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Takahashi K, Sato K. The Conventional and Breakthrough Tool for the Study of L-Glutamate Transporters. MEMBRANES 2024; 14:77. [PMID: 38668105 PMCID: PMC11052088 DOI: 10.3390/membranes14040077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 02/26/2024] [Accepted: 03/21/2024] [Indexed: 04/28/2024]
Abstract
In our recent report, we clarified the direct interaction between the excitatory amino acid transporter (EAAT) 1/2 and polyunsaturated fatty acids (PUFAs) by applying electrophysiological and molecular biological techniques to Xenopus oocytes. Xenopus oocytes have a long history of use in the scientific field, but they are still attractive experimental systems for neuropharmacological studies. We will therefore summarize the pharmacological significance, advantages (especially in the study of EAAT2), and experimental techniques that can be applied to Xenopus oocytes; our new findings concerning L-glutamate (L-Glu) transporters and PUFAs; and the significant outcomes of our data. The data obtained from electrophysiological and molecular biological studies of Xenopus oocytes have provided us with further important questions, such as whether or not some PUFAs can modulate EAATs as allosteric modulators and to what extent docosahexaenoic acid (DHA) affects neurotransmission and thereby affects brain functions. Xenopus oocytes have great advantages in the studies about the interactions between molecules and functional proteins, especially in the case when the expression levels of the proteins are small in cell culture systems without transfections. These are also proper to study the mechanisms underlying the interactions. Based on the data collected in Xenopus oocyte experiments, we can proceed to the next step, i.e., the physiological roles of the compounds and their significances. In the case of EAAT2, the effects on the neurotransmission should be examined by electrophysiological approach using acute brain slices. For new drug development, pharmacokinetics pharmacodynamics (PKPD) data and blood brain barrier (BBB) penetration data are also necessary. In order not to miss the promising candidate compounds at the primary stages of drug development, we should reconsider using Xenopus oocytes in the early phase of drug development.
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Grants
- a Research Grant on Regulatory Harmonization and Evaluation of Pharmaceuticals, Medical Devices, Regenerative and Cellular Therapy Products, Gene Therapy Products, and Cosmetics from AMED, Japan Japan Agency for Medical Research and Development
- KAKENHI 18700373, 21700422, 17K08330 Ministry of Education, Culture, Sports, Science and Technology
- a Grant for the Program for Promotion of Fundamental Studies in Health Sciences of NIBIO National Institute of Biomedical Innovation, Health and Nutrition
- a grant for Research on Risks of Chemicals, a Labor Science Research Grant for Research on New Drug Development MHLW
- a Grant-in-Aid from Hoansha Foundation Hoansha Foundation
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Affiliation(s)
| | - Kaoru Sato
- Laboratory of Neuropharmacology, Division of Pharmacology, National Institute of Health Sciences, Kanagawa 210-9501, Japan;
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2
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Mesnard CS, Hays CL, Townsend LE, Barta CL, Gurumurthy CB, Thoreson WB. SYNAPTOTAGMIN-9 IN MOUSE RETINA. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.06.27.546758. [PMID: 37425946 PMCID: PMC10327071 DOI: 10.1101/2023.06.27.546758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Synaptotagmin-9 (Syt9) is a Ca2+ sensor mediating fast synaptic release expressed in various parts of the brain. The presence and role of Syt9 in retina is unknown. We found evidence for Syt9 expression throughout the retina and created mice to conditionally eliminate Syt9 in a cre-dependent manner. We crossed Syt9fl/fl mice with Rho-iCre, HRGP-Cre, and CMV-cre mice to generate mice in which Syt9 was eliminated from rods (rodSyt9CKO), cones (coneSyt9CKO), or whole animals (CMVSyt9). CMVSyt9 mice showed an increase in scotopic electroretinogram (ERG) b-waves evoked by bright flashes with no change in a-waves. Cone-driven photopic ERG b-waves were not significantly different in CMVSyt9 knockout mice and selective elimination of Syt9 from cones had no effect on ERGs. However, selective elimination from rods decreased scotopic and photopic b-waves as well as oscillatory potentials. These changes occurred only with bright flashes where cone responses contribute. Synaptic release was measured in individual rods by recording anion currents activated by glutamate binding to presynaptic glutamate transporters. Loss of Syt9 from rods had no effect on spontaneous or depolarization-evoked release. Our data show that Syt9 is acts at multiple sites in the retina and suggest that it may play a role in regulating transmission of cone signals by rods.
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Affiliation(s)
- Chris S. Mesnard
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68106, USA
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68106, USA
| | - Cassandra L. Hays
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68106, USA
- Department of Medical Education, Creighton University, Omaha, NE 68178
| | - Lou E. Townsend
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68106, USA
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68106, USA
| | - Cody L. Barta
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68106, USA
| | | | - Wallace B. Thoreson
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical Center, Omaha, NE 68106, USA
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68106, USA
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3
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Sánchez-Cano F, Hernández-Kelly LC, Ortega A. Silica Nanoparticles Decrease Glutamate Uptake in Blood-Brain Barrier Components. Neurotox Res 2024; 42:20. [PMID: 38436780 PMCID: PMC10912144 DOI: 10.1007/s12640-024-00696-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 02/06/2024] [Accepted: 02/10/2024] [Indexed: 03/05/2024]
Abstract
Glutamate is the major excitatory amino acid in the vertebrate brain, playing an important role in most brain functions. It exerts its activity through plasma membrane receptors and transporters, expressed both in neurons and glia cells. Overstimulation of neuronal glutamate receptors is linked to cell death in a process known as excitotoxicity, that is prevented by the efficient removal of the neurotransmitter through glutamate transporters enriched in the glia plasma membrane and in the components of the blood-brain barrier (BBB). Silica nanoparticles (SiO2-NPs) have been widely used in biomedical applications and directed to enter the circulatory system; however, little is known about the potential adverse effects of SiO2-NPs exposure on the BBB transport systems that support the critical isolation function between the central nervous system (CNS) and the peripheral circulation. In this contribution, we investigated the plausible SiO2-NPs-mediated disruption of the glutamate transport system expressed by BBB cell components. First, we evaluated the cytotoxic effect of SiO2-NPs on human brain endothelial (HBEC) and Uppsala 87 Malignant glioma (U-87MG) cell lines. Transport kinetics were evaluated, and the exposure effect of SiO2-NPs on glutamate transport activity was determined in both cell lines. Exposure of the cells to different SiO2-NP concentrations (0.4, 4.8, 10, and 20 µg/ml) and time periods (3 and 6 h) did not affect cell viability. We found that the radio-labeled D-aspartate ([3H]-D-Asp) uptake is mostly sodium-dependent, and downregulated by its own substrate (glutamate). Furthermore, SiO2-NPs exposure on endothelial and astrocytes decreases [3H]-D-Asp uptake in a dose-dependent manner. Interestingly, a decrease in the transporter catalytic efficiency, probably linked to a diminution in the affinity of the transporter, was detected upon SiO2-NPs. These results favor the notion that exposure to SiO2-NPs could disrupt BBB function and by these means shed some light into our understanding of the deleterious effects of air pollution on the CNS.
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Affiliation(s)
- Fredy Sánchez-Cano
- Laboratorio de Neurotoxicología, Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, San Pedro Zacatenco, 07300 CDMX, México
| | - Luisa C Hernández-Kelly
- Laboratorio de Neurotoxicología, Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, San Pedro Zacatenco, 07300 CDMX, México
| | - Arturo Ortega
- Laboratorio de Neurotoxicología, Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, San Pedro Zacatenco, 07300 CDMX, México.
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4
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Xia R, Peng HF, Zhang X, Zhang HS. Comprehensive review of amino acid transporters as therapeutic targets. Int J Biol Macromol 2024; 260:129646. [PMID: 38272411 DOI: 10.1016/j.ijbiomac.2024.129646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Revised: 01/17/2024] [Accepted: 01/18/2024] [Indexed: 01/27/2024]
Abstract
The solute carrier (SLC) family, with more than 400 membrane-bound proteins, facilitates the transport of a wide array of substrates such as nutrients, ions, metabolites, and drugs across biological membranes. Amino acid transporters (AATs) are membrane transport proteins that mediate transfer of amino acids into and out of cells or cellular organelles. AATs participate in many important physiological functions including nutrient supply, metabolic transformation, energy homeostasis, redox regulation, and neurological regulation. Several AATs have been found to significantly impact the progression of human malignancies, and dysregulation of AATs results in metabolic reprogramming affecting tumor growth and progression. However, current clinical therapies that directly target AATs have not been developed. The purpose of this review is to highlight the structural and functional diversity of AATs, the molecular mechanisms in human diseases such as tumors, kidney diseases, and emerging therapeutic strategies for targeting AATs.
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Affiliation(s)
- Ran Xia
- College of Chemistry and Life Science, Beijing University of Technology, Pingleyuan 100(#), District of Chaoyang, Beijing 100124, China
| | - Hai-Feng Peng
- College of Chemistry and Life Science, Beijing University of Technology, Pingleyuan 100(#), District of Chaoyang, Beijing 100124, China
| | - Xing Zhang
- College of Chemistry and Life Science, Beijing University of Technology, Pingleyuan 100(#), District of Chaoyang, Beijing 100124, China
| | - Hong-Sheng Zhang
- College of Chemistry and Life Science, Beijing University of Technology, Pingleyuan 100(#), District of Chaoyang, Beijing 100124, China.
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5
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Vyas A, Doshi G. A cross talk on the role of contemporary biomarkers in depression. Biomarkers 2024; 29:18-29. [PMID: 38261718 DOI: 10.1080/1354750x.2024.2308834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 01/14/2024] [Indexed: 01/25/2024]
Abstract
Introduction: Biomarkers can be used to identify determinants of response to various treatments of mental disorders. Evidence to date demonstrates that markers of inflammatory, neurotransmitter, neurotrophic, neuroendocrine, and metabolic function can predict the psychological and physical consequences of depression in individuals, allowing for the development of new therapeutic targets with fewer side effects. Extensive research has included hundreds of potential biomarkers of depression, but their roles in depression, abnormal patients, and how bioinformatics can be used to improve diagnosis, treatment, and prognosis have not been determined or defined. To determine which biomarkers can and cannot be used to predict treatment response, classify patients for specific treatments, and develop targets for new interventions, proprietary strategies, and current research projects need to be tailored.Material and Methods: This review article focuses on - biomarker systems that would help in the further development and expansion of newer targets - which holds great promise for reducing the burden of depression.Results and Discussion: Further, this review point to the inflammatory response, metabolic marker, and microribonucleic acids, long non-coding RNAs, HPA axis which are - related to depression and can serve as future targets.
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Affiliation(s)
- Aditi Vyas
- Department of Pharmacology, SVKM's Dr. Bhanuben Nanavati College of Pharmacy, Mumbai, India
| | - Gaurav Doshi
- Department of Pharmacology, SVKM's Dr. Bhanuben Nanavati College of Pharmacy, Mumbai, India
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6
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Katane M, Homma H. Biosynthesis and Degradation of Free D-Amino Acids and Their Physiological Roles in the Periphery and Endocrine Glands. Biol Pharm Bull 2024; 47:562-579. [PMID: 38432912 DOI: 10.1248/bpb.b23-00485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/05/2024]
Abstract
It was long believed that D-amino acids were either unnatural isomers or laboratory artifacts, and that the important functions of amino acids were exerted only by L-amino acids. However, recent investigations have revealed a variety of D-amino acids in mammals that play important roles in physiological functions, including free D-serine and D-aspartate that are crucial in the central nervous system. The functions of several D-amino acids in the periphery and endocrine glands are also receiving increasing attention. Here, we present an overview of recent advances in elucidating the physiological roles of D-amino acids, especially in the periphery and endocrine glands.
