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Birolo L, Sacchi S, Smaldone G, Molla G, Leo G, Caldinelli L, Pirone L, Eliometri P, Di Gaetano S, Orefice I, Pedone E, Pucci P, Pollegioni L. Regulating levels of the neuromodulatord-serine in human brain: structural insight into pLG72 andd-amino acid oxidase interaction. FEBS J 2016; 283:3353-70. [DOI: 10.1111/febs.13809] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 06/28/2016] [Accepted: 07/08/2016] [Indexed: 12/27/2022]
Affiliation(s)
- Leila Birolo
- Dipartimento di Scienze Chimiche; Università degli Studi di Napoli Federico II; Napoli Italy
| | - Silvia Sacchi
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche “The Protein Factory”; Politecnico di Milano and Università degli studi dell'Insubria; Milano Italy
| | | | - Gianluca Molla
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche “The Protein Factory”; Politecnico di Milano and Università degli studi dell'Insubria; Milano Italy
| | - Gabriella Leo
- Dipartimento di Scienze Chimiche; Università degli Studi di Napoli Federico II; Napoli Italy
| | - Laura Caldinelli
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche “The Protein Factory”; Politecnico di Milano and Università degli studi dell'Insubria; Milano Italy
| | - Luciano Pirone
- Italian Research National Council; Institute of Biostructures and Bioimaging; Napoli Italy
| | - Patrick Eliometri
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli studi dell'Insubria; Varese Italy
| | - Sonia Di Gaetano
- Italian Research National Council; Institute of Biostructures and Bioimaging; Napoli Italy
| | - Ida Orefice
- Dipartimento di Scienze Chimiche; Università degli Studi di Napoli Federico II; Napoli Italy
| | - Emilia Pedone
- Italian Research National Council; Institute of Biostructures and Bioimaging; Napoli Italy
| | - Piero Pucci
- Dipartimento di Scienze Chimiche; Università degli Studi di Napoli Federico II; Napoli Italy
| | - Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche “The Protein Factory”; Politecnico di Milano and Università degli studi dell'Insubria; Milano Italy
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Raider K, Ma D, Harris JL, Fuentes I, Rogers RS, Wheatley JL, Geiger PC, Yeh HW, Choi IY, Brooks WM, Stanford JA. A high fat diet alters metabolic and bioenergetic function in the brain: A magnetic resonance spectroscopy study. Neurochem Int 2016; 97:172-80. [PMID: 27125544 PMCID: PMC4900919 DOI: 10.1016/j.neuint.2016.04.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 04/18/2016] [Accepted: 04/20/2016] [Indexed: 11/18/2022]
Abstract
Diet-induced obesity and associated metabolic effects can lead to neurological dysfunction and increase the risk of developing Alzheimer's disease (AD) and Parkinson's disease (PD). Despite these risks, the effects of a high-fat diet on the central nervous system are not well understood. To better understand the mechanisms underlying the effects of high fat consumption on brain regions affected by AD and PD, we used proton magnetic resonance spectroscopy ((1)H-MRS) to measure neurochemicals in the hippocampus and striatum of rats fed a high fat diet vs. normal low fat chow. We detected lower concentrations of total creatine (tCr) and a lower glutamate-to-glutamine ratio in the hippocampus of high fat rats. Additional effects observed in the hippocampus of high fat rats included higher N-acetylaspartylglutamic acid (NAAG), and lower myo-inositol (mIns) and serine (Ser) concentrations. Post-mortem tissue analyses revealed lower phosphorylated AMP-activated protein kinase (pAMPK) in the striatum but not in the hippocampus of high fat rats. Hippocampal pAMPK levels correlated significantly with tCr, aspartate (Asp), phosphoethanolamine (PE), and taurine (Tau), indicating beneficial effects of AMPK activation on brain metabolic and energetic function, membrane turnover, and edema. A negative correlation between pAMPK and glucose (Glc) indicates a detrimental effect of brain Glc on cellular energy response. Overall, these changes indicate alterations in neurotransmission and in metabolic and bioenergetic function in the hippocampus and in the striatum of rats fed a high fat diet.
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Affiliation(s)
- Kayla Raider
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Delin Ma
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Janna L Harris
- Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Hoglund Brain Imaging Center, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Isabella Fuentes
- Department of Anatomy & Cell Biology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Robert S Rogers
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Joshua L Wheatley
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Paige C Geiger
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Hung-Wen Yeh
- Department of Biostatistics, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - In-Young Choi
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Hoglund Brain Imaging Center, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - William M Brooks
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Hoglund Brain Imaging Center, University of Kansas Medical Center, Kansas City, KS 66160, USA; Kansas Intellectual and Developmental Disabilities Research Center, University of Kansas Medical Center, Kansas City, KS 66160, USA; University of Kansas Alzheimer's Disease Center, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - John A Stanford
- Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA; Kansas Intellectual and Developmental Disabilities Research Center, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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Abstract
Homochirality is fundamental for life. L-Amino acids are exclusively used as substrates for the polymerization and formation of peptides and proteins in living systems. However, D- amino acids were recently detected in various living organisms, including mammals. Of these D-amino acids, D-serine has been most extensively studied. D-Serine was found to play an important role as a neurotransmitter in the human central nervous system (CNS) by binding to the N-methyl- D-aspartate receptor (NMDAr). D-Serine binds with high affinity to a co-agonist site at the NMDAr and, along with glutamate, mediates several vital physiological and pathological processes, including NMDAr transmission, synaptic plasticity and neurotoxicity. Therefore, a key role for D-serine as a determinant of NMDAr mediated neurotransmission in mammalian CNS has been suggested. In this context, we review the known functions of D-serine in human physiology, such as CNS development, and pathology, such as neuro-psychiatric and neurodegenerative diseases related to NMDAr dysfunction.
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Ultimate Translation: Developing Therapeutics Targeting on N-Methyl-d-Aspartate Receptor. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2016; 76:257-309. [PMID: 27288080 DOI: 10.1016/bs.apha.2016.03.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
N-Methyl-d-aspartate receptors (NMDARs) are broadly distributed in the central nervous system (CNS), where they mediate excitatory signaling. NMDAR-mediated neurotransmission (NMDARMN) is the molecular engine of learning, memory and cognition, which are the basis for high cortical function. NMDARMN is also critically involved in the development and plasticity of CNS. Due to its essential and critical role, either over- or under-activation of NMDARMN can contribute substantially to the development of CNS disorders. The involvement of NMDARMN has been demonstrated in a variety of CNS disorders, including schizophrenia, depression, posttraumatic stress disorder, aging, mild cognitive impairment and Alzheimer's dementia, amyotrophic lateral sclerosis, and anti-NMDAR encephalitis. Several targets to "correct" or "reset" the NMDARMN in these CNS disorders have been identified and confirmed. With analogy to aminergic treatments, these targets include the glycine/d-serine co-agonist site, channel ionophore, glycine transporter-1, and d-amino acid oxidase. It is still early days in terms of developing novel therapeutics targeting the NMDAR. However, agents modulating NMDARMN hold promise as the next generation of CNS therapeutics.
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Cao S, Xiao Z, Sun M, Li Y. D-serine in the midbrain periaqueductal gray contributes to morphine tolerance in rats. Mol Pain 2016; 12:12/0/1744806916646786. [PMID: 27175014 PMCID: PMC4956000 DOI: 10.1177/1744806916646786] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 04/04/2016] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND The N-methyl-D-aspartate subtype of glutamate receptor plays a critical role in morphine tolerance. D-serine, a co-agonist of N-methyl-D-aspartate receptor, participates in many physiological and pathophysiological processes via regulating N-methyl-D-aspartate receptor activation. The purinergic P2X7 receptor activation can induce the D-serine release in the central nervous system. This study aimed to investigate the role of the ventrolateral midbrain periaqueductal gray D-serine in the mechanism of morphine tolerance in rats. The development of morphine tolerance was induced in normal adult male Sprague-Dawley rats through subcutaneous injection of morphine (10 mg/kg). The analgesic effect of morphine (5 mg/kg, i.p.) was assessed by measuring mechanical withdrawal thresholds in rats with an electronic von Frey anesthesiometer. The D-serine concentration and serine racemase expression levels in the ventrolateral midbrain periaqueductal gray were evaluated through enzyme-linked immunosorbent assay and Western blot analysis, respectively. The effects of intra-ventrolateral midbrain periaqueductal gray injections of the D-serine degrading enzyme D-amino acid oxidase and antisense oligodeoxynucleotide targeting the P2X7 receptor on chronic morphine-treated rats were also explored. RESULTS We found that repeated morphine administrations decreased the antinociceptive potency of morphine evidenced by the percent changes in mechanical pain threshold in rats. By contrast, the D-serine contents and the expression levels of the serine racemase protein were upregulated in the ventrolateral midbrain periaqueductal gray in morphine-tolerant rats. The development of morphine tolerance was markedly alleviated by intra-ventrolateral midbrain periaqueductal gray injections of D-amino acid oxidase or antisense oligodeoxynucleotide targeting the P2X7 receptor. CONCLUSIONS Our data indicate that the development of antinociceptive tolerance to morphine is partially mediated by ventrolateral midbrain periaqueductal gray D-serine content, and the activation of the ventrolateral midbrain periaqueductal gray P2X7 receptor is an essential prelude to D-serine release. These results suggest that a cascade involving P2X7 receptor-D-serine-N-methyl-D-aspartate receptor mediated signaling pathway in the supraspinal mechanism of morphine tolerance.
