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Suppressed expression of cystathionine β-synthase and smaller cerebellum in Wistar Kyoto rats. Brain Res 2015; 1624:208-213. [DOI: 10.1016/j.brainres.2015.07.043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2015] [Revised: 07/23/2015] [Accepted: 07/24/2015] [Indexed: 11/19/2022]
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Henríquez-Henríquez MP, Solari S, Quiroga T, Kim BI, Deckelbaum RJ, Worgall TS. Low serum sphingolipids in children with attention deficit-hyperactivity disorder. Front Neurosci 2015; 9:300. [PMID: 26379487 PMCID: PMC4548182 DOI: 10.3389/fnins.2015.00300] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 08/07/2015] [Indexed: 02/04/2023] Open
Abstract
Background: Attention deficit-hyperactivity disorder (ADHD) is the most prevalent neuropsychiatric condition in childhood. ADHD is a multifactorial trait with a strong genetic component. One neurodevelopmental hypothesis is that ADHD is associated with a lag in brain maturation. Sphingolipids are essential for brain development and neuronal functioning, but their role in ADHD pathogenesis is unexplored. We hypothesized that serum sphingolipid levels distinguish ADHD patients from unaffected subjects. Methods: We characterized serum sphingolipid profiles of ADHD patients and two control groups: non-affected relatives and non-affected subjects without a family history of ADHD. Sphingolipids were measured by LC-MS/MS in 77 participants (28 ADHD patients, 28 related controls, and 21 unrelated controls). ADHD diagnosis was based on the Diagnostic and Statistical Manual of Mental Disorders (DSM IV-TR). Diagnostic criteria were assessed by two independent observers. Groups were compared by parametrical statistics. Results: Serum sphingomyelins C16:0, C18:0, C18:1, C24:1, ceramide C24:0, and deoxy-ceramide C24:1 were significantly decreased in ADHD patients at 20–30% relative reductions. In our sample, decreased serum sphingomyelin levels distinguished ADHD patients with 79% sensitivity and 78% specificity. Conclusions: Our results showed lower levels of all major serum sphingomyelins in ADHD. These findings may reflect brain maturation and affect neuro-functional pathways characteristic for ADHD.
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Affiliation(s)
- Marcela P Henríquez-Henríquez
- Department of Pediatrics, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University New York, NY, USA ; Department of Clinical Laboratories, School of Medicine, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Sandra Solari
- Department of Clinical Laboratories, School of Medicine, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Teresa Quiroga
- Department of Clinical Laboratories, School of Medicine, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Benjamin I Kim
- Department of Pathology and Cell Biology, Columbia University New York, NY, USA
| | - Richard J Deckelbaum
- Department of Pediatrics, Institute of Human Nutrition, College of Physicians and Surgeons, Columbia University New York, NY, USA
| | - Tilla S Worgall
- Department of Pathology and Cell Biology, Columbia University New York, NY, USA
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Blood D-serine levels as a predictive biomarker for the rapid antidepressant effects of the NMDA receptor antagonist ketamine. Psychopharmacology (Berl) 2014; 231:4081-2. [PMID: 25189793 DOI: 10.1007/s00213-014-3735-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Accepted: 08/25/2014] [Indexed: 01/18/2023]
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54
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Arora G, Tiwari P, Mandal RS, Gupta A, Sharma D, Saha S, Singh R. High throughput screen identifies small molecule inhibitors specific for Mycobacterium tuberculosis phosphoserine phosphatase. J Biol Chem 2014; 289:25149-65. [PMID: 25037224 DOI: 10.1074/jbc.m114.597682] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The emergence of drug-resistant strains of Mycobacterium tuberculosis makes identification and validation of newer drug targets a global priority. Phosphoserine phosphatase (PSP), a key essential metabolic enzyme involved in conversion of O-phospho-l-serine to l-serine, was characterized in this study. The M. tuberculosis genome harbors all enzymes involved in l-serine biosynthesis including two PSP homologs: Rv0505c (SerB1) and Rv3042c (SerB2). In the present study, we have biochemically characterized SerB2 enzyme and developed malachite green-based high throughput assay system to identify SerB2 inhibitors. We have identified 10 compounds that were structurally different from known PSP inhibitors, and few of these scaffolds were highly specific in their ability to inhibit SerB2 enzyme, were noncytotoxic against mammalian cell lines, and inhibited M. tuberculosis growth in vitro. Surface plasmon resonance experiments demonstrated the relative binding for these inhibitors. The two best hits identified in our screen, clorobiocin and rosaniline, were bactericidal in activity and killed intracellular bacteria in a dose-dependent manner. We have also identified amino acid residues critical for these SerB2-small molecule interactions. This is the first study where we validate that M. tuberculosis SerB2 is a druggable and suitable target to pursue for further high throughput assay system screening.
