1
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Mullen NJ, Thakur R, Shukla SK, Chaika NV, Kollala SS, Wang D, He C, Fujii Y, Sharma S, Mulder SE, Sykes DB, Singh PK. ENT1 blockade by CNX-774 overcomes resistance to DHODH inhibition in pancreatic cancer. Cancer Lett 2023; 552:215981. [PMID: 36341997 PMCID: PMC10305837 DOI: 10.1016/j.canlet.2022.215981] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 10/19/2022] [Accepted: 10/20/2022] [Indexed: 11/23/2022]
Abstract
Inhibitors of dihydroorotate dehydrogenase (DHODH), a key enzyme for de novo synthesis of pyrimidine nucleotides, have failed in clinical trials for various cancers despite robust efficacy in preclinical animal models. To probe for druggable mediators of DHODH inhibitor resistance, we performed a combination screen with a small molecule library against pancreatic cancer cell lines that are highly resistant to the DHODH inhibitor brequinar (BQ). The screen revealed that CNX-774, a preclinical Bruton tyrosine kinase (BTK) inhibitor, sensitizes resistant cell lines to BQ. Mechanistic studies showed that this effect is independent of BTK and instead results from inhibition of equilibrative nucleoside transporter 1 (ENT1) by CNX-774. We show that ENT1 mediates BQ resistance by taking up extracellular uridine, which is salvaged to generate pyrimidine nucleotides in a DHODH-independent manner. In BQ-resistant cell lines, BQ monotherapy slowed proliferation and caused modest pyrimidine nucleotide depletion, whereas combination treatment with BQ and CNX-774 led to profound cell viability loss and pyrimidine starvation. We also identify N-acetylneuraminic acid accumulation as a potential marker of the therapeutic efficacy of DHODH inhibitors. In an aggressive, immunocompetent pancreatic cancer mouse model, combined targeting of DHODH and ENT1 dramatically suppressed tumor growth and prolonged mouse survival. Overall, our study defines CNX-774 as a previously uncharacterized ENT1 inhibitor and provides strong proof of concept support for dual targeting of DHODH and ENT1 in pancreatic cancer.
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Affiliation(s)
- Nicholas J Mullen
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Ravi Thakur
- Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA
| | - Surendra K Shukla
- Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA
| | - Nina V Chaika
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Sai Sundeep Kollala
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Dezhen Wang
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - Chunbo He
- Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA
| | - Yuki Fujii
- Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA
| | - Shikhar Sharma
- Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA
| | - Scott E Mulder
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA
| | - David B Sykes
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, USA; Harvard Stem Cell Institute, Cambridge, MA, 02114, USA
| | - Pankaj K Singh
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE, 68198, USA; Department of Oncology Science, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73014, USA; OU Health Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA.
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2
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A point-mutation in the C-domain of CMP-sialic acid synthetase leads to lethality of medaka due to protein insolubility. Sci Rep 2021; 11:23211. [PMID: 34853329 PMCID: PMC8636478 DOI: 10.1038/s41598-021-01715-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 10/05/2021] [Indexed: 01/22/2023] Open
Abstract
Vertebrate CMP-sialic acid synthetase (CSS), which catalyzes the synthesis of CMP-sialic acid (CMP-Sia), consists of a 28 kDa-N-domain and a 20 kDa-C-domain. The N-domain is known to be a catalytic domain; however, the significance of the C-domain still remains unknown. To elucidate the function of the C-domain at the organism level, we screened the medaka TILLING library and obtained medaka with non-synonymous mutations (t911a), or single amino acid substitutions of CSS, L304Q, in the C-domain. Prominently, most L304Q medaka was lethal within 19 days post-fertilization (dpf). L304Q young fry displayed free Sia accumulation, and impairment of sialylation, up to 8 dpf. At 8 dpf, a marked abnormality in ventricular contraction and skeletal myogenesis was observed. To gain insight into the mechanism of L304Q-induced abnormalities, L304Q was biochemically characterized. Although bacterially expressed soluble L304Q and WT showed the similar Vmax/Km values, very few soluble L304Q was detected when expressed in CHO cells in sharp contrast to the WT. Additionally, the thermostability of various mutations of L304 greatly decreased, except for WT and L304I. These results suggest that L304 is important for the stability of CSS, and that an appropriate level of expression of soluble CSS is significant for animal survival.