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Affiliation(s)
- Masumi Katane
- Medicinal Research Laboratories, Graduate School of Pharmaceutical Sciences, Kitasato University
| | - Hiroshi Homma
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University
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Thoreson WB, Chhunchha B. EAAT5 glutamate transporter rapidly binds glutamate with micromolar affinity in mouse rods. J Gen Physiol 2023; 155:e202313349. [PMID: 37477643 PMCID: PMC10359920 DOI: 10.1085/jgp.202313349] [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: 01/24/2023] [Revised: 04/17/2023] [Accepted: 07/05/2023] [Indexed: 07/22/2023] Open
Abstract
Light responses of rod photoreceptor cells in the retina are encoded by changes in synaptic glutamate release that is in turn shaped by reuptake involving EAAT5 plasma membrane glutamate transporters. Heterologously expressed EAAT5 activates too slowly upon glutamate binding to support significant uptake. We tested EAAT5 activation in mouse rods in vivo by stimulating glutamate transporter anion currents (IA(glu)) with UV flash photolysis of MNI-glutamate, varying flash intensity to vary glutamate levels. Responses to uncaging rose rapidly with time constants of 2-3 ms, similar to IA(glu) events arising from spontaneous release. Spontaneous release events and IA(glu) evoked by weak flashes also declined with similar time constants of 40-50 ms. Stronger flashes evoked responses that decayed more slowly. Time constants were twofold faster at 35°C, suggesting that they reflect transporter kinetics, not diffusion. Selective EAAT1 and EAAT2 inhibitors had no significant effect, suggesting IA(glu) in rods arises solely from EAAT5. We calibrated glutamate levels attained during flash photolysis by expressing a fluorescent glutamate sensor iGluSnFr in cultured epithelial cells. We compared fluorescence at different glutamate concentrations to fluorescence evoked by photolytic uncaging of MNI-glutamate. The relationship between flash intensity and glutamate yielded EC50 values for EAAT5 amplitude, decay time, and rise time of ∼10 μM. Micromolar affinity and rapid activation of EAAT5 in rods show it can rapidly bind synaptic glutamate. However, we also found that EAAT5 currents are saturated by the synchronous release of only a few vesicles, suggesting limited capacity and a role for glial uptake at higher release rates.
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Affiliation(s)
- Wallace B. Thoreson
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| | - Bhavana Chhunchha
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
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8
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Nimgampalle M, Chakravarthy H, Sharma S, Shree S, Bhat AR, Pradeepkiran JA, Devanathan V. Neurotransmitter systems in the etiology of major neurological disorders: Emerging insights and therapeutic implications. Ageing Res Rev 2023; 89:101994. [PMID: 37385351 DOI: 10.1016/j.arr.2023.101994] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 06/21/2023] [Accepted: 06/25/2023] [Indexed: 07/01/2023]
Abstract
Neurotransmitters serve as chemical messengers playing a crucial role in information processing throughout the nervous system, and are essential for healthy physiological and behavioural functions in the body. Neurotransmitter systems are classified as cholinergic, glutamatergic, GABAergic, dopaminergic, serotonergic, histaminergic, or aminergic systems, depending on the type of neurotransmitter secreted by the neuron, allowing effector organs to carry out specific functions by sending nerve impulses. Dysregulation of a neurotransmitter system is typically linked to a specific neurological disorder. However, more recent research points to a distinct pathogenic role for each neurotransmitter system in more than one neurological disorder of the central nervous system. In this context, the review provides recently updated information on each neurotransmitter system, including the pathways involved in their biochemical synthesis and regulation, their physiological functions, pathogenic roles in diseases, current diagnostics, new therapeutic targets, and the currently used drugs for associated neurological disorders. Finally, a brief overview of the recent developments in neurotransmitter-based therapeutics for selected neurological disorders is offered, followed by future perspectives in that area of research.
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Affiliation(s)
- Mallikarjuna Nimgampalle
- Department of Biology, Indian Institute of Science Education and Research Tirupati (IISER T), Transit campus, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India
| | - Harshini Chakravarthy
- Department of Biology, Indian Institute of Science Education and Research Tirupati (IISER T), Transit campus, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India.
| | - Sapana Sharma
- Department of Biology, Indian Institute of Science Education and Research Tirupati (IISER T), Transit campus, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India
| | - Shruti Shree
- Department of Biology, Indian Institute of Science Education and Research Tirupati (IISER T), Transit campus, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India
| | - Anoop Ramachandra Bhat
- Department of Biology, Indian Institute of Science Education and Research Tirupati (IISER T), Transit campus, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India
| | | | - Vasudharani Devanathan
- Department of Biology, Indian Institute of Science Education and Research Tirupati (IISER T), Transit campus, Karakambadi Road, Mangalam, Tirupati 517507, Andhra Pradesh, India.
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9
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Wang L, Chen Y, Wang M, Zhao C, Qiao D. Relationship between gene-environment interaction and obsessive-compulsive disorder: A systematic review. J Psychiatr Res 2023; 164:281-290. [PMID: 37390623 DOI: 10.1016/j.jpsychires.2023.06.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 04/29/2023] [Accepted: 06/15/2023] [Indexed: 07/02/2023]
Abstract
BACKGROUND Gene-environment interaction (G × E) refers to the change of genetic effects under the participation of environmental factors resulting in differences in genetic expression. G × E has been studied in the occurrence and development of many neuropsychiatric disorders, including obsessive-compulsive disorder (OCD). AIM A systematic review was conducted to investigate the role of G × E plays in OCD. This review explored the relationship between G × E and the susceptibility to OCD occurrence, disease progression, and treatment response. METHODS This systematic literature search was performed using Web of Science, PubMed, Cochrane Library, and CNKI. Seven studies were selected, which included seven genes (BDNF, COMT, MAO, 5-HTT, SMAD4, PGRN, and SLC1A1) polymorphisms, polygenic risk score (PRS), and two environmental factors (childhood trauma and stressful life events). RESULTS Information from this systematic review indicated that G × E increased the susceptibility to OCD, played a crucial role in the clinical characteristics, and had an inconsistent impact on treatment response of OCD. FUTURE DIRECTIONS The multi-omics studies and the inclusion of G × E in future GWAS studies of OCD should be drawn more attention, which may contribute to a deeper understanding of the etiology of OCD as well as guide therapeutic interventions for the disease.
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Affiliation(s)
- Lina Wang
- Department of Psychology, Shandong Normal University, Jinan, Shandong, 250358, China; Department of Psychiatry, Shandong Mental Health Center, Shandong University, Jinan, Shandong, 250014, China
| | - Yu Chen
- Jining Medical University, Jining, Shandong, 272000, China
| | - Miao Wang
- Jining Medical University, Jining, Shandong, 272000, China
| | - Chaoben Zhao
- Jining Medical University, Jining, Shandong, 272000, China
| | - Dongdong Qiao
- Department of Psychiatry, Shandong Mental Health Center, Shandong University, Jinan, Shandong, 250014, China.
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10
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Qiu B, Boudker O. Symport and antiport mechanisms of human glutamate transporters. Nat Commun 2023; 14:2579. [PMID: 37142617 PMCID: PMC10160106 DOI: 10.1038/s41467-023-38120-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Accepted: 04/17/2023] [Indexed: 05/06/2023] Open
Abstract
Excitatory amino acid transporters (EAATs) uptake glutamate into glial cells and neurons. EAATs achieve million-fold transmitter gradients by symporting it with three sodium ions and a proton, and countertransporting a potassium ion via an elevator mechanism. Despite the availability of structures, the symport and antiport mechanisms still need to be clarified. We report high-resolution cryo-EM structures of human EAAT3 bound to the neurotransmitter glutamate with symported ions, potassium ions, sodium ions alone, or without ligands. We show that an evolutionarily conserved occluded translocation intermediate has a dramatically higher affinity for the neurotransmitter and the countertransported potassium ion than outward- or inward-facing transporters and plays a crucial role in ion coupling. We propose a comprehensive ion coupling mechanism involving a choreographed interplay between bound solutes, conformations of conserved amino acid motifs, and movements of the gating hairpin and the substrate-binding domain.
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Affiliation(s)
- Biao Qiu
- Department of Physiology & Biophysics, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10021, USA.
| | - Olga Boudker
- Department of Physiology & Biophysics, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10021, USA.
- Howard Hughes Medical Institute, Weill Cornell Medicine, 1300 York Ave, New York, NY, 10021, USA.
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11
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Milanetti E, Miotto M, Bo' L, Di Rienzo L, Ruocco G. Investigating the competition between ACE2 natural molecular interactors and SARS-CoV-2 candidate inhibitors. Chem Biol Interact 2023; 374:110380. [PMID: 36822303 PMCID: PMC9942480 DOI: 10.1016/j.cbi.2023.110380] [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: 08/20/2022] [Revised: 01/22/2023] [Accepted: 02/01/2023] [Indexed: 02/23/2023]
Abstract
The SARS-CoV-2 pandemic still poses a threat to the global health as the virus continues spreading in most countries. Therefore, the identification of molecules capable of inhibiting the binding between the ACE2 receptor and the SARS-CoV-2 spike protein is of paramount importance. Recently, two DNA aptamers were designed with the aim to inhibit the interaction between the ACE2 receptor and the spike protein of SARS-CoV-2. Indeed, the two molecules interact with the ACE2 receptor in the region around the K353 residue, preventing its binding of the spike protein. If on the one hand this inhibition process hinders the entry of the virus into the host cell, it could lead to a series of side effects, both in physiological and pathological conditions, preventing the correct functioning of the ACE2 receptor. Here, we discuss through a computational study the possible effect of these two very promising DNA aptamers, investigating all possible interactions between ACE2 and its experimentally known molecular partners. Our in silico predictions show that some of the 10 known molecular partners of ACE2 could interact, physiologically or pathologically, in a region adjacent to the K353 residue. Thus, the curative action of the proposed DNA aptamers could recruit ACE2 from its biological functions.
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Affiliation(s)
- Edoardo Milanetti
- Department of Physics, Sapienza University, Piazzale Aldo Moro 5, 00185, Rome, Italy; Center for Life Nanoscience, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161, Rome, Italy.
| | - Mattia Miotto
- Center for Life Nanoscience, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161, Rome, Italy
| | - Leonardo Bo'
- Center for Life Nanoscience, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161, Rome, Italy
| | - Lorenzo Di Rienzo
- Center for Life Nanoscience, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161, Rome, Italy
| | - Giancarlo Ruocco
- Department of Physics, Sapienza University, Piazzale Aldo Moro 5, 00185, Rome, Italy; Center for Life Nanoscience, Istituto Italiano di Tecnologia, Viale Regina Elena 291, 00161, Rome, Italy
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12
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Colucci E, Anshari ZR, Patiño-Ruiz MF, Nemchinova M, Whittaker J, Slotboom DJ, Guskov A. Mutation in glutamate transporter homologue GltTk provides insights into pathologic mechanism of episodic ataxia 6. Nat Commun 2023; 14:1799. [PMID: 37002226 PMCID: PMC10066184 DOI: 10.1038/s41467-023-37503-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 03/20/2023] [Indexed: 04/03/2023] Open
Abstract
Episodic ataxias (EAs) are rare neurological conditions affecting the nervous system and typically leading to motor impairment. EA6 is linked to the mutation of a highly conserved proline into an arginine in the glutamate transporter EAAT1. In vitro studies showed that this mutation leads to a reduction in the substrates transport and an increase in the anion conductance. It was hypothesised that the structural basis of these opposed functional effects might be the straightening of transmembrane helix 5, which is kinked in the wild-type protein. In this study, we present the functional and structural implications of the mutation P208R in the archaeal homologue of glutamate transporters GltTk. We show that also in GltTk the P208R mutation leads to reduced aspartate transport activity and increased anion conductance, however a cryo-EM structure reveals that the kink is preserved. The arginine side chain of the mutant points towards the lipidic environment, where it may engage in interactions with the phospholipids, thereby potentially interfering with the transport cycle and contributing to stabilisation of an anion conducting state.
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Affiliation(s)
- Emanuela Colucci
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands
| | - Zaid R Anshari
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands
| | - Miyer F Patiño-Ruiz
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands
| | - Mariia Nemchinova
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands
| | - Jacob Whittaker
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands
| | - Dirk J Slotboom
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands.
| | - Albert Guskov
- Groningen Institute for Biomolecular Sciences and Biotechnology, University of Groningen, 9747AG, Groningen, the Netherlands.
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13
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Wang X, Roberts PA, Yoshimatsu T, Lagnado L, Baden T. Amacrine cells differentially balance zebrafish color circuits in the central and peripheral retina. Cell Rep 2023; 42:112055. [PMID: 36757846 DOI: 10.1016/j.celrep.2023.112055] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 11/01/2022] [Accepted: 01/18/2023] [Indexed: 02/10/2023] Open
Abstract
The vertebrate inner retina is driven by photoreceptors whose outputs are already pre-processed; in zebrafish, outer retinal circuits split "color" from "grayscale" information across four cone-photoreceptor types. It remains unclear how the inner retina processes incoming spectral information while also combining cone signals to shape grayscale functions. We address this question by imaging the light-driven responses of amacrine cells (ACs) and bipolar cells (BCs) in larval zebrafish in the presence and pharmacological absence of inner retinal inhibition. We find that ACs enhance opponency in some bipolar cells while at the same time suppressing pre-existing opponency in others, so that, depending on the retinal region, the net change in the number of color-opponent units is essentially zero. To achieve this "dynamic balance," ACs counteract intrinsic color opponency of BCs via the On channel. Consistent with these observations, Off-stratifying ACs are exclusively achromatic, while all color-opponent ACs stratify in the On sublamina.
