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Ince V, Carr BI, Bag HG, Koc C, Usta S, Ersan V, Baskiran A, Sahin TT, Yilmaz S. Gamma glutamyl transpeptidase as a prognostic biomarker in hepatocellular cancer patients especially with >5 cm tumors, treated by liver transplantation. Int J Biol Markers 2020; 35:91-95. [PMID: 32436751 DOI: 10.1177/1724600820921869] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BackgroundSerum AFP levels are typically elevated in less than 50% of hepatocellular cancer (HCC) patients. Gamma-glutamyl transpeptidase (GGT) levels have been suggested to be a potentially useful HCC biomarker.AimsTo assess in a cohort of prospectively evaluated HCC patients who underwent liver transplant and whose survival was known; the occurrence, prognosis, and clinical characteristics of patients with elevated serum GGT levels.ResultsSerum GGT levels were found to be elevated in a higher proportion in patients with either small or large HCC than alpha-fetoprotein (AFP) levels, and were significantly related to prognosis in patients with large size HCCs. There was no clear correlation between GGT and AFP levels, likely reflecting different HCC characteristics or HCC cell lineages associated with these two markers. Furthermore, elevated GGT was found in 24% of low-AFP patients with small tumors and 46% with large tumors. Elevated GGT levels were also significantly associated with microvascular invasion and tumor diameter.ConclusionsElevated serum GGT levels were associated with HCC size and worse survival, and were unrelated to AFP levels. GGT may be a useful prognostic tumor marker, especially for low-AFP HCC patients.
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Affiliation(s)
- Volkan Ince
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Brian I. Carr
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Harika Gozukara Bag
- Department of Biostatistics, Medical School, Inonu University, Malatya, Turkey
| | - Cemalettin Koc
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Sertac Usta
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Veysel Ersan
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Adil Baskiran
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Tevfik Tolga Sahin
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
| | - Sezai Yilmaz
- Department of Surgery, Liver Transplantation Institute, Inonu University, Malatya, Turkey
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Abstract
The mercapturic acid pathway is a major route for the biotransformation of xenobiotic and endobiotic electrophilic compounds and their metabolites. Mercapturic acids (N-acetyl-l-cysteine S-conjugates) are formed by the sequential action of the glutathione transferases, γ-glutamyltransferases, dipeptidases, and cysteine S-conjugate N-acetyltransferase to yield glutathione S-conjugates, l-cysteinylglycine S-conjugates, l-cysteine S-conjugates, and mercapturic acids; these metabolites constitute a "mercapturomic" profile. Aminoacylases catalyze the hydrolysis of mercapturic acids to form cysteine S-conjugates. Several renal transport systems facilitate the urinary elimination of mercapturic acids; urinary mercapturic acids may serve as biomarkers for exposure to chemicals. Although mercapturic acid formation and elimination is a detoxication reaction, l-cysteine S-conjugates may undergo bioactivation by cysteine S-conjugate β-lyase. Moreover, some l-cysteine S-conjugates, particularly l-cysteinyl-leukotrienes, exert significant pathophysiological effects. Finally, some enzymes of the mercapturic acid pathway are described as the so-called "moonlighting proteins," catalytic proteins that exert multiple biochemical or biophysical functions apart from catalysis.