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Affiliation(s)
- Song Cao
- Department of Pain Medicine, Affiliated Hospital of Zunyi Medical University, Zunyi, Guizhou, China Guizhou Key Laboratory of Anesthesia and Organ Protection, Zunyi Medical University, Zunyi, Guizhou, China
| | - Zhi Xiao
- Research Center for Medicine and Biology, Zunyi Medical University, Zunyi, Guizhou, China
| | - Mengjie Sun
- Graduate School, Zunyi Medical University, Zunyi, Guizhou, China
| | - Youyan Li
- Graduate School, Zunyi Medical University, Zunyi, Guizhou, China
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Kennedy BE, Hundert AS, Goguen D, Weaver ICG, Karten B. Presymptomatic Alterations in Amino Acid Metabolism and DNA Methylation in the Cerebellum of a Murine Model of Niemann-Pick Type C Disease. THE AMERICAN JOURNAL OF PATHOLOGY 2016; 186:1582-97. [PMID: 27083515 DOI: 10.1016/j.ajpath.2016.02.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/2014] [Revised: 02/08/2016] [Accepted: 02/16/2016] [Indexed: 10/21/2022]
Abstract
The fatal neurodegenerative disorder Niemann-Pick type C (NPC) is caused in most cases by mutations in NPC1, which encodes the late endosomal NPC1 protein. Loss of NPC1 disrupts cholesterol trafficking from late endosomes to the endoplasmic reticulum and plasma membrane, causing cholesterol accumulation in late endosomes/lysosomes. Neurons are particularly vulnerable to this cholesterol trafficking defect, but the pathogenic mechanisms through which NPC1 deficiency causes neuronal dysfunction remain largely unknown. Herein, we have investigated amino acid metabolism in cerebella of NPC1-deficient mice at different stages of NPC disease. Imbalances in amino acid metabolism were evident from increased branched chain amino acid and asparagine levels and altered expression of key enzymes of glutamine/glutamate metabolism in presymptomatic and early symptomatic NPC1-deficient cerebellum. Increased levels of several amino acid intermediates of one-carbon metabolism indicated disturbances in folate and methylation pathways. Alterations in DNA methylation were apparent in decreased expression of DNA methyltransferase 3a and methyl-5'-cytosine-phosphodiester-guanine-domain binding proteins, reduced 5-methylcytosine immunoreactivity in the molecular and Purkinje cell layers, demethylation of genome-wide repetitive LINE-1 elements, and hypermethylation in specific promoter regions of single-copy genes in NPC1-deficient cerebellum at early stages of the disease. Alterations in amino acid metabolism and epigenetic changes in the cerebellum at presymptomatic stages of NPC disease represent previously unrecognized mechanisms of NPC pathogenesis.
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Affiliation(s)
- Barry E Kennedy
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Amos S Hundert
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Donna Goguen
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Ian C G Weaver
- Department of Psychology and Neuroscience, Dalhousie University, Halifax, Nova Scotia, Canada.
| | - Barbara Karten
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
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The NMDA Receptor and Schizophrenia: From Pathophysiology to Treatment. ADVANCES IN PHARMACOLOGY 2016; 76:351-82. [PMID: 27288082 DOI: 10.1016/bs.apha.2016.01.006] [Citation(s) in RCA: 181] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Schizophrenia is a severe mental illness that affects almost 1% of the population worldwide. Even though the etiology of schizophrenia is uncertain, it is believed to be a neurodevelopmental disorder that results from a combination of environmental insults and genetic vulnerabilities. Over the past 20 years, there has been a confluence of evidence from many research disciplines pointing to alterations in excitatory signaling, particularly involving hypofunction of the N-methyl-d-aspartate receptor (NMDAR), as a key contributor to the schizophrenia disease process. This review describes the structure-function relationship of the NMDAR channel and how the glycine modulatory site acts as an important regulator of its activity. In addition, this review highlights the genetic, pharmacologic, and biochemical evidence supporting the hypothesis that NMDAR hypofunction contributes to the pathophysiology of schizophrenia. Finally, this chapter highlights some of the most recent and promising pharmacological strategies that are designed to either, directly or indirectly, augment NMDAR function in an effort to treat the cognitive and negative symptoms of schizophrenia that are not helped by currently available medications.
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Lin H, Jacobi AA, Anderson SA, Lynch DR. D-Serine and Serine Racemase Are Associated with PSD-95 and Glutamatergic Synapse Stability. Front Cell Neurosci 2016; 10:34. [PMID: 26941605 PMCID: PMC4766304 DOI: 10.3389/fncel.2016.00034] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 01/31/2016] [Indexed: 12/20/2022] Open
Abstract
D-serine is an endogenous coagonist at the glycine site of synaptic NMDA receptors (NMDARs), synthesized by serine racemase (SR) through conversion of L-serine. It is crucial for synaptic plasticity and is implicated in schizophrenia. Our previous studies demonstrated specific loss of SR, D-serine-responsive synaptic NMDARs, and glutamatergic synapses in cortical neurons lacking α7 nicotinic acetylcholine receptors, which promotes glutamatergic synapse formation and maturation during development. We thus hypothesize that D-serine and SR (D-serine/SR) are associated with glutamatergic synaptic development. Using morphological and molecular studies in cortical neuronal cultures, we demonstrate that D-serine/SR are associated with PSD-95 and NMDARs in postsynaptic neurons and with glutamatergic synapse stability during synaptic development. Endogenous D-serine and SR colocalize with PSD-95, but not presynaptic vesicular glutamate transporter 1 (VGLUT1), in glutamatergic synapses of cultured cortical neurons. Low-density astrocytes in cortical neuronal cultures lack SR expression but contain enriched D-serine in large vesicle-like structures, suggesting possible synthesis of D-serine in postsynaptic neurons and storage in astrocytes. More interestingly, endogenous D-serine and SR colocalize with PSD-95 in the postsynaptic terminals of glutamatergic synapses during early and late synaptic development, implicating involvement of D-serine/SR in glutamatergic synaptic development. Exogenous application of D-serine enhances the interactions of SR with PSD-95 and NR1, and increases the number of VGLUT1- and PSD-95-positive glutamatergic synapses, suggesting that exogenous D-serine enhances postsynaptic SR/PSD-95 signaling and stabilizes glutamatergic synapses during cortical synaptic development. This is blocked by NMDAR antagonist 2-amino-5-phosphonopentanoic acid (AP5) and 7-chlorokynurenic acid (7-CK), a specific antagonist at the glycine site of NMDARs, demonstrating that D-serine effects are mediated through postsynaptic NMDARs. Conversely, exogenous application of glycine has no such effects, suggesting D-serine, rather than glycine, modulates postsynaptic events. Taken together, our findings demonstrate that D-serine/SR are associated with PSD-95 and NMDARs in postsynaptic neurons and with glutamatergic synapse stability during synaptic development, implicating D-serine/SR as regulators of cortical synaptic and circuit development.
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Affiliation(s)
- Hong Lin
- Department of Pediatrics and Neurology, The Children's Hospital of Philadelphia Philadelphia, PA, USA
| | - Ariel A Jacobi
- Department of Pediatrics and Neurology, The Children's Hospital of PhiladelphiaPhiladelphia, PA, USA; University of Pennsylvania School of Arts and SciencesPhiladelphia, PA, USA
| | - Stewart A Anderson
- Department of Child and Adolescent Psychiatry and Behavioral Services, The Children's Hospital of PhiladelphiaPhiladelphia, PA, USA; University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA
| | - David R Lynch
- Department of Pediatrics and Neurology, The Children's Hospital of PhiladelphiaPhiladelphia, PA, USA; University of Pennsylvania Perelman School of MedicinePhiladelphia, PA, USA
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Role of Astrocytes in Central Respiratory Chemoreception. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 949:109-145. [PMID: 27714687 DOI: 10.1007/978-3-319-40764-7_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Astrocytes perform various homeostatic functions in the nervous system beyond that of a supportive or metabolic role for neurons. A growing body of evidence indicates that astrocytes are crucial for central respiratory chemoreception. This review presents a classical overview of respiratory central chemoreception and the new evidence for astrocytes as brainstem sensors in the respiratory response to hypercapnia. We review properties of astrocytes for chemosensory function and for modulation of the respiratory network. We propose that astrocytes not only mediate between CO2/H+ levels and motor responses, but they also allow for two emergent functions: (1) Amplifying the responses of intrinsic chemosensitive neurons through feedforward signaling via gliotransmitters and; (2) Recruiting non-intrinsically chemosensitive cells thanks to volume spreading of signals (calcium waves and gliotransmitters) to regions distant from the CO2/H+ sensitive domains. Thus, astrocytes may both increase the intensity of the neuron responses at the chemosensitive sites and recruit of a greater number of respiratory neurons to participate in the response to hypercapnia.
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Kumar A. NMDA Receptor Function During Senescence: Implication on Cognitive Performance. Front Neurosci 2015; 9:473. [PMID: 26732087 PMCID: PMC4679982 DOI: 10.3389/fnins.2015.00473] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2015] [Accepted: 11/25/2015] [Indexed: 12/13/2022] Open
Abstract
N-methyl-D-aspartate (NMDA) receptors, a family of L-glutamate receptors, play an important role in learning and memory, and are critical for spatial memory. These receptors are tetrameric ion channels composed of a family of related subunits. One of the hallmarks of the aging human population is a decline in cognitive function; studies in the past couple of years have demonstrated deterioration in NMDA receptor subunit expression and function with advancing age. However, a direct relationship between impaired memory function and a decline in NMDA receptors is still ambiguous. Recent studies indicate a link between an age-associated NMDA receptor hypofunction and memory impairment and provide evidence that age-associated enhanced oxidative stress might be contributing to the alterations associated with senescence. However, clear evidence is still deficient in demonstrating the underlying mechanisms and a relationship between age-associated impaired cognitive faculties and NMDA receptor hypofunction. The current review intends to present an overview of the research findings regarding changes in expression of various NMDA receptor subunits and deficits in NMDA receptor function during senescence and its implication in age-associated impaired hippocampal-dependent memory function.
