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Luo X, Tao X, Ran G, Deng Y, Wang H, Tan L, Pang Z. Molecular Modification Enhances Xylose Uptake by the Sugar Transporter KM_SUT5 of Kluyveromyces marxianus. Int J Mol Sci 2024; 25:8322. [PMID: 39125891 PMCID: PMC11312716 DOI: 10.3390/ijms25158322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Revised: 07/22/2024] [Accepted: 07/27/2024] [Indexed: 08/12/2024] Open
Abstract
This research cloned and expressed the sugar transporter gene KM_SUT5 from Kluyveromyces marxianus GX-UN120, which displayed remarkable sugar transportation capabilities, including pentose sugars. To investigate the impact of point mutations on xylose transport capacity, we selected four sites, predicted the suitable amino acid sites by molecular docking, and altered their codons to construct the corresponding mutants, Q74D, Y195K, S460H, and Q464F, respectively. Furthermore, we conducted site-directed truncation on six sites of KM_SUT5p. The molecular modification resulted in significant changes in mutant growth and the D-xylose transport rate. Specifically, the S460H mutant exhibited a higher growth rate and demonstrated excellent performance across 20 g L-1 xylose, achieving the highest xylose accumulation under xylose conditions (49.94 μmol h-1 gDCW-1, DCW mean dry cell weight). Notably, mutant delA554-, in which the transporter protein SUT5 is truncated at position delA554-, significantly increased growth rates in both D-xylose and D-glucose substrates. These findings offer valuable insights into potential modifications of other sugar transporters and contribute to a deeper understanding of the C-terminal function of sugar transporters.
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Affiliation(s)
| | | | | | | | | | | | - Zongwen Pang
- College of Life Science and Technology, Guangxi University, Nanning 530004, China; (X.L.)
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2
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Dai F, Lee SO, Song JH, Yoo WG, Shin EH, Bai X, Hong SJ. Glucose transporters and sodium glucose co-transporters cooperatively import glucose into energy-demanding organs in carcinogenic liver fluke Clonorchis sinensis. PLoS Negl Trop Dis 2024; 18:e0012315. [PMID: 38968307 PMCID: PMC11253919 DOI: 10.1371/journal.pntd.0012315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2024] [Revised: 07/17/2024] [Accepted: 06/24/2024] [Indexed: 07/07/2024] Open
Abstract
BACKGROUND The liver fluke Clonorchis sinensis imports large amounts of glucose to generate energy and metabolic intermediates through glycolysis. We hypothesized that C. sinensis absorbs glucose through glucose transporters and identified four subtypes of glucose transporter (CsGTP) and one sodium glucose co-transporter (CsSGLT) in C. sinensis. METHODOLOGY/PRINCIPAL FINDINGS Expressed sequence tags encoding CsGTPs were retrieved from the C. sinensis transcriptome database, and their full-length cDNA sequences were obtained by rapid amplification of cDNA ends (RACE). The tissue distribution of glucose transporters in C. sinensis adults was determined using immunohistochemical staining. Developmental expression was measured using RT-qPCR. The transport and distribution of glucose into living C. sinensis were monitored using confocal microscopy. Membrane topology and key functional residues of CsGTPs were homologous to their counterparts in animals and humans. CsGTP1, 2, and 4 were transcribed 2.4-5.5 times higher in the adults than metacercariae, while CsGTP3 was transcribed 2.1 times higher in the metacercariae than adults. CsSGLT transcription was 163.6 times higher in adults than in metacercariae. In adults, CsSGLT was most abundant in the tegument; CsGTP3 and CsSGLT were localized in the vitelline gland, uterine wall, eggs, mesenchymal tissue, and testes; CsGTP4 was found in sperm and mesenchymal tissue; and CsGTP1 was mainly in the sperm and testes. In C. sinensis adults, exogenous glucose is imported in a short time and is present mainly in the middle and posterior body, in which the somatic and reproductive organs are located. Of the exogenous glucose, 53.6% was imported through CsSGLT and 46.4% through CsGTPs. Exogenous glucose import was effectively inhibited by cytochalasin B and phlorizin. CONCLUSIONS/SIGNIFICANCE We propose that CsSGLT cooperates with CsGTPs to import exogenous glucose from the environmental bile, transport glucose across mesenchymal tissue cells, and finally supply energy-demanding organs in C. sinensis adults. Studies on glucose transporters may pave the way for the development of new anthelmintic drugs.
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Affiliation(s)
- Fuhong Dai
- Department of Parasitology, School of Biology and Basic Medical Sciences, MOE Key Laboratory of Geriatric Diseases and Immunology, Suzhou Key Laboratory of Pathogen Bioscience and Anti-infective Medicine, Suzhou Medical College, Soochow University, Suzhou, China
- Department of Medical Sciences, Chung-Ang University College of Medicine, Seoul, Republic of Korea
| | - Soon-Ok Lee
- Department of Medical Sciences, Chung-Ang University College of Medicine, Seoul, Republic of Korea
- Department of Medical Zoology and Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, School of Medicine, Graduate School, Kyung Hee University, Seoul, Republic of Korea
| | - Jin-Ho Song
- Department of Pharmacology, Chung-Ang University College of Medicine, Seoul, Republic of Korea
| | - Won-Gi Yoo
- Department of Medical Sciences, Chung-Ang University College of Medicine, Seoul, Republic of Korea
- Laboratory of Veterinary Parasitology, College of Veterinary Medicine and Research Institute for Veterinary Science, Seoul National University, Seoul, Republic of Korea
| | - Eun-Hee Shin
- Department of Tropical Medicine and Parasitology, Seoul National University College of Medicine, and Institute of Endemic Diseases, Seoul, Republic of Korea
- Seoul National University Bundang Hospital, Seongnam, Republic of Korea
| | - Xuelian Bai
- Department of Medical Sciences, Chung-Ang University College of Medicine, Seoul, Republic of Korea
- Medical Research Center, Binzhou Medical University Hospital, Binzhou, China
| | - Sung-Jong Hong
- Department of Medical Sciences, Chung-Ang University College of Medicine, Seoul, Republic of Korea
- Center for Infectious Vectors and Diseases, Incheon National University, Incheon, Republic of Korea
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Identification of Structural Determinants of the Transport of the Dehydroascorbic Acid Mediated by Glucose Transport GLUT1. MOLECULES (BASEL, SWITZERLAND) 2023; 28:molecules28020521. [PMID: 36677580 PMCID: PMC9867014 DOI: 10.3390/molecules28020521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Revised: 12/12/2022] [Accepted: 12/28/2022] [Indexed: 01/06/2023]
Abstract
GLUT1 is a facilitative glucose transporter that can transport oxidized vitamin C (i.e., dehydroascorbic acid) and complements the action of reduced vitamin C transporters. To identify the residues involved in human GLUT1's transport of dehydroascorbic acid, we performed docking studies in the 5 Å grid of the glucose-binding cavity of GLUT1. The interactions of the bicyclic hemiacetal form of dehydroascorbic acid with GLUT1 through hydrogen bonds with the -OH group of C3 and C5 were less favorable than the interactions with the sugars transported by GLUT1. The eight most relevant residues in such interactions (i.e., F26, Q161, I164, Q282, Y292, and W412) were mutated to alanine to perform functional studies for dehydroascorbic acid and the glucose analog, 2-deoxiglucose, in Xenopus laevis oocytes. All the mutants decreased the uptake of both substrates to less than 50%. The partial effect of the N317A mutant in transporting dehydroascorbic acid was associated with a 30% decrease in the Vmax compared to the wildtype GLUT1. The results show that both substrates share the eight residues studied in GLUT1, albeit with a differential contribution of N317. Our work, combining docking with functional studies, marks the first to identify structural determinants of oxidized vitamin C's transport via GLUT1.
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Tilekar K, Upadhyay N, Hess JD, Macias LH, Mrowka P, Aguilera RJ, Meyer-Almes FJ, Iancu CV, Choe JY, Ramaa CS. Structure guided design and synthesis of furyl thiazolidinedione derivatives as inhibitors of GLUT 1 and GLUT 4, and evaluation of their anti-leukemic potential. Eur J Med Chem 2020; 202:112603. [PMID: 32634629 PMCID: PMC7451030 DOI: 10.1016/j.ejmech.2020.112603] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/14/2020] [Accepted: 06/18/2020] [Indexed: 12/24/2022]
Abstract
Cancer cells increase their glucose uptake and glycolytic activity to meet the high energy requirements of proliferation. Glucose transporters (GLUTs), which facilitate the transport of glucose and related hexoses across the cell membrane, play a vital role in tumor cell survival and are overexpressed in various cancers. GLUT1, the most overexpressed GLUT in many cancers, is emerging as a promising anti-cancer target. To develop GLUT1 inhibitors, we rationally designed, synthesized, structurally characterized, and biologically evaluated in-vitro and in-vivo a novel series of furyl-2-methylene thiazolidinediones (TZDs). Among 25 TZDs tested, F18 and F19 inhibited GLUT1 most potently (IC50 11.4 and 14.7 μM, respectively). F18 was equally selective for GLUT4 (IC50 6.8 μM), while F19 was specific for GLUT1 (IC50 152 μM in GLUT4). In-silico ligand docking studies showed that F18 interacted with conserved residues in GLUT1 and GLUT4, while F19 had slightly different interactions with the transporters. In in-vitro antiproliferative screening of leukemic/lymphoid cells, F18 was most lethal to CEM cells (CC50 of 1.7 μM). Flow cytometry analysis indicated that F18 arrested cell cycle growth in the subG0-G1 phase and lead to cell death due to necrosis and apoptosis. Western blot analysis exhibited alterations in cell signaling proteins, consistent with cell growth arrest and death. In-vivo xenograft study in a CEM model showed that F18 impaired tumor growth significantly.