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Affiliation(s)
- Xinwei Wang
- School of Life Sciences, University of Sussex, Biology Road, Brighton BN1 9QG, UK.
| | - Paul A Roberts
- School of Life Sciences, University of Sussex, Biology Road, Brighton BN1 9QG, UK
| | - Takeshi Yoshimatsu
- School of Life Sciences, University of Sussex, Biology Road, Brighton BN1 9QG, UK
| | - Leon Lagnado
- School of Life Sciences, University of Sussex, Biology Road, Brighton BN1 9QG, UK.
| | - Tom Baden
- School of Life Sciences, University of Sussex, Biology Road, Brighton BN1 9QG, UK; Institute of Ophthalmic Research, University of Tübingen, Elfriede-Aulhorn-Strasse 7, 72076 Tübingen, Germany.
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14
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Fontana IC, Souza DG, Souza DO, Gee A, Zimmer ER, Bongarzone S. A Medicinal Chemistry Perspective on Excitatory Amino Acid Transporter 2 Dysfunction in Neurodegenerative Diseases. J Med Chem 2023; 66:2330-2346. [PMID: 36787643 PMCID: PMC9969404 DOI: 10.1021/acs.jmedchem.2c01572] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The excitatory amino acid transporter 2 (EAAT2) plays a key role in the clearance and recycling of glutamate - the major excitatory neurotransmitter in the mammalian brain. EAAT2 loss/dysfunction triggers a cascade of neurodegenerative events, comprising glutamatergic excitotoxicity and neuronal death. Nevertheless, our current knowledge regarding EAAT2 in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD), is restricted to post-mortem analysis of brain tissue and experimental models. Thus, detecting EAAT2 in the living human brain might be crucial to improve diagnosis/therapy for ALS and AD. This perspective article describes the role of EAAT2 in physio/pathological processes and provides a structure-activity relationship of EAAT2-binders, bringing two perspectives: therapy (activators) and diagnosis (molecular imaging tools).
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Affiliation(s)
- Igor C Fontana
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom.,Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, 90035-003 Porto Alegre, Brazil.,Division of Clinical Geriatrics, Center for Alzheimer Research, Department of Neurobiology, Care Sciences and Society, Karolinska Institutet, Blickagången 16 - Neo floor seventh, 141 83 Stockholm, Sweden
| | - Débora G Souza
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, 90035-003 Porto Alegre, Brazil.,Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, Av. Ipiranga, 6681 Porto Alegre, Brazil
| | - Diogo O Souza
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, 90035-003 Porto Alegre, Brazil.,Department of Biochemistry, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, 90035-003 Porto Alegre, Brazil
| | - Antony Gee
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
| | - Eduardo R Zimmer
- Department of Biochemistry, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, 90035-003 Porto Alegre, Brazil.,Department of Pharmacology, Universidade Federal do Rio Grande do Sul, Av. Sarmento Leite 500, sala, 90035-003 Porto Alegre, Brazil.,Graduate Program in Biological Sciences: Biochemistry (PPGBioq), and Pharmacology and Therapeutics (PPGFT), Universidade Federal do Rio Grande do Sul, Av. Sarmento Leite 500, sala, 305 Porto Alegre, Brazil.,Brain Institute of Rio Grande do Sul, Pontifical Catholic University of Rio Grande do Sul, Av. Ipiranga, 6681 Porto Alegre, Brazil.,McGill University Research Centre for Studies in Aging, McGill University, Montreal, Quebec H4H 1R3, Canada
| | - Salvatore Bongarzone
- School of Biomedical Engineering and Imaging Sciences, St Thomas' Hospital, King's College London, London SE1 7EH, United Kingdom
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15
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Krishna G, Pillai VS, Gopi P, Nair AS, Veettil MV. Epstein-Barr virus infection controls the concentration of the intracellular antioxidant glutathione by upregulation of the glutamate transporter EAAT3 in tumor cells. Virus Genes 2023; 59:55-66. [PMID: 36344769 DOI: 10.1007/s11262-022-01951-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 10/04/2022] [Indexed: 11/09/2022]
Abstract
Epstein-Barr virus or human herpesvirus 4 (EBV/HHV-4) is an omnipresent oncovirus etiologically associated with various B-cell lymphomas and epithelial cancers. The malignant transformation associated with the persistent expression of viral proteins often deregulates the host cellular machinery and EBV infection is coupled to elevated levels of reactive oxygen species. Here, we investigated the role that the glutamate transporter EAAT3 plays in regulating the antioxidant system as a protective mechanism of EBV-infected cells against the virus-induced oxidative stress. Our study demonstrated that the expression of EAAT3 was upregulated and localized to the plasma membrane in EBV latently infected and de novo EBV-infected cells. EAAT3 was regulated by the transcription factor NFAT5 in the infected cells. Membrane localized EAAT3 was found to be involved in the transportation of glutamate from the extracellular space into the cell, as EAAT3 and NFAT5 inhibitors markedly reduced the levels of intracellular glutamate levels in EBV latently infected cells. Additionally, our data demonstrated a notable decrease in the intracellular glutathione levels following treatment with an EAAT3 inhibitor. Collectively, our results suggest that upregulation of the glutamate transporter EAAT3 is an adaptation of EBV-infected cells to maintain cellular redox homeostasis against the virus-induced oxidative stress, and that this cellular balance could be therapeutically destroyed by targeting EAAT3 to impede EBV-associated cancers.
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Affiliation(s)
- Gayathri Krishna
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India
| | - Vinod Soman Pillai
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India
- Institute of Advanced Virology (IAV), Thonnakkal, Thiruvananthapuram, Kerala, 695317, India
| | - Poornima Gopi
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India
| | - Anuja S Nair
- Institute of Advanced Virology (IAV), Thonnakkal, Thiruvananthapuram, Kerala, 695317, India
| | - Mohanan Valiya Veettil
- Department of Biotechnology, Cochin University of Science and Technology, Cochin, Kerala, 682022, India.
- Institute of Advanced Virology (IAV), Thonnakkal, Thiruvananthapuram, Kerala, 695317, India.
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16
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Silva-Parra J, Sandu C, Felder-Schmittbuhl MP, Hernández-Kelly LC, Ortega A. Aryl Hydrocarbon Receptor in Glia Cells: A Plausible Glutamatergic Neurotransmission Orchestrator. Neurotox Res 2023; 41:103-117. [PMID: 36607593 DOI: 10.1007/s12640-022-00623-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 11/23/2022] [Accepted: 12/15/2022] [Indexed: 01/07/2023]
Abstract
Glutamate is the major excitatory amino acid in the vertebrate brain. Glutamatergic signaling is involved in most of the central nervous system functions. Its main components, namely receptors, ion channels, and transporters, are tightly regulated at the transcriptional, translational, and post-translational levels through a diverse array of extracellular signals, such as food, light, and neuroactive molecules. An exquisite and well-coordinated glial/neuronal bidirectional communication is required for proper excitatory amino acid signal transactions. Biochemical shuttles such as the glutamate/glutamine and the astrocyte-neuronal lactate represent the fundamental involvement of glial cells in glutamatergic transmission. In fact, the disruption of any of these coordinated biochemical intercellular cascades leads to an excitotoxic insult that underlies some aspects of most of the neurodegenerative diseases characterized thus far. In this contribution, we provide a comprehensive summary of the involvement of the Aryl hydrocarbon receptor, a ligand-dependent transcription factor in the gene expression regulation of glial glutamate transporters. These receptors might serve as potential targets for the development of novel strategies for the treatment of neurodegenerative diseases.
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Affiliation(s)
- Janisse Silva-Parra
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, San Pedro Zacatenco, 07360, CDMX, México
| | - Cristina Sandu
- Centre National de la Recherche Scientifique, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, Strasbourg, France
| | - Marie-Paule Felder-Schmittbuhl
- Centre National de la Recherche Scientifique, Institut des Neurosciences Cellulaires et Intégratives, Université de Strasbourg, Strasbourg, France
| | - Luisa C Hernández-Kelly
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, San Pedro Zacatenco, 07360, CDMX, México
| | - Arturo Ortega
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. IPN 2508, San Pedro Zacatenco, 07360, CDMX, México.
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17
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Cuellar-Santoyo AO, Ruiz-Rodríguez VM, Mares-Barbosa TB, Patrón-Soberano A, Howe AG, Portales-Pérez DP, Miquelajáuregui Graf A, Estrada-Sánchez AM. Revealing the contribution of astrocytes to glutamatergic neuronal transmission. Front Cell Neurosci 2023; 16:1037641. [PMID: 36744061 PMCID: PMC9893894 DOI: 10.3389/fncel.2022.1037641] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 12/20/2022] [Indexed: 01/20/2023] Open
Abstract
Research on glutamatergic neurotransmission has focused mainly on the function of presynaptic and postsynaptic neurons, leaving astrocytes with a secondary role only to ensure successful neurotransmission. However, recent evidence indicates that astrocytes contribute actively and even regulate neuronal transmission at different levels. This review establishes a framework by comparing glutamatergic components between neurons and astrocytes to examine how astrocytes modulate or otherwise influence neuronal transmission. We have included the most recent findings about the role of astrocytes in neurotransmission, allowing us to understand the complex network of neuron-astrocyte interactions. However, despite the knowledge of synaptic modulation by astrocytes, their contribution to specific physiological and pathological conditions remains to be elucidated. A full understanding of the astrocyte's role in neuronal processing could open fruitful new frontiers in the development of therapeutic applications.
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Affiliation(s)
- Ares Orlando Cuellar-Santoyo
- División de Biología Molecular, Laboratorio de Neurobiología, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, Mexico
| | - Victor Manuel Ruiz-Rodríguez
- División de Biología Molecular, Laboratorio de Neurobiología, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, Mexico
| | - Teresa Belem Mares-Barbosa
- División de Biología Molecular, Laboratorio de Neurobiología, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, Mexico,Translational and Molecular Medicine Laboratory, Research Center for Health Sciences and Biomedicine, Autonomous University of San Luis Potosí, San Luis Potosí, Mexico
| | - Araceli Patrón-Soberano
- División de Biología Molecular, Laboratorio de Neurobiología, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, Mexico
| | - Andrew G. Howe
- Intelligent Systems Laboratory, HRL Laboratories, LLC, Malibu, CA, United States
| | - Diana Patricia Portales-Pérez
- Translational and Molecular Medicine Laboratory, Research Center for Health Sciences and Biomedicine, Autonomous University of San Luis Potosí, San Luis Potosí, Mexico
| | | | - Ana María Estrada-Sánchez
- División de Biología Molecular, Laboratorio de Neurobiología, Instituto Potosino de Investigación Científica y Tecnológica (IPICYT), San Luis Potosí, Mexico,*Correspondence: Ana María Estrada-Sánchez
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18
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Fan Y, Huang H, Shao J, Huang W. MicroRNA-mediated regulation of reactive astrocytes in central nervous system diseases. Front Mol Neurosci 2023; 15:1061343. [PMID: 36710937 PMCID: PMC9877358 DOI: 10.3389/fnmol.2022.1061343] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 12/22/2022] [Indexed: 01/15/2023] Open
Abstract
Astrocytes (AST) are abundant glial cells in the human brain, accounting for approximately 20-50% percent of mammalian central nervous system (CNS) cells. They display essential functions necessary to sustain the physiological processes of the CNS, including maintaining neuronal structure, forming the blood-brain barrier, coordinating neuronal metabolism, maintaining the extracellular environment, regulating cerebral blood flow, stabilizing intercellular communication, participating in neurotransmitter synthesis, and defending against oxidative stress et al. During the pathological development of brain tumors, stroke, spinal cord injury (SCI), neurodegenerative diseases, and other neurological disorders, astrocytes undergo a series of highly heterogeneous changes, which are called reactive astrocytes, and mediate the corresponding pathophysiological process. However, the pathophysiological mechanisms of reactive astrocytes and their therapeutic relevance remain unclear. The microRNAs (miRNAs) are essential for cell differentiation, proliferation, and survival, which play a crucial role in the pathophysiological development of CNS diseases. In this review, we summarize the regulatory mechanism of miRNAs on reactive astrocytes in CNS diseases, which might provide a theoretical basis for the diagnosis and treatment of CNS diseases.