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Affiliation(s)
- Ashok Kumar
- Department of Neuroscience, Evelyn F. and William L. McKnight Brain Institute, University of Florida Gainesville, FL, USA
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61
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Errico F, Mothet JP, Usiello A. d-Aspartate: An endogenous NMDA receptor agonist enriched in the developing brain with potential involvement in schizophrenia. J Pharm Biomed Anal 2015; 116:7-17. [DOI: 10.1016/j.jpba.2015.03.024] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 03/11/2015] [Accepted: 03/23/2015] [Indexed: 12/14/2022]
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Mothet JP, Le Bail M, Billard JM. Time and space profiling of NMDA receptor co-agonist functions. J Neurochem 2015; 135:210-25. [DOI: 10.1111/jnc.13204] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 05/12/2015] [Accepted: 06/02/2015] [Indexed: 02/01/2023]
Affiliation(s)
- Jean-Pierre Mothet
- Team ‘Gliotransmission and Synaptopathies’; Aix-Marseille Université; CNRS; CRN2M UMR7286; Marseille France
| | - Matildé Le Bail
- Team ‘Gliotransmission and Synaptopathies’; Aix-Marseille Université; CNRS; CRN2M UMR7286; Marseille France
| | - Jean-Marie Billard
- Center of Psychiatry and Neuroscience; University Paris Descartes; Sorbonne Paris City; UMR 894; Paris France
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Rama Rao KV, Kielian T. Neuron-astrocyte interactions in neurodegenerative diseases: Role of neuroinflammation. ACTA ACUST UNITED AC 2015; 6:245-263. [PMID: 26543505 DOI: 10.1111/cen3.12237] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Selective neuron loss in discrete brain regions is a hallmark of various neurodegenerative disorders, although the mechanisms responsible for this regional vulnerability of neurons remain largely unknown. Earlier studies attributed neuron dysfunction and eventual loss during neurodegenerative diseases as exclusively cell autonomous. Although cell-intrinsic factors are one critical aspect in dictating neuron death, recent evidence also supports the involvement of other central nervous system cell types in propagating non-cell autonomous neuronal injury during neurodegenerative diseases. One such example is astrocytes, which support neuronal and synaptic function, but can also contribute to neuroinflammatory processes through robust chemokine secretion. Indeed, aberrations in astrocyte function have been shown to negatively impact neuronal integrity in several neurological diseases. The present review focuses on neuroinflammatory paradigms influenced by neuron-astrocyte cross-talk in the context of select neurodegenerative diseases.
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Affiliation(s)
- Kakulavarapu V Rama Rao
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, USA
| | - Tammy Kielian
- Department of Pathology and Microbiology, University of Nebraska Medical Center, Omaha, Nebraska, USA
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Zorec R, Verkhratsky A, Rodríguez JJ, Parpura V. Astrocytic vesicles and gliotransmitters: Slowness of vesicular release and synaptobrevin2-laden vesicle nanoarchitecture. Neuroscience 2015; 323:67-75. [PMID: 25727638 DOI: 10.1016/j.neuroscience.2015.02.033] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Revised: 02/01/2015] [Accepted: 02/18/2015] [Indexed: 12/30/2022]
Abstract
Neurotransmitters released at synapses activate neighboring astrocytes, which in turn, modulate neuronal activity by the release of diverse neuroactive substances that include classical neurotransmitters such as glutamate, GABA or ATP. Neuroactive substances are released from astrocytes through several distinct molecular mechanisms, for example, by diffusion through membrane channels, by translocation via plasmalemmal transporters or by vesicular exocytosis. Vesicular release regulated by a stimulus-mediated increase in cytosolic calcium involves soluble N-ethyl maleimide-sensitive fusion protein attachment protein receptor (SNARE)-dependent merger of the vesicle membrane with the plasmalemma. Up to 25 molecules of synaptobrevin 2 (Sb2), a SNARE complex protein, reside at a single astroglial vesicle; an individual neuronal, i.e. synaptic, vesicle contains ∼70 Sb2 molecules. It is proposed that this paucity of Sb2 molecules in astrocytic vesicles may determine the slow secretion. In the present essay we shall overview multiple aspects of vesicular architecture and types of vesicles based on their cargo and dynamics in astroglial cells.
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Affiliation(s)
- R Zorec
- University of Ljubljana, Institute of Pathophysiology, Laboratory of Neuroendocrinology and Molecular Cell Physiology, Zaloska cesta 4, SI-1000 Ljubljana, Slovenia; Celica, BIOMEDICAL, Technology Park 24, 1000 Ljubljana, Slovenia.
| | - A Verkhratsky
- University of Ljubljana, Institute of Pathophysiology, Laboratory of Neuroendocrinology and Molecular Cell Physiology, Zaloska cesta 4, SI-1000 Ljubljana, Slovenia; Celica, BIOMEDICAL, Technology Park 24, 1000 Ljubljana, Slovenia; Faculty of Life Sciences, The University of Manchester, Manchester M13 9PT, UK; Achucarro Center for Neuroscience, IKERBASQUE, 48011 Bilbao, Spain; University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain.
| | - J J Rodríguez
- Achucarro Center for Neuroscience, IKERBASQUE, 48011 Bilbao, Spain; University of the Basque Country UPV/EHU and CIBERNED, Leioa, Spain.
| | - V Parpura
- Department of Neurobiology, Civitan International Research Center and Center for Glial Biology in Medicine, Evelyn F. McKnight Brain Institute, Atomic Force Microscopy & Nanotechnology Laboratories, 1719 6th Avenue South, CIRC 429, University of Alabama at Birmingham, Birmingham, AL 35294-0021, USA; Department of Biotechnology, University of Rijeka, Radmile Matejčić 2, 51000 Rijeka, Croatia.
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Cappelletti P, Piubelli L, Murtas G, Caldinelli L, Valentino M, Molla G, Pollegioni L, Sacchi S. Structure-function relationships in human d-amino acid oxidase variants corresponding to known SNPs. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1150-9. [PMID: 25701391 DOI: 10.1016/j.bbapap.2015.02.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/05/2015] [Accepted: 02/07/2015] [Indexed: 12/11/2022]
Abstract
In the brain, d-amino acid oxidase plays a key role in modulating the N-methyl-d-aspartate receptor (NMDAR) activation state, catalyzing the stereospecific degradation of the coagonist d-serine. A relationship between d-serine signaling deregulation, NMDAR dysfunction, and CNS diseases is presumed. Notably, the R199W substitution in human DAAO (hDAAO) was associated with familial amyotrophic lateral sclerosis (ALS), and further coding substitutions, i.e., R199Q and W209R, were also deposited in the single nucleotide polymorphism database. Here, we investigated the biochemical properties of these different hDAAO variants. The W209R hDAAO variant shows an improved d-serine degradation ability (higher activity and affinity for the cofactor FAD) and produces a greater decrease in cellular d/(d+l) serine ratio than the wild-type counterpart when expressed in U87 cells. The production of H2O2 as result of excessive d-serine degradation by this hDAAO variant may represent the factor affecting cell viability after stable transfection. The R199W/Q substitution in hDAAO altered the protein conformation and enzymatic activity was lost under conditions resembling the cellular ones: this resulted in an abnormal increase in cellular d-serine levels. Altogether, these results indicate that substitutions that affect hDAAO functionality directly impact on d-serine cellular levels (at least in the model cell system used). The pathological effect of the expression of the R199W hDAAO, as observed in familial ALS, originates from both protein instability and a decrease in kinetic efficiency: the increase in synaptic d-serine may be mainly responsible for the neurotoxic effect. This information is expected to drive future targeted treatments.
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Affiliation(s)
- Pamela Cappelletti
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy; The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy
| | - Luciano Piubelli
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy; The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy
| | - Giulia Murtas
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy
| | - Laura Caldinelli
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy; The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy
| | - Mattia Valentino
- The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy; CNR, Istituto di Chimica del Riconoscimento Molecolare, Sezione Adolfo Quilico, via M. Bianchi 9, 20131 Milano, Italy
| | - Gianluca Molla
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy; The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy
| | - Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy; The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy
| | - Silvia Sacchi
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli Studi dell'Insubria, via J. H. Dunant 3, 21100 Varese, Italy; The Protein Factory, Politecnico di Milano, ICMR-CNR, Università degli Studi dell'Insubria, via Mancinelli 7, 20131 Milano, Italy.
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Yu H, Li T, Cui Y, Liao Y, Wang G, Gao L, Zhao F, Jin Y. Effects of lead exposure on d-serine metabolism in the hippocampus of mice at the early developmental stages. Toxicology 2014; 325:189-99. [DOI: 10.1016/j.tox.2014.09.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 09/15/2014] [Accepted: 09/16/2014] [Indexed: 02/05/2023]
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Vorlová B, Nachtigallová D, Jirásková-Vaníčková J, Ajani H, Jansa P, Rezáč J, Fanfrlík J, Otyepka M, Hobza P, Konvalinka J, Lepšík M. Malonate-based inhibitors of mammalian serine racemase: kinetic characterization and structure-based computational study. Eur J Med Chem 2014; 89:189-97. [PMID: 25462239 DOI: 10.1016/j.ejmech.2014.10.043] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 10/14/2014] [Accepted: 10/14/2014] [Indexed: 10/24/2022]
Abstract
Overactivation of NMDA receptors has been implicated in various neuropathological conditions, including brain ischaemia, neurodegenerative disorders and epilepsy. Production of d-serine, an NMDA receptor co-agonist, from l-serine is catalyzed in vivo by the pyridoxal-5'-phosphate (PLP)-dependent enzyme serine racemase. Specific inhibition of this enzyme has been proposed as a promising strategy for treatment of neurological conditions caused by NMDA receptor dysfunction. Here we present the synthesis and activity analysis of a series of malonate-based inhibitors of mouse serine racemase (mSR). The compounds possessed IC50 values ranging from 40 ± 11 mM for 2,2-bis(hydroxymethyl)malonate down to 57 ± 1 μM for 2,2-dichloromalonate, the most effective competitive mSR inhibitor known to date. The structure-activity relationship of the whole series in the human orthologue (hSR) was interpreted using Glide docking, WaterMap analysis of hydration and quantum mechanical calculations based on the X-ray structure of the hSR/malonate complex. Docking into the hSR active site with three thermodynamically favourable water molecules was able to discern qualitatively between good and weak inhibitors. Further improvement in ranking was obtained using advanced PM6-D3H4X/COSMO semiempirical quantum mechanics-based scoring which distinguished between the compounds with IC50 better/worse than 2 mM. We have thus not only found a new potent hSR inhibitor but also worked out a computer-assisted protocol to rationalize the binding affinity which will thus aid in search for more effective SR inhibitors. Novel, potent hSR inhibitors may represent interesting research tools as well as drug candidates for treatment of diseases associated with NMDA receptor overactivation.
