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Zheng M, Ye H, Yang X, Shen L, Dang X, Liu X, Gong Y, Wu Q, Wang L, Ge X, Fang X, Hou B, Zhang P, Tang R, Zheng K, Huang XF, Yu Y. Probiotic Clostridium butyricum ameliorates cognitive impairment in obesity via the microbiota-gut-brain axis. Brain Behav Immun 2024; 115:565-587. [PMID: 37981012 DOI: 10.1016/j.bbi.2023.11.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 11/06/2023] [Accepted: 11/13/2023] [Indexed: 11/21/2023] Open
Abstract
Obesity is a risk factor for cognitive dysfunction and neurodegenerative disease, including Alzheimer's disease (AD). The gut microbiota-brain axis is altered in obesity and linked to cognitive impairment and neurodegenerative disorders. Here, we targeted obesity-induced cognitive impairment by testing the impact of the probiotic Clostridium butyricum, which has previously shown beneficial effects on gut homeostasis and brain function. Firstly, we characterized and analyzed the gut microbial profiles of participants with obesity and the correlation between gut microbiota and cognitive scores. Then, using an obese mouse model induced by a Western-style diet (high-fat and fiber-deficient diet), the effects of Clostridium butyricum on the microbiota-gut-brain axis and hippocampal cognitive function were evaluated. Finally, fecal microbiota transplantation was performed to assess the functional link between Clostridium butyricum remodeling gut microbiota and hippocampal synaptic protein and cognitive behaviors. Our results showed that participants with obesity had gut microbiota dysbiosis characterized by an increase in phylum Proteobacteria and a decrease in Clostridium butyricum, which were closely associated with cognitive decline. In diet-induced obese mice, oral Clostridium butyricum supplementation significantly alleviated cognitive impairment, attenuated the deficit of hippocampal neurite outgrowth and synaptic ultrastructure, improved hippocampal transcriptome related to synapses and dendrites; a comparison of the effects of Clostridium butyricum in mice against human AD datasets revealed that many of the genes changes in AD were reversed by Clostridium butyricum; concurrently, Clostridium butyricum also prevented gut microbiota dysbiosis, colonic barrier impairment and inflammation, and attenuated endotoxemia. Importantly, fecal microbiota transplantation from donor-obese mice with Clostridium butyricum supplementation facilitated cognitive variables and colonic integrity compared with from donor obese mice, highlighting that Clostridium butyricum's impact on cognitive function is largely due to its ability to remodel gut microbiota. Our findings provide the first insights into the neuroprotective effects of Clostridium butyricum on obesity-associated cognitive impairments and neurodegeneration via the gut microbiota-gut-brain axis.
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Affiliation(s)
- Mingxuan Zheng
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Huaiyu Ye
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xiaoying Yang
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Lijun Shen
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xuemei Dang
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xiaoli Liu
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Yuying Gong
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Qingyuan Wu
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Li Wang
- Affiliated Hospital of Liaoning University of Traditional Chinese Medicine, Shenyang 110033, China
| | - Xing Ge
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xiaoli Fang
- Department of Neurology, Affiliated Hospital of Xuzhou Medical University, Jiangsu 221004, China
| | - Benchi Hou
- Affiliated Hospital of Liaoning University of Traditional Chinese Medicine, Shenyang 110033, China
| | - Peng Zhang
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Renxian Tang
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Kuiyang Zheng
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China; National Experimental Demonstration Center for Basic Medicine Education, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China
| | - Xu-Feng Huang
- Illawarra Health and Medical Research Institute (IHMRI) and School of Medicine, University of Wollongong, NSW 2522, Australia
| | - Yinghua Yu
- Jiangsu Key Laboratory of Immunity and Metabolism, Jiangsu International Laboratory of Immunity and Metabolism, Department of Pathogen Biology and Immunology, Xuzhou Medical University, Xuzhou, Jiangsu 221004, China.
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Hameed MQ, Hui B, Lin R, MacMullin PC, Pascual‐Leone A, Vermudez SAD, Rotenberg A. Depressed glutamate transporter 1 expression in a mouse model of Dravet syndrome. Ann Clin Transl Neurol 2023; 10:1695-1699. [PMID: 37452008 PMCID: PMC10502630 DOI: 10.1002/acn3.51851] [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: 01/11/2023] [Revised: 06/06/2023] [Accepted: 06/27/2023] [Indexed: 07/18/2023] Open
Abstract
Dravet syndrome (DS) is a monogenic, often refractory, epilepsy resultant from SCN1A haploinsufficiency in humans. A novel therapeutic target in DS that can be engaged in isolation or as adjunctive therapy is highly desirable. Here, we demonstrate reduced expression of the rodent glutamate transporter type 1 (GLT-1) in a DS mouse model, and in wild type mouse strains where Scn1a haploinsufficiency is most likely to cause epilepsy, indicating that GLT-1 depression may play a role in DS seizures. As GLT-1 can be upregulated by common and safe FDA-approved medications, this strategy may be an attractive, viable, and novel avenue for DS treatment.