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Affiliation(s)
- Kalpana Tilekar
- Department of Pharmaceutical Chemistry, Bharati Vidyapeeth's College of Pharmacy, Navi Mumbai, Maharashtra, India
| | - Neha Upadhyay
- Department of Pharmaceutical Chemistry, Bharati Vidyapeeth's College of Pharmacy, Navi Mumbai, Maharashtra, India
| | - Jessica D Hess
- The Cytometry, Screening and Imaging Core Facility & Border Biomedical Research Center & Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, USA
| | - Lucasantiago Henze Macias
- The Cytometry, Screening and Imaging Core Facility & Border Biomedical Research Center & Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, USA
| | - Piotr Mrowka
- Department of Biophysics and Human Physiology, Medical University of Warsaw, Chalubinskiego, Warsaw, Poland
| | - Renato J Aguilera
- The Cytometry, Screening and Imaging Core Facility & Border Biomedical Research Center & Department of Biological Sciences, The University of Texas at El Paso, El Paso, TX, USA
| | - Franz-Josef Meyer-Almes
- Department of Chemical Engineering and Biotechnology, University of Applied Sciences, Darmstadt, Germany
| | - Cristina V Iancu
- East Carolina Diabetes and Obesity Institute, Department of Chemistry, East Carolina University, Greenville, NC, USA
| | - Jun-Yong Choe
- East Carolina Diabetes and Obesity Institute, Department of Chemistry, East Carolina University, Greenville, NC, USA; Department of Biochemistry and Molecular Biology, The Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, USA.
| | - C S Ramaa
- Department of Pharmaceutical Chemistry, Bharati Vidyapeeth's College of Pharmacy, Navi Mumbai, Maharashtra, India.
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Pan Y, Zhang Y, Gongpan P, Zhang Q, Huang S, Wang B, Xu B, Shan Y, Xiong W, Li G, Wang H. Single glucose molecule transport process revealed by force tracing and molecular dynamics simulations. NANOSCALE HORIZONS 2018; 3:517-524. [PMID: 32254137 DOI: 10.1039/c8nh00056e] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Transporting individual molecules across cell membranes is a fundamental process in cellular metabolism. Although the crystal diffraction technique has greatly contributed to our understanding of the structures of the involved transporters, a description of the dynamic transport mechanism at the single-molecule level has been extremely elusive. In this study, we applied atomic force microscopy (AFM)-based force tracing to directly monitor the transport of a single molecule, d-glucose, across living cell membranes. Our results show that the force to transport a single molecule of d-glucose across cell membranes is 37 ± 9 pN, and the corresponding transport interval is approximately 20 ms, while the average speed is approximately 0.3 μm s-1. Furthermore, our calculated force profile from molecular dynamics simulations showed quantitatively good agreement with the force tracing observation and revealed detailed information regarding the glucose transport path, indicating that two salt bridges, K38/E299 and K300/E426, play critical roles during glucose transport across glucose transporter 1 (GLUT1). This role was further verified using biological experiments that disrupted these two bridges and measured the uptake of glucose into the cells. Our approaches led to the first unambiguous description of the glucose transport process across cell membranes at the single-molecule level and demonstrated the biological importance of the two salt bridges for transporting glucose across GLUT1.
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Affiliation(s)
- Yangang Pan
- State Key Laboratory of Electroanalytical Chemistry, Research Center of Biomembranomics, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, P. R. China.
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Jensen VF, Mølck AM, Lykkesfeldt J, Bøgh IB. Effect of maternal hypoglycaemia during gestation on materno-foetal nutrient transfer and embryo-foetal development: Evidence from experimental studies focused primarily on the rat. Reprod Toxicol 2018; 77:1-24. [DOI: 10.1016/j.reprotox.2018.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Revised: 12/07/2017] [Accepted: 01/30/2018] [Indexed: 01/14/2023]
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Musa MA, Wahab RA, Huyop F. Homology modelling and in silico substrate-binding analysis of a Rhizobium sp. RC1 haloalkanoic acid permease. BIOTECHNOL BIOTEC EQ 2018. [DOI: 10.1080/13102818.2018.1432417] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Affiliation(s)
- Muhammed Adamu Musa
- Department of Biotechnology and Medical Engineering, Faculty of Biosciences & Medical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
| | - Roswanira Abdul Wahab
- Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Johor, Malaysia
| | - Fahrul Huyop
- Department of Biotechnology and Medical Engineering, Faculty of Biosciences & Medical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia
- Biology Department, Faculty of Mathematics and Sciences, Universitas Negeri Semarang, Indonesia
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Stalin A, Irudayaraj SS, Gandhi GR, Balakrishna K, Ignacimuthu S, Al-Dhabi NA. Hypoglycemic activity of 6-bromoembelin and vilangin in high-fat diet fed-streptozotocin-induced type 2 diabetic rats and molecular docking studies. Life Sci 2016; 153:100-17. [PMID: 27091376 DOI: 10.1016/j.lfs.2016.04.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 04/06/2016] [Accepted: 04/13/2016] [Indexed: 12/14/2022]
Abstract
AIMS This paper investigates the hypoglycemic activity of two derivatives of embelin (1) viz. 6-bromoembelin (2) and vilangin (3), in high-fat diet - STZ induced diabetic rats. MAIN METHODS The effects of 6-bromoembelin (2) and vilangin (3) on insulin resistance, β-cell dysfunction and glucose transport in high-fat diet (HFD) fed-streptozotocin (STZ) (40mg/kg) induced type 2 diabetic rats were evaluated. The binding modes of 6-bromoembelin (2) and vilangin (3) into PPARγ, PI3K, Akt, and GLUT4 were also studied using Autodock 4.2 and ADT 1.5.6 programs. KEY FINDINGS At the dose of 30mg/kg, the plasma glucose, plasma insulin and body weight were reduced by both embelin derivatives in diabetic rats. Additionally the altered lipid profiles and hexokinase, glucose-6-phosphatase and fructose-1,6-bisphosphatase levels were brought to normal. Compared to diabetic control group, there was a significant increase in the expression of PPARγ in epididymal adipose tissue. Inhibition of adipogenic activity and mild activation of PPARγ levels in the skeletal muscle and liver were observed. In epididymal adipose tissue, the compounds increased the insulin-mediated glucose uptake through the activation and translocation of GLUT4 in PI3K/p-Akt signaling cascade. SIGNIFICANCE The derivatives of embelin such as 6-bromoembelin (2) and vilangin (3) may be useful in the prevention and treatment of obesity-linked type 2 diabetes mellitus.
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Affiliation(s)
- Antony Stalin
- Division of Bioinformatics, Entomology Research Institute, Loyola College, Chennai 600034, India
| | | | - Gopalsamy Rajiv Gandhi
- Division of Ethnopharmacology, Entomology Research Institute, Loyola College, Chennai 600034, India
| | - Kedike Balakrishna
- Division of Ethnopharmacology, Entomology Research Institute, Loyola College, Chennai 600034, India
| | - Savarimuthu Ignacimuthu
- Division of Bioinformatics, Entomology Research Institute, Loyola College, Chennai 600034, India; Division of Ethnopharmacology, Entomology Research Institute, Loyola College, Chennai 600034, India; Visiting professor program, Deanship of Scientific Research, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
| | - Naif Abdullah Al-Dhabi
- Department of Botany and Microbiology, Addiriyah Chair for Environmental Studies, College of Science, King Saud University, Post box 2455, Riyadh 11451, Saudi Arabia
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Park MS. Molecular Dynamics Simulations of the Human Glucose Transporter GLUT1. PLoS One 2015; 10:e0125361. [PMID: 25919356 PMCID: PMC4412407 DOI: 10.1371/journal.pone.0125361] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 03/12/2015] [Indexed: 01/31/2023] Open
Abstract
Glucose transporters (GLUTs) provide a pathway for glucose transport across membranes. Human GLUTs are implicated in devastating diseases such as heart disease, hyper- and hypo-glycemia, type 2 diabetes and cancer. The human GLUT1 has been recently crystalized in the inward-facing open conformation. However, there is no other structural information for other conformations. The X-ray structures of E. coli Xylose permease (XylE), a glucose transporter homolog, are available in multiple conformations with and without the substrates D-xylose and D-glucose. XylE has high sequence homology to human GLUT1 and key residues in the sugar-binding pocket are conserved. Here we construct a homology model for human GLUT1 based on the available XylE crystal structure in the partially occluded outward-facing conformation. A long unbiased all atom molecular dynamics simulation starting from the model can capture a new fully opened outward-facing conformation. Our investigation of molecular interactions at the interface between the transmembrane (TM) domains and the intracellular helices (ICH) domain in the outward- and inward-facing conformation supports that the ICH domain likely stabilizes the outward-facing conformation in GLUT1. Furthermore, inducing a conformational transition, our simulations manifest a global asymmetric rocker switch motion and detailed molecular interactions between the substrate and residues through the water-filled selective pore along a pathway from the extracellular to the intracellular side. The results presented here are consistent with previously published biochemical, mutagenesis and functional studies. Together, this study shed light on the structure and functional relationships of GLUT1 in multiple conformational states.
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Affiliation(s)
- Min-Sun Park
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia, United States of America
- * E-mail:
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Roy A, Dement AD, Cho KH, Kim JH. Assessing glucose uptake through the yeast hexose transporter 1 (Hxt1). PLoS One 2015; 10:e0121985. [PMID: 25816250 PMCID: PMC4376911 DOI: 10.1371/journal.pone.0121985] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 02/06/2015] [Indexed: 01/01/2023] Open
Abstract
The transport of glucose across the plasma membrane is mediated by members of the glucose transporter family. In this study, we investigated glucose uptake through the yeast hexose transporter 1 (Hxt1) by measuring incorporation of 2-NBDG, a non-metabolizable, fluorescent glucose analog, into the yeast Saccharomyces cerevisiae. We find that 2-NBDG is not incorporated into the hxt null strain lacking all glucose transporter genes and that this defect is rescued by expression of wild type Hxt1, but not of Hxt1 with mutations at the putative glucose-binding residues, inferred from the alignment of yeast and human glucose transporter sequences. Similarly, the growth defect of the hxt null strain on glucose is fully complemented by expression of wild type Hxt1, but not of the mutant Hxt1 proteins. Thus, 2-NBDG, like glucose, is likely to be transported into the yeast cells through the glucose transport system. Hxt1 is internalized and targeted to the vacuole for degradation in response to glucose starvation. Among the mutant Hxt1 proteins, Hxt1N370A and HXT1W473A are resistant to such degradation. Hxt1N370A, in particular, is able to neither uptake 2-NBDG nor restore the growth defect of the hxt null strain on glucose. These results demonstrate 2-NBDG as a fluorescent probe for glucose uptake in the yeast cells and identify N370 as a critical residue for the stability and function of Hxt1.
