically localized to glycinergic neurons. The β-gal protein and GLYT2 mRNAs were colocalized in the cerebellar Golgi cells, dorsal cochlear nucleus, gigantocellular reticular nucleus, spinal trigeminal nucleus, nucleus of the trapezoid body, and lateral lemniscus. More than 98% of the GLYT2 mRNA-expressing cells in these brain regions also expressed β-gal, whereas 90–98% of the β-gal-positive cells expressed the GLYT2 mRNAs. Thus, Cre activity is specifically localized to glycinergic neurons with high fidelity in the GLYT2-Cre knock-in mice. The GLYT2-Cre knock-in mouse line will be a useful tool for studying glycinergic neurons and neurotransmission.
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Affiliation(s)
- Toshikazu Kakizaki
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 228-8555, Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata 951-8585, Japan
| | - Yuchio Yanagawa
- Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, Maebashi 371-8511, Japan
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Masri A, Chung SK, Rees MI. Hyperekplexia: Report on phenotype and genotype of 16 Jordanian patients. Brain Dev 2017; 39:306-311. [PMID: 27843043 DOI: 10.1016/j.braindev.2016.10.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/15/2016] [Accepted: 10/20/2016] [Indexed: 10/20/2022]
Abstract
BACKGROUND Hyperekplexia, is a rare disorder characterized by excessive startle response to acoustic, visual, or other stimuli. It is inherited in autosomal recessive and dominant pattern. OBJECTIVE To describe the clinical and genetic features of hyperekplexia in Jordanian patients. METHODS This retrospective study includes all patients with proved genetic diagnosis of hyperekplexia who presented to our clinic at the Jordan University Hospital from January 2001 through July 2015. RESULTS A total of 16 children from 12 families were included. The total follow up period ranged from one to eleven years. The majority of the patients (13/16=81.3%) were initially misdiagnosed as epilepsy. All patients had excessive startle response since birth. Tonic-apneic spells occurred in 15/16=93.8% patients. Fourteen patients (45/16=87.5%) received clonazepam. Stopping clonazepam by three years of age failed in 11/14 (78.6%) due to reappearance of tonic-apneic spells (8/14=57.1%), recurrent falling (10/14=71.4%) or due to both reasons (5/14=35.7%). Delayed motor development occurred in 7/16 (43.8%), speech delay in 4/16 (25.0%), global developmental delay in 1/16 (6.3%), and autism spectrum disorder in 1/16 (6.3%) patient. The mode of inheritance is autosomal recessive in all 12/12 (100%) families. Mutations in GLRA1 gene was present in 9/16 (56.3%); the most common mutation was in p.G254D (4/9; 44.5%). Mutations in the GLRB gene was present in 4/16 (25.0%) patients and the SLC6A5 gene in 3/16 (18.8%) patients. CONCLUSION The clinical presentation of hyperekplexia in Jordanian patients is manifested by tonic-apneic spells in all homozygous patients. The persistence of apneic spells and recurrent falls throughout childhood necessitate continuous treatment and surveillance.
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Affiliation(s)
- Amira Masri
- Faculty of Medicine, The University of Jordan, P.O. Box 1612 Code, 11941 Amman, Jordan.
| | - Seo-Kyung Chung
- Institute of Life Sciences, Swansea University Medical School, Swansea University, UK.
| | - Mark I Rees
- Institute of Life Sciences, Swansea University Medical School, Swansea University, UK.