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Affiliation(s)
- Mustafa Q. Hameed
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- Department of NeurosurgeryBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Benjamin Hui
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Rui Lin
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Paul C. MacMullin
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Andres Pascual‐Leone
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Sheryl Anne D. Vermudez
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
| | - Alexander Rotenberg
- Neuromodulation Program, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
- FM Kirby Neurobiology Center, Department of NeurologyBoston Children's Hospital, Harvard Medical SchoolBostonMassachusettsUSA
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Suslova M, Kortzak D, Machtens JP, Kovermann P, Fahlke C. Apo state pore opening as functional basis of increased EAAT anion channel activity in episodic ataxia 6. Front Physiol 2023; 14:1147216. [PMID: 37538371 PMCID: PMC10394623 DOI: 10.3389/fphys.2023.1147216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 07/07/2023] [Indexed: 08/05/2023] Open
Abstract
SLC1A2 and SLC1A3 encode the glial glutamate transporters EAAT2 and EAAT1, which are not only the predominant glutamate uptake carriers in our brain, but also function as anion channels. Two homologous mutations, which predict substitutions of prolines in the center of the fifth transmembrane helix by arginine (P289R EAAT2, P290R EAAT1), have been identified in patients with epileptic encephalopathy (SLC1A2) or with episodic ataxia type 6 (SLC1A3). Both mutations have been shown to impair glutamate uptake and to increase anion conduction. The molecular processes that link the disease-causing mutations to two major alterations of glutamate transporter function remain insufficiently understood. The mutated proline is conserved in every EAAT. Since the pathogenic changes mainly affect the anion channel function, we here study the functional consequences of the homologous P312R mutation in the neuronal glutamate transporter EAAT4, a low capacity glutamate transporter with predominant anion channel function. To assess the impact of charge and structure of the inserted amino acid for the observed functional changes, we generated and functionally evaluated not only P312R, but also substitutions of P312 with all other amino acids. However, only exchange of proline by arginine, lysine, histidine and asparagine were functionally tolerated. We compared WT, P312R and P312N EAAT4 using a combination of cellular electrophysiology, fast substrate application and kinetic modelling. We found that WT and mutant EAAT4 anion currents can be described with a 11-state model of the transport cycle, in which several states are connected to branching anion channel states to account for the EAAT anion channel function. Substitutions of P312 modify various transitions describing substrate binding/unbinding, translocation or anion channel opening. Most importantly, P312R generates a new anion conducting state that is accessible in the outward facing apo state and that is the main determinant of the increased anion conduction of EAAT transporters carrying this mutation. Our work provides a quantitative description how a naturally occurring mutation changes glutamate uptake and anion currents in two genetic diseases.
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Pujol‐Giménez J, Mirzaa G, Blue EE, Albano G, Miller DE, Allworth A, Bennett JT, Byers PH, Chanprasert S, Chen J, Doherty D, Folta AB, Gillentine MA, Glass I, Hing A, Horike‐Pyne M, Leppig KA, Parhin A, Ranchalis J, Raskind WH, Rosenthal EA, Schwarze U, Sheppeard S, Strohbehn S, Sybert VP, Timms A, Wener M, Bamshad MJ, Hisama FM, Jarvik GP, Dipple KM, Hediger MA, Stergachis AB. Dominant-negative variant in SLC1A4 causes an autosomal dominant epilepsy syndrome. Ann Clin Transl Neurol 2023; 10:1046-1053. [PMID: 37194416 PMCID: PMC10270265 DOI: 10.1002/acn3.51786] [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: 01/30/2023] [Revised: 03/29/2023] [Accepted: 04/15/2023] [Indexed: 05/18/2023] Open
Abstract
SLC1A4 is a trimeric neutral amino acid transporter essential for shuttling L-serine from astrocytes into neurons. Individuals with biallelic variants in SLC1A4 are known to have spastic tetraplegia, thin corpus callosum, and progressive microcephaly (SPATCCM) syndrome, but individuals with heterozygous variants are not thought to have disease. We identify an 8-year-old patient with global developmental delay, spasticity, epilepsy, and microcephaly who has a de novo heterozygous three amino acid duplication in SLC1A4 (L86_M88dup). We demonstrate that L86_M88dup causes a dominant-negative N-glycosylation defect of SLC1A4, which in turn reduces the plasma membrane localization of SLC1A4 and the transport rate of SLC1A4 for L-serine.
