1
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Contreras EG, Sierralta J. The Fly Blood-Brain Barrier Fights Against Nutritional Stress. Neurosci Insights 2022; 17:26331055221120252. [PMID: 36225749 PMCID: PMC9549514 DOI: 10.1177/26331055221120252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 08/01/2022] [Indexed: 11/17/2022] Open
Abstract
In the wild, animals face different challenges including multiple events of food
scarcity. How they overcome these conditions is essential for survival. Thus,
adaptation mechanisms evolved to allow the development and survival of an
organism during nutrient restriction periods. Given the high energy demand of
the nervous system, the molecular mechanisms of adaptation to malnutrition are
of great relevance to fuel the brain. The blood-brain barrier (BBB) is the
interface between the central nervous system (CNS) and the circulatory system.
The BBB mediates the transport of macromolecules in and out of the CNS, and
therefore, it can buffer changes in nutrient availability. In this review, we
collect the current evidence using the fruit fly, Drosophila
melanogaster, as a model of the role of the BBB in the adaptation
to starvation. We discuss the role of the Drosophila BBB during
nutrient deprivation as a potential sensor for circulating nutrients, and
transient nutrient storage as a regulator of the CNS neurogenic niche.
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Affiliation(s)
- Esteban G Contreras
- Institute of Neuro- and Behavioral Biology, University of Münster, Münster, Germany
| | - Jimena Sierralta
- Biomedical Neuroscience Institute and Department of Neuroscience, Faculty of Medicine, Universidad de Chile, Santiago, Chile
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2
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Glucose transporters in brain in health and disease. Pflugers Arch 2020; 472:1299-1343. [PMID: 32789766 PMCID: PMC7462931 DOI: 10.1007/s00424-020-02441-x] [Citation(s) in RCA: 219] [Impact Index Per Article: 54.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 07/20/2020] [Accepted: 07/24/2020] [Indexed: 12/15/2022]
Abstract
Energy demand of neurons in brain that is covered by glucose supply from the blood is ensured by glucose transporters in capillaries and brain cells. In brain, the facilitative diffusion glucose transporters GLUT1-6 and GLUT8, and the Na+-d-glucose cotransporters SGLT1 are expressed. The glucose transporters mediate uptake of d-glucose across the blood-brain barrier and delivery of d-glucose to astrocytes and neurons. They are critically involved in regulatory adaptations to varying energy demands in response to differing neuronal activities and glucose supply. In this review, a comprehensive overview about verified and proposed roles of cerebral glucose transporters during health and diseases is presented. Our current knowledge is mainly based on experiments performed in rodents. First, the functional properties of human glucose transporters expressed in brain and their cerebral locations are described. Thereafter, proposed physiological functions of GLUT1, GLUT2, GLUT3, GLUT4, and SGLT1 for energy supply to neurons, glucose sensing, central regulation of glucohomeostasis, and feeding behavior are compiled, and their roles in learning and memory formation are discussed. In addition, diseases are described in which functional changes of cerebral glucose transporters are relevant. These are GLUT1 deficiency syndrome (GLUT1-SD), diabetes mellitus, Alzheimer’s disease (AD), stroke, and traumatic brain injury (TBI). GLUT1-SD is caused by defect mutations in GLUT1. Diabetes and AD are associated with changed expression of glucose transporters in brain, and transporter-related energy deficiency of neurons may contribute to pathogenesis of AD. Stroke and TBI are associated with changes of glucose transporter expression that influence clinical outcome.
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3
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Veys K, Fan Z, Ghobrial M, Bouché A, García-Caballero M, Vriens K, Conchinha NV, Seuwen A, Schlegel F, Gorski T, Crabbé M, Gilardoni P, Ardicoglu R, Schaffenrath J, Casteels C, De Smet G, Smolders I, Van Laere K, Abel ED, Fendt SM, Schroeter A, Kalucka J, Cantelmo AR, Wälchli T, Keller A, Carmeliet P, De Bock K. Role of the GLUT1 Glucose Transporter in Postnatal CNS Angiogenesis and Blood-Brain Barrier Integrity. Circ Res 2020; 127:466-482. [PMID: 32404031 PMCID: PMC7386868 DOI: 10.1161/circresaha.119.316463] [Citation(s) in RCA: 99] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Supplemental Digital Content is available in the text. Rationale: Endothelial cells (ECs) are highly glycolytic and generate the majority of their energy via the breakdown of glucose to lactate. At the same time, a main role of ECs is to allow the transport of glucose to the surrounding tissues. GLUT1 (glucose transporter isoform 1/Slc2a1) is highly expressed in ECs of the central nervous system (CNS) and is often implicated in blood-brain barrier (BBB) dysfunction, but whether and how GLUT1 controls EC metabolism and function is poorly understood. Objective: We evaluated the role of GLUT1 in endothelial metabolism and function during postnatal CNS development as well as at the adult BBB. Methods and Results: Inhibition of GLUT1 decreases EC glucose uptake and glycolysis, leading to energy depletion and the activation of the cellular energy sensor AMPK (AMP-activated protein kinase), and decreases EC proliferation without affecting migration. Deletion of GLUT1 from the developing postnatal retinal endothelium reduces retinal EC proliferation and lowers vascular outgrowth, without affecting the number of tip cells. In contrast, in the brain, we observed a lower number of tip cells in addition to reduced brain EC proliferation, indicating that within the CNS, organotypic differences in EC metabolism exist. Interestingly, when ECs become quiescent, endothelial glycolysis is repressed, and GLUT1 expression increases in a Notch-dependent fashion. GLUT1 deletion from quiescent adult ECs leads to severe seizures, accompanied by neuronal loss and CNS inflammation. Strikingly, this does not coincide with BBB leakiness, altered expression of genes crucial for BBB barrier functioning nor reduced vascular function. Instead, we found a selective activation of inflammatory and extracellular matrix related gene sets. Conclusions: GLUT1 is the main glucose transporter in ECs and becomes uncoupled from glycolysis during quiescence in a Notch-dependent manner. It is crucial for developmental CNS angiogenesis and adult CNS homeostasis but does not affect BBB barrier function.
