1
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Suades A, Qureshi A, McComas SE, Coinçon M, Rudling A, Chatzikyriakidou Y, Landreh M, Carlsson J, Drew D. Establishing mammalian GLUT kinetics and lipid composition influences in a reconstituted-liposome system. Nat Commun 2023; 14:4070. [PMID: 37429918 DOI: 10.1038/s41467-023-39711-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Accepted: 06/26/2023] [Indexed: 07/12/2023] Open
Abstract
Glucose transporters (GLUTs) are essential for organism-wide glucose homeostasis in mammals, and their dysfunction is associated with numerous diseases, such as diabetes and cancer. Despite structural advances, transport assays using purified GLUTs have proven to be difficult to implement, hampering deeper mechanistic insights. Here, we have optimized a transport assay in liposomes for the fructose-specific isoform GLUT5. By combining lipidomic analysis with native MS and thermal-shift assays, we replicate the GLUT5 transport activities seen in crude lipids using a small number of synthetic lipids. We conclude that GLUT5 is only active under a specific range of membrane fluidity, and that human GLUT1-4 prefers a similar lipid composition to GLUT5. Although GLUT3 is designated as the high-affinity glucose transporter, in vitro D-glucose kinetics demonstrates that GLUT1 and GLUT3 actually have a similar KM, but GLUT3 has a higher turnover. Interestingly, GLUT4 has a high KM for D-glucose and yet a very slow turnover, which may have evolved to ensure uptake regulation by insulin-dependent trafficking. Overall, we outline a much-needed transport assay for measuring GLUT kinetics and our analysis implies that high-levels of free fatty acid in membranes, as found in those suffering from metabolic disorders, could directly impair glucose uptake.
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Affiliation(s)
- Albert Suades
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius v. 16c, SE-106 91, Stockholm, Sweden
| | - Aziz Qureshi
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius v. 16c, SE-106 91, Stockholm, Sweden
| | - Sarah E McComas
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius v. 16c, SE-106 91, Stockholm, Sweden
| | - Mathieu Coinçon
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius v. 16c, SE-106 91, Stockholm, Sweden
| | - Axel Rudling
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC, Box 596, SE-751 24, Uppsala, Sweden
| | - Yurie Chatzikyriakidou
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius v. 16c, SE-106 91, Stockholm, Sweden
| | - Michael Landreh
- Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solnavägen 9, SE-171 65, Solna, Sweden
| | - Jens Carlsson
- Science for Life Laboratory, Department of Cell and Molecular Biology, Uppsala University, BMC, Box 596, SE-751 24, Uppsala, Sweden
| | - David Drew
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius v. 16c, SE-106 91, Stockholm, Sweden.
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2
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Custódio TF, Paulsen PA, Frain KM, Pedersen BP. Structural comparison of GLUT1 to GLUT3 reveal transport regulation mechanism in sugar porter family. Life Sci Alliance 2021; 4:4/4/e202000858. [PMID: 33536238 PMCID: PMC7898563 DOI: 10.26508/lsa.202000858] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 01/18/2021] [Accepted: 01/19/2021] [Indexed: 12/19/2022] Open
Abstract
The human glucose transporters GLUT1 and GLUT3 have a central role in glucose uptake as canonical members of the Sugar Porter (SP) family. GLUT1 and GLUT3 share a fully conserved substrate-binding site with identical substrate coordination, but differ significantly in transport affinity in line with their physiological function. Here, we present a 2.4 Å crystal structure of GLUT1 in an inward open conformation and compare it with GLUT3 using both structural and functional data. Our work shows that interactions between a cytosolic "SP motif" and a conserved "A motif" stabilize the outward conformational state and increases substrate apparent affinity. Furthermore, we identify a previously undescribed Cl- ion site in GLUT1 and an endofacial lipid/glucose binding site which modulate GLUT kinetics. The results provide a possible explanation for the difference between GLUT1 and GLUT3 glucose affinity, imply a general model for the kinetic regulation in GLUTs and suggest a physiological function for the defining SP sequence motif in the SP family.