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Affiliation(s)
- Patrick E Hanna
- Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - M W Anders
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, USA
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Abstract
The expression of gamma-glutamyl transpeptidase (GGT) is essential to maintaining cysteine levels in the body. GGT is a cell surface enzyme that hydrolyzes the gamma-glutamyl bond of extracellular reduced and oxidized glutathione, initiating their cleavage into glutamate, cysteine (cystine), and glycine. GGT is normally expressed on the apical surface of ducts and glands, salvaging the amino acids from glutathione in the ductal fluids. GGT in tumors is expressed over the entire cell membrane and provides tumors with access to additional cysteine and cystine from reduced and oxidized glutathione in the blood and interstitial fluid. Cysteine is rate-limiting for glutathione synthesis in cells under oxidative stress. The induction of GGT is observed in tumors with elevated levels of intracellular glutathione. Studies in models of hepatocarcinogenesis show that GGT expression in foci of preneoplastic hepatocytes provides a selective advantage to the cells during tumor promotion with agents that deplete intracellular glutathione. Similarly, expression of GGT in tumors enables cells to maintain elevated levels of intracellular glutathione and to rapidly replenish glutathione during treatment with prooxidant anticancer therapy. In the clinic, the expression of GGT in tumors is correlated with drug resistance. The inhibitors of GGT block GGT-positive tumors from accessing the cysteine in extracellular glutathione. They also inhibit GGT activity in the kidney, which results in the excretion of GSH in the urine and a rapid decrease in blood cysteine levels, leading to depletion of intracellular GSH in both GGT-positive and GGT-negative tumors. GGT inhibitors are being developed for clinical use to sensitize tumors to chemotherapy.
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Affiliation(s)
- Marie H Hanigan
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
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4
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Kishi M, Emi Y, Sakaguchi M, Ikushiro SI, Iyanagi T. Ontogenic isoform switching of UDP–glucuronosyltransferase family 1 in rat liver. Biochem Biophys Res Commun 2008; 377:815-9. [DOI: 10.1016/j.bbrc.2008.10.043] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Accepted: 10/11/2008] [Indexed: 11/16/2022]
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5
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Abstract
gamma-Glutamyltranspeptidase is a heterodimeric glycoprotein that catalyzes the transpeptidation and hydrolysis of the gamma-glutamyl group of glutathione and related compounds. It is known that the enzyme plays a role in the metabolism of glutathione and in salvaging constituents of glutathione. In the adult animal, high levels of gamma-glutamyltranspeptidase are constitutively expressed in the kidney, intestine, and epididymis. On the other hand, although gamma-glutamyltranspeptidase is up-regulated in the liver during the perinatal stage, its expression is nearly undetectable in the adult. In addition, it has long been observed that the intake of certain xenobiotics, including carcinogens and drugs, induces the hepatic expression of the enzyme. This induction seems to be associated with both transcriptional regulation and the growth of certain types of cells in the injured liver. A number of studies have been carried out to explain the mechanism by which gamma-glutamyltranspeptidase expression is regulated. 5'-Untranslated regions of mRNAs of the enzyme differ in a tissue-specific manner but share a common protein coding region, and the tissue-specific and developmental stage-specific expression, as well as hepatic induction, are conferred by different promoters. As suggested by the capability of enzymatic activity-independent induction of osteoclasts, the expression of gamma-glutamyltranspeptidase may also be involved in various biological processes that are not directly associated with glutathione metabolism. This chapter briefly summarizes studies to date concerning the tissue-specific expression and induction of gamma-glutamyltranspeptidase and transcriptional regulation by the multiple promoter system is discussed.
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Affiliation(s)
- Yoshitaka Ikeda
- Division of Molecular Cell Biology, Department of Biomolecular Sciences, Saga University Faculty of Medicine, Japan
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6
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Kirby JL, Yang L, Labus JC, Lye RJ, Hsia N, Day R, Cornwall GA, Hinton BT. Characterization of Epididymal Epithelial Cell-Specific Gene Promoters by In Vivo Electroporation1. Biol Reprod 2004; 71:613-9. [PMID: 15115732 DOI: 10.1095/biolreprod.103.025635] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The mammalian epididymis plays a critical role in sperm maturation, a function dependent on testicular androgens. However, the function of the initial segment, the most proximal part of the epididymis, is also dependent on luminal factors of testicular origin. Efferent duct ligation (EDL), which prevents luminal testicular fluid from reaching the epididymis, results in changes in gene expression within this region. Cystatin-related epididymal spermatogenic (cres) gene and gamma-glutamyl transpeptidase (GGT) mRNA IV are highly expressed in the initial segment and are regulated by luminal testicular factors. EDL results in decreased expression of both genes. To evaluate these promoters in the context of their native physiological state, an in vivo electroporation procedure was used. Significant differences were observed in vivo compared to previous in vitro results. Whereas two C/EBP sites were necessary for transcriptional activity from a 135-base-pair (bp) cres promoter in vitro, only the 5' site displayed functional activity in the in vivo system. A 135-bp GGT promoter IV construct was sufficient for reporter gene expression in vitro. However, in vivo, substantial expression was not observed until the construct was extended to 530 bp. Three polyoma enhancer activator 3 (PEA3) sites were found to be necessary for in vivo reporter gene expression from this construct. A cis-acting negative regulatory element between -530 and -681 bp was also identified that was not previously recognized in the in vitro studies. These studies demonstrate the utility of in vivo electroporation for elucidating promoter elements that may not be identified when traditional in vitro methods are used.