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Affiliation(s)
- Koen Veys
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven
| | - Zheng Fan
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.)
| | - Moheb Ghobrial
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.).,Group of CNS Angiogenesis and Neurovascular Link, Neuroscience Center Zurich, University of Zurich (UZH) and ETHZ and Division of Neurosurgery, USZ, Zurich (M.G., T.W.)
| | - Ann Bouché
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven
| | - Melissa García-Caballero
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven
| | - Kim Vriens
- Laboratory of Cellular Metabolism and Metabolic Regulation, Department of Oncology (K. Vriens, S.-M.F.), KU Leuven.,Laboratory of Cellular Metabolism and Metabolic Regulation (K. Vriens, S.-M.F.), Center for Cancer Biology, VIB, Leuven
| | - Nadine Vasconcelos Conchinha
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven
| | - Aline Seuwen
- Institute for Biomedical Engineering (A. Seuwen, F.S., A. Schroeter), UZH/ETHZ, Zurich, Switzerland.,Institute of Pharmacology and Toxicology, UZH, Zurich, Switzerland (A. Seuwen, F.S., A. Schroeter)
| | - Felix Schlegel
- Institute for Biomedical Engineering (A. Seuwen, F.S., A. Schroeter), UZH/ETHZ, Zurich, Switzerland.,Institute of Pharmacology and Toxicology, UZH, Zurich, Switzerland (A. Seuwen, F.S., A. Schroeter)
| | - Tatiane Gorski
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.)
| | - Melissa Crabbé
- Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, University Hospitals Leuven, Belgium (M.C., C.C., K.V.L.).,Molecular Small Animal Imaging Centre, KU Leuven (M.C., C.C., K.V.L.)
| | - Paola Gilardoni
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.)
| | - Raphaela Ardicoglu
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.)
| | - Johanna Schaffenrath
- Neuroscience Center Zurich (J.S., A.K.), UZH/ETHZ, Zurich, Switzerland.,Department of Neurosurgery, Clinical Neurocentre, USZ, Zurich (J.S., A.K.)
| | - Cindy Casteels
- Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, University Hospitals Leuven, Belgium (M.C., C.C., K.V.L.).,Molecular Small Animal Imaging Centre, KU Leuven (M.C., C.C., K.V.L.)
| | - Gino De Smet
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Center for Neurosciences, Vrije Universiteit Brussel (G.D.S., I.S.)
| | - Ilse Smolders
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Center for Neurosciences, Vrije Universiteit Brussel (G.D.S., I.S.)
| | - Koen Van Laere
- Nuclear Medicine and Molecular Imaging, Department of Imaging and Pathology, KU Leuven, University Hospitals Leuven, Belgium (M.C., C.C., K.V.L.).,Molecular Small Animal Imaging Centre, KU Leuven (M.C., C.C., K.V.L.)
| | - E Dale Abel
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.).,Fraternal Order of Eagles Diabetes Research Center (E.D.A.), University of Iowa.,Division of Endocrinology and Metabolism, Carver College of Medicine (E.D.A.), University of Iowa
| | - Sarah-Maria Fendt
- Laboratory of Cellular Metabolism and Metabolic Regulation, Department of Oncology (K. Vriens, S.-M.F.), KU Leuven.,Laboratory of Cellular Metabolism and Metabolic Regulation (K. Vriens, S.-M.F.), Center for Cancer Biology, VIB, Leuven
| | - Aileen Schroeter
- Institute for Biomedical Engineering (A. Seuwen, F.S., A. Schroeter), UZH/ETHZ, Zurich, Switzerland.,Institute of Pharmacology and Toxicology, UZH, Zurich, Switzerland (A. Seuwen, F.S., A. Schroeter)
| | - Joanna Kalucka
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven.,Aarhus Institute of advanced studies (AIAS) and Department of Biomedicine, Aarhus University (J.K.)
| | - Anna Rita Cantelmo
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven.,Université de Lille, INSERM U1003, Physiologie Cellulaire, France (A.R.C.)