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Abstract
PURPOSE OF REVIEW This review highlights the recent developments in immune-mediated movement disorders and how they reflect on clinical practice and our understanding of the underlying pathophysiological mechanisms. RECENT FINDINGS The antibody spectrum associated with stiff person syndrome and related disorders (SPSD) has broadened and, apart from the classic glutamic acid decarboxylase (GAD)- and amphiphysin-antibodies, includes now also antibodies against dipeptidyl-peptidase-like protein-6 (DPPX), gamma-aminobutyric acid type A receptor (GABAAR), glycine receptor (GlyR) and glycine transporter 2 (GlyT2). The field of movement disorders with neuronal antibodies keeps expanding with the discovery for example of antibodies against leucine rich glioma inactivated protein 1 (LGI1) and contactin associated protein 2 (Caspr2) in chorea, or antibodies targeting ARHGAP26- or Na/K ATPase alpha 3 subunit (ATP1A3) in cerebellar ataxia. Moreover, neuronal antibodies may partly account for movement disorders attributed for example to Sydenham's chorea, coeliac disease, or steroid responsive encephalopathy with thyroid antibodies. Lastly, there is an interface of immunology, genetics and neurodegeneration, e.g. in Aicardi-Goutières syndrome or the tauopathy with IgLON5-antibodies. SUMMARY Clinicians should be aware of new antibodies such as dipeptidyl-peptidase-like protein-6, gamma-aminobutyric acid type A receptor and glycine transporter 2 in stiff person syndrome and related disorders, as well as of the expanding spectrum of immune-mediated movement disorders.
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Freissmuth M, Stockner T, Sucic S. SLC6 Transporter Folding Diseases and Pharmacochaperoning. Handb Exp Pharmacol 2017; 245:249-270. [PMID: 29086036 DOI: 10.1007/164_2017_71] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The human genome encodes 19 genes of the solute carrier 6 (SLC6) family; non-synonymous changes in the coding sequence give rise to mutated transporters, which are misfolded and thus cause diseases in the affected individuals. Prominent examples include mutations in the transporters for dopamine (DAT, SLC6A3), for creatine (CT1, SLC6A8), and for glycine (GlyT2, SLC6A5), which result in infantile dystonia, mental retardation, and hyperekplexia, respectively. Thus, there is an obvious unmet medical need to identify compounds, which can remedy the folding deficit. The pharmacological correction of folding defects was originally explored in mutants of the serotonin transporter (SERT, SLC6A4), which were created to study the COPII-dependent export from the endoplasmic reticulum. This led to the serendipitous discovery of the pharmacochaperoning action of ibogaine. Ibogaine and its metabolite noribogaine also rescue several disease-relevant mutants of DAT. Because the pharmacology of DAT and SERT is exceptionally rich, it is not surprising that additional compounds have been identified, which rescue folding-deficient mutants. These compounds are not only of interest for restoring DAT function in the affected children. They are also likely to serve as useful tools to interrogate the folding trajectory of the transporter. This is likely to initiate a virtuous cycle: if the principles underlying folding of SLC6 transporters are understood, the design of pharmacochaperones ought to be facilitated.
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Affiliation(s)
- Michael Freissmuth
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria.
| | - Thomas Stockner
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Sonja Sucic
- Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, Vienna, Austria
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Glycinergic transmission: glycine transporter GlyT2 in neuronal pathologies. Neuronal Signal 2016; 1:NS20160009. [PMID: 32714574 PMCID: PMC7377260 DOI: 10.1042/ns20160009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 11/04/2016] [Accepted: 11/09/2016] [Indexed: 11/17/2022] Open
Abstract
Glycinergic neurons are major contributors to the regulation of neuronal excitability, mainly in caudal areas of the nervous system. These neurons control fluxes of sensory information between the periphery and the CNS and diverse motor activities like locomotion, respiration or vocalization. The phenotype of a glycinergic neuron is determined by the expression of at least two proteins: GlyT2, a plasma membrane transporter of glycine, and VIAAT, a vesicular transporter shared by glycine and GABA. In this article, we review recent advances in understanding the role of GlyT2 in the pathophysiology of inhibitory glycinergic neurotransmission. GlyT2 mutations are associated to decreased glycinergic function that results in a rare movement disease termed hyperekplexia (HPX) or startle disease. In addition, glycinergic neurons control pain transmission in the dorsal spinal cord and their function is reduced in chronic pain states. A moderate inhibition of GlyT2 may potentiate glycinergic inhibition and constitutes an attractive target for pharmacological intervention against these devastating conditions.