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Affiliation(s)
- Jennifer L Kirby
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA 22908, USA
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7
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Abstract
The mechanisms of thiol metabolism and chemistry have particular relevance to both cellular defenses against toxicant exposure and to redox signaling. Here, we will focus on glutathione (GSH), the major endogenous low- molecular-weight nonprotein thiol synthesized de novo in mammalian cells. The major pathways for GSH metabolism in defense of the cell are reduction of hydroperoxides by glutathione peroxidases (GSHPx) and some peroxiredoxins, which yield glutathione disulfide (GSSG), and conjugation reactions catalyzed by glutathione-S-transferases. GSSG can be reduced to GSH by glutathione reductase, but glutathione conjugates are excreted from cells. The exoenzyme gamma-glutamyltranspeptidase (GGT) removes the glutamate from extracellular GSH, producing cysteinyl-glycine from which a dipeptidase then generates cysteine, an amino acid often limiting for de novo GSH synthesis. Synthesis of GSH from the constituent amino acids occurs in two regulated, enzymatically catalyzed steps. The signaling pathways leading to activation of the transcription factors that regulate these genes are a current area of intense investigation. The elucidation of the signaling for GSH biosynthesis in human bronchial epithelial cells in response to 4-hydroxynonenal (4HNE), an end product of lipid peroxidation, will be used as an example. GSH also participates in redox signaling through the removal of H(2)O(2), which has the properties of a second messenger, and by reversing the formation of sulfenic acid, a moiety formed by reaction of critical cysteine residues in signaling proteins with H(2)O(2). Disruption of GSH metabolism will therefore have major a impact upon function of cells in terms of both defense and normal physiology.
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Affiliation(s)
- Dale A Dickinson
- Department of Environmental Health Sciences, School of Public Health, and Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA
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8
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Mikkelsen IM, Huseby NE, Visvikis A, Moens U. Activation of the gamma-glutamyltransferase promoter 2 in the rat colon carcinoma cell line CC531 by histone deacetylase inhibitors is mediated through the Sp1 binding motif. Biochem Pharmacol 2002; 64:307-15. [PMID: 12123752 DOI: 10.1016/s0006-2952(02)01116-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The single-copy gene for rat gamma-glutamyltransferase (GGT) encodes at least seven distinct mRNAs that differ in their 5'-untranslated regions only. Tissue- and developmental-specific expression of GGT is partly achieved by the presence of many transcription factor-binding sites in the promoters of this gene. In an earlier study we found that GGT mRNAs II and IV levels were increased upon butyrate-induced differentiation of the rat colon carcinoma cell line CC531. The mechanism for this butyrate-induced upregulation remains unknown, but may result from altered promoter activity as butyrate is a known histone deacetylase inhibitor. In the present study, we show by transient transfection studies that butyrate enhanced the expression of the luciferase reporter gene driven by the rat GGT promoter 2 (P2). Trichostatine A (TSA), another histone deacetylase inhibitor, also enhanced transcription from this promoter. The role of the transcription factor site Sp1 in butyrate- or TSA-induced activation of the GGT P2 was examined as Sp1 has been previously shown to play a central role in the transcriptional activation of other genes during butyrate and TSA stimulation. A triple sequence-motif of this isolated Sp1 site linked to a minimal promoter was able to mediate butyrate- and TSA-induced expression of the luciferase reporter gene, while no effect was measured using the minimal promoter alone. Deleting the Sp1 site in the context of the rat GGT P2 strongly reduced the basal transcription activity and abrogated butyrate- and TSA-induced activation of the mutated promoter. These results suggest that butyrate- or TSA-induced activation of the rat GGT P2 can be mediated by a Sp1 binding motif.