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19
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Duarte-Silva AT, Ximenes LGR, Guimarães-Souza M, Domith I, Paes-de-Carvalho R. Chemical signaling in the developing avian retina: Focus on cyclic AMP and AKT-dependent pathways. Front Cell Dev Biol 2022; 10:1058925. [PMID: 36568967 PMCID: PMC9780464 DOI: 10.3389/fcell.2022.1058925] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/28/2022] [Indexed: 12/13/2022] Open
Abstract
Communication between developing progenitor cells as well as differentiated neurons and glial cells in the nervous system is made through direct cell contacts and chemical signaling mediated by different molecules. Several of these substances are synthesized and released by developing cells and play roles since early stages of Central Nervous System development. The chicken retina is a very suitable model for neurochemical studies, including the study of regulation of signaling pathways during development. Among advantages of the model are its very well-known histogenesis, the presence of most neurotransmitter systems found in the brain and the possibility to make cultures of neurons and/or glial cells where many neurochemical functions develop in a similar way than in the intact embryonic tissue. In the chicken retina, some neurotransmitters or neuromodulators as dopamine, adenosine, and others are coupled to cyclic AMP production or adenylyl cyclase inhibition since early stages of development. Other substances as vitamin C and nitric oxide are linked to the major neurotransmitter glutamate and AKT metabolism. All these different systems regulate signaling pathways, including PKA, PKG, SRC, AKT and ERK, and the activation of the transcription factor CREB. Dopamine and adenosine stimulate cAMP accumulation in the chick embryo retina through activation of D1 and A2a receptors, respectively, but the onset of dopamine stimulation is much earlier than that of adenosine. However, adenosine can inhibit adenylyl cyclase and modulate dopamine-dependent cAMP increase since early developmental stages through A1 receptors. Dopamine stimulates different PKA as well as EPAC downstream pathways both in intact tissue and in culture as the CSK-SRC pathway modulating glutamate NMDA receptors as well as vitamin C release and CREB phosphorylation. By the other hand, glutamate modulates nitric oxide production and AKT activation in cultured retinal cells and this pathway controls neuronal survival in retina. Glutamate and adenosine stimulate the release of vitamin C and this vitamin regulates the transport of glutamate, activation of NMDA receptors and AKT phosphorylation in cultured retinal cells. In the present review we will focus on these reciprocal interactions between neurotransmitters or neuromodulators and different signaling pathways during retinal development.
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Affiliation(s)
- A. T. Duarte-Silva
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - L. G. R. Ximenes
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - M. Guimarães-Souza
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - I. Domith
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil
| | - R. Paes-de-Carvalho
- Program of Neurosciences, Institute of Biology, Fluminense Federal University, Niterói, Brazil,Department of Neurobiology, Institute of Biology, Fluminense Federal University, Niterói, Brazil,*Correspondence: R. Paes-de-Carvalho,
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20
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Leucine 434 is essential for docosahexaenoic acid-induced augmentation of L-glutamate transporter current. J Biol Chem 2022; 299:102793. [PMID: 36509140 PMCID: PMC9823230 DOI: 10.1016/j.jbc.2022.102793] [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: 04/13/2022] [Revised: 11/30/2022] [Accepted: 12/04/2022] [Indexed: 12/14/2022] Open
Abstract
Astrocytic excitatory amino acid transporter 2 (EAAT2) plays a major role in removing the excitatory neurotransmitter L-glutamate (L-Glu) from synaptic clefts in the forebrain to prevent excitotoxicity. Polyunsaturated fatty acids such as docosahexaenoic acid (DHA, 22:6 n-3) enhance synaptic transmission, and their target molecules include EAATs. Here, we aimed to investigate the effect of DHA on EAAT2 and identify the key amino acid for DHA/EAAT2 interaction by electrophysiological recording of L-Glu-induced current in Xenopus oocytes transfected with EAATs, their chimeras, and single mutants. DHA transiently increased the amplitude of EAAT2 but tended to decrease that of excitatory amino acid transporter subtype 1 (EAAT1), another astrocytic EAAT. Single mutation of leucine (Leu) 434 to alanine (Ala) completely suppressed the augmentation by DHA, while mutation of EAAT1 Ala 435 (corresponding to EAAT2 Leu434) to Leu changed the effect from suppression to augmentation. Other polyunsaturated fatty acids (docosapentaenoic acid, eicosapentaenoic acid, arachidonic acid, and α-linolenic acid) similarly augmented the EAAT2 current and suppressed the EAAT1 current. Finally, our docking analysis suggested the most stable docking site is the lipid crevice of EAAT2, in close proximity to the L-Glu and sodium binding sites, suggesting that the DHA/Leu434 interaction might affect the elevator-like slide and/or the shapes of the other binding sites. Collectively, our results highlight a key molecular detail in the DHA-induced regulation of synaptic transmission involving EAATs.
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21
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Mesnard CS, Hays CL, Barta CL, Sladek AL, Grassmeyer JJ, Hinz KK, Quadros RM, Gurumurthy CB, Thoreson WB. Synaptotagmins 1 and 7 in vesicle release from rods of mouse retina. Exp Eye Res 2022; 225:109279. [PMID: 36280223 PMCID: PMC9830644 DOI: 10.1016/j.exer.2022.109279] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/14/2022] [Accepted: 10/10/2022] [Indexed: 01/13/2023]
Abstract
Synaptotagmins are the primary Ca2+ sensors for synaptic exocytosis. Previous work suggested synaptotagmin-1 (Syt1) mediates evoked vesicle release from cone photoreceptor cells in the vertebrate retina whereas release from rods may involve another sensor in addition to Syt1. We found immunohistochemical evidence for syntaptotagmin-7 (Syt7) in mouse rod terminals and so performed electroretinograms (ERG) and single-cell recordings using mice in which Syt1 and/or Syt7 were conditionally removed from rods and/or cones. Synaptic release was measured in mouse rods by recording presynaptic anion currents activated during glutamate re-uptake and from exocytotic membrane capacitance changes. Deleting Syt1 from rods reduced glutamate release evoked by short depolarizing steps but not long steps whereas deleting Syt7 from rods reduced release evoked by long but not short steps. Deleting both sensors completely abolished depolarization-evoked release from rods. Effects of various intracellular Ca2+ buffers showed that Syt1-mediated release from rods involves vesicles close to ribbon-associated Ca2+ channels whereas Syt7-mediated release evoked by longer steps involves more distant release sites. Spontaneous release from rods was unaffected by eliminating Syt7. While whole animal knockout of Syt7 slightly reduced ERG b-waves and oscillatory potentials, selective elimination of Syt7 from rods had no effect on ERGs. Furthermore, eliminating Syt1 from rods and cones abolished ERG b-waves and additional elimination of Syt7 had no further effect. These results show that while Syt7 contributes to slow non-ribbon release from rods, Syt1 is the principal sensor shaping rod and cone inputs to bipolar cells in response to light flashes.
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Affiliation(s)
- C S Mesnard
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA; Pharmacology and Experimental Neuroscience, USA
| | - C L Hays
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - C L Barta
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - A L Sladek
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - J J Grassmeyer
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA; Pharmacology and Experimental Neuroscience, USA
| | - K K Hinz
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA
| | - R M Quadros
- Pharmacology and Experimental Neuroscience, USA; Mouse Genome Engineering Core Facility, Vice Chancellor for Research Office, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68106, USA
| | - C B Gurumurthy
- Pharmacology and Experimental Neuroscience, USA; Mouse Genome Engineering Core Facility, Vice Chancellor for Research Office, College of Medicine, University of Nebraska Medical Center, Omaha, NE, 68106, USA
| | - W B Thoreson
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, USA; Pharmacology and Experimental Neuroscience, USA.
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22
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Boulund U, Bastos DM, Ferwerda B, van den Born BJ, Pinto-Sietsma SJ, Galenkamp H, Levin E, Groen AK, Zwinderman AH, Nieuwdorp M. Gut microbiome associations with host genotype vary across ethnicities and potentially influence cardiometabolic traits. Cell Host Microbe 2022; 30:1464-1480.e6. [PMID: 36099924 DOI: 10.1016/j.chom.2022.08.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 06/16/2022] [Accepted: 08/17/2022] [Indexed: 12/13/2022]
Abstract
Previous studies in mainly European populations have reported that the gut microbiome composition is associated with the human genome. However, the genotype-microbiome interaction in different ethnicities is largely unknown. We performed a large fecal microbiome genome-wide association study of a single multiethnic cohort, the Healthy Life in an Urban Setting (HELIUS) cohort (N = 4,117). Mendelian randomization was performed using the multiethnic Pan-UK Biobank (N = 460,000) to dissect potential causality. We identified ethnicity-specific associations between host genomes and gut microbiota. Certain microbes were associated with genotype in multiple ethnicities. Several of the microbe-associated loci were found to be related to immune functions, interact with glutamate and the mucus layer, or be expressed in the gut or brain. Additionally, we found that gut microbes potentially influence cardiometabolic health factors such as BMI, cholesterol, and blood pressure. This provides insight into the relationship of ethnicity and gut microbiota and into the possible causal effects of gut microbes on cardiometabolic traits.
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Affiliation(s)
- Ulrika Boulund
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Diogo M Bastos
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Bart Ferwerda
- Department of Clinical Epidemiology and Biostatistics, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Bert-Jan van den Born
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands; Department of Public and Occupational Health, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Sara-Joan Pinto-Sietsma
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands; Department of Clinical Epidemiology and Biostatistics, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Henrike Galenkamp
- Department of Public and Occupational Health, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Evgeni Levin
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands; HorAIzon BV, 2645 LT Delfgauw, the Netherlands
| | - Albert K Groen
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Aeilko H Zwinderman
- Department of Clinical Epidemiology and Biostatistics, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands
| | - Max Nieuwdorp
- Department of Internal and Vascular Medicine, Amsterdam University Medical Centers, location AMC, 1105 AZ Amsterdam, the Netherlands.
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23
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Wood OWG, Yeung JHY, Faull RLM, Kwakowsky A. EAAT2 as a therapeutic research target in Alzheimer's disease: A systematic review. Front Neurosci 2022; 16:952096. [PMID: 36033606 PMCID: PMC9399514 DOI: 10.3389/fnins.2022.952096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Accepted: 07/14/2022] [Indexed: 11/23/2022] Open
Abstract
Glutamate is the main excitatory neurotransmitter in the human central nervous system, responsible for a wide variety of normal physiological processes. Glutamatergic metabolism and its sequestration are tightly regulated in the normal human brain, and it has been demonstrated that dysregulation of the glutamatergic system can have wide-ranging effects both in acute brain injury and neurodegenerative diseases. The excitatory amino acid transporter 2 (EAAT2) is the dominant glutamatergic transporter in the human brain, responsible for efficient removal of glutamate from the synaptic cleft for recycling within glial cells. As such, it has a key role in maintaining excitatory-inhibitory homeostasis. Animal studies have demonstrated dysregulation or alterations of EAAT2 expression can have implications in neurodegenerative disorders. Despite extensive research into glutamatergic alterations in AD mouse models, there is a lack of studies examining the expression of EAAT2 within the AD human brain. In this systematic review, 29 articles were identified that either analyzed EAAT2 expression in the AD human brain or used a human-derived cell culture. Studies were inconclusive as to whether EAAT2 was upregulated or downregulated in AD. However, changes in localization and correlation between EAAT2 expression and symptomatology was noted. These findings implicate EAAT2 alterations as a key process in AD progression and highlight the need for further research into the characterization of EAAT2 processes in normal physiology and disease in human tissue and to identify compounds that can act as EAAT2 neuromodulators.
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Affiliation(s)
- Oliver W. G. Wood
- Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | - Jason H. Y. Yeung
- Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | - Richard L. M. Faull
- Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, Centre for Brain Research, University of Auckland, Auckland, New Zealand
| | - Andrea Kwakowsky
- Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, Centre for Brain Research, University of Auckland, Auckland, New Zealand
- Pharmacology and Therapeutics, Galway Neuroscience Centre, School of Medicine, Ollscoil na Gaillimhe – University of Galway, Galway, Ireland
- *Correspondence: Andrea Kwakowsky
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24
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Shen Z, Xiang M, Chen C, Ding F, Wang Y, Shang C, Xin L, Zhang Y, Cui X. Glutamate excitotoxicity: Potential therapeutic target for ischemic stroke. Biomed Pharmacother 2022; 151:113125. [PMID: 35609367 DOI: 10.1016/j.biopha.2022.113125] [Citation(s) in RCA: 44] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/01/2022] [Accepted: 05/13/2022] [Indexed: 11/29/2022] Open
Abstract
Glutamate-mediated excitotoxicity is an important mechanism leading to post ischemic stroke damage. After acute stroke, the sudden reduction in cerebral blood flow is most initially followed by ion transport protein dysfunction and disruption of ion homeostasis, which in turn leads to impaired glutamate release, reuptake, and excessive N-methyl-D-aspartate receptor (NMDAR) activation, promoting neuronal death. Despite extensive evidence from preclinical studies suggesting that excessive NMDAR stimulation during ischemic stroke is a central step in post-stroke damage, NMDAR blockers have failed to translate into clinical stroke treatment. Current treatment options for stroke are very limited, and there is therefore a great need to develop new targets for neuroprotective therapeutic agents in ischemic stroke to extend the therapeutic time window. In this review, we highlight recent findings on glutamate release, reuptake mechanisms, NMDAR and its downstream cellular signaling pathways in post-ischemic stroke damage, and review the pathological changes in each link to help develop viable new therapeutic targets. We then also summarize potential neuroprotective drugs and therapeutic approaches for these new targets in the treatment of ischemic stroke.