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Advances in understanding the functions of native GlyT1 and GlyT2 neuronal glycine transporters. Neurochem Int 2016; 99:169-177. [DOI: 10.1016/j.neuint.2016.07.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 07/05/2016] [Accepted: 07/05/2016] [Indexed: 11/20/2022]
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Aubrey KR. Presynaptic control of inhibitory neurotransmitter content in VIAAT containing synaptic vesicles. Neurochem Int 2016; 98:94-102. [PMID: 27296116 DOI: 10.1016/j.neuint.2016.06.002] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 05/21/2016] [Accepted: 06/07/2016] [Indexed: 12/13/2022]
Abstract
In mammals, fast inhibitory neurotransmission is carried out by two amino acid transmitters, γ-aminobutyric acid (GABA) and glycine. The higher brain uses only GABA, but in the spinal cord and brain stem both GABA and glycine act as inhibitory signals. In some cases GABA and glycine are co-released from the same neuron where they are co-packaged into synaptic vesicles by a shared vesicular inhibitory amino acid transporter, VIAAT (also called vGAT). The vesicular content of all other classical neurotransmitters (eg. glutamate, monoamines, acetylcholine) is determined by the presence of a specialized vesicular transporter. Because VIAAT is non-specific, the phenotype of inhibitory synaptic vesicles is instead predicted to be dependent on the relative concentration of GABA and glycine in the cytosol of the presynaptic terminal. This predicts that changes in GABA or glycine supply should be reflected in vesicle transmitter content but as yet, the mechanisms that control GABA versus glycine uptake into synaptic vesicles and their potential for modulation are not clearly understood. This review summarizes the most relevant experimental data that examines the link between GABA and glycine accumulation in the presynaptic cytosol and the inhibitory vesicle phenotype. The accumulated evidence challenges the hypothesis that vesicular phenotype is determined simply by the competition of inhibitory transmitter for VIAAT and instead suggest that the GABA/glycine balance in vesicles is dynamically regulated.
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Affiliation(s)
- Karin R Aubrey
- Pain Management Research Institute, Kolling Institute of Medical Research & Northern Clinical School, University of Sydney at Royal North Shore Hospital, Pacific Hwy, St Leonards, NSW, 2065, Australia.
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Winczewska-Wiktor A, Badura-Stronka M, Monies-Nowicka A, Nowicki MM, Steinborn B, Latos-Bieleńska A, Monies D. A de novo CTNNB1 nonsense mutation associated with syndromic atypical hyperekplexia, microcephaly and intellectual disability: a case report. BMC Neurol 2016; 16:35. [PMID: 26968164 PMCID: PMC4788907 DOI: 10.1186/s12883-016-0554-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 02/26/2016] [Indexed: 11/23/2022] Open
Abstract
Background In addition to its role in cell adhesion and gene expression in the canonical Wingless/integrated Wnt signaling pathway, β-catenin also regulates genes that underlie the transmission of nerve impulses. Mutations of CTNNB1 (β-catenin) have recently been described in patients with a wide range of neurodevelopmental disorders (intellectual disability, microcephaly and other syndromic features). We for the first time associate CTNNB1 mutation with hyperekplexia identifying it as an additional candidate for consideration in patients with startle syndrome. Case presentation We describe an 11 year old male Polish patient with a de novo nonsense mutation in CTNNB1 who in addition to the major features of CTNNB1-related syndrome including intellectual disability and microcephaly, exhibited hyperekplexia and apraxia of upward gaze. The patient became symptomatic at the age of 20 months exhibiting delayed speech and psychomotor development. Social and emotional development was normal but mild hyperactivity was noted. Episodic falls when startled by noise or touch were observed from the age of 8.5 years, progressively increasing but never with loss of consciousness. Targeted gene panel next generation sequencing (NGS) and patient-parents trio analysis revealed a heterozygous de novo nonsense mutation in exon 3 of CTNNB1 identifying a novel association of β-catenin with hyperekplexia. Conclusion We report for the first time a clear association of mutation in CTNNB1 with an atypical syndromic heperekplexia expanding the phenotype of CTNNB1-related syndrome. Consequently CTNNB1 should be added to the growing list of genes to be considered as a cause of startle disease or syndromic hyperekplexia.