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Affiliation(s)
- Jonai Pujol‐Giménez
- Department of Nephrology and HypertensionUniversity Hospital Bern, InselspitalBernSwitzerland
- Department of Biomedical ResearchUniversity of BernBernSwitzerland
| | - Ghayda Mirzaa
- Center for Integrative Brain ResearchSeattle Children's Research InstituteSeattleWashingtonUSA
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Elizabeth E. Blue
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Department of Laboratory Medicine and PathologyUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Giuseppe Albano
- Department of Nephrology and HypertensionUniversity Hospital Bern, InselspitalBernSwitzerland
- Department of Biomedical ResearchUniversity of BernBernSwitzerland
| | - Danny E. Miller
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Aimee Allworth
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - James T. Bennett
- Center for Integrative Brain ResearchSeattle Children's Research InstituteSeattleWashingtonUSA
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- Center for Developmental Biology and Regenerative MedicineSeattle Children's Research InstituteSeattleWashingtonUSA
| | - Peter H. Byers
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Sirisak Chanprasert
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Jingheng Chen
- Department of Laboratory Medicine and PathologyUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Daniel Doherty
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Andrew B. Folta
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | | | - Ian Glass
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Anne Hing
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
| | - Martha Horike‐Pyne
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Kathleen A. Leppig
- Group Health CooperativeKaiser Permanente WashingtonSeattleWashingtonUSA
| | - Azma Parhin
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Jane Ranchalis
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Wendy H. Raskind
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | | | - Ulrike Schwarze
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Sam Sheppeard
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Samuel Strohbehn
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Virginia P. Sybert
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Andrew Timms
- Center for Developmental Biology and Regenerative MedicineSeattle Children's Research InstituteSeattleWashingtonUSA
| | - Mark Wener
- Department of MedicineUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Michael J. Bamshad
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Fuki M. Hisama
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
| | - Gail P. Jarvik
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Genome SciencesUniversity of Washington School of MedicineSeattleWashingtonUSA
| | - Katrina M. Dipple
- Department of PediatricsUniversity of WashingtonSeattleWashingtonUSA
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
| | - Matthias A. Hediger
- Department of Nephrology and HypertensionUniversity Hospital Bern, InselspitalBernSwitzerland
- Department of Biomedical ResearchUniversity of BernBernSwitzerland
| | - Andrew B. Stergachis
- Brotman Baty Institute for Precision MedicineSeattleWashingtonUSA
- University of Washington, Institute of Public Health GeneticsSeattleWashingtonUSA
- Genome SciencesUniversity of Washington School of MedicineSeattleWashingtonUSA
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Alijanpour S, Miryounesi M, Ghafouri-Fard S. The role of excitatory amino acid transporter 2 (EAAT2) in epilepsy and other neurological disorders. Metab Brain Dis 2023; 38:1-16. [PMID: 36173507 DOI: 10.1007/s11011-022-01091-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 09/15/2022] [Indexed: 02/03/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). Excitatory amino acid transporters (EAATs) have important roles in the uptake of glutamate and termination of glutamatergic transmission. Up to now, five EAAT isoforms (EAAT1-5) have been identified in mammals. The main focus of this review is EAAT2. This protein has an important role in the pathoetiology of epilepsy. De novo dominant mutations, as well as inherited recessive mutation in this gene, have been associated with epilepsy. Moreover, dysregulation of this protein is implicated in a range of neurological diseases, namely amyotrophic lateral sclerosis, alzheimer's disease, parkinson's disease, schizophrenia, epilepsy, and autism. In this review, we summarize the role of EAAT2 in epilepsy and other neurological disorders, then provide an overview of the therapeutic modulation of this protein.
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Affiliation(s)
- Sahar Alijanpour
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Miryounesi
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Soudeh Ghafouri-Fard
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Functional investigation of SLC1A2 variants associated with epilepsy. Cell Death Dis 2022; 13:1063. [PMID: 36543780 PMCID: PMC9772344 DOI: 10.1038/s41419-022-05457-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 11/15/2022] [Accepted: 11/18/2022] [Indexed: 12/24/2022]
Abstract
Epilepsy is a common neurological disorder and glutamate excitotoxicity plays a key role in epileptic pathogenesis. Astrocytic glutamate transporter GLT-1 is responsible for preventing excitotoxicity via clearing extracellular accumulated glutamate. Previously, three variants (G82R, L85P, and P289R) in SLC1A2 (encoding GLT-1) have been clinically reported to be associated with epilepsy. However, the functional validation and underlying mechanism of these GLT-1 variants in epilepsy remain undetermined. In this study, we reported that these disease-linked mutants significantly decrease glutamate uptake, cell membrane expression of the glutamate transporter, and glutamate-elicited current. Additionally, we found that these variants may disturbed stromal-interacting molecule 1 (STIM1)/Orai1-mediated store-operated Ca2+ entry (SOCE) machinery in the endoplasmic reticulum (ER), in which GLT-1 may be a new partner of SOCE. Furthermore, knock-in mice with disease-associated variants showed a hyperactive phenotype accompanied by reduced glutamate transporter expression. Therefore, GLT-1 is a promising and reliable therapeutic target for epilepsy interventions.