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Affiliation(s)
| | - Peter Aasted Paulsen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Kelly May Frain
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Bjørn Panyella Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark .,Aarhus Institute of Advanced Studies, Aarhus University, Aarhus C, Denmark
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3
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Matsuo S, Hiasa M, Omote H. Functional characterization and tissue localization of the facilitative glucose transporter GLUT12. J Biochem 2020; 168:611-620. [PMID: 32761185 DOI: 10.1093/jb/mvaa090] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 06/28/2020] [Indexed: 11/13/2022] Open
Abstract
Facilitative glucose transporters (GLUTs) play crucial roles in glucose utilization and homeostasis. GLUT12 was initially isolated as a novel GLUT4-like transporter involved in insulin-dependent glucose transport. However, tissue distribution and biochemical properties of GLUT12 are not well understood. In this study, we investigated the basic kinetic properties and tissue distribution of GLUT12. Human GLUT12 and GLUT1 were overexpressed and purified using Ni-NTA column chromatography. Reconstituted proteoliposomes showed time-dependent d-glucose transport activity, which was inhibited by phloretin and dehydroascorbate. Dose dependence of glucose transport revealed a KM and Vmax values of 6.4 mM and 1.2 μmol/mg/min, respectively, indicating that GLUT12 is a high-affinity type GLUT. Glucose transport by GLUT12 was inhibited by ATP and glucose-1-phosphate, glucose-6-phosphate and disaccharides (properties similar to those of GLUT1). Indirect immunohistochemistry revealed the distribution of mouse GLUT12 in the apical region of distal tubules and collecting ducts in the kidney and epithelial cells of the jejunum. In addition to these cells, GLUT12 was present in chromaffin cells in the adrenal medulla, the anterior pituitary lobe, as well as the thyroid and pyloric glands. These tissue distributions suggest a unique function of GLUT12, besides that of an insulin-dependent glucose transport.
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Affiliation(s)
- Shunsuke Matsuo
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
| | - Miki Hiasa
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
| | - Hiroshi Omote
- Department of Membrane Biochemistry, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan
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4
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Paulsen PA, Custódio TF, Pedersen BP. Crystal structure of the plant symporter STP10 illuminates sugar uptake mechanism in monosaccharide transporter superfamily. Nat Commun 2019; 10:407. [PMID: 30679446 PMCID: PMC6345825 DOI: 10.1038/s41467-018-08176-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 12/19/2018] [Indexed: 01/06/2023] Open
Abstract
Plants are dependent on controlled sugar uptake for correct organ development and sugar storage, and apoplastic sugar depletion is a defense strategy against microbial infections like rust and mildew. Uptake of glucose and other monosaccharides is mediated by Sugar Transport Proteins, proton-coupled symporters from the Monosaccharide Transporter (MST) superfamily. We present the 2.4 Å structure of Arabidopsis thaliana high affinity sugar transport protein, STP10, with glucose bound. The structure explains high affinity sugar recognition and suggests a proton donor/acceptor pair that links sugar transport to proton translocation. It contains a Lid domain, conserved in all STPs, that locks the mobile transmembrane domains through a disulfide bridge, and creates a protected environment which allows efficient coupling of the proton gradient to drive sugar uptake. The STP10 structure illuminates fundamental principles of sugar transport in the MST superfamily with implications for both plant antimicrobial defense, organ development and sugar storage.
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Affiliation(s)
- Peter Aasted Paulsen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark
| | - Tânia F Custódio
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark
| | - Bjørn Panyella Pedersen
- Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark.
- Aarhus Institute of Advanced Studies, Aarhus University, Høegh-Guldbergs Gade 6B, DK-8000, Aarhus C, Denmark.