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Affiliation(s)
- Zihuan Shen
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Mi Xiang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China
| | - Chen Chen
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China
| | - Fan Ding
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Yuling Wang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Chang Shang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China; Clinical Medical School, Beijing University of Traditional Chinese Medicine, Beijing 100029, China
| | - Laiyun Xin
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China
| | - Yang Zhang
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China.
| | - Xiangning Cui
- Department of Cardiovascular, Guang'anmen Hospital, China Academy of Chinese Medical Sciences, Beijing 100053, China.
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25
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Piepgras J, Rohrbeck A, Just I, Bittner S, Ahnert-Hilger G, Höltje M. Enhancement of Phosphorylation and Transport Activity of the Neuronal Glutamate Transporter Excitatory Amino Acid Transporter 3 by C3bot and a 26mer C3bot Peptide. Front Cell Neurosci 2022; 16:860823. [PMID: 35783090 PMCID: PMC9240211 DOI: 10.3389/fncel.2022.860823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2022] [Accepted: 05/16/2022] [Indexed: 11/13/2022] Open
Abstract
In primary murine hippocampal neurons we investigated the regulation of EAAT3-mediated glutamate transport by the Clostridium botulinum C3 transferase C3bot and a 26mer peptide derived from full length protein. Incubation with either enzyme-competent C3bot or enzyme-deficient C3bot156–181 peptide resulted in the upregulation of glutamate uptake by up to 22% compared to untreated cells. A similar enhancement of glutamate transport was also achieved by the classical phorbol-ester-mediated activation of protein kinase C subtypes. Yet comparable, effects elicited by C3 preparations seemed not to rely on PKCα, γ, ε, or ζ activation. Blocking of tyrosine phosphorylation by tyrosine kinase inhibitors prevented the observed effect mediated by C3bot and C3bot 26mer. By using biochemical and molecular biological assays we could rule out that the observed C3bot and C3bot 26mer-mediated effects solely resulted from enhanced transporter expression or translocation to the neuronal surface but was rather mediated by transporter phosphorylation at tyrosine residues that was found to be significantly enhanced following incubation with either full length protein or the 26mer C3 peptide.
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Affiliation(s)
- Johannes Piepgras
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine-Main Neuroscience Network, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Astrid Rohrbeck
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
| | - Ingo Just
- Institute of Toxicology, Hannover Medical School, Hanover, Germany
| | - Stefan Bittner
- Department of Neurology, Focus Program Translational Neuroscience and Immunotherapy, Rhine-Main Neuroscience Network, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Gudrun Ahnert-Hilger
- Department of Neurobiology, Max Planck Institute for Biophysical Chemistry, University of Göttingen, Göttingen, Germany
| | - Markus Höltje
- Institut für Integrative Neuroanatomie, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
- *Correspondence: Markus Höltje,
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26
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Chen I, Wu Q, Font J, Ryan RM. The twisting elevator mechanism of glutamate transporters reveals the structural basis for the dual transport-channel functions. Curr Opin Struct Biol 2022; 75:102405. [PMID: 35709614 DOI: 10.1016/j.sbi.2022.102405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/10/2022] [Accepted: 05/12/2022] [Indexed: 11/16/2022]
Abstract
Glutamate transporters facilitate the removal of this excitatory neurotransmitter from the synapse. Increasing evidence indicates that this process is linked to intrinsic chloride channel activity that is thermodynamically uncoupled from substrate transport. A recent cryo-EM structure of GltPh - an archaeal homolog of the glutamate transporters - in an open channel state has shed light on the structural basis for channel opening formed at the interface of two domains within the transporter which is gated by two clusters of hydrophobic residues. These transporters cycle through several conformational states during the transport process, including the chloride conducting state, which appears to be stabilised by protein-membrane interactions and membrane deformation. Several point mutations that perturb the chloride conductance can have detrimental effects and are linked to the pathogenesis of the neurological disorder, episodic ataxia type 6.
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Affiliation(s)
- Ichia Chen
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Qianyi Wu
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Josep Font
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia.
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27
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Mesnard CS, Barta CL, Sladek AL, Zenisek D, Thoreson WB. Eliminating Synaptic Ribbons from Rods and Cones Halves the Releasable Vesicle Pool and Slows Down Replenishment. Int J Mol Sci 2022; 23:ijms23126429. [PMID: 35742873 PMCID: PMC9223732 DOI: 10.3390/ijms23126429] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 06/03/2022] [Accepted: 06/05/2022] [Indexed: 01/25/2023] Open
Abstract
Glutamate release from rod and cone photoreceptor cells involves presynaptic ribbons composed largely of the protein RIBEYE. To examine roles of ribbons in rods and cones, we studied mice in which GCamP3 replaced the B-domain of RIBEYE. We discovered that ribbons were absent from rods and cones of both knock-in mice possessing GCamP3 and conditional RIBEYE knockout mice. The mice lacking ribbons showed reduced temporal resolution and contrast sensitivity assessed with optomotor reflexes. ERG recordings showed 50% reduction in scotopic and photopic b-waves. The readily releasable pool (RRP) of vesicles in rods and cones measured using glutamate transporter anion currents (IA(glu)) was also halved. We also studied the release from cones by stimulating them optogenetically with ChannelRhodopsin2 (ChR2) while recording postsynaptic currents in horizontal cells. Recovery of the release from paired pulse depression was twofold slower in the rods and cones lacking ribbons. The release from rods at -40 mV in darkness involves regularly spaced multivesicular fusion events. While the regular pattern of release remained in the rods lacking ribbons, the number of vesicles comprising each multivesicular event was halved. Our results support conclusions that synaptic ribbons in rods and cones expand the RRP, speed up vesicle replenishment, and augment some forms of multivesicular release. Slower replenishment and a smaller RRP in photoreceptors lacking ribbons may contribute to diminished temporal frequency responses and weaker contrast sensitivity.
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Affiliation(s)
- Chris S. Mesnard
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
| | - Cody L. Barta
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
| | - Asia L. Sladek
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
| | - David Zenisek
- Department of Cellular and Molecular Physiology, Yale University, New Haven, CT 06510, USA;
| | - Wallace B. Thoreson
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, University of Nebraska Medical Center, Omaha, NE 68198, USA; (C.S.M.); (C.L.B.); (A.L.S.)
- Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198, USA
- Correspondence: ; Tel.: +1-402-559-4076
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28
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Sijben HJ, Dall’ Acqua L, Liu R, Jarret A, Christodoulaki E, Onstein S, Wolf G, Verburgt SJ, Le Dévédec SE, Wiedmer T, Superti-Furga G, IJzerman AP, Heitman LH. Impedance-Based Phenotypic Readout of Transporter Function: A Case for Glutamate Transporters. Front Pharmacol 2022; 13:872335. [PMID: 35677430 PMCID: PMC9169222 DOI: 10.3389/fphar.2022.872335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 03/29/2022] [Indexed: 11/18/2022] Open
Abstract
Excitatory amino acid transporters (EAAT/SLC1) mediate Na+-dependent uptake of extracellular glutamate and are potential drug targets for neurological disorders. Conventional methods to assess glutamate transport in vitro are based on radiolabels, fluorescent dyes or electrophysiology, which potentially compromise the cell’s physiology and are generally less suited for primary drug screens. Here, we describe a novel label-free method to assess human EAAT function in living cells, i.e., without the use of chemical modifications to the substrate or cellular environment. In adherent HEK293 cells overexpressing EAAT1, stimulation with glutamate or aspartate induced cell spreading, which was detected in real-time using an impedance-based biosensor. This change in cell morphology was prevented in the presence of the Na+/K+-ATPase inhibitor ouabain and EAAT inhibitors, which suggests the substrate-induced response was ion-dependent and transporter-specific. A mechanistic explanation for the phenotypic response was substantiated by actin cytoskeleton remodeling and changes in the intracellular levels of the osmolyte taurine, which suggests that the response involves cell swelling. In addition, substrate-induced cellular responses were observed for cells expressing other EAAT subtypes, as well as in a breast cancer cell line (MDA-MB-468) with endogenous EAAT1 expression. These findings allowed the development of a label-free high-throughput screening assay, which could be beneficial in early drug discovery for EAATs and holds potential for the study of other transport proteins that modulate cell shape.
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Affiliation(s)
- Hubert J. Sijben
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Laura Dall’ Acqua
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Rongfang Liu
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Abigail Jarret
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Eirini Christodoulaki
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Svenja Onstein
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Gernot Wolf
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Simone J. Verburgt
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Sylvia E. Le Dévédec
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Tabea Wiedmer
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Giulio Superti-Furga
- CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences, Medical University of Vienna, Vienna, Austria
| | - Adriaan P. IJzerman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
| | - Laura H. Heitman
- Division of Drug Discovery and Safety, Leiden Academic Centre for Drug Research, Leiden University, Leiden, Netherlands
- Oncode Institute, Leiden, Netherlands
- *Correspondence: Laura H. Heitman,
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29
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Tang FS, Yuan HL, Liu JB, Zhang G, Chen SY, Ke JB. Glutamate Transporters EAAT2 and EAAT5 Differentially Shape Synaptic Transmission from Rod Bipolar Cell Terminals. eNeuro 2022; 9:ENEURO.0074-22.2022. [PMID: 35523583 PMCID: PMC9121915 DOI: 10.1523/eneuro.0074-22.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/26/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) control visual signal transmission in the retina by rapidly removing glutamate released from photoreceptors and bipolar cells (BCs). Although it has been reported that EAAT2 and EAAT5 are expressed at presynaptic terminals of photoreceptors and some BCs in mammals, the distinct functions of these two glutamate transporters in retinal synaptic transmission, especially at a single synapse, remain elusive. In this study, we found that EAAT2 was expressed in all BC types while coexisting with EAAT5 in rod bipolar (RB) cells and several types of cone BCs from mice of either sex. Our immunohistochemical study, together with a recently published literature (Gehlen et al., 2021), showed that EAAT2 and EAAT5 were both located in RB axon terminals near release sites. Optogenetic, electrophysiological and pharmacological analyses, however, demonstrated that EAAT2 and EAAT5 regulated neurotransmission at RB→AII amacrine cell synapses in significantly different ways: EAAT5 dramatically affected both the peak amplitude and kinetics of postsynaptic responses in AIIs, whereas EAAT2 had either relatively small or opposite effects. By contrast, blockade of EAAT1/GLAST, which was exclusively expressed in Müller cells, showed no obvious effect on AII responses, indicating that glutamate uptake by Müller cells did not influence synaptic transmission from RB terminals. Furthermore, we found that temporal resolution at RB→AII synapses was reduced substantially by blockade of EAAT5 but not EAAT2. Taken together, our work reveals the distinct functions of EAAT2 and EAAT5 in signal transmission at RB ribbon synapses.
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Affiliation(s)
| | | | | | | | | | - Jiang-Bin Ke
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou 510060, China
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30
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Hann Yih T, Abd Ghapor AA, Agarwal R, Razali N, Iezhitsa I, Mohd Ismail N. Effect of trans-resveratrol on glutamate clearance and visual behaviour in rats with glutamate induced retinal injury. Exp Eye Res 2022; 220:109104. [DOI: 10.1016/j.exer.2022.109104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 04/20/2022] [Accepted: 04/27/2022] [Indexed: 11/04/2022]
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31
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Boccuni I, Fairless R. Retinal Glutamate Neurotransmission: From Physiology to Pathophysiological Mechanisms of Retinal Ganglion Cell Degeneration. Life (Basel) 2022; 12:638. [PMID: 35629305 PMCID: PMC9147752 DOI: 10.3390/life12050638] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/22/2022] [Accepted: 04/22/2022] [Indexed: 12/12/2022] Open
Abstract
Glutamate neurotransmission and metabolism are finely modulated by the retinal network, where the efficient processing of visual information is shaped by the differential distribution and composition of glutamate receptors and transporters. However, disturbances in glutamate homeostasis can result in glutamate excitotoxicity, a major initiating factor of common neurodegenerative diseases. Within the retina, glutamate excitotoxicity can impair visual transmission by initiating degeneration of neuronal populations, including retinal ganglion cells (RGCs). The vulnerability of RGCs is observed not just as a result of retinal diseases but has also been ascribed to other common neurodegenerative and peripheral diseases. In this review, we describe the vulnerability of RGCs to glutamate excitotoxicity and the contribution of different glutamate receptors and transporters to this. In particular, we focus on the N-methyl-d-aspartate (NMDA) receptor as the major effector of glutamate-induced mechanisms of neurodegeneration, including impairment of calcium homeostasis, changes in gene expression and signalling, and mitochondrial dysfunction, as well as the role of endoplasmic reticular stress. Due to recent developments in the search for modulators of NMDA receptor signalling, novel neuroprotective strategies may be on the horizon.