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Affiliation(s)
- Garima Arora
- From the Vaccine and Infectious Disease Research Centre, Translational Health Science and Technology Institute, Gurgaon 122016, Haryana, India, the Symbiosis School of Biomedical Sciences, Symbiosis International University, Lavale, Maharashtra 412115, India
| | - Prabhakar Tiwari
- From the Vaccine and Infectious Disease Research Centre, Translational Health Science and Technology Institute, Gurgaon 122016, Haryana, India
| | - Rahul Shubhra Mandal
- the Biomedical Informatics Center, National Institute of Cholera and Enteric Diseases, Kolkata, West Bengal 700010, India
| | - Arpit Gupta
- the CSIR-Institute of Microbial Technology, Chandigarh, 160036, India, and
| | - Deepak Sharma
- the CSIR-Institute of Microbial Technology, Chandigarh, 160036, India, and
| | - Sudipto Saha
- the Bioinformatics Centre, Bose Institute, Kolkata, West Bengal 700054, India
| | - Ramandeep Singh
- From the Vaccine and Infectious Disease Research Centre, Translational Health Science and Technology Institute, Gurgaon 122016, Haryana, India,
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Kim HY, Huang BX, Spector AA. Phosphatidylserine in the brain: metabolism and function. Prog Lipid Res 2014; 56:1-18. [PMID: 24992464 DOI: 10.1016/j.plipres.2014.06.002] [Citation(s) in RCA: 212] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 06/18/2014] [Accepted: 06/21/2014] [Indexed: 01/08/2023]
Abstract
Phosphatidylserine (PS) is the major anionic phospholipid class particularly enriched in the inner leaflet of the plasma membrane in neural tissues. PS is synthesized from phosphatidylcholine or phosphatidylethanolamine by exchanging the base head group with serine, and this reaction is catalyzed by phosphatidylserine synthase 1 and phosphatidylserine synthase 2 located in the endoplasmic reticulum. Activation of Akt, Raf-1 and protein kinase C signaling, which supports neuronal survival and differentiation, requires interaction of these proteins with PS localized in the cytoplasmic leaflet of the plasma membrane. Furthermore, neurotransmitter release by exocytosis and a number of synaptic receptors and proteins are modulated by PS present in the neuronal membranes. Brain is highly enriched with docosahexaenoic acid (DHA), and brain PS has a high DHA content. By promoting PS synthesis, DHA can uniquely expand the PS pool in neuronal membranes and thereby influence PS-dependent signaling and protein function. Ethanol decreases DHA-promoted PS synthesis and accumulation in neurons, which may contribute to the deleterious effects of ethanol intake. Improvement of some memory functions has been observed in cognitively impaired subjects as a result of PS supplementation, but the mechanism is unclear.
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Affiliation(s)
- Hee-Yong Kim
- Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410, United States.
| | - Bill X Huang
- Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410, United States
| | - Arthur A Spector
- Laboratory of Molecular Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-9410, United States
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Sertbaş M, Ülgen K, Çakır T. Systematic analysis of transcription-level effects of neurodegenerative diseases on human brain metabolism by a newly reconstructed brain-specific metabolic network. FEBS Open Bio 2014; 4:542-53. [PMID: 25061554 PMCID: PMC4104795 DOI: 10.1016/j.fob.2014.05.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 05/23/2014] [Accepted: 05/27/2014] [Indexed: 01/02/2023] Open
Abstract
Network-oriented analysis is essential to identify those parts of a cell affected by a given perturbation. The effect of neurodegenerative perturbations in the form of diseases of brain metabolism was investigated by using a newly reconstructed brain-specific metabolic network. The developed stoichiometric model correctly represents healthy brain metabolism, and includes 630 metabolic reactions in and between astrocytes and neurons, which are controlled by 570 genes. The integration of transcriptome data of six neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, schizophrenia) with the model was performed to identify reporter features specific and common for these diseases, which revealed metabolites and pathways around which the most significant changes occur. The identified metabolites are potential biomarkers for the pathology of the related diseases. Our model indicated perturbations in oxidative stress, energy metabolism including TCA cycle and lipid metabolism as well as several amino acid related pathways, in agreement with the role of these pathways in the studied diseases. The computational prediction of transcription factors that commonly regulate the reporter metabolites was achieved through binding-site analysis. Literature support for the identified transcription factors such as USF1, SP1 and those from FOX families are known from the literature to have regulatory roles in the identified reporter metabolic pathways as well as in the neurodegenerative diseases. In essence, the reconstructed brain model enables the elucidation of effects of a perturbation on brain metabolism and the illumination of possible machineries in which a specific metabolite or pathway acts as a regulatory spot for cellular reorganization.
