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Manzari B, Kudlow JE, Fardin P, Merello E, Ottaviano C, Puppo M, Eva A, Varesio L. Induction of Macrophage Glutamine: Fructose-6-Phosphate Amidotransferase Expression by Hypoxia and by Picolinic Acid. Int J Immunopathol Pharmacol 2016; 20:47-58. [PMID: 17346427 DOI: 10.1177/039463200702000106] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
We studied the expression of glutamine:fructose-6-phosphate amidotransferase (GFAT), the rate limiting enzyme in the hexosamine biosynthetic pathway controlling protein glycosylation. We obtained the first evidence that the GFAT mRNA and protein are constitutively expressed in murine mononuclear phagocytes (Mf) and inducible by picolinic acid (PA), a catabolite of tryptophan, hypoxia and desferrioxamine (DFX). These stimuli share the property to transactivate gene expression through the Hypoxia Responsive Element (HRE). The promoter of GFAT contains the consensus sequence of HRE in position −74/-65 (GFAT-HRE), and we studied the role of HRE on the activation of the promoter utilizing appropriate expression vectors. We found that GFAT-HRE is essential for the response to hypoxia, PA or DFX and that Hypoxia Inducible Factor-1α (HIF-1α) can augment this response. Finally, we demonstrate that iron chelation is part of the mechanism by which PA and DFX activate GFAT expression. Our results provide the first indication that hypoxia, PA or DFX induce the transcription of GFAT gene in murine Mf cell lines and that the HRE of the promoter is essential for this response.
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Affiliation(s)
- B Manzari
- Laboratory of Molecular Biology, Giannina Gaslini Institute, Genoa, Italy
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Zachova K, Krupka M, Chamrad I, Belakova J, Horynova M, Weigl E, Sebela M, Raska M. Novel modification of growth medium enables efficient E. coli expression and simple purification of an endotoxin-free recombinant murine hsp70 protein. J Microbiol Biotechnol 2009; 19:727-733. [PMID: 19652522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Heat shock protein 70 kDa (hsp70), a molecular chaperone involved in folding of nascent proteins, has been studied for its ability to activate innate and specific immunity. High purity hsp70 preparation is generally required for immunization experiments, because endotoxins and other immunologically active contaminants may affect immune responses independently of hsp70. We have developed a novel modification of E. coli-expression medium that enabled a simple two-step production and purification method for endotoxin-free recombinant hsp70. During Ni-NTA-based affinity purification of hsp70, a contaminating protein from host E. coli cells, L-glutamine-D-fructose-6-phosphate aminotransferase (GFAT), was identified. By testing various compounds, supplementation of growth medium with a GFAT metabolite, N-acetylglucosamine, was found to reduce GFAT expression and increase the total hsp70 yield five times. The new protocol is based on column purification of His-tagged hsp70 protein produced by E. coli with the modified medium, followed by endotoxin removal by Triton X-114 extraction. This approach yielded hsp70 with high purity and minimal endotoxin contamination, making the final product acceptable for immunization experiments. In summary, a simple modification of growth medium allowed production of recombinant mouse hsp70 in high yield and purity, thus compatible with immunological studies. This protocol may be useful for production of other His.