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3
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Ryckman AE, Brockhausen I, Walia JS. Metabolism of Glycosphingolipids and Their Role in the Pathophysiology of Lysosomal Storage Disorders. Int J Mol Sci 2020; 21:E6881. [PMID: 32961778 PMCID: PMC7555265 DOI: 10.3390/ijms21186881] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 09/04/2020] [Accepted: 09/12/2020] [Indexed: 12/11/2022] Open
Abstract
Glycosphingolipids (GSLs) are a specialized class of membrane lipids composed of a ceramide backbone and a carbohydrate-rich head group. GSLs populate lipid rafts of the cell membrane of eukaryotic cells, and serve important cellular functions including control of cell-cell signaling, signal transduction and cell recognition. Of the hundreds of unique GSL structures, anionic gangliosides are the most heavily implicated in the pathogenesis of lysosomal storage diseases (LSDs) such as Tay-Sachs and Sandhoff disease. Each LSD is characterized by the accumulation of GSLs in the lysosomes of neurons, which negatively interact with other intracellular molecules to culminate in cell death. In this review, we summarize the biosynthesis and degradation pathways of GSLs, discuss how aberrant GSL metabolism contributes to key features of LSD pathophysiology, draw parallels between LSDs and neurodegenerative proteinopathies such as Alzheimer's and Parkinson's disease and lastly, discuss possible therapies for patients.
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Affiliation(s)
| | - Inka Brockhausen
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 2V5, Canada;
| | - Jagdeep S. Walia
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, ON K7L 2V5, Canada;
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4
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Fang M, Xu X, Zhang M, Shi Y, Gu G, Liu W, Class B, Ciccone C, Gahl WA, Huizing M, Carrillo N, Wang AQ. Quantitation of cytidine-5'-monophospho-N-acetylneuraminic acid in human leukocytes using LC-MS/MS: method development and validation. Biomed Chromatogr 2020; 34:e4735. [PMID: 31691999 DOI: 10.1002/bmc.4735] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/18/2019] [Accepted: 10/21/2019] [Indexed: 11/06/2022]
Abstract
The biosynthesis of sialic acid (Neu5Ac) leads to the intracellular production of cytidine-5'-monophospho-N-acetylneuraminic acid (CMP-Neu5Ac), the active sialic acid donor to nascent glycans (glycoproteins and glycolipids) in the Golgi. UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase myopathy is a rare autosomal recessive muscular disease characterized by progressive muscle weakness and atrophy. To quantify the intracellular levels of CMP-Neu5Ac as well as N-acetylmannosamine (ManNAc) and Neu5Ac in human leukocytes, we developed and validated robust liquid chromatography-tandem mass spectrometry methods. A fit-for-purpose approach was implemented for method validation. Hydrophilic interaction chromatography was used to retain three hydrophilic analytes. The human leukocyte pellets were lysed and extracted in a methanol-water mixture and the leukocyte extract was used for LC-MS/MS analysis. The lower limits of quantitation for ManNAc, Neu5Ac and CMP-Neu5Ac were 25.0, 25.0 and 10.0 ng/ml, respectively. These validated methods were applied to a clinical study.
