1
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Zhang D, Hua Z, Li Z. The role of glutamate and glutamine metabolism and related transporters in nerve cells. CNS Neurosci Ther 2024; 30:e14617. [PMID: 38358002 PMCID: PMC10867874 DOI: 10.1111/cns.14617] [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: 10/19/2023] [Revised: 12/15/2023] [Accepted: 01/10/2024] [Indexed: 02/16/2024] Open
Abstract
BACKGROUND Glutamate and glutamine are the most abundant amino acids in the blood and play a crucial role in cell survival in the nervous system. Various transporters found in cell and mitochondrial membranes, such as the solute carriers (SLCs) superfamily, are responsible for maintaining the balance of glutamate and glutamine in the synaptic cleft and within cells. This balance affects the metabolism of glutamate and glutamine as non-essential amino acids. AIMS This review aims to provide an overview of the transporters and enzymes associated with glutamate and glutamine in neuronal cells. DISCUSSION We delve into the function of glutamate and glutamine in the nervous system by discussing the transporters involved in the glutamate-glutamine cycle and the key enzymes responsible for their mutual conversion. Additionally, we highlight the role of glutamate and glutamine as carbon and nitrogen donors, as well as their significance as precursors for the synthesis of reduced glutathione (GSH). CONCLUSION Glutamate and glutamine play a crucial role in the brain due to their special effects. It is essential to focus on understanding glutamate and glutamine metabolism to comprehend the physiological behavior of nerve cells and to treat nervous system disorders and cancer.
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Affiliation(s)
- Dongyang Zhang
- Department of PediatricsShengjing Hospital of China Medical UniversityShenyangLiaoningChina
- Medical Research Center, Liaoning Key Laboratory of Research and Application of Animal Models for Environment and Metabolic DiseasesShengjing Hospital of China Medical UniversityShenyangLiaoningChina
| | - Zhongyan Hua
- Department of PediatricsShengjing Hospital of China Medical UniversityShenyangLiaoningChina
- Medical Research Center, Liaoning Key Laboratory of Research and Application of Animal Models for Environment and Metabolic DiseasesShengjing Hospital of China Medical UniversityShenyangLiaoningChina
| | - Zhijie Li
- Department of PediatricsShengjing Hospital of China Medical UniversityShenyangLiaoningChina
- Medical Research Center, Liaoning Key Laboratory of Research and Application of Animal Models for Environment and Metabolic DiseasesShengjing Hospital of China Medical UniversityShenyangLiaoningChina
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2
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Baek JH, Park H, Kang H, Kim R, Kang JS, Kim HJ. The Role of Glutamine Homeostasis in Emotional and Cognitive Functions. Int J Mol Sci 2024; 25:1302. [PMID: 38279303 PMCID: PMC10816396 DOI: 10.3390/ijms25021302] [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: 12/20/2023] [Revised: 01/17/2024] [Accepted: 01/18/2024] [Indexed: 01/28/2024] Open
Abstract
Glutamine (Gln), a non-essential amino acid, is synthesized de novo by glutamine synthetase (GS) in various organs. In the brain, GS is exclusively expressed in astrocytes under normal physiological conditions, producing Gln that takes part in glutamatergic neurotransmission through the glutamate (Glu)-Gln cycle. Because the Glu-Gln cycle and glutamatergic neurotransmission play a pivotal role in normal brain activity, maintaining Gln homeostasis in the brain is crucial. Recent findings indicated that a neuronal Gln deficiency in the medial prefrontal cortex in rodents led to depressive behaviors and mild cognitive impairment along with lower glutamatergic neurotransmission. In addition, exogenous Gln supplementation has been tested for its ability to overcome neuronal Gln deficiency and reverse abnormal behaviors induced by chronic immobilization stress (CIS). Although evidence is accumulating as to how Gln supplementation contributes to normalizing glutamatergic neurotransmission and the Glu-Gln cycle, there are few reviews on this. In this review, we summarize recent evidence demonstrating that Gln supplementation ameliorates CIS-induced deleterious changes, including an imbalance of the Glu-Gln cycle, suggesting that Gln homeostasis is important for emotional and cognitive functions. This is the first review of detailed mechanistic studies on the effects of Gln supplementation on emotional and cognitive functions.
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Affiliation(s)
| | | | | | | | | | - Hyun Joon Kim
- Department of Anatomy and Convergence Medical Sciences, College of Medicine, Institute of Medical Science, Tyrosine Peptide Multiuse Research Group, Anti-Aging Bio Cell Factory Regional Leading Research Center, Gyeongsang National University, 15 Jinju-daero 816 Beongil, Jinju 52727, Gyeongnam, Republic of Korea; (J.H.B.); (H.P.); (H.K.); (R.K.); (J.S.K.)
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3
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Taurino G, Chiu M, Bianchi MG, Griffini E, Bussolati O. The SLC38A5/SNAT5 amino acid transporter: from pathophysiology to pro-cancer roles in the tumor microenvironment. Am J Physiol Cell Physiol 2023; 325:C550-C562. [PMID: 37458433 DOI: 10.1152/ajpcell.00169.2023] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/11/2023] [Accepted: 07/11/2023] [Indexed: 08/09/2023]
Abstract
SLC38A5/SNAT5 is a system N transporter that can mediate net inward or outward transmembrane fluxes of neutral amino acids coupled with Na+ (symport) and H+ (antiport). Its preferential substrates are not only amino acids with side chains containing amide (glutamine and asparagine) or imidazole (histidine) groups, but also serine, glycine, and alanine are transported by the carrier. Expressed in the pancreas, intestinal tract, brain, liver, bone marrow, and placenta, it is regulated at mRNA and protein levels by mTORC1 and WNT/β-catenin pathways, and it is sensitive to pH, nutritional stress, inflammation, and hypoxia. SNAT5 expression has been found to be altered in pathological conditions such as chronic inflammatory diseases, gestational complications, chronic metabolic acidosis, and malnutrition. Growing experimental evidence shows that SNAT5 is overexpressed in several types of cancer cells. Moreover, recently published results indicate that SNAT5 expression in stromal cells can support the metabolic exchanges occurring in the tumor microenvironment of asparagine-auxotroph tumors. We review the functional role of the SNAT5 transporter in pathophysiology and propose that, due to its peculiar operational and regulatory features, SNAT5 may play important pro-cancer roles when expressed either in neoplastic or in stromal cells of glutamine-auxotroph tumors.NEW & NOTEWORTHY The transporter SLC38A5/SNAT5 provides net influx or efflux of glutamine, asparagine, and serine. These amino acids are of particular metabolic relevance in several conditions. Changes in transporter expression or activity have been described in selected types of human cancers, where SNAT5 can mediate amino acid exchanges between tumor and stromal cells, thus providing a potential therapeutic target. This is the first review that recapitulates the characteristics and roles of the transporter in physiology and pathology.
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Affiliation(s)
- Giuseppe Taurino
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
- MRH-Microbiome Research Hub, University of Parma, Parma, Italy
| | - Martina Chiu
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Massimiliano G Bianchi
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
- MRH-Microbiome Research Hub, University of Parma, Parma, Italy
| | - Erika Griffini
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Ovidio Bussolati
- Laboratory of General Pathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
- MRH-Microbiome Research Hub, University of Parma, Parma, Italy
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4
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Andersen JV, Schousboe A. Glial Glutamine Homeostasis in Health and Disease. Neurochem Res 2023; 48:1100-1128. [PMID: 36322369 DOI: 10.1007/s11064-022-03771-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 08/25/2022] [Accepted: 09/27/2022] [Indexed: 11/05/2022]
Abstract
Glutamine is an essential cerebral metabolite. Several critical brain processes are directly linked to glutamine, including ammonia homeostasis, energy metabolism and neurotransmitter recycling. Astrocytes synthesize and release large quantities of glutamine, which is taken up by neurons to replenish the glutamate and GABA neurotransmitter pools. Astrocyte glutamine hereby sustains the glutamate/GABA-glutamine cycle, synaptic transmission and general brain function. Cerebral glutamine homeostasis is linked to the metabolic coupling of neurons and astrocytes, and relies on multiple cellular processes, including TCA cycle function, synaptic transmission and neurotransmitter uptake. Dysregulations of processes related to glutamine homeostasis are associated with several neurological diseases and may mediate excitotoxicity and neurodegeneration. In particular, diminished astrocyte glutamine synthesis is a common neuropathological component, depriving neurons of an essential metabolic substrate and precursor for neurotransmitter synthesis, hereby leading to synaptic dysfunction. While astrocyte glutamine synthesis is quantitatively dominant in the brain, oligodendrocyte-derived glutamine may serve important functions in white matter structures. In this review, the crucial roles of glial glutamine homeostasis in the healthy and diseased brain are discussed. First, we provide an overview of cellular recycling, transport, synthesis and metabolism of glutamine in the brain. These cellular aspects are subsequently discussed in relation to pathological glutamine homeostasis of hepatic encephalopathy, epilepsy, Alzheimer's disease, Huntington's disease and amyotrophic lateral sclerosis. Further studies on the multifaceted roles of cerebral glutamine will not only increase our understanding of the metabolic collaboration between brain cells, but may also aid to reveal much needed therapeutic targets of several neurological pathologies.
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Affiliation(s)
- Jens V Andersen
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark.
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5
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Lindberg FA, Nordenankar K, Forsberg EC, Fredriksson R. SLC38A10 Deficiency in Mice Affects Plasma Levels of Threonine and Histidine in Males but Not in Females: A Preliminary Characterization Study of SLC38A10−/− Mice. Genes (Basel) 2023; 14:genes14040835. [PMID: 37107593 PMCID: PMC10138244 DOI: 10.3390/genes14040835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 03/23/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023] Open
Abstract
Solute carriers belong to the biggest group of transporters in the human genome, but more knowledge is needed to fully understand their function and possible role as therapeutic targets. SLC38A10, a poorly characterized solute carrier, is preliminary characterized here. By using a knockout mouse model, we studied the biological effects of SLC38A10 deficiency in vivo. We performed a transcriptomic analysis of the whole brain and found seven differentially expressed genes in SLC38A10-deficient mice (Gm48159, Nr4a1, Tuba1c, Lrrc56, mt-Tp, Hbb-bt and Snord116/9). By measuring amino acids in plasma, we found lower levels of threonine and histidine in knockout males, whereas no amino acid levels were affected in females, suggesting that SLC38A10−/− might affect sexes differently. Using RT-qPCR, we investigated the effect of SLC38A10 deficiency on mRNA expression of other SLC38 members, Mtor and Rps6kb1 in the brain, liver, lung, muscle, and kidney, but no differences were found. Relative telomere length measurement was also taken, as a marker for cellular age, but no differences were found between the genotypes. We conclude that SLC38A10 might be important for keeping amino acid homeostasis in plasma, at least in males, but no major effects were seen on transcriptomic expression or telomere length in the whole brain.
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6
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Huttunen J, Kronenberger T, Montaser AB, Králová A, Terasaki T, Poso A, Huttunen KM. Sodium-Dependent Neutral Amino Acid Transporter 2 Can Serve as a Tertiary Carrier for l-Type Amino Acid Transporter 1-Utilizing Prodrugs. Mol Pharm 2023; 20:1331-1346. [PMID: 36688491 PMCID: PMC9906736 DOI: 10.1021/acs.molpharmaceut.2c00948] [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] [Indexed: 01/24/2023]
Abstract
Membrane transporters are the key determinants of the homeostasis of endogenous compounds in the cells and their exposure to drugs. However, the substrate specificities of distinct transporters can overlap. In the present study, the interactions of l-type amino acid transporter 1 (LAT1)-utilizing prodrugs with sodium-coupled neutral amino acid transporter 2 (SNAT2) were explored. The results showed that the cellular uptake of LAT1-utilizing prodrugs into a human breast cancer cell line, MCF-7 cells, was mediated via SNATs as the uptake was increased at higher pH (8.5), decreased in the absence of sodium, and inhibited in the presence of unselective SNAT-inhibitor, (α-(methylamino)isobutyric acid, MeAIB). Moreover, docking the compounds to a SNAT2 homology model (inward-open conformation) and further molecular dynamics simulations and the subsequent trajectory and principal component analyses confirmed the chemical features supporting the interactions of the studied compounds with SNAT2, which was found to be the main SNAT expressed in MCF-7 cells.
