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Peixoto JAB, Andrade N, Machado S, Costa ASG, Oliveira MBPP, Martel F, Alves RC. Green/Roasted Coffee and Silverskin Extracts Inhibit Sugar Absorption by Human Intestinal Epithelial (Caco-2) Cells by Decreasing GLUT2 Gene Expression. Foods 2022; 11. [PMID: 36496710 DOI: 10.3390/foods11233902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/26/2022] [Accepted: 11/30/2022] [Indexed: 12/07/2022] Open
Abstract
Moderate coffee ingestion has been associated with a decrease in type 2 diabetes risk, mainly due to its richness in chlorogenic acids (CGA). To explore this, extracts of green beans, roasted beans, and silverskin were prepared by aqueous ultrasound-assisted extraction and characterized by a reversed-phase high-performance liquid chromatography-photodiode array detector (RP-HPLC-DAD). The effects on the uptake of glucose and fructose by human intestinal epithelial (Caco-2) cells and the influence on the expression of sugar transporter genes (by RT-qPCR) were investigated and compared. The uptake of 3H-deoxy-D-glucose and 14C-fructose by Caco-2 cells was significantly reduced by all the extracts, with green coffee (which also contained higher amounts of CGA) achieving the highest efficiency. Although silverskin presented the lowest amounts of CGA and caffeine, it promoted an inhibitory effect similar to the effects of green/roasted beans. In the case of glucose uptake, the effect was even higher than for roasted coffee. This activity is explained by the ability of the extracts to markedly decrease GLUT2, but not GLUT5 gene expression. In addition, a decrease in SGLT1 gene expression was also found for all extracts, although not at a statistically significant rate for silverskin. This study also revealed a synergistic inhibitory effect of caffeine and 5-CQA on the uptake of sugars. Thus, silverskin appears as an interesting alternative to coffee, since the valorization of this by-product also contributes to the sustainability of the coffee chain.
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Rapp J, Wagner B, Brilisauer K, Forchhammer K. In vivo Inhibition of the 3-Dehydroquinate Synthase by 7-Deoxysedoheptulose Depends on Promiscuous Uptake by Sugar Transporters in Cyanobacteria. Front Microbiol 2021; 12:692986. [PMID: 34248919 PMCID: PMC8261047 DOI: 10.3389/fmicb.2021.692986] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/03/2021] [Indexed: 11/13/2022] Open
Abstract
7-Deoxysedoheptulose (7dSh) is a bioactive deoxy-sugar actively excreted by the unicellular cyanobacterium Synechococcus elongatus PCC 7942 (S. elongatus) but also Streptomyces setonensis. In our previous publications we have shown that in S. elongatus, 7dSh is exclusively synthesized by promiscuous enzyme activity from an inhibitory by-product of radical SAM enzymes, without a specific gene cluster being involved. Additionally, we showed that 7dSh inhibits the growth of cyanobacteria, but also the growth of plants and fungi, presumably by inhibiting the 3-dehydroquinate synthase (DHQS), the second enzyme of the shikimate pathway, as the substrate of this enzyme strongly accumulates in cells treated with 7dSh. In this study, by using purified DHQS of Anabaena variabilis ATCC 29413 (A. variabilis) we biochemically confirmed that 7dSh is a competitive inhibitor of this enzyme. By analyzing the effect of 7dSh on a subset of cyanobacteria from all the five subsections, we identified different species whose growth was inhibited by 7dSh. We also found that in some of the susceptible cyanobacteria import of 7dSh is mediated by structurally different and promiscuous transporters: 7dSh can be taken up by the fructose ABC-transporter in A. variabilis and via the glucose permease in Synechocystis sp. PCC 6803 (Synechocystis sp.). In both cases, an effective uptake and thereby intracellular enrichment of 7dSh was essential for the inhibitory activity. Importantly, spontaneous mutations in the sugar transporters of A. variabilis and Synechocystis sp. not only disabled growth of the two strains on fructose and glucose, respectively, but also almost abolished their sensitivity to 7dSh. Although we have clearly shown in these examples that the effective uptake plays an essential role in the inhibitory effect of 7dSh, questions remain about how 7dSh resistance works in other (cyano)bacteria. Also, the involvement of a putative ribokinase in 7dSh resistance in the producer strain S. elongatus remained to be further investigated. Overall, these data establish 7dSh as the first allelochemical targeting the shikimate pathway in other cyanobacteria and plants and suggest a role of 7dSh in niche competition.