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Affiliation(s)
- Isabella Boccuni
- Institute for Physiology and Pathophysiology, Heidelberg University, 69120 Heidelberg, Germany
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany;
| | - Richard Fairless
- Department of Neurology, University Clinic Heidelberg, 69120 Heidelberg, Germany;
- Clinical Cooperation Unit (CCU) Neurooncology, German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
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32
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Wu Q, Akhter A, Pant S, Cho E, Zhu JX, Garner AR, Ohyama T, Tajkhorshid E, van Meyel DJ, Ryan RM. Ataxia-linked SLC1A3 mutations alter EAAT1 chloride channel activity and glial regulation of CNS function. J Clin Invest 2022; 132:154891. [PMID: 35167492 PMCID: PMC8970671 DOI: 10.1172/jci154891] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/08/2022] [Indexed: 11/17/2022] Open
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system (CNS). Excitatory Amino Acid Transporters (EAATs) regulate extracellular glutamate by transporting it into cells, mostly glia, to terminate neurotransmission and to avoid neurotoxicity. EAATs are also chloride (Cl-) channels, but the physiological role of Cl- conductance through EAATs is poorly understood. Mutations of human EAAT1 (hEAAT1) have been identified in patients with episodic ataxia type 6 (EA6). One mutation showed increased Cl- channel activity and decreased glutamate transport, but the relative contributions of each function of hEAAT1 to mechanisms underlying the pathology of EA6 remain unclear. Here we investigated the effects of five additional EA6-related mutations on hEAAT1 function in Xenopus laevis oocytes, and on CNS function in a Drosophila melanogaster model of locomotor behavior. Our results indicate that mutations resulting in decreased hEAAT1 Cl- channel activity but with functional glutamate transport can also contribute to the pathology of EA6, highlighting the importance of Cl- homeostasis in glial cells for proper CNS function. We also identified a novel mechanism involving an ectopic sodium (Na+) leak conductance in glial cells. Together, these results strongly support the idea that EA6 is primarily an ion channelopathy of CNS glia.
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Affiliation(s)
- Qianyi Wu
- School of Medical Sciences, University of Sydney, Sydney, Australia
| | - Azman Akhter
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Shashank Pant
- Theoretical and Computational Biophysics Group, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Eunjoo Cho
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Jin Xin Zhu
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | | | - Tomoko Ohyama
- Department of Biology, McGill University, Montreal, Canada
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, University of Illinois at Urbana-Champaign, Urbana, United States of America
| | - Donald J van Meyel
- Department of Neurology and Neurosurgery, McGill University, Montreal, Canada
| | - Renae M Ryan
- School of Medical Sciences, University of Sydney, Sydney, Australia
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33
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Functional and Kinetic Comparison of Alanine Cysteine Serine Transporters ASCT1 and ASCT2. Biomolecules 2022; 12:biom12010113. [PMID: 35053261 PMCID: PMC8773628 DOI: 10.3390/biom12010113] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/05/2022] [Accepted: 01/07/2022] [Indexed: 02/01/2023] Open
Abstract
Neutral amino acid transporters ASCT1 and ASCT2 are two SLC1 (solute carrier 1) family subtypes, which are specific for neutral amino acids. The other members of the SLC1 family are acidic amino acid transporters (EAATs 1–5). While the functional similarities and differences between the EAATs have been well studied, less is known about how the subtypes ASCT1 and 2 differ in kinetics and function. Here, by performing comprehensive electrophysiological analysis, we identified similarities and differences between these subtypes, as well as novel functional properties, such as apparent substrate affinities of the inward-facing conformation (in the range of 70 μM for L-serine as the substrate). Key findings were: ASCT1 has a higher apparent affinity for Na+, as well as a larger [Na+] dependence of substrate affinity compared to ASCT2. However, the general sequential Na+/substrate binding mechanism with at least one Na+ binding first, followed by amino acid substrate, followed by at least one more Na+ ion, appears to be conserved between the two subtypes. In addition, the first Na+ binding step, presumably to the Na3 site, occurs with high apparent affinity (<1 mM) in both transporters. In addition, ASCT1 and 2 show different substrate selectivities, where ASCT1 does not respond to extracellular glutamine. Finally, in both transporters, we measured rapid, capacitive charge movements upon application and removal of amino acid, due to rearrangement of the translocation equilibrium. This charge movement decays rapidly, with a time constant of 4–5 ms and recovers with a time constant in the 15 ms range after substrate removal. This places a lower limit on the turnover rate of amino acid exchange by these two transporters of 60–80 s−1.
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34
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Kovermann P, Engels M, Müller F, Fahlke C. Cellular Physiology and Pathophysiology of EAAT Anion Channels. Front Cell Neurosci 2022; 15:815279. [PMID: 35087380 PMCID: PMC8787812 DOI: 10.3389/fncel.2021.815279] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Accepted: 12/13/2021] [Indexed: 11/17/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) optimize the temporal resolution and energy demand of mammalian excitatory synapses by quickly removing glutamate from the synaptic cleft into surrounding neuronal and glial cells and ensuring low resting glutamate concentrations. In addition to secondary active glutamate transport, EAATs also function as anion channels. The channel function of these transporters is conserved in all homologs ranging from archaebacteria to mammals; however, its physiological roles are insufficiently understood. There are five human EAATs, which differ in their glutamate transport rates. Until recently the high-capacity transporters EAAT1, EAAT2, and EAAT3 were believed to conduct only negligible anion currents, with no obvious function in cell physiology. In contrast, the low-capacity glutamate transporters EAAT4 and EAAT5 are thought to regulate neuronal signaling as glutamate-gated channels. In recent years, new experimental approaches and novel animal models, together with the discovery of a human genetic disease caused by gain-of-function mutations in EAAT anion channels have enabled identification of the first physiological and pathophysiological roles of EAAT anion channels.
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35
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Rapid Regulation of Glutamate Transport: Where Do We Go from Here? Neurochem Res 2022; 47:61-84. [PMID: 33893911 PMCID: PMC8542062 DOI: 10.1007/s11064-021-03329-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 04/08/2021] [Accepted: 04/13/2021] [Indexed: 01/03/2023]
Abstract
Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system (CNS). A family of five Na+-dependent transporters maintain low levels of extracellular glutamate and shape excitatory signaling. Shortly after the research group of the person being honored in this special issue (Dr. Baruch Kanner) cloned one of these transporters, his group and several others showed that their activity can be acutely (within minutes to hours) regulated. Since this time, several different signals and post-translational modifications have been implicated in the regulation of these transporters. In this review, we will provide a brief introduction to the distribution and function of this family of glutamate transporters. This will be followed by a discussion of the signals that rapidly control the activity and/or localization of these transporters, including protein kinase C, ubiquitination, glutamate transporter substrates, nitrosylation, and palmitoylation. We also include the results of our attempts to define the role of palmitoylation in the regulation of GLT-1 in crude synaptosomes. In some cases, the mechanisms have been fairly well-defined, but in others, the mechanisms are not understood. In several cases, contradictory phenomena have been observed by more than one group; we describe these studies with the goal of identifying the opportunities for advancing the field. Abnormal glutamatergic signaling has been implicated in a wide variety of psychiatric and neurologic disorders. Although recent studies have begun to link regulation of glutamate transporters to the pathogenesis of these disorders, it will be difficult to determine how regulation influences signaling or pathophysiology of glutamate without a better understanding of the mechanisms involved.
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36
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Yeung JHY, Palpagama TH, Wood OWG, Turner C, Waldvogel HJ, Faull RLM, Kwakowsky A. EAAT2 Expression in the Hippocampus, Subiculum, Entorhinal Cortex and Superior Temporal Gyrus in Alzheimer's Disease. Front Cell Neurosci 2021; 15:702824. [PMID: 34588956 PMCID: PMC8475191 DOI: 10.3389/fncel.2021.702824] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 08/23/2021] [Indexed: 11/24/2022] Open
Abstract
Alzheimer’s disease (AD) is a neuropathological disorder characterized by the presence and accumulation of amyloid-beta plaques and neurofibrillary tangles. Glutamate dysregulation and the concept of glutamatergic excitotoxicity have been frequently described in the pathogenesis of a variety of neurodegenerative disorders and are postulated to play a major role in the progression of AD. In particular, alterations in homeostatic mechanisms, such as glutamate uptake, have been implicated in AD. An association with excitatory amino acid transporter 2 (EAAT2), the main glutamate uptake transporter, dysfunction has also been described. Several animal and few human studies examined EAAT2 expression in multiple brain regions in AD but studies of the hippocampus, the most severely affected brain region, are scarce. Therefore, this study aims to assess alterations in the expression of EAAT2 qualitatively and quantitatively through DAB immunohistochemistry (IHC) and immunofluorescence within the hippocampus, subiculum, entorhinal cortex, and superior temporal gyrus (STG) regions, between human AD and control cases. Although no significant EAAT2 density changes were observed between control and AD cases, there appeared to be increased transporter expression most likely localized to fine astrocytic branches in the neuropil as seen on both DAB IHC and immunofluorescence. Therefore, individual astrocytes are not outlined by EAAT2 staining and are not easily recognizable in the CA1–3 and dentate gyrus regions of AD cases, but the altered expression patterns observed between AD and control hippocampal cases could indicate alterations in glutamate recycling and potentially disturbed glutamatergic homeostasis. In conclusion, no significant EAAT2 density changes were found between control and AD cases, but the observed spatial differences in transporter expression and their functional significance will have to be further explored.
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Affiliation(s)
- Jason H Y Yeung
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Thulani H Palpagama
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Oliver W G Wood
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Clinton Turner
- Department of Anatomical Pathology, LabPlus, Auckland City Hospital, Auckland, New Zealand
| | - Henry J Waldvogel
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Richard L M Faull
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Andrea Kwakowsky
- Centre for Brain Research, Department of Anatomy and Medical Imaging, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
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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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38
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Stehantsev P, Stetsenko A, Nemchinova M, Aduri NG, Marrink SJ, Gati C, Guskov A. A structural view onto disease-linked mutations in the human neutral amino acid exchanger ASCT1. Comput Struct Biotechnol J 2021; 19:5246-5254. [PMID: 34630942 PMCID: PMC8479201 DOI: 10.1016/j.csbj.2021.09.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/14/2021] [Accepted: 09/14/2021] [Indexed: 01/30/2023] Open
Abstract
The ASCT1 transporter of the SLC1 family is largely involved in equilibration of neutral amino acids' pools across the plasma membrane and plays a prominent role in the transport of both L- and D-isomers of serine, essential for the normal functioning of the central nervous system in mammals. A number of mutations in ASCT1 (E256K, G381R, R457W) have been linked to severe neurodevelopmental disorders, however in the absence of ASCT1 structure it is hard to understand their impact on substrate transport. To ameliorate that we have determined a cryo-EM structure of human ASCT1 at 4.2 Å resolution and performed functional transport assays and molecular dynamics simulations, which revealed that given mutations lead to the diminished transport capability of ASCT1 caused by instability of transporter and impeded transport cycle.