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Affiliation(s)
- Barbora Vorlová
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic; Department of Biochemistry, Faculty of Natural Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic
| | - Dana Nachtigallová
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
| | - Jana Jirásková-Vaníčková
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic; Department of Biochemistry, Faculty of Natural Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic
| | - Haresh Ajani
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic; Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Palacky University, 771 46 Olomouc, Czech Republic
| | - Petr Jansa
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
| | - Jan Rezáč
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
| | - Jindřich Fanfrlík
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic
| | - Michal Otyepka
- Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Palacky University, 771 46 Olomouc, Czech Republic
| | - Pavel Hobza
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic; Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Palacky University, 771 46 Olomouc, Czech Republic
| | - Jan Konvalinka
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic; Department of Biochemistry, Faculty of Natural Science, Charles University, Albertov 6, 128 43 Prague 2, Czech Republic.
| | - Martin Lepšík
- Institute of Organic Chemistry and Biochemistry, Gilead Sciences and IOCB Research Centre, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nam. 2, 166 10 Prague 6, Czech Republic.
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Novel human D-amino acid oxidase inhibitors stabilize an active-site lid-open conformation. Biosci Rep 2014; 34:BSR20140071. [PMID: 25001371 PMCID: PMC4127593 DOI: 10.1042/bsr20140071] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The NMDAR (N-methyl-D-aspartate receptor) is a central regulator of synaptic plasticity and learning and memory. hDAAO (human D-amino acid oxidase) indirectly reduces NMDAR activity by degrading the NMDAR co-agonist D-serine. Since NMDAR hypofunction is thought to be a foundational defect in schizophrenia, hDAAO inhibitors have potential as treatments for schizophrenia and other nervous system disorders. Here, we sought to identify novel chemicals that inhibit hDAAO activity. We used computational tools to design a focused, purchasable library of compounds. After screening this library for hDAAO inhibition, we identified the structurally novel compound, 'compound 2' [3-(7-hydroxy-2-oxo-4-phenyl-2H-chromen-6-yl)propanoic acid], which displayed low nM hDAAO inhibitory potency (Ki=7 nM). Although the library was expected to enrich for compounds that were competitive for both D-serine and FAD, compound 2 actually was FAD uncompetitive, much like canonical hDAAO inhibitors such as benzoic acid. Compound 2 and an analog were independently co-crystalized with hDAAO. These compounds stabilized a novel conformation of hDAAO in which the active-site lid was in an open position. These results confirm previous hypotheses regarding active-site lid flexibility of mammalian D-amino acid oxidases and could assist in the design of the next generation of hDAAO inhibitors.
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Abazyan S, Yang EJ, Abazyan B, Xia M, Yang C, Rojas C, Slusher B, Sattler R, Pletnikov M. Mutant disrupted-in-schizophrenia 1 in astrocytes: focus on glutamate metabolism. J Neurosci Res 2014; 92:1659-68. [PMID: 25131692 DOI: 10.1002/jnr.23459] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 06/18/2014] [Accepted: 06/30/2014] [Indexed: 01/05/2023]
Abstract
Disrupted-in-schizophrenia 1 (DISC1) is a genetic risk factor that has been implicated in major mental disorders. DISC1 binds to and stabilizes serine racemase to regulate production of D-serine by astrocytes, contributing to glutamate (GLU) neurotransmission. However, the possible involvement of astrocytic DISC1 in synthesis, metabolism, reuptake, or secretion of GLU remains unexplored. Therefore, we studied the effects of dominant-negative mutant DISC1 on various aspects of GLU metabolism by using primary astrocyte cultures and hippocampal tissue from transgenic mice with astrocyte-restricted expression of mutant DISC1. Although mutant DISC1 had no significant effects on astrocyte proliferation, GLU reuptake, glutaminase, or glutamate carboxypeptidase II activity, expression of mutant DISC1 was associated with increased levels of alanine-serine-cysteine transporter 2, vesicular glutamate transporters 1 and 3 in primary astrocytes and in the hippocampus, and elevated expression of the NR1 subunit and diminished expression of the NR2A subunit of N-methyl-D-aspartate (NMDA) receptors in the hippocampus, at postnatal day 21. Our findings indicate that decreased D-serine production by astrocytic mutant DISC1 might lead to compensatory changes in levels of the amino acid transporters and NMDA receptors in the context of tripartite synapse.
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Affiliation(s)
- Sofya Abazyan
- Departments of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland
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70
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Pang J, Scrutton NS, Sutcliffe MJ. Quantum Mechanics/Molecular Mechanics Studies on the Mechanism of Action of Cofactor Pyridoxal 5′-Phosphate in Ornithine 4,5-Aminomutase. Chemistry 2014; 20:11390-401. [DOI: 10.1002/chem.201402759] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Indexed: 02/02/2023]
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71
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D'Ascenzo M, Podda MV, Grassi C. The role of D-serine as co-agonist of NMDA receptors in the nucleus accumbens: relevance to cocaine addiction. Front Synaptic Neurosci 2014; 6:16. [PMID: 25076900 PMCID: PMC4100571 DOI: 10.3389/fnsyn.2014.00016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 06/29/2014] [Indexed: 12/20/2022] Open
Abstract
Cocaine addiction is characterized by compulsive drug use despite adverse consequences and high rate of relapse during periods of abstinence. Increasing consensus suggests that addiction to drugs of abuse usurps learning and memory mechanisms normally related to natural rewards, ultimately producing long-lasting neuroadaptations in the mesocorticolimbic system. This system, formed in part by the ventral tegmental area and nucleus accumbens (NAc), has a central role in the development and expression of addictive behaviors. In addition to a broad spectrum of changes that affect morphology and function of NAc excitatory circuits in cocaine–treated animals, impaired N-methyl-D-aspartate receptor (NMDAR)-dependent synaptic plasticity is a typical feature. D-serine, a D-amino acid that has been found at high levels in mammalian brain, binds with high affinity the co-agonist site of NMDAR and mediates, along with glutamate, several important processes including synaptic plasticity. Here we review recent literature focusing on cocaine-induced impairment in synaptic plasticity mechanisms in the NAc and on the fundamental role of D-serine as co-agonist of NMDAR in functional and dysfunctional synaptic plasticity within this nucleus. The emerging picture is that reduced D-serine levels play a crucial role in synaptic plasticity relevant to cocaine addiction. This finding opens new perspectives for therapeutic approaches to treat this addictive state.
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Affiliation(s)
- Marcello D'Ascenzo
- Institute of Human Physiology, Medical School, Universitá Cattolica "S. Cuore" Rome, Italy
| | - Maria Vittoria Podda
- Institute of Human Physiology, Medical School, Universitá Cattolica "S. Cuore" Rome, Italy
| | - Claudio Grassi
- Institute of Human Physiology, Medical School, Universitá Cattolica "S. Cuore" Rome, Italy
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72
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Abstract
D-Serine (DSR) is an endogenous amino acid involved in glia-synapse interactions that has unique neurotransmitter characteristics. DSR acts as obligatory coagonist at the glycine site associated with the N-methyl-D-aspartate subtype of glutamate receptors (NMDAR) and has a cardinal modulatory role in major NMDAR-dependent processes including NMDAR-mediated neurotransmission, neurotoxicity, synaptic plasticity, and cell migration. Since either over- or underfunction of NMDARs may be involved in the pathophysiology of neuropsychiatric disorders; the pharmacological manipulation of DSR signaling represents a major drug development target. A first generation of proof-of-concept animal and clinical studies suggest beneficial DSR effects in treatment-refractory schizophrenia, movement, depression, and anxiety disorders and for the improvement of cognitive performance. A related developing pharmacological strategy is the indirect modification of DSR synaptic levels by use of compounds that alter the function of main enzymes responsible for DSR production and degradation. Accumulating data indicate that, during the next decade, we will witness important advances in the understanding of DSR role that will further contribute to elucidating the causes of neuropsychiatric disorders and will be instrumental in the development of innovative treatments.
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73
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Sasabe J, Suzuki M, Imanishi N, Aiso S. Activity of D-amino acid oxidase is widespread in the human central nervous system. Front Synaptic Neurosci 2014; 6:14. [PMID: 24959138 PMCID: PMC4050652 DOI: 10.3389/fnsyn.2014.00014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2014] [Accepted: 05/20/2014] [Indexed: 12/11/2022] Open
Abstract
It has been proposed that D-amino acid oxidase (DAO) plays an essential role in degrading D-serine, an endogenous coagonist of N-methyl-D-aspartate (NMDA) glutamate receptors. DAO shows genetic association with amyotrophic lateral sclerosis (ALS) and schizophrenia, in whose pathophysiology aberrant metabolism of D-serine is implicated. Although the pathology of both essentially involves the forebrain, in rodents, enzymatic activity of DAO is hindbrain-shifted and absent in the region. Here, we show activity-based distribution of DAO in the central nervous system (CNS) of humans compared with that of mice. DAO activity in humans was generally higher than that in mice. In the human forebrain, DAO activity was distributed in the subcortical white matter and the posterior limb of internal capsule, while it was almost undetectable in those areas in mice. In the lower brain centers, DAO activity was detected in the gray and white matters in a coordinated fashion in both humans and mice. In humans, DAO activity was prominent along the corticospinal tract, rubrospinal tract, nigrostriatal system, ponto-/olivo-cerebellar fibers, and in the anterolateral system. In contrast, in mice, the reticulospinal tract and ponto-/olivo-cerebellar fibers were the major pathways showing strong DAO activity. In the human corticospinal tract, activity-based staining of DAO did not merge with a motoneuronal marker, but colocalized mostly with excitatory amino acid transporter 2 and in part with GFAP, suggesting that DAO activity-positive cells are astrocytes seen mainly in the motor pathway. These findings establish the distribution of DAO activity in cerebral white matter and the motor system in humans, providing evidence to support the involvement of DAO in schizophrenia and ALS. Our results raise further questions about the regulation of D-serine in DAO-rich regions as well as the physiological/pathological roles of DAO in white matter astrocytes.
