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Xiao Y, Zhang H, Li Z, Huang T, Akihiro T, Xu J, Xu H, Lin F. An amino acid transporter-like protein (OsATL15) facilitates the systematic distribution of thiamethoxam in rice for controlling the brown planthopper. PLANT BIOTECHNOLOGY JOURNAL 2022; 20:1888-1901. [PMID: 35678495 PMCID: PMC9491460 DOI: 10.1111/pbi.13869] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 05/30/2022] [Accepted: 06/02/2022] [Indexed: 06/15/2023]
Abstract
Characterization and genetic engineering of plant transporters involved in the pesticide uptake and translocation facilitate pesticide relocation to the tissue where the pests feed, thus improving the bioavailability of the agrichemicals. We aimed to identify thiamethoxam (THX) transporters in rice and modify their expression for better brown planthopper (BPH) control with less pesticide application. A yeast library expressing 1385 rice transporters was screened, leading to the identification of an amino acid transporter-like (ATL) gene, namely OsATL15, which facilitates THX uptake in both yeast cells and rice seedlings. In contrast to a decrease in THX content in osatl15 knockout mutants, ectopic expression of OsATL15 under the control of the CaMV 35S promoter or a vascular-bundle-specific promoter gdcsPpro significantly increased THX accumulation in rice plants, thus further enhancing the THX efficacy against BPH. OsATL15 was localized in rice cell membrane and abundant in the root transverse sections, vascular bundles of leaf blade, and stem longitudinal sections, but not in hull and brown rice at filling stages. Our study shows that OsATL15 plays an essential role in THX uptake and its systemic distribution in rice. OsATL15 could be valuable in achieving precise pest control by biotechnology approaches.
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Affiliation(s)
- Yuyan Xiao
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources/Key Laboratory of Natural Pesticide and Chemical BiologyMinistry of Education, South China Agricultural UniversityGuangzhouChina
| | - Hanlin Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources/Key Laboratory of Natural Pesticide and Chemical BiologyMinistry of Education, South China Agricultural UniversityGuangzhouChina
| | - Zhiwei Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources/Key Laboratory of Natural Pesticide and Chemical BiologyMinistry of Education, South China Agricultural UniversityGuangzhouChina
| | - Tinghong Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources/Key Laboratory of Natural Pesticide and Chemical BiologyMinistry of Education, South China Agricultural UniversityGuangzhouChina
| | - Takashi Akihiro
- Faculty of Life and Environmental ScienceShimane UniversityShimaneJapan
| | - Jian Xu
- College of Life SciencesSouth China Agricultural UniversityGuangzhouChina
| | - Hanhong Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources/Key Laboratory of Natural Pesticide and Chemical BiologyMinistry of Education, South China Agricultural UniversityGuangzhouChina
| | - Fei Lin
- State Key Laboratory for Conservation and Utilization of Subtropical Agro‐Bioresources/Key Laboratory of Natural Pesticide and Chemical BiologyMinistry of Education, South China Agricultural UniversityGuangzhouChina
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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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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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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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Barrera SP, Castrejon-Tellez V, Trinidad M, Robles-Escajeda E, Vargas-Medrano J, Varela-Ramirez A, Miranda M. PKC-Dependent GlyT1 Ubiquitination Occurs Independent of Phosphorylation: Inespecificity in Lysine Selection for Ubiquitination. PLoS One 2015; 10:e0138897. [PMID: 26418248 PMCID: PMC4587969 DOI: 10.1371/journal.pone.0138897] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/06/2015] [Indexed: 01/08/2023] Open
Abstract
Neurotransmitter transporter ubiquitination is emerging as the main mechanism for endocytosis and sorting of cargo into lysosomes. In this study, we demonstrate PKC-dependent ubiquitination of three different isoforms of the glycine transporter 1 (GlyT1). Incubation of cells expressing transporter with the PKC activator phorbol ester induced a dramatic, time-dependent increase in GlyT1 ubiquitination, followed by accumulation of GlyT1 in EEA1 positive early endosomes. This occurred via a mechanism that was abolished by inhibition of PKC. GlyT1 endocytosis was confirmed in both retinal sections and primary cultures of mouse amacrine neurons. Replacement of only all lysines in the N-and C-termini to arginines prevented ubiquitination and endocytosis, displaying redundancy in the mechanism of ubiquitination. Interestingly, a 40–50% reduction in glycine uptake was detected in phorbol-ester stimulated cells expressing the WT-GlyT1, whereas no significant change was for the mutant protein, demonstrating that endocytosis participates in the reduction of uptake. Consistent with previous findings for the dopamine transporter DAT, ubiquitination of GlyT1 tails functions as sorting signal to deliver transporter into the lysosome and removal of ubiquitination sites dramatically attenuated the rate of GlyT1 degradation. Finally, we showed for the first time that PKC-dependent GlyT1 phosphorylation was not affected by removal of ubiquitination sites, suggesting separate PKC-dependent signaling events for these posttranslational modifications.