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5
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Kanska J, Aspuria PJP, Taylor-Harding B, Spurka L, Funari V, Orsulic S, Karlan BY, Wiedemeyer WR. Glucose deprivation elicits phenotypic plasticity via ZEB1-mediated expression of NNMT. Oncotarget 2018; 8:26200-26220. [PMID: 28412735 PMCID: PMC5432250 DOI: 10.18632/oncotarget.15429] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 02/06/2017] [Indexed: 12/13/2022] Open
Abstract
Glucose is considered the primary energy source for all cells, and some cancers are addicted to glucose. Here, we investigated the functional consequences of chronic glucose deprivation in serous ovarian cancer cells. We found that cells resistant to glucose starvation (glucose-restricted cells) demonstrated increased metabolic plasticity that was dependent on NNMT (Nicotinamide N-methyltransferase) expression. We further show that ZEB1 induced NNMT, rendered cells resistant to glucose deprivation and recapitulated metabolic adaptations and mesenchymal gene expression observed in glucose-restricted cells. NNMT depletion reversed metabolic plasticity in glucose-restricted cells and prevented de novo formation of glucose-restricted colonies. In addition to its role in glucose independence, we found that NNMT was required for other ZEB1-induced phenotypes, such as increased migration. NNMT protein levels were also elevated in metastatic and recurrent tumors compared to matched primary carcinomas, while normal ovary and fallopian tube tissue had no detectable NNMT expression. Our studies define a novel ZEB1/NNMT signaling axis, which elicits mesenchymal gene expression, as well as phenotypic and metabolic plasticity in ovarian cancer cells upon chronic glucose starvation. Understanding the causes of cancer cell plasticity is crucial for the development of therapeutic strategies to counter intratumoral heterogeneity, acquired drug resistance and recurrence in high-grade serous ovarian cancer (HGSC).
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Affiliation(s)
- Justyna Kanska
- Women's Cancer Program at the Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Paul-Joseph P Aspuria
- Women's Cancer Program at the Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Barbie Taylor-Harding
- Women's Cancer Program at the Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Lindsay Spurka
- Genomics Core, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Vincent Funari
- Genomics Core, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
| | - Sandra Orsulic
- Women's Cancer Program at the Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,Department of Obstetrics and Gynecology, David Geffen School of Medicine, University of California, Los Angeles, CA 90048, USA
| | - Beth Y Karlan
- Women's Cancer Program at the Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,Department of Obstetrics and Gynecology, David Geffen School of Medicine, University of California, Los Angeles, CA 90048, USA
| | - W Ruprecht Wiedemeyer
- Women's Cancer Program at the Samuel Oschin Cancer Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA.,Department of Obstetrics and Gynecology, David Geffen School of Medicine, University of California, Los Angeles, CA 90048, USA
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6
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Kitaoka S, Morielli AD, Zhao FQ. FGT-1-mediated glucose uptake is defective in insulin/IGF-like signaling mutants in Caenorhabditis elegans. FEBS Open Bio 2016; 6:576-85. [PMID: 27419060 PMCID: PMC4887973 DOI: 10.1002/2211-5463.12068] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/27/2016] [Accepted: 04/05/2016] [Indexed: 11/23/2022] Open
Abstract
Insulin signaling plays a central role in the regulation of facilitative glucose transporters (GLUTs) in humans. To establish Caenorhabditis elegans (C. elegans) as a model to study the mechanism underlying insulin regulation of GLUT, we identified that FGT‐1 is most likely the only functional GLUT homolog in C. elegans and is ubiquitously expressed. The FGT‐1‐mediated glucose uptake was almost completely defective in insulin/IGF‐like signaling (IIS) mutants daf‐2 and age‐1, and this defect mainly resulted from the down‐regulated FGT‐1 protein expression. However, glycosylation may also be involved because OGA‐1, an O‐GlcNAcase, was essential for the function of FGT‐1. Thus, our study showed that C. elegans can be a new powerful model system to study insulin regulation of GLUT.