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Affiliation(s)
- Jumpei Sasabe
- Department of Anatomy, Keio University School of Medicine Shinjuku-ku, Tokyo, Japan
| | - Masataka Suzuki
- Department of Anatomy, Keio University School of Medicine Shinjuku-ku, Tokyo, Japan
| | - Nobuaki Imanishi
- Department of Anatomy, Keio University School of Medicine Shinjuku-ku, Tokyo, Japan
| | - Sadakazu Aiso
- Department of Anatomy, Keio University School of Medicine Shinjuku-ku, Tokyo, Japan
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Martineau M, Parpura V, Mothet JP. Cell-type specific mechanisms of D-serine uptake and release in the brain. Front Synaptic Neurosci 2014; 6:12. [PMID: 24910611 PMCID: PMC4039169 DOI: 10.3389/fnsyn.2014.00012] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Accepted: 05/02/2014] [Indexed: 12/30/2022] Open
Abstract
Accumulating evidence during the last decade established that D-serine is a key signaling molecule utilized by neurons and astroglia in the mammalian central nervous system. D-serine is increasingly appreciated as the main physiological endogenous coagonist for synaptic NMDA receptors at central excitatory synapses; it is mandatory for long-term changes in synaptic strength, memory, learning, and social interactions. Alterations in the extracellular levels of D-serine leading to disrupted cell-cell signaling are a trademark of many chronic or acute neurological (i.e., Alzheimer disease, epilepsy, stroke) and psychiatric (i.e., schizophrenia) disorders, and are associated with addictive behavior (i.e., cocaine addiction). Indeed, fine tuning of the extracellular levels of D-serine, achieved by various molecular machineries and signaling pathways, is necessary for maintenance of accurate NMDA receptor functions. Here, we review the experimental data supporting the notion that astroglia and neurons use different pathways to regulate levels of extracellular D-serine.
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Affiliation(s)
- Magalie Martineau
- Department of Cellular Biophysics, Institute for Medical Physics and Biophysics, University of Muenster Muenster, Germany
| | - Vladimir Parpura
- Department of Neurobiology, University of Alabama at Birmingham Birmingham, AL, USA ; Department of Biotechnology, University of Rijeka Rijeka, Croatia
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Balu DT, Takagi S, Puhl MD, Benneyworth MA, Coyle JT. D-serine and serine racemase are localized to neurons in the adult mouse and human forebrain. Cell Mol Neurobiol 2014; 34:419-35. [PMID: 24436034 DOI: 10.1007/s10571-014-0027-z] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 01/03/2014] [Indexed: 01/12/2023]
Abstract
D-Serine, a co-agonist at the NMDA receptor (NMDAR), is synthesized from L-serine by the enzyme serine racemase (SR), which is heavily expressed in the forebrain. Although SR was originally reported to be localized exclusively to astrocytes, recent conditional knock out results demonstrate that little SR is expressed in forebrain astrocytes. As a consequence, the cellular location of its product, D-serine, in the brain is also uncertain. Immunocytochemistry now indicates that SR is expressed primarily in forebrain glutamatergic neurons with the remainder in GABAergic interneurons. We utilized SR deficient (SR-/-) mice, which have <15 % of normal D-serine levels, to validate and optimize a D-serine immunohistochemical method. Nearly all of the D-serine in neocortex and hippocampus (HP) is found in neurons, with virtually no D-serine co-localizing with two astrocyte markers. Interestingly, only a subset of the D-serine positive neurons contained SR in the neocortex and HP. Greater than half of the D-serine positive neurons were GABAergic interneurons, with a majority of these neurons containing parvalbumin and/or somatostatin. Only ~25-40 % of interneurons expressed SR in the neocortex and HP. Finally, we demonstrate in human post-mortem neocortex that SR is found in both excitatory and inhibitory neurons, but not in S100β-containing astrocytes. In sum, these findings conclusively demonstrate that the majority of D-serine is both synthesized and stored in neurons. It will be important to determine the functional significance for the separation of synthesis and storage of D-serine in neurons, as well as the presence of this NMDAR co-agonist in GABAergic interneurons.
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Affiliation(s)
- Darrick T Balu
- Department of Psychiatry, Harvard Medical School, Boston, MA, 02115, USA
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76
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Cappelletti P, Campomenosi P, Pollegioni L, Sacchi S. The degradation (by distinct pathways) of humand-amino acid oxidase and its interacting partner pLG72 - two key proteins ind-serine catabolism in the brain. FEBS J 2013; 281:708-23. [DOI: 10.1111/febs.12616] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 11/08/2013] [Accepted: 11/11/2013] [Indexed: 12/26/2022]
Affiliation(s)
- Pamela Cappelletti
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli Studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche ‘The Protein Factory’; Politecnico di Milano; ICRM-CNR Milano and Università degli studi dell'Insubria; Varese Italy
| | - Paola Campomenosi
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli Studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche ‘The Protein Factory’; Politecnico di Milano; ICRM-CNR Milano and Università degli studi dell'Insubria; Varese Italy
| | - Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli Studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche ‘The Protein Factory’; Politecnico di Milano; ICRM-CNR Milano and Università degli studi dell'Insubria; Varese Italy
| | - Silvia Sacchi
- Dipartimento di Biotecnologie e Scienze della Vita; Università degli Studi dell'Insubria; Varese Italy
- Centro Interuniversitario di Ricerca in Biotecnologie Proteiche ‘The Protein Factory’; Politecnico di Milano; ICRM-CNR Milano and Università degli studi dell'Insubria; Varese Italy
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77
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The serine shuttle between glia and neurons: implications for neurotransmission and neurodegeneration. Biochem Soc Trans 2013; 41:1546-50. [DOI: 10.1042/bst20130220] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
D-Serine is a physiological co-agonist of NMDARs (N-methyl-D-aspartate receptors) required for neurotransmission, synaptic plasticity and neurotoxicity. There is no consensus, however, on the relative roles of neurons and astrocytes in D-serine signalling. The effects of D-serine had been attributed to its role as a gliotransmitter specifically produced and released by astrocytes. In contrast, recent studies indicate that neurons regulate their own NMDARs by releasing D-serine via plasma membrane transporters and depolarization-sensitive pathways. Only a minority of astrocytes contain authentic D-serine, whereas neuronal D-serine accounts for up to 90% of the total D-serine pool. Neuronal and glial D-serine production requires astrocytic L-serine generated by a 3-phosphoglycerate dehydrogenase-dependent pathway. These findings support a model whereby astrocyte-derived L-serine shuttles to neurons to fuel the synthesis of D-serine by serine racemase. We incorporate these new findings in a revised model of serine dynamics, called the glia–neuron serine shuttle, which highlights the role of glia–neuron cross-talk for optimal NMDAR activity and brain development.
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78
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D-Serine metabolism: new insights into the modulation of D-amino acid oxidase activity. Biochem Soc Trans 2013; 41:1551-6. [DOI: 10.1042/bst20130184] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Over the years, accumulating evidence has indicated that D-serine represents the main endogenous ligand of NMDA (N-methyl-D-aspartate) receptors. In the brain, the concentration of D-serine stored in cells is defined by the activity of two enzymes: serine racemase (responsible for both the synthesis and degradation) and D-amino acid oxidase (which catalyses D-serine degradation). The present review is focused on human D-amino acid oxidase, discussing the mechanisms involved in modulating enzyme activity and stability, with the aim to substantiate the pivotal role of D-amino acid oxidase in brain D-serine metabolism.
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Marchetti M, Bruno S, Campanini B, Peracchi A, Mai N, Mozzarelli A. ATP binding to human serine racemase is cooperative and modulated by glycine. FEBS J 2013; 280:5853-63. [PMID: 23992455 DOI: 10.1111/febs.12510] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 08/27/2013] [Accepted: 08/29/2013] [Indexed: 11/26/2022]
Abstract
The N-methyl D-aspartate (NMDA) receptors play a key role in excitatory neurotransmission, and control learning, memory and synaptic plasticity. Their activity is modulated by the agonist glutamate and by the co-agonists d-serine and glycine. In the human brain, d-serine is synthesized from l-serine by the dimeric pyridoxal 5'-phosphate-dependent enzyme serine racemase, which also degrades l- and d-serine to pyruvate and ammonia. The dependence of l- and d-serine β-elimination and l-serine racemization activities on ATP concentration was characterized, and was found to be strongly cooperative, with Hill coefficients close to 2 and apparent ATP dissociation constants ranging from 0.22 to 0.41 mm. ATP binding to the holo-enzyme, monitored by the fluorescence changes of the coenzyme, was also determined to be cooperative, with an apparent dissociation constant of 0.24 mm. Glycine, an active-site ligand, increased the serine racemase affinity for ATP by ~ 22-fold, abolishing cooperativity. Conversely, ATP increased the non-cooperative glycine binding 15-fold. These results indicate cross-talk between allosteric and active sites, leading to the stabilization of two alternative protein conformations with ATP affinities of ~ 10 μM and 1.8 mm, as evaluated within the Monod, Wyman and Changeux model. Therefore, intracellular ATP and glycine control d-serine homeostasis, and, indirectly, NMDA receptor activity. Because hyper- and hypo-activation of NMDA receptors are associated with neuropathologies, the development of allosteric drugs modulating serine racemase activity is a promising therapeutic strategy.