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Affiliation(s)
- Katerina Zachova
- Department of Immunology, Faculty of Medicine and Dentistry, Palacky University in Olomouc, Trida Svobody, Olomouc
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Reichenbach B, Maes A, Kalamorz F, Hajnsdorf E, Görke B. The small RNA GlmY acts upstream of the sRNA GlmZ in the activation of glmS expression and is subject to regulation by polyadenylation in Escherichia coli. Nucleic Acids Res 2008; 36:2570-80. [PMID: 18334534 PMCID: PMC2377431 DOI: 10.1093/nar/gkn091] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Revised: 02/11/2008] [Accepted: 02/12/2008] [Indexed: 12/31/2022] Open
Abstract
In Escherichia coli the glmS gene encoding glucosamine 6-phosphate (GlcN-6-P) synthase GlmS is feedback regulated by GlcN-6-P in a pathway that involves the small RNA GlmZ. Expression of glmS is activated by the unprocessed form of GlmZ, which accumulates when the intracellular GlcN-6-P concentration decreases. GlmZ stabilizes a glmS transcript that derives from processing. Overexpression of a second sRNA, GlmY, also activates glmS expression in an unknown way. Furthermore, mutations in two genes, yhbJ and pcnB, cause accumulation of full-length GlmZ and thereby activate glmS expression. The function of yhbJ is unknown and pcnB encodes poly(A) polymerase PAP-I known to polyadenylate and destabilize RNAs. Here we show that GlmY acts indirectly in a way that depends on GlmZ. When the intracellular GlcN-6-P concentration decreases, GlmY accumulates and causes in turn accumulation of full-length GlmZ, which finally activates glmS expression. In glmZ mutants, GlmY has no effect on glmS, whereas artificially expressed GlmZ can activate glmS expression also in the absence of GlmY. Furthermore, we show that PAP-I acts at the top of this regulatory pathway by polyadenylating and destabilizing GlmY. In pcnB mutants, GlmY accumulates and induces glmS expression by stabilizing full-length GlmZ. Hence, the data reveal a regulatory cascade composed of two sRNAs, which responds to GlcN-6-P and is controlled by polyadenylation.
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Affiliation(s)
- Birte Reichenbach
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University, Grisebachstrasse 8, D-37077 Göttingen, Germany and Régulation de l'Expression Génétique chez les Microorganismes, Université Denis Diderot Paris 7; CNRS, UPR9073; Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Alexandre Maes
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University, Grisebachstrasse 8, D-37077 Göttingen, Germany and Régulation de l'Expression Génétique chez les Microorganismes, Université Denis Diderot Paris 7; CNRS, UPR9073; Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Falk Kalamorz
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University, Grisebachstrasse 8, D-37077 Göttingen, Germany and Régulation de l'Expression Génétique chez les Microorganismes, Université Denis Diderot Paris 7; CNRS, UPR9073; Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Eliane Hajnsdorf
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University, Grisebachstrasse 8, D-37077 Göttingen, Germany and Régulation de l'Expression Génétique chez les Microorganismes, Université Denis Diderot Paris 7; CNRS, UPR9073; Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Boris Görke
- Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University, Grisebachstrasse 8, D-37077 Göttingen, Germany and Régulation de l'Expression Génétique chez les Microorganismes, Université Denis Diderot Paris 7; CNRS, UPR9073; Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
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Richez C, Boetzel J, Floquet N, Koteshwar K, Stevens J, Badet B, Badet-Denisot MA. Expression and purification of active human internal His(6)-tagged L-glutamine: D-Fructose-6P amidotransferase I. Protein Expr Purif 2007; 54:45-53. [PMID: 17379537 DOI: 10.1016/j.pep.2007.01.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 01/31/2007] [Accepted: 01/31/2007] [Indexed: 11/26/2022]
Abstract
Human L-glutamine: D-fructose-6-phosphate amidotransferase (Gfat1), a recognized target in type 2 diabetes complications, was expressed in Sf9 insect cells with an internal His(6)-tag and purified to homogenity. Two different microplate assays that quantify, respectively D-glucosamine-6-phosphate and L-glutamate were used to analyze the enzyme kinetic properties. The recombinant human L-glutamine: D-fructose-6-phosphate amidotransferase isoform 1 exhibits Michaelis parameters K(m)(Fru-6P)=0.98 mM and K(m)(Gln)=0.84 mM which are similar to the values reported for the same enzyme from different sources. The stimulation of hydrolysis of the alternate substrate L-glutamine para-nitroanilide by D-fructose-6P (Fru-6P) afforded a K(d) of 5 microM for Fru-6P.