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Affiliation(s)
- Shun Kitaoka
- Laboratory of Lactation and Metabolic Physiology Department of Animal and Veterinary Sciences University of Vermont Burlington VT USA; Present address: Drug Discovery Laboratory Wakunaga Pharmaceutical Co., Ltd. Akitakata Hiroshima Japan
| | - Anthony D Morielli
- Department of Pharmacology College of Medicine University of Vermont Burlington VT USA
| | - Feng-Qi Zhao
- Laboratory of Lactation and Metabolic Physiology Department of Animal and Veterinary Sciences University of Vermont Burlington VT USA
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7
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Liu Z, Moate P, Cocks B, Rochfort S. Simple liquid chromatography-mass spectrometry method for quantification of major free oligosaccharides in bovine milk. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2014; 62:11568-11574. [PMID: 25365143 DOI: 10.1021/jf5037849] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Free oligosaccharides (OS) are a significant functional component of milk that are difficult to quantitate. A simple method for quantitative analysis of the major free OS in bovine milk is described. Following a defatting step, protein elimination was performed by ultrafiltration. OS were separated by hydrophilic interaction liquid chromatography (HILIC) and detected by an Orbitrap mass analyzer in negative mode. The method is sensitive [with a limit of detection (LOD) for all representative OS of <0.1 ng] and reproducible, enabling simultaneous quantification of 13 major OS within a single run. Application of this method to the quantification of major OS in 32 milk samples collected after three different feeding treatments allowed us to reveal the relative abundance of different OS species, the variation of the OS content between individual cows, and the correlations between some of the major OS.
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Affiliation(s)
- Zhiqian Liu
- Biosciences Research Division, Department of Environment and Primary Industries, AgriBio , 5 Ring Road, Bundoora, Victoria 3083, Australia
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8
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Marín-Hernández A, López-Ramírez SY, Del Mazo-Monsalvo I, Gallardo-Pérez JC, Rodríguez-Enríquez S, Moreno-Sánchez R, Saavedra E. Modeling cancer glycolysis under hypoglycemia, and the role played by the differential expression of glycolytic isoforms. FEBS J 2014; 281:3325-45. [DOI: 10.1111/febs.12864] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 04/15/2014] [Accepted: 05/27/2014] [Indexed: 12/15/2022]
Affiliation(s)
| | | | | | | | - Sara Rodríguez-Enríquez
- Departamento de Bioquímica; Instituto Nacional de Cardiología; Mexico
- Laboratorio de Medicina Traslacional; Instituto Nacional de Cancerología; Mexico
| | | | - Emma Saavedra
- Departamento de Bioquímica; Instituto Nacional de Cardiología; Mexico
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9
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Pizarro-Delgado J, Fasciani I, Temperan A, Romero M, González-Nieto D, Alonso-Magdalena P, Nualart-Marti A, Estil'les E, Paul DL, Martín-del-Río R, Montanya E, Solsona C, Nadal A, Barrio LC, Tamarit-Rodríguez J. Inhibition of connexin 36 hemichannels by glucose contributes to the stimulation of insulin secretion. Am J Physiol Endocrinol Metab 2014; 306:E1354-66. [PMID: 24735890 DOI: 10.1152/ajpendo.00358.2013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The existence of functional connexin36 (Cx36) hemichannels in β-cells was investigated in pancreatic islets of rat and wild-type (Cx36(+/+)), monoallelic (Cx36(+/-)), and biallelic (Cx36(-/-)) knockout mice. Hemichannel opening by KCl depolarization was studied by measuring ATP release and changes of intracellular ATP (ADP). Cx36(+/+) islets lost ATP after depolarization with 70 mM KCl at 5 mM glucose; ATP loss was prevented by 8 and 20 mM glucose or 50 μM mefloquine (connexin inhibitor). ATP content was higher in Cx36(-/-) than Cx36(+/+) islets and was not decreased by KCl depolarization; Cx36(+/-) islets showed values between that of control and homozygous islets. Five minimolar extracellular ATP increased ATP content and ATP/ADP ratio and induced a biphasic insulin secretion in depolarized Cx36(+/+) and Cx36(+/-) but not Cx36(-/-) islets. Cx36 hemichannels expressed in oocytes opened upon depolarization of membrane potential, and their activation was inhibited by mefloquine and glucose (IC₅₀ ∼8 mM). It is postulated that glucose-induced inhibition of Cx36 hemichannels in islet β-cells might avoid depolarization-induced ATP loss, allowing an optimum increase of the ATP/ADP ratio by sugar metabolism and a biphasic stimulation of insulin secretion. Gradual suppression of glucose-induced insulin release in Cx36(+/-) and Cx36(-/-) islets confirms that Cx36 gap junction channels are necessary for a full secretory stimulation and might account for the glucose intolerance observed in mice with defective Cx36 expression. Mefloquine targeting of Cx36 on both gap junctions and hemichannels also suppresses glucose-stimulated secretion. By contrast, glucose stimulation of insulin secretion requires Cx36 hemichannels' closure but keeping gap junction channels opened.