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Affiliation(s)
- Adhiraj Roy
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, NW, Washington, D. C., 20037, United States of America
| | - Angela D. Dement
- Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, 1015 Life Science Circle, Blacksburg, Virginia 24061, United States of America
| | - Kyu Hong Cho
- Department of Biology, Indiana State University, 200N 7th St, Terre Haute, Indiana 47809, United States of America
| | - Jeong-Ho Kim
- Department of Biochemistry and Molecular Medicine, The George Washington University School of Medicine and Health Science, 2300 Eye Street, NW, Washington, D. C., 20037, United States of America
- * E-mail:
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Huang ZB, Chen XZ, Qin LN, Wu HQ, Su XY, Dong ZY. A novel major facilitator transporter TrSTR1 is essential for pentose utilization and involved in xylanase induction in Trichoderma reesei. Biochem Biophys Res Commun 2015; 460:663-9. [PMID: 25817789 DOI: 10.1016/j.bbrc.2015.03.087] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 03/06/2015] [Indexed: 01/15/2023]
Abstract
Trichoderma reesei (teleomorph Hypocrea jecorina) is an industrially important filamentous fungus for glycoside hydrolases production, with its xylanolytic enzymes widely applied in many areas. However, the molecular mechanisms underlying xylanase expression are still insufficiently understood. In particular, the effect of sugar transporter on the induction of xylanase expression is unclear. In this work, we identified a novel major facilitator transporter TrSTR1 that is capable of transporting xylose by using a xylose utilization system in Saccharomyces cerevisiae. In T. reesei, TrSTR1 is essential for the utilization of d-xylose, l-arabinose, and even their downstream metabolites D-xylitol and L-arabitol. TrSTR1 is also involved in the induction of xylanase expression since both the xylanase activity and extracellular protein concentration in the Tu6△str1 strain were decreased, which further confirmed by a qRT-PCR analysis of the transcript levels of the key transcriptional regulators. Our observations provide new insights into connections between pentose utilization and xylanase production in T. reesei.
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Affiliation(s)
- Zhen-Bang Huang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Xiu-Zhen Chen
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
| | - Li-Na Qin
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
| | - Hong-Qing Wu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
| | - Xiao-Yun Su
- Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Zhi-Yang Dong
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
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Abstract
Soluble sugars serve five main purposes in multicellular organisms: as sources of carbon skeletons, osmolytes, signals, and transient energy storage and as transport molecules. Most sugars are derived from photosynthetic organisms, particularly plants. In multicellular organisms, some cells specialize in providing sugars to other cells (e.g., intestinal and liver cells in animals, photosynthetic cells in plants), whereas others depend completely on an external supply (e.g., brain cells, roots and seeds). This cellular exchange of sugars requires transport proteins to mediate uptake or release from cells or subcellular compartments. Thus, not surprisingly, sugar transport is critical for plants, animals, and humans. At present, three classes of eukaryotic sugar transporters have been characterized, namely the glucose transporters (GLUTs), sodium-glucose symporters (SGLTs), and SWEETs. This review presents the history and state of the art of sugar transporter research, covering genetics, biochemistry, and physiology-from their identification and characterization to their structure, function, and physiology. In humans, understanding sugar transport has therapeutic importance (e.g., addressing diabetes or limiting access of cancer cells to sugars), and in plants, these transporters are critical for crop yield and pathogen susceptibility.
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Affiliation(s)
- Li-Qing Chen
- Department of Plant Biology, Carnegie Institution for Science, Stanford, California 94305;
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Hresko RC, Kraft TE, Tzekov A, Wildman SA, Hruz PW. Isoform-selective inhibition of facilitative glucose transporters: elucidation of the molecular mechanism of HIV protease inhibitor binding. J Biol Chem 2014; 289:16100-13. [PMID: 24706759 DOI: 10.1074/jbc.m113.528430] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pharmacologic HIV protease inhibitors (PIs) and structurally related oligopeptides are known to reversibly bind and inactivate the insulin-responsive facilitative glucose transporter 4 (GLUT4). Several PIs exhibit isoform selectivity with little effect on GLUT1. The ability to target individual GLUT isoforms in an acute and reversible manner provides novel means both to investigate the contribution of individual GLUTs to health and disease and to develop targeted treatment of glucose-dependent diseases. To determine the molecular basis of transport inhibition, a series of chimeric proteins containing transmembrane and cytosolic domains from GLUT1 and GLUT4 and/or point mutations were generated and expressed in HEK293 cells. Structural integrity was confirmed via measurement of N-[2-[2-[2-[(N-biotinylcaproylamino)ethoxy)ethoxyl]-4-[2-(trifluoromethyl)-3H-diazirin-3-yl]benzoyl]-1,3-bis(mannopyranosyl-4-yloxy)-2-propylamine (ATB-BMPA) labeling of the chimeric proteins in low density microsome fractions isolated from stably transfected 293 cells. Functional integrity was assessed via measurement of zero-trans 2-deoxyglucose (2-DOG) uptake. ATB-BMPA labeling studies and 2-DOG uptake revealed that transmembrane helices 1 and 5 contain amino acid residues that influence inhibitor access to the transporter binding domain. Substitution of Thr-30 and His-160 in GLUT1 to the corresponding positions in GLUT4 is sufficient to completely transform GLUT1 into GLUT4 with respect to indinavir inhibition of 2-DOG uptake and ATB-BMPA binding. These data provide a structural basis for the selectivity of PIs toward GLUT4 over GLUT1 that can be used in ongoing novel drug design.
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Affiliation(s)
| | | | | | | | - Paul W Hruz
- From the Department of Pediatrics, Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110
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15
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Jensen VFH, Bøgh IB, Lykkesfeldt J. Effect of insulin-induced hypoglycaemia on the central nervous system: evidence from experimental studies. J Neuroendocrinol 2014; 26:123-50. [PMID: 24428753 DOI: 10.1111/jne.12133] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 12/13/2013] [Accepted: 01/08/2014] [Indexed: 12/12/2022]
Abstract
Insulin-induced hypoglycaemia (IIH) is a major acute complication in type 1 as well as in type 2 diabetes, particularly during intensive insulin therapy. The brain plays a central role in the counter-regulatory response by eliciting parasympathetic and sympathetic hormone responses to restore normoglycaemia. Brain glucose concentrations, being approximately 15-20% of the blood glucose concentration in humans, are rigorously maintained during hypoglycaemia through adaptions such as increased cerebral glucose transport, decreased cerebral glucose utilisation and, possibly, by using central nervous system glycogen as a glucose reserve. However, during sustained hypoglycaemia, the brain cannot maintain a sufficient glucose influx and, as the cerebral hypoglycaemia becomes severe, electroencephalogram changes, oxidative stress and regional neuronal death ensues. With particular focus on evidence from experimental studies on nondiabetic IIH, this review outlines the central mechanisms behind the counter-regulatory response to IIH, as well as cerebral adaption to avoid sequelae of cerebral neuroglycopaenia, including seizures and coma.
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Affiliation(s)
- V F H Jensen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Diabetes Toxicology and Safety Pharmacology, Novo Nordisk A/S, Maaloev, Denmark
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16
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Abstract
The Major Facilitator Superfamily (MFS) is a diverse group of secondary transporters with over 10,000 members, found in all kingdoms of life, including Homo sapiens. One objective of determining crystallographic models of the bacterial representatives is identification and physical localization of residues important for catalysis in transporters with medical relevance. The recently solved crystallographic models of the D-xylose permease XylE from Escherichia coli and GlcP from Staphylococcus epidermidus, homologs of the human D-glucose transporters, the GLUTs (SLC2), provide information about the structure of these transporters. The goal of this work is to examine general concepts derived from the bacterial XylE, GlcP, and other MFS transporters for their relevance to the GLUTs by comparing conservation of functionally critical residues. An energy landscape for symport and uniport is presented. Furthermore, the substrate selectivity of XylE is compared with GLUT1 and GLUT5, as well as a XylE mutant that transports D-glucose.
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17
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Abstract
Glucose transporters are required to bring glucose into cells, where it is an essential energy source and precursor in protein and lipid synthesis. These transporters are involved in important common diseases such as cancer and diabetes. Here, we report the crystal structure of the Staphylococcus epidermidis glucose/H(+) symporter in an inward-facing conformation at 3.2-Å resolution. The Staphylococcus epidermidis glucose/H(+) symporter is homologous to human glucose transporters, is very specific and has high avidity for glucose, and is inhibited by the human glucose transport inhibitors cytochalasin B, phloretin, and forskolin. On the basis of the crystal structure in conjunction with mutagenesis and functional studies, we propose a mechanism for glucose/H(+) symport and discuss the symport mechanism versus facilitated diffusion.
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18
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Mohan S S, Perry JJP, Poulose N, Nair BG, Anilkumar G. Homology modeling of GLUT4, an insulin regulated facilitated glucose transporter and docking studies with ATP and its inhibitors. J Biomol Struct Dyn 2013; 26:455-64. [PMID: 19108584 DOI: 10.1080/07391102.2009.10507260] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
GLUT4 is a 12 transmembrane (TM) protein belonging to the Class I facilitated glucose transporter family that transports glucose into the cells in an insulin regulated manner. GLUT4 plays a key role in the maintenance of blood glucose homeostasis and inhibition of glucose transporter activity may lead to insulin resistance, hallmark of type 2 diabetes. No crystal structure data is available for any members of the facilitated glucose transporter family. Here, in this paper, we have generated a homology model of GLUT4 based on experimental data available on GLUT1, a Class I facilitated glucose transporter and the crystal structure data obtained from the Glycerol 3-phosphate transporter. The model identified regions in GLUT4 that form a channel for the transport of glucose along with the substrate interacting residues. Docking and electrostatic potential data analysis of GLUT4 model has mapped an ATP binding region close to the binding site of cytochalasin B and genistein, two GLUT4 inhibitors, and this may explain the mechanism by which these inhibitors could potentially affect the GLUT4 function.