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Affiliation(s)
- Johanna Huttunen
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland
| | - Thales Kronenberger
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland,Department
of Internal Medicine VIII, University Hospital
Tübingen, Otfried-Müller-Strasse
14, DE 72076 Tübingen, Germany,Department
of Pharmaceutical and Medicinal Chemistry, Institute of Pharmaceutical
Sciences, Eberhard-Karls-Universität,
Tübingen, Auf
der Morgenstelle 8, 72076 Tübingen, Germany,Cluster
of Excellence iFIT (EXC 2180) “Image-Guided and Functionally
Instructed Tumor Therapies”, University
of Tübingen, 72076 Tübingen, Germany,Tübingen
Center for Academic Drug Discovery & Development (TüCAD2), 72076 Tübingen, Germany
| | - Ahmed B. Montaser
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland
| | - Adéla Králová
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland
| | - Tetsuya Terasaki
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland
| | - Antti Poso
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland,Department
of Internal Medicine VIII, University Hospital
Tübingen, Otfried-Müller-Strasse
14, DE 72076 Tübingen, Germany,Department
of Pharmaceutical and Medicinal Chemistry, Institute of Pharmaceutical
Sciences, Eberhard-Karls-Universität,
Tübingen, Auf
der Morgenstelle 8, 72076 Tübingen, Germany,Cluster
of Excellence iFIT (EXC 2180) “Image-Guided and Functionally
Instructed Tumor Therapies”, University
of Tübingen, 72076 Tübingen, Germany,Tübingen
Center for Academic Drug Discovery & Development (TüCAD2), 72076 Tübingen, Germany
| | - Kristiina M. Huttunen
- School
of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O.
Box 1627, FI-70211 Kuopio, Finland,
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7
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Lindberg FA, Roman E, Fredriksson R. Behavioral profiling of SLC38A10 knockout mice using the multivariate concentric square field TM test. Front Behav Neurosci 2022; 16:987037. [PMID: 36620864 PMCID: PMC9815452 DOI: 10.3389/fnbeh.2022.987037] [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: 07/05/2022] [Accepted: 12/06/2022] [Indexed: 12/24/2022] Open
Abstract
Introduction SLC38A10 is a gene that encodes the SLC38A10 protein, also known as SNAT10. The SLC38 family is evolutionary old, and SLC38A10 is one of the oldest members of the family. It is ubiquitously expressed, and its substrates are glutamine, glutamate, alanine, aspartate, and serine. However, little is known about its biological importance. Methods In the current study, an SLC38A10 knockout mouse was run in the multivariate concentric square field TM (MCSF) test. The MCSF test gives the mouse a choice of areas to explore; sheltered areas, elevated and illuminated areas, or open spaces, and a behavioral profile is obtained. The multivariate data obtained were analyzed (i) for each parameter, (ii) parameters grouped into functional categories, and (iii) with a principal component analysis. Results In the trend analysis, knockout mice had a decreased exploratory behavior compared to controls but did not show a distinct grouping in the principal component analysis. Discussion There was not a pronounced difference in the behavioral profile in SLC38A10 knockout mice compared to their wild-type controls, although subtle alterations in zones associated with exploratory behavior and risk assessment in female and male knockout mice, respectively, could be observed. These results imply that a loss of function of the SLC38A10 protein in mice does not drastically alter behavior in the MSCF test.
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Affiliation(s)
- Frida A. Lindberg
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden,*Correspondence: Frida A. Lindberg,
| | - Erika Roman
- Neuropharmacology and Addiction, Uppsala University, Uppsala, Sweden,Division of Anatomy and Physiology, Department of Anatomy, Physiology and Biochemistry, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Robert Fredriksson
- Department of Pharmaceutical Biosciences, Molecular Neuropharmacology, Uppsala University, Uppsala, Sweden
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8
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Wang Z, Yemanyi F, Blomfield AK, Bora K, Huang S, Liu CH, Britton WR, Cho SS, Tomita Y, Fu Z, Ma JX, Li WH, Chen J. Amino acid transporter SLC38A5 regulates developmental and pathological retinal angiogenesis. eLife 2022; 11:e73105. [PMID: 36454214 PMCID: PMC9714971 DOI: 10.7554/elife.73105] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 11/17/2022] [Indexed: 12/03/2022] Open
Abstract
Amino acid (AA) metabolism in vascular endothelium is important for sprouting angiogenesis. SLC38A5 (solute carrier family 38 member 5), an AA transporter, shuttles neutral AAs across cell membrane, including glutamine, which may serve as metabolic fuel for proliferating endothelial cells (ECs) to promote angiogenesis. Here, we found that Slc38a5 is highly enriched in normal retinal vascular endothelium, and more specifically, in pathological sprouting neovessels. Slc38a5 is suppressed in retinal blood vessels from Lrp5-/- and Ndpy/- mice, both genetic models of defective retinal vascular development with Wnt signaling mutations. Additionally, Slc38a5 transcription is regulated by Wnt/β-catenin signaling. Genetic deficiency of Slc38a5 in mice substantially delays retinal vascular development and suppresses pathological neovascularization in oxygen-induced retinopathy modeling ischemic proliferative retinopathies. Inhibition of SLC38A5 in human retinal vascular ECs impairs EC proliferation and angiogenic function, suppresses glutamine uptake, and dampens vascular endothelial growth factor receptor 2. Together these findings suggest that SLC38A5 is a new metabolic regulator of retinal angiogenesis by controlling AA nutrient uptake and homeostasis in ECs.
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Affiliation(s)
- Zhongxiao Wang
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Felix Yemanyi
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Alexandra K Blomfield
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Kiran Bora
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Shuo Huang
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Chi-Hsiu Liu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - William R Britton
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Steve S Cho
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Yohei Tomita
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Zhongjie Fu
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
| | - Jian-xing Ma
- Department of Biochemistry, Wake Forest University School of MedicineWinston-SalemUnited States
| | - Wen-hong Li
- Departments of Cell Biology and of Biochemistry, University of Texas Southwestern Medical CenterDallasUnited States
| | - Jing Chen
- Department of Ophthalmology, Boston Children's Hospital, Harvard Medical SchoolBostonUnited States
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9
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Huttunen J, Adla SK, Markowicz-Piasecka M, Huttunen KM. Increased/Targeted Brain (Pro)Drug Delivery via Utilization of Solute Carriers (SLCs). Pharmaceutics 2022; 14:pharmaceutics14061234. [PMID: 35745806 PMCID: PMC9228667 DOI: 10.3390/pharmaceutics14061234] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/06/2022] [Accepted: 06/07/2022] [Indexed: 02/04/2023] Open
Abstract
Membrane transporters have a crucial role in compounds’ brain drug delivery. They allow not only the penetration of a wide variety of different compounds to cross the endothelial cells of the blood–brain barrier (BBB), but also the accumulation of them into the brain parenchymal cells. Solute carriers (SLCs), with nearly 500 family members, are the largest group of membrane transporters. Unfortunately, not all SLCs are fully characterized and used in rational drug design. However, if the structural features for transporter interactions (binding and translocation) are known, a prodrug approach can be utilized to temporarily change the pharmacokinetics and brain delivery properties of almost any compound. In this review, main transporter subtypes that are participating in brain drug disposition or have been used to improve brain drug delivery across the BBB via the prodrug approach, are introduced. Moreover, the ability of selected transporters to be utilized in intrabrain drug delivery is discussed. Thus, this comprehensive review will give insights into the methods, such as computational drug design, that should be utilized more effectively to understand the detailed transport mechanisms. Moreover, factors, such as transporter expression modulation pathways in diseases that should be taken into account in rational (pro)drug development, are considered to achieve successful clinical applications in the future.
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Affiliation(s)
- Johanna Huttunen
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; (J.H.); (S.K.A.)
| | - Santosh Kumar Adla
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; (J.H.); (S.K.A.)
- Institute of Organic Chemistry and Biochemistry (IOCB), Czech Academy of Sciences, Flemingovo Namesti 542/2, 160 00 Prague, Czech Republic
| | - Magdalena Markowicz-Piasecka
- Department of Pharmaceutical Chemistry, Drug Analysis and Radiopharmacy, Medical University of Lodz, ul. Muszyńskiego 1, 90-151 Lodz, Poland;
| | - Kristiina M. Huttunen
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; (J.H.); (S.K.A.)
- Correspondence:
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10
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Zielińska M, Albrecht J, Popek M. Dysregulation of Astrocytic Glutamine Transport in Acute Hyperammonemic Brain Edema. Front Neurosci 2022; 16:874750. [PMID: 35733937 PMCID: PMC9207324 DOI: 10.3389/fnins.2022.874750] [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: 02/14/2022] [Accepted: 05/17/2022] [Indexed: 11/13/2022] Open
Abstract
Acute liver failure (ALF) impairs ammonia clearance from blood, which gives rise to acute hyperammonemia and increased ammonia accumulation in the brain. Since in brain glutamine synthesis is the only route of ammonia detoxification, hyperammonemia is as a rule associated with increased brain glutamine content (glutaminosis) which correlates with and contributes along with ammonia itself to hyperammonemic brain edema-associated with ALF. This review focuses on the effects of hyperammonemia on the two glutamine carriers located in the astrocytic membrane: Slc38a3 (SN1, SNAT3) and Slc7a6 (y + LAT2). We emphasize the contribution of the dysfunction of either of the two carriers to glutaminosis- related aspects of brain edema: retention of osmotically obligated water (Slc38a3) and induction of oxidative/nitrosative stress (Slc7a6). The changes in glutamine transport link glutaminosis- evoked mitochondrial dysfunction to oxidative-nitrosative stress as formulated in the “Trojan Horse” hypothesis.
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11
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Lindberg FA, Nordenankar K, Fredriksson R. SLC38A10 Knockout Mice Display a Decreased Body Weight and an Increased Risk-Taking Behavior in the Open Field Test. Front Behav Neurosci 2022; 16:840987. [PMID: 35677577 PMCID: PMC9169716 DOI: 10.3389/fnbeh.2022.840987] [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: 12/21/2021] [Accepted: 03/21/2022] [Indexed: 11/17/2022] Open
Abstract
The solute carrier 38 family (SLC38) is a family of 11 members. The most common substrate among these are alanine and glutamine, and members are present in a wide range of tissues with important functions for several biological processes, such as liver and brain function. Some of these transporters are better characterized than others and, in this paper, a behavioral characterization of SLC38A10−/− mice was carried out. A battery of tests for general activity, emotionality, motor function, and spatial memory was used. Among these tests, the elevated plus maze, Y-maze, marble burying and challenging beam walk have not been tested on the SLC38A10−/− mice previously, while the open field and the rotarod tests have been performed by the International Mouse Phenotyping Consortium (IMPC). Unlike the results from IMPC, the results from this study showed that SLC38A10−/− mice spend less time in the wall zone in the open field test than WT mice, implying that SLC38A10-deficient mice have an increased explorative behavior, which suggests an important function of SLC38A10 in brain. The present study also confirmed IMPC's data regarding rotarod performance and weight, showing that SLC38A10−/− mice do not have an affected motor coordination impairment and have a lower body weight than both SLC38A10+/− and SLC38A10+/+ mice. These results imply that a complete deficiency of the SLC38A10 protein might affect body weight homeostasis, but the underlying mechanisms needs to be studied further.