| | - Thomas Wälchli
- Group of CNS Angiogenesis and Neurovascular Link, Neuroscience Center Zurich, University of Zurich (UZH) and ETHZ and Division of Neurosurgery, USZ, Zurich (M.G., T.W.).,Group of Brain Vasculature and Neurovascular Unit, Department of Clinical Neurosciences, University Hospital Geneva (T.W.).,Department of Fundamental Neurobiology, Krembil Research Institute (T.W.), Toronto Western Hospital, University Health Network, University of Toronto.,Division of Neurosurgery, Department of Surgery (T.W.), Toronto Western Hospital, University Health Network, University of Toronto
| | - Annika Keller
- Neuroscience Center Zurich (J.S., A.K.), UZH/ETHZ, Zurich, Switzerland.,Department of Neurosurgery, Clinical Neurocentre, USZ, Zurich (J.S., A.K.)
| | - Peter Carmeliet
- From the Laboratory of Angiogenesis and Vascular Metabolism, Department of Oncology (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), KU Leuven.,Laboratory of Angiogenesis and Vascular Metabolism (K. Veys, A.B., M.G.-C., N.V.C., J.K., A.R.C., P.C.), Center for Cancer Biology, VIB, Leuven
| | - Katrien De Bock
- Laboratory of Exercise and Health, Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETHZ) Zurich (Z.F., M.G., T.G., P.G., R.A., K.D.B.)
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4
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Yazdani S, Jaldin‐Fincati JR, Pereira RVS, Klip A. Endothelial cell barriers: Transport of molecules between blood and tissues. Traffic 2019; 20:390-403. [DOI: 10.1111/tra.12645] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 04/02/2019] [Accepted: 04/02/2019] [Indexed: 12/25/2022]
Affiliation(s)
- Samaneh Yazdani
- Cell Biology ProgramThe Hospital for Sick Children Toronto Ontario Canada
| | | | | | - Amira Klip
- Cell Biology ProgramThe Hospital for Sick Children Toronto Ontario Canada
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5
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Masuda T, Hoshiyama T, Uemura T, Hirayama-Kurogi M, Ogata S, Furukawa A, Couraud PO, Furihata T, Ito S, Ohtsuki S. Large-Scale Quantitative Comparison of Plasma Transmembrane Proteins between Two Human Blood–Brain Barrier Model Cell Lines, hCMEC/D3 and HBMEC/ciβ. Mol Pharm 2019; 16:2162-2171. [DOI: 10.1021/acs.molpharmaceut.9b00114] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Takeshi Masuda
- AMED-CREST, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda, Tokyo 100-0004, Japan
| | | | | | | | | | | | - Pierre-Olivier Couraud
- Institut Cochin, Paris Descartes University, Inserm U1016, CNRS UMR8104, Paris 75014, France
| | - Tomomi Furihata
- Department of Pharmacology, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba-shi, Chiba 260-8670 Japan
| | - Shingo Ito
- AMED-CREST, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda, Tokyo 100-0004, Japan
| | - Sumio Ohtsuki
- AMED-CREST, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda, Tokyo 100-0004, Japan
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6
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Hladky SB, Barrand MA. Elimination of substances from the brain parenchyma: efflux via perivascular pathways and via the blood-brain barrier. Fluids Barriers CNS 2018; 15:30. [PMID: 30340614 PMCID: PMC6194691 DOI: 10.1186/s12987-018-0113-6] [Citation(s) in RCA: 126] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 08/30/2018] [Indexed: 02/06/2023] Open
Abstract
This review considers efflux of substances from brain parenchyma quantified as values of clearances (CL, stated in µL g-1 min-1). Total clearance of a substance is the sum of clearance values for all available routes including perivascular pathways and the blood-brain barrier. Perivascular efflux contributes to the clearance of all water-soluble substances. Substances leaving via the perivascular routes may enter cerebrospinal fluid (CSF) or lymph. These routes are also involved in entry to the parenchyma from CSF. However, evidence demonstrating net fluid flow inwards along arteries and then outwards along veins (the glymphatic hypothesis) is still lacking. CLperivascular, that via perivascular routes, has been measured by following the fate of exogenously applied labelled tracer amounts of sucrose, inulin or serum albumin, which are not metabolized or eliminated across the blood-brain barrier. With these substances values of total CL ≅ 1 have been measured. Substances that are eliminated at least partly by other routes, i.e. across the blood-brain barrier, have higher total CL values. Substances crossing the blood-brain barrier may do so by passive, non-specific means with CLblood-brain barrier values ranging from < 0.01 for inulin to > 1000 for water and CO2. CLblood-brain barrier values for many small solutes are predictable from their oil/water partition and molecular weight. Transporters specific for glucose, lactate and many polar substrates facilitate efflux across the blood-brain barrier producing CLblood-brain barrier values > 50. The principal route for movement of Na+ and Cl- ions across the blood-brain barrier is probably paracellular through tight junctions between the brain endothelial cells producing CLblood-brain barrier values ~ 1. There are large fluxes of amino acids into and out of the brain across the blood-brain barrier but only small net fluxes have been observed suggesting substantial reuse of essential amino acids and α-ketoacids within the brain. Amyloid-β efflux, which is measurably faster than efflux of inulin, is primarily across the blood-brain barrier. Amyloid-β also leaves the brain parenchyma via perivascular efflux and this may be important as the route by which amyloid-β reaches arterial walls resulting in cerebral amyloid angiopathy.