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Key Words
- AD, Alzheimer’s disease
- ALS, amyotrophic lateral sclerosis
- Brain metabolic network
- Computational systems biology
- FBA, flux balance analysis
- GABA, gamma-aminobutyric acid
- HD, Huntington’s disease
- KIV, ketoisovalerate
- KLF, Krüppel-like factor
- KMV, alpha-keto-beta-methylvalerate
- MS, multiple sclerosis
- Neurodegenerative diseases
- Neurometabolism
- PCA, principal component analysis
- PD, Parkinson’s disease
- RMA, reporter metabolite analysis
- RPA, reporter pathway analysis
- Reporter metabolite
- SCHZ, schizophrenia
- TCA, tricarboxylic acid
- Transcriptome
- USF, upstream stimulatory factor
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Affiliation(s)
- Mustafa Sertbaş
- Department of Bioengineering, Gebze Institute of Technology, Gebze, Kocaeli, Turkey
- Department of Chemical Engineering, Boğaziçi University, 34342 Bebek, Istanbul, Turkey
| | - Kutlu Ülgen
- Department of Chemical Engineering, Boğaziçi University, 34342 Bebek, Istanbul, Turkey
| | - Tunahan Çakır
- Department of Bioengineering, Gebze Institute of Technology, Gebze, Kocaeli, Turkey
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57
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Brondolin M, Berger S, Reinke M, Tanaka H, Ohshima T, Fuβ B, Hoch M. Identification and expression analysis of the zebrafish homologs of the ceramide synthase gene family. Dev Dyn 2013. [PMID: 23203913 DOI: 10.1002/dvdy.23913] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Sphingolipids represent a major class of lipids which both serve as structural components of membranes and as bioactive molecules involved in lipid signaling. Ceramide synthases (cers) reside in the center of sphingolipid metabolism by producing ceramide through de novo synthesis or degradative pathways. While the six mammalian cers family members have been extensively studied in cell culture and in adult tissues, a systematic analysis of cers expression and function during embryogenesis is still lacking. RESULTS Using bioinformatic and phylogenetic analysis, we identified nine highly conserved homologs of the vertebrate cers gene family in the zebrafish genome. A systematic expression analysis throughout five developmental stages indicates that, whereas until 48 hours post fertilization most zebrafish cers homologs are expressed in distinct patterns, e.g., in the intermediate cell mass and the pronephric duct, they show a highly overlapping expression during later stages of embryonic development, mostprominently in the developing brain. CONCLUSIONS In this study, the expression of the cers gene homologs is comprehensively analyzed for the first time during vertebrate embryogenesis. Our data indicate that each embryonic tissue has a unique profile of cers expression during zebrafish embryogenesis suggesting tissue-specific profiles of ceramides and their derivatives.
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58
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Ishibashi Y, Kohyama-Koganeya A, Hirabayashi Y. New insights on glucosylated lipids: metabolism and functions. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1831:1475-85. [PMID: 23770033 DOI: 10.1016/j.bbalip.2013.06.001] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 06/01/2013] [Accepted: 06/04/2013] [Indexed: 01/05/2023]
Abstract
Ceramide, cholesterol, and phosphatidic acid are major basic structures for cell membrane lipids. These lipids are modified with glucose to generate glucosylceramide (GlcCer), cholesterylglucoside (ChlGlc), and phosphatidylglucoside (PtdGlc), respectively. Glucosylation dramatically changes the functional properties of lipids. For instance, ceramide acts as a strong tumor suppressor that causes apoptosis and cell cycle arrest, while GlcCer has an opposite effect, downregulating ceramide activities. All glucosylated lipids are enriched in lipid rafts or microdomains and play fundamental roles in a variety of cellular processes. In this review, we discuss the biological functions and metabolism of these three glucosylated lipids.
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Affiliation(s)
- Yohei Ishibashi
- Laboratory for Molecular Membrane Neuroscience, RIKEN Brain Science Institute, Wako, Saitama, Japan
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59
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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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60
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Fong B, Ma L, Norris C. Analysis of phospholipids in infant formulas using high performance liquid chromatography-tandem mass spectrometry. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2013; 61:858-865. [PMID: 23297796 DOI: 10.1021/jf304877k] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Phospholipids have been used widely in the food industry as emulsifiers, but it is their biological and nutritional function that has been the focus over recent years. The recognition of the importance of phospholipids and sphingomyelin for infant development has led to an increase in the number of infant formulas claiming to contain these complex lipid components. Therefore, the ability to measure these lipids in infant formulas and dairy-derived complex lipid ingredients for fortification purposes is important. A high-performance liquid chromatography-tandem mass spectrometry method that quantifies phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and sphingomyelin found in infant formulas and dairy-derived complex lipid ingredients is described. The method uses external standards of similar fatty acid profile for calibration. The recovery of phospholipids ranged from 92% to 102% with a method repeatability coefficient of variation of 6-10%. In addition to the specificity and selectivity of the method, details of the molecular species in the individual phospholipid classes are available using this method.
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Affiliation(s)
- Bertram Fong
- Fonterra Research Centre, Palmerston North 4412, New Zealand.