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Affiliation(s)
- Suma Mohan S
- School of Biotechnology, Amrita University, Kollam, Kerala 690525, India
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19
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Salas M, Obando P, Ojeda L, Ojeda P, Pérez A, Vargas-Uribe M, Rivas CI, Vera JC, Reyes AM. Resolution of the direct interaction with and inhibition of the human GLUT1 hexose transporter by resveratrol from its effect on glucose accumulation. Am J Physiol Cell Physiol 2013; 305:C90-9. [PMID: 23615963 DOI: 10.1152/ajpcell.00387.2012] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Resveratrol acts as a chemopreventive agent for cancer and as a potential antiobesity and antidiabetic compound, by leading to reduced body fat and improved glucose homeostasis. The exact mechanisms involved in improving hyperglycemic state are not known, but most of the glucose uptake into mammalian cells is facilitated by the GLUT hexose transporters. Resveratrol is structurally similar to isoflavones such as genistein, which inhibit the glucose uptake facilitated by the GLUT1 hexose transporter. Here we examined the direct effects of resveratrol on glucose uptake and accumulation in HL-60 and U-937 leukemic cell lines, which express mainly GLUT1, under conditions that discriminate transport from the intracellular substrate phosphorylation/accumulation. Resveratrol blocks GLUT1-mediated hexose uptake and thereby affects substrate accumulation on these cells. Consequently, we characterized the mechanism involved in inhibition of glucose uptake in human red cells. Resveratrol inhibits glucose exit in human red cells, and the displacement of previously bound cytochalasin B revealed the direct interaction of resveratrol with GLUT1. Resveratrol behaves as a competitive blocker of glucose uptake under zero-trans exit and exchange kinetic assays, but it becomes a mixed noncompetitive blocker when zero-trans entry transport was assayed, suggesting that the binding site for resveratrol lies on the endofacial face of the transporter. We propose that resveratrol interacts directly with the human GLUT1 hexose transporter by binding to an endofacial site and that this interaction inhibits the transport of hexoses across the plasma membrane. This inhibition is distinct from the effect of resveratrol on the intracellular phosphorylation/accumulation of glucose.
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Affiliation(s)
- Mónica Salas
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
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20
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Ligand-induced movements of inner transmembrane helices of Glut1 revealed by chemical cross-linking of di-cysteine mutants. PLoS One 2012; 7:e31412. [PMID: 22363641 PMCID: PMC3282689 DOI: 10.1371/journal.pone.0031412] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 01/10/2012] [Indexed: 11/19/2022] Open
Abstract
The relative orientation and proximity of the pseudo-symmetrical inner transmembrane helical pairs 5/8 and 2/11 of Glut1 were analyzed by chemical cross-linking of di-cysteine mutants. Thirteen functional di-cysteine mutants were created from a C-less Glut1 reporter construct containing cysteine substitutions in helices 5 and 8 or helices 2 and 11. The mutants were expressed in Xenopus oocytes and the sensitivity of each mutant to intramolecular cross-linking by two homobifunctional thiol-specific reagents was ascertained by protease cleavage followed by immunoblot analysis. Five of 9 mutants with cysteine residues predicted to lie in close proximity to each other were susceptible to cross-linking by one or both reagents. None of 4 mutants with cysteine substitutions predicted to lie on opposite faces of their respective helices was susceptible to cross-linking. Additionally, the cross-linking of a di-cysteine pair (A70C/M420C, helices 2/11) predicted to lie near the exoplasmic face of the membrane was stimulated by ethylidene glucose, a non-transported glucose analog that preferentially binds to the exofacial substrate-binding site, suggesting that the binding of this ligand stimulates the closure of helices at the exoplasmic face of the membrane. In contrast, the cross-linking of a second di-cysteine pair (T158C/L325, helices 5/8), predicted to lie near the cytoplasmic face of the membrane, was stimulated by cytochalasin B, a glucose transport inhibitor that competitively inhibits substrate efflux, suggesting that this compound recruits the transporter to a conformational state in which closure of inner helices occurs at the cytoplasmic face of the membrane. This observation provides a structural explanation for the competitive inhibition of substrate efflux by cytochalasin B. These data indicate that the binding of competitive inhibitors of glucose efflux or influx induce occluded states in the transporter in which substrate is excluded from the exofacial or endofacial binding site.
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21
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Yoshida A, Wei D, Nomura W, Izawa S, Inoue Y. Reduction of glucose uptake through inhibition of hexose transporters and enhancement of their endocytosis by methylglyoxal in Saccharomyces cerevisiae. J Biol Chem 2011; 287:701-711. [PMID: 22094464 DOI: 10.1074/jbc.m111.322222] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Diabetes mellitus is characterized by an impairment of glucose uptake even though blood glucose levels are increased. Methylglyoxal is derived from glycolysis and has been implicated in the development of diabetes mellitus, because methylglyoxal levels in blood and tissues are higher in diabetic patients than in healthy individuals. However, it remains to be elucidated whether such factors are a cause, or consequence, of diabetes. Here, we show that methylglyoxal inhibits the activity of mammalian glucose transporters using recombinant Saccharomyces cerevisiae cells genetically lacking all hexose transporters but carrying cDNA for human GLUT1 or rat GLUT4. We found that methylglyoxal inhibits yeast hexose transporters also. Glucose uptake was reduced in a stepwise manner following treatment with methylglyoxal, i.e. a rapid reduction within 5 min, followed by a slow and gradual reduction. The rapid reduction was due to the inhibitory effect of methylglyoxal on hexose transporters, whereas the slow and gradual reduction seemed due to endocytosis, which leads to a decrease in the amount of hexose transporters on the plasma membrane. We found that Rsp5, a HECT-type ubiquitin ligase, is responsible for the ubiquitination of hexose transporters. Intriguingly, Plc1 (phospholipase C) negatively regulated the endocytosis of hexose transporters in an Rsp5-dependent manner, although the methylglyoxal-induced endocytosis of hexose transporters occurred irrespective of Plc1. Meanwhile, the internalization of hexose transporters following treatment with methylglyoxal was delayed in a mutant defective in protein kinase C.
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Affiliation(s)
- Aya Yoshida
- Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Dandan Wei
- Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Wataru Nomura
- Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Shingo Izawa
- Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Yoshiharu Inoue
- Laboratory of Molecular Microbiology, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
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22
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Sheena A, Mohan SS, Haridas NPA, Anilkumar G. Elucidation of the glucose transport pathway in glucose transporter 4 via steered molecular dynamics simulations. PLoS One 2011; 6:e25747. [PMID: 22022441 PMCID: PMC3192114 DOI: 10.1371/journal.pone.0025747] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2011] [Accepted: 09/11/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND GLUT4 is a predominant insulin regulated glucose transporter expressed in major glucose disposal tissues such as adipocytes and muscles. Under the unstimulated state, GLUT4 resides within intracellular vesicles. Various stimuli such as insulin translocate this protein to the plasma membrane for glucose transport. In the absence of a crystal structure for GLUT4, very little is known about the mechanism of glucose transport by this protein. Earlier we proposed a homology model for GLUT4 and performed a conventional molecular dynamics study revealing the conformational rearrangements during glucose and ATP binding. However, this study could not explain the transport of glucose through the permeation tunnel. METHODOLOGY/PRINCIPAL FINDINGS To elucidate the molecular mechanism of glucose transport and its energetic, a steered molecular dynamics study (SMD) was used. Glucose was pulled from the extracellular end of GLUT4 to the cytoplasm along the pathway using constant velocity pulling method. We identified several key residues within the tunnel that interact directly with either the backbone ring or the hydroxyl groups of glucose. A rotation of glucose molecule was seen near the sugar binding site facilitating the sugar recognition process at the QLS binding site. CONCLUSIONS/SIGNIFICANCE This study proposes a possible glucose transport pathway and aids the identification of several residues that make direct interactions with glucose during glucose transport. Mutational studies are required to further validate the observation made in this study.
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Affiliation(s)
- Aswathy Sheena
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, India
| | - Suma S. Mohan
- Amrita School of Biotechnology, Amrita Vishwa Vidyapeetham, Kollam, India
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23
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Kasahara T, Shimogawara K, Kasahara M. Crucial effects of amino acid side chain length in transmembrane segment 5 on substrate affinity in yeast glucose transporter Hxt7. Biochemistry 2011; 50:8674-81. [PMID: 21892826 DOI: 10.1021/bi200958s] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
We previously identified Asp(340) in transmembrane segment 7 (TM7) as a key determinant of substrate affinity in Hxt7, a high-affinity facilitative glucose transporter of Saccharomyces cerevisiae. To gain further insight into the structural basis of substrate recognition by Hxt7, we performed cysteine-scanning mutagenesis of 21 residues in TM5 of a Cys-less form of Hxt7. Four residues were sensitive to Cys replacement, among which Gln(209) was found to be essential for high-affinity glucose transport activity. The 17 remaining sites were examined further for the accessibility of cysteine to the hydrophilic sulfhydryl reagent p-chloromercuribenzenesulfonate (pCMBS). Among the Cys mutants, T213C was the only one whose transport activity was completely inhibited by 0.5 mM pCMBS. Moreover, this mutant was protected from pCMBS inhibition by the substrate d-glucose and by 2-deoxy-D-glucose but not by L-glucose, indicating that Thr(213) is situated at or close to a substrate recognition site. The functional role of Thr(213) was further examined with its replacement with each of the other 19 amino acids in wild-type Hxt7. Such replacement generated seven functional transporters with various affinities for glucose. Only three mutants, those with Val, Cys, and Ser at position 213, exhibited high-affinity glucose transport activity. All of these residues possess a side chain length similar to that of Thr, indicating that side chain length at this position is a key determinant of substrate affinity. A working homology model of Hxt7 indicated that Gln(209) and Thr(213) face the central cavity and that Thr(213) is located within van der Waals distance of Asp(340) (TM7).
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Affiliation(s)
- Toshiko Kasahara
- Laboratory of Biophysics, School of Medicine, Teikyo University, Hachioji, Tokyo 192-0395, Japan.
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24
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Augustin R. The protein family of glucose transport facilitators: It's not only about glucose after all. IUBMB Life 2010; 62:315-33. [PMID: 20209635 DOI: 10.1002/iub.315] [Citation(s) in RCA: 187] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The protein family of facilitative glucose transporters comprises 14 isoforms that share common structural features such as 12 transmembrane domains, N- and C-termini facing the cytoplasm of the cell, and a N-glycosylation side either within the first or fifth extracellular loop. Based on their sequence homology, three classes can be distinguished: class I includes GLUT1-4 and GLUT14, class II the "odd transporters" GLUT5, 7, 9, 11, and class III the "even transporters" GLUT6, 8, 10, 12 and the proton driven myoinositol transporter HMIT (or GLUT13). With the cloning and characterization of the more recent class II and III isoforms, it became apparent that despite their structural similarities, the different isoforms not only show a distinct tissue-specific expression pattern but also show distinct characteristics such as alternative splicing, specific (sub)cellular localization, and affinities for a spectrum of substrates. This review summarizes the current understanding of the physiological role for the various transport facilitators based on human genetically inherited disorders or single-nucleotide polymorphisms and knockout mice models. The emphasis of the review will be on the potential functional role of the more recent isoforms.