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Affiliation(s)
- Susana P. Barrera
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Vicente Castrejon-Tellez
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Margarita Trinidad
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Elisa Robles-Escajeda
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Javier Vargas-Medrano
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Armando Varela-Ramirez
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
| | - Manuel Miranda
- Department of Biological Sciences and Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, 79968, United States of America
- * E-mail:
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de Juan-Sanz J, Núñez E, Villarejo-López L, Pérez-Hernández D, Rodriguez-Fraticelli AE, López-Corcuera B, Vázquez J, Aragón C. Na+/K+-ATPase is a new interacting partner for the neuronal glycine transporter GlyT2 that downregulates its expression in vitro and in vivo. J Neurosci 2013; 33:14269-81. [PMID: 23986260 PMCID: PMC6618510 DOI: 10.1523/jneurosci.1532-13.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 07/09/2013] [Accepted: 07/18/2013] [Indexed: 01/16/2023] Open
Abstract
The neuronal glycine transporter GlyT2 plays a fundamental role in the glycinergic neurotransmission by recycling the neurotransmitter to the presynaptic terminal. GlyT2 is the main supplier of glycine for vesicle refilling, a process that is absolutely necessary to preserve quantal glycine content in synaptic vesicles. Alterations in GlyT2 activity modify glycinergic neurotransmission and may underlie several neuromuscular disorders, such as hyperekplexia, myoclonus, dystonia, and epilepsy. Indeed, mutations in the gene encoding GlyT2 are the main presynaptic cause of hyperekplexia in humans and produce congenital muscular dystonia type 2 (CMD2) in Belgian Blue cattle. GlyT2 function is strictly coupled to the sodium electrochemical gradient actively generated by the Na+/K+-ATPase (NKA). GlyT2 cotransports 3Na+/Cl-/glycine generating large rises of Na+ inside the presynaptic terminal that must be efficiently reduced by the NKA to preserve Na+ homeostasis. In this work, we have used high-throughput mass spectrometry to identify proteins interacting with GlyT2 in the CNS. NKA was detected as a putative candidate and through reciprocal coimmunoprecipitations and immunocytochemistry analyses the association between GlyT2 and NKA was confirmed. NKA mainly interacts with the raft-associated active pool of GlyT2, and low and high levels of the specific NKA ligand ouabain modulate the endocytosis and total expression of GlyT2 in neurons. The ouabain-mediated downregulation of GlyT2 also occurs in vivo in two different systems: zebrafish embryos and adult rats, indicating that this NKA-mediated regulatory mechanism is evolutionarily conserved and may play a relevant role in the physiological control of inhibitory glycinergic neurotransmission.