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Affiliation(s)
- Stephen B. Hladky
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
| | - Margery A. Barrand
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
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7
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Lloyd KP, Ojelabi OA, De Zutter JK, Carruthers A. Reconciling contradictory findings: Glucose transporter 1 (GLUT1) functions as an oligomer of allosteric, alternating access transporters. J Biol Chem 2017; 292:21035-21046. [PMID: 29066623 DOI: 10.1074/jbc.m117.815589] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 10/23/2017] [Indexed: 11/06/2022] Open
Abstract
Recent structural studies suggest that GLUT1 (glucose transporter 1)-mediated sugar transport is mediated by an alternating access transporter that successively presents exofacial (e2) and endofacial (e1) substrate-binding sites. Transport studies, however, indicate multiple, interacting (allosteric), and co-existent, exo- and endofacial GLUT1 ligand-binding sites. The present study asks whether these contradictory conclusions result from systematic analytical error or reveal a more fundamental relationship between transporter structure and function. Here, homology modeling supported the alternating access transporter model for sugar transport by confirming at least four GLUT1 conformations, the so-called outward, outward-occluded, inward-occluded, and inward GLUT1 conformations. Results from docking analysis suggested that outward and outward-occluded conformations present multiple β-d-glucose and maltose interaction sites, whereas inward-occluded and inward conformations present only a single β-d-glucose interaction site. Gln-282 contributed to sugar binding in all GLUT1 conformations via hydrogen bonding. Mutating Gln-282 to alanine (Q282A) doubled the Km(app) for 2-deoxy-d-glucose uptake and eliminated cis-allostery (stimulation of sugar uptake by subsaturating extracellular maltose) but not trans-allostery (uptake stimulation by subsaturating cytochalasin B). cis-Allostery persisted, but trans-allostery was lost in an oligomerization-deficient GLUT1 variant in which we substituted membrane helix 9 with the equivalent GLUT3 sequence. Moreover, Q282A eliminated cis-allostery in the oligomerization variant. These findings reconcile contradictory conclusions from structural and transport studies by suggesting that GLUT1 is an oligomer of allosteric, alternating access transporters in which 1) cis-allostery is mediated by intrasubunit interactions and 2) trans-allostery requires intersubunit interactions.
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Affiliation(s)
- Kenneth P Lloyd
- From the Department of Biochemistry and Molecular Pharmacology, Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Ogooluwa A Ojelabi
- From the Department of Biochemistry and Molecular Pharmacology, Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Julie K De Zutter
- From the Department of Biochemistry and Molecular Pharmacology, Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Anthony Carruthers
- From the Department of Biochemistry and Molecular Pharmacology, Graduate School of Biomedical Sciences, University of Massachusetts Medical School, Worcester, Massachusetts 01605
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8
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Tomioka NH, Tamura Y, Takada T, Shibata S, Suzuki H, Uchida S, Hosoyamada M. Immunohistochemical and in situ hybridization study of urate transporters GLUT9/URATv1, ABCG2, and URAT1 in the murine brain. Fluids Barriers CNS 2016; 13:22. [PMID: 27955673 PMCID: PMC5154092 DOI: 10.1186/s12987-016-0046-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 11/26/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Uric acid (UA) is known to exert neuroprotective effects in the brain. However, the mechanism of UA regulation in the brain is not well characterized. In our previous study, we described that the mouse urate transporter URAT1 is localized to the cilia and apical surface of ventricular ependymal cells. To further strengthen the hypothesis that UA is transported transcellularly at the ependymal cells, we aimed to assess the distribution of other UA transporters in the murine brain. METHODS Immunostaining and highly-sensitive in situ hybridization was used to assess the distribution of UA transporters: GLUT9/URATv1, ABCG2, and URAT1. RESULTS Immunostaining for GLUT9 was observed in ependymal cells, neurons, and brain capillaries. Immunostaining for ABCG2 was observed in the choroid plexus epithelium and brain capillaries, but not in ependymal cells. These results were validated by in situ hybridization. CONCLUSIONS We propose that given their specific expression patterns in ependymal, choroid plexus epithelial, and brain capillary endothelial cells in this study, UA may be transported by these UA transporters in the murine brain. This may provide a novel strategy for targeted neuroprotection.