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61
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Kolter T. Ganglioside biochemistry. ISRN BIOCHEMISTRY 2012; 2012:506160. [PMID: 25969757 PMCID: PMC4393008 DOI: 10.5402/2012/506160] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Accepted: 10/09/2012] [Indexed: 01/21/2023]
Abstract
Gangliosides are sialic acid-containing glycosphingolipids. They occur especially on the cellular surfaces of neuronal cells, where they form a complex pattern, but are also found in many other cell types. The paper provides a general overview on their structures, occurrence, and metabolism. Key functional, biochemical, and pathobiochemical aspects are summarized.
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Affiliation(s)
- Thomas Kolter
- Program Unit Membrane Biology & Lipid Biochemistry, LiMES, University of Bonn, Gerhard-Domagk Straße 1, 53121 Bonn, Germany
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62
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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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63
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Mauri M, Lentini D, Gravati M, Foudah D, Biella G, Costa B, Toselli M, Parenti M, Coco S. Mesenchymal stem cells enhance GABAergic transmission in co-cultured hippocampal neurons. Mol Cell Neurosci 2012; 49:395-405. [PMID: 22388097 DOI: 10.1016/j.mcn.2012.02.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 02/14/2012] [Accepted: 02/15/2012] [Indexed: 12/14/2022] Open
Abstract
Bone marrow-derived mesenchymal stem cells (MSCs) are multipotent stem cells endowed with neurotrophic potential combined with immunological properties, making them a promising therapeutic tool for neurodegenerative disorders. However, the mechanisms through which MSCs promote the neurological recovery following injury or inflammation are still largely unknown, although cell replacement and paracrine mechanisms have been hypothesized. In order to find out what are the mechanisms of the trophic action of MSCs, as compared to glial cells, on CNS neurons, we set up a co-culture system where rat MSCs (or cortical astrocytes) were used as a feeding layer for hippocampal neurons without any direct contact between the two cell types. The analysis of hippocampal synaptogenesis, synaptic vesicle recycling and electrical activity show that MSCs were capable to support morphological and functional neuronal differentiation. The proliferation of hippocampal glial cells induced by the release of bioactive substance(s) from MSCs was necessary for neuronal survival. Furthermore, MSCs selectively increased hippocampal GABAergic pre-synapses. This effect was paralleled with a higher expression of the potassium/chloride KCC2 co-transporter and increased frequency and amplitude of mIPSCs and sIPSCs. The enhancement of GABA synapses was impaired by the treatment with K252a, a Trk/neurotrophin receptor blocker, and by TrkB receptor bodies hence suggesting the involvement of BDNF as a mediator of such effects. The results obtained here indicate that MSC-secreted factors induce glial-dependent neuronal survival and trigger an augmented GABAergic transmission in hippocampal cultures, highlighting a new effect by which MSCs could promote CNS repair. Our results suggest that MSCs may be useful in those neurological disorders characterized by an impairment of excitation versus inhibition balance.
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Affiliation(s)
- Mario Mauri
- Department of Experimental Medicine, University of Milano-Bicocca, Via Cadore 48, 20900 Monza, Italy
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Garofalo K, Penno A, Schmidt BP, Lee HJ, Frosch MP, von Eckardstein A, Brown RH, Hornemann T, Eichler FS. Oral L-serine supplementation reduces production of neurotoxic deoxysphingolipids in mice and humans with hereditary sensory autonomic neuropathy type 1. J Clin Invest 2012; 121:4735-45. [PMID: 22045570 DOI: 10.1172/jci57549] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2011] [Accepted: 09/07/2011] [Indexed: 11/17/2022] Open
Abstract
Hereditary sensory and autonomic neuropathy type 1 (HSAN1) causes sensory loss that predominantly affects the lower limbs, often preceded by hyperpathia and spontaneous shooting or lancinating pain. It is caused by several missense mutations in the genes encoding 2 of the 3 subunits of the enzyme serine palmitoyltransferase (SPT). The mutant forms of the enzyme show a shift from their canonical substrate L-serine to the alternative substrate L-alanine. This shift leads to increased formation of neurotoxic deoxysphingolipids (dSLs). Our initial analysis showed that in HEK cells transfected with SPTLC1 mutants, dSL generation was modulated in vitro in the presence of various amino acids. We therefore examined whether in vivo specific amino acid substrate supplementation influenced dSL levels and disease severity in HSAN1. In mice bearing a transgene expressing the C133W SPTLC1 mutant linked to HSAN1, a 10% L-serine–enriched diet reduced dSL levels. L-serine supplementation also improved measures of motor and sensory performance as well as measures of male fertility. In contrast, a 10% L-alanine–enriched diet increased dSL levels and led to severe peripheral neuropathy. In a pilot study with 14 HSAN1 patients, L-serine supplementation similarly reduced dSL levels. These observations support the hypothesis that an altered substrate selectivity of the mutant SPT is key to the pathophysiology of HSAN1 and raise the prospect of l-serine supplementation as a first treatment option for this disorder.