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Affiliation(s)
- Jaime de Juan-Sanz
- 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, 46010 Valencia, Spain
- IdiPAZ-Hospital Universitario La Paz, 28046 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, 46010 Valencia, Spain
- IdiPAZ-Hospital Universitario La Paz, 28046 Madrid, Spain
| | - Lucía Villarejo-López
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
| | | | - Alejo E. Rodriguez-Fraticelli
- Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain
| | - Beatriz López-Corcuera
- 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, 46010 Valencia, Spain
- IdiPAZ-Hospital Universitario La Paz, 28046 Madrid, Spain
| | - Jesús Vázquez
- Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain, and
| | - 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, 46010 Valencia, Spain
- IdiPAZ-Hospital Universitario La Paz, 28046 Madrid, Spain
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Kristensen AS, Andersen J, Jørgensen TN, Sørensen L, Eriksen J, Loland CJ, Strømgaard K, Gether U. SLC6 neurotransmitter transporters: structure, function, and regulation. Pharmacol Rev 2011; 63:585-640. [PMID: 21752877 DOI: 10.1124/pr.108.000869] [Citation(s) in RCA: 591] [Impact Index Per Article: 45.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The neurotransmitter transporters (NTTs) belonging to the solute carrier 6 (SLC6) gene family (also referred to as the neurotransmitter-sodium-symporter family or Na(+)/Cl(-)-dependent transporters) comprise a group of nine sodium- and chloride-dependent plasma membrane transporters for the monoamine neurotransmitters serotonin (5-hydroxytryptamine), dopamine, and norepinephrine, and the amino acid neurotransmitters GABA and glycine. The SLC6 NTTs are widely expressed in the mammalian brain and play an essential role in regulating neurotransmitter signaling and homeostasis by mediating uptake of released neurotransmitters from the extracellular space into neurons and glial cells. The transporters are targets for a wide range of therapeutic drugs used in treatment of psychiatric diseases, including major depression, anxiety disorders, attention deficit hyperactivity disorder and epilepsy. Furthermore, psychostimulants such as cocaine and amphetamines have the SLC6 NTTs as primary targets. Beginning with the determination of a high-resolution structure of a prokaryotic homolog of the mammalian SLC6 transporters in 2005, the understanding of the molecular structure, function, and pharmacology of these proteins has advanced rapidly. Furthermore, intensive efforts have been directed toward understanding the molecular and cellular mechanisms involved in regulation of the activity of this important class of transporters, leading to new methodological developments and important insights. This review provides an update of these advances and their implications for the current understanding of the SLC6 NTTs.
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Affiliation(s)
- Anders S Kristensen
- Department of Medicinal Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Copenhagen, Denmark.
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Davies JS, Chung SK, Thomas RH, Robinson A, Hammond CL, Mullins JGL, Carta E, Pearce BR, Harvey K, Harvey RJ, Rees MI. The glycinergic system in human startle disease: a genetic screening approach. Front Mol Neurosci 2010; 3:8. [PMID: 20407582 PMCID: PMC2854534 DOI: 10.3389/fnmol.2010.00008] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Accepted: 03/08/2010] [Indexed: 11/17/2022] Open
Abstract
Human startle disease, also known as hyperekplexia (OMIM 149400), is a paroxysmal neurological disorder caused by defects in glycinergic neurotransmission. Hyperekplexia is characterised by an exaggerated startle reflex in response to tactile or acoustic stimuli which first presents as neonatal hypertonia, followed in some with episodes of life-threatening infantile apnoea. Genetic screening studies have demonstrated that hyperekplexia is genetically heterogeneous with several missense and nonsense mutations in the postsynaptic glycine receptor (GlyR) alpha1 subunit gene (GLRA1) as the primary cause. More recently, missense, nonsense and frameshift mutations have also been identified in the glycine transporter GlyT2 gene, SLC6A5, demonstrating a presynaptic component to this disease. Further mutations, albeit rare, have been identified in the genes encoding the GlyR beta subunit (GLRB), collybistin (ARHGEF9) and gephyrin (GPHN) - all of which are postsynaptic proteins involved in orchestrating glycinergic neurotransmission. In this review, we describe the clinical ascertainment aspects, phenotypic considerations and the downstream molecular genetic tools utilised to analyse both presynaptic and postsynaptic components of this heterogeneous human neurological disorder. Moreover, we will describe how the ancient startle response is the preserve of glycinergic neurotransmission and how animal models and human hyperekplexia patients have provided synergistic evidence that implicates this inhibitory system in the control of startle reflexes.
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Affiliation(s)
- Jeff S Davies
- Institute of Life Science, School of Medicine, Swansea University Singleton Park, Swansea, UK
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Pennington K, Beasley CL, Dicker P, Fagan A, English J, Pariante CM, Wait R, Dunn MJ, Cotter DR. Prominent synaptic and metabolic abnormalities revealed by proteomic analysis of the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder. Mol Psychiatry 2008; 13:1102-17. [PMID: 17938637 DOI: 10.1038/sj.mp.4002098] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is evidence for both similarity and distinction in the presentation and molecular characterization of schizophrenia and bipolar disorder. In this study, we characterized protein abnormalities in the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder using two-dimensional gel electrophoresis. Tissue samples were obtained from 35 individuals with schizophrenia, 35 with bipolar disorder and 35 controls. Eleven protein spots in schizophrenia and 48 in bipolar disorder were found to be differentially expressed (P<0.01) in comparison to controls, with 7 additional spots found to be altered in both diseases. Using mass spectrometry, 15 schizophrenia-associated proteins and 51 bipolar disorder-associated proteins were identified. The functional groups most affected included synaptic proteins (7 of the 15) in schizophrenia and metabolic or mitochondrial-associated proteins (25 of the 51) in bipolar disorder. Six of seven synaptic-associated proteins abnormally expressed in bipolar disorder were isoforms of the septin family, while two septin protein spots were also significantly differentially expressed in schizophrenia. This finding represented the largest number of abnormalities from one protein family. All septin protein spots were upregulated in disease in comparison to controls. This study provides further characterization of the synaptic pathology present in schizophrenia and of the metabolic dysfunction observed in bipolar disorder. In addition, our study has provided strong evidence implicating the septin protein family of proteins in psychiatric disorders for the first time.