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Affiliation(s)
- Naoko H. Tomioka
- Department of Human Physiology and Pathology, Faculty of Pharma-Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605 Japan
| | - Yoshifuru Tamura
- Department of Internal Medicine, Teikyo University School of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605 Japan
| | - Tappei Takada
- Department of Pharmacy, The University of Tokyo Hospital, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655 Japan
| | - Shigeru Shibata
- Department of Internal Medicine, Teikyo University School of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605 Japan
| | - Hiroshi Suzuki
- Department of Pharmacy, The University of Tokyo Hospital, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655 Japan
| | - Shunya Uchida
- Department of Internal Medicine, Teikyo University School of Medicine, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605 Japan
| | - Makoto Hosoyamada
- Department of Human Physiology and Pathology, Faculty of Pharma-Sciences, Teikyo University, 2-11-1 Kaga, Itabashi-ku, Tokyo, 173-8605 Japan
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9
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Myers RB, Fomovsky GM, Lee S, Tan M, Wang BF, Patwari P, Yoshioka J. Deletion of thioredoxin-interacting protein improves cardiac inotropic reserve in the streptozotocin-induced diabetic heart. Am J Physiol Heart Circ Physiol 2016; 310:H1748-59. [PMID: 27037370 DOI: 10.1152/ajpheart.00051.2016] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 03/25/2016] [Indexed: 02/05/2023]
Abstract
Although the precise pathogenesis of diabetic cardiac damage remains unclear, potential mechanisms include increased oxidative stress, autonomic nervous dysfunction, and altered cardiac metabolism. Thioredoxin-interacting protein (Txnip) was initially identified as an inhibitor of the antioxidant thioredoxin but is now recognized as a member of the arrestin superfamily of adaptor proteins that classically regulate G protein-coupled receptor signaling. Here we show that Txnip plays a key role in diabetic cardiomyopathy. High glucose levels induced Txnip expression in rat cardiomyocytes in vitro and in the myocardium of streptozotocin-induced diabetic mice in vivo. While hyperglycemia did not induce cardiac dysfunction at baseline, β-adrenergic challenge revealed a blunted myocardial inotropic response in diabetic animals (24-wk-old male and female C57BL/6;129Sv mice). Interestingly, diabetic mice with cardiomyocyte-specific deletion of Txnip retained a greater cardiac response to β-adrenergic stimulation than wild-type mice. This benefit in Txnip-knockout hearts was not related to the level of thioredoxin activity or oxidative stress. Unlike the β-arrestins, Txnip did not interact with β-adrenergic receptors to desensitize downstream signaling. However, our proteomic and functional analyses demonstrated that Txnip inhibits glucose transport through direct binding to glucose transporter 1 (GLUT1). An ex vivo analysis of perfused hearts further demonstrated that the enhanced functional reserve afforded by deletion of Txnip was associated with myocardial glucose utilization during β-adrenergic stimulation. These data provide novel evidence that hyperglycemia-induced Txnip is responsible for impaired cardiac inotropic reserve by direct regulation of insulin-independent glucose uptake through GLUT1 and plays a role in the development of diabetic cardiomyopathy.
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Affiliation(s)
- Ronald B Myers
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Gregory M Fomovsky
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Samuel Lee
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Max Tan
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Bing F Wang
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Parth Patwari
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
| | - Jun Yoshioka
- Cardiovascular Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts
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Glucose Transporters at the Blood-Brain Barrier: Function, Regulation and Gateways for Drug Delivery. Mol Neurobiol 2016; 54:1046-1077. [PMID: 26801191 DOI: 10.1007/s12035-015-9672-6] [Citation(s) in RCA: 204] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Accepted: 12/17/2015] [Indexed: 12/31/2022]
Abstract
Glucose transporters (GLUTs) at the blood-brain barrier maintain the continuous high glucose and energy demands of the brain. They also act as therapeutic targets and provide routes of entry for drug delivery to the brain and central nervous system for treatment of neurological and neurovascular conditions and brain tumours. This article first describes the distribution, function and regulation of glucose transporters at the blood-brain barrier, the major ones being the sodium-independent facilitative transporters GLUT1 and GLUT3. Other GLUTs and sodium-dependent transporters (SGLTs) have also been identified at lower levels and under various physiological conditions. It then considers the effects on glucose transporter expression and distribution of hypoglycemia and hyperglycemia associated with diabetes and oxygen/glucose deprivation associated with cerebral ischemia. A reduction in glucose transporters at the blood-brain barrier that occurs before the onset of the main pathophysiological changes and symptoms of Alzheimer's disease is a potential causative effect in the vascular hypothesis of the disease. Mutations in glucose transporters, notably those identified in GLUT1 deficiency syndrome, and some recreational drug compounds also alter the expression and/or activity of glucose transporters at the blood-brain barrier. Approaches for drug delivery across the blood-brain barrier include the pro-drug strategy whereby drug molecules are conjugated to glucose transporter substrates or encapsulated in nano-enabled delivery systems (e.g. liposomes, micelles, nanoparticles) that are functionalised to target glucose transporters. Finally, the continuous development of blood-brain barrier in vitro models is important for studying glucose transporter function, effects of disease conditions and interactions with drugs and xenobiotics.
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11
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Abstract
In this issue, Lee et al. (2015) show that PKC directly phosphorylates the glucose transporter Glut1, in order to promote glucose uptake in response to growth factor signaling.
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Affiliation(s)
- Peter J Siska
- Department of Pharmacology and Cancer Biology, Department of Immunology, Duke Molecular Physiology Institute, Duke University, Durham, NC 27710, USA
| | - Jeffrey C Rathmell
- Department of Pharmacology and Cancer Biology, Department of Immunology, Duke Molecular Physiology Institute, Duke University, Durham, NC 27710, USA.