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80
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Astrocytes use a novel transporter to fill gliotransmitter vesicles with D-serine: evidence for vesicular synergy. J Neurosci 2013; 33:10193-4. [PMID: 23785135 DOI: 10.1523/jneurosci.1665-13.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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81
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Hashimoto K, Malchow B, Falkai P, Schmitt A. Glutamate modulators as potential therapeutic drugs in schizophrenia and affective disorders. Eur Arch Psychiatry Clin Neurosci 2013; 263:367-77. [PMID: 23455590 DOI: 10.1007/s00406-013-0399-y] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 02/19/2013] [Indexed: 12/25/2022]
Abstract
Severe psychiatric disorders such as schizophrenia are related to cognitive and negative symptoms, which often are resistant to current treatment approaches. The glutamatergic system has been implicated in the pathophysiology of schizophrenia and affective disorders. A key component is the dysfunction of the glutamatergic N-methyl-D-aspartate (NMDA) receptor. Substances regulating activation/inhibition of the NMDA receptor have been investigated in schizophrenia and major depression and are promising in therapeutic approaches of negative symptoms, cognition, and mood. In schizophrenia, add-on treatments with glycine, D-serine, D-alanine, D-cycloserine, D-amino acid oxidase inhibitors, glycine transporter-1 (GlyT-1) inhibitors (e.g., sarcosine, bitopertin) and agonists (e.g., LY2140023) or positive allosteric modulator (e.g., ADX71149) of group II metabotropic glutamate receptors (mGluRs) have been studied. In major depression, the NMDA receptor antagonists (e.g., ketamine, AZD6765), GluN2B subtype antagonists (e.g., traxoprodil, MK-0657), and partial agonists (e.g., D-cycloserine, GLYX-13) at the glycine site of the NMDA receptor have been proven to be effective in animal studies and first clinical trials. In addition, clinical studies of mGluR2/3 antagonist BCI-838 (a prodrug of BCI-632 (MGS0039)), mGluR2/3-negative allosteric modulators (NMAs) (e.g., RO499819, RO4432717), and mGluR5 NAMs (e.g., AZD2066, RO4917523) are in progress. Future investigations should include effects on brain structure and activation to elucidate neural mechanisms underlying efficacy of these drugs.
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Affiliation(s)
- Kenji Hashimoto
- Division of Clinical Neuroscience, Chiba University Center for Forensic Mental Health, 1-8-1 Inohana, Chiba, 260-8670, Japan.
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82
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Maternal immune activation during gestation interacts with Disc1 point mutation to exacerbate schizophrenia-related behaviors in mice. J Neurosci 2013; 33:7654-66. [PMID: 23637159 DOI: 10.1523/jneurosci.0091-13.2013] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Schizophrenia is thought to result from interactions between susceptible genotypes and environmental risk factors. DISC1 is an important gene for schizophrenia and mood disorders based on both human and animal studies. In the present study we sought to investigate interactions between two distinct point mutations in the mouse Disc1 gene (L100P and Q31L) and maternal immune activation (MIA) during pregnancy with polyinosinic:polycytidylic acid (polyI:C). PolyI:C given at 5 mg/kg impaired cognitive and social behavior in both wild-type (WT) and Disc1-Q31L(+/-) offspring, and reduced prepulse inhibition at 16 but not 8 weeks of age. Disc1-L100P(+/-) mutants were more sensitive to MIA than WT or Disc1-Q31L(+/-) mice. Interleukin-6 (IL-6) is a critical cytokine for mediating the behavioral and transcriptional effects of polyI:C. We found a more pronounced increase of IL-6 in response to polyI:C in fetal brain in Disc1-L100P(+/-) mice compared with WT or Disc1-Q31L(+/-) mice. Coadministration of an anti-IL-6 antibody with polyI:C reversed schizophrenia-related behavioral phenotypes in Disc1-L100P(+/-) mice. In summary, we found specific interactions between discrete genetic (Disc1-L100P(+/-)) and environmental factors (MIA) that exacerbate schizophrenia-related phenotypes. IL-6 may be important in the pathophysiology of this interaction.
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83
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Billard JM. Serine racemase as a prime target for age-related memory deficits. Eur J Neurosci 2013; 37:1931-8. [DOI: 10.1111/ejn.12226] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 02/26/2013] [Accepted: 03/22/2013] [Indexed: 11/29/2022]
Affiliation(s)
- J.-M. Billard
- Centre de Psychiatrie et Neurosciences; Faculté de Médecine; Université Paris Descartes; UMR 894; Sorbonne Paris Cité; 2 ter rue d'Alésia; Paris; 75014; France
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84
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Maucler C, Pernot P, Vasylieva N, Pollegioni L, Marinesco S. In vivo D-serine hetero-exchange through alanine-serine-cysteine (ASC) transporters detected by microelectrode biosensors. ACS Chem Neurosci 2013; 4:772-81. [PMID: 23581544 DOI: 10.1021/cn4000549] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
D-serine, a co-agonist of N-methyl D-aspartate (NMDA) receptors, has been implicated in neurological and psychiatric disorders such as cerebral ischemia, lateral amyotrophic sclerosis, or schizophrenia. D-serine signaling represents an important pharmacological target for treating these diseases; however, the biochemical mechanisms controlling extracellular D-serine levels in vivo are still unclear. D-serine heteroexchange through small neutral amino acid transporters has been shown in cell cultures and brain slices and could provide a biochemical mechanism for the control of D-serine extracellular concentration in vivo. Alternatively, exocytotic D-serine release has also been proposed. In this study, the dynamics of D-serine release and clearance were explored in vivo on a second-by-second time scale using microelectrode biosensors. The rate of D-serine clearance in the rat frontal cortex after a microionophoretic injection revealed a transporter-mediated uptake mechanism. D-serine uptake was blocked by small neutral l-amino acids, implicating alanine-serine-cysteine (ASC) transporters, in particular high affinity Asc-1 and low affinity ASCT2 transporters. Interestingly, changes in alanine, serine, or threonine levels resulted in D-serine release through ASC transporters. Asc-1, but not ASCT2, appeared to release D-serine in response to changes in amino acid concentrations. Finally, neuronal silencing by tetrodotoxin increased D-serine extracellular concentration by an ASC-transporter-dependent mechanism. Together, these results indicate that D-serine heteroexchange through ASC transporters is present in vivo and may constitute a key component in the regulation of D-serine extracellular concentration.
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Affiliation(s)
- Caroline Maucler
- INSERM U1028; CNRS UMR5292 Lyon Neuroscience Research Center, AniRA-Neurochem technological platform, team WAKING, Lyon F-69000, France
- Université Claude Bernard Lyon 1, Lyon F-69000, France
| | - Pierre Pernot
- INSERM U1028; CNRS UMR5292 Lyon Neuroscience Research Center, AniRA-Neurochem technological platform, team WAKING, Lyon F-69000, France
- Université Claude Bernard Lyon 1, Lyon F-69000, France
| | - Natalia Vasylieva
- INSERM U1028; CNRS UMR5292 Lyon Neuroscience Research Center, AniRA-Neurochem technological platform, team WAKING, Lyon F-69000, France
- Université Claude Bernard Lyon 1, Lyon F-69000, France
- Institut de nanotechnologie de Lyon, CNRS UMR-5270, INSA de Lyon, France
| | - Loredano Pollegioni
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli studi dell’Insubria, Varese, Italy
- “The Protein Factory”, Centro Interuniversitario di Ricerca in Biotecnologie Proteiche ICRM-CNR Milano, Politecnico di Milano and Università degli studi dell’Insubria, Italy
| | - Stéphane Marinesco
- INSERM U1028; CNRS UMR5292 Lyon Neuroscience Research Center, AniRA-Neurochem technological platform, team WAKING, Lyon F-69000, France
- Université Claude Bernard Lyon 1, Lyon F-69000, France
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85
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Ma T, Abazyan S, Abazyan B, Nomura J, Yang C, Seshadri S, Sawa A, Snyder S, Pletnikov M. Pathogenic disruption of DISC1-serine racemase binding elicits schizophrenia-like behavior via D-serine depletion. Mol Psychiatry 2013; 18:557-67. [PMID: 22801410 PMCID: PMC3475769 DOI: 10.1038/mp.2012.97] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Perturbation of Disrupted-In-Schizophrenia-1 (DISC1) and D-serine/NMDA receptor hypofunction have both been implicated in the pathophysiology of schizophrenia and other psychiatric disorders. In the present study, we demonstrate that these two pathways intersect with behavioral consequences. DISC1 binds to and stabilizes serine racemase (SR), the enzyme that generates D-serine, an endogenous co-agonist of the NMDA receptor. Mutant DISC1 fails to bind to SR, facilitating ubiquitination and degradation of SR and a decrease in D-serine production. To elucidate DISC1-SR interactions in vivo, we generated a mouse model of selective and inducible expression of mutant DISC1 in astrocytes, the main source of D-serine in the brain. Expression of mutant DISC1 downregulates endogenous DISC1 and decreases protein but not mRNA levels of SR, resulting in diminished production of D-serine. In contrast, mutant DISC1 does not alter levels of ALDH1L1, connexins, GLT-1 or binding partners of DISC1 and SR, LIS1 or PICK1. Adult male and female mice with lifelong expression of mutant DISC1 exhibit behavioral abnormalities consistent with hypofunction of NMDA neurotransmission. Specifically, mutant mice display greater responses to an NMDA antagonist, MK-801, in open field and pre-pulse inhibition of the acoustic startle tests and are significantly more sensitive to the ameliorative effects of D-serine. These findings support a model wherein mutant DISC1 leads to SR degradation via dominant negative effects, resulting in D-serine deficiency that diminishes NMDA neurotransmission thus linking DISC1 and NMDA pathophysiological mechanisms in mental illness.