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Affiliation(s)
- Idun Merete Mikkelsen
- Department of Medical Biochemistry, Institute of Medical Biology, Faculty of Medicine, University of Tromsø, N-9037 Tromsø, Norway.
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9
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Gupta S, Rajvanshi P, Malhi H, Slehria S, Sokhi RP, Vasa SR, Dabeva M, Shafritz DA. Cell transplantation causes loss of gap junctions and activates GGT expression permanently in host liver. Am J Physiol Gastrointest Liver Physiol 2000; 279:G815-26. [PMID: 11005770 DOI: 10.1152/ajpgi.2000.279.4.g815] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Cell transplantation into hepatic sinusoids, which is necessary for liver repopulation, could cause hepatic ischemia. To examine the effects of cell transplantation on host hepatocytes, we transplanted Fisher 344 rat hepatocytes into syngeneic dipeptidyl peptidase IV-deficient rats. Within 24 h of cell transplantation, areas of ischemic necrosis, along with transient disruption of gap junctions, appeared in the liver. Moreover, host hepatocytes expressed gamma-glutamyl transpeptidase (GGT) extensively, which was observed even 2 years after cell transplantation. GGT expression was not associated with alpha-fetoprotein activation, which is present in progenitor cells. Increased GGT expression was apparent after transplantation of nonparenchymal cells and latex beads but not after injection of saline, fragmented hepatocytes, hepatocyte growth factor, or turpentine. Some host hepatocytes exhibited apoptosis, as well as DNA synthesis, between 24 and 48 h after cell transplantation. Changes in gap junctions, GGT expression, DNA synthesis, and apoptosis after cell transplantation were prevented by vasodilators. The findings indicated the onset of ischemic liver injury after cell transplantation. These hepatic perturbations must be considered when transplanted cells are utilized as reporters for biological studies.
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Affiliation(s)
- S Gupta
- Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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10
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Holic N, Suzuki T, Corlu A, Couchie D, Chobert MN, Guguen-Guillouzo C, Laperche Y. Differential expression of the rat gamma-glutamyl transpeptidase gene promoters along with differentiation of hepatoblasts into biliary or hepatocytic lineage. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 157:537-48. [PMID: 10934156 PMCID: PMC1850145 DOI: 10.1016/s0002-9440(10)64564-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
gamma-Glutamyl transpeptidase (GGT), a major enzyme of glutathione (GSH) homeostasis, is often used as a biliary marker to follow the differentiation of hepatic precursor cells. The expression of the GGT gene is driven by different promoters and yields multiple mRNAs, depending on the cell type or the stage of differentiation. In the present study, we analyzed the GGT mRNA expression pattern by quantitative reverse transcriptase-polymerase chain reaction or by in situ hybridization i) in the liver, in vivo, at early stages of development; ii) in oval cells, which proliferate and differentiate into hepatocytes in response to galactosamine injury in vivo; and finally, iii) during hepatoblast differentiation, in vitro. We show that GGT gene transcription originates from promoters P3, P4, and P5 in rat hepatic precursor cells. Differentiation of these cells induces profound alterations in GGT gene expression, leading to extinction of promoters P4 and P5, when they differentiate into the hepatocytic pathway, and to extinction of promoters P3 and P5 when they differentiate into the biliary pathway. This diversity in GGT mRNA expression provides unique molecular probes to follow hepatic precursor cell differentiation. Furthermore, the identification of factors governing GGT P5 and P4 promoter expression should provide further insight into the molecular events that occur as the liver precursor cell differentiates into the hepatic lineages.