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Feng Y, Zhang C, Wei Z, Li G, Gan Y, Liu C, Deng Y. Gene variations of glutamate metabolism pathway and epilepsy. ACTA EPILEPTOLOGICA 2022. [DOI: 10.1186/s42494-022-00103-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Abstract
Background
Epilepsy is a paroxysmal disorder of the brain, caused by an imbalance of neuronal excitation and inhibition. Glutamate is the most important excitatory neurotransmitter in the brain and plays an important role in epileptogenesis. Mutations in genes at any step/component of the glutamate metabolic pathway may lead to the development of epilepsy or epileptic encephalopathy.
Methods
Clinical history of 3 epilepsy patients with genetic variations of the glutamate metabolism pathway was collected. Electroencephalogram recording and magnetic resonance imaging were performed in each patient. We also reviewed recent literature for a variety of the genetic variations involved in epilepsy.
Results
Case 1 was a SLC1A2 mutation-carrier diagnosed with developmental and epileptic encephalopathy (DEE) 41, whose seizures decreased after start of the ketogenic diet. Case 2 carried a GRIN2A gene mutation and was seizure-free for three years after taking levetiracetam and vitamin B6. Case 3 was a GRIN2B mutation-carrier diagnosed with DEE 27, who seizures diminished after taking oxcarbazepine.
Conclusions
Preclinical and clinical evidence supports the therapeutic potential of glutamatergic signaling-targeting treatments for epilepsy. More studies are needed to discover novel DEE-related genetic mutations in the glutamate metabolic pathway.
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Gan Y, Wei Z, Liu C, Li G, Feng Y, Deng Y. Solute carrier transporter disease and developmental and epileptic encephalopathy. Front Neurol 2022; 13:1013903. [PMID: 36419532 PMCID: PMC9676364 DOI: 10.3389/fneur.2022.1013903] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 09/07/2022] [Indexed: 09/14/2023] Open
Abstract
The International League Against Epilepsy officially revised its classification in 2017, which amended "epileptic encephalopathy" to "developmental and epileptic encephalopathy". With the development of genetic testing technology, an increasing number of genes that cause developmental and epileptic encephalopathies are being identified. Among these, solute transporter dysfunction is part of the etiology of developmental and epileptic encephalopathies. Solute carrier transporters play an essential physiological function in the human body, and their dysfunction is associated with various human diseases. Therefore, in-depth studies of developmental and epileptic encephalopathies caused by solute carrier transporter dysfunction can help develop new therapeutic modalities to facilitate the treatment of refractory epilepsy and improve patient prognosis. In this article, the concept of transporter protein disorders is first proposed, and nine developmental and epileptic encephalopathies caused by solute carrier transporter dysfunction are described in detail in terms of pathogenesis, clinical manifestations, ancillary tests, and precise treatment to provide ideas for the precise treatment of epilepsy.
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Affiliation(s)
- Yajing Gan
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Zihan Wei
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Chao Liu
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Guoyan Li
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yan Feng
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
| | - Yanchun Deng
- Department of Neurology, Epilepsy Center of Xijing Hospital, Fourth Military Medical University, Xi'an, China
- Xijing Institute of Epilepsy and Encephalopathy, Xi'an, China
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9
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Kovermann P, Kolobkova Y, Franzen A, Fahlke C. Mutations associated with epileptic encephalopathy modify EAAT2 anion channel function. Epilepsia 2021; 63:388-401. [PMID: 34961934 DOI: 10.1111/epi.17154] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/09/2021] [Accepted: 12/09/2021] [Indexed: 11/28/2022]
Abstract
OBJECTIVE Mutations in the gene solute carrier family member 1A2 (SLC1A2) encoding the excitatory amino acid transporter 2 (EAAT2) are associated with severe forms of epileptic encephalopathy. EAAT2 is expressed in glial cells and presynaptic nerve terminals and represents the main l-glutamate uptake carrier in the mammalian brain. It does not only function as a secondary active glutamate transporter, but also as an anion channel. How naturally occurring mutations affect these two transport functions of EAAT2 and how such alterations cause epilepsy is insufficiently understood. METHODS Here we studied the functional consequences of three disease-associated mutations, which predict amino acid exchanges p.Gly82Arg (G82R), p.Leu85Pro (L85P), and p.Pro289Arg (P289R), by heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch-clamp recordings of EAAT2 l-glutamate transport and anion current. RESULTS G82R and L85P exchange amino acid residues contribute to the formation of the EAAT anion pore. They enlarge the pore diameter sufficiently to permit the passage of l-glutamate and thus function as l-glutamate efflux pathways. The mutation P289R decreases l-glutamate uptake, but increases anion currents despite a lower membrane expression. SIGNIFICANCE l-glutamate permeability of the EAAT anion pore is an unexpected functional consequence of naturally occurring single amino acid substitutions. l-glutamate efflux through mutant EAAT2 anion channels will cause glutamate excitotoxicity and neuronal hyperexcitability in affected patients. Antagonists that selectively suppress the EAAT anion channel function could serve as therapeutic agents in the future.