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Affiliation(s)
- Kevin Garofalo
- MGH Neuroscience Center, Department of Neurology, Harvard Medical School, Boston, Massachusetts, USA
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65
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Castro-Chavez F. Defragged Binary I Ching Genetic Code Chromosomes Compared to Nirenberg's and Transformed into Rotating 2D Circles and Squares and into a 3D 100% Symmetrical Tetrahedron Coupled to a Functional One to Discern Start From Non-Start Methionines through a Stella Octangula. ACTA ACUST UNITED AC 2012; 2012. [PMID: 23431415 DOI: 10.7243/2050-2273-1-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND: Three binary representations of the genetic code according to the ancient I Ching of Fu-Xi will be presented, depending on their defragging capabilities by pairing based on three biochemical properties of the nucleic acids: H-bonds, Purine/Pyrimidine rings, and the Keto-enol/Amino-imino tautomerism, yielding the last pair a 32/32 single-strand self-annealed genetic code and I Ching tables. METHODS: Our working tool is the ancient binary I Ching's resulting genetic code chromosomes defragged by vertical and by horizontal pairing, reverse engineered into non-binaries of 2D rotating 4×4×4 circles and 8×8 squares and into one 3D 100% symmetrical 16×4 tetrahedron coupled to a functional tetrahedron with apical signaling and central hydrophobicity (codon formula: 4[1(1)+1(3)+1(4)+4(2)]; 5:5, 6:6 in man) forming a stella octangula, and compared to Nirenberg's 16×4 codon table (1965) pairing the first two nucleotides of the 64 codons in axis y. RESULTS: One horizontal and one vertical defragging had the start Met at the center. Two, both horizontal and vertical pairings produced two pairs of 2×8×4 genetic code chromosomes naturally arranged (M and I), rearranged by semi-introversion of central purines or pyrimidines (M' and I') and by clustering hydrophobic amino acids; their quasi-identity was disrupted by amino acids with odd codons (Met and Tyr pairing to Ile and TGA Stop); in all instances, the 64-grid 90° rotational ability was restored. CONCLUSIONS: We defragged three I Ching representations of the genetic code while emphasizing Nirenberg's historical finding. The synthetic genetic code chromosomes obtained reflect the protective strategy of enzymes with a similar function, having both humans and mammals a biased G-C dominance of three H-bonds in the third nucleotide of their most used codons per amino acid, as seen in one chromosome of the i, M and M' genetic codes, while a two H-bond A-T dominance was found in their complementary chromosome, as seen in invertebrates and plants. The reverse engineering of chromosome I' into 2D rotating circles and squares was undertaken, yielding a 100% symmetrical 3D geometry which was coupled to a previously obtained genetic code tetrahedron in order to differentiate the start methionine from the methionine that is acting as a codifying non-start codon.
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Affiliation(s)
- Fernando Castro-Chavez
- Department of Medicine, Atherosclerosis and Vascular Medicine Section, Baylor College of Medicine, Houston, TX, USA
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66
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Hirabayashi Y. A world of sphingolipids and glycolipids in the brain--novel functions of simple lipids modified with glucose. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2012; 88:129-143. [PMID: 22498977 PMCID: PMC3406307 DOI: 10.2183/pjab.88.129] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Glycosphingolipids (GSLs) are present on cell surface membranes and are particularly abundant in the brain. Since over 300-400 GSLs are synthesized from glucosylceramide (GlcCer), GlcCer is believed to only serve as the source of most GSLs, including sialic acid-containing GSLs or gangliosides, in the brain. Recent studies, however, suggest that GlcCer itself plays a role in the heat stress response, as it functions as a glucose donor for the synthesis of cholesterylglucoside, a lipid mediator in heat stress responses in animals. GlcCer in adipose tissues is also thought to be involved in mechanisms that regulate energy (sugar and lipid) metabolism. Our extensive structural study revealed an additional novel glucosylated membrane lipid, called phosphatidylglucoside, in developing rodent brains and human neutrophils. These lipids, all modified with glucose, are enriched in lipid rafts and play important roles in basic cellular processes. Here, I summarize the recent progress regarding these glucosylated lipids and their biosynthesis and regulation in the central nervous system (CNS).
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Affiliation(s)
- Yoshio Hirabayashi
- Laboratory for Molecular Membrane Neuroscience, Brain Science Institute, RIKEN, Saitama, Japan.