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Affiliation(s)
- Céline Richez
- Institut de Chimie des Substances Naturelles, ICSN-CNRS, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
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Olchowy J, Kur K, Sachadyn P, Milewski S. Construction, purification, and functional characterization of His-tagged Candida albicans glucosamine-6-phosphate synthase expressed in Escherichia coli. Protein Expr Purif 2005; 46:309-15. [PMID: 16169745 DOI: 10.1016/j.pep.2005.07.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2005] [Revised: 07/27/2005] [Accepted: 07/28/2005] [Indexed: 10/25/2022]
Abstract
Expression plasmids containing recombinant genes encoding three His(6)-tagged versions of the enzyme, glucosamine-6-phosphate synthase from Candida albicans, were constructed and overexpressed in Escherichia coli. The gene products were purified by metal-affinity chromatography to near homogeneity with 77-80% yield and characterized in terms of size and enzymatic properties. Presence of oligohistidyl tags at either of two ends did not affect enzyme quarternary structure but strongly influenced its catalytic activity. The His6-N-tagged enzyme completely lost an ability of glucosamine-6-phosphate formation and amidohydrolase activity but retained the hexosephosphate-isomerising activity. On the other hand, two His6-C-tagged versions of glucosamine-6-phosphate synthase exhibited amidohydrolase activity almost equal to that of the wild-type enzyme but only 18% of its hexosephosphate-isomerising activity and about 1.5% of the synthetic activity.
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Affiliation(s)
- Jarosław Olchowy
- Department of Pharmaceutical Technology and Biochemistry, Gdańsk University of Technology, 11/12 Narutowicza St., 80-952 Gdańsk, Poland
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Niimi M, Ogawara T, Yamashita T, Yamamoto Y, Ueyama A, Kambe T, Okamoto T, Ban T, Tamanoi H, Ozaki K, Fujiwara T, Fukui H, Takahashi EI, Kyushiki H, Tanigami A. Identification of GFAT1-L, a novel splice variant of human glutamine: fructose-6-phosphate amidotransferase (GFAT1) that is expressed abundantly in skeletal muscle. J Hum Genet 2002; 46:566-71. [PMID: 11587069 DOI: 10.1007/s100380170022] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Glutamine:fructose-6-phosphate amidotransferase (GFAT1) is the rate-limiting enzyme in the hexosamine biosynthetic pathway, which plays an important role in hyperglycemia-induced insulin resistance. To evaluate the role of GFAT1 expression, we analyzed the expression profiles of GFAT1 mRNA in various human tissues using reverse transcriptase-polymerase chain reaction. We report here the identification and cDNA cloning of a novel GFAT1 splice variant expressed abundantly in skeletal muscle and heart. This subtype, designated GFAT1-L, contains a 54-bp insertion within the GFAT1 coding sequence. Recombinant GFAT1-L protein possessed functional GFAT activities and biochemical characteristics similar to GFAT1. Previously, GFAT1 was considered a simplex enzyme. The identification of a novel GFAT1 subtype possessing functional enzymatic activity and tissue-specific expression should provide additional insight into the mechanism of skeletal muscle insulin resistance and diabetes complications.
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Affiliation(s)
- M Niimi
- Otsuka GEN Research Institute, Otsuka Pharmaceutical Co., Ltd., Tokushima, Japan
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Graack HR, Cinque U, Kress H. Functional regulation of glutamine:fructose-6-phosphate aminotransferase 1 (GFAT1) of Drosophila melanogaster in a UDP-N-acetylglucosamine and cAMP-dependent manner. Biochem J 2001; 360:401-12. [PMID: 11716769 PMCID: PMC1222241 DOI: 10.1042/0264-6021:3600401] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glutamine:fructose-6-phosphate aminotransferase (GFAT; EC 2.6.1.16) expression is tightly regulated in the context of amino sugar synthesis in many organisms from yeast to humans by transcriptional and post-translational processes. We have cloned the cDNA of the GFAT1 of Drosophila melanogaster (Dmel/Gfat1). One of the two putative protein kinase A (PKA) phosphorylation sites proposed for the regulation of human GFAT1 [Zhou, Huynh, Hoffmann, Crook, Daniels, Gulve and McClain (1998) Diabetes 47, 1836-1840] is conserved in Dmel/GFAT1. In the other one the reactive serine has been converted to a cysteine, making further access by PKA unlikely. The Dmel/Gfat1 gene is localized at position 81F on the right arm of chromosome 3. By whole-mount in situ hybridization specific expression of Dmel/GFAT1 was detected in embryonic chitin-synthesizing tissues and in the corpus cells of salivary glands from late third larval instar. Expressing Dmel/GFAT1 in yeast we showed that Dmel/GFAT1 activity is controlled by UDP-N-acetylglucosamine and PKA in the yeast total protein extract system. We propose a model for the independent regulation of the Dmel/GFAT1 enzyme by feedback inhibition and PKA.