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Affiliation(s)
| | | | | | - Karl Forchhammer
- Interfaculty Institute of Microbiology and Infection Medicine, Organismic Interactions, Eberhard Karls Universität Tübingen, Tübingen, Germany
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Cakpo CB, Vercambre G, Baldazzi V, Roch L, Dai Z, Valsesia P, Memah MM, Colombié S, Moing A, Gibon Y, Génard M. Model-assisted comparison of sugar accumulation patterns in ten fleshy fruits highlights differences between herbaceous and woody species. Ann Bot 2020; 126:455-470. [PMID: 32333754 PMCID: PMC7424760 DOI: 10.1093/aob/mcaa082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 04/23/2020] [Indexed: 05/13/2023]
Abstract
BACKGROUND AND AIMS Sugar concentration is a key determinant of fruit quality. Soluble sugars and starch concentrations in fruits vary greatly from one species to another. The aim of this study was to investigate similarities and differences in sugar accumulation strategies across ten contrasting fruit species using a modelling approach. METHODS We developed a coarse-grained model of primary metabolism based on the description of the main metabolic and hydraulic processes (synthesis of compounds other than sugar and starch, synthesis and hydrolysis of starch, and water dilution) involved in the accumulation of soluble sugars during fruit development. KEY RESULTS Statistical analyses based on metabolic rates separated the species into six groups according to the rate of synthesis of compounds other than sugar and starch. Herbaceous species (cucumber, tomato, eggplant, pepper and strawberry) were characterized by a higher synthesis rate than woody species (apple, nectarine, clementine, grape and kiwifruit). Inspection of the dynamics of the processes involved in sugar accumulation revealed that net sugar importation, metabolism and dilution processes were remarkably synchronous in most herbaceous plants, whereas in kiwifruit, apple and nectarine, processes related to starch metabolism were temporally separated from other processes. Strawberry, clementine and grape showed a distinct dynamic compared with all other species. CONCLUSIONS Overall, these results provide fresh insights into species-specific regulatory strategies and into the role of starch metabolism in the accumulation of soluble sugars in fleshy fruits. In particular, inter-specific differences in development period shape the co-ordination of metabolic processes and affect priorities for carbon allocation across species. The six metabolic groups identified by our analysis do not show a clear separation into climacteric and non-climacteric species, possibly suggesting that the metabolic processes related to sugar concentration are not greatly affected by ethylene-associated events.
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Affiliation(s)
- Coffi Belmys Cakpo
- INRAE, UR1115, Unité Plantes et Systèmes de Culture Horticoles, Avignon, France
| | - Gilles Vercambre
- INRAE, UR1115, Unité Plantes et Systèmes de Culture Horticoles, Avignon, France
| | - Valentina Baldazzi
- INRAE, UR1115, Unité Plantes et Systèmes de Culture Horticoles, Avignon, France
- Université Côte d’Azur, INRAE, CNRS, Institut Sophia Agrobiotech, Sophia-Antipolis, France
- Université Côte d’Azur, Inria, INRAE, Sorbonne Université, BIOCORE, Sophia-Antipolis, France
| | - Léa Roch
- INRAE, Univ. Bordeaux, UMR1332 Biologie du Fruit et Pathologie, Villenave d’Ornon, France
| | - Zhanwu Dai
- EGFV, Bordeaux Sciences Agro, INRAE, Université de Bordeaux, Villenave d’Ornon, France
- Beijing Key Laboratory of Grape Science and Enology and Key Laboratory of Plant Resources, Institute of Botany, Chinese Academy of Sciences, Beijing, China
| | - Pierre Valsesia
- INRAE, UR1115, Unité Plantes et Systèmes de Culture Horticoles, Avignon, France
| | | | - Sophie Colombié
- INRAE, Univ. Bordeaux, UMR1332 Biologie du Fruit et Pathologie, Villenave d’Ornon, France
| | - Annick Moing
- INRAE, Univ. Bordeaux, UMR1332 Biologie du Fruit et Pathologie, Villenave d’Ornon, France
- Bordeaux Metabolome Facility– MetaboHUB, Villenave d’Ornon, France
| | - Yves Gibon
- INRAE, Univ. Bordeaux, UMR1332 Biologie du Fruit et Pathologie, Villenave d’Ornon, France
| | - Michel Génard
- INRAE, UR1115, Unité Plantes et Systèmes de Culture Horticoles, Avignon, France