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Affiliation(s)
- Peter Kovermann
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
| | - Yulia Kolobkova
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
| | - Arne Franzen
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
| | - Christoph Fahlke
- Molekular- und Zellphysiologie (IBI-1) Forschungszentrum Jülich, Institute of Biological Information Processing, Jülich, Germany
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Hotz AL, Jamali A, Rieser NN, Niklaus S, Aydin E, Myren‐Svelstad S, Lalla L, Jurisch‐Yaksi N, Yaksi E, Neuhauss SCF. Loss of glutamate transporter eaat2a leads to aberrant neuronal excitability, recurrent epileptic seizures, and basal hypoactivity. Glia 2021; 70:196-214. [PMID: 34716961 PMCID: PMC9297858 DOI: 10.1002/glia.24106] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 10/05/2021] [Accepted: 10/06/2021] [Indexed: 11/13/2022]
Abstract
Astroglial excitatory amino acid transporter 2 (EAAT2, GLT‐1, and SLC1A2) regulates the duration and extent of neuronal excitation by removing glutamate from the synaptic cleft. Hence, an impairment in EAAT2 function could lead to an imbalanced brain network excitability. Here, we investigated the functional alterations of neuronal and astroglial networks associated with the loss of function in the astroglia predominant eaat2a gene in zebrafish. We observed that eaat2a−/− mutant zebrafish larvae display recurrent spontaneous and light‐induced seizures in neurons and astroglia, which coincide with an abrupt increase in extracellular glutamate levels. In stark contrast to this hyperexcitability, basal neuronal and astroglial activity was surprisingly reduced in eaat2a−/− mutant animals, which manifested in decreased overall locomotion. Our results reveal an essential and mechanistic contribution of EAAT2a in balancing brain excitability, and its direct link to epileptic seizures.
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Affiliation(s)
- Adriana L. Hotz
- Department of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
- Life Science Zürich Graduate School ‐ NeuroscienceUniversity of Zurich and ETH ZurichZurichSwitzerland
| | - Ahmed Jamali
- Kavli Institute for Systems Neuroscience and Centre for Neural ComputationFaculty of Medicine and Health Sciences, Norwegian University of Science and TechnologyTrondheimNorway
| | - Nicolas N. Rieser
- Department of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
- Life Science Zürich Graduate School ‐ NeuroscienceUniversity of Zurich and ETH ZurichZurichSwitzerland
| | - Stephanie Niklaus
- Department of Molecular Life SciencesUniversity of ZurichZurichSwitzerland
- Present address:
EraCal TherapeuticsSchlierenSwitzerland
| | - Ecem Aydin
- Kavli Institute for Systems Neuroscience and Centre for Neural ComputationFaculty of Medicine and Health Sciences, Norwegian University of Science and TechnologyTrondheimNorway
| | - Sverre Myren‐Svelstad
- Kavli Institute for Systems Neuroscience and Centre for Neural ComputationFaculty of Medicine and Health Sciences, Norwegian University of Science and TechnologyTrondheimNorway
- Department of Neurology and Clinical NeurophysiologySt. Olav's University HospitalTrondheimNorway
- Department of Neuromedicine and Movement Science, Faculty of Medicine and Health SciencesNorwegian University of Science and TechnologyTrondheimNorway
| | - Laetitia Lalla
- Kavli Institute for Systems Neuroscience and Centre for Neural ComputationFaculty of Medicine and Health Sciences, Norwegian University of Science and TechnologyTrondheimNorway
| | - Nathalie Jurisch‐Yaksi
- Kavli Institute for Systems Neuroscience and Centre for Neural ComputationFaculty of Medicine and Health Sciences, Norwegian University of Science and TechnologyTrondheimNorway
- Department of Neurology and Clinical NeurophysiologySt. Olav's University HospitalTrondheimNorway
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health SciencesNorwegian University of Science and TechnologyTrondheimNorway
| | - Emre Yaksi
- Kavli Institute for Systems Neuroscience and Centre for Neural ComputationFaculty of Medicine and Health Sciences, Norwegian University of Science and TechnologyTrondheimNorway
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11
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Green JL, Dos Santos WF, Fontana ACK. Role of glutamate excitotoxicity and glutamate transporter EAAT2 in epilepsy: Opportunities for novel therapeutics development. Biochem Pharmacol 2021; 193:114786. [PMID: 34571003 DOI: 10.1016/j.bcp.2021.114786] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 09/21/2021] [Accepted: 09/22/2021] [Indexed: 12/21/2022]
Abstract
Epilepsy is a complex neurological syndrome characterized by seizures resulting from neuronal hyperexcitability and sudden and synchronized bursts of electrical discharges. Impaired astrocyte function that results in glutamate excitotoxicity has been recognized to play a key role in the pathogenesis of epilepsy. While there are 26 drugs marketed as anti-epileptic drugs no current treatments are disease modifying as they only suppress seizures rather than the development and progression of epilepsy. Excitatory amino acid transporters (EAATs) are critical for maintaining low extracellular glutamate concentrations and preventing excitotoxicity. When extracellular glutamate concentrations rise to abnormal levels, glutamate receptor overactivation and the subsequent excessive influx of calcium into the post-synaptic neuron can trigger cell death pathways. In this review we discuss targeting EAAT2, the predominant glutamate transporter in the CNS, as a promising approach for developing therapies for epilepsy. EAAT2 upregulation via transcriptional and translational regulation has proven successful in vivo in reducing spontaneous recurrent seizures and offering neuroprotective effects. Another approach to regulate EAAT2 activity is through positive allosteric modulation (PAM). Novel PAMs of EAAT2 have recently been identified and are under development, representing a promising approach for the advance of novel therapeutics for epilepsy.