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Affiliation(s)
- H R Graack
- Institute for Biology-Genetics, Free University of Berlin, Arnimallee 7, D-14195 Berlin, Germany.
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Kaneto H, Xu G, Song KH, Suzuma K, Bonner-Weir S, Sharma A, Weir GC. Activation of the hexosamine pathway leads to deterioration of pancreatic beta-cell function through the induction of oxidative stress. J Biol Chem 2001; 276:31099-104. [PMID: 11390407 DOI: 10.1074/jbc.m104115200] [Citation(s) in RCA: 218] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
It is known well that activation of the hexosamine pathway causes insulin resistance, but how this activation influences pancreatic beta-cell function remains unclear. In this study, we found that in isolated rat islets adenovirus-mediated overexpression of glutamine:fructose-6-phosphate amidotransferase (GFAT), the first and rate-limiting enzyme of the hexosamine pathway, leads to deterioration of beta-cell function, which is similar to that found in diabetes. Overexpression of GFAT or treatment with glucosamine results in impaired glucose-stimulated insulin secretion and reduction in the expression levels of several beta-cell specific genes (insulin, GLUT2, and glucokinase). Additionally, the DNA binding activity of PDX-1, an important transcription factor for these three genes, was markedly reduced. These phenomena were not mimicked by the induction of O-linked glycosylation with an inhibitor of O-GlcNAcase, PUGNAc. It was also found that glucosamine increases hydrogen peroxide levels and that several hexosamine pathway-mediated changes were suppressed by treatment with the antioxidant N-acetyl-l-cysteine. In conclusion, activation of the hexosamine pathway leads to deterioration of beta-cell function through the induction of oxidative stress rather than O-linked glycosylation. Thus, the hexosamine pathway may contribute to the deterioration of beta-cell function found in diabetes.
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Affiliation(s)
- H Kaneto
- Section of Islet Transplantation and Cell Biology, Joslin Diabetes Center, Boston, Massachusetts 02215, USA
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9
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Sachadyn P, Jedrzejczak R, Milewski S, Kur J, Borowski E. Purification to homogeneity of Candida albicans glucosamine-6-phosphate synthase overexpressed in Escherichia coli. Protein Expr Purif 2000; 19:343-9. [PMID: 10910723 DOI: 10.1006/prep.2000.1253] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Candida albicans GFA1 gene encoding glucosamine-6-phosphate synthase, an enzyme of cell wall biosynthesis pathway in fungi and bacteria, recently an object of interest as a target for the chemotherapy of systemic mycoses, was PCR amplified and cloned to an Escherichia coli expression vector pET23b. The activity of the enzyme in the lysates from the overproducing E. coli strain was approximately 50-100 times higher than in the lysates from the control E. coli strain. This abundant overproduction allows to purify milligram amounts of the enzyme to homogeneity.
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Affiliation(s)
- P Sachadyn
- Department of Microbiology, Department of Pharmaceutical Technology and Biochemistry, Technical University of Gdańsk, ul. G. Narutowicza 11/12, Gdańsk, 80-952, Poland.
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Miura N, Kaneko S, Hosoya S, Furuchi T, Miura K, Kuge S, Naganuma A. Overexpression of L-glutamine:D-fructose-6-phosphate amidotransferase provides resistance to methylmercury in Saccharomyces cerevisiae. FEBS Lett 1999; 458:215-8. [PMID: 10481068 DOI: 10.1016/s0014-5793(99)01158-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
To identify novel genes that confer resistance to methylmercury (MeHg), a yeast genomic DNA library was transfected into Saccharomyces cerevisiae. Two functional plasmids were isolated from transfected yeast clones D1 and H5 that exhibited resistance to MeHg. The yeast transfected with plasmid isolated from clone H5 was several-fold more resistant than yeast transfected with plasmid from clone D1. Functional characterization of the genomic DNA fragment obtained from clone H5 determined that the GFA1 gene conferred resistance to MeHg. GFA1 was reported to encode L-glutamine:D-fructose-6-phosphate amidotransferase (GFAT) which catalyzes the synthesis of glucosamine-6-phosphate from glutamine and fructose-6-phosphate. Accumulation of mercury in yeast clone W303B/pGFA1, which contains the transfected GFA1 gene, did not differ from that in control yeast clone W303B/pYES2. The W303B/pGFA1 strain did not show resistance to mercuric chloride, zinc chloride, cadmium chloride or copper chloride, suggesting that the resistance acquired by GFA1 gene transfection might be specific to MeHg. This is the first report of a gene involved in MeHg resistance in eukaryotic cells identified by screening a DNA library.
