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Zhou J, Fan S, Cao Y, Zhu M, Han Y, Cao X, Li Y. Tumor necrosis factor-α suppresses the protein fractional synthesis rate of the small intestine stimulated by glutamine in rats. Exp Ther Med 2014; 9:547-552. [PMID: 25574232 PMCID: PMC4280961 DOI: 10.3892/etm.2014.2129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2014] [Accepted: 10/21/2014] [Indexed: 12/21/2022] Open
Abstract
The objective of this study was to examine whether and how TNF-α affects glutamine-enhanced protein synthesis and the expression of the amino acid transporter ASCT2 in the small intestine at the mRNA and protein levels. A total of 30 male Sprague-Dawley rats were randomly assigned into three groups, namely the total parenteral nutrition (TPN; control), glutamine-treated (Gln), and glutamine- and tumor necrosis factor-α (TNF-α)-treated (TNF-α) groups. At 30 min prior to examination, all rats were mainlined with [L-15N]leucine. The concentration of TNF-α in plasma and of glutamine in plasma and the small intestine was measured. The fractional synthesis rate (FSR) of protein and the mRNA and protein expression levels of ASCT2 in the small intestine were assessed. The level of TNF-α was highest in the TNF-α group and the glutamine concentration was elevated to a greater extent in the TNF-α group than in the other two groups. However, the FSR of protein in the small intestine was significantly higher in the Gln group compared with that in the TNF-α group. The mRNA and protein expression levels of ASCT2 in the experimental groups were significantly higher that those in the control group, but did not differ significantly between the Gln and TNF-α groups. These results indicate that TNF-α may attenuate glutamine-stimulated protein synthesis in the small intestine in the early stage of sepsis in rats. The mechanism may be that TNF-α inhibits the function of the glutamine transporter in the uptake the glutamine into target cells for protein synthesis. This inhibition may occur at or following protein translation.
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Affiliation(s)
- Jihong Zhou
- Department of Burns and Plastic Surgery, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, P.R. China
| | - Shengxian Fan
- Department of General Surgery, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, P.R. China
| | - Yacheng Cao
- Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210002, P.R. China
| | - Mingfang Zhu
- Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210002, P.R. China
| | - Yong Han
- Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu 210002, P.R. China
| | - Xueying Cao
- Department of Burns and Plastic Surgery, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, P.R. China
| | - Yousheng Li
- Department of General Surgery, Jinling Hospital, Nanjing University School of Medicine, Nanjing, Jiangsu 210002, P.R. China
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152
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Audette MC, Challis JRG, Jones RL, Sibley CP, Matthews SG. Synthetic glucocorticoid reduces human placental system a transport in women treated with antenatal therapy. J Clin Endocrinol Metab 2014; 99:E2226-33. [PMID: 25105735 DOI: 10.1210/jc.2014-2157] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
CONTEXT Synthetic glucocorticoids (sGCs) are routinely given to women with threatened preterm labor and have been linked to fetal growth restriction and developmental programming. Reductions in fetal growth are likely to be mediated by placental dysfunction, including altered nutrient transport. sGCs modify the system A neutral amino acid transporter in vitro, but there are no in vivo comparable data in human placenta. OBJECTIVE Because ∼ 30% of women who receive sGCs carry to term, our objective was to examine the short- and longer-term consequences of antenatal sGCs on placental system A transport. METHODS AND PATIENTS Placental tissue was collected from women treated with sGCs between 24 hours and 14 days before delivery (24h-14d), 14 days after treatment but before term (14d-term), or at term, compared with healthy term (control) deliveries to measure system A-mediated activity (Na(+)-dependent [(14)C]methylaminoisobutyric acid uptake per gram placenta) and mRNA expression. RESULTS After sGC treatment, system A activity was significantly reduced at term compared with both sGC placentas delivered 24h-14d and compared with controls. Placentae from women treated with sGCs who delivered between 14d-term also had significantly reduced system A activity compared with 24h-14d placentas. SLC38A1 and SLC38A2 mRNA expression was unaffected. However, SLC38A4 was significantly reduced by sGCs at term compared with placentas delivered between 14d-term. CONCLUSION We conclude that women who are at risk of preterm labor and receive sGCs but deliver at term have significantly reduced placental system A amino acid transporter activity. Altered placental transporter function could affect fetal growth and may contribute to developmental programming reported in both animal and clinical studies.
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Affiliation(s)
- Melanie C Audette
- Departments of Physiology (M.C.A., J.R.G.C., S.G.M.), Obstetrics and Gynecology (J.R.G.C., S.G.M.), and Medicine (M.C.A., J.R.G.C., S.G.M.) University of Toronto, Toronto, Ontario Canada M5A 1A8; and Maternal and Fetal Heath Research Centre (J.R.G.C., R.L.J., C.P.S.), School Institute of Human Development, Manchester Academic Health Sciences Centre, University of Manchester, St. Mary's Hospital, Central Manchester University Hospitals National Health Service Foundation Trust, Manchester M13 9WL, United Kingdom
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153
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Hägglund MGA, Hellsten SV, Bagchi S, Philippot G, Löfqvist E, Nilsson VCO, Almkvist I, Karlsson E, Sreedharan S, Tafreshiha A, Fredriksson R. Transport of L-glutamine, L-alanine, L-arginine and L-histidine by the neuron-specific Slc38a8 (SNAT8) in CNS. J Mol Biol 2014; 427:1495-1512. [PMID: 25451601 DOI: 10.1016/j.jmb.2014.10.016] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 09/30/2014] [Accepted: 10/17/2014] [Indexed: 11/19/2022]
Abstract
Glutamine transporters are important for regulating levels of glutamate and GABA in the brain. To date, six members of the SLC38 family (SNATs) have been characterized and functionally subdivided them into System A (SNAT1, SNAT2 and SNAT4) and System N (SNAT3, SNAT5 and SNAT7). Here we present the first functional characterization of SLC38A8, one of the previous orphan transporters from the family, and we suggest that the encoded protein should be named SNAT8 to adhere with the SNAT nomenclature. We show that SLC38A8 has preference for transporting L-glutamine, L-alanine, L-arginine, L-histidine and L-aspartate using a Na+-dependent transport mechanism and that the functional characteristics of SNAT8 have highest similarity to the known System A transporters. We also provide a comprehensive central nervous system expression profile in mouse brain for the Slc38a8 gene and the SNAT8 protein. We show that Slc38a8 (SNAT8) is expressed in all neurons, both excitatory and inhibitory, in mouse brain using in situ hybridization and immunohistochemistry. Furthermore, proximity ligation assay shows highly similar subcellular expression of SNAT7 and SNAT8. In conclusion, the neuronal SLC38A8 has a broad amino acid transport profile and is the first identified neuronal System A transporter. This suggests a key role of SNAT8 in the glutamine/glutamate (GABA) cycle in the brain.
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Affiliation(s)
- Maria G A Hägglund
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Sofie V Hellsten
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Sonchita Bagchi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Gaëtan Philippot
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Erik Löfqvist
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Victor C O Nilsson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Ingrid Almkvist
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Edvin Karlsson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Smitha Sreedharan
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Atieh Tafreshiha
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Husargatan 3, SE-75124 Uppsala, Sweden.
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154
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Lee IP, Evans AK, Yang C, Works MG, Kumar V, De Miguel Z, Manley NC, Sapolsky RM. Toxoplasma gondii is dependent on glutamine and alters migratory profile of infected host bone marrow derived immune cells through SNAT2 and CXCR4 pathways. PLoS One 2014; 9:e109803. [PMID: 25299045 PMCID: PMC4192591 DOI: 10.1371/journal.pone.0109803] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 09/12/2014] [Indexed: 01/16/2023] Open
Abstract
The obligate intracellular parasite, Toxoplasma gondii, disseminates through its host inside infected immune cells. We hypothesize that parasite nutrient requirements lead to manipulation of migratory properties of the immune cell. We demonstrate that 1) T. gondii relies on glutamine for optimal infection, replication and viability, and 2) T. gondii-infected bone marrow-derived dendritic cells (DCs) display both “hypermotility” and “enhanced migration” to an elevated glutamine gradient in vitro. We show that glutamine uptake by the sodium-dependent neutral amino acid transporter 2 (SNAT2) is required for this enhanced migration. SNAT2 transport of glutamine is also a significant factor in the induction of migration by the small cytokine stromal cell-derived factor-1 (SDF-1) in uninfected DCs. Blocking both SNAT2 and C-X-C chemokine receptor 4 (CXCR4; the unique receptor for SDF-1) blocks hypermotility and the enhanced migration in T. gondii-infected DCs. Changes in host cell protein expression following T. gondii infection may explain the altered migratory phenotype; we observed an increase of CD80 and unchanged protein level of CXCR4 in both T. gondii-infected and lipopolysaccharide (LPS)-stimulated DCs. However, unlike activated DCs, SNAT2 expression in the cytosol of infected cells was also unchanged. Thus, our results suggest an important role of glutamine transport via SNAT2 in immune cell migration and a possible interaction between SNAT2 and CXCR4, by which T. gondii manipulates host cell motility.
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Affiliation(s)
- I-Ping Lee
- Department of Biology, Stanford University, Stanford, California, United States of America
- * E-mail:
| | - Andrew K. Evans
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Cissy Yang
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Melissa G. Works
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Vineet Kumar
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore
| | - Zurine De Miguel
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Nathan C. Manley
- Department of Biology, Stanford University, Stanford, California, United States of America
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, California, United States of America
- Stanford Stroke Center and Stanford Institute for Neuro-Innovation and Translational Neurosciences, Stanford University School of Medicine, Stanford, California, United States of America
| | - Robert M. Sapolsky
- Department of Biology, Stanford University, Stanford, California, United States of America
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, California, United States of America
- Stanford Stroke Center and Stanford Institute for Neuro-Innovation and Translational Neurosciences, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, United States of America
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155
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Fike CD, Summar M, Aschner JL. L-citrulline provides a novel strategy for treating chronic pulmonary hypertension in newborn infants. Acta Paediatr 2014; 103:1019-26. [PMID: 24862864 DOI: 10.1111/apa.12707] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Revised: 03/23/2014] [Accepted: 05/23/2014] [Indexed: 02/05/2023]
Abstract
UNLABELLED Effective therapies are urgently needed for infants with forms of pulmonary hypertension that develop or persist beyond the first week of life. The L-arginine nitric oxide (NO) precursor, L-citrulline, improves NO signalling and ameliorates pulmonary hypertension in newborn animals. In vitro studies demonstrate that manipulating L-citrulline transport alters NO production. CONCLUSION Strategies that increase the supply and transport of L-citrulline merit pursuit as novel approaches to managing infants with chronic, progressive pulmonary hypertension.