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Affiliation(s)
- Jennifer Leigh Green
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, 19102, United States
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12
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Alleva C, Machtens JP, Kortzak D, Weyand I, Fahlke C. Molecular Basis of Coupled Transport and Anion Conduction in Excitatory Amino Acid Transporters. Neurochem Res 2021; 47:9-22. [PMID: 33587237 PMCID: PMC8763778 DOI: 10.1007/s11064-021-03252-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 12/15/2022]
Abstract
Glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. After its release from presynaptic nerve terminals, glutamate is quickly removed from the synaptic cleft by excitatory amino acid transporters (EAATs) 1–5, a subfamily of glutamate transporters. The five proteins utilize a complex transport stoichiometry that couples glutamate transport to the symport of three Na+ ions and one H+ in exchange with one K+ to accumulate glutamate against up to 106-fold concentration gradients. They are also anion-selective channels that open and close during transitions along the glutamate transport cycle. EAATs belong to a larger family of secondary-active transporters, the SLC1 family, which also includes purely Na+- or H+-coupled prokaryotic transporters and Na+-dependent neutral amino acid exchangers. In recent years, molecular cloning, heterologous expression, cellular electrophysiology, fluorescence spectroscopy, structural approaches, and molecular simulations have uncovered the molecular mechanisms of coupled transport, substrate selectivity, and anion conduction in EAAT glutamate transporters. Here we review recent findings on EAAT transport mechanisms, with special emphasis on the highly conserved hairpin 2 gate, which has emerged as the central processing unit in many of these functions.
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Affiliation(s)
- Claudia Alleva
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Jülich, Germany
| | - Jan-Philipp Machtens
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Jülich, Germany.,Institute of Clinical Pharmacology, RWTH Aachen University, Aachen, Germany
| | - Daniel Kortzak
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Jülich, Germany
| | - Ingo Weyand
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Jülich, Germany
| | - Christoph Fahlke
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, Jülich, Germany.
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13
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Arkhipova V, Fu H, Hoorens MWH, Trinco G, Lameijer LN, Marin E, Feringa BL, Poelarends GJ, Szymanski W, Slotboom DJ, Guskov A. Structural Aspects of Photopharmacology: Insight into the Binding of Photoswitchable and Photocaged Inhibitors to the Glutamate Transporter Homologue. J Am Chem Soc 2021; 143:1513-1520. [PMID: 33449695 PMCID: PMC7844824 DOI: 10.1021/jacs.0c11336] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
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Photopharmacology addresses the challenge of drug selectivity and
side effects through creation of photoresponsive molecules activated
with light with high spatiotemporal precision. This is achieved through
incorporation of molecular photoswitches and photocages into the pharmacophore.
However, the structural basis for the light-induced modulation of
inhibitory potency in general is still missing, which poses a major
design challenge for this emerging field of research. Here we solved
crystal structures of the glutamate transporter homologue GltTk in complex with photoresponsive transport inhibitors—azobenzene
derivative of TBOA (both in trans and cis configuration) and with the photocaged compound ONB-hydroxyaspartate.
The essential role of glutamate transporters in the functioning of
the central nervous system renders them potential therapeutic targets
in the treatment of neurodegenerative diseases. The obtained structures
provide a clear structural insight into the origins of photocontrol
in photopharmacology and lay the foundation for application of photocontrolled
ligands to study the transporter dynamics by using time-resolved X-ray
crystallography.