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Affiliation(s)
- N Holic
- Institut National de la Santé et de la Recherche Médicale Unite 99, Hôpital Henri Mondor, Université Paris XII, Créteil. Hôpital Pontchaillou, Rennes, France
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11
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Horio J, Nomura S, Okada M, Katsumata Y, Nakanishi Y, Kumano Y, Takami S, Kinoshita M, Tsujimoto M, Nakazato H, Mizutani S. Structural organization of the 5'-end and chromosomal assignment of human placental leucine aminopeptidase/insulin-regulated membrane aminopeptidase gene. Biochem Biophys Res Commun 1999; 262:269-74. [PMID: 10448104 DOI: 10.1006/bbrc.1999.1184] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Placental leucine aminopeptidase (P-LAP) which is identical with cystine aminopeptidase as oxytocinase was found to be a homologue of rat insulin-regulated membrane aminopeptidase (IRAP) by cDNA cloning. In this study, we confirmed 5'-end cDNA sequence of P-LAP and isolated genomic clones containing the upstream region of human P-LAP gene. The transcription initiation sites determined by primer extension located 478 and 480 bp upstream of the initiation methionine codon, 38 bp downstream of TATA box-like motif. The 5'-flanking region of human P-LAP gene contained DNA-binding motifs for several ubiquitous transcription factors such as SP1 and AP2. Chromosomal localization by fluorescence in situ hybridization showed that the gene was assigned to 5q14.2-q15 of the human chromosome. This study establishes the genetic basis for P-LAP gene research, thereby leading to better understanding of the molecular mechanism underlying the P-LAP gene.
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Affiliation(s)
- J Horio
- Department of Obstetrics and Gynecology, Nagoya University School of Medicine, Nagoya, 466-8550, Japan
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12
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Chikhi N, Holic N, Guellaen G, Laperche Y. Gamma-glutamyl transpeptidase gene organization and expression: a comparative analysis in rat, mouse, pig and human species. Comp Biochem Physiol B Biochem Mol Biol 1999; 122:367-80. [PMID: 10392451 DOI: 10.1016/s0305-0491(99)00013-9] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Gamma-glutamyl transpeptidase (GGT) is an enzyme located at the external surface of epithelial cells. It initiates extracellular glutathione (GSH) breakdown, provides cells with a local cysteine supply and contributes to maintain intracellular GSH level. GGT expression, highly sensitive to oxidative stress, is a part of the cell antioxidant defense mechanisms. We describe recent advances in GGT gene structure and expression knowledge and put emphasis on the complex transcriptional organization of that gene and its conservation among different species. GGT gene structure has been elucidated in rat and mouse where a single gene is transcribed from multiple promoters into several transcripts which finally yield a unique polypeptidic chain. Analysis of rat, mouse, human and pig cDNA and gene sequences reveals a large conservation of the transcriptional organization of that gene. This complex structure provides flexibility in GGT expression controlled at the promoter level, through multiple regulatory sites, and at RNA level by alternate 5' untranslated sequences which may create a diversity in the stability and translational efficiency of the different transcripts. In conclusion, transcription of the GGT gene from several promoters offers multiple DNA and RNA targets for various oxidative stimuli and contributes to a broad antioxidant cell defense through GGT induction and subsequent cysteine supply from extracellular glutathione.