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Affiliation(s)
- Anna Winczewska-Wiktor
- Chair and Department of Child Neurology, Poznan University of Medical Sciences, Poznan, Poland
| | - Magdalena Badura-Stronka
- Chair and Department of Medical Genetics, Poznan University of Medical Sciences, ul. Rokietnicka 8, 60-608, Poznań, Poland.
| | | | | | - Barbara Steinborn
- Chair and Department of Child Neurology, Poznan University of Medical Sciences, Poznan, Poland
| | - Anna Latos-Bieleńska
- Chair and Department of Medical Genetics, Poznan University of Medical Sciences, ul. Rokietnicka 8, 60-608, Poznań, Poland
| | - Dorota Monies
- Department of Genetics, King Faisal Hospital and Research Centre, Riyadh, Saudi Arabia
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42
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Maleeva GV, Bregestovski PD. [GLYCINE RECEPTOR: MOLECULAR ORGANIZATION AND PATHOLOGY]. ACTA ACUST UNITED AC 2016; 61:107-17. [PMID: 26845851 DOI: 10.15407/fz61.05.107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glycine receptor is the anion-selective channel, providing fast synaptic transmission in the central nervous system of vertebrates. Together with the nicotinic acetylcholine, GABA and serotonin (5-HT3R) receptors, it belongs to the superfamily of pentameric cys-loop receptors. In this review we briefly describe main functions of these transmembrane proteins, their distribution and molecular architecture. Special attention is paid to recent studies on the molecular physiology of these receptors, as well as on presenting of molecular domains responsible for their dysfunction.
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MESH Headings
- Acetylcholine/metabolism
- Central Nervous System/metabolism
- Central Nervous System/physiopathology
- Gene Expression
- Humans
- Ion Transport
- Mutation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, GABA/chemistry
- Receptors, GABA/genetics
- Receptors, GABA/metabolism
- Receptors, Glycine/chemistry
- Receptors, Glycine/genetics
- Receptors, Glycine/metabolism
- Receptors, Nicotinic/chemistry
- Receptors, Nicotinic/genetics
- Receptors, Nicotinic/metabolism
- Receptors, Serotonin, 5-HT3/chemistry
- Receptors, Serotonin, 5-HT3/genetics
- Receptors, Serotonin, 5-HT3/metabolism
- Reflex, Startle/genetics
- Serotonin/metabolism
- Synaptic Transmission
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Spillane J, Kullmann DM, Hanna MG. Genetic neurological channelopathies: molecular genetics and clinical phenotypes. J Neurol Neurosurg Psychiatry 2016; 87:37-48. [PMID: 26558925 PMCID: PMC4717447 DOI: 10.1136/jnnp-2015-311233] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 09/13/2015] [Indexed: 01/08/2023]
Abstract
Evidence accumulated over recent years has shown that genetic neurological channelopathies can cause many different neurological diseases. Presentations relating to the brain, spinal cord, peripheral nerve or muscle mean that channelopathies can impact on almost any area of neurological practice. Typically, neurological channelopathies are inherited in an autosomal dominant fashion and cause paroxysmal disturbances of neurological function, although the impairment of function can become fixed with time. These disorders are individually rare, but an accurate diagnosis is important as it has genetic counselling and often treatment implications. Furthermore, the study of less common ion channel mutation-related diseases has increased our understanding of pathomechanisms that is relevant to common neurological diseases such as migraine and epilepsy. Here, we review the molecular genetic and clinical features of inherited neurological channelopathies.