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12
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Lee EE, Ma J, Sacharidou A, Mi W, Salato VK, Nguyen N, Jiang Y, Pascual JM, North PE, Shaul PW, Mettlen M, Wang RC. A Protein Kinase C Phosphorylation Motif in GLUT1 Affects Glucose Transport and is Mutated in GLUT1 Deficiency Syndrome. Mol Cell 2015; 58:845-53. [PMID: 25982116 DOI: 10.1016/j.molcel.2015.04.015] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Revised: 03/09/2015] [Accepted: 04/07/2015] [Indexed: 12/31/2022]
Abstract
Protein kinase C has been implicated in the phosphorylation of the erythrocyte/brain glucose transporter, GLUT1, without a clear understanding of the site(s) of phosphorylation and the possible effects on glucose transport. Through in vitro kinase assays, mass spectrometry, and phosphospecific antibodies, we identify serine 226 in GLUT1 as a PKC phosphorylation site. Phosphorylation of S226 is required for the rapid increase in glucose uptake and enhanced cell surface localization of GLUT1 induced by the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Endogenous GLUT1 is phosphorylated on S226 in primary endothelial cells in response to TPA or VEGF. Several naturally occurring, pathogenic mutations that cause GLUT1 deficiency syndrome disrupt this PKC phosphomotif, impair the phosphorylation of S226 in vitro, and block TPA-mediated increases in glucose uptake. We demonstrate that the phosphorylation of GLUT1 on S226 regulates glucose transport and propose that this modification is important in the physiological regulation of glucose transport.
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Affiliation(s)
- Eunice E Lee
- Department of Dermatology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jing Ma
- Department of Dermatology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | | | - Wentao Mi
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Valerie K Salato
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Nam Nguyen
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Youxing Jiang
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Juan M Pascual
- Department of Pediatrics, UT Southwestern Medical Center, Dallas, TX 75390, USA; Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Paula E North
- Department of Pathology, Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Philip W Shaul
- Department of Pediatrics, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Marcel Mettlen
- Department of Cell Biology, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Richard C Wang
- Department of Dermatology, UT Southwestern Medical Center, Dallas, TX 75390, USA.
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13
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Cura AJ, Carruthers A. Role of monosaccharide transport proteins in carbohydrate assimilation, distribution, metabolism, and homeostasis. Compr Physiol 2013; 2:863-914. [PMID: 22943001 DOI: 10.1002/cphy.c110024] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The facilitated diffusion of glucose, galactose, fructose, urate, myoinositol, and dehydroascorbicacid in mammals is catalyzed by a family of 14 monosaccharide transport proteins called GLUTs. These transporters may be divided into three classes according to sequence similarity and function/substrate specificity. GLUT1 appears to be highly expressed in glycolytically active cells and has been coopted in vitamin C auxotrophs to maintain the redox state of the blood through transport of dehydroascorbate. Several GLUTs are definitive glucose/galactose transporters, GLUT2 and GLUT5 are physiologically important fructose transporters, GLUT9 appears to be a urate transporter while GLUT13 is a proton/myoinositol cotransporter. The physiologic substrates of some GLUTs remain to be established. The GLUTs are expressed in a tissue specific manner where affinity, specificity, and capacity for substrate transport are paramount for tissue function. Although great strides have been made in characterizing GLUT-catalyzed monosaccharide transport and mapping GLUT membrane topography and determinants of substrate specificity, a unifying model for GLUT structure and function remains elusive. The GLUTs play a major role in carbohydrate homeostasis and the redistribution of sugar-derived carbons among the various organ systems. This is accomplished through a multiplicity of GLUT-dependent glucose sensing and effector mechanisms that regulate monosaccharide ingestion, absorption,distribution, cellular transport and metabolism, and recovery/retention. Glucose transport and metabolism have coevolved in mammals to support cerebral glucose utilization.
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Affiliation(s)
- Anthony J Cura
- Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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14
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Characterization and Modulation of Glucose Uptake in a Human Blood–Brain Barrier Model. J Membr Biol 2013; 246:669-77. [DOI: 10.1007/s00232-013-9583-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 08/04/2013] [Indexed: 10/26/2022]
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15
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De Zutter JK, Levine KB, Deng D, Carruthers A. Sequence determinants of GLUT1 oligomerization: analysis by homology-scanning mutagenesis. J Biol Chem 2013; 288:20734-44. [PMID: 23720776 DOI: 10.1074/jbc.m113.469023] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human blood-brain barrier glucose transport protein (GLUT1) forms homodimers and homotetramers in detergent micelles and in cell membranes, where the GLUT1 oligomeric state determines GLUT1 transport behavior. GLUT1 and the neuronal glucose transporter GLUT3 do not form heterocomplexes in human embryonic kidney 293 (HEK293) cells as judged by co-immunoprecipitation assays. Using homology-scanning mutagenesis in which GLUT1 domains are substituted with equivalent GLUT3 domains and vice versa, we show that GLUT1 transmembrane helix 9 (TM9) is necessary for optimal association of GLUT1-GLUT3 chimeras with parental GLUT1 in HEK cells. GLUT1 TMs 2, 5, 8, and 11 also contribute to a less abundant heterocomplex. Cell surface GLUT1 and GLUT3 containing GLUT1 TM9 are 4-fold more catalytically active than GLUT3 and GLUT1 containing GLUT3 TM9. GLUT1 and GLUT3 display allosteric transport behavior. Size exclusion chromatography of detergent solubilized, purified GLUT1 resolves GLUT1/lipid/detergent micelles as 6- and 10-nm Stokes radius particles, which correspond to GLUT1 dimers and tetramers, respectively. Studies with GLUTs expressed in and solubilized from HEK cells show that HEK cell GLUT1 resolves as 6- and 10-nm Stokes radius particles, whereas GLUT3 resolves as a 6-nm particle. Substitution of GLUT3 TM9 with GLUT1 TM9 causes chimeric GLUT3 to resolve as 6- and 10-nm Stokes radius particles. Substitution of GLUT1 TM9 with GLUT3 TM9 causes chimeric GLUT1 to resolve as a mixture of 6- and 4-nm particles. We discuss these findings in the context of determinants of GLUT oligomeric structure and transport function.