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Affiliation(s)
- Candice D. Fike
- Department of Pediatrics; Vanderbilt University Medical Center; Nashville TN USA
- Monroe Carell Jr. Children's Hospital at Vanderbilt; Nashville TN USA
| | - Marshall Summar
- Division of Genetics and Metabolism; Children's National Medical Center; Washington DC USA
| | - Judy L. Aschner
- Department of Pediatrics; Albert Einstein College of Medicine and the Children's Hospital at Montefiore; New York NY USA
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156
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Laufenberg LJ, Pruznak AM, Navaratnarajah M, Lang CH. Sepsis-induced changes in amino acid transporters and leucine signaling via mTOR in skeletal muscle. Amino Acids 2014; 46:2787-98. [PMID: 25218136 DOI: 10.1007/s00726-014-1836-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 09/03/2014] [Indexed: 12/13/2022]
Abstract
The present study tested the hypothesis that sepsis-induced leucine (Leu) resistance in skeletal muscle is associated with a down-regulation of amino acid transporters important in regulating Leu flux or an impairment in the formation of the Leu-sensitive mTOR-Ragulator complex. Sepsis in adult male rats decreased basal protein synthesis in gastrocnemius, associated with a reduction in mTOR activation as indicated by decreased 4E-BP1 and S6K1 phosphorylation. The ability of oral Leu to increase protein synthesis and mTOR kinase after 1 h was largely prevented in sepsis. Sepsis increased CAT1, LAT2 and SNAT2 mRNA content two- to fourfold, but only the protein content for CAT1 (20 % decrease) differed significantly. Conversely, sepsis decreased the proton-assisted amino acid transporter (PAT)-2 mRNA by 60 %, but without a coordinate change in PAT2 protein. There was no sepsis or Leu effect on the protein content for RagA-D, LAMTOR-1 and -2, raptor, Rheb or mTOR in muscle. The binding of mTOR, PRAS40 and RagC to raptor did not differ for control and septic muscle in the basal condition; however, the Leu-induced decrease in PRAS40·raptor and increase in RagC·raptor seen in control muscle was absent in sepsis. The intracellular Leu concentration was increased in septic muscle, compared to basal control conditions, and oral Leu further increased the intracellular Leu concentration similarly in both control and septic rats. Hence, while alterations in select amino acid transporters are not associated with development of sepsis-induced Leu resistance, the Leu-stimulated binding of raptor with RagC and the recruitment of mTOR/raptor to the endosome-lysosomal compartment may partially explain the inability of Leu to fully activate mTOR and muscle protein synthesis.
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Affiliation(s)
- Lacee J Laufenberg
- Departments of Cellular and Molecular Physiology (H166), and Surgery, Penn State College of Medicine, Hershey, PA, 17033, USA
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157
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Synthesis and evaluation of 2-amino-5-(4-[18F]fluorophenyl)pent-4-ynoic acid ([18F]FPhPA): A novel 18F-labeled amino acid for oncologic PET imaging. Nucl Med Biol 2014; 41:660-9. [DOI: 10.1016/j.nucmedbio.2014.05.140] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/24/2014] [Accepted: 05/27/2014] [Indexed: 11/20/2022]
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158
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Pochini L, Scalise M, Galluccio M, Indiveri C. Membrane transporters for the special amino acid glutamine: structure/function relationships and relevance to human health. Front Chem 2014; 2:61. [PMID: 25157349 PMCID: PMC4127817 DOI: 10.3389/fchem.2014.00061] [Citation(s) in RCA: 175] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 07/16/2014] [Indexed: 12/26/2022] Open
Abstract
Glutamine together with glucose is essential for body's homeostasis. It is the most abundant amino acid and is involved in many biosynthetic, regulatory and energy production processes. Several membrane transporters which differ in transport modes, ensure glutamine homeostasis by coordinating its absorption, reabsorption and delivery to tissues. These transporters belong to different protein families, are redundant and ubiquitous. Their classification, originally based on functional properties, has recently been associated with the SLC nomenclature. Function of glutamine transporters is studied in cells over-expressing the transporters or, more recently in proteoliposomes harboring the proteins extracted from animal tissues or over-expressed in microorganisms. The role of the glutamine transporters is linked to their transport modes and coupling with Na+ and H+. Most transporters share specificity for other neutral or cationic amino acids. Na+-dependent co-transporters efficiently accumulate glutamine while antiporters regulate the pools of glutamine and other amino acids. The most acknowledged glutamine transporters belong to the SLC1, 6, 7, and 38 families. The members involved in the homeostasis are the co-transporters B0AT1 and the SNAT members 1, 2, 3, 5, and 7; the antiporters ASCT2, LAT1 and 2. The last two are associated to the ancillary CD98 protein. Some information on regulation of the glutamine transporters exist, which, however, need to be deepened. No information at all is available on structures, besides some homology models obtained using similar bacterial transporters as templates. Some models of rat and human glutamine transporters highlight very similar structures between the orthologs. Moreover the presence of glycosylation and/or phosphorylation sites located at the extracellular or intracellular faces has been predicted. ASCT2 and LAT1 are over-expressed in several cancers, thus representing potential targets for pharmacological intervention.
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Affiliation(s)
- Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Unit of Biochemistry and Molecular Biotechnology, University of Calabria Arcavacata di Rende, Italy
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159
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Zhou Y, Danbolt NC. Glutamate as a neurotransmitter in the healthy brain. J Neural Transm (Vienna) 2014; 121:799-817. [PMID: 24578174 PMCID: PMC4133642 DOI: 10.1007/s00702-014-1180-8] [Citation(s) in RCA: 529] [Impact Index Per Article: 52.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Accepted: 02/11/2014] [Indexed: 12/13/2022]
Abstract
Glutamate is the most abundant free amino acid in the brain and is at the crossroad between multiple metabolic pathways. Considering this, it was a surprise to discover that glutamate has excitatory effects on nerve cells, and that it can excite cells to their death in a process now referred to as "excitotoxicity". This effect is due to glutamate receptors present on the surface of brain cells. Powerful uptake systems (glutamate transporters) prevent excessive activation of these receptors by continuously removing glutamate from the extracellular fluid in the brain. Further, the blood-brain barrier shields the brain from glutamate in the blood. The highest concentrations of glutamate are found in synaptic vesicles in nerve terminals from where it can be released by exocytosis. In fact, glutamate is the major excitatory neurotransmitter in the mammalian central nervous system. It took, however, a long time to realize that. The present review provides a brief historical description, gives a short overview of glutamate as a transmitter in the healthy brain, and comments on the so-called glutamate-glutamine cycle. The glutamate transporters responsible for the glutamate removal are described in some detail.
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Affiliation(s)
- Y. Zhou
- The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Blindern, P.O. Box 1105, 0317 Oslo, Norway
| | - N. C. Danbolt
- The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Blindern, P.O. Box 1105, 0317 Oslo, Norway
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160
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Transcriptional regulation of the sodium-coupled neutral amino acid transporter (SNAT2) by 17β-estradiol. Proc Natl Acad Sci U S A 2014; 111:11443-8. [PMID: 25056967 DOI: 10.1073/pnas.1412099111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The sodium-coupled neutral amino acid transporter 2 (SNAT2) translocates small neutral amino acids into the mammary gland to promote cell proliferation during gestation. It is known that SNAT2 expression increases during pregnancy, and in vitro studies indicate that this transporter is induced by 17β-estradiol. In this study, we elucidated the mechanism by which 17β-estradiol regulates the transcription of SNAT2. In silico analysis revealed the presence of a potential estrogen response element (ERE) in the SNAT2 promoter. Reporter assays showed an increase in SNAT2 promoter activity when cotransfected with estrogen receptor alpha (ER-α) after 17β-estradiol stimulation. Deletion of the ERE reduced estradiol-induced promoter activity by 63%. Additionally, EMSAs and supershift assays showed that ER-α binds to the SNAT2 ERE and that this binding competes with the interaction of ER-α with its consensus ERE. An in vivo ChIP assay demonstrated that the binding of ER-α to the SNAT2 promoter gradually increased in the mammary gland during gestation and that maximal binding occurred at the highest 17β-estradiol serum concentration. Liquid chromatography-elevated energy mass spectrometry and Western blot analysis revealed that the SNAT2 ER-α-ERE complex contained poly(ADP-ribose) polymerase 1, Lupus Ku autoantigen protein p70, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) proteins and that the silencing of each of these proteins nearly abolished 17β-estradiol-stimulated SNAT2 promoter activity. Nuclear levels of GAPDH increased progressively during gestation in the mammary gland, and GAPDH binding was nucleotide-specific for the SNAT2 ERE. Thus, this study provides new insights into how the mammary epithelium adapts to control amino acid uptake through the transcriptional regulation of the SNAT2 transporter via 17β-estradiol.
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161
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Grifoni D, Bellosta P. Drosophila Myc: A master regulator of cellular performance. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:570-81. [PMID: 25010747 DOI: 10.1016/j.bbagrm.2014.06.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2014] [Revised: 06/26/2014] [Accepted: 06/30/2014] [Indexed: 11/25/2022]
Abstract
The identification of the Drosophila homolog of the human MYC oncogene has fostered a series of studies aimed to address its functions in development and cancer biology. Due to its essential roles in many fundamental biological processes it is hard to imagine a molecular mechanism in which MYC function is not required. For this reason, the easily manipulated Drosophila system has greatly helped in the dissection of the genetic and molecular pathways that regulate and are regulated by MYC function. In this review, we focus on studies of MYC in the fruitfly with particular emphasis on metabolism and cell competition, highlighting the contributions of this model system in the last decade to our understanding of MYC's complex biological nature. This article is part of a Special Issue entitled: Myc proteins in cell biology and pathology.
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Affiliation(s)
- Daniela Grifoni
- Department of "Farmacia e Biotecnologie", University of Bologna, Via Selmi 3, 40126 Bologna, Italy.
| | - Paola Bellosta
- Department of "Bioscienze", University of Milan, Via Celoria 26, 20133 Milan, Italy.
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162
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Arriola Apelo S, Knapp J, Hanigan M. Invited review: Current representation and future trends of predicting amino acid utilization in the lactating dairy cow. J Dairy Sci 2014; 97:4000-17. [DOI: 10.3168/jds.2013-7392] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 03/06/2014] [Indexed: 12/20/2022]
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163
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Berndt N, Holzhütter HG. The high energy demand of neuronal cells caused by passive leak currents is not a waste of energy. Cell Biochem Biophys 2014; 67:527-35. [PMID: 23479331 DOI: 10.1007/s12013-013-9538-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
It is estimated that maintenance of the resting potential of neurons consumes between 15% (in gray matter) and 44% (in fully myelinated white matter) of the brain's total energy budget [1]. This poses the intriguing question why evolution has not strived to lower the permeability of passive ion channels to cut the high resting-state energy budget of the brain. Based on a conceptual mathematical model of neuronal ion currents and action potential (AP) firing we demonstrate that a neuron endowed with small leak currents and correspondingly low energy consumption by the Na(+)/K(+)-ATPase in the resting state may indeed recapitulate all features of normal AP firing. However, the activation and inactivation of such a "low-energy-cost neuron" turns out to be extremely sensitive to small fluctuation of Na(+) currents associated with Na(+)-dependent secondary-active transport that is indispensable for the metabolic integrity of the cell and neurotransmitter recycling. We provide evidence that sufficiently large leak currents function as important stabilizers of the membrane potential and thus are required to allow robust AP firing. Our simulations suggest that the energy demand of the Na(+)/K(+)-ATPase needed to counterbalance passive leak currents cannot be significantly dropped below observed values.