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12
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Gururajan A, Bastiaanssen TFS, Ventura Silva AP, Moloney GM, Cryan JF. The impact of psychosocial defeat stress on the bed nucleus of the stria terminalis transcriptome in adult male mice. Eur J Neurosci 2021; 55:67-77. [PMID: 34904308 DOI: 10.1111/ejn.15567] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2021] [Revised: 11/07/2021] [Accepted: 12/05/2021] [Indexed: 01/07/2023]
Abstract
The bed nucleus of the stria terminalis (BNST) is a focal point for the convergence of inputs from canonical stress-sensitive structures to fine-tune the response to stress. However, its role in mediating phenotypes of stress resilience or susceptibility is yet to be fully defined. In this study, we carried out unbiased RNA-sequencing to analyse the BNST transcriptomes of adult male mice, which were classified as resilient or susceptible following a 10-day chronic psychosocial defeat stress paradigm. Pairwise comparisons revealed 20 differentially expressed genes in resilience (6) and susceptible (14) mice compared with controls. An in silico validation of our data against an earlier study revealed significant concordance in gene expression profiles associated with resilience to chronic stress. Enrichment analysis revealed that resilience is linked to functions including retinoic acid hydrolase activity, phospholipase inhibitor and tumour necrosis factor (TNF)-receptor activities, whereas susceptibility is linked to alterations in amino acid transporter activity. We also identified differential usage of 134 exons across 103 genes associated with resilience and susceptibility; enrichment analysis for genes with differential exon usage in resilient mice was linked to functions including adrenergic receptor binding mice and oxysterol binding in susceptible mice. Our findings highlight the important and underappreciated role of the BNST in stress resilience and susceptibility and reveal research avenues for follow-up investigations.
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Affiliation(s)
- Anand Gururajan
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland.,School of Psychology, Faculty of Science, University of Sydney, Sydney, New South Wales, Australia
| | - Thomaz F S Bastiaanssen
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Ana Paula Ventura Silva
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - Gerard M Moloney
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
| | - John F Cryan
- Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.,APC Microbiome Ireland, University College Cork, Cork, Ireland
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13
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Goldberg LR, Yao EJ, Kelliher JC, Reed ER, Cox JW, Parks C, Kirkpatrick SL, Beierle JA, Chen MM, Johnson WE, Homanics GE, Williams RW, Bryant CD, Mulligan MK. A quantitative trait variant in Gabra2 underlies increased methamphetamine stimulant sensitivity. GENES, BRAIN, AND BEHAVIOR 2021; 20:e12774. [PMID: 34677900 PMCID: PMC9083095 DOI: 10.1111/gbb.12774] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/19/2021] [Accepted: 09/15/2021] [Indexed: 12/24/2022]
Abstract
Psychostimulant (methamphetamine, cocaine) use disorders have a genetic component that remains mostly unknown. We conducted genome-wide quantitative trait locus (QTL) analysis of methamphetamine stimulant sensitivity. To facilitate gene identification, we employed a Reduced Complexity Cross between closely related C57BL/6 mouse substrains and examined maximum speed and distance traveled over 30 min following methamphetamine (2 mg/kg, i.p.). For maximum methamphetamine-induced speed following the second and third administration, we identified a single genome-wide significant QTL on chromosome 11 that peaked near the Cyfip2 locus (LOD = 3.5, 4.2; peak = 21 cM [36 Mb]). For methamphetamine-induced distance traveled following the first and second administration, we identified a genome-wide significant QTL on chromosome 5 that peaked near a functional intronic indel in Gabra2 coding for the alpha-2 subunit of the GABA-A receptor (LOD = 3.6-5.2; peak = 34-35 cM [66-67 Mb]). Striatal cis-expression QTL mapping corroborated Gabra2 as a functional candidate gene underlying methamphetamine-induced distance traveled. CRISPR/Cas9-mediated correction of the mutant intronic deletion on the C57BL/6J background to the wild-type C57BL/6NJ allele was sufficient to reduce methamphetamine-induced locomotor activity toward the wild-type C57BL/6NJ-like level, thus validating the quantitative trait variant (QTV). These studies show the power and efficiency of Reduced Complexity Crosses in identifying causal variants underlying complex traits. Functionally restoring Gabra2 expression decreased methamphetamine stimulant sensitivity and supports preclinical and human genetic studies implicating the GABA-A receptor in psychostimulant addiction-relevant traits. Importantly, our findings have major implications for studying psychostimulants in the C57BL/6J strain-the gold standard strain in biomedical research.
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Affiliation(s)
- Lisa R. Goldberg
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
- NIGMS T32 Ph.D. Training Program in Biomolecular Pharmacology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Emily J. Yao
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
| | - Julia C. Kelliher
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
| | - Eric R. Reed
- Ph.D. Program in Bioinformatics, Boston University, Boston, Massachusetts, USA
| | - Jiayi Wu Cox
- Program in Biomedical Sciences, Graduate Program in Genetics and Genomics, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Cory Parks
- Department of Agricultural, Biology, and Health Sciences, Cameron University, Lawton, Oklahoma, USA
| | - Stacey L. Kirkpatrick
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
| | - Jacob A. Beierle
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
- NIGMS T32 Ph.D. Training Program in Biomolecular Pharmacology, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Melanie M. Chen
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
| | - William E. Johnson
- Department of Medicine, Computational Medicine, Boston University School of Medicine, Boston, Massachusetts, USA
| | - Gregg E. Homanics
- Departments of Anesthesiology, Neurobiology, and Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Robert W. Williams
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Camron D. Bryant
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston, Massachusetts, USA
| | - Megan K. Mulligan
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, Tennessee, USA
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14
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Hamdani EH, Popek M, Frontczak-Baniewicz M, Utheim TP, Albrecht J, Zielińska M, Chaudhry FA. Perturbation of astroglial Slc38 glutamine transporters by NH 4 + contributes to neurophysiologic manifestations in acute liver failure. FASEB J 2021; 35:e21588. [PMID: 34169573 DOI: 10.1096/fj.202001712rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Revised: 03/17/2021] [Accepted: 03/25/2021] [Indexed: 02/07/2023]
Abstract
Ammonia is considered the main pathogenic toxin in hepatic encephalopathy (HE). However, the molecular mechanisms involved have been disputed. As altered glutamatergic and GABAergic neurotransmission has been reported in HE, we investigated whether four members of the solute carrier 38 (Slc38) family of amino acid transporters-involved in the replenishment of glutamate and GABA-contribute to ammonia neurotoxicity in HE. We show that ammonium ion exerts multiple actions on the Slc38 transporters: It competes with glutamine for the binding to the system N transporters Slc38a3 and Slc38a5, consequently inhibiting bidirectional astroglial glutamine transport. It also competes with H+ , Na+ , and K+ for uncoupled permeation through the same transporters, which may perturb astroglial intracellular pH, membrane potential, and K+ -buffering. Knockdown of Slc38a3 in mice results in cerebral cortical edema and disrupted neurotransmitter synthesis mimicking events contributing to HE development. Finally, in a mouse model of acute liver failure (ALF), we demonstrate the downregulation of Slc38a3 protein, impeded astroglial glutamine release, and cytotoxic edema. Altogether, we demonstrate contribution of Slc38 transporters to the ammonia-induced impairment of glutamine recycling between astrocytes and neurons, a phenomenon underlying acute ammonia neurotoxicity in the setting of ALF.
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Affiliation(s)
- El Hassan Hamdani
- Department of Molecular Medicine, University of Oslo (UiO), Oslo, Norway.,Institute of Behavioural Science, Oslo Metropolitan University, Oslo, Norway
| | - Mariusz Popek
- Neurotoxicology Department, Mossakowski Medical Research Institute PAS, Warsaw, Poland
| | | | - Tor Paaske Utheim
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway.,Department of Plastic and Reconstructive Surgery, Oslo University Hospital, Oslo, Norway
| | - Jan Albrecht
- Neurotoxicology Department, Mossakowski Medical Research Institute PAS, Warsaw, Poland
| | - Magdalena Zielińska
- Neurotoxicology Department, Mossakowski Medical Research Institute PAS, Warsaw, Poland
| | - Farrukh Abbas Chaudhry
- Department of Molecular Medicine, University of Oslo (UiO), Oslo, Norway.,Department of Plastic and Reconstructive Surgery, Oslo University Hospital, Oslo, Norway
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15
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Popek M, Bobula B, Sowa J, Hess G, Frontczak-Baniewicz M, Albrecht J, Zielińska M. Physiology and Morphological Correlates of Excitatory Transmission are Preserved in Glutamine Transporter SN1-Depleted Mouse Frontal Cortex. Neuroscience 2020; 446:124-136. [DOI: 10.1016/j.neuroscience.2020.08.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 07/16/2020] [Accepted: 08/14/2020] [Indexed: 01/22/2023]
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16
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Qureshi T, Bjørkmo M, Nordengen K, Gundersen V, Utheim TP, Watne LO, Storm-Mathisen J, Hassel B, Chaudhry FA. Slc38a1 Conveys Astroglia-Derived Glutamine into GABAergic Interneurons for Neurotransmitter GABA Synthesis. Cells 2020; 9:E1686. [PMID: 32668809 PMCID: PMC7407890 DOI: 10.3390/cells9071686] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 07/06/2020] [Accepted: 07/08/2020] [Indexed: 12/17/2022] Open
Abstract
GABA signaling is involved in a wide range of neuronal functions, such as synchronization of action potential firing, synaptic plasticity and neuronal development. Sustained GABA signaling requires efficient mechanisms for the replenishment of the neurotransmitter pool of GABA. The prevailing theory is that exocytotically released GABA may be transported into perisynaptic astroglia and converted to glutamine, which is then shuttled back to the neurons for resynthesis of GABA-i.e., the glutamate/GABA-glutamine (GGG) cycle. However, an unequivocal demonstration of astroglia-to-nerve terminal transport of glutamine and the contribution of astroglia-derived glutamine to neurotransmitter GABA synthesis is lacking. By genetic inactivation of the amino acid transporter Solute carrier 38 member a1 (Slc38a1)-which is enriched on parvalbumin+ GABAergic neurons-and by intraperitoneal injection of radiolabeled acetate (which is metabolized to glutamine in astroglial cells), we show that Slc38a1 mediates import of astroglia-derived glutamine into GABAergic neurons for synthesis of GABA. In brain slices, we demonstrate the role of Slc38a1 for the uptake of glutamine specifically into GABAergic nerve terminals for the synthesis of GABA depending on demand and glutamine supply. Thus, while leaving room for other pathways, our study demonstrates a key role of Slc38a1 for newly formed GABA, in harmony with the existence of a GGG cycle.
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Affiliation(s)
- Tayyaba Qureshi
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (T.Q.); (M.B.); (K.N.); (V.G.); (J.S.-M.)
| | - Mona Bjørkmo
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (T.Q.); (M.B.); (K.N.); (V.G.); (J.S.-M.)
| | - Kaja Nordengen
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (T.Q.); (M.B.); (K.N.); (V.G.); (J.S.-M.)
| | - Vidar Gundersen
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (T.Q.); (M.B.); (K.N.); (V.G.); (J.S.-M.)
| | - Tor Paaske Utheim
- Department of Plastic and Reconstructive Surgery, Oslo University Hospital, 0424 Oslo, Norway;
| | - Leiv Otto Watne
- Department of Geriatric Medicine, Oslo University Hospital, 0424 Oslo, Norway;
| | - Jon Storm-Mathisen
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (T.Q.); (M.B.); (K.N.); (V.G.); (J.S.-M.)
| | - Bjørnar Hassel
- Department of Neurohabilitation, Oslo University Hospital and University of Oslo, 0424 Oslo, Norway;
| | - Farrukh Abbas Chaudhry
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway; (T.Q.); (M.B.); (K.N.); (V.G.); (J.S.-M.)