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Kinne R, Spokes KC, Silva P. Sugar uptake, metabolism, and chloride secretion in the rectal gland of the spiny dogfish Squalus acanthias. Am J Physiol Regul Integr Comp Physiol 2020; 319:R96-R105. [PMID: 32459971 DOI: 10.1152/ajpregu.00060.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rectal gland of the spiny dogfish Squalus acanthias secretes a salt solution isosmotic with plasma that maintains the salt homeostasis of the fish. It secretes salt against an electrochemical gradient that requires the expenditure of energy. Isolated rectal glands perfused without glucose secrete salt, albeit at a rate about 30% of glands perfused with 5 mM glucose. Gradually reducing the glucose concentration is associated with a progressive decrease in the secretion of chloride. The apparent Km for the exogenous glucose-dependent chloride secretion is around 2 mM. Phloretin and cytochalasin B, agents that inhibit facilitated glucose carriers of the solute carrier 2 (Slc2) family such as glucose transporter 2 (GLUT2), do not inhibit the secretion of chloride by the perfused rectal glands. Phloridzin, which inhibits Slc5 family of glucose symporters, or α-methyl-d-glucoside, which competitively inhibits the uptake of glucose through Slc5 symporters, inhibit the secretion of chloride. Thus the movement of glucose into the rectal gland cells appears to be mediated by a sodium-glucose symporter. Sodium-glucose cotransporter 1 (SGLT1), the first member of the Slc5 family of sodium-linked glucose symporters, was cloned from the rectal gland. No evidence of GLUT2 was found. The persistence of secretion of chloride in the absence of glucose in the perfusate suggests that there is an additional source of energy within the cells. The use of 2-mercapto-acetate did not result in any change in the secretion of chloride, suggesting that the oxidation of fatty acids is not the source of energy for the secretion of chloride. Perfusion of isolated glands with KCN in the absence of glucose further reduces the secretion of chloride but does not abolish it, again suggesting that there is another source of energy within the cells. Glucose was measured in the rectal gland cells and found to be at concentrations in the range of that in the perfusate. Glycogen measurements indicated that there are significant stores of glucose in the rectal gland. Moreover, glycogen synthase was partially cloned from rectal gland cells. The open reading frame of glycogen phosphorylase was also cloned from rectal gland cells. Measurements of glycogen phosphorylase showed that the enzyme is mostly in its active form in the cells. The cells of the rectal gland of the spiny dogfish require exogenous glucose to fully support the active secretion of salt. They have the means to transport glucose into the cells in the form of SGLT1. The cells also have an endogenous supply of glucose as glycogen and have the necessary elements to synthesize, store, and hydrolyze it.
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Affiliation(s)
- Rolf Kinne
- Max-Planck-Institut für Molekulare Physiologie, Dortmund, Germany.,Mount Desert Island Biological Laboratory, Salsbury Cove, Maine
| | - Katherine C Spokes
- Department of Medicine, Beth Israel Hospital, and Harvard Medical School, Boston, Massachusetts.,Mount Desert Island Biological Laboratory, Salsbury Cove, Maine
| | - Patricio Silva
- Department of Medicine, Temple University School of Medicine, Philadelphia, Pennsylvania.,Mount Desert Island Biological Laboratory, Salsbury Cove, Maine
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Hara KY, Kobayashi J, Yamada R, Sasaki D, Kuriya Y, Hirono-Hara Y, Ishii J, Araki M, Kondo A. Transporter engineering in biomass utilization by yeast. FEMS Yeast Res 2018; 17:4097189. [PMID: 28934416 DOI: 10.1093/femsyr/fox061] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 08/04/2017] [Indexed: 12/17/2022] Open
Abstract
Biomass resources are attractive carbon sources for bioproduction because of their sustainability. Many studies have been performed using biomass resources to produce sugars as carbon sources for cell factories. Expression of biomass hydrolyzing enzymes in cell factories is an important approach for constructing biomass-utilizing bioprocesses because external addition of these enzymes is expensive. In particular, yeasts have been extensively engineered to be cell factories that directly utilize biomass because of their manageable responses to many genetic engineering tools, such as gene expression, deletion and editing. Biomass utilizing bioprocesses have also been developed using these genetic engineering tools to construct metabolic pathways. However, sugar input and product output from these cells are critical factors for improving bioproduction along with biomass utilization and metabolic pathways. Transporters are key components for efficient input and output activities. In this review, we focus on transporter engineering in yeast to enhance bioproduction from biomass resources.