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Affiliation(s)
- N Chikhi
- INSERM Unité 99, Université Paris XII, Hôpital Henri Mondor, Créteil, France
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13
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Lan ZJ, Lye RJ, Holic N, Labus JC, Hinton BT. Involvement of polyomavirus enhancer activator 3 in the regulation of expression of gamma-glutamyl transpeptidase messenger ribonucleic acid-IV in the rat epididymis. Biol Reprod 1999; 60:664-73. [PMID: 10026114 DOI: 10.1095/biolreprod60.3.664] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Gamma-glutamyl transpeptidase (GGT) mRNA-IV and polyomavirus enhancer activator 3 (PEA3) mRNA are highly expressed in the initial segment of the rat epididymis, and both are regulated by testicular factors. PEA3 protein in rat initial segment nuclear extracts has been shown to bind to a PEA3/Ets binding motif, which is derived from the partially characterized GGT mRNA-IV promoter region. This suggests that PEA3 may be involved in regulating transcription from the rat GGT mRNA-IV gene promoter in the initial segment. Using DNA oligonucleotide primers and DNA sequencing analysis, an approximately 1500-basepair (bp) DNA sequence at the 5' region of the promoter was obtained. Using transient transfection, PEA3 activated transcription of the rat GGT mRNA-IV promoter only in cultured epididymal cells from the rat initial segment, but not in Cos-1 or NRK-52E cells. Promoter deletion analysis indicated that a PEA3/Ets binding motif between nucleotides -22 and -17 is the functional site for PEA3 to activate transcription of GGT promoter IV and that an adjacent Sp1 binding motif is also required to maintain promoter IV activity in epididymal cells. Transcriptional activation of promoter IV was shown to be epididymal cell-specific and PEA3-specific. In addition, PEA3 may act as a weak repressor for transcription of promoter IV, probably using a PEA3/Ets binding motif(s) distal to the transcription start site. A model of how PEA3 is involved in the regulation of transcription of GGT promoter IV in epididymal cells is proposed.
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Affiliation(s)
- Z J Lan
- Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA
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14
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Taniguchi N, Ikeda Y. gamma-Glutamyl transpeptidase: catalytic mechanism and gene expression. ADVANCES IN ENZYMOLOGY AND RELATED AREAS OF MOLECULAR BIOLOGY 1998; 72:239-78. [PMID: 9559055 DOI: 10.1002/9780470123188.ch7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The gamma-glutamyl transpeptidases are key enzymes in the so-called gamma-glutamyl cycle involving glutathione synthesis, the recovery of its constituents, and in the transport of amino acids. This membrane-bound ectoenzyme thus serves to regulate glutathione synthesis. This chapter deals with the active site chemistry of gamma-glutamyl transpeptidase, including the role of side-chain groups on the light subunit as well as several serine residues in the catalytic process. Also considered are genomic studies indicating (a) the presence of a single gene in mouse and rat; (b) the occurrence of multiple genes in humans; (c) the involvement of multiple promoters for gene expression; and (d) how these multiple promoters may play a role in the tissue-specific expression of gamma-glutamyl transpeptidases.
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Affiliation(s)
- N Taniguchi
- Department of Biochemistry, Osaka University Medical School, Japan
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15
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Hanigan MH. gamma-Glutamyl transpeptidase, a glutathionase: its expression and function in carcinogenesis. Chem Biol Interact 1998; 111-112:333-42. [PMID: 9679564 DOI: 10.1016/s0009-2797(97)00170-1] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
gamma-Glutamyl transpeptidase (GGT) is found throughout the plant and animal kingdoms. It is a cell surface glycoprotein that cleaves gamma-glutamyl amide bonds. The most abundant physiologic substrates for the enzyme are glutathione and glutathione-conjugated compounds. GGT initiates the cleavage of extracellular glutathione into its constituent amino acids which can then be transported into the cell. It also catalyzes the initial step in the conversion of glutathione-conjugated compounds to mercapturic acids. GGT is expressed at high levels in many human tumors and in many carcinogen-induced tumors in animals. These observations have lead an increased focus on the role of the enzyme in the development and treatment of tumors. This chapter begins with an overview of the structure and function of GGT in normal tissues. A summary of its expression in neoplastic tissues and the ways in which GGT effects the response of tumors to chemotherapy follows. The chapter concludes with a discussion of strategies for using GGT to activate and target chemotherapy drugs to tumors as a means of improving treatment for common human malignancies.