- Department of Plastic and Reconstructive Surgery, Oslo University Hospital, 0424 Oslo, Norway;
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17
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Tripathi R, Hosseini K, Arapi V, Fredriksson R, Bagchi S. SLC38A10 (SNAT10) is Located in ER and Golgi Compartments and Has a Role in Regulating Nascent Protein Synthesis. Int J Mol Sci 2019; 20:ijms20246265. [PMID: 31842320 PMCID: PMC6940841 DOI: 10.3390/ijms20246265] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 12/03/2019] [Accepted: 12/09/2019] [Indexed: 01/27/2023] Open
Abstract
The solute carrier (SLC) family-38 of transporters has eleven members known to transport amino acids, with glutamine being a common substrate for ten of them, with SLC38A9 being the exception. In this study, we examine the subcellular localization of SNAT10 in several independent immortalized cell lines and stem cell-derived neurons. Co-localization studies confirmed the SNAT10 was specifically localized to secretory organelles. SNAT10 is expressed in both excitatory and inhibitory neurons in the mouse brain, predominantly in the endoplasmic reticulum, and in the Golgi apparatus. Knock-down experiments of SNAT10, using Slc38a10-specific siRNA in PC12 cells reduced nascent protein synthesis by more than 40%, suggesting that SNAT10 might play a role in signaling pathways that regulate protein synthesis, and may act as a transceptor in a similar fashion to what has been shown previously for SLC38A2 (SNAT2) and SNAT9(SLC38A9).
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18
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Natarajan SK, Venneti S. Glutamine Metabolism in Brain Tumors. Cancers (Basel) 2019; 11:E1628. [PMID: 31652923 PMCID: PMC6893651 DOI: 10.3390/cancers11111628] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 10/18/2019] [Accepted: 10/19/2019] [Indexed: 12/14/2022] Open
Abstract
Altered metabolism is a hallmark of cancer cells. Tumor cells rewire their metabolism to support their uncontrolled proliferation by taking up nutrients from the microenvironment. The amino acid glutamine is a key nutrient that fuels biosynthetic processes including ATP generation, redox homeostasis, nucleotide, protein, and lipid synthesis. Glutamine as a precursor for the neurotransmitter glutamate, and plays a critical role in the normal functioning of the brain. Brain tumors that grow in this glutamine/glutamate rich microenvironment can make synaptic connections with glutamatergic neurons and reprogram glutamine metabolism to enable their growth. In this review, we examine the functions of glutamate/glutamine in the brain and how brain tumor cells reprogram glutamine metabolism. Altered glutamine metabolism can be leveraged to develop non-invasive imaging strategies and we review these imaging modalities. Finally, we examine if targeting glutamine metabolism could serve as a therapeutic strategy in brain tumors.
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Affiliation(s)
- Siva Kumar Natarajan
- Laboratory of Brain Tumor Metabolism and Epigenetics, Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
| | - Sriram Venneti
- Laboratory of Brain Tumor Metabolism and Epigenetics, Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
- Department of Pathology, University of Michigan 3520E MSRB 1, 1150 West Medical Center Drive, Ann Arbor, MI 41804, USA.
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19
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Luengo JG, Muñoz MD, Álvarez-Merz I, Herranz AS, González JC, Martín del Río R, Hernández-Guijo JM, Solís JM. Intracellular accumulation of amino acids increases synaptic potentials in rat hippocampal slices. Amino Acids 2019; 51:1337-1351. [DOI: 10.1007/s00726-019-02771-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 08/11/2019] [Indexed: 12/22/2022]
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20
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McColl ER, Piquette-Miller M. Poly(I:C) alters placental and fetal brain amino acid transport in a rat model of maternal immune activation. Am J Reprod Immunol 2019; 81:e13115. [PMID: 30924965 DOI: 10.1111/aji.13115] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 03/18/2019] [Accepted: 03/19/2019] [Indexed: 12/13/2022] Open
Abstract
PROBLEM Maternal immune activation (MIA) during pregnancy is associated with increased chances of neurodevelopmental disorders including schizophrenia and autism spectrum disorder (ASD). However, the exact mechanism through which MIA contributes to altered neurodevelopment is unknown. Due to the important role that amino acids play in neurodevelopment, altered amino acid transport could play a role in neurodevelopmental disorders. Indeed, altered plasma concentrations of multiple amino acids have been reported in individuals with ASD or schizophrenia. Therefore, our objective was to determine whether virally mediated MIA induces changes in amino acid transporters in the placenta and fetal brain. METHOD OF STUDY Pregnant rats were administered poly(I:C) on gestational day 14, and placental and fetal tissues were collected 6, 24, and 48 hours later. Amino acid transporter expression was measured in the placenta and fetal brain using qPCR, Western blotting, and Simple Western. Free amino acid concentrations in the fetal brain were quantified using HPLC. RESULTS Poly(I:C) increased mRNA expression of several amino acid transporters in the placenta and fetal brain over these timepoints. Conversely, poly(I:C) imposed significant decreases in the protein expression of ASCT1 and EAAT2 in placenta and expression of SNAT5, EAAT1, and GLYT1 in fetal brain. Functional consequences of altered transporter expression were demonstrated through widespread changes in the concentrations of free amino acids in the fetal brains. CONCLUSION Together, these results represent novel findings with the poly(I:C) MIA model and contribute to the understanding of how MIA during pregnancy potentially leads to neurodevelopmental disorders.
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Affiliation(s)
- Eliza R McColl
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
| | - Micheline Piquette-Miller
- Department of Pharmaceutical Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, Canada
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21
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Exchange-mode glutamine transport across CNS cell membranes. Neuropharmacology 2019; 161:107560. [PMID: 30853601 DOI: 10.1016/j.neuropharm.2019.03.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 02/28/2019] [Accepted: 03/02/2019] [Indexed: 12/18/2022]
Abstract
CNS cell membranes possess four transporters capable of exchanging Lglutamine (Gln) for other amino acids: the large neutral amino acid (LNAA) transporters LAT1 and LAT2, the hybrid basic amino acid (L-arginine (Arg), L-leucine (Leu)/LNAA transporter y+LAT2, and the L-alanine/L-serine/L-cysteine transporter 2 (ASCT2). LAT1/LAT2 and y+LAT2 are present in astrocytes, neurons and the blood brain barrier (BBB) - forming cerebral vascular endothelial cells (CVEC), while the location of ASCT2 in the individual cell types is a matter of debate. In the healthy brain, contribution of the exchangers to Gln shuttling from astrocytes to neurons and thus their role in controlling the conversion of Gln to the amino acid neurotransmitters l-glutamate (Glu) and γ-aminobutyric acid (GABA) and Gln flux across the BBB appears negligible as compared to the system A and system N uniporters. Insofar, except for the contribution of LAT1 to the maintenance of Gln homeostasis in the interstitial fluid (ISF), no well-defined CNS-specific function has been established for either of the three transporters in the healthy brain. The Gln-accepting amino acid exchangers appear to gain significance under conditions of excessive brain Gln load (glutaminosis). Excess Gln efflux across the BBB enhances influx into the brain of L-tryptophan (Trp). Excess of Trp is responsible for overloading the brain with neuroactive compounds: serotonin, kynurenic acid, quinolinic acid and/or oxindole, which contribute to neurotransmission imbalance accompanying hyperammonemia. In turn, alterations of y+LAT2-mediated Gln/Arg exchange and Arg uptake in astrocyte, modulate astrocytic nitric oxide synthesis and oxidative/nitrosative stress in ammonia-overexposed brain. This article is part of the issue entitled 'Special Issue on Neurotransmitter Transporters'.
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22
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Anand AC, Singh P. Neurological Recovery After Recovery From Acute Liver Failure: Is it Complete? J Clin Exp Hepatol 2019; 9:99-108. [PMID: 30765942 PMCID: PMC6363962 DOI: 10.1016/j.jceh.2018.06.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 06/11/2018] [Indexed: 12/12/2022] Open
Abstract
Neurologic dysfunction characterised by Hepatic Encephalopathy (HE) and cerebral oedema are the most dramatic presentations of Acute Liver Failure (ALF) and signify poor outcome. Improved critical care and wider availability of emergency Liver Transplantation (LT) has improved survivability in ALF. In most cases absence of clinically overt encephalopathy after spontaneous recovery from ALF or after LT is thought to indicate complete neurologic recovery. Recent data suggests that neurologic recovery may not always be complete. Instances of persistent neurologic dysfunction as well as neuropsychiatric abnormalities are now being recognised and warrant active follow up of these patients. Although evidences irreversible neurologic damage is uncommon after ALF, neuropsychiatric disturbances are not uncommon. Complex pathogenesis is involved in neurocognitive disorders seen after many other conditions including LT that require critical care. Structural damage and persistent neurological abnormalities seen after ALF are more likely to be related to cerebral edema, raised intracranial tension and cerebral hypoxemia, while neurocognitive dysfunctions may be a part of a wider spectrum of disorders commonly seen among those who recover from any critical illness.
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Key Words
- ALF, Acute Liver Failure
- APAP, Acetaminophen
- BBB, Blood Brain Barrier
- CARS, Compensatory Anti-Inflammatory Response Syndrome
- CVVH, Continuous Veno-Venous Hemodialysis
- DAMPS, Damage Associated Molecular Pattern
- DWI, Diffusion-Weighted Imaging
- EEG, Electroencephalography
- FLAIR, Fluid-Attenuated Inversion Recovery
- HE, Hepatic Encephalopathy
- LT, Liver Transplantation
- MPT, Mitochondrial Permeability Transition
- PET, Positron Emission Tomography
- SIRS, Systemic Inflammatory Response Syndrome
- acute liver failure
- cerebral oedema
- hepatic encephalopathy
- neurological dysfunction
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Affiliation(s)
- Anil C. Anand
- Address for correspondence: Anil C. Anand, Senior Consultant, Gastroenterology & Hepatology, Indraprastha Apollo Hospital, New Delhi 110076, India.
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23
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Zafra F, Ibáñez I, Bartolomé-Martín D, Piniella D, Arribas-Blázquez M, Giménez C. Glycine Transporters and Its Coupling with NMDA Receptors. ADVANCES IN NEUROBIOLOGY 2018; 16:55-83. [PMID: 28828606 DOI: 10.1007/978-3-319-55769-4_4] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Glycine plays two roles in neurotransmission. In caudal areas like the spinal cord and the brainstem, it acts as an inhibitory neurotransmitter, but in all regions of the CNS, it also works as a co-agonist with L-glutamate at N-methyl-D-aspartate receptors (NMDARs). The glycine fluxes in the CNS are regulated by two specific transporters for glycine, GlyT1 and GlyT2, perhaps with the cooperation of diverse neutral amino acid transporters like Asc-1 or SNAT5/SN2. While GlyT2 and Asc-1 are neuronal proteins, GlyT1 and SNAT5 are mainly astrocytic, although neuronal forms of GlyT1 also exist. GlyT1 has attracted considerable interest from the medical community and the pharmaceutical industry since compelling evidence indicates a clear association with the functioning of NMDARs, whose activity is decreased in various psychiatric illnesses. By controlling extracellular glycine, transporter inhibitors might potentiate the activity of NMDARs without activating excitotoxic processes. Physiologically, GlyT1 is a central actor in the cross talk between glutamatergic, glycinergic, dopaminergic, and probably other neurotransmitter systems. Many of these relationships begin to be unraveled by studies performed in recent years using genetic and pharmacological models. These studies are also clarifying the interactions between glycine, glycine transporters, and other co-agonists of the glycine site of NMDARs like D-serine. These findings are also relevant to understand the pathophysiology of devastating diseases like schizophrenia, depression, anxiety, epilepsy, stroke, and chronic pain.