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Paoletti L, Elena C, Domizi P, Banchio C. Role of Phosphatidylcholine during Neuronal differentiation. IUBMB Life 2011; 63:714-20. [DOI: 10.1002/iub.521] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2011] [Accepted: 05/19/2011] [Indexed: 12/15/2022]
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Chervyakov AV, Gulyaeva NV, Zakharova MN. D-amino acids in normal ageing and pathogenesis of neurodegenerative diseases. NEUROCHEM J+ 2011. [DOI: 10.1134/s1819712411020036] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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69
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Tachikawa M, Okamoto M, Hirose S, Yoneyama D, Akanuma SI, Terasaki T, Hosoya KI. Inner blood-retinal barrier mediates l-isomer-predominant transport of serine. J Pharm Sci 2011; 100:3892-903. [PMID: 21590774 DOI: 10.1002/jps.22626] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 03/29/2011] [Accepted: 04/26/2011] [Indexed: 12/21/2022]
Abstract
D-serine, a coagonist for N-methyl-D-aspartate-type glutamate receptors, which mediate visual signal transmission, is thought to be generated from L-serine via serine racemase in the retina. However, the source of L-serine and D-serine in the retina are yet to be determined. The purpose of the present study was to investigate the characteristics of the blood-to-retina transport of serine at the inner blood-retinal barrier (BRB). In vivo study revealed the blood-to-retina transport of [(3) H]L-serine with an influx clearance of 49.9 μL/(min·g retina), which is greater than that of [(3) H]D-serine. This was consistent with the L-isomer-predominant uptake of serine by conditionally immortalized rat retinal capillary endothelial cell line (TR-iBRB2 cells), an in vitro inner BRB model. [(3) H]L-Serine and [(3) H]D-serine uptake by TR-iBRB2 cells took place in an Na(+)-dependent and a concentration-dependent manner with Michaelis constant values of 97.5 μM and 9.63 mM, respectively. The uptake process of [(3) H]L-serine and [(3) H]D-serine was significantly inhibited by system ASC (alanine-serine-cysteine) substrates. Polymerase chain reaction analysis and immunocytochemistry revealed the expression of ASC transporters ASCT1 and ASCT2 in TR-iBRB2 cells. These results suggest that the system ASC at the inner BRB is a potent pathway for supplying serine in the form of the L-isomer from the circulating blood to the retina.
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Affiliation(s)
- Masanori Tachikawa
- Department of Pharmaceutics, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
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70
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Wolosker H. Serine racemase and the serine shuttle between neurons and astrocytes. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1558-66. [PMID: 21224019 DOI: 10.1016/j.bbapap.2011.01.001] [Citation(s) in RCA: 105] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2010] [Revised: 01/02/2011] [Accepted: 01/04/2011] [Indexed: 11/24/2022]
Abstract
d-Serine is a brain-enriched d-amino acid that works as a transmitter-like molecule by physiologically activating NMDA receptors. Synthesis of d-serine is carried out by serine racemase (SR), a pyridoxal 5'-phosphate-dependent enzyme. In addition to carry out racemization, SR α,β-eliminates water from l- or d-serine, generating pyruvate and NH(4)(+). Here I review the main mechanisms regulating SR activity and d-serine dynamics in the brain. I propose a role for SR in a novel form of astrocyte-neuron communication-the "serine shuttle", whereby astrocytes synthesize and export l-serine required for the synthesis of d-serine by the predominantly neuronal SR. d-Serine synthesized and released by neurons can be further taken up by astrocytes for storage and activity-dependent release. I discuss how SR α,β-elimination with d-serine itself may limit the achievable intracellular d-serine concentration, providing a mechanistic rationale on why neurons do not store as much d-serine as astrocytes. The higher content of d-serine in astrocytes appears to be related to increased d-serine stability, for their low SR expression will prevent substantial d-serine metabolism via α,β-elimination. SR and the serine shuttle pathway are therapeutic targets in neurodegenerative diseases in which NMDA receptor dysfunction plays pathological roles. This article is part of a Special Issue entitled: Pyridoxal Phospate Enzymology.
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Affiliation(s)
- Herman Wolosker
- Department of Biochemistry, B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
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Yang JH, Wada A, Yoshida K, Miyoshi Y, Sayano T, Esaki K, Kinoshita MO, Tomonaga S, Azuma N, Watanabe M, Hamase K, Zaitsu K, Machida T, Messing A, Itohara S, Hirabayashi Y, Furuya S. Brain-specific Phgdh deletion reveals a pivotal role for L-serine biosynthesis in controlling the level of D-serine, an N-methyl-D-aspartate receptor co-agonist, in adult brain. J Biol Chem 2010; 285:41380-90. [PMID: 20966073 DOI: 10.1074/jbc.m110.187443] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammalian brain, D-serine is synthesized from L-serine by serine racemase, and it functions as an obligatory co-agonist at the glycine modulatory site of N-methyl-D-aspartate (NMDA)-selective glutamate receptors. Although diminution in D-serine level has been implicated in NMDA receptor hypofunction, which is thought to occur in schizophrenia, the source of the precursor L-serine and its role in D-serine metabolism in adult brain have yet to be determined. We investigated whether L-serine synthesized in brain via the phosphorylated pathway is essential for D-serine synthesis by generating mice with a conditional deletion of D-3-phosphoglycerate dehydrogenase (Phgdh; EC 1.1.1.95). This enzyme catalyzes the first step in L-serine synthesis via the phosphorylated pathway. HPLC analysis of serine enantiomers demonstrated that both L- and D-serine levels were markedly decreased in the cerebral cortex and hippocampus of conditional knock-out mice, whereas the serine deficiency did not alter protein expression levels of serine racemase and NMDA receptor subunits in these regions. The present study provides definitive proof that L-serine-synthesized endogenously via the phosphorylated pathway is a key rate-limiting factor for maintaining steady-state levels of D-serine in adult brain. Furthermore, NMDA-evoked transcription of Arc, an immediate early gene, was diminished in the hippocampus of conditional knock-out mice. Thus, this study demonstrates that in mature neuronal circuits L-serine availability determines the rate of D-serine synthesis in the forebrain and controls NMDA receptor function at least in the hippocampus.