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Affiliation(s)
- Nikolaus Berndt
- Computational Biochemistry Group, Institute of Biochemistry, University Medicine Berlin (Charité), Charitéplatz 1/Sitz: Virchowweg 6, 10117, Berlin, Germany,
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164
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The Involvement of L-Type Amino Acid Transporters in Theanine Transport. Biosci Biotechnol Biochem 2014; 76:2230-5. [DOI: 10.1271/bbb.120519] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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165
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Altintas MM, Moriwaki K, Wei C, Möller CC, Flesche J, Li J, Yaddanapudi S, Faridi MH, Gödel M, Huber TB, Preston RA, Jiang JX, Kerjaschki D, Sever S, Reiser J. Reduction of proteinuria through podocyte alkalinization. J Biol Chem 2014; 289:17454-67. [PMID: 24817115 DOI: 10.1074/jbc.m114.568998] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Podocytes are highly differentiated cells and critical elements for the filtration barrier of the kidney. Loss of their foot process (FP) architecture (FP effacement) results in urinary protein loss. Here we show a novel role for the neutral amino acid glutamine in structural and functional regulation of the kidney filtration barrier. Metabolic flux analysis of cultured podocytes using genetic, toxic, and immunologic injury models identified increased glutamine utilization pathways. We show that glutamine uptake is increased in diseased podocytes to couple nutrient support to increased demand during the disease state of FP effacement. This feature can be utilized to transport increased amounts of glutamine into damaged podocytes. The availability of glutamine determines the regulation of podocyte intracellular pH (pHi). Podocyte alkalinization reduces cytosolic cathepsin L protease activity and protects the podocyte cytoskeleton. Podocyte glutamine supplementation reduces proteinuria in LPS-treated mice, whereas acidification increases glomerular injury. In summary, our data provide a metabolic opportunity to combat urinary protein loss through modulation of podocyte amino acid utilization and pHi.
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Affiliation(s)
- Mehmet M Altintas
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Kumiko Moriwaki
- the Department of Medicine, Division of Nephrology and Hypertension, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Changli Wei
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Clemens C Möller
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Jan Flesche
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Jing Li
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Suma Yaddanapudi
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Mohd Hafeez Faridi
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035
| | - Markus Gödel
- the Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany
| | - Tobias B Huber
- the Renal Division, University Hospital Freiburg, 79106 Freiburg, Germany, the BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs University, 79106 Freiburg, Germany
| | - Richard A Preston
- the Department of Medicine, Division of Clinical Pharmacology, University of Miami Miller School of Medicine, Miami, Florida 33136
| | - Jean X Jiang
- the Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229, and
| | - Dontscho Kerjaschki
- the Clinical Institute of Pathology, Medical University of Vienna, 1090 Vienna, Austria
| | - Sanja Sever
- the Division of Nephrology and Program in Glomerular Disease, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02129
| | - Jochen Reiser
- From the Department of Medicine, Rush University Medical Center, Chicago, Illinois 60035,
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Nishimura T, Yagi R, Usuda M, Oda K, Yamazaki M, Suda S, Takahashi Y, Okazaki F, Sai Y, Higuchi K, Maruyama T, Tomi M, Nakashima E. System A amino acid transporter SNAT2 shows subtype-specific affinity for betaine and hyperosmotic inducibility in placental trophoblasts. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1306-12. [DOI: 10.1016/j.bbamem.2014.01.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2013] [Revised: 12/17/2013] [Accepted: 01/06/2014] [Indexed: 11/27/2022]
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167
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Glycine modulates membrane potential, cell volume, and phagocytosis in murine microglia. Amino Acids 2014; 46:1907-17. [PMID: 24760586 DOI: 10.1007/s00726-014-1745-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 04/05/2014] [Indexed: 12/19/2022]
Abstract
Phagocytes form engulfment pseudopodia at the contact area with their target particle by a process resembling cell volume (CV) regulatory mechanisms. We evaluated whether the osmoregulatory active neutral amino acid glycine, which contributes to CV regulation via activation of sodium-dependent neutral amino acid transporters (SNATs) improves phagocytosis in isotonic and hypertonic conditions in the murine microglial cell line BV-2 and primary microglial cells (pMG). In BV-2 cells and pMG, RT-PCR analysis revealed expression of SNATs (Slc38a1, Slc38a2), but not of GlyRs (Glra1-4). In BV-2 cells, glycine (5 mM) led to a rapid Na(+)-dependent depolarization of membrane potential (V mem). Furthermore, glycine increased CV by about 9%. Visualizing of phagocytosis of polystyrene microspheres by scanning electron microscopy revealed that glycine (1 mM) increased the number of BV-2 cells containing at least one microsphere by about 13%. Glycine-dependent increase in phagocytosis was suppressed by the SNAT inhibitor α-(methylamino)isobutyric acid (MeAIB), by replacing extracellular Na(+) with choline, and under hypertonic conditions, but not by the GlyR antagonist strychnine or the GlyR agonist taurine. Interestingly, hypertonicity-induced suppression of phagocytosis was rescued by glycine. These findings demonstrate that glycine increases phagocytosis in iso- and hypertonic conditions by activation of SNATs.
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168
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New genetic biomarkers predicting azathioprine blood concentrations in combination therapy with 5-aminosalicylic acid. PLoS One 2014; 9:e95080. [PMID: 24762746 PMCID: PMC3999094 DOI: 10.1371/journal.pone.0095080] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 03/23/2014] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND AND AIMS Azathioprine (AZA) is widely used for the treatment of inflammatory bowel disease (IBD) patients. AZA is catabolized by thiopurine S-methyltransferase (TPMT), which exhibits genetic polymorphisms. It has also been reported that 5-aminosalicylic acid (5-ASA) inhibits TPMT activity, and that increased 6-thioguanine nucleotide (6-TGN, a metabolite of AZA) blood concentrations result in an increased number of ADRs. In this study, single nucleotide polymorphisms (SNPs) related to differential gene expression affecting AZA drug metabolism in combination therapy with 5-ASA were examined. METHODS To identify genetic biomarkers for the prediction of 6-TGN blood concentration, ExpressGenotyping analysis was used. ExpressGenotyping analysis is able to detect critical pharmacogenetic SNPs by analyzing drug-induced expression allelic imbalance (EAI) of premature RNA in HapMap lymphocytes. We collected blood samples on 38 patients with inflammatory bowel disease treated with AZA and corroboration of the obtained SNPs was attempted in clinical samples. RESULTS A large number of SNPs with AZA/5-ASA-induced EAI within the investigated HapMap lymphocytes was identified by ExpressGenotyping analysis. The respective SNPs were analyzed in IBD patients' blood samples. Among these SNPs, several that have not yet been described to be induced by AZA/5-ASA were found. SNPs within SLC38A9 showed a particular correlation with patients' 6-TGN blood concentrations. CONCLUSIONS Based on these results, ExpressGenotyping analysis and genotyping of patients appears to be a useful way to identify inter-individual differences in drug responses and ADRs to AZA/5-ASA. This study provides helpful information on genetic biomarkers for optimized AZA/5-ASA treatment of IBD patients.
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169
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Bagchi S, Baomar HA, Al-Walai S, Al-Sadi S, Fredriksson R. Histological analysis of SLC38A6 (SNAT6) expression in mouse brain shows selective expression in excitatory neurons with high expression in the synapses. PLoS One 2014; 9:e95438. [PMID: 24752331 PMCID: PMC3994050 DOI: 10.1371/journal.pone.0095438] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2013] [Accepted: 03/27/2014] [Indexed: 11/18/2022] Open
Abstract
SLC38A6 is one of the newly found members of the solute carrier 38 family consisting of total 11 members, of which only 6 have been characterized so far. Being the only glutamine transporter family expressed in the brain, this family of proteins are most probably involved in the regulation of the glutamate-glutamine cycle, responsible for preventing excitotoxicity. We used immunohistochemistry to show that SLC38A6 is primarily expressed in excitatory neurons and is not expressed in the astrocytes. Using proximity ligation assay, we have quantified the interactions of this SLC38 family protein with other proteins with known localization in the cells, showing that this transporter is expressed at the synapses. Moreover, this study has enabled us to come up with a model suggesting sub-cellular localization of SLC38A6 at the synaptic membrane of the excitatory neurons.
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Affiliation(s)
- Sonchita Bagchi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Hajar Ali Baomar
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Somar Al-Walai
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Saifaddin Al-Sadi
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
- * E-mail:
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170
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Corbett HE, Dubé CD, Slow S, Lever M, Trasler JM, Baltz JM. Uptake of Betaine into Mouse Cumulus-Oocyte Complexes via the SLC7A6 Isoform of y+L Transporter1. Biol Reprod 2014; 90:81. [DOI: 10.1095/biolreprod.113.116939] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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171
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Abstract
The observation that antagonists of the N-methyl-D-aspartate receptor (NMDAR), such as phencyclidine (PCP) and ketamine, transiently induce symptoms of acute schizophrenia had led to a paradigm shift from dopaminergic to glutamatergic dysfunction in pharmacological models of schizophrenia. The glutamate hypothesis can explain negative and cognitive symptoms of schizophrenia better than the dopamine hypothesis, and has the potential to explain dopamine dysfunction itself. The pharmacological and psychomimetic effects of ketamine, which is safer for human subjects than phencyclidine, are herein reviewed. Ketamine binds to a variety of receptors, but principally acts at the NMDAR, and convergent genetic and molecular evidence point to NMDAR hypofunction in schizophrenia. Furthermore, NMDAR hypofunction can explain connectional and oscillatory abnormalities in schizophrenia in terms of both weakened excitation of inhibitory γ-aminobutyric acidergic (GABAergic) interneurons that synchronize cortical networks and disinhibition of principal cells. Individuals with prenatal NMDAR aberrations might experience the onset of schizophrenia towards the completion of synaptic pruning in adolescence, when network connectivity drops below a critical value. We conclude that ketamine challenge is useful for studying the positive, negative, and cognitive symptoms, dopaminergic and GABAergic dysfunction, age of onset, functional dysconnectivity, and abnormal cortical oscillations observed in acute schizophrenia.