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Affiliation(s)
- Francisco Zafra
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain.
| | - Ignacio Ibáñez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - David Bartolomé-Martín
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Dolores Piniella
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Marina Arribas-Blázquez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
| | - Cecilio Giménez
- Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, C / Nicolás Cabrera, 1, 28049, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras and IdiPAZ, Instituto de Salud Carlos III, Madrid, Spain
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24
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Hellsten SV, Tripathi R, Ceder MM, Fredriksson R. Nutritional Stress Induced by Amino Acid Starvation Results in Changes for Slc38 Transporters in Immortalized Hypothalamic Neuronal Cells and Primary Cortex Cells. Front Mol Biosci 2018; 5:45. [PMID: 29868606 PMCID: PMC5952004 DOI: 10.3389/fmolb.2018.00045] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 04/18/2018] [Indexed: 01/01/2023] Open
Abstract
Amino acid sensing and signaling is vital for cells, and both gene expression and protein levels of amino acid transporters are regulated in response to amino acid availability. Here, the aim was to study the regulation of all members of the SLC38 amino acid transporter family, Slc38a1-11, in mouse brain cells following amino acid starvation. We reanalyzed microarray data for the immortalized hypothalamic cell line N25/2 subjected to complete amino acid starvation for 1, 2, 3, 5, or 16 h, focusing specifically on the SLC38 family. All 11 Slc38 genes were expressed in the cell line, and Slc38a1, Slc38a2, and Slc38a7 were significantly upregulated at 5 h and most strongly at 16 h. Here, protein level changes were measured for SLC38A7 and the orphan family member SLC38A11 which has not been studied under different amino acid starvation condition at protein level. At 5 h, no significant alteration on protein level for either SLC38A7 or SLC38A11 could be detected. In addition, primary embryonic cortex cells were deprived of nine amino acids, the most common amino acids transported by the SLC38 family members, for 3 h, 7 h or 12 h, and the gene expression was measured using qPCR. Slc38a1, Slc38a2, Slc38a5, Slc38a6, Slc38a9, and Slc38a10 were upregulated, while Slc38a3 and Slc38a7 were downregulated. Slc38a8 was upregulated at 5 h and downregulated at 12 h. In conclusion, several members from the SLC38 family are regulated depending on amino acid levels and are likely to be involved in amino acid sensing and signaling in brain.
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Affiliation(s)
- Sofie V Hellsten
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Rekha Tripathi
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Mikaela M Ceder
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
| | - Robert Fredriksson
- Molecular Neuropharmacology, Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
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Hellsten SV, Hägglund MG, Eriksson MM, Fredriksson R. The neuronal and astrocytic protein SLC38A10 transports glutamine, glutamate, and aspartate, suggesting a role in neurotransmission. FEBS Open Bio 2017; 7:730-746. [PMID: 28593130 PMCID: PMC5458457 DOI: 10.1002/2211-5463.12219] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Revised: 03/03/2017] [Accepted: 03/08/2017] [Indexed: 12/21/2022] Open
Abstract
In brain cells, glutamine transporters are vital to monitor and control the levels of glutamate and GABA. There are 11 members of the SLC38 family of amino acid transporters of which eight have been functionally characterized. Here, we report the first histological and functional characterization of the previously orphan member, SLC38A10. We used pairwise global sequence alignments to determine the sequence identity between the SLC38 family members. SLC38A10 was found to share 20–25% transmembrane sequence identity with several family members, and was predicted to have 11 transmembrane helices. SLC38A10 immunostaining was abundant in mouse brain using a custom‐made anti‐SLC38A10 antibody and colocalization of SLC38A10 immunoreactivity with markers for neurons and astrocytes was detected. Using Xenopus laevis oocytes overexpressing SLC38A10, we show that SLC38A10 mediates bidirectional transport of l‐glutamine, l‐alanine, l‐glutamate, and d‐aspartate, and efflux of l‐serine. This profile mostly resembles system A members of the SLC38 family. In conclusion, the bidirectional transport of glutamine, glutamate, and aspartate by SLC38A10, and the immunostaining detected in neurons and astrocytes, suggest that SLC38A10 plays a role in pathways involved in neurotransmission.
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Affiliation(s)
- Sofie V Hellsten
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology Uppsala University Sweden
| | - Maria G Hägglund
- Department of Neuroscience, Functional Pharmacology Uppsala University Sweden
| | - Mikaela M Eriksson
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology Uppsala University Sweden
| | - Robert Fredriksson
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology Uppsala University Sweden
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26
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Todd AC, Marx MC, Hulme SR, Bröer S, Billups B. SNAT3-mediated glutamine transport in perisynaptic astrocytesin situis regulated by intracellular sodium. Glia 2017; 65:900-916. [DOI: 10.1002/glia.23133] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 01/12/2017] [Accepted: 02/08/2017] [Indexed: 01/16/2023]
Affiliation(s)
- Alison C. Todd
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research; The Australian National University; 131 Garran Road Canberra ACT 2601 Australia
- Centre for Integrative Physiology, School of Biomedical Sciences; University of Edinburgh; Edinburgh EH8 9XD United Kingdom
| | - Mari-Carmen Marx
- Department of Pharmacology; University of Cambridge; Tennis Court Road Cambridge CB2 1BT United Kingdom
| | - Sarah R. Hulme
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research; The Australian National University; 131 Garran Road Canberra ACT 2601 Australia
| | - Stefan Bröer
- Research School of Biology; The Australian National University; Linnaeus Way 134 Canberra ACT 2601 Australia
| | - Brian Billups
- Eccles Institute of Neuroscience, The John Curtin School of Medical Research; The Australian National University; 131 Garran Road Canberra ACT 2601 Australia
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27
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Hellsten SV, Eriksson MM, Lekholm E, Arapi V, Perland E, Fredriksson R. The gene expression of the neuronal protein, SLC38A9, changes in mouse brain after in vivo starvation and high-fat diet. PLoS One 2017; 12:e0172917. [PMID: 28235079 PMCID: PMC5325605 DOI: 10.1371/journal.pone.0172917] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 02/03/2017] [Indexed: 11/18/2022] Open
Abstract
SLC38A9 is characterized as a lysosomal component of the amino acid sensing Ragulator-RAG GTPase complex, controlling the mechanistic target of rapamycin complex 1 (mTORC1). Here, immunohistochemistry was used to map SLC38A9 in mouse brain and staining was detected throughout the brain, in cortex, hypothalamus, thalamus, hippocampus, brainstem and cerebellum. More specifically, immunostaining was found in areas known to be involved in amino acid sensing and signaling pathways e.g. piriform cortex and hypothalamus. SLC38A9 immunoreactivity co-localized with both GABAergic and glutamatergic neurons, but not with astrocytes. SLC38A9 play a key role in the mTORC1 pathway, and therefore we performed in vivo starvation and high-fat diet studies, to measure gene expression alterations in specific brain tissues and in larger brain regions. Following starvation, Slc38a9 was upregulated in brainstem and cortex, and in anterior parts of the brain (Bregma 3.2 to -2.1mm). After high-fat diet, Slc38a9 was specifically upregulated in hypothalamus, while overall downregulation was noticed throughout the brain (Bregma 3.2 to -8.6mm).
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Affiliation(s)
- Sofie V. Hellsten
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology, Uppsala University, Uppsala SE, Sweden
- * E-mail:
| | - Mikaela M. Eriksson
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology, Uppsala University, Uppsala SE, Sweden
| | - Emilia Lekholm
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology, Uppsala University, Uppsala SE, Sweden
| | - Vasiliki Arapi
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology, Uppsala University, Uppsala SE, Sweden
| | - Emelie Perland
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology, Uppsala University, Uppsala SE, Sweden
| | - Robert Fredriksson
- Department of Pharmaceutical Bioscience, Molecular Neuropharmacology, Uppsala University, Uppsala SE, Sweden
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Dolgodilina E, Imobersteg S, Laczko E, Welt T, Verrey F, Makrides V. Brain interstitial fluid glutamine homeostasis is controlled by blood-brain barrier SLC7A5/LAT1 amino acid transporter. J Cereb Blood Flow Metab 2016; 36:1929-1941. [PMID: 26661195 PMCID: PMC5094305 DOI: 10.1177/0271678x15609331] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/20/2015] [Accepted: 08/31/2015] [Indexed: 01/26/2023]
Abstract
L-glutamine (Gln) is the most abundant amino acid in plasma and cerebrospinal fluid and a precursor for the main central nervous system excitatory (L-glutamate) and inhibitory (γ-aminobutyric acid (GABA)) neurotransmitters. Concentrations of Gln and 13 other brain interstitial fluid amino acids were measured in awake, freely moving mice by hippocampal microdialysis using an extrapolation to zero flow rate method. Interstitial fluid levels for all amino acids including Gln were ∼5-10 times lower than in cerebrospinal fluid. Although the large increase in plasma Gln by intraperitoneal (IP) injection of 15N2-labeled Gln (hGln) did not increase total interstitial fluid Gln, low levels of hGln were detected in microdialysis samples. Competitive inhibition of system A (SLC38A1&2; SNAT1&2) or system L (SLC7A5&8; LAT1&2) transporters in brain by perfusion with α-(methylamino)-isobutyric acid (MeAIB) or 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH) respectively, was tested. The data showed a significantly greater increase in interstitial fluid Gln upon BCH than MeAIB treatment. Furthermore, brain BCH perfusion also strongly increased the influx of hGln into interstitial fluid following IP injection consistent with transstimulation of LAT1-mediated transendothelial transport. Taken together, the data support the independent homeostatic regulation of amino acids in interstitial fluid vs. cerebrospinal fluid and the role of the blood-brain barrier expressed SLC7A5/LAT1 as a key interstitial fluid gatekeeper.
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Affiliation(s)
- Elena Dolgodilina
- Institute of Physiology, Zurich Center for Integrative Human Physiology (ZIHP) and NCCR Kidney. CH, University of Zurich, Zurich, Switzerland
| | - Stefan Imobersteg
- Division of Psychiatry Research, University of Zurich, Schlieren, Switzerland
| | - Endre Laczko
- Functional Genomic Center Zurich (FGCZ), ETH and University of Zurich, Zurich, Switzerland
| | - Tobias Welt
- Division of Psychiatry Research, University of Zurich, Schlieren, Switzerland
| | - Francois Verrey
- Institute of Physiology, Zurich Center for Integrative Human Physiology (ZIHP) and NCCR Kidney. CH, University of Zurich, Zurich, Switzerland
| | - Victoria Makrides
- Institute of Physiology, Zurich Center for Integrative Human Physiology (ZIHP) and NCCR Kidney. CH, University of Zurich, Zurich, Switzerland
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29
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In vivo N-15 MRS study of glutamate metabolism in the rat brain. Anal Biochem 2016; 529:179-192. [PMID: 27580850 DOI: 10.1016/j.ab.2016.08.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 08/22/2016] [Accepted: 08/24/2016] [Indexed: 01/05/2023]
Abstract
In vivo 15N MRS has made a unique contribution to kinetic studies of the individual pathways that control glutamate flux in the rat brain. This review covers the following topics: (1) the advantages and limitations of in vivo 15N MRS and its indirect detection through coupled 1H; (2) kinetic methods; (3) major findings from our and other laboratories in the areas: (a) the uptake of the neurotransmitter glutamate from the extracellular fluid into glia; (b) the metabolism of glutamate to glutamine; (c) glutamine transport to the extracellular fluid; (d) hydrolysis of neuronal glutamine to glutamate; and (e) contribution of transamination from leucine to replenish the glutamate nitrogen. In vivo glutamine synthetase activities measured at several levels of hyperammonemia showed that this enzyme becomes saturated at blood ammonia concentration >0.9 μmol/g, and causes the elevation of brain ammonia. Implications of the results for the cause of hyperammonemic encephalopathy are discussed. Leucine provides >25% of glutamate nitrogen. An intriguing possibility that supplementing leucine may restore cognitive function after brain injury is discussed. Finally, some characteristics of 15N MRS that may facilitate the future application of this technique to the study of the human brain at 4 or 7 T are described.