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Affiliation(s)
- N Miura
- Laboratory of Molecular and Biochemical Toxicology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
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Cooksey RC, Hebert LF, Zhu JH, Wofford P, Garvey WT, McClain DA. Mechanism of hexosamine-induced insulin resistance in transgenic mice overexpressing glutamine:fructose-6-phosphate amidotransferase: decreased glucose transporter GLUT4 translocation and reversal by treatment with thiazolidinedione. Endocrinology 1999; 140:1151-7. [PMID: 10067838 DOI: 10.1210/endo.140.3.6563] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hexosamines have been hypothesized to mediate aspects of glucose sensing and toxic effects of hyperglycemia. For example, insulin resistance results when the rate-limiting enzyme for hexosamine synthesis, glutamine:fructose-6-phosphate amidotransferase (GFA), is overexpressed in muscle and adipose tissue of transgenic mice. The glucose infusion rates required to maintain euglycemia at insulin infusion rates of 0.5, 2, 15, and 20 mU/kg x min were 39-90% lower in such transgenic mice, compared with their control littermates (P < or = 0.01). No differences were observed in hepatic glucose output, serum insulin levels, or muscle ATP levels. Uptake of 2-deoxyglucose, measured under conditions of hyperinsulinemia, was significantly lower in transgenic hindlimb muscle, compared with controls (85.9 +/- 17.8 vs. 166.8 +/- 15.1 pmol deoxyglucose/g x min). The decrease in glucose uptake by transgenic muscle was associated with a disruption in the translocation of the insulin-stimulated glucose transporter GLUT4. Fractionation of muscle membranes on a discontinuous sucrose gradient revealed that insulin stimulation of control muscle led to a 28.8% increase in GLUT4 content in the 25% fraction and a 61.2% decrease in the 35% fraction. In transgenic muscle, the insulin-stimulated shifts in GLUT4 distribution were inhibited by over 70%. Treatment of the transgenic animals with the thiazolidinedione troglitazone completely reversed the defect in glucose disposal without changing GFA activity or the levels of uridine 5'-diphosphate-N-acetylglucosamine. Overexpression of GFA in skeletal muscle thus leads to defects in glucose transport similar to those seen in type 2 diabetes. These data support the hypothesis that excess glucose metabolism through the hexosamine pathway may be responsible for the diminished insulin sensitivity and defective glucose uptake that are seen with hyperglycemia.
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Affiliation(s)
- R C Cooksey
- Department of Medicine of the University of Mississippi Medical Center, Jackson 39216, USA
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12
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Roos MD, Han IO, Paterson AJ, Kudlow JE. Role of glucosamine synthesis in the stimulation of TGF-alpha gene transcription by glucose and EGF. Am J Physiol 1996; 270:C803-11. [PMID: 8638660 DOI: 10.1152/ajpcell.1996.270.3.c803] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Transforming growth factor-alpha (TGF-alpha) gene transcription is regulated by both epidermal growth factor (EGF) and glucose. Previous studies have suggested that the metabolism of glucose to glucosamine through the enzyme L-glutamine: D-fructose-6-phosphate amidotransferase (GFAT) plays a critical role in the glucose signaling. In this paper, we compared the role of GFAT in the glucose and EGF signals. We found that, although EGF stimulates GFAT mRNA accumulation in MDA-MB-468 cells, this effect of EGF occurred several hours after TGF-alpha transcription increased. MDA-MB-468 cells also exhibited a TGF-alpha transcriptional response to low concentrations of glucose. The TGF-alpha response to glucose but not EGF could be inhibited by a blocker of GFAT activity. Blockade of GFAT was confirmed by using Western blotting with the RL2 antibody, which recognizes an epitope on proteins containing N-acetylglucosamine. Exposure of cells to glucose increased the RL2 signal on several polypeptides, but this change could be blocked by inhibition of GFAT. These results support the notion that glucose stimulation of TGF-alpha expression requires GFAT, but EGF stimulation does not.