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Affiliation(s)
- Julie K De Zutter
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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Laporta J, Peters TL, Merriman KE, Vezina CM, Hernandez LL. Serotonin (5-HT) affects expression of liver metabolic enzymes and mammary gland glucose transporters during the transition from pregnancy to lactation. PLoS One 2013; 8:e57847. [PMID: 23469086 PMCID: PMC3585179 DOI: 10.1371/journal.pone.0057847] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 01/29/2013] [Indexed: 11/24/2022] Open
Abstract
The aim of this experiment was to demonstrate the ability of feeding serotonin (5-HT; 5-hydroxytryptamine) precursors to increase 5-HT production during the transition from pregnancy to lactation and the effects this has on maternal energy metabolism in the liver and mammary gland. Pregnant rats (n = 45) were fed one of three diets: I) control (CON), II) CON supplemented with 0.2% 5-hydroxytryptophan (5-HTP) or III) CON supplemented with 1.35% L-tryptophan (L-TRP), beginning on d13 of pregnancy through d9 of lactation (d9). Serum (pre and post-partum), milk (daily), liver and mammary gland tissue (d9) were collected. Serum 5-HT was increased in the 5-HTP fed dams beginning on d20 of gestation and remained elevated through d9, while it was only increased on d9 in the L-TRP fed dams. 5-HT levels were increased in mammary gland and liver of both groups. Additionally, 5-HTP fed dams had serum and milk glucose levels similar to the CON, while L-TRP had decreased serum (d9) and milk glucose (all dates evaluated). Feeding 5-HTP resulted in increased mRNA expression of key gluconeogenic and glycolytic enzymes in liver and glucose transporters 1 and 8 (GLUT-1, -8) in the mammary gland. We demonstrated the location of GLUT-8 in the mammary gland both in the epithelial and vascular endothelial cells. Finally, phosphorylated 5′ AMP-activated protein kinase (pAMPK), a known regulator of intracellular energy status, was elevated in mammary glands of 5-HTP fed dams. Our results suggest that increasing 5-HT production during the transition from pregnancy to lactation increases mRNA expression of enzymes involved in energy metabolism in the liver, and mRNA abundance and distribution of glucose transporters within the mammary gland. This suggests the possibility that 5-HT may be involved in regulating energy metabolism during the transition from pregnancy to lactation.
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Affiliation(s)
- Jimena Laporta
- Department of Dairy Science, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
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17
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Vollers SS, Carruthers A. Sequence determinants of GLUT1-mediated accelerated-exchange transport: analysis by homology-scanning mutagenesis. J Biol Chem 2012; 287:42533-44. [PMID: 23093404 DOI: 10.1074/jbc.m112.369587] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The class 1 equilibrative glucose transporters GLUT1 and GLUT4 are structurally similar but catalyze distinct modes of transport. GLUT1 exhibits trans-acceleration, in which the presence of intracellular sugar stimulates the rate of unidirectional sugar uptake. GLUT4-mediated uptake is unaffected by intracellular sugar. Using homology-scanning mutagenesis in which domains of GLUT1 are substituted with equivalent domains from GLUT4 and vice versa, we show that GLUT1 transmembrane domain 6 is both necessary and sufficient for trans-acceleration. This region is not directly involved in GLUT1 binding of substrate or inhibitors. Rather, transmembrane domain 6 is part of two putative scaffold domains, which coordinate membrane-spanning amphipathic helices that form the sugar translocation pore. We propose that GLUT1 transmembrane domain 6 restrains import when intracellular sugar is absent by slowing transport-associated conformational changes.