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Affiliation(s)
- Valentina Arkhipova
- University Medical Center Groningen, Department of Radiology, Medical Imaging Center, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.,Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Haigen Fu
- Department of Chemical and Pharmaceutical Biology, Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Mark W H Hoorens
- University Medical Center Groningen, Department of Radiology, Medical Imaging Center, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.,Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Gianluca Trinco
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Lucien N Lameijer
- University Medical Center Groningen, Department of Radiology, Medical Imaging Center, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.,Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Egor Marin
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny 141701, Russia
| | - Ben L Feringa
- Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Gerrit J Poelarends
- Department of Chemical and Pharmaceutical Biology, Groningen Research Institute of Pharmacy, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Wiktor Szymanski
- University Medical Center Groningen, Department of Radiology, Medical Imaging Center, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.,Stratingh Institute for Chemistry, Faculty of Science and Engineering, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Dirk J Slotboom
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Albert Guskov
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.,Research Center for Molecular Mechanisms of Aging and Age-related Diseases, Moscow Institute of Physics and Technology, Dolgoprudny 141701, Russia
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14
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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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15
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Neurobiology, Functions, and Relevance of Excitatory Amino Acid Transporters (EAATs) to Treatment of Refractory Epilepsy. CNS Drugs 2020; 34:1089-1103. [PMID: 32926322 DOI: 10.1007/s40263-020-00764-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Epilepsy is one of the most prevalent and devastating neurological disorders characterized by episodes of unusual sensations, loss of awareness, and reoccurring seizures. The frequency and intensity of epileptic fits can vary to a great degree, with almost a third of all cases resistant to available therapies. At present, there is a major unmet need for effective and specific therapeutic intervention. Impairments of the exquisite balance between excitatory and inhibitory synaptic processes in the brain are considered key in the onset and pathophysiology of the disease. As the primary excitatory neurotransmitter in the central nervous system, glutamate has been implicated in the process, with the glutamatergic system holding center stage in the pathobiology as well as in developing disease-modifying therapies. Emerging data pinpoint impairments of glutamate clearance as one of the key causative factors in drug-resistant disease forms. Reinstatement of glutamate homeostasis using pharmacological and genetic modulation of glutamate clearance is therefore considered to be of major translational relevance. In this article, we review the neurobiological and clinical evidence suggesting complex aberrations in the activity and functions of excitatory amino acid transporters (EAATs) in epilepsy, with knock-on effects on glutamate homeostasis as a leading cause for the development of refractory forms. We consider the emerging data on pharmacological and genetic manipulations of EAATs, with reference to seizures and glutamate dyshomeostasis, and review their fundamental and translational relevance. We discuss the most recent advances in the EAATs research in human and animal models, along with numerous questions that remain open for debate and critical appraisal. Contrary to the widely held view on EAATs as a promising therapeutic target for management of refractory epilepsy as well as other neurological and psychiatric conditions related to glutamatergic hyperactivity and glutamate-induced cytotoxicity, we stress that the true relevance of EAAT2 as a target for medical intervention remains to be fully appreciated and verified. Despite decades of research, the emerging properties and functional characteristics of glutamate transporters and their relationship with neurophysiological and behavioral correlates of epilepsy challenge the current perception of this disease and fit unambiguously in neither EAATs functional deficit nor in reversal models. We stress the pressing need for new approaches and models for research and restoration of the physiological activity of glutamate transporters and synaptic transmission to achieve much needed therapeutic effects. The complex mechanism of EAATs regulation by multiple factors, including changes in the electrochemical environment and ionic gradients related to epileptic hyperactivity, impose major therapeutic challenges. As a final note, we consider the evolving views and present a cautious perspective on the key areas of future progress in the field towards better management and treatment of refractory disease forms.
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16
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Transport rate of EAAT2 is regulated by amino acid located at the interface between the scaffolding and substrate transport domains. Neurochem Int 2020; 139:104792. [PMID: 32668264 DOI: 10.1016/j.neuint.2020.104792] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 05/19/2020] [Accepted: 06/21/2020] [Indexed: 01/24/2023]
Abstract
Excitatory Amino Acid Transporters (EAATs) are plasma membrane proteins responsible for maintenance of low extracellular concentrations of glutamate in the CNS. Dysfunction in their activity is implicated in various neurological disorders. Glutamate transport by EAATs occurs through the movement of the central transport domain relative to the scaffold domain in the EAAT membrane protein. Previous studies suggested that residues located within the interface of these two domains in EAAT2, the main subtype of glutamate transporter in the brain, are involved in regulating transport rates. We used mutagenesis, structure-function relationship, surface protein expression and electrophysiology studies, in transfected COS-7 cells and oocytes, to examine residue glycine at position 298, which is located within this interface. Mutation G298A results in increased transport rate without changes in surface expression, suggesting a more hydrophobic and larger alanine results in facilitated transport movement. The increased transport rate does not involve changes in sodium affinity. Electrophysiological currents show that G298A increase both transport and anion currents, suggesting faster transitions through the transport cycle. This work identifies a region critically involved in setting the glutamate transport rate.