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Affiliation(s)
- J Spillane
- Royal Free Hospital Foundation Trust London, London, UK MRC Centre for Neuromuscular Disease, UCL, London, UK
| | - D M Kullmann
- MRC Centre for Neuromuscular Disease, UCL, London, UK UCL, Institute of Neurology, London, UK
| | - M G Hanna
- MRC Centre for Neuromuscular Disease, UCL, London, UK UCL, Institute of Neurology, London, UK
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Koban F, El-Kasaby A, Häusler C, Stockner T, Simbrunner BM, Sitte HH, Freissmuth M, Sucic S. A salt bridge linking the first intracellular loop with the C terminus facilitates the folding of the serotonin transporter. J Biol Chem 2015; 290:13263-78. [PMID: 25869136 PMCID: PMC4505579 DOI: 10.1074/jbc.m115.641357] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Indexed: 12/13/2022] Open
Abstract
The folding trajectory of solute carrier 6 (SLC6) family members is of interest because point mutations result in misfolding and thus cause clinically relevant phenotypes in people. Here we examined the contribution of the C terminus in supporting folding of the serotonin transporter (SERT; SLC6A4). Our working hypothesis posited that the amphipathic nature of the C-terminal α-helix (Thr603–Thr613) was important for folding of SERT. Accordingly, we disrupted the hydrophobic moment of the α-helix by replacing Phe604, Ile608, or Ile612 by Gln. The bulk of the resulting mutants SERT-F604Q, SERT-I608Q, and SERT-I612Q were retained in the endoplasmic reticulum, but their residual delivery to the cell surface still depended on SEC24C. This indicates that the amphipathic nature of the C-terminal α-helix was dispensable to endoplasmic reticulum export. The folding trajectory of SERT is thought to proceed through the inward facing conformation. Consistent with this conjecture, cell surface expression of the misfolded mutants was restored by (i) introducing second site suppressor mutations, which trap SERT in the inward facing state, or (ii) by the pharmacochaperone noribogaine, which binds to the inward facing conformation. Finally, mutation of Glu615 at the end of the C-terminal α-helix to Lys reduced surface expression of SERT-E615K. A charge reversal mutation in intracellular loop 1 restored surface expression of SERT-R152E/E615K to wild type levels. These observations support a mechanistic model where the C-terminal amphipathic helix is stabilized by an intramolecular salt bridge between residues Glu615 and Arg152. This interaction acts as a pivot in the conformational search associated with folding of SERT.
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Affiliation(s)
- Florian Koban
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Ali El-Kasaby
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and the Department of Pharmacology, Faculty of Veterinary Medicine, Mansoura University, 35516 Mansoura, Egypt
| | - Cornelia Häusler
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Thomas Stockner
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Benedikt M Simbrunner
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Harald H Sitte
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Michael Freissmuth
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
| | - Sonja Sucic
- From the Institute of Pharmacology, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria and
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Abstract
Trismus is a rare presentation affecting neonates, children, and adults. In newborns there are serious implications, with potential to affect feeding, cause airway problems, and make intubation difficult. Causes of trismus seen in the paediatric patient are discussed in this review article; they are divided into intra- and extra-articular types. The extra-articular group consists of congenital and acquired disorders. The acquired group includes infective causes such as tetanus, iatrogenic causes related to drugs, cancer or dental treatment, and trauma causing articulation difficulty or triggering a rare type of bone growth in myositis ossificans. Changes in the mouth resulting from oral submucous fibrosis can undergo malignant transformation. This review aims to raise awareness of potential causes of trismus in paediatric populations, helping clinicians identify the underlying pathology so appropriate strategies for treatment be applied, with the ultimate aim of improving long-term outlook and quality of life for affected children.