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Affiliation(s)
- Robert Augustin
- Department of Cardiometabolic Diseases Research, Boehringer-Ingelheim Pharma GmbH&Co KG, Biberach a.d. Riss, Germany.
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25
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Price DRG, Tibbles K, Shigenobu S, Smertenko A, Russell CW, Douglas AE, Fitches E, Gatehouse AMR, Gatehouse JA. Sugar transporters of the major facilitator superfamily in aphids; from gene prediction to functional characterization. INSECT MOLECULAR BIOLOGY 2010; 19 Suppl 2:97-112. [PMID: 20482643 DOI: 10.1111/j.1365-2583.2009.00918.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Analysis of the pea aphid (Acyrthosiphon pisum) genome using signatures specific to the Major Facilitator Superfamily (Pfam Clan CL0015) and the Sugar_tr family (Pfam Family PF00083) has identified 54 genes encoding potential sugar transporters, of which 38 have corresponding ESTs. Twenty-nine genes contain the InterPro IPR003663 hexose transporter signature. The protein encoded by Ap_ST3, the most abundantly expressed sugar transporter gene, was functionally characterized by expression as a recombinant protein. Ap_ST3 acts as a low-affinity uniporter for fructose and glucose that does not depend on Na(+) or H(+) for activity. Ap_ST3 was expressed at elevated levels in distal gut tissue, consistent with a role in gut sugar transport. The A. pisum genome shows evidence of duplications of sugar transporter genes.
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26
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Amann T, Hellerbrand C. GLUT1 as a therapeutic target in hepatocellular carcinoma. Expert Opin Ther Targets 2010; 13:1411-27. [PMID: 19874261 DOI: 10.1517/14728220903307509] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Primary hepatocellular carcinoma (HCC) is one of the most fatal cancers in humans with rising incidence in many regions around the world. Currently, no satisfactory curative pharmacological treatment is available, and the outcome is mostly poor. Recently, we have shown that the glucose transporter GLUT1 is increased in a subset of patients with HCC and functionally affects tumorigenicity. GLUT1 is a rate-limiting transporter for glucose uptake, and its expression correlates with anaerobic glycolysis. This phenomenon is also known as the Warburg effect and recently became of great interest, since it affects not only glucose uptake and utilization but also has an influence on tumorigenic features like metastasis, chemoresistance and escape from immune surveillance. Consistent with this, RNA-interference-mediated inhibition of GLUT1 expression in HCC cells resulted in reduced tumorigenicity. Together, these findings indicate that GLUT1 is a novel and attractive therapeutic target for HCC. This review summarizes our current knowledge on the expression and function of GLUT1 in HCC, available drugs/strategies to inhibit GLUT1 expression or function, and potential side effects of such therapeutic strategies.
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Affiliation(s)
- Thomas Amann
- University Hospital Regensburg, Department of Internal Medicine I, D-93042 Regensburg, Germany
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27
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Kanamori Y, Saito A, Hagiwara-Komoda Y, Tanaka D, Mitsumasu K, Kikuta S, Watanabe M, Cornette R, Kikawada T, Okuda T. The trehalose transporter 1 gene sequence is conserved in insects and encodes proteins with different kinetic properties involved in trehalose import into peripheral tissues. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2010; 40:30-7. [PMID: 20035867 DOI: 10.1016/j.ibmb.2009.12.006] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 11/19/2009] [Accepted: 12/10/2009] [Indexed: 05/09/2023]
Abstract
We recently cloned a trehalose transporter gene (Tret1) that contributes to anhydrobiosis induction in the sleeping chironomid Polypedilum vanderplanki Hinton. Because trehalose is the main haemolymph sugar in most insects, they might possess Tret1 orthologs involved in maintaining haemolymph trehalose levels. We cloned Tret1 orthologs from four species in three insect orders. The similarities of the amino acid sequence to TRET1 in P. vanderplanki were 58.5-80.4%. Phylogenetic analysis suggested the Tret1 sequences were conserved in insects. The Xenopus oocyte expression system showed apparent differences in the K(m) and V(max) values for trehalose transport activity among the six proteins encoded by the corresponding orthologs. The TRET1 orthologs of Anopheles gambiae (K(m): 45.74 +/- 3.58 mM) and Bombyx mori (71.58 +/- 6.45 mM) showed low trehalose affinity, whereas those of Apis mellifera (9.42 +/- 2.37 mM) and Drosophila melanogaster (10.94 +/- 7.70 mM) showed high affinity. This difference in kinetics might be reflected in the haemolymph trehalose:glucose ratio of each species. Tret1 was expressed not only in the fat body but also in muscle and testis. These findings suggest that insect TRET1 is responsible for the release of trehalose from the fat body and the incorporation of trehalose into other tissues that require a carbon source, thereby regulating trehalose levels in the haemolymph.
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Affiliation(s)
- Yasushi Kanamori
- Anhydrobiosis Research Unit, National Institute of Agrobiological Sciences, Ohwashi 1-2, Tsukuba, Ibaraki 305-8634, Japan
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28
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Alisio A, Mueckler M. Purification and characterization of mammalian glucose transporters expressed in Pichia pastoris. Protein Expr Purif 2009; 70:81-7. [PMID: 19883765 DOI: 10.1016/j.pep.2009.10.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 10/20/2009] [Accepted: 10/23/2009] [Indexed: 10/20/2022]
Abstract
The major bottleneck to the application of high-resolution techniques such as crystallographic X-ray diffraction and spectroscopic analyses to resolve the structure of mammalian membrane proteins has been the ectopic expression and purification of sufficient quantities of non-denatured proteins. This has been especially problematic for members of the major facilitator superfamily, which includes the family of mammalian glucose transporters. A simple and rapid method is described for the purification of milligram quantities of recombinant GLUT1 and GLUT4, two of the most intensively studied GLUT isoforms, after ectopic expression in Pichia pastoris. The proteins obtained were >95% pure and exhibited functional transport and ligand-binding activities.
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Affiliation(s)
- Arturo Alisio
- Department of Cell Biology & Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
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29
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Mueckler M, Makepeace C. Model of the exofacial substrate-binding site and helical folding of the human Glut1 glucose transporter based on scanning mutagenesis. Biochemistry 2009; 48:5934-42. [PMID: 19449892 PMCID: PMC2776625 DOI: 10.1021/bi900521n] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transmembrane helix 9 of the Glut1 glucose transporter was analyzed by cysteine-scanning mutagenesis and the substituted cysteine accessibility method (SCAM). A cysteine-less (C-less) template transporter containing amino acid substitutions for the six native cysteine residues present in human Glut1 was used to generate a series of 21 mutant transporters by substituting each successive residue in predicted transmembrane segment 9 with a cysteine residue. The mutant proteins were expressed in Xenopus oocytes, and their specific transport activities were directly compared to that of the parental C-less molecule whose function has been shown to be indistinguishable from that of native Glut1. Only a single mutant (G340C) had activity that was reduced (by 75%) relative to that of the C-less parent. These data suggest that none of the amino acid side chains in helix 9 is absolutely required for transport function and that this helix is not likely to be directly involved in substrate binding or translocation. Transport activity of the cysteine mutants was also tested after incubation of oocytes in the presence of the impermeant sulfhydryl-specific reagent, p-chloromercuribenzene sulfonate (pCMBS). Only a single mutant (T352C) exhibited transport inhibition in the presence of pCMBS, and the extent of inhibition was minimal (11%), indicating that only a very small portion of helix 9 is accessible to the external solvent. These results are consistent with the conclusion that helix 9 plays an outer stabilizing role for the inner helical bundle predicted to form the exofacial substrate-binding site. All 12 of the predicted transmembrane segments of Glut1 encompassing 252 amino acid residues and more than 50% of the complete polypeptide sequence have now been analyzed by scanning mutagenesis and SCAM. An updated model is presented for the outward-facing substrate-binding site and relative orientation of the 12 transmembrane helices of Glut1.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110, USA.
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30
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Myronovych A, Murata S, Chiba M, Matsuo R, Ikeda O, Watanabe M, Hisakura K, Nakano Y, Kohno K, Kawasaki T, Hashimoto I, Shibasaki Y, Yasue H, Ohkohchi N. Role of platelets on liver regeneration after 90% hepatectomy in mice. J Hepatol 2008; 49:363-72. [PMID: 18602717 DOI: 10.1016/j.jhep.2008.04.019] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 04/17/2008] [Accepted: 04/17/2008] [Indexed: 02/07/2023]
Abstract
BACKGROUND/AIMS Mortality after 90% partial hepatectomy in mice was associated with severe acute liver failure. Recently, we revealed that platelets have a strong promotional effect on hepatic regeneration. In the present study, we investigated the effect of thrombocytosis on liver regeneration after 90% hepatectomy in mice. METHODS For thrombocytosis induction PEG-rHuMGDF was injected 5 days before operation. Hepatectomy, sparing only the caudate lobe, was performed in normal and thrombocytotic BALB/c mice. Survival rate, platelet number, liver weight/body weight ratio, proliferating cell nuclear antigen, serum parameters, signal transduction and overexpressed genes were examined. RESULTS Platelet number was significantly higher in thrombocytotic group. All mice in normal group died within 30 h after hepatectomy. Survival rate in thrombocytotic group was 6/11 at 30 h and 3/11 one week after hepatectomy. Activation of Akt and STAT3 signaling pathways in thrombocytotic group was observed earlier and recognized to be stronger compared to normal group. Cell cycle, signaling pathways, metabolism and transport genes were significantly overexpressed in thrombocytotic group up to 24h after hepatectomy. CONCLUSIONS Under the thrombocytotic condition, liver regeneration occurred even in 90% hepatectomized mice. Platelets contribute to cell cycle progression and metabolic pathways in addition to preventing acute liver failure.