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Affiliation(s)
- Jung Hoon Yang
- Laboratory of Metabolic Regulation Research, Kyushu University Bio-Architecture Center, Fukuoka 812-8581, Japan
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Paila YD, Ganguly S, Chattopadhyay A. Metabolic Depletion of Sphingolipids Impairs Ligand Binding and Signaling of Human Serotonin1A Receptors. Biochemistry 2010; 49:2389-97. [DOI: 10.1021/bi1001536] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Yamuna Devi Paila
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
| | - Sourav Ganguly
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
| | - Amitabha Chattopadhyay
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
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Geiger O, González-Silva N, López-Lara IM, Sohlenkamp C. Amino acid-containing membrane lipids in bacteria. Prog Lipid Res 2010; 49:46-60. [DOI: 10.1016/j.plipres.2009.08.002] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Shigemi K, Tsuneyoshi Y, Yamada S, Kabuki Y, Hayamizu K, Denbow DM, Furuse M. Oral administration of L-serine reduces the locomotor activity of socially isolated rats. Neurosci Lett 2009; 468:75-9. [PMID: 19874867 DOI: 10.1016/j.neulet.2009.10.068] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2009] [Revised: 10/21/2009] [Accepted: 10/21/2009] [Indexed: 10/20/2022]
Abstract
L-Serine is considered a functional amino acid in the central nervous system, since intracerebroventricular injection of L-serine induced sedative and hypnotic effects in neonatal chicks exposed to acute stressful conditions. Accordingly, L-serine is a candidate anti-stress factor, but the effect of daily intake of L-serine on behavior of animals exposed to chronic stress has not been investigated. In the present study, we exposed rats to social isolation stress for 4 weeks, and home cage test and open field test were concluded to evaluate the effect of L-serine on behavior. To investigate L-serine supplementation modifies the brain L-serine and its metabolite contents, free amino acid contents were measured by a high performance liquid chromatography. L-Serine in the drinking water increased L-serine levels in some brain areas, but changes in its metabolites were almost negligible. L-Serine decreased locomotor activity in rats exposed to a familiar environment. In addition, L-serine decreased exploratory behavior of isolated rats, even in a novel environment. Our results could suggest that daily intake of L-serine can attenuate symptoms induced by chronic stress.
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Affiliation(s)
- Kazutaka Shigemi
- Laboratory of Regulation in Metabolism and Behavior, Graduate School of Bioresources and Bioenvironmental Sciences, Kyushu University, Fukuoka 812-8581, Japan
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Shao Z, Kamboj A, Anderson CM. Functional and immunocytochemical characterization of D-serine transporters in cortical neuron and astrocyte cultures. J Neurosci Res 2009; 87:2520-30. [PMID: 19382234 DOI: 10.1002/jnr.22086] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
D-serine is an endogenous coagonist of N-methyl-D-aspartate (NMDA) receptors that plays an important role in synaptic function, neuronal development, and excitotoxicity. Mechanisms of D-serine transport are important in regulation of extracellular D-serine concentration and therefore of these critical processes. D-serine can be transported with low affinity through the Na(+)-dependent amino acid transporter termed ASCT2, whereas high-affinity D-serine uptake has been reported through the Na(+)-independent transporter termed asc-1. We investigated immunoreactivity for ASCT2 and asc-1 and D-serine transport kinetics in cultured cortical neurons and astrocytes to gain insight into how D-serine transporters regulate CNS D-serine levels. Both neurons and astrocytes exhibited low-affinity Na(+)-dependent D-serine uptake (K(T) > 1 mM) with broad substrate selectivity that was consistent with uptake through ASCT2. Both neurons and astrocytes also stained positively for ASCT2 in immunocytochemistry studies. Neurons but not astrocytes stained positively for the high-affinity D-serine transporter asc-1, but no evidence of functional asc-1 could be detected in neurons with conditions that produced such activity in cortical synaptosomes. These data support ASCT2 function in both neuron and astrocyte cultures and identify a discrepancy between observed asc-1 immunoreactivity and lack of functional asc-1 activity in neuron cultures. Together these findings further our knowledge of the processes that govern D-serine regulation.