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Affiliation(s)
- Pavlo Stehantsev
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Artem Stetsenko
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Mariia Nemchinova
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Nanda Gowtham Aduri
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA, USA
| | - Siewert J. Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
| | - Cornelius Gati
- Department of Biological Sciences, Bridge Institute, USC Michelson Center for Convergent Bioscience, University of Southern California, Los Angeles, CA, USA
| | - Albert Guskov
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
- Moscow Institute of Physics and Technology, Dolgoprudny, Russia
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Hays CL, Sladek AL, Thoreson WB. Resting and stimulated mouse rod photoreceptors show distinct patterns of vesicle release at ribbon synapses. J Gen Physiol 2021; 152:211528. [PMID: 33175961 PMCID: PMC7664508 DOI: 10.1085/jgp.202012716] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 10/01/2020] [Accepted: 10/19/2020] [Indexed: 01/04/2023] Open
Abstract
The vertebrate visual system can detect and transmit signals from single photons. To understand how single-photon responses are transmitted, we characterized voltage-dependent properties of glutamate release in mouse rods. We measured presynaptic glutamate transporter anion current and found that rates of synaptic vesicle release increased with voltage-dependent Ca2+ current. Ca2+ influx and release rate also rose with temperature, attaining a rate of ∼11 vesicles/s/ribbon at -40 mV (35°C). By contrast, spontaneous release events at hyperpolarized potentials (-60 to -70 mV) were univesicular and occurred at random intervals. However, when rods were voltage clamped at -40 mV for many seconds to simulate maintained darkness, release occurred in coordinated bursts of 17 ± 7 quanta (mean ± SD; n = 22). Like fast release evoked by brief depolarizing stimuli, these bursts involved vesicles in the readily releasable pool of vesicles and were triggered by the opening of nearby ribbon-associated Ca2+ channels. Spontaneous release rates were elevated and bursts were absent after genetic elimination of the Ca2+ sensor synaptotagmin 1 (Syt1). This study shows that at the resting potential in darkness, rods release glutamate-filled vesicles from a pool at the base of synaptic ribbons at low rates but in Syt1-dependent bursts. The absence of bursting in cones suggests that this behavior may have a role in transmitting scotopic responses.
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Affiliation(s)
- Cassandra L Hays
- Cellular and Integrative Physiology, College of Medicine, University of Nebraska Medical Center, Omaha, NE.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, NE
| | - Asia L Sladek
- Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center, Omaha, NE
| | - Wallace B Thoreson
- Pharmacology and Experimental Neuroscience, College of Medicine, University of Nebraska Medical Center, Omaha, NE.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, NE
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Nakamoto M, Uchino T, Koshimizu E, Kuchiishi Y, Sekiguchi R, Wang L, Sudo R, Endo M, Guiguen Y, Schartl M, Postlethwait JH, Sakamoto T. A Y-linked anti-Müllerian hormone type-II receptor is the sex-determining gene in ayu, Plecoglossus altivelis. PLoS Genet 2021; 17:e1009705. [PMID: 34437539 PMCID: PMC8389408 DOI: 10.1371/journal.pgen.1009705] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 07/09/2021] [Indexed: 11/19/2022] Open
Abstract
Whole-genome duplication and genome compaction are thought to have played important roles in teleost fish evolution. Ayu (or sweetfish), Plecoglossus altivelis, belongs to the superorder Stomiati, order Osmeriformes. Stomiati is phylogenetically classified as sister taxa of Neoteleostei. Thus, ayu holds an important position in the fish tree of life. Although ayu is economically important for the food industry and recreational fishing in Japan, few genomic resources are available for this species. To address this problem, we produced a draft genome sequence of ayu by whole-genome shotgun sequencing and constructed linkage maps using a genotyping-by-sequencing approach. Syntenic analyses of ayu and other teleost fish provided information about chromosomal rearrangements during the divergence of Stomiati, Protacanthopterygii and Neoteleostei. The size of the ayu genome indicates that genome compaction occurred after the divergence of the family Osmeridae. Ayu has an XX/XY sex-determination system for which we identified sex-associated loci by a genome-wide association study by genotyping-by-sequencing and whole-genome resequencing using wild populations. Genome-wide association mapping using wild ayu populations revealed three sex-linked scaffolds (total, 2.03 Mb). Comparison of whole-genome resequencing mapping coverage between males and females identified male-specific regions in sex-linked scaffolds. A duplicate copy of the anti-Müllerian hormone type-II receptor gene (amhr2bY) was found within these male-specific regions, distinct from the autosomal copy of amhr2. Expression of the Y-linked amhr2 gene was male-specific in sox9b-positive somatic cells surrounding germ cells in undifferentiated gonads, whereas autosomal amhr2 transcripts were detected in somatic cells in sexually undifferentiated gonads of both genetic males and females. Loss-of-function mutation for amhr2bY induced male to female sex reversal. Taken together with the known role of Amh and Amhr2 in sex differentiation, these results indicate that the paralog of amhr2 on the ayu Y chromosome determines genetic sex, and the male-specific amh-amhr2 pathway is critical for testicular differentiation in ayu.
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Affiliation(s)
- Masatoshi Nakamoto
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Tsubasa Uchino
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Eriko Koshimizu
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
- Department of Human Genetics, Yokohama City University, Graduate School of Medicine, Yokohama, Japan
| | - Yudai Kuchiishi
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Ryota Sekiguchi
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Liu Wang
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Ryusuke Sudo
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | - Masato Endo
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
| | | | - Manfred Schartl
- University of Wuerzburg, Developmental Biochemistry, Biocenter, Würzburg, Germany
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, United States of America
| | - John H. Postlethwait
- Institute of Neuroscience, University of Oregon, Eugene, Oregon, United States of America
| | - Takashi Sakamoto
- Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Tokyo, Japan
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Katane M, Matsuda S, Saitoh Y, Miyamoto T, Sekine M, Sakai-Kato K, Homma H. Glyoxylate reductase/hydroxypyruvate reductase regulates the free d-aspartate level in mammalian cells. J Cell Biochem 2021; 122:1639-1652. [PMID: 34289161 DOI: 10.1002/jcb.30110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 06/30/2021] [Accepted: 07/09/2021] [Indexed: 12/16/2022]
Abstract
Multiple d-amino acids are present in mammalian cells, and these compounds have distinctive physiological functions. Among the free d-amino acids identified in mammals, d-aspartate plays critical roles in the neuroendocrine and endocrine systems, as well as in the central nervous system. Mammalian cells have the molecular apparatus necessary to take up, degrade, synthesize, and release d-aspartate. In particular, d-aspartate is degraded by d-aspartate oxidase (DDO), a peroxisome-localized enzyme that catalyzes the oxidative deamination of d-aspartate to generate oxaloacetate, hydrogen peroxide, and ammonia. However, little is known about the molecular mechanisms underlying d-aspartate homeostasis in cells. In this study, we established a cell line that overexpresses cytoplasm-localized DDO; this cell line cannot survive in the presence of high concentrations of d-aspartate, presumably because high levels of toxic hydrogen peroxide are produced by metabolism of abundant d-aspartate by DDO in the cytoplasm, where hydrogen peroxide cannot be removed due to the absence of catalase. Next, we transfected these cells with a complementary DNA library derived from the human brain and screened for clones that affected d-aspartate metabolism and improved cell survival, even when the cells were challenged with high concentrations of d-aspartate. The screen identified a clone of glyoxylate reductase/hydroxypyruvate reductase (GRHPR). Moreover, the GRHPR metabolites glyoxylate and hydroxypyruvate inhibited the enzymatic activity of DDO. Furthermore, we evaluated the effects of GRHPR and peroxisome-localized DDO on d- and l-aspartate levels in cultured mammalian cells. Our findings show that GRHPR contributes to the homeostasis of these amino acids in mammalian cells.
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Affiliation(s)
- Masumi Katane
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Satsuki Matsuda
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Yasuaki Saitoh
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Tetsuya Miyamoto
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Masae Sekine
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Kumiko Sakai-Kato
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
| | - Hiroshi Homma
- Laboratory of Analytical Chemistry, Graduate School of Pharmaceutical Sciences, Kitasato University, Minato-ku, Tokyo, Japan
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42
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Andersen JV, Markussen KH, Jakobsen E, Schousboe A, Waagepetersen HS, Rosenberg PA, Aldana BI. Glutamate metabolism and recycling at the excitatory synapse in health and neurodegeneration. Neuropharmacology 2021; 196:108719. [PMID: 34273389 DOI: 10.1016/j.neuropharm.2021.108719] [Citation(s) in RCA: 120] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 07/01/2021] [Accepted: 07/13/2021] [Indexed: 02/08/2023]
Abstract
Glutamate is the primary excitatory neurotransmitter of the brain. Cellular homeostasis of glutamate is of paramount importance for normal brain function and relies on an intricate metabolic collaboration between neurons and astrocytes. Glutamate is extensively recycled between neurons and astrocytes in a process known as the glutamate-glutamine cycle. The recycling of glutamate is closely linked to brain energy metabolism and is essential to sustain glutamatergic neurotransmission. However, a considerable amount of glutamate is also metabolized and serves as a metabolic hub connecting glucose and amino acid metabolism in both neurons and astrocytes. Disruptions in glutamate clearance, leading to neuronal overstimulation and excitotoxicity, have been implicated in several neurodegenerative diseases. Furthermore, the link between brain energy homeostasis and glutamate metabolism is gaining attention in several neurological conditions. In this review, we provide an overview of the dynamics of synaptic glutamate homeostasis and the underlying metabolic processes with a cellular focus on neurons and astrocytes. In particular, we review the recently discovered role of neuronal glutamate uptake in synaptic glutamate homeostasis and discuss current advances in cellular glutamate metabolism in the context of Alzheimer's disease and Huntington's disease. Understanding the intricate regulation of glutamate-dependent metabolic processes at the synapse will not only increase our insight into the metabolic mechanisms of glutamate homeostasis, but may reveal new metabolic targets to ameliorate neurodegeneration.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
| | - Kia H Markussen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, KY, USA
| | - Emil Jakobsen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Helle S Waagepetersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark
| | - Paul A Rosenberg
- Department of Neurology and the F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA, USA; Program in Neuroscience, Harvard Medical School, Boston, MA, USA
| | - Blanca I Aldana
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark.
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Li X, Wang W, Yan J, Zeng F. Glutamic Acid Transporters: Targets for Neuroprotective Therapies in Parkinson's Disease. Front Neurosci 2021; 15:678154. [PMID: 34220434 PMCID: PMC8242205 DOI: 10.3389/fnins.2021.678154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 05/07/2021] [Indexed: 12/21/2022] Open
Abstract
Parkinson's disease (PD) is a common neurodegenerative disease in middle-aged and elderly individuals. At present, no effective drug has been developed to treat PD. Although a variety of drugs exist for the symptomatic treatment of PD, they all have strong side effects. Most studies on PD mainly focus on dopaminergic neurons. This review highlights the function of glutamic acid transporters (GLTs), including excitatory amino acid transporters (EAATs) and vesicular glutamate transporters (VGLUTs), during the development of PD. In addition, using bioinformatics, we compared the expression of different types of glutamate transporter genes in the cingulate gyrus of PD patients and healthy controls. More importantly, we suggest that the functional roles of glutamate transporters may prove beneficial in the treatment of PD. In summary, VGLUTs and EAATs may be potential targets in the treatment of PD. VGLUTs and EAATs can be used as clinical drug targets to achieve better efficacy. Through this review article, we hope to enable future researchers to improve the condition of PD patients.
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Affiliation(s)
- Xiang Li
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Southwest Medical University, Luzhou, China
| | - Wenjun Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Southwest Medical University, Luzhou, China.,Institute for Cancer Medicine and School of Basic Medical Sciences, Southwest Medical University, Luzhou, China
| | - Jianghong Yan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Southwest Medical University, Luzhou, China
| | - Fancai Zeng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Science, Southwest Medical University, Luzhou, China
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44
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Rodríguez-Campuzano AG, Ortega A. Glutamate transporters: Critical components of glutamatergic transmission. Neuropharmacology 2021; 192:108602. [PMID: 33991564 DOI: 10.1016/j.neuropharm.2021.108602] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/09/2021] [Accepted: 04/27/2021] [Indexed: 02/06/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the vertebrate central nervous system. Once released, it binds to specific membrane receptors and transporters activating a wide variety of signal transduction cascades, as well as its removal from the synaptic cleft in order to avoid its extracellular accumulation and the overstimulation of extra-synaptic receptors that might result in neuronal death through a process known as excitotoxicity. Although neurodegenerative diseases are heterogenous in clinical phenotypes and genetic etiologies, a fundamental mechanism involved in neuronal degeneration is excitotoxicity. Glutamate homeostasis is critical for brain physiology and Glutamate transporters are key players in maintaining low extracellular Glutamate levels. Therefore, the characterization of Glutamate transporters has been an active area of glutamatergic research for the last 40 years. Transporter activity its regulated at different levels: transcriptional and translational control, transporter protein trafficking and membrane mobility, and through extensive post-translational modifications. The elucidation of these mechanisms has emerged as an important piece to shape our current understanding of glutamate actions in the nervous system.
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Affiliation(s)
- Ada G Rodríguez-Campuzano
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, Ciudad de México, 07000, Mexico
| | - Arturo Ortega
- Departamento de Toxicología, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado Postal 14-740, Ciudad de México, 07000, Mexico.