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Affiliation(s)
- M D Roos
- Division of Endocrinology and Metabolism, University of Alabama at Birmingham 35294, USA
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Fernández-Herrero LA, Badet-Denisot MA, Badet B, Berenguer J. glmS of Thermus thermophilus HB8: an essential gene for cell-wall synthesis identified immediately upstream of the S-layer gene. Mol Microbiol 1995; 17:1-12. [PMID: 7476196 DOI: 10.1111/j.1365-2958.1995.mmi_17010001.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A 30 kbp chromosomal region containing the S-layer gene (slpA) from Thermus thermophilus HB8 was cloned from a lambda phage gene library. DNA sequence analysis of the region upstream to the slpA gene revealed the presence of an open reading frame (ORF) which coded for a 604-amino-acid protein highly homologous to the glucosamine-6-P synthases (EC 2.6.1.16) of both prokaryotic and eukaryotic origin. The identification of this ORF as the glucosamine-6-P synthase gene from T. thermophilus (glmSth) has been carried out using three different strategies: (i) complementation of an Escherichia coli glmS mutant; (ii) in vivo insertional inactivation of the gene; and (iii) in vitro synthesis of glucosamine-6-P at 60 degrees C by a cytoplasmic extract of an overproducing E. coli strain. The glmSth gene is transcribed divergently from slpA in a 2.0 kb mRNA which probably also includes a tryptophan tRNA gene (trpTth) identified at its 3' extreme. As the products of both the glmSth and the slpA genes are main components of the cell envelope of T. thermophilus, their unusual clustering in the chromosome could be related to the existence of specific mechanisms for their coordinate expression.
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Abstract
The hexosamine biosynthesis pathway has been hypothesized to mediate some of the regulatory as well as the deleterious effects of glucose. We have stably overexpressed the cDNA for human glutamine:fructose-6-phosphate amidotransferase (GFA), the rate-limiting enzyme in the hexosamine biosynthesis pathway, in rat-1 fibroblasts. Two cell lines expressing the human RNA were selected by Northern analysis, and they exhibited 51-95% increases in GFA activity. Insulin-stimulated glycogen synthase (GS) activity and net glycogen synthesis were assayed, and GFA cells revealed decreased insulin sensitivity for both GS and net glycogen synthesis. The ED50 for insulin stimulation of GS was 2.45 +/- 0.4 nmol/l insulin in controls and 5.29 +/- 1.01 nmol/l in GFA cells (P < 0.005). For insulin-stimulated glycogen synthesis, the ED50 was 3.43 +/- 0.88 nmol/l in controls and 5.54 +/- 0.98 nmol/l in GFA cells (P < 0.005). There were no significant differences in maximally insulin-stimulated or total GS activities, insulin binding or receptor number, or glucose uptake between GFA and control cells. We also examined the effects of glucose on GS activity. GFA cells had a twofold increase in GS activity at low glucose (0.5 mmol/l) when compared with controls (P < 0.025). Both GFA and control cells had an approximately 75-80% decrease in GS activity as glucose concentration was increased from 0.5 to 20 mmol/l. This change in GS activity was not observed until after 12 h in culture. GFA cells were more sensitive to the effects of glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- E D Crook
- Department of Medicine, University of Mississippi Medical Center, Jackson
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15
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Vijayan E, Jayashree J. Prolactin suppression during pre and post-implantation periods on rat uterine glucosamine synthase activity. Indian J Exp Biol 1993; 31:386-8. [PMID: 8359840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Administration of bromocriptine (Bc), an ergot derivative having dopamine receptor agonist activity, to rats on day 1-5 of pregnancy prevented implantation of blastocysts and significantly suppressed uterine glucosamine 6-phosphate synthase activity. There was no effect on implantation or the enzyme activity when Bc was injected on day 7 or later of pregnancy. Injection of prolactin following Bc partially restored the enzyme activity and increased number of implantation sites. These results indicate that suppression of prolactin on day 1 to 5 of pregnancy causes failure of implantation. Bc on day 9 or later had no effect possibly due to the availability of placental LH/hCG to support the luteal cells.
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Affiliation(s)
- E Vijayan
- School of Life Sciences, Pondicherry University, India
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