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Affiliation(s)
| | - Ilaria Fasciani
- Research Department, "Ramón y Cajal" Hospital-IRYCIS, Madrid, Spain
| | - Ana Temperan
- Research Department, "Ramón y Cajal" Hospital-IRYCIS, Madrid, Spain
| | - María Romero
- Research Department, "Ramón y Cajal" Hospital-IRYCIS, Madrid, Spain
| | | | - Paloma Alonso-Magdalena
- Institute of Bioengineering and CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Miguel Hernández University, Elche, Spain
| | - Anna Nualart-Marti
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine - Campus Bellvitge, University of Barcelona, Hospitalet del Llobregat, Barcelona, Spain; IDIBELL, Institut d'Investigació Biomèdica de Bellvitge, Hospitalet del Llobregat, Barcelona, Spain
| | - Elisabet Estil'les
- CIBERDEM, Barcelona, Spain; Department of Clinical Sciences, University of Barcelona, Feixa Llarga s/n, L'Hospitalet de Llobregat, Barcelona, Spain; and
| | - David L Paul
- Department of Neurobiology, Harvard Medical School, Boston, Massachusetts
| | | | - Eduard Montanya
- CIBERDEM, Barcelona, Spain; Department of Clinical Sciences, University of Barcelona, Feixa Llarga s/n, L'Hospitalet de Llobregat, Barcelona, Spain; and Endocrine Unit, Hospital Universitari Bellvitge-IDIBELL, Barcelona, Spain
| | - Carles Solsona
- Department of Pathology and Experimental Therapeutics, Faculty of Medicine - Campus Bellvitge, University of Barcelona, Hospitalet del Llobregat, Barcelona, Spain; IDIBELL, Institut d'Investigació Biomèdica de Bellvitge, Hospitalet del Llobregat, Barcelona, Spain
| | - Angel Nadal
- Institute of Bioengineering and CIBER de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Miguel Hernández University, Elche, Spain
| | | | - J Tamarit-Rodríguez
- Biochemistry Department, Medical School, Complutense University, Madrid, Spain;
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10
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Zhao FQ. Biology of glucose transport in the mammary gland. J Mammary Gland Biol Neoplasia 2014; 19:3-17. [PMID: 24221747 DOI: 10.1007/s10911-013-9310-8] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 10/29/2013] [Indexed: 01/10/2023] Open
Abstract
Glucose is the major precursor of lactose, which is synthesized in Golgi vesicles of mammary secretory alveolar epithelial cells during lactation. Glucose is taken up by mammary epithelial cells through a passive, facilitative process, which is driven by the downward glucose concentration gradient across the plasma membrane. This process is mediated by facilitative glucose transporters (GLUTs), of which there are 14 known isoforms. Mammary glands mainly express GLUT1 and GLUT8, and GLUT1 is the predominant isoform with a Km of ~10 mM and transport activity for mannose and galactose in addition to glucose. Mammary glucose transport activity increases dramatically from the virgin state to the lactation state, with a concomitant increase in GLUT expression. The increased GLUT expression during lactogenesis is not stimulated by the accepted lactogenic hormones. New evidence indicates that a possible low oxygen tension resulting from increased metabolic rate and oxygen consumption may play a major role in stimulating glucose uptake and GLUT1 expression in mammary epithelial cells during lactogenesis. In addition to its primary presence on the plasma membrane, GLUT1 is also expressed on the Golgi membrane of mammary epithelial cells and is likely involved in facilitating the uptake of glucose and galactose to the site of lactose synthesis. Because lactose synthesis dictates milk volume, regulation of GLUT expression and trafficking represents potentially fruitful areas for further research in dairy production. In addition, this research will have pathological implications for the treatment of breast cancer because glucose uptake and GLUT expression are up-regulated in breast cancer cells to accommodate the increased glucose need.