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Affiliation(s)
- K Pennington
- Department of Psychiatry, Royal College of Surgeons in Ireland, Dublin, Ireland
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11
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The genetics of hyperekplexia: more than startle! Trends Genet 2008; 24:439-47. [DOI: 10.1016/j.tig.2008.06.005] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 06/04/2008] [Accepted: 06/04/2008] [Indexed: 11/20/2022]
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Harvey RJ, Carta E, Pearce BR, Chung SK, Supplisson S, Rees MI, Harvey K. A critical role for glycine transporters in hyperexcitability disorders. Front Mol Neurosci 2008; 1:1. [PMID: 18946534 PMCID: PMC2526004 DOI: 10.3389/neuro.02.001.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 01/30/2008] [Indexed: 11/13/2022] Open
Abstract
Defects in mammalian glycinergic neurotransmission result in a complex motor disorder characterized by neonatal hypertonia and an exaggerated startle reflex, known as hyperekplexia (OMIM 149400). This affects newborn children and is characterized by noise or touch-induced seizures that result in muscle stiffness and breath-holding episodes. Although rare, this disorder can have serious consequences, including brain damage and/or sudden infant death. The primary cause of hyperekplexia is missense and non-sense mutations in the glycine receptor (GlyR) α1 subunit gene (GLRA1) on chromosome 5q33.1, although we have also discovered rare mutations in the genes encoding the GlyR β subunit (GLRB) and the GlyR clustering proteins gephyrin (GPNH) and collybistin (ARHGEF9). Recent studies of the Na+/Cl−-dependent glycine transporters GlyT1 and GlyT2 using mouse knockout models and human genetics have revealed that mutations in GlyT2 are a second major cause of hyperekplexia, while the phenotype of the GlyT1 knockout mouse resembles a devastating neurological disorder known as glycine encephalopathy (OMIM 605899). These findings highlight the importance of these transporters in regulating the levels of synaptic glycine.
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Affiliation(s)
- Robert J Harvey
- Department of Pharmacology, The School of Pharmacy London, UK
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Armsen W, Himmel B, Betz H, Eulenburg V. The C-terminal PDZ-ligand motif of the neuronal glycine transporter GlyT2 is required for efficient synaptic localization. Mol Cell Neurosci 2007; 36:369-80. [PMID: 17851090 DOI: 10.1016/j.mcn.2007.07.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2007] [Revised: 07/13/2007] [Accepted: 07/24/2007] [Indexed: 11/28/2022] Open
Abstract
The neuronal glycine transporter 2 (GlyT2) belongs to the large SLC6 family of Na+/Cl--dependent neurotransmitter transporters. At its extreme C-terminus, GlyT2 carries a type III PDZ domain binding motif (PDZ-ligand motif), which interacts with the PDZ domain protein syntenin-1. Here, we investigated the physiological role of the GlyT2 PDZ-ligand motif by a loss-of-function approach. Inactivation of the PDZ-ligand motif did not impair the localization, glycosylation and transport function of recombinant GlyT2 expressed in HEK293T cells. However, in transfected hippocampal neurons, the synaptic localization of GlyT2 was significantly reduced upon PDZ-ligand motif inactivation. Co-localization of GlyT2 with marker proteins of excitatory and inhibitory synapses was decreased by down to 50% upon PDZ-ligand motif deletion as compared to the wild-type protein. These data indicate that the C-terminal PDZ-ligand motif of GlyT2 plays an important role in transporter trafficking to and/or stabilization at synaptic sites.