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Rubio-Aliaga I, Wagner CA. Regulation and function of the SLC38A3/SNAT3 glutamine transporter. Channels (Austin) 2016; 10:440-52. [PMID: 27362266 DOI: 10.1080/19336950.2016.1207024] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Affiliation(s)
- Isabel Rubio-Aliaga
- a Institute of Physiology, the National Center for Competence in Research NCCR Kidney, University of Zurich , Zurich , Switzerland
| | - Carsten A Wagner
- a Institute of Physiology, the National Center for Competence in Research NCCR Kidney, University of Zurich , Zurich , Switzerland
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31
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The Glutamine Transporters and Their Role in the Glutamate/GABA-Glutamine Cycle. ADVANCES IN NEUROBIOLOGY 2016; 13:223-257. [PMID: 27885631 DOI: 10.1007/978-3-319-45096-4_8] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Glutamine is a key amino acid in the CNS, playing an important role in the glutamate/GABA-glutamine cycle (GGC). In the GGC, glutamine is transferred from astrocytes to neurons, where it will replenish the inhibitory and excitatory neurotransmitter pools. Different transporters participate in this neural communication, i.e., the transporters responsible for glutamine efflux from astrocytes and influx into the neurons, such as the members of the SNAT, LAT, y+LAT, and ASC families of transporters. The SNAT family consists of the transporter isoforms SNAT3 and SNAT5 that are related to efflux from the astrocytic compartment, and SNAT1 and SNAT2 that are associated with glutamine uptake into the neuronal compartment. The isoforms SNAT7 and SNAT8 do not have their role completely understood, but they likely also participate in the GGC. The isoforms LAT2 and y+LAT2 facilitate the exchange of neutral amino acids and cationic amino acids (y+LAT2 isoform) and have been associated with glutamine efflux from astrocytes. ASCT2 is a Na+-dependent antiporter, the participation of which in the GGC also remains to be better characterized. All these isoforms are tightly regulated by transcriptional and translational mechanisms, which are induced by several determinants such as amino acid deprivation, hormones, pH, and the activity of different signaling pathways. Dysfunctional glutamine transporter activity has been associated with the pathophysiological mechanisms of certain neurologic diseases, such as Hepatic Encephalopathy and Manganism. However, there might also be other neuropathological conditions associated with an altered GGC, in which glutamine transporters are dysfunctional. Hence, it appears to be of critical importance that the physiological and pathological aspects of glutamine transporters are thoroughly investigated.
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32
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Zielińska M, Dąbrowska K, Hadera MG, Sonnewald U, Albrecht J. System N transporters are critical for glutamine release and modulate metabolic fluxes of glucose and acetate in cultured cortical astrocytes: changes induced by ammonia. J Neurochem 2015; 136:329-38. [DOI: 10.1111/jnc.13376] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 08/25/2015] [Accepted: 09/14/2015] [Indexed: 12/28/2022]
Affiliation(s)
- Magdalena Zielińska
- Department of Neurotoxicology; Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
| | - Katarzyna Dąbrowska
- Department of Neurotoxicology; Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
| | - Mussie Ghezu Hadera
- Department of Neuroscience; Faculty of Medicine; Norwegian University of Science and Technology (NTNU); Trondheim Norway
| | - Ursula Sonnewald
- Department of Neuroscience; Faculty of Medicine; Norwegian University of Science and Technology (NTNU); Trondheim Norway
- Department of Drug Design and Pharmacology; Faculty of Health and Medical Sciences; University of Copenhagen; Copenhagen Denmark
| | - Jan Albrecht
- Department of Neurotoxicology; Mossakowski Medical Research Centre; Polish Academy of Sciences; Warsaw Poland
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33
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Leke R, Escobar TDC, Rao KVR, Silveira TR, Norenberg MD, Schousboe A. Expression of glutamine transporter isoforms in cerebral cortex of rats with chronic hepatic encephalopathy. Neurochem Int 2015; 88:32-7. [PMID: 25842041 DOI: 10.1016/j.neuint.2015.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 03/13/2015] [Accepted: 03/18/2015] [Indexed: 01/19/2023]
Abstract
Hepatic encephalopathy (HE) is a neuropsychiatric disorder that occurs due to acute and chronic liver diseases, the hallmark of which is the increased levels of ammonia and subsequent alterations in glutamine synthesis, i.e. conditions associated with the pathophysiology of HE. Under physiological conditions, glutamine is fundamental for replenishment of the neurotransmitter pools of glutamate and GABA. The different isoforms of glutamine transporters play an important role in the transfer of this amino acid between astrocytes and neurons. A disturbance in the GABA biosynthetic pathways has been described in bile duct ligated (BDL) rats, a well characterized model of chronic HE. Considering that glutamine is important for GABA biosynthesis, altered glutamine transport and the subsequent glutamate/GABA-glutamine cycle efficacy might influence these pathways. Given this potential outcome, the aim of the present study was to investigate whether the expression of the glutamine transporters SAT1, SAT2, SN1 and SN2 would be affected in chronic HE. We verified that mRNA expression of the neuronal glutamine transporters SAT1 and SAT2 was found unaltered in the cerebral cortex of BDL rats. Similarly, no changes were found in the mRNA level for the astrocytic transporter SN1, whereas the gene expression of SN2 was increased by two-fold in animals with chronic HE. However, SN2 protein immuno-reactivity did not correspond with the increase in gene transcription since it remained unaltered. These data indicate that the expression of the glutamine transporter isoforms is unchanged during chronic HE, and thus likely not to participate in the pathological mechanisms related to the imbalance in the GABAergic neurotransmitter system observed in this neurologic condition.
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Affiliation(s)
- Renata Leke
- Experimental Hepatology and Gastroenterology Laboratory, Research Center of Hospital de Clínicas de Porto Alegre, Porto Alegre 90035-903, Brazil; Department of Pathology, University of Miami School of Medicine and Veterans Administration Medical Center, Miami, FL 33101, USA.
| | - Thayssa D C Escobar
- Experimental Hepatology and Gastroenterology Laboratory, Research Center of Hospital de Clínicas de Porto Alegre, Porto Alegre 90035-903, Brazil
| | - Kakulavarapu V Rama Rao
- Department of Pathology, University of Miami School of Medicine and Veterans Administration Medical Center, Miami, FL 33101, USA
| | - Themis Reverbel Silveira
- Experimental Hepatology and Gastroenterology Laboratory, Research Center of Hospital de Clínicas de Porto Alegre, Porto Alegre 90035-903, Brazil; Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Michael D Norenberg
- Department of Pathology, University of Miami School of Medicine and Veterans Administration Medical Center, Miami, FL 33101, USA
| | - Arne Schousboe
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen 2100, Denmark
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Butterworth RF. Pathogenesis of hepatic encephalopathy and brain edema in acute liver failure. J Clin Exp Hepatol 2015; 5:S96-S103. [PMID: 26041966 PMCID: PMC4442857 DOI: 10.1016/j.jceh.2014.02.004] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Accepted: 02/07/2014] [Indexed: 12/12/2022] Open
Abstract
Neuropathologic investigations in acute liver failure (ALF) reveal significant alterations to neuroglia consisting of swelling of astrocytes leading to cytotoxic brain edema and intracranial hypertension as well as activation of microglia indicative of a central neuroinflammatory response. Increased arterial ammonia concentrations in patients with ALF are predictors of patients at risk for the development of brain herniation. Molecular and spectroscopic techniques in ALF reveal alterations in expression of an array of genes coding for neuroglial proteins involved in cell volume regulation and mitochondrial function as well as in the transport of neurotransmitter amino acids and in the synthesis of pro-inflammatory cytokines. Liver-brain pro-inflammatory signaling mechanisms involving transduction of systemically-derived cytokines, ammonia neurotoxicity and exposure to increased brain lactate have been proposed. Mild hypothermia and N-Acetyl cysteine have both hepato-protective and neuro-protective properties in ALF. Potentially effective anti-inflammatory agents aimed at control of encephalopathy and brain edema in ALF include etanercept and the antibiotic minocycline, a potent inhibitor of microglial activation. Translation of these potentially-interesting findings to the clinic is anxiously awaited.
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Key Words
- ALF, acute liver failure
- ATP, adenosine triphosphate
- BBB, blood-brain barrier
- CCL2, chemokine ligand-2
- CMRO2, cerebral metabolic rate for oxygen
- CNS, central nervous system
- EEG, electroencephalography
- GABA, gamma-aminobutyric acid
- GFAP, glial fibrillary acidic protein
- IgG, immunoglobulin
- MRS, magnetic resonance spectroscopy
- NAC, N-Acetyl cysteine
- NMDA, N-methyl-d-aspartate
- SIRS, systemic inflammatory response syndrome
- SNATs, several neutral amino acid transport systems
- TLP, translocator protein
- TNFα, tumor necrosis factor alpha
- acute liver failure
- hepatic encephalopathy
- intracranial hypertension
- microglial activation
- neuroinflammation
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Affiliation(s)
- Roger F. Butterworth
- Neuroscience Research Unit, Hopital St-Luc (CHUM) and Department of Medicine, University of Montreal, Montreal, QC H2W 3J4, Canada,Address for correspondence: Roger F. Butterworth, Neuroscience Research Unit, Hospital St-Luc (CHUM) and Department of Medicine, University of Montreal, 1058 St Denis, Montreal, QC H2W 3J4, Canada. Tel.: +1 902 929 2470.
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Hägglund MGA, Hellsten SV, Bagchi S, Philippot G, Löfqvist E, Nilsson VCO, Almkvist I, Karlsson E, Sreedharan S, Tafreshiha A, Fredriksson R. Transport of L-glutamine, L-alanine, L-arginine and L-histidine by the neuron-specific Slc38a8 (SNAT8) in CNS. J Mol Biol 2014; 427:1495-1512. [PMID: 25451601 DOI: 10.1016/j.jmb.2014.10.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 09/30/2014] [Accepted: 10/17/2014] [Indexed: 11/19/2022]
Abstract
Glutamine transporters are important for regulating levels of glutamate and GABA in the brain. To date, six members of the SLC38 family (SNATs) have been characterized and functionally subdivided them into System A (SNAT1, SNAT2 and SNAT4) and System N (SNAT3, SNAT5 and SNAT7). Here we present the first functional characterization of SLC38A8, one of the previous orphan transporters from the family, and we suggest that the encoded protein should be named SNAT8 to adhere with the SNAT nomenclature. We show that SLC38A8 has preference for transporting L-glutamine, L-alanine, L-arginine, L-histidine and L-aspartate using a Na+-dependent transport mechanism and that the functional characteristics of SNAT8 have highest similarity to the known System A transporters. We also provide a comprehensive central nervous system expression profile in mouse brain for the Slc38a8 gene and the SNAT8 protein. We show that Slc38a8 (SNAT8) is expressed in all neurons, both excitatory and inhibitory, in mouse brain using in situ hybridization and immunohistochemistry. Furthermore, proximity ligation assay shows highly similar subcellular expression of SNAT7 and SNAT8. In conclusion, the neuronal SLC38A8 has a broad amino acid transport profile and is the first identified neuronal System A transporter. This suggests a key role of SNAT8 in the glutamine/glutamate (GABA) cycle in the brain.