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Affiliation(s)
- Joel Frohlich
- Neuroscience Research Program, 1506D Gonda Center, University of California, Los Angeles Box 951761, Los Angeles, CA 90095-1761
| | - John Darrell Van Horn
- The Institute for Neuroimaging and Informatics, Keck School of Medicine, University of Southern California, 2001 North Soto Street – SSB1-102, Los Angeles, CA 90032, Phone: (323) 442-7246
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172
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PAT4 is abundantly expressed in excitatory and inhibitory neurons as well as epithelial cells. Brain Res 2014; 1557:12-25. [PMID: 24530433 DOI: 10.1016/j.brainres.2014.02.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2014] [Accepted: 02/05/2014] [Indexed: 11/23/2022]
Abstract
PAT4, the fourth member of the SLC36/proton dependent amino acid transporter (PAT) family, is a high-affinity, low capacity electroneutral transporter of neutral amino acids like proline and tryptophan. It has also been associated with the function of mTORC1, a complex in the mammalian target of rapamycin (mTOR) pathway. We performed in situ hybridization and immunohistological analysis to determine the expression profile of PAT4, as well as an RT-PCR study on tissue from mice exposed to leucine. We performed a phylogenetic analysis to determine the evolutionary origin of PAT4. The in situ hybridization and the immunohistochemistry on mouse brain sections and hypothalamic cells showed abundant PAT4 expression in the mouse brain intracellularly in both inhibitory and excitatory neurons, partially co-localizing with lysosomal markers and epithelial cells lining the ventricles. Its location in epithelial cells around the ventricles indicates a transport of substrates across the blood brain barrier. Phylogenetic analysis showed that PAT4 belongs to an evolutionary old family most likely predating animals, and PAT4 is the oldest member of that family.
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173
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Glutamatergic candidate genes in autism spectrum disorder: an overview. J Neural Transm (Vienna) 2014; 121:1081-106. [PMID: 24493018 DOI: 10.1007/s00702-014-1161-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 01/13/2014] [Indexed: 12/22/2022]
Abstract
Autism spectrum disorders (ASD) are neurodevelopmental disorders with early onset in childhood. Most of the risk for ASD can be explained by genetic variants that act in interaction with biological environmental risk factors. However, the architecture of the genetic components is still unclear. Genetic studies and subsequent systems biological approaches described converging functional effects of identified genes towards pathways relevant for neuronal signalling. Mouse models suggest an aberrant synaptic plasticity at the neuropathological level, which is believed to be conferred by dysregulation of long-term potentiation or depression of neuronal connections. A central pathway regulating these mechanisms is glutamatergic signalling. Here, we hypothesized that susceptibility genes for ASD are enriched for components of this pathway. To further understand the impact of ASD risk genes on the glutamatergic pathway, we performed a systematic review using the literature database "pubmed" and the "AutismKB" knowledgebase. We provide an overview of the glutamatergic system in typical brain function and development, and summarize findings from linkage, association, copy number variants, and sequencing studies in ASD to provide a comprehensive picture of the glutamatergic landscape of ASD genetics. Genetic variants associated with ASD were enriched in glutamatergic pathways, affecting receptor signalling, metabolism and transport. Furthermore, in genetically modified mouse models for ASD, pharmacological compounds acting on ionotropic or metabotropic receptor activity are able to rescue ASD reminscent phenotypes. We conclude that glutamatergic genetic risk factors for ASD show a complex pattern and further studies are needed to fully understand its mechanisms, before translation of findings into clinical applications and individualized treatment approaches will be possible.
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174
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175
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176
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Kavitha JV, Rosario FJ, Nijland MJ, McDonald TJ, Wu G, Kanai Y, Powell TL, Nathanielsz PW, Jansson T. Down-regulation of placental mTOR, insulin/IGF-I signaling, and nutrient transporters in response to maternal nutrient restriction in the baboon. FASEB J 2013; 28:1294-305. [PMID: 24334703 DOI: 10.1096/fj.13-242271] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The mechanisms by which maternal nutrient restriction (MNR) causes reduced fetal growth are poorly understood. We hypothesized that MNR inhibits placental mechanistic target of rapamycin (mTOR) and insulin/IGF-I signaling, down-regulates placental nutrient transporters, and decreases fetal amino acid levels. Pregnant baboons were fed control (ad libitum, n=11) or an MNR diet (70% of controls, n=11) from gestational day (GD) 30. Placenta and umbilical blood were collected at GD 165. Western blot was used to determine the phosphorylation of proteins in the mTOR, insulin/IGF-I, ERK1/2, and GSK-3 signaling pathways in placental homogenates and expression of glucose transporter 1 (GLUT-1), taurine transporter (TAUT), sodium-dependent neutral amino acid transporter (SNAT), and large neutral amino acid transporter (LAT) isoforms in syncytiotrophoblast microvillous membranes (MVMs). MNR reduced fetal weights by 13%, lowered fetal plasma concentrations of essential amino acids, and decreased the phosphorylation of placental S6K, S6 ribosomal protein, 4E-BP1, IRS-1, Akt, ERK-1/2, and GSK-3. MVM protein expression of GLUT-1, TAUT, SNAT-2 and LAT-1/2 was reduced in MNR. This is the first study in primates exploring placental responses to maternal undernutrition. Inhibition of placental mTOR and insulin/IGF-I signaling resulting in down-regulation of placental nutrient transporters may link maternal undernutrition to restricted fetal growth.
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Affiliation(s)
- Jovita V Kavitha
- 2Center for Pregnancy and Newborn Research, Department of Obstetrics and Gynecology, University of Texas Health Science Center San Antonio, Mail Code 7836, 7703 Floyd Curl Dr., San Antonio, TX 78229-3900, USA.
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177
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Poulter J, Al-Araimi M, Conte I, van Genderen M, Sheridan E, Carr I, Parry D, Shires M, Carrella S, Bradbury J, Khan K, Lakeman P, Sergouniotis P, Webster A, Moore A, Pal B, Mohamed M, Venkataramana A, Ramprasad V, Shetty R, Saktivel M, Kumaramanickavel G, Tan A, Mackey D, Hewitt A, Banfi S, Ali M, Inglehearn C, Toomes C. Recessive mutations in SLC38A8 cause foveal hypoplasia and optic nerve misrouting without albinism. Am J Hum Genet 2013; 93:1143-50. [PMID: 24290379 PMCID: PMC3853409 DOI: 10.1016/j.ajhg.2013.11.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/05/2013] [Accepted: 11/01/2013] [Indexed: 10/26/2022] Open
Abstract
Foveal hypoplasia and optic nerve misrouting are developmental defects of the visual pathway and only co-occur in connection with albinism; to date, they have only been associated with defects in the melanin-biosynthesis pathway. Here, we report that these defects can occur independently of albinism in people with recessive mutations in the putative glutamine transporter gene SLC38A8. Nine different mutations were identified in seven Asian and European families. Using morpholino-mediated ablation of Slc38a8 in medaka fish, we confirmed that pigmentation is unaffected by loss of SLC38A8. Furthermore, by undertaking an association study with SNPs at the SLC38A8 locus, we showed that common variants within this gene modestly affect foveal thickness in the general population. This study reveals a melanin-independent component underpinning the development of the visual pathway that requires a functional role for SLC38A8.
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Affiliation(s)
- James A. Poulter
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Musallam Al-Araimi
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Ivan Conte
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
| | | | - Eamonn Sheridan
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
- Department of Clinical Genetics, St. James’s University Hospital, Leeds, West Yorkshire LS9 7TF, UK
| | - Ian M. Carr
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - David A. Parry
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Mike Shires
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Sabrina Carrella
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
| | - John Bradbury
- Department of Ophthalmology, Bradford Royal Infirmary, Bradford, West Yorkshire BD9 6RJ, UK
| | - Kamron Khan
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Phillis Lakeman
- Department of Clinical Genetics, VU University Medical Center, Amsterdam NL-1081 HV, the Netherlands
| | - Panagiotis I. Sergouniotis
- Division of Inherited Eye Disease, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | - Andrew R. Webster
- Division of Inherited Eye Disease, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | - Anthony T. Moore
- Division of Inherited Eye Disease, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
- Moorfields Eye Hospital, London EC1V 2PD, UK
| | | | - Moin D. Mohamed
- Department of Ophthalmology, St. Thomas’ Hospital, London SE1 9RT, UK
| | | | | | - Rohit Shetty
- Department of Ocular Genetics, Narayana Nethralaya, Bangalore, Karnataka 560099, India
| | | | | | - Alex Tan
- Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, Perth WA 6009, Australia
| | - David A. Mackey
- Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, Perth WA 6009, Australia
| | - Alex W. Hewitt
- Centre for Ophthalmology and Visual Science, University of Western Australia, Crawley, Perth WA 6009, Australia
| | - Sandro Banfi
- Telethon Institute of Genetics and Medicine, Naples 80131, Italy
- Medical Genetics, Department of Biochemistry, Biophysics, and General Pathology, Second University of Naples, Naples 80138, Italy
| | - Manir Ali
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Chris F. Inglehearn
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
| | - Carmel Toomes
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, West Yorkshire LS9 7TF, UK
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178
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Zhou Y, Waanders LF, Holmseth S, Guo C, Berger UV, Li Y, Lehre AC, Lehre KP, Danbolt NC. Proteome analysis and conditional deletion of the EAAT2 glutamate transporter provide evidence against a role of EAAT2 in pancreatic insulin secretion in mice. J Biol Chem 2013; 289:1329-44. [PMID: 24280215 DOI: 10.1074/jbc.m113.529065] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Islet function is incompletely understood in part because key steps in glutamate handling remain undetermined. The glutamate (excitatory amino acid) transporter 2 (EAAT2; Slc1a2) has been hypothesized to (a) provide islet cells with glutamate, (b) protect islet cells against high extracellular glutamate concentrations, (c) mediate glutamate release, or (d) control the pH inside insulin secretory granules. Here we floxed the EAAT2 gene to produce the first conditional EAAT2 knock-out mice. Crossing with Nestin-cyclization recombinase (Cre) eliminated EAAT2 from the brain, resulting in epilepsy and premature death, confirming the importance of EAAT2 for brain function and validating the genetic construction. Crossing with insulin-Cre lines (RIP-Cre and IPF1-Cre) to obtain pancreas-selective deletion did not appear to affect survival, growth, glucose tolerance, or β-cell number. We found (using TaqMan RT-PCR, immunoblotting, immunocytochemistry, and proteome analysis) that the EAAT2 levels were too low to support any of the four hypothesized functions. The proteome analysis detected more than 7,000 islet proteins of which more than 100 were transporters. Although mitochondrial glutamate transporters and transporters for neutral amino acids were present at high levels, all other transporters with known ability to transport glutamate were strikingly absent. Glutamate-metabolizing enzymes were abundant. The level of glutamine synthetase was 2 orders of magnitude higher than that of glutaminase. Taken together this suggests that the uptake of glutamate by islets from the extracellular fluid is insignificant and that glutamate is intracellularly produced. Glutamine synthetase may be more important for islets than assumed previously.