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Affiliation(s)
- T.M. Ma
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD
| | - S. Abazyan
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD
| | - B. Abazyan
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD
| | - J. Nomura
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD,Division of Molecular Medical Science, Hiroshima University Graduate School of Biomedical Sciences, Hiroshima, Japan
| | - C. Yang
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD
| | - S. Seshadri
- Division of Molecular Psychiatry, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD
| | - A. Sawa
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD,Division of Molecular Psychiatry, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD,McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD
| | - S.H. Snyder
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD,Departments of Pharmacology and Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD,co-corresponding authors
| | - M.V. Pletnikov
- Division of Neurobiology, Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD,The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD,Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, MD,co-corresponding authors
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86
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Van Horn MR, Sild M, Ruthazer ES. D-serine as a gliotransmitter and its roles in brain development and disease. Front Cell Neurosci 2013; 7:39. [PMID: 23630460 PMCID: PMC3632749 DOI: 10.3389/fncel.2013.00039] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 03/26/2013] [Indexed: 01/05/2023] Open
Abstract
The development of new techniques to study glial cells has revealed that they are active participants in the development of functional neuronal circuits. Calcium imaging studies demonstrate that glial cells actively sense and respond to neuronal activity. Glial cells can produce and release neurotransmitter-like molecules, referred to as gliotransmitters, that can in turn influence the activity of neurons and other glia. One putative gliotransmitter, D-serine is believed to be an endogenous co-agonist for synaptic N-methyl-D-aspartate receptors (NMDARs), modulating synaptic transmission and plasticity mediated by this receptor. The observation that D-serine levels in the mammalian brain increase during early development, suggests a possible role for this gliotransmitter in normal brain development and circuit refinement. In this review we will examine the data that D-serine and its associated enzyme serine racemase are developmentally regulated. We will consider the evidence that D-serine is actively released by glial cells and examine the studies that have implicated D-serine as a critical player involved in regulating NMDAR-mediated synaptic transmission and neuronal migration during development. Furthermore, we will consider how dysregulation of D-serine may play an important role in the etiology of neurological and psychiatric diseases.
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Affiliation(s)
- Marion R Van Horn
- Montreal Neurological Institute, McGill University Montreal, QC, Canada
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87
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Curcio L, Podda MV, Leone L, Piacentini R, Mastrodonato A, Cappelletti P, Sacchi S, Pollegioni L, Grassi C, D'Ascenzo M. Reduced D-serine levels in the nucleus accumbens of cocaine-treated rats hinder the induction of NMDA receptor-dependent synaptic plasticity. ACTA ACUST UNITED AC 2013; 136:1216-30. [PMID: 23518710 DOI: 10.1093/brain/awt036] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cocaine seeking behaviour and relapse have been linked to impaired potentiation and depression at excitatory synapses in the nucleus accumbens, but the mechanism underlying this process is poorly understood. We show that, in the rat nucleus accumbens core, D-serine is the endogenous coagonist of N-methyl-D-aspartate receptors, and its presence is essential for N-methyl-D-aspartate receptor-dependent potentiation and depression of synaptic transmission. Nucleus accumbens core slices obtained from cocaine-treated rats after 1 day of abstinence presented significantly reduced D-serine concentrations, increased expression of the D-serine degrading enzyme, D-amino acid oxidase, and downregulated expression of serine racemase, the enzyme responsible for D-serine synthesis. The D-serine deficit was associated with impairment of potentiation and depression of glutamatergic synaptic transmission, which was restored by slice perfusion with exogenous D-serine. Furthermore, in vivo administration of D-serine directly into the nucleus accumbens core blocked behavioural sensitization to cocaine. These results provide evidence for a critical role of D-serine signalling in synaptic plasticity relevant to cocaine addiction.
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Affiliation(s)
- Livia Curcio
- Institute of Human Physiology, Medical School, Università Cattolica, 00168 Rome, Italy
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88
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Sayano T, Kawakami Y, Kusada W, Suzuki T, Kawano Y, Watanabe A, Takashima K, Arimoto Y, Esaki K, Wada A, Yoshizawa F, Watanabe M, Okamoto M, Hirabayashi Y, Furuya S. L-serine deficiency caused by genetic Phgdh deletion leads to robust induction of 4E-BP1 and subsequent repression of translation initiation in the developing central nervous system. FEBS J 2013; 280:1502-17. [PMID: 23350942 DOI: 10.1111/febs.12146] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 01/09/2013] [Accepted: 01/21/2013] [Indexed: 12/23/2022]
Abstract
Targeted disruption in mice of the gene encoding D-3-phosphoglycerate dehydrogenase (Phgdh) results in embryonic lethality associated with a striking reduction in free L-serine and growth retardation including severe brain malformation. We previously observed a severe impairment in neurogenesis of the central nervous system of Phgdh knockout (KO) embryos and a reduction in the protein content of their brains. Although these findings suggest that L-serine deficiency links attenuation of mRNA translation to severe developmental malformation of the central nervous system, the underlying key molecular event remains unexplored. Here we demonstrate that mRNA of Eif4ebp1 encoding eukaryotic initiation factor 4 binding protein 1 and its protein, 4E-BP1, are markedly induced in the central nervous system of Phgdh KO embryos, whereas a modest induction is observed in the liver. The increase in 4E-BP1 was associated with a decrease in the cap initiation complex in the brain, as shown by lower levels of eukaryotic translation initiation factor 4G bound to eukaryotic translation initiation factor 4E (eIF4E) and increased eIF4E interaction with 4E-BP1 based on 7-methyl-GTP chromatography. eIF4E protein and polysomes were also diminished in Phgdh KO embryos. Induction of Eif4ebp1 mRNA and of 4E-BP1 was reproduced in mouse embryonic fibroblasts established from Phgdh KO embryos under the condition of L-serine deprivation. Induction of Eif4ebp1 mRNA was suppressed only when L-serine was supplemented in the culture medium, indicating that reduced L-serine availability regulates the induction of Eif4ebp1/4E-BP1. These data suggest that elevated levels of 4E-BP1 may be involved in a mechanism to arrest brain development in Phgdh KO embryos.
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Affiliation(s)
- Tomoko Sayano
- Division of Systems Biology, Department of Bioscience and Biotechnology, Kyushu University, Fukuoka, Japan
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89
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Henneberger C, Bard L, King C, Jennings A, Rusakov DA. NMDA Receptor Activation: Two Targets for Two Co-Agonists. Neurochem Res 2013; 38:1156-62. [DOI: 10.1007/s11064-013-0987-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/27/2013] [Accepted: 01/28/2013] [Indexed: 12/01/2022]
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90
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Filali M, Lalonde R. The effects of subchronic d-serine on left–right discrimination learning, social interaction, and exploratory activity in APPswe/PS1 mice. Eur J Pharmacol 2013; 701:152-8. [DOI: 10.1016/j.ejphar.2012.12.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 12/12/2012] [Accepted: 12/19/2012] [Indexed: 10/27/2022]
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91
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Wang YF, Sun MY, Hou Q, Parpura V. Hyposmolality differentially and spatiotemporally modulates levels of glutamine synthetase and serine racemase in rat supraoptic nucleus. Glia 2013; 61:529-38. [PMID: 23361961 DOI: 10.1002/glia.22453] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 11/09/2012] [Indexed: 01/22/2023]
Abstract
Prolonged hyposmotic challenge (HOC) has a dual effect on vasopressin (VP) secretion [Yagil and Sladek (1990) Am J Physiol 258(2 Pt 2):R492-R500]. We describe an electrophysiological correlate of this phenomenon, whereby in vitro HOC transiently reduced the firing activity of VP neurons within the supraoptic nucleus of brain slices, which was followed by a rebound increase of their activity; this was paralleled by changes in the level of proteins relevant to astroglia-neuronal interactions. Hence, in vitro HOC transiently (at 5 min) increased the level of astrocyte-specific glial fibrillary acidic protein (GFAP), which then declined to control or base level (at 20 min); this was blocked by the gliotoxin L-aminoadipic acid, but not by tetanus toxin, which was used to inhibit neurotransmission. Similarly, in vivo HOC led to changes in GFAP level, which after an early increase (10 min) returned to normal (30 min). Immunoassays revealed that neuronal, but not astrocytic, expression of serine racemase (SR) was increased at the late stage of HOC in vivo, whereas at an early stage there was a transient increase in level of the astrocyte-specific glutamine synthetase (GS). Furthermore, there was an increased molecular association between GFAP and GS at 10 min, whereas SR increased its association with the neuronal nuclear antigen NeuN at 30 min. These results suggest that the dual effect of HOC on VP neuronal secretion/activity could be related to metabolic/signaling changes in astrocytes (glutamate-glutamine conversion) and neurons (D-serine synthesis/ammonia production), which may account for the rebound in VP neuronal activity, presumably by promoting the activation of neuronal glutamate receptors.
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Affiliation(s)
- Yu-Feng Wang
- Department of Cell Biology and Neuroscience, University of California, Riverside, California, USA.
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92
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Abstract
PURPOSE OF REVIEW Here, we discuss the recent data on the role of different N-methyl D-aspartate receptor (NMDAR) coagonists, D-serine and glycine, in regulating NMDAR activity and neurotoxicity. RECENT FINDINGS D-Serine originates from both neurons and astrocytes, from where it is released by different mechanisms. Recent data indicate that like glial D-serine, neuronal D-serine is required for NMDAR-dependent, long-term potentiation at the hippocampal CA1-CA3 synapses and proper synapse formation in the cerebral cortex. D-serine is the physiological coagonist of synaptic NMDAR, whereas glycine action is restricted to extrasynaptic sites. SUMMARY D-Serine is now recognized as the major NMDAR coagonist at the synapse. The data establish D-serine as a key transmitter or neuromodulator that mediates synaptic NMDAR activation and neurotoxicity. In this context, drugs that inhibit D-serine synthesis or release will provide new neuroprotective strategy.