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Affiliation(s)
- Kiyotaka Y Hara
- Division of Environmental and Life Sciences, Graduate Division of Nutritional and Environmental Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.,School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Jyumpei Kobayashi
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Ryosuke Yamada
- Department of Chemical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Daisuke Sasaki
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Yuki Kuriya
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Yoko Hirono-Hara
- School of Food and Nutritional Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan
| | - Jun Ishii
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
| | - Michihiro Araki
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan.,Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Syogoin, Sakyo-ku, Kyoto 606-8507, Japan
| | - Akihiko Kondo
- Graduate School of Science, Technology, and Innovation, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan.,Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo 657-8501, Japan
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López-Yoldi M, Castilla-Madrigal R, Lostao MP, Barber A, Prieto J, Martínez JA, Bustos M, Moreno-Aliaga MJ. Cardiotrophin-1 decreases intestinal sugar uptake in mice and in Caco-2 cells. Acta Physiol (Oxf) 2016; 217:217-26. [PMID: 26972986 DOI: 10.1111/apha.12674] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 10/12/2015] [Accepted: 03/04/2016] [Indexed: 12/15/2022]
Abstract
AIM Cardiotrophin-1 (CT-1) is a member of the IL-6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT-1 treatment on intestinal sugar absorption in different experimental models. METHODS rCT-1 effects on α-Methyl-D-glucoside uptake were assessed in everted intestinal rings from wild-type and CT-1(-/-) mice and in Caco-2 cells. rCT-1 actions on SGLT-1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot. RESULTS In vivo administration (0.2 mg kg(-1) ) of rCT-1 caused a significant decrease on α-Methyl-D-glucoside uptake in everted intestinal rings from wild-type and CT-1(-/-) mice after short-term and long-term treatments. Similarly, in vitro treatment (1-50 ng mL(-1) ) with rCT-1 reduced α-Methyl-D-glucoside uptake in everted intestinal rings. In Caco-2 cells, rCT-1 treatment (20 ng mL(-1) , 1 and 24 h) lowered apical uptake of α-Methyl-D-glucoside in parallel with a decrease on SGLT-1 protein expression. rCT-1 promoted the phosphorylation of STAT-3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre-treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT-1 on α-Methyl-D-glucoside uptake. AICAR also prevented the inhibition of SGLT-1 observed in rCT-1-treated cells. CONCLUSIONS CT-1 inhibits intestinal sugar absorption by the reduction of SGLT-1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti-obesity properties of CT-1.
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Affiliation(s)
- M. López-Yoldi
- Department of Nutrition, Food Science and Physiology; University of Navarra; Pamplona Navarra Spain
- Centre for Nutrition Research; University of Navarra; Pamplona Navarra Spain
| | - R. Castilla-Madrigal
- Department of Nutrition, Food Science and Physiology; University of Navarra; Pamplona Navarra Spain
- Centre for Nutrition Research; University of Navarra; Pamplona Navarra Spain
| | - M. P. Lostao
- Department of Nutrition, Food Science and Physiology; University of Navarra; Pamplona Navarra Spain
- Centre for Nutrition Research; University of Navarra; Pamplona Navarra Spain
- IdiSNA; Navarra Institute for Health Research; Pamplona Spain
| | - A. Barber
- Department of Nutrition, Food Science and Physiology; University of Navarra; Pamplona Navarra Spain
| | - J. Prieto
- Department of Gene Therapy and Hepatology; CIMA; University of Navarra; Pamplona Navarra Spain
- CIBERehd; Institute of Health Carlos III; Madrid Spain
| | - J. A. Martínez
- Department of Nutrition, Food Science and Physiology; University of Navarra; Pamplona Navarra Spain
- Centre for Nutrition Research; University of Navarra; Pamplona Navarra Spain
- IdiSNA; Navarra Institute for Health Research; Pamplona Spain
- CIBERobn; Physiopathology of Obesity and Nutrition; Institute of Health Carlos III; Madrid Spain
| | - M. Bustos
- Department of Gene Therapy and Hepatology; CIMA; University of Navarra; Pamplona Navarra Spain
| | - M. J. Moreno-Aliaga
- Department of Nutrition, Food Science and Physiology; University of Navarra; Pamplona Navarra Spain
- Centre for Nutrition Research; University of Navarra; Pamplona Navarra Spain
- IdiSNA; Navarra Institute for Health Research; Pamplona Spain
- CIBERobn; Physiopathology of Obesity and Nutrition; Institute of Health Carlos III; Madrid Spain
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7
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Abdel-Basset R, Ozuka S, Demiral T, Furuichi T, Sawatani I, Baskin TI, Matsumoto H, Yamamoto Y. Aluminium reduces sugar uptake in tobacco cell cultures: a potential cause of inhibited elongation but not of toxicity. J Exp Bot 2010; 61:1597-610. [PMID: 20219776 PMCID: PMC2852655 DOI: 10.1093/jxb/erq027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 01/04/2010] [Accepted: 01/25/2010] [Indexed: 05/10/2023]