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Affiliation(s)
- Andriy Myronovych
- Department of Surgery, Advanced Biomedical Applications, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan
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31
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Mueckler M, Makepeace C. Transmembrane segment 6 of the Glut1 glucose transporter is an outer helix and contains amino acid side chains essential for transport activity. J Biol Chem 2008; 283:11550-5. [PMID: 18245775 PMCID: PMC2431073 DOI: 10.1074/jbc.m708896200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Revised: 01/29/2008] [Indexed: 11/06/2022] Open
Abstract
Experimental data and homology modeling suggest a structure for the exofacial configuration of the Glut1 glucose transporter in which 8 transmembrane helices form an aqueous cavity in the bilayer that is stabilized by four outer helices. The role of transmembrane segment 6, predicted to be an outer helix in this model, was examined by cysteine-scanning mutagenesis and the substituted cysteine accessibility method using the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzene-sulfonate (pCMBS). A fully functional Glut1 molecule lacking all 6 native cysteine residues was used as a template to produce a series of 21 Glut1 point mutants in which each residue along helix 6 was individually changed to cysteine. These mutants were expressed in Xenopus oocytes, and their expression levels, functional activities, and sensitivities to inhibition by pCMBS were determined. Cysteine substitutions at Leu(204) and Pro(205) abolished transport activity, whereas substitutions at Ile(192), Pro(196), Gln(200), and Gly(201) resulted in inhibition of activity that ranged from approximately 35 to approximately 80%. Cysteine substitutions at Leu(188), Ser(191), and Leu(199) moderately augmented specific transport activity relative to the control. These results were dramatically different from those previously reported for helix 12, the structural cognate of helix 6 in the pseudo-symmetrical structural model, for which none of the 21 single-cysteine mutants exhibited reduced activity. Only the substitution at Leu(188) conferred inhibition by pCMBS, suggesting that most of helix 6 is not exposed to the external solvent, consistent with its proposed role as an outer helix. These data suggest that helix 6 contains amino acid side chains that are critical for transport activity and that structurally analogous outer helices may play distinct roles in the function of membrane transporters.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, 63110, USA.
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Patel AP, Staines HM, Krishna S. New antimalarial targets: the example of glucose transport. Travel Med Infect Dis 2008; 6:58-66. [PMID: 18342277 DOI: 10.1016/j.tmaid.2008.01.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Accepted: 01/10/2008] [Indexed: 11/19/2022]
Abstract
In order for a novel drug target to attract attention it must be shown to be essential for parasite survival. In addition, it is desirable that a novel target provides some molecular and functional basis for the development of selective inhibitors. In this respect the pathway for transport of glucose to the parasite in Plasmodium falciparum has attracted increasing interest as a target for antimalarial chemotherapy. In particular, the plasmodial hexose transporter, PfHT, known to mediate transport of this essential substrate to the parasite has been a promising candidate for development of inhibitors. The article summarises the steps involved in development of this parasite protein as a drug target. Details of PfHT identification, functional characterisation and its validation as a drug target by using a selective inhibitor are discussed. The potential use of a robust system to screen libraries of compounds in a high-throughput format, in pursuit of an inhibitor of PfHT is also described. In conclusion PfHT represents one example of a rational approach in the drug discovery process to structure-base design of drugs.
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Affiliation(s)
- Asha Parbhu Patel
- Centre for Infection, Division of Cellular and Molecular Medicine, St. George's, University of London, Cranmer Terrace, London SW17 0RE, UK.
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Price DRG, Wilkinson HS, Gatehouse JA. Functional expression and characterisation of a gut facilitative glucose transporter, NlHT1, from the phloem-feeding insect Nilaparvata lugens (rice brown planthopper). INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2007; 37:1138-1148. [PMID: 17916500 DOI: 10.1016/j.ibmb.2007.07.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2006] [Revised: 06/29/2007] [Accepted: 07/03/2007] [Indexed: 05/25/2023]
Abstract
Phloem-sap feeding Hemipteran insects have access to a sucrose-rich diet but are dependent on sucrose hydrolysis and hexose transport for carbon nutrition. A cDNA library from Nilaparvata lugens (rice brown planthopper) was screened for clones encoding potential transmembrane transporters. A selected cDNA, NlHT1, encodes a 53kDa polypeptide with sequence similarity to facilitative hexose transporters of eukaryotes and prokaryotes, including GLUT1, the human erythrocyte hexose transporter. NlHT1 was expressed as a recombinant protein in the methylotropic yeast Pichia pastoris, and was identified in a membrane fraction isolated from transformed yeast cells. Transport experiments using membrane vesicles containing NlHT1 showed that the protein is a saturable, sodium independent transporter, with a relatively low affinity for glucose (K(m) 3.0mM), which can be inhibited by cytochalasin B. Competition experiments with fructose demonstrate NlHT1 is glucose specific. In situ localisation studies revealed that NlHT1 mRNA is expressed in N. lugens gut tissue, mainly in midgut regions, and that expression is absent in hindgut and Malpighian tubules. NlHT1 is therefore likely to play an important role in glucose transport from the gut, and in carbon nutrition in vivo. This is the first report of a facilitative glucose transporter from a phloem-feeding insect pest.
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Affiliation(s)
- Daniel R G Price
- School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, UK.
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Mueckler M, Makepeace C. Transmembrane segment 12 of the Glut1 glucose transporter is an outer helix and is not directly involved in the transport mechanism. J Biol Chem 2006; 281:36993-8. [PMID: 17020877 DOI: 10.1074/jbc.m608158200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
A model has been proposed for the exofacial configuration of the Glut1 glucose transporter in which eight transmembrane domains form an inner helical bundle stabilized by four outer helices. The role of transmembrane segment 12, predicted to be an outer helix in this hypothetical model, was examined by cysteine-scanning mutagenesis and the substituted cysteine accessibility method using the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). A previously characterized functional cysteine-less Glut1 molecule was used to produce 21 Glut1 point mutants by changing each residue along helix 12 to a cysteine residue. These mutants were then expressed in Xenopus oocytes, and their protein levels, functional activities, and sensitivities to pCMBS were determined. Strikingly, in contrast to all nine other predicted Glut1 transmembrane helices that have been previously examined by this method, none of the 21 helix 12 single-cysteine mutants exhibited significant inhibition of specific transport activity. Also unlike most other Glut1 transmembrane domains in which solvent-accessible residues lie along a single face of the helix, mutations in five consecutive residues predicted to lie close to the exofacial face of the membrane resulted in sensitivity to pCMBS-induced transport inhibition. These results suggest that helix 12 plays a passive stabilizing role in the structure of Glut1 and is not directly involved in the transport mechanism. Additionally, the pCMBS data indicate that the predicted exoplasmic end of helix 12 is completely exposed to the external solvent when the transporter is in its exofacial configuration.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Forment JV, Flipphi M, Ramón D, Ventura L, Maccabe AP. Identification of the mstE gene encoding a glucose-inducible, low affinity glucose transporter in Aspergillus nidulans. J Biol Chem 2006; 281:8339-46. [PMID: 16418173 DOI: 10.1074/jbc.m508198200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mstE gene encoding a low affinity glucose transporter active during the germination of Aspergillus nidulans conidia on glucose medium has been identified. mstE expression also occurs in hyphae, is induced in the presence of other repressing carbon sources besides glucose, and is dependent on the function of the transcriptional repressor CreA. The expression of MstE and its subcellular distribution have been studied using a MstE-sGFP fusion protein. Concordant with data on mstE expression, MstE-sGFP is synthesized in the presence of repressing carbon sources, and fluorescence at the periphery of conidia and hyphae is consistent with MstE location in the plasma membrane. Deletion of mstE has no morphological phenotype but results in the absence of low affinity glucose uptake kinetics, the latter being substituted by a high affinity system.
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Affiliation(s)
- Josep V Forment
- Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas, Apartado de Correos 73, Burjassot, 46100 Valencia, Spain
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Mueckler M, Makepeace C. Cysteine-scanning Mutagenesis and Substituted Cysteine Accessibility Analysis of Transmembrane Segment 4 of the Glut1 Glucose Transporter. J Biol Chem 2005; 280:39562-8. [PMID: 16172126 DOI: 10.1074/jbc.m509050200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A low resolution model has been proposed for the exofacial conformation of the Glut1 glucose transporter in which eight transmembrane segments form an inner helical bundle stabilized by four outer helices. The role of transmembrane segment 4, predicted to be an inner helix in this structural model, was investigated by cysteine-scanning mutagenesis in conjunction with the substituted cysteine accessibility method using the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). A functional, cysteine-less, parental Glut1 molecule was used to produce 21 Glut1 point mutants by individually changing each residue along transmembrane helix 4 to a cysteine. The single cysteine mutants were then expressed in Xenopus oocytes, and their expression levels, transport activities, and sensitivities to pCMBS were determined. In striking contrast to all of the other seven predicted inner helices, none of the 21 helix 4 single-cysteine mutants was demonstrably inhibited by pCMBS. However, cysteine substitution within helix 4 resulted in an unusually high number of severely transport-defective mutants. The low absolute transport activities of two of these mutants (G130C and G134C) were due to their extremely low levels of expression, presumably a result of structural instability and consequent degradation in oocytes, suggesting that these two residues play an important role in maintaining the native structure of Glut1. The other two transport-defective mutants (Y143C and E146C) exhibited low specific transport activities, implying that these two residues play an important role in the transport cycle. Based on these data, we conclude that the exoplasmic end of helix 4 lies outside the inner helical bundle in the exofacial configuration of Glut1.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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37
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Manolescu A, Salas-Burgos AM, Fischbarg J, Cheeseman CI. Identification of a hydrophobic residue as a key determinant of fructose transport by the facilitative hexose transporter SLC2A7 (GLUT7). J Biol Chem 2005; 280:42978-83. [PMID: 16186102 DOI: 10.1074/jbc.m508678200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Until recently, the only facilitated hexose transporter GLUT proteins (SLC2A) known to transport fructose were GLUTs 2 and 5. However, the recently cloned GLUT7 can also transport fructose as well as glucose. Comparison of sequence alignments indicated that GLUTs 2, 5, and 7 all had an isoleucine residue at position "314" (GLUT7), whereas the non-fructose-transporting isoforms, GLUTs 1, 3, and 4, had a valine at this position. Mutation of Ile-314 to a valine in GLUT7 resulted in a loss of fructose transport, whereas glucose transport remained completely unaffected. Similar results were obtained with GLUTs 2 and 5. Energy minimization modeling of GLUT7 indicated that Ile-314 projects from transmembrane domain 7 (TM7) into the lumen of the aqueous pore, where it could form a hydrophobic interaction with tryptophan 89 from TM2. A valine residue at 314 appeared to produce a narrowing of the vestibule when compared with the isoleucine. It is proposed that this hydrophobic interaction across the pore forms a selectivity filter restricting the access of some hexoses to the substrate binding site(s) within the aqueous channel. The presence of a selectivity filter in the extracellular vestibule of GLUT proteins would allow for subtle changes in substrate specificity without changing the kinetic parameters of the protein.