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Affiliation(s)
- Wencke Armsen
- Department of Neurochemistry, Max-Planck Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt am Main, Germany
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Mackenzie B, Takanaga H, Hubert N, Rolfs A, Hediger M. Functional properties of multiple isoforms of human divalent metal-ion transporter 1 (DMT1). Biochem J 2007; 403:59-69. [PMID: 17109629 PMCID: PMC1828886 DOI: 10.1042/bj20061290] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
DMT1 (divalent metal-ion transporter 1) is a widely expressed metal-ion transporter that is vital for intestinal iron absorption and iron utilization by most cell types throughout the body, including erythroid precursors. Mutations in DMT1 cause severe microcytic anaemia in animal models. Four DMT1 isoforms that differ in their N- and C-termini arise from mRNA transcripts that vary both at their 5'-ends (starting in exon 1A or exon 1B) and at their 3'-ends giving rise to mRNAs containing (+) or lacking (-) the 3'-IRE (iron-responsive element) and resulting in altered C-terminal coding sequences. To determine whether these variations result in functional differences between isoforms, we explored the functional properties of each isoform using the voltage clamp and radiotracer assays in cRNA-injected Xenopus oocytes. 1A/IRE+-DMT1 mediated Fe2+-evoked currents that were saturable (K(0.5)(Fe) approximately 1-2 microM), temperature-dependent (Q10 approximately 2), H+-dependent (K(0.5)(H) approximately 1 muM) and voltage-dependent. 1A/IRE+-DMT1 exhibited the provisional substrate profile (ranked on currents) Cd2+, Co2+, Fe2+, Mn2+>Ni2+, V3+>>Pb2+. Zn2+ also evoked large currents; however, the zinc-evoked current was accounted for by H+ and Cl- conductances and was not associated with significant Zn2+ transport. 1B/IRE+-DMT1 exhibited the same substrate profile, Fe2+ affinity and dependence on the H+ electrochemical gradient. Each isoform mediated 55Fe2+ uptake and Fe2+-evoked currents at low extracellular pH. Whereas iron transport activity varied markedly between the four isoforms, the activity for each correlated with the density of anti-DMT1 immunostaining in the plasma membrane, and the turnover rate of the Fe2+ transport cycle did not differ between isoforms. Therefore all four isoforms of human DMT1 function as metal-ion transporters of equivalent efficiency. Our results reveal that the N- and C-terminal sequence variations among the DMT1 isoforms do not alter DMT1 functional properties. We therefore propose that these variations serve as tissue-specific signals or cues to direct DMT1 to the appropriate subcellular compartments (e.g. in erythroid cells) or the plasma membrane (e.g. in intestine).
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Affiliation(s)
- Bryan Mackenzie
- *Membrane Biology Program and Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, U.S.A
- †Department of Molecular and Cellular Physiology, University of Cincinnati College of Medicine, PO Box 670576, Cincinnati, OH 45267-0576, U.S.A
| | - Hitomi Takanaga
- *Membrane Biology Program and Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, U.S.A
| | - Nadia Hubert
- ‡European Molecular Biology Laboratory, Gene Expression Programme, Meyerhofstrasse 1, D-69117 Heidelberg, Federal Republic of Germany
| | - Andreas Rolfs
- *Membrane Biology Program and Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, U.S.A
| | - Matthias A. Hediger
- *Membrane Biology Program and Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, U.S.A
- Present address and address for correspondence: Institute of Biochemistry and Molecular Medicine, University of Berne, Bühlstrasse 28, CH-3012 Berne, Switzerland (email )
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15
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Rees MI, Harvey K, Pearce BR, Chung SK, Duguid IC, Thomas P, Beatty S, Graham GE, Armstrong L, Shiang R, Abbott KJ, Zuberi SM, Stephenson JBP, Owen MJ, Tijssen MAJ, van den Maagdenberg AMJM, Smart TG, Supplisson S, Harvey RJ. Mutations in the gene encoding GlyT2 (SLC6A5) define a presynaptic component of human startle disease. Nat Genet 2006; 38:801-6. [PMID: 16751771 PMCID: PMC3204411 DOI: 10.1038/ng1814] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Accepted: 05/05/2006] [Indexed: 11/08/2022]
Abstract
Hyperekplexia is a human neurological disorder characterized by an excessive startle response and is typically caused by missense and nonsense mutations in the gene encoding the inhibitory glycine receptor (GlyR) alpha1 subunit (GLRA1). Genetic heterogeneity has been confirmed in rare sporadic cases, with mutations affecting other postsynaptic glycinergic proteins including the GlyR beta subunit (GLRB), gephyrin (GPHN) and RhoGEF collybistin (ARHGEF9). However, many individuals diagnosed with sporadic hyperekplexia do not carry mutations in these genes. Here we show that missense, nonsense and frameshift mutations in SLC6A5 (ref. 8), encoding the presynaptic glycine transporter 2 (GlyT2), also cause hyperekplexia. Individuals with mutations in SLC6A5 present with hypertonia, an exaggerated startle response to tactile or acoustic stimuli, and life-threatening neonatal apnea episodes. SLC6A5 mutations result in defective subcellular GlyT2 localization, decreased glycine uptake or both, with selected mutations affecting predicted glycine and Na+ binding sites.