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Affiliation(s)
- Peter M Shires
- Department of Paediatric Neurology, Nottingham Children's Hospital, Queen's Medical Centre, Nottingham, UK
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Thomas RH, Drew CJG, Wood SE, Hammond CL, Chung SK, Rees MI. Ethnicity can predict GLRA1 genotypes in hyperekplexia. J Neurol Neurosurg Psychiatry 2015; 86:341-3. [PMID: 24970905 DOI: 10.1136/jnnp-2014-307903] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES Hyperekplexia is predominantly caused by mutations in the α-1 subunit of the inhibitory glycine receptor (GLRA1). Three quarters of cases show autosomal-recessive inheritance. METHODS We carefully ascertained reports of ethnicity from our hyperekplexia research cohort. These were compared with all published cases of hyperekplexia with an identified genetic cause. Ethnicities were subgrouped as Caucasian, Asian, Arabic, Turkish, Jewish or Afro-American. RESULTS We report the ethnicity of 90 cases: 56 cases from our service augmented by 34 cases from the literature. Homozygous deletions of exons 1 to 7 are predominantly seen in people with Turkish backgrounds (n=16/17, p<0.001). In contrast, the dominant point mutation R271 is seen in people of Asian, Caucasian and African-American heritage (n=19) but not in people with Arab or Turkish ethnicities (p<0.001). CONCLUSIONS Self-declared ethnicity can predict gene-screening outcomes. Cultural practices influence the inheritance patterns and a Caucasian founder is postulated for R271 mutations.
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Affiliation(s)
- R H Thomas
- MRC Centre for Neuropsychiatric Genetics & Genomics, Cardiff University, Cardiff, Cathays, UK Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea, UK Epilepsy Research Centre, Austin Hospital, Heidelberg, Melbourne, Victoria, Australia
| | - C J G Drew
- Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea, UK Institute of Life Science, College of Medicine, Swansea University, Swansea, UK
| | - S E Wood
- Institute of Life Science, College of Medicine, Swansea University, Swansea, UK
| | - C L Hammond
- Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea, UK Genetic Counselling Service, Guy's and St Thomas' NHS Foundation Trust, St Thomas' Hospital, London, UK
| | - S K Chung
- Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea, UK Institute of Life Science, College of Medicine, Swansea University, Swansea, UK
| | - M I Rees
- Wales Epilepsy Research Network (WERN), College of Medicine, Swansea University, Swansea, UK Institute of Life Science, College of Medicine, Swansea University, Swansea, UK
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Wakabayashi K, Mori F, Kakita A, Takahashi H, Utsumi J, Sasaki H. Analysis of microRNA from archived formalin-fixed paraffin-embedded specimens of amyotrophic lateral sclerosis. Acta Neuropathol Commun 2014; 2:173. [PMID: 25497327 PMCID: PMC4279903 DOI: 10.1186/s40478-014-0173-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 12/01/2014] [Indexed: 12/13/2022] Open
Abstract
Background MicroRNAs (miRNAs) are noncoding small RNAs that regulate gene expression. This study investigated whether formalin-fixed paraffin-embedded (FFPE) specimens from postmortem cases of neurodegenerative disorders would be suitable for miRNA profiling. Results Ten FFPE samples from 6 cases of amyotrophic lateral sclerosis (ALS) and 4 neurologically normal controls were selected for miRNA analysis on the basis of the following criteria for RNA quality: (i) a postmortem interval of less than 6 hours, (ii) a formalin fixation time of less than 4 weeks, (iii) an RNA yield per sample of more than 500 ng, and (iv) sufficient quality of the RNA agarose gel image. An overall RNA extraction success rate was 46.2%. For ALS, a total of 364 miRNAs were identified in the motor cortex, 91 being up-regulated and 233 down-regulated. Target genes were predicted using miRNA bioinformatics software, and the data applied to ontology analysis. This indicated that one of the miRNAs up-regulated in ALS (miR-338-3p) had already been identified in leukocytes, serum, cerebrospinal fluid and frozen spinal cord from ALS patients. Conclusion Although analysis was possible for just under half of the specimens examined, we were able to show that informative miRNA data can be derived from archived FFPE samples from postmortem cases of neurodegenerative disorders. Electronic supplementary material The online version of this article (doi:10.1186/s40478-014-0173-z) contains supplementary material, which is available to authorized users.