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Affiliation(s)
- Zongjun Shao
- Department of Pharmacology and Therapeutics, University of Manitoba, and Division of Neurodegenerative Disorders, St. Boniface Hospital Research Center, Manitoba, Canada
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Kawakami Y, Yoshida K, Yang JH, Suzuki T, Azuma N, Sakai K, Hashikawa T, Watanabe M, Yasuda K, Kuhara S, Hirabayashi Y, Furuya S. Impaired neurogenesis in embryonic spinal cord of Phgdh knockout mice, a serine deficiency disorder model. Neurosci Res 2009; 63:184-93. [DOI: 10.1016/j.neures.2008.12.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Revised: 11/14/2008] [Accepted: 12/02/2008] [Indexed: 10/21/2022]
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Kinoshita MO, Shinoda Y, Sakai K, Hashikawa T, Watanabe M, Machida T, Hirabayashi Y, Furuya S. Selective upregulation of 3-phosphoglycerate dehydrogenase (Phgdh) expression in adult subventricular zone neurogenic niche. Neurosci Lett 2009; 453:21-6. [PMID: 19429008 DOI: 10.1016/j.neulet.2009.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2008] [Revised: 01/21/2009] [Accepted: 02/01/2009] [Indexed: 02/06/2023]
Abstract
In the adult rodent brain, constitutive neurogenesis occurs in two restricted regions, the subventricular zone (SVZ) of the lateral ventricle and the subgranular zone of the hippocampal dentate gyrus, where multipotent neural stem/progenitor cells generate new neurons. Using Western blotting and immunohistochemistry for established markers, we demonstrated that the expression of 3-phosphoglycerate dehydrogenase (Phgdh), an enzyme involved in de novo synthesis of l-serine, was upregulated in the SVZ. The expression was selective to cells having morphological features and expressing markers of astrocyte-like primary neural stem cells (type B cells) and their progeny, actively proliferating progenitors (type C cells). By contrast, Phgdh protein expression was virtually absent in committed neuronal precursors (type A cells) derived from type C cells. High levels of Phgdh were also expressed by glial tube cells located in the rostral migratory stream (RMS). Interestingly, ensheathment of type A cells by these Phgdh-expressing cells was persistent in the SVZ and RMS, suggesting that l-serine mediates trophic support for type A cells via these glial cells. In vitro neurosphere assays confirmed that growth-factor-responsive, transient amplifying neural progenitors in the SVZ, but not differentiated neurons, expressed Phgdh. In the aged brain, a decline in Phgdh expression was evident in type B and C cells of the SVZ. These observations support the notion that availability of l-serine within neural stem/progenitor cells may be a critical factor for neurogenesis in developing and adult brain.
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Affiliation(s)
- Masami O Kinoshita
- Hirabayashi Research Unit, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan
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Gliddon CM, Shao Z, LeMaistre JL, Anderson CM. Cellular distribution of the neutral amino acid transporter subtype ASCT2 in mouse brain. J Neurochem 2008; 108:372-83. [PMID: 19012749 DOI: 10.1111/j.1471-4159.2008.05767.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
ASCT2 is an ASC (alanine-, serine-, cysteine-preferring) neutral amino acid exchanger that may regulate CNS function by transporting amino acid substrates including L-serine, L-cysteine, L-glutamine, L-glutamate and D-serine. Despite the potentially important role of ASCT2 in influencing metabolic and signaling functions of these amino acids in brain, there has been little description of its distribution in brain tissue. We employed a commercially available human ASCT2 antibody in immunohistochemistry studies in adult mouse brain and found a wide regional distribution for ASCT2 that was limited to dendrites labeled by anti-microtubule-associated protein-2 in cortex, hippocampus and striatum. No ASCT2 immunoreactivity was observed in areas labeled by antibodies against a neuronal cell body marker (NeuN), or either of the astrocyte markers, glial fibrillary acidic protein or S100beta. In cerebellum both Purkinje cell bodies and dendrites were positive for ASCT2 immunoreactivity. In support of a dendritic localization for ASCT2 in cortex, low affinity (K(T) > 1 mM), Na(+)-dependent D-serine and L-glutamine uptake characteristic of ASCT2-mediated transport was observed in P2 synaptosomal preparations. These results suggest that ASCT2 may be an important neuronal neutral amino acid transporter and highlight a discrepancy between findings of astrocyte ASCT2 function in tissue culture and brain in situ.
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Affiliation(s)
- Catherine M Gliddon
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada
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Wolosker H, Dumin E, Balan L, Foltyn VN. d-Amino acids in the brain: d-serine in neurotransmission and neurodegeneration. FEBS J 2008; 275:3514-26. [DOI: 10.1111/j.1742-4658.2008.06515.x] [Citation(s) in RCA: 226] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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