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Affiliation(s)
- M H Hanigan
- Department of Cell Biology, School of Medicine, University of Virginia, Charlottesville 22908, USA
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16
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Hudson EA, Munks RJL, Manson MM. Characterization of transcriptional regulation of γ-glutamyl transpeptidase in rat liver involving both positive and negative regulatory elements. Mol Carcinog 1997. [DOI: 10.1002/(sici)1098-2744(199712)20:4<376::aid-mc7>3.0.co;2-h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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17
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Abstract
A recently introduced thermostable RNase H was tested to determine its effectiveness in RNase H mapping reactions. Procedures are described which should have general use with both the thermostable and the Escherichia coli RNase H enzymes. Using the thermostable RNase H at higher temperatures extends the range of oligodeoxyribonucleotide/RNA combinations that yield satisfactory results. Northern blot analyses of total RNA was used to demonstrate that native RNAs can be analyzed by oligodeoxyribonucleotide directed RNase H digestion with minimal sample processing as long as care is taken to maintain thermal stringency both during reaction assembly and termination. Increased thermal stringency allows for higher DNA concentrations to ensure complete site-specific digestion of target RNAs or to permit simultaneous cleavage with multiple oligodeoxyribonucleotides. Partial digests can also be controlled by manipulating oligodeoxyribonucleotide concentrations. In addition, the thermostable RNase H was shown to be active at magnesium ion concentrations as low as 0.1 mM. This allows for optimization of Mg2+ effects on overall sample integrity and DNA/RNA interactions over at least a 20-fold range (2.0-0.1 mM).
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Affiliation(s)
- D Porter
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins 80523-1870, USA
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Takahashi Y, Oakes SM, Williams MC, Takahashi S, Miura T, Joyce-Brady M. Nitrogen dioxide exposure activates gamma-glutamyl transferase gene expression in rat lung. Toxicol Appl Pharmacol 1997; 143:388-96. [PMID: 9144455 DOI: 10.1006/taap.1996.8087] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Exposure to nitrogen dioxide (NO2) has been shown to activate glutathione metabolism in lung and lung lavage. Since GGT is a key enzyme in glutathione metabolism and we have previously characterized GGT expression in distal lung epithelium and in lung surfactant, we examined the NO2 exposed lung for induction of gamma-glutamyl transferase (GGT) mRNA, protein, and enzyme activity. We found that the GGT gene product is induced in lung by NO2. The GGT mRNA level in lung increases 2-fold within 6 hr and 3-fold after 24 hr of exposure to this oxidant gas, and this 3-fold elevation persists even after 14 days of exposure. The pattern of GGT mRNA expression switches from the single GGT mRNA III transcript in the normal lung to the dual expression of GGT mRNA I and mRNA III. Enzyme activity in whole lung increases 1.6- to 2.5-fold while extracellular surfactant-associated GGT activity accumulates 5.5-fold and GGT protein accumulates in lung surfactant. Induction of GGT mRNA and protein is evident in cells of the bronchioles by in situ hybridization and immunolocalization, respectively. In contrast, alveolar type 2 cells lack an in situ hybridization signal and exhibit a reduction in the intensity of immunostaining with prolonged exposure. Our studies show that NO2 induces GGT mRNA expression, including GGT mRNA1, in lung and GGT protein and enzyme activity in lung and lung lavage in response to the oxidative stress of NO2 inhalation.
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Affiliation(s)
- Y Takahashi
- Environmental Health Sciences Division, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan
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Chobert MN, Grondin G, Brouillet A, Laperche Y, Beaudoin AR. Control of gamma-glutamyl transpeptidase expression by glucocorticoids in the rat pancreas. Correlation with granule formation. J Biol Chem 1996; 271:12431-7. [PMID: 8647848 DOI: 10.1074/jbc.271.21.12431] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Glucocorticoids are known to promote the formation of zymogen granules in acinar cells of the exocrine pancreas in vivo as well as in vitro. To gain insight into the mechanism of this regulation, we studied the effects of glucocorticoids on the synthesis of two components of the secretory granule membrane, the glycoprotein 2 (GP-2) and the gamma-glutamyl transpeptidase (GGT). It was demonstrated that following adrenalectomy, degranulation of pancreatic acinar cells is accompanied by a sharp decrease in GGT and GP-2 synthesis as measured by mRNA and protein accumulation. The decline of GGT synthesis was prevented by glucocorticoid replacement therapy, whereas GP-2 synthesis could be maintained with either glucocorticoid or estradiol treatment. These in vivo observations were corroborated and extended in an in vitro study using AR42J pancreatic cells. With this cell line, it was demonstrated that dexamethasone induces the formation of zymogen granules and the accumulation of a specific GGT transcript (mRNA III) by decreasing its degradation rate. At the same time, the GP-2 mRNA level was not modified by the hormonal treatment. These data demonstrate that glucocorticoids exert a positive control on the GGT expression in pancreatic cells at a post-transcriptional level. GGT, an enzyme of the glutathione metabolism, could play a significant role in protein packaging in secretory cells.