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Arribas-González E, de Juan-Sanz J, Aragón C, López-Corcuera B. Molecular basis of the dominant negative effect of a glycine transporter 2 mutation associated with hyperekplexia. J Biol Chem 2014; 290:2150-65. [PMID: 25480793 DOI: 10.1074/jbc.m114.587055] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperekplexia or startle disease is a rare clinical syndrome characterized by an exaggerated startle in response to trivial tactile or acoustic stimuli. This neurological disorder can have serious consequences in neonates, provoking brain damage and/or sudden death due to apnea episodes and cardiorespiratory failure. Hyperekplexia is caused by defective inhibitory glycinergic neurotransmission. Mutations in the human SLC6A5 gene encoding the neuronal GlyT2 glycine transporter are responsible for the presynaptic form of the disease. GlyT2 mediates synaptic glycine recycling, which constitutes the main source of releasable transmitter at glycinergic synapses. Although the majority of GlyT2 mutations detected so far are recessive, a dominant negative mutant that affects GlyT2 trafficking does exist. In this study, we explore the properties and structural alterations of the S512R mutation in GlyT2. We analyze its dominant negative effect that retains wild-type GlyT2 in the endoplasmic reticulum (ER), preventing surface expression. We show that the presence of an arginine rather than serine 512 provoked transporter misfolding, enhanced association to the ER-chaperone calnexin, altered association with the coat-protein complex II component Sec24D, and thereby impeded ER exit. The S512R mutant formed oligomers with wild-type GlyT2 causing its retention in the ER. Overexpression of calnexin rescued wild-type GlyT2 from the dominant negative effect of the mutant, increasing the amount of transporter that reached the plasma membrane and dampening the interaction between the wild-type and mutant GlyT2. The ability of chemical chaperones to overcome the dominant negative effect of the disease mutation on the wild-type transporter was demonstrated in heterologous cells and primary neurons.
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Affiliation(s)
- Esther Arribas-González
- From the Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid 28049, Spain, the IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain
| | - Jaime de Juan-Sanz
- From the Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid 28049, Spain, the IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain, and
| | - Carmen Aragón
- From the Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid 28049, Spain, the IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain, and
| | - Beatriz López-Corcuera
- From the Departamento de Biología Molecular and Centro de Biología Molecular "Severo Ochoa," Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Madrid 28049, Spain, the IdiPAZ-Hospital Universitario La Paz, Universidad Autónoma de Madrid, Madrid 28046, Spain the Centro de Investigación Biomédica en Red de Enfermedades Raras, Instituto de Salud Carlos III, Madrid 28029, Spain, and
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de Juan-Sanz J, Núñez E, Zafra F, Berrocal M, Corbacho I, Ibáñez I, Arribas-González E, Marcos D, López-Corcuera B, Mata AM, Aragón C. Presynaptic control of glycine transporter 2 (GlyT2) by physical and functional association with plasma membrane Ca2+-ATPase (PMCA) and Na+-Ca2+ exchanger (NCX). J Biol Chem 2014; 289:34308-24. [PMID: 25315779 DOI: 10.1074/jbc.m114.586966] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fast inhibitory glycinergic transmission occurs in spinal cord, brainstem, and retina to modulate the processing of motor and sensory information. After synaptic vesicle fusion, glycine is recovered back to the presynaptic terminal by the neuronal glycine transporter 2 (GlyT2) to maintain quantal glycine content in synaptic vesicles. The loss of presynaptic GlyT2 drastically impairs the refilling of glycinergic synaptic vesicles and severely disrupts neurotransmission. Indeed, mutations in the gene encoding GlyT2 are the main presynaptic cause of hyperekplexia in humans. Here, we show a novel endogenous regulatory mechanism that can modulate GlyT2 activity based on a compartmentalized interaction between GlyT2, neuronal plasma membrane Ca(2+)-ATPase (PMCA) isoforms 2 and 3, and Na(+)/Ca(2+)-exchanger 1 (NCX1). This GlyT2·PMCA2,3·NCX1 complex is found in lipid raft subdomains where GlyT2 has been previously found to be fully active. We show that endogenous PMCA and NCX activities are necessary for GlyT2 activity and that this modulation depends on lipid raft integrity. Besides, we propose a model in which GlyT2·PMCA2-3·NCX complex would help Na(+)/K(+)-ATPase in controlling local Na(+) increases derived from GlyT2 activity after neurotransmitter release.