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Affiliation(s)
- Maria G A Hägglund
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Sofie V Hellsten
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Sonchita Bagchi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Gaëtan Philippot
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Erik Löfqvist
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Victor C O Nilsson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Ingrid Almkvist
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Edvin Karlsson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Smitha Sreedharan
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Atieh Tafreshiha
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
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36
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Butterworth RF. Pathophysiology of brain dysfunction in hyperammonemic syndromes: The many faces of glutamine. Mol Genet Metab 2014; 113:113-7. [PMID: 25034052 DOI: 10.1016/j.ymgme.2014.06.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/16/2014] [Accepted: 06/16/2014] [Indexed: 12/31/2022]
Abstract
Ineffective hepatic clearance of excess ammonia in the form of urea, as occurs in urea cycle enzymopathies (UCDs) and in liver failure, leads to increases in circulating and tissue concentrations of glutamine and a positive correlation between brain glutamine and the severity of neurological symptoms. Studies using 1H/13C Nuclear Magnetic Resonance (NMR) spectroscopy reveal increased de novo synthesis of glutamine in the brain in acute liver failure (ALF) but increases of synthesis rates per se do not correlate with either the severity of encephalopathy or brain edema. Skeletal muscle becomes primarily responsible for removal of excess ammonia in liver failure and in UCDs, an adaptation that results from a post-translational induction of the glutamine synthetase (GS) gene. The importance of muscle in ammonia removal in hyperammonemia accounts for the resurgence of interest in maintaining adequate dietary protein and the use of agents aimed at the stimulation of muscle GS. Alternative or additional metabolic and regulatory pathways that impact on brain glutamine homeostasis in hyperammonemia include (i) glutamine deamination by the two isoforms of glutaminase, (ii) glutamine transamination leading to the production of the putative neurotoxin alpha-ketoglutaramate and (iii) alterations of high affinity astrocytic glutamine transporters (SNATs). Findings of reduced expression of the glutamine transporter SNAT-5 (responsible for glutamine clearance from the astrocyte) in ALF raise the possibility of "glutamine trapping" within these cells. Such a trapping mechanism could contribute to cytotoxic brain edema and to the imbalance between excitatory and inhibitory neurotransmission in this disorder.
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Affiliation(s)
- Roger F Butterworth
- Dept. of Medicine, University of Montreal and Neuroscience Research Unit, St-Luc Hospital (CHUM), Montreal, Qc, Canada
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37
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Expression of the System N transporter (SNAT5/SN2) during development indicates its plausible role in glutamatergic neurotransmission. Neurochem Int 2014; 73:166-71. [DOI: 10.1016/j.neuint.2013.11.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 11/20/2013] [Accepted: 11/27/2013] [Indexed: 01/09/2023]
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38
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New genetic biomarkers predicting azathioprine blood concentrations in combination therapy with 5-aminosalicylic acid. PLoS One 2014; 9:e95080. [PMID: 24762746 PMCID: PMC3999094 DOI: 10.1371/journal.pone.0095080] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 03/23/2014] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND AND AIMS Azathioprine (AZA) is widely used for the treatment of inflammatory bowel disease (IBD) patients. AZA is catabolized by thiopurine S-methyltransferase (TPMT), which exhibits genetic polymorphisms. It has also been reported that 5-aminosalicylic acid (5-ASA) inhibits TPMT activity, and that increased 6-thioguanine nucleotide (6-TGN, a metabolite of AZA) blood concentrations result in an increased number of ADRs. In this study, single nucleotide polymorphisms (SNPs) related to differential gene expression affecting AZA drug metabolism in combination therapy with 5-ASA were examined. METHODS To identify genetic biomarkers for the prediction of 6-TGN blood concentration, ExpressGenotyping analysis was used. ExpressGenotyping analysis is able to detect critical pharmacogenetic SNPs by analyzing drug-induced expression allelic imbalance (EAI) of premature RNA in HapMap lymphocytes. We collected blood samples on 38 patients with inflammatory bowel disease treated with AZA and corroboration of the obtained SNPs was attempted in clinical samples. RESULTS A large number of SNPs with AZA/5-ASA-induced EAI within the investigated HapMap lymphocytes was identified by ExpressGenotyping analysis. The respective SNPs were analyzed in IBD patients' blood samples. Among these SNPs, several that have not yet been described to be induced by AZA/5-ASA were found. SNPs within SLC38A9 showed a particular correlation with patients' 6-TGN blood concentrations. CONCLUSIONS Based on these results, ExpressGenotyping analysis and genotyping of patients appears to be a useful way to identify inter-individual differences in drug responses and ADRs to AZA/5-ASA. This study provides helpful information on genetic biomarkers for optimized AZA/5-ASA treatment of IBD patients.
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Bagchi S, Baomar HA, Al-Walai S, Al-Sadi S, Fredriksson R. Histological analysis of SLC38A6 (SNAT6) expression in mouse brain shows selective expression in excitatory neurons with high expression in the synapses. PLoS One 2014; 9:e95438. [PMID: 24752331 PMCID: PMC3994050 DOI: 10.1371/journal.pone.0095438] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 03/27/2014] [Indexed: 11/18/2022] Open
Abstract
SLC38A6 is one of the newly found members of the solute carrier 38 family consisting of total 11 members, of which only 6 have been characterized so far. Being the only glutamine transporter family expressed in the brain, this family of proteins are most probably involved in the regulation of the glutamate-glutamine cycle, responsible for preventing excitotoxicity. We used immunohistochemistry to show that SLC38A6 is primarily expressed in excitatory neurons and is not expressed in the astrocytes. Using proximity ligation assay, we have quantified the interactions of this SLC38 family protein with other proteins with known localization in the cells, showing that this transporter is expressed at the synapses. Moreover, this study has enabled us to come up with a model suggesting sub-cellular localization of SLC38A6 at the synaptic membrane of the excitatory neurons.
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Affiliation(s)
- Sonchita Bagchi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Hajar Ali Baomar
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Somar Al-Walai
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Saifaddin Al-Sadi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
- * E-mail:
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Glutamate transporters in the biology of malignant gliomas. Cell Mol Life Sci 2013; 71:1839-54. [PMID: 24281762 DOI: 10.1007/s00018-013-1521-z] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Revised: 10/22/2013] [Accepted: 11/11/2013] [Indexed: 12/11/2022]
Abstract
Malignant gliomas are relentless tumors that offer a dismal clinical prognosis. They develop many biological advantages that allow them to grow and survive in the unique environment of the brain. The glutamate transporters system x c (-) and excitatory amino acid transporters (EAAT) are emerging as key players in the biology and malignancy of these tumors. Gliomas manipulate glutamate transporter expression and function to alter glutamate homeostasis in the brain, which supports their own growth, invasion, and survival. As a consequence, malignant cells are able to quickly destroy and invade surrounding normal brain. Recent findings are painting a larger picture of these transporters in glioma biology, and as such are providing opportunities for clinical intervention for patients. This review will detail the current understanding of glutamate transporters in the biology of malignant gliomas and highlight some of the unique aspects of these tumors that make them so devastating and difficult to treat.
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41
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The SLC38 family of sodium-amino acid co-transporters. Pflugers Arch 2013; 466:155-72. [PMID: 24193407 DOI: 10.1007/s00424-013-1393-y] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/16/2013] [Accepted: 10/20/2013] [Indexed: 12/13/2022]
Abstract
Transporters of the SLC38 family are found in all cell types of the body. They mediate Na(+)-dependent net uptake and efflux of small neutral amino acids. As a result they are particularly expressed in cells that grow actively, or in cells that carry out significant amino acid metabolism, such as liver, kidney and brain. SLC38 transporters occur in membranes that face intercellular space or blood vessels, but do not occur in the apical membrane of absorptive epithelia. In the placenta, they play a significant role in the transfer of amino acids to the foetus. Members of the SLC38 family are highly regulated in response to amino acid depletion, hypertonicity and hormonal stimuli. SLC38 transporters play an important role in amino acid signalling and have been proposed to act as transceptors independent of their transport function. The structure of SLC38 transporters is characterised by the 5 + 5 inverted repeat fold, which is observed in a wide variety of transport proteins.
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Nissen-Meyer LSH, Chaudhry FA. Protein Kinase C Phosphorylates the System N Glutamine Transporter SN1 (Slc38a3) and Regulates Its Membrane Trafficking and Degradation. Front Endocrinol (Lausanne) 2013; 4:138. [PMID: 24106489 PMCID: PMC3788335 DOI: 10.3389/fendo.2013.00138] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 09/16/2013] [Indexed: 01/11/2023] Open
Abstract
The system N transporter SN1 (also known as SNAT3) is enriched on perisynaptic astroglial cell membranes. SN1 mediates electroneutral and bidirectional glutamine transport, and regulates the intracellular as well as the extracellular concentrations of glutamine. We hypothesize that SN1 participates in the glutamate/γ-aminobutyric acid (GABA)-glutamine cycle and regulates the amount of glutamine supplied to the neurons for replenishment of the neurotransmitter pools of glutamate and GABA. We also hypothesize that its activity on the plasma membrane is regulated by protein kinase C (PKC)-mediated phosphorylation and that SN1 activity has an impact on synaptic plasticity. This review discusses reports on the regulation of SN1 by PKC and presents a consolidated model for regulation and degradation of SN1 and the subsequent functional implications. As SN1 function is likely also regulated by PKC-mediated phosphorylation in peripheral organs, the same mechanisms may, thus, have impact on e.g., pH regulation in the kidney, urea formation in the liver, and insulin secretion in the pancreas.
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Affiliation(s)
- Lise Sofie H. Nissen-Meyer
- The Biotechnology Centre, University of Oslo, Oslo, Norway
- The Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- *Correspondence: Lise Sofie H. Nissen-Meyer and Farrukh Abbas Chaudhry, The Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1110 Blindern, 0317 Oslo, Norway e-mail: ;
| | - Farrukh Abbas Chaudhry
- The Biotechnology Centre, University of Oslo, Oslo, Norway
- The Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
- *Correspondence: Lise Sofie H. Nissen-Meyer and Farrukh Abbas Chaudhry, The Institute of Basic Medical Sciences, University of Oslo, P.O. Box 1110 Blindern, 0317 Oslo, Norway e-mail: ;
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Roles of changes in active glutamine transport in brain edema development during hepatic encephalopathy: an emerging concept. Neurochem Res 2013; 39:599-604. [PMID: 24072671 PMCID: PMC3926979 DOI: 10.1007/s11064-013-1141-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 08/20/2013] [Accepted: 08/22/2013] [Indexed: 12/12/2022]
Abstract
Excessive glutamine (Gln) synthesis in ammonia-overloaded astrocytes contributes to astrocytic swelling and brain edema, the major complication of hepatic encephalopathy (HE). Much of the newly formed Gln is believed to enter mitochondria, where it is recycled to ammonia, which causes mitochondrial dysfunction (a “Trojan horse” mode of action). A portion of Gln may increase osmotic pressure in astrocytes and the interstitial space, directly and independently contributing to brain tissue swelling. Here we discuss the possibility that altered functioning of Gln transport proteins located in the cellular or mitochondrial membranes, modulates the effects of increased Gln synthesis. Accumulation of excess Gln in mitochondria involves a carrier-mediated transport which is activated by ammonia. Studies on the expression of the cell membrane N-system transporters SN1 (SNAT3) and SN2 (SNAT5), which mediate Gln efflux from astrocytes rendered HE model-dependent effects. HE lowered the expression of SN1 at the RNA and protein level in the cerebral cortex (cc) in the thioacetamide (TAA) model of HE and the effect paralleled induction of cerebral cortical edema. Neither SN1 nor SN2 expression was affected by simple hyperammonemia, which produces no cc edema. TAA-induced HE is also associated with decreased expression of mRNA coding for the system A carriers SAT1 and SAT2, which stimulate Gln influx to neurons. Taken together, changes in the expression of Gln transporters during HE appear to favor retention of Gln in astrocytes and/or the interstitial space of the brain. HE may also affect arginine (Arg)/Gln exchange across the astrocytic cell membrane due to changes in the expression of the hybrid Arg/Gln transporter y+LAT2. Gln export from brain across the blood–brain barrier may be stimulated by HE via its increased exchange with peripheral tryptophan.