Abstract
Aluminium is well known to inhibit plant elongation, but the role in this inhibition played by water relations remains unclear. To investigate this, tobacco (Nicotiana tabacum L.) suspension-cultured cells (line SL) was used, treating them with aluminium (50 microM) in a medium containing calcium, sucrose, and MES (pH 5.0). Over an 18 h treatment period, aluminium inhibited the increase in fresh weight almost completely and decreased cellular osmolality and internal soluble sugar content substantially; however, aluminium did not affect the concentrations of major inorganic ions. In aluminium-treated cultures, fresh weight, soluble sugar content, and osmolality decreased over the first 6 h and remained constant thereafter, contrasting with their continued increases in the untreated cultures. The rate of sucrose uptake, measured by radio-tracer, was reduced by approximately 60% within 3 h of treatment. Aluminium also inhibited glucose uptake. In an aluminium-tolerant cell line (ALT301) isogenic to SL, all of the above-mentioned changes in water relations occurred and tolerance emerged only after 6 h and appeared to involve the suppression of reactive oxygen species. Further separating the effects of aluminium on elongation and cell survival, sucrose starvation for 18 h inhibited elongation and caused similar changes in cellular osmolality but stimulated the production of neither reactive oxygen species nor callose and did not cause cell death. We propose that the inhibition of sucrose uptake is a mechanism whereby aluminium inhibits elongation, but does not account for the induction of cell death.
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Affiliation(s)
- Refat Abdel-Basset
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
| | - Shotaro Ozuka
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
| | - Tijen Demiral
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
- Department of Biology, Science Faculty, Ege University, Bornova 35100, Izmir, Turkey
| | - Takuya Furuichi
- Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan
| | - Ikuo Sawatani
- Glycoscience Institute, Research Center, Hayashibara Biochemical Laboratories, Inc., 675-1 Fujisaki, Okayama 702-8006, Japan
| | - Tobias I. Baskin
- Biology Department, University of Massachusetts, 611 N Pleasant St, Amherst, MA 01003, USA
| | - Hideaki Matsumoto
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
| | - Yoko Yamamoto
- Research Institute for Bioresources, Okayama University, Chuo 2-20-1, Kurashiki 710-0046, Japan
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Abstract
We analyze the connection between structure and function for regulatory motifs associated with cellular uptake and usage of small molecules. Based on the boolean logic of the feedback we suggest four classes: the socialist, consumer, fashion, and collector motifs. We find that the socialist motif is good for homeostasis of a useful but potentially poisonous molecule, whereas the consumer motif is optimal for nutrition molecules. Accordingly, examples of these motifs are found in, respectively, the iron homeostasis system in various organisms and in the uptake of sugar molecules in bacteria. The remaining two motifs have no obvious analogs in small molecule regulation, but we illustrate their behavior using analogies to fashion and obesity. These extreme motifs could inspire construction of synthetic systems that exhibit bistable, history-dependent states, and homeostasis of flux (rather than concentration).
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Affiliation(s)
- Sandeep Krishna
- Department of Genetics, Eotvos Lorand University, Budapest H-1117, Hungary.
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Singh VN, Singh M, August JT, Horecker BL. Alterations in glucose metabolism in chick-embryo cells transformed by Rous sarcoma virus: intracellular levels of glycolytic intermediates. Proc Natl Acad Sci U S A 1974; 71:4129-32. [PMID: 4372608 PMCID: PMC434342 DOI: 10.1073/pnas.71.10.4129] [Citation(s) in RCA: 76] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Chick-embryo cells, transformed with Rous sarcoma virus, show enhanced rates of sugar transport and glycolysis. Determination of intracellular concentrations of glycolytic intermediates suggests that the enhanced glycolytic flux is due to increased activities of hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1), phosphofructokinase, (ATP:D-fructose-1-phosphate 6-phosphotransferase, EC 2.7.1.56), and pyruvate kinase (ATP:pyruvate 2-O-phosphotransferase, EC 2.7.1.40), and not directly to the increased glucose transport. This conclusion is supported by the finding that the intracellular concentration of free glucose is decreased, rather than increased, in the transformed cells. The present observations suggest that the increased glycolytic flux is related to an increased rate of phosphorylation of glucose, and that hexokinase in the transformed cells is at least partly released from its normal control mechanism involving feedback inhibition by glucose-6-P.
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