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MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites
- Biological Transport
- Blotting, Western
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Fructose/chemistry
- Fructose/metabolism
- Glucose/chemistry
- Glucose Transport Proteins, Facilitative/chemistry
- Glucose Transport Proteins, Facilitative/metabolism
- Hexoses/chemistry
- Hexoses/metabolism
- Humans
- Immunohistochemistry
- Isoleucine/chemistry
- Kinetics
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Oocytes/metabolism
- Protein Binding
- Protein Conformation
- Protein Isoforms
- Protein Structure, Secondary
- Protein Transport
- RNA, Complementary/metabolism
- Sequence Homology, Amino Acid
- Substrate Specificity
- Valine/chemistry
- Xenopus
- Xenopus laevis
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Affiliation(s)
- Andrei Manolescu
- Department of Physiology, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
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Salas-Burgos A, Iserovich P, Zuniga F, Vera JC, Fischbarg J. Predicting the three-dimensional structure of the human facilitative glucose transporter glut1 by a novel evolutionary homology strategy: insights on the molecular mechanism of substrate migration, and binding sites for glucose and inhibitory molecules. Biophys J 2004; 87:2990-9. [PMID: 15326030 PMCID: PMC1304772 DOI: 10.1529/biophysj.104.047886] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Accepted: 08/09/2004] [Indexed: 12/13/2022] Open
Abstract
The glucose transporters (GLUT/SLC2A) are members of the major facilitator superfamily. Here, we generated a three-dimensional model for Glut1 using a two-step strategy: 1), GlpT structure as an initial homology template and 2), evolutionary homology using glucose-6-phosphate translocase as a template. The resulting structure (PDB No. 1SUK) exhibits a water-filled passageway communicating the extracellular and intracellular domains, with a funnel-like exofacial vestibule (infundibulum), followed by a 15 A-long x 8 A-wide channel, and a horn-shaped endofacial vestibule. Most residues which, by mutagenesis, are crucial for transport delimit the channel, and putative sugar recognition motifs (QLS, QLG) border both ends of the channel. On the outside of the structure there are two positively charged cavities (one exofacial, one endofacial) delimited by ATP-binding Walker motifs, and an exofacial large side cavity of yet unknown function. Docking sites were found for the glucose substrate and its inhibitors: glucose, forskolin, and phloretin at the exofacial infundibulum; forskolin, and phloretin at an endofacial site next to the channel opening; and cytochalasin B at a positively charged endofacial pocket 3 A away from the channel. Thus, 1SUK accounts for practically all biochemical and mutagenesis evidence, and provides clues for the transport process.
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Affiliation(s)
- Alexis Salas-Burgos
- Department of Ophthalmology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
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39
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Mueckler M, Roach W, Makepeace C. Transmembrane segment 3 of the Glut1 glucose transporter is an outer helix. J Biol Chem 2004; 279:46876-81. [PMID: 15308632 DOI: 10.1074/jbc.m408632200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A model has been proposed for the structure of the Glut1 glucose transporter based on the results of mutagenesis studies and homology modeling in which eight transmembrane segments form an inner helical bundle surrounded by four outer helices. The role of transmembrane segment 3 in this structural model was investigated using cysteine-scanning mutagenesis in conjunction with the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). Twenty-one Glut1 mutants were created from a fully functional, cysteine-less, parental Glut1 molecule by successively changing each residue along transmembrane helix 3 to a cysteine. The single cysteine mutants were then expressed in Xenopus oocytes, and their expression levels, transport activities, and sensitivities to pCMBS were determined. Cysteine substitution at methionine 96 abolished transport activity, whereas substitutions at the other positions resulted in either modest reductions or no significant effect on transport activity. In striking contrast to all other helices that have been examined to date, only one of the 21 helix 3 single-cysteine mutants was inhibited by pCMBS, suggesting that only a small portion of this helix is exposed to the external solvent. This result is consistent with predictions based on our current structural model, in which helix 3 is one of four outer helices that surround the inner helical bundle that comprises the aqueous substrate-binding cavity. An updated two-dimensional model for the orientation of the 12 transmembrane helices and the conformation of the exofacial glucose-binding site of Glut1 is presented that is consistent with existing experimental data.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Alisio A, Mueckler M. Relative Proximity and Orientation of Helices 4 and 8 of the GLUT1 Glucose Transporter. J Biol Chem 2004; 279:26540-5. [PMID: 15073187 DOI: 10.1074/jbc.m402303200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A structure has been proposed for glucose transporter-1 (GLUT1) based upon homology modeling that is consistent with the results of numerous mutagenesis studies (Mueckler, M., and Makepeace, C. (2004) J. Biol. Chem. 279, 10494-10499). To further test and refine this model, the relative orientation and proximity of transmembrane helices 4 and 8 were analyzed by chemical crosslinking of di-cysteine mutants created in a reporter GLUT1 construct. All six native cysteine residues of GLUT1 were changed to either glycine or serine residues by site-directed mutagenesis, resulting in a functional Glut1 construct with Cys mutated to Gly/Ser (C-less). The GLUT1 reporter molecule was engineered from C-less GLUT1 by creating a unique cleavage site for factor Xa protease within the central cytoplasmic loop and by eliminating the site of N-linked glycosylation. Fourteen functional di-cysteine mutants were then created from the C-less reporter construct, each mutant containing a single cysteine residue in helix 4 and one cysteine residue in helix 8. These mutants were expressed in Xenopus oocytes, and the sensitivity of each mutant to intramolecular crosslinking by two homo-bifunctional, thiol-specific crosslinking reagents, bismaleimidehexane and 1,4-phenylenedimaleimide, was ascertained by protease cleavage followed by immunoblot analysis. Four pairs of cysteine residues, Cys(148)/Cys(328), Cys(145)/Cys(328), Cys(148)/Cys(325), and Cys(145)/Cys(325), were observed to be in close enough proximity to be susceptible to crosslinking by one or both reagents. All five of the cysteine residues susceptible to crosslinking are predicted to lie on the same face of helix 4 or 8 and to reside close to the cytoplasmic face of the membrane. These data indicate that the cytoplasmic ends of helices 4 and 8 lie within 6-16 A of one another and that the two helices twist or tilt such that they are further than 16 A apart toward the center and the exoplasmic side of the membrane. An updated model for the clustering of the transmembrane helices of GLUT1 is presented based on these data.
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Affiliation(s)
- Arturo Alisio
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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41
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Mueckler M, Makepeace C. Analysis of transmembrane segment 8 of the GLUT1 glucose transporter by cysteine-scanning mutagenesis and substituted cysteine accessibility. J Biol Chem 2003; 279:10494-9. [PMID: 14688257 DOI: 10.1074/jbc.m310786200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The GLUT1 glucose transporter has been proposed to form an aqueous substrate translocation pathway via the clustering of several amphipathic transmembrane helices (Mueckler, M., Caruso, C., Baldwin, S. A., Panico, M., Blench, I., Morris, H. R., Allard, W. J., Lienhard, G. E., and Lodish, H. F. (1985) Science 229, 941-945). The possible role of transmembrane helix 8 in the formation of this permeation pathway was investigated using cysteine-scanning mutagenesis and the membrane-impermeant sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). Twenty-one GLUT1 mutants were created from a fully functional cysteine-less parental GLUT1 molecule by successively changing each residue along transmembrane segment 8 to a cysteine. The mutant proteins were then expressed in Xenopus oocytes, and their membrane concentrations, 2-deoxyglucose uptake activities, and sensitivities to pCMBS were determined. Four positions within helix 8, alanine 309, threonine 310, serine 313, and glycine 314, were accessible to pCMBS as judged by the inhibition of transport activity. All four of these residues are clustered along one face of a putative alpha-helix. These results suggest that transmembrane segment 8 of GLUT1 forms part of the sugar permeation pathway. Updated two-dimensional models for the orientation of the 12 transmembrane helices and the conformation of the exofacial glucose binding site of GLUT1 are proposed that are consistent with existing experimental data and homology modeling based on the crystal structures of two bacterial membrane transporters.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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42
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Manning SK, Woodrow C, Zuniga FA, Iserovich P, Fischbarg J, Louw AI, Krishna S. Mutational analysis of the hexose transporter of Plasmodium falciparum and development of a three-dimensional model. J Biol Chem 2002; 277:30942-9. [PMID: 12042321 DOI: 10.1074/jbc.m204337200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plasmodium falciparum infection kills more than 1 million children annually. Novel drug targets are urgently being sought as multidrug resistance limits the range of treatment options for this protozoan pathogen. PfHT1, the major hexose transporter of P. falciparum is a promising new target. We report detailed structure-function studies on PfHT1 using site-directed mutagenesis approaches on residues located in helix V (Q169N) and helix VII ((302)SGL --> AGT). Studies with hexose analogues in these mutants have established that hexose recognition and permeation are intimately linked to these helices. A "fructose filter" effect results from the Q169N mutation (abolishing fructose uptake but preserving affinity and transport of glucose, as reported in Woodrow, C. J., Burchmore, R. J. S., and Krishna, S. (2000) Proc. Natl. Acad. Sci. U. S. A. 97, 9931-9936). Associated changes in competition for glucose uptake by C-2, C-3, and C-6 glucose analogues compared with native PfHT1 indicate subtle alterations in substrate interaction in this mutant. The K(m) values for glucose uptake in helix VII mutants are also similar to native PfHT1. Hydrogen bonding to positions C-5 and C-6 in glucose analogues becomes relatively more important in these mutants compared with native PfHT1. To increase understanding of hexose permeation pathways in PfHT1, we have developed the first three-dimensional model for PfHT1. As predicted for GLUT1, the principal mammalian glucose transporter, PfHT1 contains a main and an auxiliary channel. After modeling, the Q169N mutation leads predominantly to local structural changes, including displacement of neighboring helix IV. The (302)SGL position in helix VII lies in the same plane as Gln-169 in helix V but is also adjacent to the main hexose permeation pathway, consistent with results from experiments mutating this triplet motif. Furthermore, there are obvious structural and functional differences between GLUT1 and PfHT1 that can now be explored in detail using the approaches presented here. The development of specific inhibitors for PfHT1 will also be aided by these insights.