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17
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Abstract
Developmental and epileptic encephalopathies (DEEs) can be primarily attributed to genetic causes. The genetic landscape of DEEs has been largely shaped by the rise of high-throughput sequencing, which led to the discovery of new DEE-associated genes and helped identify de novo pathogenic variants. We discuss briefly the contribution of de novo variants to DEE and also focus on alternative inheritance models that contribute to DEE. First, autosomal recessive inheritance in outbred populations may have a larger contribution than previously appreciated, accounting for up to 13% of DEEs. A small subset of genes that typically harbor de novo variants have been associated with recessive inheritance, and often these individuals have more severe clinical presentations. Additionally, pathogenic variants in X-linked genes have been identified in both affected males and females, possibly due to a lack of X-chromosome inactivation skewing. Collectively, exome sequencing has resulted in a molecular diagnosis for many individuals with DEE, but this still leaves many cases unsolved. Multiple factors contribute to the missing etiology, including nonexonic variants, mosaicism, epigenetics, and oligogenic inheritance. Here, we focus on the first 2 factors. We discuss the promises and challenges of genome sequencing, which allows for a more comprehensive analysis of the genome, including interpretation of structural and noncoding variants and also yields a high number of de novo variants for interpretation. We also consider the contribution of genetic mosaicism, both what it means for a molecular diagnosis in mosaic individuals and the important implications for genetic counseling.
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Affiliation(s)
- Hannah C Happ
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Gemma L Carvill
- Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
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18
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Yahyaoui R, Pérez-Frías J. Amino Acid Transport Defects in Human Inherited Metabolic Disorders. Int J Mol Sci 2019; 21:ijms21010119. [PMID: 31878022 PMCID: PMC6981491 DOI: 10.3390/ijms21010119] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/12/2019] [Accepted: 12/18/2019] [Indexed: 02/07/2023] Open
Abstract
Amino acid transporters play very important roles in nutrient uptake, neurotransmitter recycling, protein synthesis, gene expression, cell redox balance, cell signaling, and regulation of cell volume. With regard to transporters that are closely connected to metabolism, amino acid transporter-associated diseases are linked to metabolic disorders, particularly when they involve different organs, cell types, or cell compartments. To date, 65 different human solute carrier (SLC) families and more than 400 transporter genes have been identified, including 11 that are known to include amino acid transporters. This review intends to summarize and update all the conditions in which a strong association has been found between an amino acid transporter and an inherited metabolic disorder. Many of these inherited disorders have been identified in recent years. In this work, the physiological functions of amino acid transporters will be described by the inherited diseases that arise from transporter impairment. The pathogenesis, clinical phenotype, laboratory findings, diagnosis, genetics, and treatment of these disorders are also briefly described. Appropriate clinical and diagnostic characterization of the underlying molecular defect may give patients the opportunity to avail themselves of appropriate therapeutic options in the future.
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Affiliation(s)
- Raquel Yahyaoui
- Laboratory of Metabolic Disorders and Newborn Screening Center of Eastern Andalusia, Málaga Regional University Hospital, 29011 Málaga, Spain
- Grupo Endocrinología y Nutrición, Diabetes y Obesidad, Instituto de Investigación Biomédica de Málaga-IBIMA, 29010 Málaga, Spain
- Correspondence:
| | - Javier Pérez-Frías
- Grupo Multidisciplinar de Investigación Pediátrica, Instituto de Investigación Biomédica de Málaga-IBIMA, 29010 Málaga, Spain;
- Departamento de Farmacología y Pediatría, Facultad de Medicina, Universidad de Málaga, 29010 Málaga, Spain
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19
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The solute carrier transporters and the brain: Physiological and pharmacological implications. Asian J Pharm Sci 2019; 15:131-144. [PMID: 32373195 PMCID: PMC7193445 DOI: 10.1016/j.ajps.2019.09.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 08/17/2019] [Accepted: 09/27/2019] [Indexed: 02/05/2023] Open
Abstract
Solute carriers (SLCs) are the largest family of transmembrane transporters that determine the exchange of various substances, including nutrients, ions, metabolites, and drugs across biological membranes. To date, the presence of about 287 SLC genes have been identified in the brain, among which mutations or the resultant dysfunctions of 71 SLC genes have been reported to be correlated with human brain disorders. Although increasing interest in SLCs have focused on drug development, SLCs are currently still under-explored as drug targets, especially in the brain. We summarize the main substrates and functions of SLCs that are expressed in the brain, with an emphasis on selected SLCs that are important physiologically, pathologically, and pharmacologically in the blood-brain barrier, astrocytes, and neurons. Evidence suggests that a fraction of SLCs are regulated along with the occurrences of brain disorders, among which epilepsy, neurodegenerative diseases, and autism are representative. Given the review of SLCs involved in the onset and procession of brain disorders, we hope these SLCs will be screened as promising drug targets to improve drug delivery to the brain.
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