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Affiliation(s)
- Yun Zhou
- From The Neurotransporter Group, Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, 0317 Oslo, Norway
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179
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Bjørnsen LP, Hadera MG, Zhou Y, Danbolt NC, Sonnewald U. The GLT-1 (EAAT2; slc1a2) glutamate transporter is essential for glutamate homeostasis in the neocortex of the mouse. J Neurochem 2013; 128:641-9. [PMID: 24224925 DOI: 10.1111/jnc.12509] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 10/18/2013] [Accepted: 10/21/2013] [Indexed: 12/24/2022]
Abstract
Glutamate is the major excitatory neurotransmitter, and is inactivated by cellular uptake catalyzed mostly by the glutamate transporter subtypes GLT-1 (EAAT2) and GLAST (EAAT1). Astrocytes express both GLT-1 and GLAST, while axon terminals in the neocortex only express GLT-1. To evaluate the role of GLT-1 in glutamate homeostasis, we injected GLT-1 knockout (KO) mice and wild-type littermates with [1-(13)C]glucose and [1,2-(13)C]acetate 15 min before euthanization. Metabolite levels were analyzed in extracts from neocortex and cerebellum and (13)C labeling in neocortex. Whereas the cerebellum in GLT-1-deficient mice had normal levels of glutamate, glutamine, and (13)C labeling of metabolites, glutamate level was decreased but labeling from [1-(13)C] glucose was unchanged in the neocortex. The contribution from pyruvate carboxylation toward labeling of these metabolites was unchanged. Labeling from [1,2-(13)C] acetate, originating in astrocytes, was decreased in glutamate and glutamine in the neocortex indicating reduced mitochondrial metabolism in astrocytes. The decreased amount of glutamate in the cortex indicates that glutamine transport into neurons is not sufficient to replenish glutamate lost because of neurotransmission and that GLT-1 plays a role in glutamate homeostasis in the cortex. Glutamate is the major excitatory neurotransmitter, and is inactivated by uptake via GLT-1 (EAAT2) and GLAST (EAAT1) transporters, while axon terminals in the neocortex only express GLT-1. To evaluate the role of GLT-1 in glutamate homeostasis, we used [1-(13)C]glucose and [1,2-(13)C]acetate injection and NMR spectroscopy. The results indicate that glutamine transport into neurons is not sufficient to replenish glutamate lost because of neurotransmission and that GLT-1 plays a role in glutamate homeostasis in the neocortex.
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Affiliation(s)
- Lars Petter Bjørnsen
- Department of Anatomy, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
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180
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The SLC38 family of sodium-amino acid co-transporters. Pflugers Arch 2013; 466:155-72. [PMID: 24193407 DOI: 10.1007/s00424-013-1393-y] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/16/2013] [Accepted: 10/20/2013] [Indexed: 12/13/2022]
Abstract
Transporters of the SLC38 family are found in all cell types of the body. They mediate Na(+)-dependent net uptake and efflux of small neutral amino acids. As a result they are particularly expressed in cells that grow actively, or in cells that carry out significant amino acid metabolism, such as liver, kidney and brain. SLC38 transporters occur in membranes that face intercellular space or blood vessels, but do not occur in the apical membrane of absorptive epithelia. In the placenta, they play a significant role in the transfer of amino acids to the foetus. Members of the SLC38 family are highly regulated in response to amino acid depletion, hypertonicity and hormonal stimuli. SLC38 transporters play an important role in amino acid signalling and have been proposed to act as transceptors independent of their transport function. The structure of SLC38 transporters is characterised by the 5 + 5 inverted repeat fold, which is observed in a wide variety of transport proteins.
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181
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Gårdebjer EM, Cuffe JSM, Pantaleon M, Wlodek ME, Moritz KM. Periconceptional alcohol consumption causes fetal growth restriction and increases glycogen accumulation in the late gestation rat placenta. Placenta 2013; 35:50-7. [PMID: 24239160 DOI: 10.1016/j.placenta.2013.10.008] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 10/18/2013] [Accepted: 10/18/2013] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Alcohol consumption is a common social practice among women of childbearing age. With 50% of pregnancies being unplanned, many embryos are exposed to alcohol prior to pregnancy recognition and formation of the placenta. The effects of periconceptional (PC) alcohol exposure on the placenta are unknown. METHODS Sprague-Dawley rats were exposed to alcohol (12.5% v/v ad libitum) from 4 days prior to 4 days after conception and effects on placental growth, morphology and gene/protein expression examined at embryonic day (E) 20. RESULTS PC ethanol (EtOH)-exposed fetuses were growth restricted and their placental/body weight ratio and placental cross-sectional area were increased. This was associated with an increase in cross-sectional area of the junctional zone and glycogen cells, especially in PC EtOH-exposed placentas from female fetuses. Junctional Glut1 and Igf2 mRNA levels were increased. Labyrinth Igf1 mRNA levels were decreased in placentas from both sexes, but protein IGF1R levels were decreased in placentas from male fetuses only. Labyrinth mRNA levels of Slc38a2 were decreased and Vegfa were increased in placentas following PC EtOH-exposure but only placentas from female fetuses exhibited increased Kdr expression. Augmented expression of the protective enzyme 11βHsd2 was found in PC EtOH-exposed labyrinth. DISCUSSION These observations are consistent with a stress response, apparent well beyond the period of EtOH-exposure and demonstrate that PC EtOH alters placental development in a sex specific manner. CONCLUSION Public awareness should be increased to educate women about how excessive drinking even before falling pregnant may impact on placental development and fetal health.
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Affiliation(s)
- E M Gårdebjer
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - J S M Cuffe
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - M Pantaleon
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - M E Wlodek
- The Department of Physiology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - K M Moritz
- School of Biomedical Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia.
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182
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Kondou H, Kawai M, Tachikawa K, Kimoto A, Yamagata M, Koinuma T, Yamazaki M, Nakayama M, Mushiake S, Ozono K, Michigami T. Sodium-coupled neutral amino acid transporter 4 functions as a regulator of protein synthesis during liver development. Hepatol Res 2013; 43:1211-23. [PMID: 23607685 DOI: 10.1111/hepr.12069] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2012] [Revised: 12/17/2012] [Accepted: 01/03/2013] [Indexed: 12/13/2022]
Abstract
AIM The molecular mechanisms by which hepatocyte nuclear factor (HNF)4α regulates fetal liver development have not been fully elucidated. We screened the downstream molecules of HNF4α during liver development and identified sodium-coupled neutral amino acid transporter (SNAT)4. The aim of this study is to investigate the regulation of SNAT4 by HNF4α and to clarify its roles in differentiating hepatocytes. METHODS HNF4α was overexpressed in cultured liver buds using adenovirus, and suppression subtractive hybridization screening was performed. Temporal and spatial expression of SNAT4 during liver development was investigated. Regulation of SNAT4 by HNF4α was examined by promoter analyses and electrophoretic mobility shift assays (EMSA). Metabolic labeling and western blotting were carried out using primary hepatoblasts with SNAT4 overexpression. RESULTS The expression of Slc38a4 encoding SNAT4 showed a marked perinatal increase, and was predominant among system A amino acid transporters. It was first detected in embryonic day 18.5 liver, and found in most hepatocytes after birth. Three alternative first exons were found in the SNAT4 gene. Promoter analyses using approximately 3-kb fragments corresponding to each first exon (AP1, AP2, AP3) revealed that AP1 and AP2 exhibited strong promoter activity in mouse hepatoblasts with endogenous HNF4α. Transactivation of AP2 was upregulated by HNF4α in HeLa cells without endogenous HNF4α. EMSA has demonstrated that HNF4α directly binds to cis-elements in AP2. Overexpression of SNAT4 facilitated amino acid uptake and de novo protein synthesis in primary hepatoblasts. CONCLUSION SNAT4 functions downstream of HNF4α and plays significant roles in liver development through mechanisms of amino acid uptake and protein synthesis.
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Affiliation(s)
- Hiroki Kondou
- Department of Environmental Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health, Osaka, Japan; Department of Pediatrics, Osaka University Graduate School of Medicine, Osaka, Japan
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183
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Partitioning of glutamine synthesised by the isolated perfused human placenta between the maternal and fetal circulations. Placenta 2013; 34:1223-31. [PMID: 24183194 PMCID: PMC3851744 DOI: 10.1016/j.placenta.2013.10.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 09/03/2013] [Accepted: 10/07/2013] [Indexed: 01/01/2023]
Abstract
INTRODUCTION Placental glutamine synthesis has been demonstrated in animals and is thought to increase the availability of this metabolically important amino acid to the fetus. Glutamine is of fundamental importance for cellular replication, cellular function and inter-organ nitrogen transfer. The objective of this study was to investigate the role of glutamate/glutamine metabolism by the isolated perfused human placenta in the provision of glutamine to the fetus. METHODS Glutamate metabolism was investigated in the isolated dually perfused human placental cotyledon. U-¹³C-glutamate was used to investigate the movement of carbon and ¹⁵N-leucine to study movement of amino-nitrogen. Labelled amino acids were perfused via maternal or fetal arteries at defined flow rates. The enrichment and concentration of amino acids in the maternal and fetal veins were measured following 5 h of perfusion. RESULTS Glutamate taken up from the maternal and fetal circulations was primarily converted into glutamine the majority of which was released into the maternal circulation. The glutamine transporter SNAT5 was localised to the maternal-facing membrane of the syncytiotrophoblast. Enrichment of ¹³C or ¹⁵N glutamine in placental tissue was lower than in either the maternal or fetal circulation, suggesting metabolic compartmentalisation within the syncytiotrophoblast. DISCUSSION Placental glutamine synthesis may help ensure the placenta's ability to supply this amino acid to the fetus does not become limiting to fetal growth. Glutamine synthesis may also influence placental transport of other amino acids, metabolism, nitrogen flux and cellular regulation. CONCLUSIONS Placental glutamine synthesis may therefore be a central mechanism in ensuring that the human fetus receives adequate nutrition and is able to maintain growth.