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Affiliation(s)
- Inna Radzishevsky
- Department of Biochemistry, B Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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93
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Caldinelli L, Sacchi S, Molla G, Nardini M, Pollegioni L. Characterization of human DAAO variants potentially related to an increased risk of schizophrenia. Biochim Biophys Acta Mol Basis Dis 2012; 1832:400-10. [PMID: 23219954 DOI: 10.1016/j.bbadis.2012.11.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 11/22/2012] [Accepted: 11/27/2012] [Indexed: 12/11/2022]
Abstract
Considering the key role of d-serine in N-methyl-d-aspartate receptor-mediated neurotransmission, it is highly relevant to define the role that enzymes play in d-serine synthesis and degradation. In particular, the details of regulation of the d-serine catabolic human enzyme d-amino acid oxidase (hDAAO) are unknown although different lines of evidence have shown it to be involved in schizophrenia susceptibility. Here we investigated the effect of three single nucleotide polymorphisms and known mutations in hDAAO, i.e., D31H, R279A, and G331V. A very low amount of soluble G331V hDAAO is produced in E. coli cells: the recombinant variant enzyme is fully active. Human U87 glioblastoma cells transiently transfected for G331V hDAAO show a low viability, a significant amount of protein aggregates, and augmented apoptosis. The recombinant D31H and R279A hDAAO variants do not show alterations in tertiary and quaternary structures, thermal stability, binding affinity for inhibitors, and the modulator pLG72, whereas the kinetic efficiency and the affinity for d-serine and for FAD were higher than for the wild-type enzyme. While these effects for the substitution at position 31 cannot be structurally explained, the R279A mutation might affect the hDAAO FAD-binding affinity by altering the "structurally ambivalent" peptide V47-L51. In agreement with the observed increased activity, expression of D31H and R279A hDAAO variants in U87 cells produces a higher decrease in cellular d/(d+l) serine ratio than the wild-type counterpart. In vivo, these substitutions could affect cellular d-serine concentration and its release at synapsis and thus might be relevant for schizophrenia susceptibility.
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Affiliation(s)
- Laura Caldinelli
- Dipartimento di Biotecnologie e Scienze della Vita, Università degli studi dell'Insubria, Varese, Italy
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94
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Spalloni A, Nutini M, Longone P. Role of the N-methyl-d-aspartate receptors complex in amyotrophic lateral sclerosis. Biochim Biophys Acta Mol Basis Dis 2012. [PMID: 23200922 DOI: 10.1016/j.bbadis.2012.11.013] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is an adult onset neurodegenerative disease pathologically characterized by the massive loss of motor neurons in the spinal cord, brain stem and cerebral cortex. There is a consensus in the field that ALS is a multifactorial pathology and a number of possible mechanisms have been suggested. Among the proposed hypothesis, glutamate toxicity has been one of the most investigated. Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor mediated cell death and impairment of the glutamate-transport system have been suggested to play a central role in the glutamate-mediated motor neuron degeneration. In this context, the role played by the N-methyl-d-aspartate (NMDA) receptor has received considerable less attention notwithstanding its high Ca(2+) permeability, expression in motor neurons and its importance in excitotoxicity. This review overviews the critical role of NMDA-mediated toxicity in ALS, with a particular emphasis on the endogenous modulators of the NMDAR.
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Affiliation(s)
- Alida Spalloni
- Molecular Neurobiology Unit, Experimental Neurology, Fondazione Santa Lucia, Rome Italy
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95
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López-Hidalgo M, Salgado-Puga K, Alvarado-Martínez R, Medina AC, Prado-Alcalá RA, García-Colunga J. Nicotine uses neuron-glia communication to enhance hippocampal synaptic transmission and long-term memory. PLoS One 2012; 7:e49998. [PMID: 23185511 PMCID: PMC3503711 DOI: 10.1371/journal.pone.0049998] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Accepted: 10/19/2012] [Indexed: 01/08/2023] Open
Abstract
Nicotine enhances synaptic transmission and facilitates long-term memory. Now it is known that bi-directional glia-neuron interactions play important roles in the physiology of the brain. However, the involvement of glial cells in the effects of nicotine has not been considered until now. In particular, the gliotransmitter D-serine, an endogenous co-agonist of NMDA receptors, enables different types of synaptic plasticity and memory in the hippocampus. Here, we report that hippocampal long-term synaptic plasticity induced by nicotine was annulled by an enzyme that degrades endogenous D-serine, or by an NMDA receptor antagonist that acts at the D-serine binding site. Accordingly, both effects of nicotine: the enhancement of synaptic transmission and facilitation of long-term memory were eliminated by impairing glial cells with fluoroacetate, and were restored with exogenous D-serine. Together, these results show that glial D-serine is essential for the long-term effects of nicotine on synaptic plasticity and memory, and they highlight the roles of glial cells as key participants in brain functions.
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Affiliation(s)
- Mónica López-Hidalgo
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
| | - Karla Salgado-Puga
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
| | - Reynaldo Alvarado-Martínez
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
| | - Andrea Cristina Medina
- Departamento de Neurobiología Conductual y Cognitiva, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
| | - Roberto A. Prado-Alcalá
- Departamento de Neurobiología Conductual y Cognitiva, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
| | - Jesús García-Colunga
- Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro, México
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96
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Reato D, Cammarota M, Parra LC, Carmignoto G. Computational model of neuron-astrocyte interactions during focal seizure generation. Front Comput Neurosci 2012; 6:81. [PMID: 23091457 PMCID: PMC3467689 DOI: 10.3389/fncom.2012.00081] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Accepted: 09/21/2012] [Indexed: 11/18/2022] Open
Abstract
Empirical research in the last decade revealed that astrocytes can respond to neurotransmitters with Ca2+ elevations and generate feedback signals to neurons which modulate synaptic transmission and neuronal excitability. This discovery changed our basic understanding of brain function and provided new perspectives for how astrocytes can participate not only to information processing, but also to the genesis of brain disorders, such as epilepsy. Epilepsy is a neurological disorder characterized by recurrent seizures that can arise focally at restricted areas and propagate throughout the brain. Studies in brain slice models suggest that astrocytes contribute to epileptiform activity by increasing neuronal excitability through a Ca2+-dependent release of glutamate. The underlying mechanism remains, however, unclear. In this study, we implemented a parsimonious network model of neurons and astrocytes. The model consists of excitatory and inhibitory neurons described by Izhikevich's neuron dynamics. The experimentally observed Ca2+ change in astrocytes in response to neuronal activity was modeled with linear equations. We considered that glutamate is released from astrocytes above certain intracellular Ca2+ concentrations thus providing a non-linear positive feedback signal to neurons. Propagating seizure-like ictal discharges (IDs) were reliably evoked in our computational model by repeatedly exciting a small area of the network, which replicates experimental results in a slice model of focal ID in entorhinal cortex. We found that the threshold of focal ID generation was lowered when an excitatory feedback-loop between astrocytes and neurons was included. Simulations show that astrocytes can contribute to ID generation by directly affecting the excitatory/inhibitory balance of the neuronal network. Our model can be used to obtain mechanistic insights into the distinct contributions of the different signaling pathways to the generation and propagation of focal IDs.
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Affiliation(s)
- Davide Reato
- Department of Biomedical Engineering, The City College of the City University of New York New York, NY, USA
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97
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D-Serine Production, Degradation, and Transport in ALS: Critical Role of Methodology. Neurol Res Int 2012; 2012:625245. [PMID: 23029613 PMCID: PMC3458282 DOI: 10.1155/2012/625245] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Accepted: 07/31/2012] [Indexed: 01/12/2023] Open
Abstract
In mammalian systems, D-serine is perhaps the most biologically active D-amino acid described to date. D-serine is a coagonist at the NMDA-receptor, and receptor activation is dependent on D-serine binding. Because D-serine binding dramatically increases receptor affinity for glutamate, it can produce excitotoxicity without any change in glutamate per se. D-serine is twofold higher in the spinal cords of mSOD1 (G93A) ALS mice, and the deletion of serine racemase (SR), the enzyme that produces D-serine, results in an earlier onset of symptoms, but with a much slower rate of disease progression. Localization studies within the brain suggest that mSOD1 and subsequent glial activation could contribute to the alterations in SR and D-serine seen in ALS. By also degrading both D-serine and L-serine, SR appears to be a prime bidirectional regulator of free serine levels in vivo. Therefore, accurate and reproducible measurements of D-serine are critical to understanding its regulation by SR. Several methods for measuring D-serine have been employed, and significant issues related to validation and standardization remain unresolved. Further insights into the intracellular transport and tissue-specific compartmentalization of D-serine within the CNS will aid in the understanding of the role of D-serine in the pathogenesis of ALS.
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98
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Yamanaka M, Miyoshi Y, Ohide H, Hamase K, Konno R. d-Amino acids in the brain and mutant rodents lacking d-amino-acid oxidase activity. Amino Acids 2012; 43:1811-21. [DOI: 10.1007/s00726-012-1384-x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Accepted: 07/30/2012] [Indexed: 12/27/2022]
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99
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Billard JM. d-Amino acids in brain neurotransmission and synaptic plasticity. Amino Acids 2012; 43:1851-60. [DOI: 10.1007/s00726-012-1346-3] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/16/2012] [Indexed: 01/25/2023]
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100
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Wolosker H, Mori H. Serine racemase: an unconventional enzyme for an unconventional transmitter. Amino Acids 2012; 43:1895-904. [PMID: 22847782 DOI: 10.1007/s00726-012-1370-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Accepted: 07/14/2012] [Indexed: 12/19/2022]
Abstract
The discovery of large amounts of D-serine in the brain challenged the dogma that only L-amino acids are relevant for eukaryotes. The levels of D-serine in the brain are higher than many L-amino acids and account for as much as one-third of L-serine levels. Several studies in the last decades have demonstrated a role of D-serine as an endogenous agonist of N-methyl-D-aspartate receptors (NMDARs). D-Serine is required for NMDAR activity during normal neurotransmission as well as NMDAR overactivation that takes place in neurodegenerative conditions. Still, there are many unanswered questions about D-serine neurobiology, including regulation of its synthesis, release and metabolism. Here, we review the mechanisms of D-serine synthesis by serine racemase and discuss the lessons we can learn from serine racemase knockout mice, focusing on the roles attributed to D-serine and its cellular origin.
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Affiliation(s)
- Herman Wolosker
- Department of Biochemistry, B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 31096, Haifa, Israel.
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