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Affiliation(s)
- Jaime de Juan-Sanz
- From the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065
| | - Enrique Núñez
- the Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049-Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, 46009-Valencia, Spain, the IdiPAZ-Hospital, Universitario La Paz, 28046-Madrid, Spain, and
| | - Francisco Zafra
- the Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049-Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, 46009-Valencia, Spain, the IdiPAZ-Hospital, Universitario La Paz, 28046-Madrid, Spain, and
| | - María Berrocal
- the Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006-Badajoz, Spain
| | - Isaac Corbacho
- the Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006-Badajoz, Spain
| | - Ignacio Ibáñez
- the Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049-Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, 46009-Valencia, Spain, the IdiPAZ-Hospital, Universitario La Paz, 28046-Madrid, Spain, and
| | - Esther Arribas-González
- the Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049-Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, 46009-Valencia, Spain, the IdiPAZ-Hospital, Universitario La Paz, 28046-Madrid, Spain, and
| | - Daniel Marcos
- the Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006-Badajoz, Spain
| | - Beatriz López-Corcuera
- the Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049-Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, 46009-Valencia, Spain, the IdiPAZ-Hospital, Universitario La Paz, 28046-Madrid, Spain, and
| | - Ana M Mata
- the Departamento de Bioquímica y Biología Molecular y Genética, Facultad de Ciencias, Universidad de Extremadura, 06006-Badajoz, Spain
| | - Carmen Aragón
- the Centro de Biología Molecular "Severo Ochoa," Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049-Madrid, Spain, the Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, 46009-Valencia, Spain, the IdiPAZ-Hospital, Universitario La Paz, 28046-Madrid, Spain, and
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50
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Jiménez E, Núñez E, Ibáñez I, Zafra F, Aragón C, Giménez C. Glycine transporters GlyT1 and GlyT2 are differentially modulated by glycogen synthase kinase 3β. Neuropharmacology 2014; 89:245-54. [PMID: 25301276 DOI: 10.1016/j.neuropharm.2014.09.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 09/08/2014] [Accepted: 09/16/2014] [Indexed: 11/16/2022]
Abstract
Inhibitory glycinergic neurotransmission is terminated by the specific glycine transporters GlyT1 and GlyT2 which actively reuptake glycine from the synaptic cleft. GlyT1 is associated with both glycinergic and glutamatergic pathways, and is the main regulator of the glycine levels in the synapses. GlyT2 is the main supplier of glycine for vesicle refilling, a process that is vital to preserve the quantal glycine content in synaptic vesicles. Therefore, to control glycinergic neurotransmission efficiently, GlyT1 and GlyT2 activity must be regulated by diverse neuronal and glial signaling pathways. In this work, we have investigated the possible functional modulation of GlyT1 and GlyT2 by glycogen synthase kinase 3 (GSK3β). This kinase is involved in mood stabilization, neurodegeneration and plasticity at excitatory and inhibitory synapses. The co-expression of GSK3β with GlyT1 or GlyT2 in COS-7 cells and Xenopus laevis oocytes, leads to inhibition and stimulation of GlyT1 and GlyT2 activities, respectively, with a decrease of GlyT1, and an increase in GlyT2 levels at the plasma membrane. The specificity of these changes is supported by the antagonism exerted by a catalytically inactive form of the kinase and through inhibitors of GSK3β such as lithium chloride and TDZD-8. GSK3β also increases the incorporation of 32Pi into GlyT1 and decreases that of GlyT2. The pharmacological inhibition of the endogenous GSK3β in neuron cultures of brainstem and spinal cord leads to an opposite modulation of GlyT1 and GlyT2.Our results suggest that GSK3β is important for stabilizing and/or controlling the expression of functional GlyTs on the neural cell surface.
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Affiliation(s)
- Esperanza Jiménez
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Enrique Núñez
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Ignacio Ibáñez
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Carmen Aragón
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras, ISCIII, Madrid, Spain; IdiPAZ-Hospital Universitario La Paz, Madrid, Spain.
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