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184
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Kyriakopoulos S, Polizzi KM, Kontoravdi C. Comparative analysis of amino acid metabolism and transport in CHO variants with different levels of productivity. J Biotechnol 2013; 168:543-51. [PMID: 24056080 DOI: 10.1016/j.jbiotec.2013.09.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 09/10/2013] [Accepted: 09/12/2013] [Indexed: 12/12/2022]
Abstract
Chinese hamster ovary (CHO) cells are widely used for the production of biopharmaceuticals; however, our understanding of several physiological elements that contribute to productivity is limited. One of these is amino acid transport and how its limitation and/or regulation might affect productivity. To further our understanding, we have examined the expression of 40 mammalian amino acid transporter genes during batch cultures of three CHO cell lines: a non-producer and two antibody-producing cell lines with different levels of productivity. In parallel, extracellular and intracellular levels of amino acids were quantified. The aim was to identify differences in gene regulation between cell lines and within culture. Our results show that three transporters associated with transport of taurine and β-alanine, acidic amino acids and branched chain amino acids, are highly upregulated in both antibody-producing cell lines but not in the non-producer. Additionally, genes associated with the transport of amino acids related to the glutathione pathway (alanine, cysteine, cystine, glycine, glutamate) were found to be highly upregulated during the stationary phase of cell culture, correlating well with literature data on the importance of the pathway. Our analysis highlights potential markers for cell line selection and targets for process optimization.
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Affiliation(s)
- Sarantos Kyriakopoulos
- Centre for Process Systems Engineering, Department of Chemical Engineering, Imperial College London, London SW7 2AZ, UK
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185
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Du QX, Sun JH, Zhang LY, Liang XH, Guo XJ, Gao CR, Wang YY. Time-dependent expression of SNAT2 mRNA in the contused skeletal muscle of rats: a possible marker for wound age estimation. Forensic Sci Med Pathol 2013; 9:528-33. [PMID: 24045877 DOI: 10.1007/s12024-013-9482-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2013] [Indexed: 02/05/2023]
Abstract
To estimate the age of skeletal muscle contusion, the expression of SNAT2 mRNA in contused skeletal muscle of rats was detected by real-time polymerase chain reaction (PCR). In total, 78 Sprague-Dawley male rats were divided into control and contusion groups. At 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, and 48 h (n = 6) after contusion, the rats were sacrificed with a lethal dose of pentobarbital. Another 24 rats received contusion injuries at 6, 12, 18, and 24 h (n = 6) after death. Total RNA was isolated from muscle specimens using the TRIzol reagent and reverse-transcribed into first-strand cDNA. Sequence-specific primers and TaqMan fluorogenic probes for SNAT2 mRNA and RPL13 mRNA were designed using the AlleleID 6 software, and the expression levels of SNAT2 mRNA were determined by real-time PCR. At 4, 16, 20, and 24 h after contusion, expression levels of SNAT2 mRNA normalized to RPL13 mRNA increased by 2.07 (P < 0.05), 2.53 (P < 0.05), 2.68 (P < 0.05), and 2.06 fold (P < 0.05) respectively, versus that in the control group. However, there was no significant change in the expression level of SNAT2 mRNA from 24 to 48 h (P > 0.05) after contusion, when normalized to RPL13 mRNA. There was no change in the expression level of SNAT2 mRNA between the normal skeletal muscle from the left limb of the same injured rat and the control. Also, no degradation of SNAT2 mRNA was detected in the postmortem samples (P > 0.05). This result suggests that the determination of SNAT2 mRNA levels by real-time PCR may be useful for estimating wound age.
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Affiliation(s)
- Qiu-xiang Du
- Department of Forensic Pathology, Shanxi Medical University, 56 South Xinjian Nan Road, Taiyuan, 030001, Shanxi, People's Republic of China
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186
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Isolated foveal hypoplasia with secondary nystagmus and low vision is associated with a homozygous SLC38A8 mutation. Eur J Hum Genet 2013; 22:703-6. [PMID: 24045842 DOI: 10.1038/ejhg.2013.212] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/07/2013] [Accepted: 08/16/2013] [Indexed: 11/08/2022] Open
Abstract
Foveal hypoplasia, always accompanied by nystagmus, is found as part of the clinical spectrum of various eye disorders such as aniridia, albinism and achromatopsia. However, the molecular basis of isolated autosomal recessive foveal hypoplasia is yet unknown. Individuals of apparently unrelated non consanguineous Israeli families of Jewish Indian (Mumbai) ancestry presented with isolated foveal hypoplasia associated with congenital nystagmus and reduced visual acuity. Genome-wide homozygosity mapping followed by fine mapping defined a 830 Kb disease-associated locus (LOD score 3.5). Whole-exome sequencing identified a single missense mutation in the homozygosity region: c.95T>G, p.(Ile32Ser), in a conserved amino acid within the first predicted transmembrane domain of SLC38A8. The mutation fully segregated with the disease-associated phenotype, demonstrating an ∼10% carrier rate in Mumbai Jews. SLC38A8 encodes a putative sodium-dependent amino-acid/proton antiporter, which we showed to be expressed solely in the eye. Thus, a homozygous SLC38A8 mutation likely underlies isolated foveal hypoplasia.
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187
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Fu J, Han J, Zhou B, Gong Z, Santos EM, Huo X, Zheng W, Liu H, Yu H, Liu C. Toxicogenomic responses of zebrafish embryos/larvae to tris(1,3-dichloro-2-propyl) phosphate (TDCPP) reveal possible molecular mechanisms of developmental toxicity. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:10574-82. [PMID: 23919627 DOI: 10.1021/es401265q] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is frequently present in indoor dust and can be detected in human milk. In order to evaluate the effects of TDCPP on vertebrate development, zebrafish embryos/larvae were used as an animal model to examine developmental phenotypes and explore possible mechanisms of toxicity by employing microarrays and iTRAQ labeling quantitative proteomics. The results demonstrated that treatment with TDCPP (3 μM) from 0.75 h postfertilization (hpf) inhibited cell rearrangement at 4 hpf, caused delay in epiboly at 5.7 and 8.5 hpf, and led to abnormal development (e.g., short tail, reduced body size) and lethality between 14 and 45 hpf, which might be related with altered expression of genes regulating embryogenesis. Furthermore, trunk curvature was observed as the main phenotype in 96 hpf zebrafish larvae exposed to 1 or 3 μM TDCPP, possibly by changing somite formation and expression of proteins related to fast muscle and cartilage development. Collectively, our results suggest that exposure to TDCPP causes developmental toxicity in vertebrates and warrant the need for studies to evaluate the potential health risks of TDCPP to developing human embryos/infants/children, due to its frequent presence in indoor dust and potential for human exposure.
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Affiliation(s)
- Jie Fu
- State Key Laboratory of Pollution Control and Resource Reuse & School of the Environment, Nanjing University , Nanjing, Jiangsu 210023, China
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188
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Schiöth HB, Roshanbin S, Hägglund MGA, Fredriksson R. Evolutionary origin of amino acid transporter families SLC32, SLC36 and SLC38 and physiological, pathological and therapeutic aspects. Mol Aspects Med 2013; 34:571-85. [PMID: 23506890 DOI: 10.1016/j.mam.2012.07.012] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Accepted: 06/25/2012] [Indexed: 10/27/2022]
Abstract
About 25% of all solute carriers (SLCs) are likely to transport amino acids as their primary substrate. One of the major phylogenetic clusters of amino acid transporters from the SLC family is the β-family, which is part of the PFAM APC clan. The β-family includes three SLC families, SLC32, SLC36 and SLC38 with one, four and eleven members in humans, respectively. The most well characterized genes within these families are the vesicular inhibitory amino acid transporter (VIAAT, SLC32A1), PAT1 (SLC36A1), PAT2 (SLC36A2), PAT4 (SLC36A4), SNAT1 (SLC38A1), SNAT2 (SLC38A2), SNAT3 (SLC38A3), and SNAT4 (SLC38A4). Here we review the structural characteristics and functional role of these transporters. We also mined the complete protein sequence datasets for nine different genomes to clarify the evolutionary history of the β-family of transporters. We show that all three main branches of the this family are found as far back as green algae suggesting that genes from these families existed in the early eukaryote before the split of animals and plants and that they are present in most animal species. We also address the potential of further drug development within this field highlighting the important role of these transporters in neurotransmission and transport of amino acids as nutrients.
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Affiliation(s)
- Helgi B Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden.
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189
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Ono M, Oka S, Okudaira H, Schuster DM, Goodman MM, Kawai K, Shirakami Y. Comparative evaluation of transport mechanisms of trans-1-amino-3-[¹⁸F]fluorocyclobutanecarboxylic acid and L-[methyl-¹¹C]methionine in human glioma cell lines. Brain Res 2013; 1535:24-37. [PMID: 23994214 DOI: 10.1016/j.brainres.2013.08.037] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 08/08/2013] [Accepted: 08/21/2013] [Indexed: 12/01/2022]
Abstract
Positron emission tomography (PET) with amino acid tracers is useful for the visualization and assessment of therapeutic effects on gliomas. Our purpose is to elucidate the transport mechanisms of trans-1-amino-3-[¹⁸F]fluorocyclobutanecarboxylic acid (anti-[¹⁸F]FACBC) and L-[methyl-¹¹C]methionine ([¹¹C]Met) in normal human astrocytes (NHA), low-grade (Hs683, SW1088), and high-grade (U87MG, T98G) human glioma cell lines. Because the short half-lives of fluorine-18 and carbon-11 are inconvenient for in vitro experiments, trans-1-amino-3-fluoro[1-¹⁴C]cyclobutanecarboxylic acid (anti-[¹⁴C]FACBC) and L-[methyl-¹⁴C]methionine ([¹⁴C]Met) were used instead of the PET tracers. Time-course uptake experiments showed that uptake of anti-[¹⁴C]FACBC was 1.4-2.6 times higher than that of [¹⁴C]Met in NHA and low-grade glioma cells, and was almost equal to that of [¹⁴C]Met in high-grade glioma cells. To identify the amino acid transporters (AATs) involved in the transport of anti-[¹⁴C]FACBC and [¹⁴C]Met, we carried out competitive inhibition experiments using synthetic/naturally-occurring amino acids as inhibitors. We found that anti-[¹⁴C]FACBC uptake in the presence of Na⁺ was strongly inhibited by L-glutamine and L-serine (the substrates for ASC system AATs), whereas L-phenylalanine and 2-amino-bicyclo[2,2,1]heptane-2-carboxylic acid (BCH, the substrates for L system AATs) robustly inhibited Na⁺-independent anti-[¹⁴C]FACBC uptake. Regardless of Na⁺, [¹⁴C]Met uptake was inhibited strongly by L-phenylalanine and BCH. Moreover, the exchange transport activity of L-glutamine for anti-[¹⁴C]FACBC was stronger than that of BCH in the presence of Na⁺, whereas that for [¹⁴C]Met was almost equal to BCH. These results demonstrate that ASC and L are important transport systems for anti-[¹⁸F]FACBC uptake, while system L is predominantly involved in [¹¹C]Met transport in human astrocytes and glioma cells.