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Affiliation(s)
- Suzanne K Manning
- Department of Biochemistry, University of Pretoria, Pretoria 0002, South Africa
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43
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Mueckler M, Makepeace C. Analysis of transmembrane segment 10 of the Glut1 glucose transporter by cysteine-scanning mutagenesis and substituted cysteine accessibility. J Biol Chem 2002; 277:3498-503. [PMID: 11713254 DOI: 10.1074/jbc.m109157200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Glut1 glucose transporter has been proposed to form an aqueous sugar translocation pathway through the lipid bilayer via the clustering of several transmembrane helices (Mueckler, M., Caruso, C., Baldwin, S. A., Panico, M., Blench, I., Morris, H. R., Allard, W. J., Lienhard, G. E., and Lodish, H. F. (1985) Science 229, 941-945). The participation of transmembrane helix 10 in the formation of this putative aqueous tunnel was tested using cysteine-scanning mutagenesis in conjunction with the membrane-impermeant, sulfhydryl-specific reagent, p-chloromercuribenzenesulfonate (pCMBS). A series of 21 mutants was created from a fully functional, cysteine-less, parental Glut1 molecule by changing each residue within putative transmembrane segment 10 to cysteine. Each mutant was then expressed in Xenopus oocytes, and its plasma membrane content, 2-deoxyglucose uptake activity, and sensitivity to pCMBS were measured. Helix 10 exhibited a highly distinctive reaction profile to scanning mutagenesis whereby cysteine substitution at residues within the cytoplasmic N-terminal half of the helix tended to increase specific transport activity, whereas substitution at residues within the exoplasmic C-terminal half of the helix tended to decrease specific transport activity. Four residues within helix 10 were clearly accessible to pCMBS as judged by inhibition or stimulation of transport activity. All four of these residues were clustered along one face of a putative alpha-helix. These results combined with previously published data suggest that transmembrane segment 10 of Glut1 forms part of the sugar permeation pathway. Two-dimensional models for the conformation of the 12 transmembrane helices and the exofacial glucose-binding site of Glut1 are proposed that are consistent with existing experimental data.
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Affiliation(s)
- Mike Mueckler
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Sasaki T, Minoshima S, Shiohama A, Shintani A, Shimizu A, Asakawa S, Kawasaki K, Shimizu N. Molecular cloning of a member of the facilitative glucose transporter gene family GLUT11 (SLC2A11) and identification of transcription variants. Biochem Biophys Res Commun 2001; 289:1218-24. [PMID: 11741323 DOI: 10.1006/bbrc.2001.6101] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We isolated a member of the facilitative glucose transporter (GLUT) gene family (GLUT11; SLC2A11 as a HGMW-approved symbol) based on the analysis of a human genomic BAC clone KB1125A3 located on band q11.2 of human chromosome 22. The gene GLUT11/SLC2A11 consists of 12 exons spanning over 29 kb in size and is located between two genes, SMARCB1 and MIF. The deduced amino acid sequence indicated the topological features of transmembrane helices and sequence motifs which are common to the GLUT protein family. The cDNA cloning revealed the presence of three types of variation in its transcripts. The first variation is caused by the existence of three distinct first exons (SLC2A11-a, -b, and -c). PCR analysis of multi-tissue-derived cDNA panels indicated the differential expression of these transcript variants. The second variation is caused by skipping over one exon (exon 6). The third variation is caused by the premature transcription termination at a site between exon 8 and exon 9. Both exon skipping and premature termination caused frameshift, resulting in the production of truncated GLUT11/SLC2A11 transcripts. These results suggested that transcription of GLUT11/SCL2A11 gene is controlled in a complex manner.
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Affiliation(s)
- T Sasaki
- Department of Molecular Biology, Keio University School of Medicine, Tokyo, Japan
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Klip A, Marette A. Regulation of Glucose Transporters by Insulin and Exercise: Cellular Effects and Implications for Diabetes. Compr Physiol 2001. [DOI: 10.1002/cphy.cp070214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Zuniga FA, Shi G, Haller JF, Rubashkin A, Flynn DR, Iserovich P, Fischbarg J. A three-dimensional model of the human facilitative glucose transporter Glut1. J Biol Chem 2001; 276:44970-5. [PMID: 11571301 DOI: 10.1074/jbc.m107350200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The human facilitative transporter Glut1 is the major glucose transporter present in all human cells, has a central role in metabolism, and is an archetype of the superfamily of major protein facilitators. Here we describe a three-dimensional structure of Glut1 based on helical packing schemes proposed for lactose permease and Glut1 and predictions of secondary structure, and refined using energy minimization, molecular dynamics simulations, and quality and environmental scores. The Ramachandran scores and the stereochemical quality of the structure obtained were as good as those for the known structures of the KcsA K(+) channel and aquaporin 1. We found two channels in Glut1. One of them traverses the structure completely, and is lined by many residues known to be solvent-accessible. Since it is delimited by the QLS motif and by several well conserved residues, it may serve as the substrate transport pathway. To validate our structure, we determined the distance between these channels and all the residues for which mutations are known. From the locations of sugar transporter signatures, motifs, and residues important to the transport function, we find that this Glut1 structure is consistent with mutagenesis and biochemical studies. It also accounts for functional deficits in seven pathogenic mutants.
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Affiliation(s)
- F A Zuniga
- Department of Physiology, College of Physicians & Surgeons, Columbia University, New York, New York 10032, USA
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Klepper J, Monden I, Guertsen E, Voit T, Willemsen M, Keller K. Functional consequences of the autosomal dominant G272A mutation in the human GLUT1 gene. FEBS Lett 2001; 498:104-9. [PMID: 11389907 DOI: 10.1016/s0014-5793(01)02463-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The first autosomal dominant missense mutation (G272A) reported within the human GLUT1 gene and shared by three affected family members was investigated in respect to functional consequences. Substitution of glycine-91 by site-directed mutagenesis with either aspartate or alanine resulted in a significant decrease in transport activity of GLUT1 expressed in Xenopus oocytes. Expression of mutant transporters was confirmed by immunoblot, 2-deoxy-glucose uptake and confocal laser microscopy. The data agree with 3-O-methyl-glucose uptake into patient erythrocytes and indicate that the loss of glycine rather than a hydrophilic side chain (Gly91Asp) defines the functional consequences of this mutation.
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Affiliation(s)
- J Klepper
- Department of Pediatrics and Pediatric Neurology, University of Essen, Germany.
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Rumsey SC, Daruwala R, Al-Hasani H, Zarnowski MJ, Simpson IA, Levine M. Dehydroascorbic acid transport by GLUT4 in Xenopus oocytes and isolated rat adipocytes. J Biol Chem 2000; 275:28246-53. [PMID: 10862609 DOI: 10.1074/jbc.m000988200] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Dehydroascorbic acid (DHA), the first stable oxidation product of vitamin C, was transported by GLUT1 and GLUT3 in Xenopus laevis oocytes with transport rates similar to that of 2-deoxyglucose (2-DG), but due to inherent difficulties with GLUT4 expression in oocytes it was uncertain whether GLUT4 transported DHA (Rumsey, S. C. , Kwon, O., Xu, G. W., Burant, C. F., Simpson, I., and Levine, M. (1997) J. Biol. Chem. 272, 18982-18989). We therefore studied DHA and 2-DG transport in rat adipocytes, which express GLUT4. Without insulin, rat adipocytes transported 2-DG 2-3-fold faster than DHA. Preincubation with insulin (0.67 micrometer) increased transport of each substrate similarly: 7-10-fold for 2-DG and 6-8-fold for DHA. Because intracellular reduction of DHA in adipocytes was complete before and after insulin stimulation, increased transport of DHA was not explained by increased internal reduction of DHA to ascorbate. To determine apparent transport kinetics of GLUT4 for DHA, GLUT4 expression in Xenopus oocytes was reexamined. Preincubation of oocytes for >4 h with insulin (1 micrometer) augmented GLUT4 transport of 2-DG and DHA by up to 5-fold. Transport of both substrates was inhibited by cytochalasin B and displayed saturable kinetics. GLUT4 had a higher apparent transport affinity (K(m) of 0.98 versus 5.2 mm) and lower maximal transport rate (V(max) of 66 versus 880 pmol/oocyte/10 min) for DHA compared with 2-DG. The lower transport rate for DHA could not be explained by binding differences at the outer membrane face, as shown by inhibition with ethylidene glucose, or by transporter trans-activation and therefore was probably due to substrate-specific differences in transporter/substrate translocation or release. These novel data indicate that the insulin-sensitive transporter GLUT4 transports DHA in both rat adipocytes and Xenopus oocytes. Alterations of this mechanism in diabetes could have clinical implications for ascorbate utilization.
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Affiliation(s)
- S C Rumsey
- Molecular and Clinical Nutrition Section, Digestive Diseases Branch, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-1372, USA
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Woodrow CJ, Burchmore RJ, Krishna S. Hexose permeation pathways in Plasmodium falciparum-infected erythrocytes. Proc Natl Acad Sci U S A 2000; 97:9931-6. [PMID: 10954735 PMCID: PMC27630 DOI: 10.1073/pnas.170153097] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2000] [Indexed: 11/18/2022] Open
Abstract
Plasmodium falciparum requires glucose as its energy source to multiply within erythrocytes but is separated from plasma by multiple membrane systems. The mechanism of delivery of substrates such as glucose to intraerythrocytic parasites is unclear. We have developed a system for robust functional expression in Xenopus oocytes of the P. falciparum asexual stage hexose permease, PfHT1, and have analyzed substrate specificities of PfHT1. We show that PfHT1 (a high-affinity glucose transporter, K(m) approximately 1.0 mM) also transports fructose (K(m) approximately 11.5 mM). Fructose can replace glucose as an energy source for intraerythrocytic parasites. PfHT1 binds fructose in a furanose conformation and glucose in a pyranose form. Fructose transport by PfHT1 is ablated by mutation of a single glutamine residue, Q169, which is predicted to lie within helix 5 of the hexose permeation pathway. Glucose transport in the Q169N mutant is preserved. Comparison in oocytes of transport properties of PfHT1 and human facilitative glucose transporter (GLUT)1, an archetypal mammalian hexose transporter, combined with studies on cultured P. falciparum, has clarified hexose permeation pathways in infected erythrocytes. Glucose and fructose enter erythrocytes through separate permeation pathways. Our studies suggest that both substrates enter parasites via PfHT1.
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Affiliation(s)
- C J Woodrow
- Department of Infectious Diseases, St. George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, United Kingdom
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