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Affiliation(s)
- Sabrina S Vollers
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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18
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Lee WL, Klip A. Shuttling glucose across brain microvessels, with a little help from GLUT1 and AMP kinase. Focus on "AMP kinase regulation of sugar transport in brain capillary endothelial cells during acute metabolic stress". Am J Physiol Cell Physiol 2012; 303:C803-5. [PMID: 22814398 DOI: 10.1152/ajpcell.00241.2012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Cura AJ, Carruthers A. AMP kinase regulation of sugar transport in brain capillary endothelial cells during acute metabolic stress. Am J Physiol Cell Physiol 2012; 303:C806-14. [PMID: 22763120 DOI: 10.1152/ajpcell.00437.2011] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
AMP-dependent kinase (AMPK) and GLUT1-mediated sugar transport in blood-brain barrier endothelial cells are activated during acute cellular metabolic stress. Using murine brain microvasculature endothelium bEnd.3 cells, we show that AMPK phosphorylation and stimulation of 3-O-methylglucose transport by the AMPK agonist AICAR are inhibited in a dose-dependent manner by the AMPK antagonist Compound C. AMPK α1- or AMPK α2-knockdown by RNA interference or AMPK inhibition by Compound C reduces AMPK phosphorylation and 3-O-methylglucose transport stimulation induced by cellular glucose-depletion, by potassium cyanide (KCN), or by carbonyl cyanide-p-trifluoromethoxy-phenylhydrazone (FCCP). Cell surface biotinylation studies reveal that plasma membrane GLUT1 levels are increased two- to threefold by cellular glucose depletion, AICAR or KCN treatment, and that these increases are prevented by Compound C and by AMPK α1- or α2-knockdown. These results support the hypothesis that AMPK activation in blood-brain barrier-derived endothelial cells directs the trafficking of GLUT1 intracellular pools to the plasma membrane, thereby increasing endothelial sugar transport capacity.
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Affiliation(s)
- Anthony J Cura
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, USA
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Proinflammatory Stimulants Promote the Expression of a Promiscuous G Protein-Coupled Receptor, mFPR2, in Microvascular Endothelial Cells. Inflammation 2011; 35:656-64. [DOI: 10.1007/s10753-011-9358-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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21
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Alcázar-Leyva S, Alvarado-Vásquez N. Could thiamine pyrophosphate be a regulator of the nitric oxide synthesis in the endothelial cell of diabetic patients? Med Hypotheses 2011; 76:629-31. [PMID: 21288652 DOI: 10.1016/j.mehy.2011.01.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2010] [Accepted: 01/09/2011] [Indexed: 12/12/2022]
Abstract
Thiamine (Vitamin B1) is considered an essential micronutrient for humans; its deficient intake brings about the Wernicke-Korsakoff syndrome (encephalopathy and psychosis) or beriberi (a neurological and cardiovascular disease). Once thiamine enters the cells it is phosphorylated by thiamine pyrophosphokinase (TPPK), and converted into the coenzyme thiamine pyrophosphate (TPP), the active form of thiamine. TPP is a relevant cofactor for transketolase (TK), α-ketoglutarate dehydrogenase (αKDH), and pyruvate dehydrogenase (PDH), all these enzymes are fundamental for glucose metabolism. Diabetes mellitus (DM), however, is considered both a deficient thiamine and deficient energy state, as a consequence of the limited TPP synthesis. Recent evidences have shown that the administration of thiamine or lipid-soluble derivatives, such as benfotiamine (developed to improve the bioavailability of thiamine), has positive effects in the diabetic patient (after thiamine is transformed into TPP). For this reason, administration of supplements with TPP in the diabetic patients is recommended to avoid complications, like neuropathy and nephropathy. It has been suggested that these beneficial effects are a consequence of the activation of TK (pentose pathway) or the PDH complex in mitochondria. Nitric oxide (NO) is synthesized by the endothelial cell and is also an important element for the viability and functionality of this cell type. However, in the DM patient, a deficient synthesis of NO has been reported. It is relevant to mention that recent evidences have led to propose mitochondrial activity as an important regulator of nitric oxide synthesis (ON). We consider that the exogenous administration of TPP facilitates the utilization of this molecule, regulating some metabolic processes such as phosphorylation of thiamine by TPPK, energy consumption (ATP), as well as mitochondrial activity, inducing eventually NO synthesis. If this is confirmed, the administration of TPP to the diabetic patient would provide additional protection to endothelial cells, reducing the risk of vascular damage, to which the diabetic patient is highly susceptible.
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Cardoso FL, Brites D, Brito MA. Looking at the blood-brain barrier: molecular anatomy and possible investigation approaches. ACTA ACUST UNITED AC 2010; 64:328-63. [PMID: 20685221 DOI: 10.1016/j.brainresrev.2010.05.003] [Citation(s) in RCA: 404] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 05/18/2010] [Accepted: 05/19/2010] [Indexed: 12/17/2022]
Abstract
The blood-brain barrier (BBB) is a dynamic and complex interface between blood and the central nervous system that strictly controls the exchanges between the blood and brain compartments, therefore playing a key role in brain homeostasis and providing protection against many toxic compounds and pathogens. In this review, the unique properties of brain microvascular endothelial cells and intercellular junctions are examined. The specific interactions between endothelial cells and basement membrane as well as neighboring perivascular pericytes, glial cells and neurons, which altogether constitute the neurovascular unit and play an essential role in both health and function of the central nervous system, are also explored. Some relevant pathways across the endothelium, as well as mechanisms involved in the regulation of BBB permeability, and the emerging role of the BBB as a signaling interface are addressed as well. Furthermore, we summarize some of the experimental approaches that can be used to monitor BBB properties and function in a variety of conditions and have allowed recent advances in BBB knowledge. Elucidation of the molecular anatomy and dynamics of the BBB is an essential step for the development of new strategies directed to maintain or restore BBB integrity and barrier function and ultimately preserve the delicate interstitial brain environment.
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Affiliation(s)
- Filipa Lourenço Cardoso
- Research Institute for Medicines and Pharmaceutical Sciences (iMed.UL), Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
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