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Affiliation(s)
- Masahiro Ono
- Research Center, Nihon Medi-Physics Co., Ltd., Chiba 299-0266, Japan; Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Ishikawa 920-0942, Japan
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190
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Weng CY, Chiou SY, Wang L, Kou MC, Wang YJ, Wu MJ. Arsenic trioxide induces unfolded protein response in vascular endothelial cells. Arch Toxicol 2013; 88:213-26. [PMID: 23892647 DOI: 10.1007/s00204-013-1101-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 07/11/2013] [Indexed: 01/13/2023]
Abstract
Chronic arsenic exposure has been linked to endothelial dysfunction and apoptosis. We investigate the involvement of unfolded protein response (UPR) signaling in the arsenic-mediated cytotoxicity of the SVEC4-10 mouse endothelial cells. The SVEC4-10 cells underwent apoptosis in response to As2O3 dose- and time-dependently, accompanied by increased accumulation of calcium, and activation of caspase-3. These phenomena were completely inhibited by α-lipoic acid (LA), which did not scavenge ROS over-production, but were only partially or not ameliorated by tiron, a potent superoxide scavenger. Moreover, arsenic activated UPR, leading to phosphorylation of eukaryotic translation initiation factor 2 subunit α (eIF2α), induction of ATF4, and processing of ATF6. Treatment with arsenic also triggered the expression of endoplasmic reticulum (ER) stress markers, GRP78 (glucose-regulated protein), and CHOP (C/EBP homologous protein). The activation of eIF2α, ATF4 and ATF6 and expression of GRP78 and CHOP are repressed by both LA and tiron, indicating arsenic-induced UPR is mediated through ROS-dependent and ROS-independent pathways. Arsenic also induced ER stress-inducible genes, BAX, PUMA (p53 upregulated modulator of apoptosis), TRB3 (tribbles-related protein 3), and SNAT2 (sodium-dependent neutral amino acid transporter 2). Consistent with intracellular calcium and cell viability data, ROS may not be important in arsenic-induced death, because tiron did not affect the expression of these pro-apoptotic genes. In addition, pretreatment with salubrinal, a selective inhibitor of eIF2α dephosphorylation, enhanced arsenic-induced GRP78 and CHOP expression and partially prevented arsenic cytotoxicity in SVEC4-10 cells. Taken together, these results suggest that arsenic-induced endothelial cytotoxicity is associated with ER stress, which is mediated by ROS-dependent and ROS-independent signaling.
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Affiliation(s)
- Ching-Yi Weng
- Department of Biotechnology, Chia Nan University of Pharmacy and Science, Tainan, 717, Taiwan
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191
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Wang K, Cao F, Fang W, Hu Y, Chen Y, Ding H, Yu G. Activation of SNAT1/SLC38A1 in human breast cancer: correlation with p-Akt overexpression. BMC Cancer 2013; 13:343. [PMID: 23848995 PMCID: PMC3729721 DOI: 10.1186/1471-2407-13-343] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 05/14/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND SNAT1 is a subtype of the amino acid transport system A that has been implicated to play a potential role in cancer development and progression, yet its role in breast cancer remains unclear. In present study, we detected SNAT1 expression in breast cancers and explored its underlying mechanism in promoting breast carcinogenesis. METHODS RT-PCR and Western blotting were performed to analyze the transcription and protein levels of SNAT1 in breast cancer cell lines and fresh tissues. Tissue microarray blocks containing breast cancer specimens obtained from 210 patients were constructed. Expression of SNAT1 in these specimens was analyzed using immunohistochemical studies. SNAT1 was down-regulated by SNAT1-shRNA in breast cancer cells and the functional significance was measured. RESULTS SNAT1 was up-regulated in breast cancer cell lines and breast cancer tissues. Overexpression of SNAT1 was observed in 127 cases (60.5%). Expression of SNAT1 was significantly associated with tumor size, nodal metastasis, advanced disease stage, Ki-67, and ER status. Suppression of endogenous SNAT1 leads to cell growth inhibition, cell cycle arrest, and apoptosis of 4T1 cells and lowered the phosphorylation level of Akt. SNAT1 expression correlated significantly with p-Akt expression in human breast cancer samples. CONCLUSIONS The cross-talk between Akt signaling and SNAT1 might play a critical role in the development and progression of breast cancer, providing an important molecular basis for novel diagnostic markers and new attractive targets in the treatment of breast cancer patients.
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Affiliation(s)
- Kuo Wang
- Department of Surgery, The Affiliated Kunshan First People's Hospital, Jiangsu University, Kunshan 215300, Jiangsu Province, China
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192
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Rooman I, Lutz C, Pinho AV, Huggel K, Reding T, Lahoutte T, Verrey F, Graf R, Camargo SMR. Amino acid transporters expression in acinar cells is changed during acute pancreatitis. Pancreatology 2013; 13:475-85. [PMID: 24075511 DOI: 10.1016/j.pan.2013.06.006] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 06/15/2013] [Accepted: 06/17/2013] [Indexed: 12/11/2022]
Abstract
Pancreatic acinar cells accumulate amino acids against a marked concentration gradient to synthesize digestive enzymes. Thus, the function of acinar cells depends on amino acid uptake mediated by active transport. Despite the importance of this process, pancreatic amino acid transporter expression and cellular localization is still unclear. We screened mouse pancreas for the expression of genes encoding amino acid transporters. We showed that the most highly expressed transporters, namely sodium dependent SNAT3 (Slc38a3) and SNAT5 (Slc38a5) and sodium independent neutral amino acids transporters LAT1 (Slc7a5) and LAT2 (Slc7a8), are expressed in the basolateral membrane of acinar cells. SNAT3 and SNAT5, LAT1 and LAT2 are expressed in acinar cells. Additional evidence that these transporters are expressed in mature acinar cells was gained using acinar cell culture and acute pancreatitis models. In the acute phase of pancreatic injury, when acinar cell loss occurs, and in an acinar cell culture model, which mimics changes occurring during pancreatitis, SNAT3 and SNAT5 are strongly down-regulated. LAT1 and LAT2 were down-regulated only in the in vitro model. At protein level, SNAT3 and SNAT5 expression was also reduced during pancreatitis. Expression of other amino acid transporters was also modified in both models of pancreatitis. The subset of transporters with differential expression patterns during acute pancreatitis might be involved in the injury/regeneration phases. Further expression, localization and functional studies will follow to better understand changes occurring during acute pancreatitis. These findings provide insight into pancreatic amino acid transport in healthy pancreas and during acute pancreatitis injury.
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Affiliation(s)
- Ilse Rooman
- Cancer Research Program, The Kinghorn Cancer Centre, Garvan Institute of Medical Research, Darlinghurst-Sydney, NSW, Australia; St Vincent's Clinical School, University New South Wales, Australia; Cell Differentiation Unit, Diabetes Research Center, Vrije Universiteit Brussel, Brussels, Belgium
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193
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Pochini L, Scalise M, Galluccio M, Indiveri C. OCTN cation transporters in health and disease: role as drug targets and assay development. ACTA ACUST UNITED AC 2013; 18:851-67. [PMID: 23771822 DOI: 10.1177/1087057113493006] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The three members of the organic cation transporter novel subfamily are known to be involved in interactions with xenobiotic compounds. These proteins are characterized by 12 transmembrane segments connected by nine short loops and two large hydrophilic loops. It has been recently pointed out that acetylcholine is a physiological substrate of OCTN1. Its transport could be involved in nonneuronal cholinergic functions. OCTN2 maintains the carnitine homeostasis, resulting from intestinal absorption, distribution to tissues, and renal excretion/reabsorption. OCTN3, identified only in mouse, mediates also carnitine transport. OCTN1 and OCTN2 are associated with several pathologies, such as inflammatory bowel disease, primary carnitine deficiency, diabetes, neurological disorders, and cancer, thus representing useful pharmacological targets. The function and interaction with drugs of OCTNs have been studied in intact cell systems and in proteoliposomes. The latter experimental model enables reduced interference from other transporters or enzyme pathways. Using proteoliposomes, the molecular bases of toxicity of some drugs have recently been revealed. Therefore, proteoliposomes represent a promising experimental tool suitable for large-scale molecular screening of interactions of OCTNs with chemicals regarding human health.
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Affiliation(s)
- Lorena Pochini
- Laboratory of Biochemistry and Molecular Biotechnology, Department BEST (Biologia, Ecologia, Scienze della Terra), University of Calabria, Italy
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194
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Schweikhard ES, Ziegler CM. Amino acid secondary transporters: toward a common transport mechanism. CURRENT TOPICS IN MEMBRANES 2013. [PMID: 23177982 DOI: 10.1016/b978-0-12-394316-3.00001-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Solute carriers (SLC) that transport amino acids are key players in health and diseases in humans. Their prokaryotic relatives are often involved in essential physiological processes in microorganisms, e.g. in homeostasis and acidic/osmotic stress response. High-resolution X-ray structures of the sequence-unrelated amino acid transporters unraveled a striking structural similarity between carriers, which were formerly assigned to different families. The highly conserved fold is characterized by two inverted structural repeats of five transmembrane helices each and indicates common mechanistic transport concepts if not an evolutionary link among a large number of amino acid transporters. Therefore, these transporters are classified now into the structural amino acid-polyamine-organocation superfamily (APCS). The APCS includes among others the mammalian SLC6 transporters and the heterodimeric SLC7/SLC3 transporters. However, it has to be noted that the APCS is not limited entirely to amino acid transporters but contains also transporters for, e.g. amino acid derivatives and sugars. For instance, the betaine-choline-carnitine transporter family of bacterial activity-regulated Na(+)- and H(+)-coupled symporters for glycine betaine and choline is also part of this second largest structural superfamily. The APCS fold provides different possibilities to transport the same amino acid. Arginine can be transported by an H(+)-coupled symport or by antiport mechanism in exchange against agmatine for example. The convergence of the mechanistic concept of transport under comparable physiological conditions allows speculating if structurally unexplored amino acid transporters, e.g. the members of the SLC36 and SLC38 family, belong to the APCS, too. In the kidney, which is an organ that depends critically on the regulated amino acid transport, these different SLC transporters have to work together to account for proper function. Here, we will summarize the basic concepts of Na(+)- and H(+)-coupled amino acid symport and amino acid-product antiport in the light of the respective physiological requirements.