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Affiliation(s)
- M N Chobert
- Institut National de la Santé et de la Recherche Mdicale, Unité INSERM 99, Hôpital Henri Mondor, Créteil, France
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Griffiths SA, Good VM, Gordon LA, Hudson EA, Barrett MC, Munks RJ, Manson MM. Characterization of a promoter for gamma-glutamyl transpeptidase activated in rat liver in response to aflatoxin B1 and ethoxyquin. Mol Carcinog 1995; 14:251-62. [PMID: 8519414 DOI: 10.1002/mc.2940140405] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
gamma-Glutamyl transpeptidase (GGT) is normally absent from adult rat hepatocytes but is induced by a range of xenobiotics, including carcinogens and chemoprotective agents. As many as six mRNA species for this enzyme have been described in both rat and mouse, with various degrees of tissue specificity. These originate from one gene and have separate promoters within alternative 5' untranslated sequences. By using a cDNA-derived sequence specific for GGT mRNA III to screen a rat genomic library, a clone that contains the promoter region for this mRNA was isolated and characterized. The transcriptional start site lay some 3.5 kb upstream from that already characterized for mRNA II in rat kidney. Luciferase activity was obtained after transfection of rat hepatoma-derived cell lines with constructs containing the putative promoter III fused to a luc reporter. Although this promoter lacks a TATA box, a sequence close to the start site that binds the transcription factor TFIID in vitro was identified. By using PCR techniques, mRNA III (homologous to both mouse III and IV) and an mRNA (IV) with homology to VI in mouse were found in ethoxyquin- and aflatoxin B1-treated rat liver and kidney as well as in a hepatoma-derived cell line. No evidence was found for a product homologous to mRNA from promoter V described in the mouse.
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Affiliation(s)
- S A Griffiths
- MRC Toxicology Unit, University of Leicester, United Kingdom
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Habib GM, Carter BZ, Sepulveda AR, Shi ZZ, Wan DF, Lebovitz RM, Lieberman MW. Identification of a sixth promoter that directs the transcription of gamma-glutamyl transpeptidase type III RNA in mouse. J Biol Chem 1995; 270:13711-5. [PMID: 7775425 DOI: 10.1074/jbc.270.23.13711] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
We have previously identified five promoters in the 5'-flanking region of the mouse gamma-glutamyl transpeptidase (gamma GT) gene. We now report the localization of a sixth promoter that supports the transcription of type III RNA, the major gamma GT RNA in fetal liver. We made a fetal liver cDNA library enriched for gamma GT RNA and obtained 12 gamma GT type III-specific clones. The longest clone is consistent with a transcription start site for type III RNA at a position 5' to the type IV promoter and about 5 kilobase(s) (kb) 5' to the first coding exon. We estimated by ribonuclease protection assay that about 80% of the gamma GT mRNA in fetal liver was type III. Primer extension and nuclease protection analyses mapped the 5' end of type III mRNA in fetal liver and kidney to a single cluster of potential major and minor transcription start sites. Deletion analysis using transient expression of chloramphenicol acetyltransferase constructs of the type III promoter region revealed the greatest activity with a 1-kb 5'-flanking fragment in mouse kidney proximal tubular cells and no detectable activity in NIH-3T3 fibroblasts. These studies demonstrate that the type III 5' region of the mouse gamma GT gene is organized into two distinct exons (IIIa and IIIb) and that type III RNA is expressed under the control of its own promoter.
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Affiliation(s)
- G M Habib
- Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA
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