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Affiliation(s)
- Feng-Qi Zhao
- Laboratory of Lactation and Metabolic Physiology, Department of Animal Science, University of Vermont, 211 Terrill Building, 570 Main Street, Burlington, VT, 05405, USA,
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11
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Kitaoka S, Morielli AD, Zhao FQ. FGT-1 is a mammalian GLUT2-like facilitative glucose transporter in Caenorhabditis elegans whose malfunction induces fat accumulation in intestinal cells. PLoS One 2013; 8:e68475. [PMID: 23826391 PMCID: PMC3691140 DOI: 10.1371/journal.pone.0068475] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Accepted: 06/05/2013] [Indexed: 11/28/2022] Open
Abstract
Caenorhabditis elegans (C. elegans) is an attractive animal model for biological and biomedical research because it permits relatively easy genetic dissection of cellular pathways, including insulin/IGF-like signaling (IIS), that are conserved in mammalian cells. To explore C. elegans as a model system to study the regulation of the facilitative glucose transporter (GLUT), we have characterized the GLUT gene homologues in C. elegans: fgt-1, R09B5.11, C35A11.4, F53H8.3, F48E3.2, F13B12.2, Y61A9LA.1, K08F9.1 and Y37A1A.3. The exogenous expression of these gene products in Xenopus oocytes showed transport activity to unmetabolized glucose analogue 2-deoxy-D-glucose only in FGT-1. The FGT-1-mediated transport activity was inhibited by the specific GLUT inhibitor phloretin and exhibited a Michaelis constant (Km) of 2.8 mM. Mannose, galactose, and fructose were able to inhibit FGT-1-mediated 2-deoxy-D-glucose uptake (P < 0.01), indicating that FGT-1 is also able to transport these hexose sugars. A GFP fusion protein of FGT-1 was observed only on the basolateral membrane of digestive tract epithelia in C. elegans, but not in other tissues. FGT-1::eGFP expression was observed from early embryonic stages. The knockdown or mutation of fgt-1 resulted in increased fat staining in both wild-type and daf-2 (mammalian insulin receptor homologue) mutant animals. Other common phenotypes of IIS mutant animals, including dauer formation and brood size reduction, were not affected by fgt-1 knockdown in wild-type or daf-2 mutants. Our results indicated that in C. elegans, FGT-1 is mainly a mammalian GLUT2-like intestinal glucose transporter and is involved in lipid metabolism.
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Affiliation(s)
- Shun Kitaoka
- Laboratory of Lactation and Metabolic Physiology, Department of Animal Science, University of Vermont, Burlington, Vermont, United States of America
| | - Anthony D. Morielli
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, United States of America
| | - Feng-Qi Zhao
- Laboratory of Lactation and Metabolic Physiology, Department of Animal Science, University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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