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Affiliation(s)
- Mark I Rees
- School of Medicine, University of Wales Swansea, Singleton Park, West Glamorgan SA2 8PP, UK.
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16
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Betz H, Gomeza J, Armsen W, Scholze P, Eulenburg V. Glycine transporters: essential regulators of synaptic transmission. Biochem Soc Trans 2006; 34:55-8. [PMID: 16417482 DOI: 10.1042/bst0340055] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glycine is a major inhibitory neurotransmitter in the mammalian CNS (central nervous system). Glycinergic neurotransmission is terminated by the uptake of glycine into glycinergic nerve terminals and neighbouring glial cells. This uptake process is mediated by specific Na+/Cl−-dependent GlyTs (glycine transporters), GlyT1 and GlyT2. GlyT1, in addition, is thought to regulate the concentration of glycine at excitatory synapses containing NMDARs (N-methyl-D-aspartate receptors), which require glycine as a co-agonist. We have analysed the physiological roles and regulation of GlyT1 and GlyT2 by generating transporter-deficient mice and searching for interacting proteins. Our genetic results indicate that at glycinergic synapses, the glial transporter GlyT1 catalyses the removal of glycine from the synaptic cleft, whereas GlyT2 is required for the re-uptake of glycine into nerve terminals, thereby allowing for neurotransmitter reloading of synaptic vesicles. Both GlyT1 and GlyT2 are essential for CNS function, as revealed by the lethal phenotypes of the respective knockout mice. Mice expressing only a single GlyT1 allele are phenotypically normal but may have enhanced NMDAR function. GlyT2 is highly enriched at glycinergic nerve terminals, and Ca2+-triggered exocytosis and internalization are thought to regulate GlyT2 numbers in the pre-synaptic plasma membrane. We have identified different interacting proteins that may play a role in GlyT2 trafficking and/or pre-synaptic localization.
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Affiliation(s)
- H Betz
- Department of Neurochemistry, Max-Planck-Institute for Brain Research, Deutschordenstrasse 46, 60528 Frankfurt, Germany.
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17
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Abstract
Glycine has multiple neurotransmitter functions in the central nervous system (CNS). In the spinal cord and brainstem of vertebrates, it serves as a major inhibitory neurotransmitter. In addition, it participates in excitatory neurotransmission by modulating the activity of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. The extracellular concentrations of glycine are regulated by Na+/Cl(-)-dependent glycine transporters (GlyTs), which are expressed in neurons and adjacent glial cells. Considerable progress has been made recently towards elucidating the in vivo roles of GlyTs in the CNS. The generation and analysis of animals carrying targeted disruptions of GlyT genes (GlyT knockout mice) have allowed investigators to examine the different contributions of individual GlyT subtypes to synaptic transmission. In addition, they have provided animal models for two hereditary human diseases, glycine encephalopathy and hyperekplexia. Selective GlyT inhibitors have been shown to modulate neurotransmission and might constitute promising therapeutic tools for the treatment of psychiatric and neurological disorders such as schizophrenia and pain. Therefore, pharmacological and genetic studies indicate that GlyTs are key regulators of both glycinergic inhibitory and glutamatergic excitatory neurotransmission. This chapter describes our present understanding of the functions of GlyTs and their involvement in the fine-tuning of neuronal communication.
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Affiliation(s)
- J Gomeza
- Department of Pharmacology, The Panum Institute, University of Copenhagen, Blegdamsvej 3, 2200 Copenhagen, Denmark.
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