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Affiliation(s)
- Eva S Schweikhard
- Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Germany
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195
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Parisi F, Riccardo S, Zola S, Lora C, Grifoni D, Brown LM, Bellosta P. dMyc expression in the fat body affects DILP2 release and increases the expression of the fat desaturase Desat1 resulting in organismal growth. Dev Biol 2013; 379:64-75. [PMID: 23608455 DOI: 10.1016/j.ydbio.2013.04.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 04/05/2013] [Accepted: 04/10/2013] [Indexed: 01/12/2023]
Abstract
Drosophila dMyc (dMyc) is known for its role in cell-autonomous regulation of growth. Here we address its role in the fat body (FB), a metabolic tissue that functions as a sensor of circulating nutrients to control the release of Drosophila Insulin-like peptides (Dilps) from the brain influencing growth and development. Our results show that expression of dMyc in the FB affects development and animal size. Expression of dMyc, but not of CycD/cdk4 or Rheb, in the FB diminishes the ability to retain Drosophila Insulin-like peptide-2 (DILP2) in the brain during starvation, suggesting that expression of dMyc mimics the signal that remotely controls the release of Dilps into the hemolymph. dMyc also affects glucose metabolism and increases the transcription of Glucose-transporter-1 mRNA, and of Hexokinase and Pyruvate-Kinase mRNAs, key regulators of glycolysis. These animals are able to counteract the increased levels of circulating trehalose induced by a high sugar diet leading to the conclusion that dMyc activity in the FB promotes glucose disposal. dMyc expression induces cell autonomous accumulation of triglycerides, which correlates with increased levels of Fatty Acid Synthase and Acetyl CoA Carboxylase mRNAs, enzymes responsible for lipid synthesis. We also found the expression of Stearoyl-CoA desaturase, Desat1 mRNA significantly higher in FB overexpressing dMyc. Desat1 is an enzyme that is necessary for monosaturation and production of fatty acids, and its reduction affects dMyc's ability to induce fat storage and resistance to animal survival. In conclusion, here we present novel evidences for dMyc function in the Drosophila FB in controlling systemic growth. We discovered that dMyc expression triggers cell autonomous mechanisms that control glucose and lipid metabolism to favor the storage of nutrients (lipids and sugars). In addition, the regulation of Desat1 controls the synthesis of triglycerides in FB and this may affect the humoral signal that controls DILP2 release in the brain.
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Affiliation(s)
- Federica Parisi
- Department of Biology, City College of the City University of New York, New York, NY 10031, USA
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196
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Combined walking exercise and alkali therapy in patients with CKD4-5 regulates intramuscular free amino acid pools and ubiquitin E3 ligase expression. Eur J Appl Physiol 2013; 113:2111-24. [PMID: 23591985 DOI: 10.1007/s00421-013-2628-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Accepted: 03/13/2013] [Indexed: 01/04/2023]
Abstract
Muscle-wasting in chronic kidney disease (CKD) arises from several factors including sedentary behaviour and metabolic acidosis. Exercise is potentially beneficial but might worsen acidosis through exercise-induced lactic acidosis. We studied the chronic effects of exercise in CKD stage 4-5 patients (brisk walking, 30 min, 5 times/week), and non-exercising controls; each group receiving standard oral bicarbonate (STD), or additional bicarbonate (XS) (Total n = 26; Exercising + STD n = 9; Exercising +XS n = 6; Control + STD n = 8; Control + XS n = 3). Blood and vastus lateralis biopsies were drawn at baseline and 6 months. The rise in blood lactate in submaximal treadmill tests was suppressed in the Exercising + XS group. After 6 months, intramuscular free amino acids (including the branched chain amino acids) in the Exercising + STD group showed a striking chronic depletion. This did not occur in the Exercising + XS group. The effect in Exercising + XS patients was accompanied by reduced transcription of ubiquitin E3-ligase MuRF1 which activates proteolysis via the ubiquitin-proteasome pathway. Other anabolic indicators (Akt activation and suppression of the 14 kDa actin catabolic marker) were unaffected in Exercising + XS patients. Possibly because of this, overall suppression of myofibrillar proteolysis (3-methylhistidine output) was not observed. It is suggested that alkali effects in exercisers arose by countering exercise-induced acidosis. Whether further anabolic effects are attainable on combining alkali with enhanced exercise (e.g. resistance exercise) merits further investigation.
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197
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Metzler R, Meleshkevitch EA, Fox J, Kim H, Boudko DY. An SLC6 transporter of the novel B(0,)- system aids in absorption and detection of nutrient amino acids in Caenorhabditis elegans. ACTA ACUST UNITED AC 2013; 216:2843-57. [PMID: 23580723 DOI: 10.1242/jeb.081497] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Nutrient amino acid transporters (NATs) of solute carrier family 6 (SLC6) mediate uptake of essential amino acids in mammals and insects. Phylogenomic analysis of the Caenorhabditis elegans (Ce) SLC6 family identifies five genes paralogous to an insect-specific NAT subfamily. Here we cloned and characterized the first representative of the identified nematode-specific transporters, SNF-5. SNF-5 mediates broad spectrum cation-coupled transport of neutral amino acids with submillimolar affinities and stoichiometry of 1 AA:1 Na(+), except for 1 l-Pro:2 Na(+). Unexpectedly, it transports acidic l-Glu(-) and l-Asp(-) (1 AA(-):3 Na(+)), revealing it to be the first member of a new B(0,-) system among characterized SLC6 transporters. This activity correlates with a unique positively charged His(+) 377 in the substrate-binding pocket. snf-5 promoter-driven enhanced green fluorescent protein labels intestinal cells INT1-9 and three pairs of amphid sensory neurons: ASI, ADF and ASK. These cells are intimately involved in control of dauer diapause, development, metabolism and longevity. The snf-5 deletion mutants do not show apparent morphological disorders, but increase dauer formation while reducing dauer maintenance upon starvation. Overall, the present study characterized the first nematode-specific NAT and revealed important structural and functional aspects of this transporter. In addition to the predictable role in alimentary amino acid absorption, our results indicate possible neuronal roles of SNF-5 as an amino acid provider to specific neuronal functions, including sensing of amino acid availability.
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Affiliation(s)
- Ryan Metzler
- The Department of Physiology and Biophysics of the Rosalind Franklin University of Medicine and Science, Chicago Medical School, North Chicago, IL 60064, USA
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198
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Burdakov D, Karnani MM, Gonzalez A. Lateral hypothalamus as a sensor-regulator in respiratory and metabolic control. Physiol Behav 2013; 121:117-24. [PMID: 23562864 DOI: 10.1016/j.physbeh.2013.03.023] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 02/25/2013] [Accepted: 03/06/2013] [Indexed: 02/04/2023]
Abstract
Physiological fluctuations in the levels of hormones, nutrients, and gasses are sensed in parallel by interacting control systems distributed throughout the brain and body. We discuss the logic of this arrangement and the definitions of "sensing"; and then focus on lateral hypothalamic (LH) control of energy balance and respiration. LH neurons control diverse behavioral and autonomic processes by projecting throughout the neuraxis. Three recently characterized types of LH cells are discussed here. LH orexin/hypocretin (ORX) neurons fire predominantly during wakefulness and are thought to promote reward-seeking, arousal, obesity resistance, and adaptive thermogenesis. Bidirectional control of ORX cells by extracellular macronutrients may add a new regulatory loop to these processes. ORX neurons also stimulate breathing and are activated by acid/CO2in vivo and in vitro. LH melanin-concentrating hormone (MCH) neurons fire mostly during sleep, promote physical inactivity, weight gain, and may impair glucose tolerance. Reported stimulation of MCH neurons by glucose may thus modulate energy homeostasis. Leptin receptor (LepR) neurons of the LH are distinct from ORX and MCH neurons, and may suppress feeding and locomotion by signaling to the mesolimbic dopamine system and local ORX neurons. Integration within the ORX-MCH-LepR microcircuit is suggested by anatomical and behavioral data, but requires clarification with direct assays of functional connectivity. Further studies of how LH circuits counteract evolutionarily-relevant environmental fluctuations will provide key information about the logic and fragilities of brain controllers of healthy homeostasis.
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Affiliation(s)
- Denis Burdakov
- King's College London, MRC Center for Developmental Neurobiology, London, UK; MRC National Institute for Medical Research, London, UK.
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199
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Gaccioli F, Lager S, Powell TL, Jansson T. Placental transport in response to altered maternal nutrition. J Dev Orig Health Dis 2013; 4:101-15. [PMID: 25054676 PMCID: PMC4237017 DOI: 10.1017/s2040174412000529] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The mechanisms linking maternal nutrition to fetal growth and programming of adult disease remain to be fully established. We review data on changes in placental transport in response to altered maternal nutrition, including compromized utero-placental blood flow. In human intrauterine growth restriction and in most animal models involving maternal undernutrition or restricted placental blood flow, the activity of placental transporters, in particular for amino acids, is decreased in late pregnancy. The effect of maternal overnutrition on placental transport remains largely unexplored. However, some, but not all, studies in women with diabetes giving birth to large babies indicate an upregulation of placental transporters for amino acids, glucose and fatty acids. These data support the concept that the placenta responds to maternal nutritional cues by altering placental function to match fetal growth to the ability of the maternal supply line to allocate resources to the fetus. On the other hand, some findings in humans and mice suggest that placental transporters are regulated in response to fetal demand signals. These observations are consistent with the idea that fetal signals regulate placental function to compensate for changes in nutrient availability. We propose that the placenta integrates maternal and fetal nutritional cues with information from intrinsic nutrient sensors. Together, these signals regulate placental growth and nutrient transport to balance fetal demand with the ability of the mother to support pregnancy. Thus, the placenta plays a critical role in modulating maternal-fetal resource allocation, thereby affecting fetal growth and the long-term health of the offspring.
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Affiliation(s)
- F Gaccioli
- Department of Obstetrics and Gynecology, Center for Pregnancy and Newborn Research, University of Texas Health Science Center, San Antonio, TX, USA
| | - S Lager
- Department of Obstetrics and Gynecology, Center for Pregnancy and Newborn Research, University of Texas Health Science Center, San Antonio, TX, USA
| | - T L Powell
- Department of Obstetrics and Gynecology, Center for Pregnancy and Newborn Research, University of Texas Health Science Center, San Antonio, TX, USA
| | - T Jansson
- Department of Obstetrics and Gynecology, Center for Pregnancy and Newborn Research, University of Texas Health Science Center, San Antonio, TX, USA
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200
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McCracken AN, Edinger AL. Nutrient transporters: the Achilles' heel of anabolism. Trends Endocrinol Metab 2013; 24:200-8. [PMID: 23402769 PMCID: PMC3617053 DOI: 10.1016/j.tem.2013.01.002] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2012] [Revised: 01/03/2013] [Accepted: 01/04/2013] [Indexed: 01/08/2023]
Abstract
Highly proliferative cells, including cancer cells, require a constant supply of molecular building blocks to support their growth. To acquire substrates such as glucose and amino acids from the extracellular space, dividing cells rely on transporter proteins in the plasma membrane. Numerous studies link transcriptional and post-translational control of nutrient transporter expression with proliferation, highlighting the importance of nutrient transporters in both physiologic and pathologic growth. Here we review recent work that spotlights the crucial role of nutrient transporters in cell growth and proliferation, discuss post-translational mechanisms for coordinating expression of different transporters, and consider the therapeutic potential of targeting these proteins in cancer and other diseases characterized by inappropriate cell division.
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Affiliation(s)
| | - Aimee L. Edinger
- Corresponding Author: Aimee L. Edinger 2128 Natural Sciences 1 University of California, Irvine Irvine, CA 92697-2300 Tel: 949-824-1921 FAX: 949-824-4709
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