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Schiöth HB, Roshanbin S, Hägglund MGA, Fredriksson R. Evolutionary origin of amino acid transporter families SLC32, SLC36 and SLC38 and physiological, pathological and therapeutic aspects. Mol Aspects Med 2013; 34:571-85. [PMID: 23506890 DOI: 10.1016/j.mam.2012.07.012] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 06/25/2012] [Indexed: 10/27/2022]
Abstract
About 25% of all solute carriers (SLCs) are likely to transport amino acids as their primary substrate. One of the major phylogenetic clusters of amino acid transporters from the SLC family is the β-family, which is part of the PFAM APC clan. The β-family includes three SLC families, SLC32, SLC36 and SLC38 with one, four and eleven members in humans, respectively. The most well characterized genes within these families are the vesicular inhibitory amino acid transporter (VIAAT, SLC32A1), PAT1 (SLC36A1), PAT2 (SLC36A2), PAT4 (SLC36A4), SNAT1 (SLC38A1), SNAT2 (SLC38A2), SNAT3 (SLC38A3), and SNAT4 (SLC38A4). Here we review the structural characteristics and functional role of these transporters. We also mined the complete protein sequence datasets for nine different genomes to clarify the evolutionary history of the β-family of transporters. We show that all three main branches of the this family are found as far back as green algae suggesting that genes from these families existed in the early eukaryote before the split of animals and plants and that they are present in most animal species. We also address the potential of further drug development within this field highlighting the important role of these transporters in neurotransmission and transport of amino acids as nutrients.
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Affiliation(s)
- Helgi B Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden.
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Martínez-Lozada Z, Guillem AM, Flores-Méndez M, Hernández-Kelly LC, Vela C, Meza E, Zepeda RC, Caba M, Rodríguez A, Ortega A. GLAST/EAAT1-induced glutamine release via SNAT3 in Bergmann glial cells: evidence of a functional and physical coupling. J Neurochem 2013; 125:545-54. [PMID: 23418736 DOI: 10.1111/jnc.12211] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 10/11/2012] [Accepted: 02/15/2013] [Indexed: 01/26/2023]
Abstract
Glutamate, the major excitatory transmitter in the vertebrate brain, is removed from the synaptic cleft by a family of sodium-dependent glutamate transporters profusely expressed in glial cells. Once internalized, it is metabolized by glutamine synthetase to glutamine and released to the synaptic space through sodium-dependent neutral amino acid carriers of the N System (SNAT3/slc38a3/SN1, SNAT5/slc38a5/SN2). Glutamine is then taken up by neurons completing the so-called glutamate/glutamine shuttle. Despite of the fact that this coupling was described decades ago, it is only recently that the biochemical framework of this shuttle has begun to be elucidated. Using the established model of cultured cerebellar Bergmann glia cells, we sought to characterize the functional and physical coupling of glutamate uptake and glutamine release. A time-dependent Na⁺-dependent glutamate/aspartate transporter/EAAT1-induced System N-mediated glutamine release could be demonstrated. Furthermore, D-aspartate, a specific glutamate transporter ligand, was capable of enhancing the co-immunoprecipitation of Na⁺-dependent glutamate/aspartate transporter and Na⁺-dependent neutral amino acid transporter 3, whereas glutamine tended to reduce this association. Our results suggest that glial cells surrounding glutamatergic synapses may act as sensors of neuron-derived glutamate through their contribution to the neurotransmitter turnover.
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Affiliation(s)
- Zila Martínez-Lozada
- Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México D.F, México
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Bosoi CR, Rose CF. Brain edema in acute liver failure and chronic liver disease: similarities and differences. Neurochem Int 2013; 62:446-57. [PMID: 23376027 DOI: 10.1016/j.neuint.2013.01.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 01/11/2013] [Accepted: 01/16/2013] [Indexed: 12/12/2022]
Abstract
Hepatic encephalopathy (HE) is a complex neuropsychiatric syndrome that typically develops as a result of acute liver failure or chronic liver disease. Brain edema is a common feature associated with HE. In acute liver failure, brain edema contributes to an increase in intracranial pressure, which can fatally lead to brain stem herniation. In chronic liver disease, intracranial hypertension is rarely observed, even though brain edema may be present. This discrepancy in the development of intracranial hypertension in acute liver failure versus chronic liver disease suggests that brain edema plays a different role in relation to the onset of HE. Furthermore, the pathophysiological mechanisms involved in the development of brain edema in acute liver failure and chronic liver disease are dissimilar. This review explores the types of brain edema, the cells, and pathogenic factors involved in its development, while emphasizing the differences in acute liver failure versus chronic liver disease. The implications of brain edema developing as a neuropathological consequence of HE, or as a cause of HE, are also discussed.
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Affiliation(s)
- Cristina R Bosoi
- Neuroscience Research Unit, Hôpital Saint-Luc (CRCHUM), Université de Montréal, Québec, Canada
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Hamdani EH, Gudbrandsen M, Bjørkmo M, Chaudhry FA. The system N transporter SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors. Glia 2012; 60:1671-83. [PMID: 22821889 DOI: 10.1002/glia.22386] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Revised: 06/14/2012] [Accepted: 06/15/2012] [Indexed: 12/28/2022]
Abstract
Activation of NMDA receptor requires two co-agonists, glutamate and glycine. Despite its intrinsic role in brain functions molecular mechanisms involved in glutamate replenishment and identification of the origin of glycine have eluded characterization. We have performed direct measurements of glycine flux by SN2 (Slc38a5; also known as SNAT5), executed extensive electrophysiological characterization as well as implemented ratiometric analyses to show that SN2 transport resembles SN1 in mechanism but differ in functional implications. We report that rat SN2 mediates electroneutral and bidirectional transport of glutamine and glycine at perisynaptic astroglial membranes. Sophisticated coupled and uncoupled movements of H(+) differentially associate with glutamine and glycine transport by SN2 and regulate pH(i) and the release mode of the transporter. Consequently, SN2 doubles as a transmitter precursor furnisher and a potential regulator of NMDA receptors.
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Affiliation(s)
- El Hassan Hamdani
- The Biotechnology Center and Center for Molecular Biology and Neuroscience, University of Oslo, Blindern, Oslo, Norway
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Uwechue NM, Marx MC, Chevy Q, Billups B. Activation of glutamate transport evokes rapid glutamine release from perisynaptic astrocytes. J Physiol 2012; 590:2317-31. [PMID: 22411007 DOI: 10.1113/jphysiol.2011.226605] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Stimulation of astrocytes by neuronal activity and the subsequent release of neuromodulators is thought to be an important regulator of synaptic communication. In this study we show that astrocytes juxtaposed to the glutamatergic calyx of Held synapse in the rat medial nucleus of the trapezoid body (MNTB) are stimulated by the activation of glutamate transporters and consequently release glutamine on a very rapid timescale. MNTB principal neurones express electrogenic system A glutamine transporters, and were exploited as glutamine sensors in this study. By simultaneous whole-cell voltage clamping astrocytes and neighbouring MNTB neurones in brainstem slices, we show that application of the excitatory amino acid transporter (EAAT) substrate d-aspartate stimulates astrocytes to rapidly release glutamine, which is detected by nearby MNTB neurones. This release is significantly reduced by the toxins L-methionine sulfoximine and fluoroacetate, which reduce glutamine concentrations specifically in glial cells. Similarly, glutamine release was also inhibited by localised inactivation of EAATs in individual astrocytes, using internal DL-threo-β-benzyloxyaspartic acid (TBOA) or dissipating the driving force by modifying the patch-pipette solution. These results demonstrate that astrocytes adjacent to glutamatergic synapses can release glutamine in a temporally precise, controlled manner in response to glial glutamate transporter activation. Since glutamine can be used by neurones as a precursor for glutamate and GABA synthesis, this represents a potential feedback mechanism by which astrocytes can respond to synaptic activation and react in a way that sustains or enhances further communication. This would therefore represent an additional manifestation of the tripartite relationship between synapses and astrocytes.
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Affiliation(s)
- Nneka M Uwechue
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, UK
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Pathogenesis of hepatic encephalopathy and brain edema in acute liver failure: role of glutamine redefined. Neurochem Int 2012; 60:690-6. [PMID: 22382077 DOI: 10.1016/j.neuint.2012.02.001] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 02/02/2012] [Accepted: 02/04/2012] [Indexed: 11/23/2022]
Abstract
Acute liver failure (ALF) is characterized neuropathologically by cytotoxic brain edema and biochemically by increased brain ammonia and its detoxification product, glutamine. The osmotic actions of increased glutamine synthesis in astrocytes are considered to be causally related to brain edema and its complications (intracranial hypertension, brain herniation) in ALF. However studies using multinuclear (1)H- and (13)C-NMR spectroscopy demonstrate that neither brain glutamine concentrations per se nor brain glutamine synthesis rates correlate with encephalopathy grade or the presence of brain edema in ALF. An alternative mechanism is now proposed whereby the newly synthesized glutamine is trapped within the astrocyte as a consequence of down-regulation of its high affinity glutamine transporter SNAT5 in ALF. Restricted transfer out of the cell rather than increased synthesis within the cell could potentially explain the cell swelling/brain edema in ALF. Moreover, the restricted transfer of glutamine from the astrocyte to the adjacent glutamatergic nerve terminal (where glutamine serves as immediate precursor for the releasable/transmitter pool of glutamate) could result in decreased excitatory transmission and excessive neuroinhibition that is characteristic of encephalopathy in ALF. Paradoxically, in spite of renewed interest in arterial ammonia as a predictor of raised intracranial pressure and brain herniation in ALF, ammonia-lowering agents aimed at reduction of ammonia production in the gut have so far been shown to be of limited value in the prevention of these cerebral consequences. Mild hypothermia, shown to prevent brain edema and intracranial hypertension in both experimental and human ALF, does so independent of effects on brain glutamine synthesis; whether or not hypothermia restores expression levels of SNAT5 in ALF awaits further studies. While inhibitors of brain glutamine synthesis such as methionine sulfoximine, have been proposed for the prevention of brain edema in ALF, potential adverse effects have so far limited their applicability.
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Abstract
Glutamine (Gln) is found abundantly in the central nervous system (CNS) where it participates in a variety of metabolic pathways. Its major role in the brain is that of a precursor of the neurotransmitter amino acids: the excitatory amino acids, glutamate (Glu) and aspartate (Asp), and the inhibitory amino acid, γ-amino butyric acid (GABA). The precursor-product relationship between Gln and Glu/GABA in the brain relates to the intercellular compartmentalization of the Gln/Glu(GABA) cycle (GGC). Gln is synthesized from Glu and ammonia in astrocytes, in a reaction catalyzed by Gln synthetase (GS), which, in the CNS, is almost exclusively located in astrocytes (Martinez-Hernandez et al., 1977). Newly synthesized Gln is transferred to neurons and hydrolyzed by phosphate-activated glutaminase (PAG) to give rise to Glu, a portion of which may be decarboxylated to GABA or transaminated to Asp. There is a rich body of evidence which indicates that a significant proportion of the Glu, Asp and GABA derived from Gln feed the synaptic, neurotransmitter pools of the amino acids. Depolarization-induced-, calcium- and PAG activity-dependent releases of Gln-derived Glu, GABA and Asp have been observed in CNS preparations in vitro and in the brain in situ. Immunocytochemical studies in brain slices have documented Gln transfer from astrocytes to neurons as well as the location of Gln-derived Glu, GABA and Asp in the synaptic terminals. Patch-clamp studies in brain slices and astrocyte/neuron co-cultures have provided functional evidence that uninterrupted Gln synthesis in astrocytes and its transport to neurons, as mediated by specific carriers, promotes glutamatergic and GABA-ergic transmission. Gln entry into the neuronal compartment is facilitated by its abundance in the extracellular spaces relative to other amino acids. Gln also appears to affect neurotransmission directly by interacting with the NMDA class of Glu receptors. Transmission may also be modulated by alterations in cell membrane polarity related to the electrogenic nature of Gln transport or to uncoupled ion conductances in the neuronal or glial cell membranes elicited by Gln transporters. In addition, Gln appears to modulate the synthesis of the gaseous messenger, nitric oxide (NO), by controlling the supply to the cells of its precursor, arginine. Disturbances of Gln metabolism and/or transport contribute to changes in Glu-ergic or GABA-ergic transmission associated with different pathological conditions of the brain, which are best recognized in epilepsy, hepatic encephalopathy and manganese encephalopathy.
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