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Lukasiewcz PD, Bligard GW, DeBrecht JD. EAAT5 Glutamate Transporter-Mediated Inhibition in the Vertebrate Retina. Front Cell Neurosci 2021; 15:662859. [PMID: 34025361 PMCID: PMC8134652 DOI: 10.3389/fncel.2021.662859] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 03/19/2021] [Indexed: 12/29/2022] Open
Abstract
Glutamate transporters typically remove glutamate from the synaptic cleft. In addition, all glutamate transporters have a chloride channel, which is opened upon glutamate binding to the transporter. There are five types of glutamate transporter (EAATs 1–5, excitatory amino acid transporters), which have distinct chloride conductances. Some EAATs that have low chloride conductances, remove glutamate from the synaptic cleft most effectively (e.g., EAAT1). By contrast, EAATs that have high chloride conductances, remove glutamate less effectively (e.g., EAAT5). We have studied EAAT5 in the retina. In the retina, light activates a chloride current, mediated by the glutamate activation of EAAT5. EAAT5 is not a significant contributor to lateral inhibition in the retina. Instead, it is the main source of autoinhibition to rod bipolar cells (RBCs). EAAT5-mediated inhibition has a substantial effect on synaptic transmission from RBCs to downstream retinal neurons.
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Affiliation(s)
- Peter D Lukasiewcz
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine in St. Louis, St. Louis, MO, United States.,Department of Neuroscience, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
| | - Gregory W Bligard
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
| | - James D DeBrecht
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine in St. Louis, St. Louis, MO, United States
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Meng X, Zhong J, Zeng C, Yung KKL, Zhang X, Wu X, Qu S. MiR-30a-5p Regulates GLT-1 Function via a PKCα-Mediated Ubiquitin Degradation Pathway in a Mouse Model of Parkinson's Disease. ACS Chem Neurosci 2021; 12:1578-1592. [PMID: 33882234 DOI: 10.1021/acschemneuro.1c00076] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Glutamate excitotoxicity is caused by dysfunctional glutamate transporters and plays an important role in the pathogenesis of Parkinson's disease (PD); however, the mechanisms that underlie the regulation of glutamate transporters in PD are still not fully elucidated. MicroRNAs(miRNA), which are abundant in astrocytes and neurons, have been reported to play key roles in regulating the translation of glutamate-transporter mRNA. In this study, we hypothesized that the miR-30a-5p contributes to the pathogenesis of PD by regulating the ubiquitin-mediated degradation of glutamate transporter 1 (GLT-1). We demonstrated that short-hairpin RNA-mediated knockdown of miR-30a-5p ameliorated motor deficits and pathological changes like astrogliosis and reactive microgliosis in a mouse model of PD (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice). Western blotting and immunofluorescent labeling revealed that miR-30a-5p suppressed the expression and function of GLT-1 in MPTP-treated mice and specifically in astrocytes treated with 1-methyl-4-phenylpyridinium (MPP+) (cell model of PD). Both in vitro and in vivo, we found that miR-30a-5p knockdown promoted glutamate uptake and increased GLT-1 expression by hindering GLT-1 ubiquitination and subsequent degradation in a PKCα-dependent manner. Therefore, we conclude that miR-30a-5p represents a potential therapeutic target for the treatment of PD.
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Affiliation(s)
- Xingjun Meng
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, China
- Central Laboratory and Department of Neurology, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, Guangdong 510515, China
- Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Jianping Zhong
- Department of Neurology, Shunde Hospital of Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
| | - Chong Zeng
- Central Laboratory and Department of Neurology, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
| | - Ken Kin Lam Yung
- Department of Biology, Faculty of Science, Hong Kong Baptist University, Hong Kong, China
| | - Xiuping Zhang
- Teaching Center of Experimental Medicine, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Xiaojuan Wu
- Department of Immunology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong 510515, China
| | - Shaogang Qu
- Department of Neurology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, China
- Central Laboratory and Department of Neurology, Shunde Hospital, Southern Medical University (The First People’s Hospital of Shunde Foshan), Foshan, Guangdong 528300, China
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, Guangdong 510515, China
- Key Laboratory of Mental Health of the Ministry of Education, Southern Medical University, Guangzhou, Guangdong 510515, China
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Danbolt NC, López-Corcuera B, Zhou Y. Reconstitution of GABA, Glycine and Glutamate Transporters. Neurochem Res 2021; 47:85-110. [PMID: 33905037 PMCID: PMC8763731 DOI: 10.1007/s11064-021-03331-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 04/13/2021] [Accepted: 04/15/2021] [Indexed: 10/25/2022]
Abstract
In contrast to water soluble enzymes which can be purified and studied while in solution, studies of solute carrier (transporter) proteins require both that the protein of interest is situated in a phospholipid membrane and that this membrane forms a closed compartment. An additional challenge to the study of transporter proteins has been that the transport depends on the transmembrane electrochemical gradients. Baruch I. Kanner understood this early on and first developed techniques for studying plasma membrane vesicles. This advanced the field in that the experimenter could control the electrochemical gradients. Kanner, however, did not stop there, but started to solubilize the membranes so that the transporter proteins were taken out of their natural environment. In order to study them, Kanner then had to find a way to reconstitute them (reinsert them into phospholipid membranes). The scope of the present review is both to describe the reconstitution method in full detail as that has never been done, and also to reveal the scientific impact that this method has had. Kanner's later work is not reviewed here although that also deserves a review because it too has had a huge impact.
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Affiliation(s)
- Niels Christian Danbolt
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317, Oslo, Norway.
| | - Beatriz López-Corcuera
- Departamento de Biología Molecular, Universidad Autónoma de Madrid, Madrid, Spain.,Centro de Biología Molecular "Severo Ochoa" Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Madrid, Spain.,IdiPAZ, Hospital Universitario La Paz, Madrid, Spain
| | - Yun Zhou
- Neurotransporter Group, Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317, Oslo, Norway
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Thoreson WB. Transmission at rod and cone ribbon synapses in the retina. Pflugers Arch 2021; 473:1469-1491. [PMID: 33779813 DOI: 10.1007/s00424-021-02548-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 02/23/2021] [Accepted: 02/25/2021] [Indexed: 12/29/2022]
Abstract
Light-evoked voltage responses of rod and cone photoreceptor cells in the vertebrate retina must be converted to a train of synaptic vesicle release events for transmission to downstream neurons. This review discusses the processes, proteins, and structures that shape this critical early step in vision, focusing on studies from salamander retina with comparisons to other experimental animals. Many mechanisms are conserved across species. In cones, glutamate release is confined to ribbon release sites although rods are also capable of release at non-ribbon sites. The role of non-ribbon release in rods remains unclear. Release from synaptic ribbons in rods and cones involves at least three vesicle pools: a readily releasable pool (RRP) matching the number of membrane-associated vesicles along the ribbon base, a ribbon reserve pool matching the number of additional vesicles on the ribbon, and an enormous cytoplasmic reserve. Vesicle release increases in parallel with Ca2+ channel activity. While the opening of only a few Ca2+ channels beneath each ribbon can trigger fusion of a single vesicle, sustained release rates in darkness are governed by the rate at which the RRP can be replenished. The number of vacant release sites, their functional status, and the rate of vesicle delivery in turn govern replenishment. Along with an overview of the mechanisms of exocytosis and endocytosis, we consider specific properties of ribbon-associated proteins and pose a number of remaining questions about this first synapse in the visual system.
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Affiliation(s)
- Wallace B Thoreson
- Truhlsen Eye Institute, Departments of Ophthalmology & Visual Sciences and Pharmacology & Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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Hays CL, Sladek AL, Field GD, Thoreson WB. Properties of multivesicular release from mouse rod photoreceptors support transmission of single-photon responses. eLife 2021; 10:67446. [PMID: 33769285 PMCID: PMC8032395 DOI: 10.7554/elife.67446] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 03/20/2021] [Indexed: 01/18/2023] Open
Abstract
Vision under starlight requires rod photoreceptors to transduce and transmit single-photon responses to the visual system. Small single-photon voltage changes must therefore cause detectable reductions in glutamate release. We found that rods achieve this by employing mechanisms that enhance release regularity and its sensitivity to small voltage changes. At the resting membrane potential in darkness, mouse rods exhibit coordinated and regularly timed multivesicular release events, each consisting of ~17 vesicles and occurring two to three times more regularly than predicted by Poisson statistics. Hyperpolarizing rods to mimic the voltage change produced by a single photon abruptly reduced the probability of multivesicular release nearly to zero with a rebound increase at stimulus offset. Simulations of these release dynamics indicate that this regularly timed, multivesicular release promotes transmission of single-photon responses to post-synaptic rod-bipolar cells. Furthermore, the mechanism is efficient, requiring lower overall release rates than uniquantal release governed by Poisson statistics.
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Affiliation(s)
- Cassandra L Hays
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, United States.,Cellular and Integrative Physiology, Omaha, United States
| | - Asia L Sladek
- Pharmacology and Experimental Neuroscience, Omaha, United States
| | - Greg D Field
- Department of Neurobiology, Duke University School of Medicine, Durham, United States
| | - Wallace B Thoreson
- Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, College of Medicine, University of Nebraska Medical Center, Omaha, United States.,Pharmacology and Experimental Neuroscience, Omaha, United States
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50
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Mai D, Chen R, Wang J, Zheng J, Zhang X, Qu S. Critical amino acids in the TM2 of EAAT2 are essential for membrane-bound localization, substrate binding, transporter function and anion currents. J Cell Mol Med 2021; 25:2530-2548. [PMID: 33523598 PMCID: PMC7933967 DOI: 10.1111/jcmm.16212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 11/12/2020] [Accepted: 11/28/2020] [Indexed: 12/25/2022] Open
Abstract
Excitatory amino acid transporter 2 (EAAT2), the gene of which is known as solute carrier family 1 member 2 (SLC1A2), is an important membrane-bound transporter that mediates approximately 90% of the transport and clearance of l-glutamate at synapses in the central nervous system (CNS). Transmembrane domain 2 (TM2) of EAAT2 is close to hairpin loop 2 (HP2) and far away from HP1 in the inward-facing conformation. In the present study, 14 crucial amino acid residues of TM2 were identified via alanine-scanning mutations. Further analysis in EAAT2-transfected HeLa cells in vitro showed that alanine substitutions of these residues resulted in a decrease in the efficiency of trafficking/targeting to the plasma membrane and/or reduced functionality of membrane-bound, which resulted in impaired transporter activity. After additional mutations, the transporter activities of some alanine-substitution mutants recovered. Specifically, the P95A mutant decreased EAAT2-associated anion currents. The Michaelis constant (Km ) values of the mutant proteins L85A, L92A and L101A were increased significantly, whereas R87 and P95A were decreased significantly, indicating that the mutations L85A, L92A and L101A reduced the affinity of the transporter and the substrate, whereas R87A and P95A enhanced this affinity. The maximum velocity (Vmax) values of all 14 alanine mutant proteins were decreased significantly, indicating that all these mutations reduced the substrate transport rate. These results suggest that critical residues in TM2 affect not only the protein expression and membrane-bound localization of EAAT2, but also its interactions with substrates. Additionally, our findings elucidate that the P95A mutant decreased EAAT2-related anion currents. Our results indicate that the TM2 of EAAT2 plays a vital role in the transport process. The key residues in TM2 affect protein expression in the membrane, substrate transport and the anion currents of EAAT2.
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Affiliation(s)
- Dongmei Mai
- Department of NeurologyNanfang HospitalSouthern Medical UniversityGuangzhouChina
- Key Laboratory of Mental Health of the Ministry of EducationSouthern Medical UniversityGuangzhouChina
- Guangdong‐Hong Kong‐Macao Greater Bay Area Center for Brain Science and Brain‐Inspired IntelligenceGuangzhouChina
| | - Rongqing Chen
- Department of NeurobiologySchool of Basic Medical SciencesSouthern Medical UniversityGuangzhouChina
| | - Ji Wang
- Department of NeurologyNanfang HospitalSouthern Medical UniversityGuangzhouChina
- Key Laboratory of Mental Health of the Ministry of EducationSouthern Medical UniversityGuangzhouChina
- Guangdong‐Hong Kong‐Macao Greater Bay Area Center for Brain Science and Brain‐Inspired IntelligenceGuangzhouChina
| | - Jiawei Zheng
- Department of NeurobiologySchool of Basic Medical SciencesSouthern Medical UniversityGuangzhouChina
| | - Xiuping Zhang
- Teaching Center of Experimental MedicineSchool of Basic Medical SciencesSouthern Medical UniversityGuangzhouChina
| | - Shaogang Qu
- Department of NeurologyNanfang HospitalSouthern Medical UniversityGuangzhouChina
- Key Laboratory of Mental Health of the Ministry of EducationSouthern Medical UniversityGuangzhouChina
- Guangdong‐Hong Kong‐Macao Greater Bay Area Center for Brain Science and Brain‐Inspired IntelligenceGuangzhouChina
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