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Affiliation(s)
- Meng Fang
- Alliance Pharma, 17 Lee Boulevard, Malvern, PA, USA
| | - Xin Xu
- Therapeutic Development Branch, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, USA
| | | | - Yifan Shi
- Alliance Pharma, 17 Lee Boulevard, Malvern, PA, USA
| | - Guodong Gu
- Alliance Pharma, 17 Lee Boulevard, Malvern, PA, USA
| | - Wanjing Liu
- Alliance Pharma, 17 Lee Boulevard, Malvern, PA, USA
| | - Bradley Class
- Medical Genetics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Carla Ciccone
- Medical Genetics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - William A Gahl
- Medical Genetics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Marjan Huizing
- Medical Genetics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Nuria Carrillo
- Medical Genetics Branch, National Human Genome Research Institute, Bethesda, MD, USA
| | - Amy Q Wang
- Therapeutic Development Branch, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, USA
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5
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Matthews MM, McArthur JB, Li Y, Yu H, Chen X, Fisher AJ. Catalytic Cycle of Neisseria meningitidis CMP-Sialic Acid Synthetase Illustrated by High-Resolution Protein Crystallography. Biochemistry 2019; 59:3157-3168. [PMID: 31583886 DOI: 10.1021/acs.biochem.9b00517] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytidine 5'-monophosphate (CMP)-sialic acid synthetase (CSS) is an essential enzyme involved in the biosynthesis of carbohydrates and glycoconjugates containing sialic acids, a class of α-keto acids that are generally terminal key recognition residues by many proteins that play important biological and pathological roles. The CSS from Neisseria meningitidis (NmCSS) has been commonly used with other enzymes such as sialic acid aldolase and/or sialyltransferase in synthesizing a diverse array of compounds containing sialic acid or its naturally occurring and non-natural derivatives. To better understand its catalytic mechanism and substrate promiscuity, four NmCSS crystal structures trapped at various stages of the catalytic cycle with bound substrates, substrate analogues, and products have been obtained and are presented here. These structures suggest a mechanism for an "open" and "closed" conformational transition that occurs as sialic acid binds to the NmCSS/cytidine-5'-triphosphate (CTP) complex. The closed conformation positions critical residues to help facilitate the nucleophilic attack of sialic acid C2-OH to the α-phosphate of CTP, which is also aided by two observed divalent cations. Product formation drives the active site opening, promoting the release of products.
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Affiliation(s)
- Melissa M Matthews
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - John B McArthur
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Yanhong Li
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Hai Yu
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Xi Chen
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Andrew J Fisher
- Department of Chemistry, University of California, Davis, California 95616, United States.,Department of Molecular and Cellular Biology, University of California, Davis, California 95616, United States
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6
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Niculovic KM, Blume L, Wedekind H, Kats E, Albers I, Groos S, Abeln M, Schmitz J, Beuke E, Bräsen JH, Melk A, Schiffer M, Weinhold B, Münster-Kühnel AK. Podocyte-Specific Sialylation-Deficient Mice Serve as a Model for Human FSGS. J Am Soc Nephrol 2019; 30:1021-1035. [PMID: 31040189 DOI: 10.1681/asn.2018090951] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 02/26/2019] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The etiology of steroid-resistant nephrotic syndrome, which manifests as FSGS, is not completely understood. Aberrant glycosylation is an often underestimated factor for pathologic processes, and structural changes in the glomerular endothelial glycocalyx have been correlated with models of nephrotic syndrome. Glycans are frequently capped by sialic acid (Sia), and sialylation's crucial role for kidney function is well known. Human podocytes are highly sialylated; however, sialylation's role in podocyte homeostasis remains unclear. METHODS We generated a podocyte-specific sialylation-deficient mouse model (PCmas-/- ) by targeting CMP-Sia synthetase, and used histologic and ultrastructural analysis to decipher the phenotype. We applied CRISPR/Cas9 technology to generate immortalized sialylation-deficient podocytes (asialo-podocytes) for functional studies. RESULTS Progressive loss of sialylation in PCmas-/- mice resulted in onset of proteinuria around postnatal day 28, accompanied by foot process effacement and loss of slit diaphragms. Podocyte injury led to severe glomerular defects, including expanded capillary lumen, mesangial hypercellularity, synechiae formation, and podocyte loss. In vivo, loss of sialylation resulted in mislocalization of slit diaphragm components, whereas podocalyxin localization was preserved. In vitro, asialo-podocytes were viable, able to proliferate and differentiate, but showed impaired adhesion to collagen IV. CONCLUSIONS Loss of cell-surface sialylation in mice resulted in disturbance of podocyte homeostasis and FSGS development. Impaired podocyte adhesion to the glomerular basement membrane most likely contributed to disease development. Our data support the notion that loss of sialylation might be part of the complex process causing FSGS. Sialylation, such as through a Sia supplementation therapy, might provide a new therapeutic strategy to cure or delay FSGS and potentially other glomerulopathies.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Esther Beuke
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany; and
| | - Jan H Bräsen
- Nephropathology Unit, Institute of Pathology, and
| | - Anette Melk
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany; and
| | - Mario Schiffer
- Department of Nephrology and Hypertension, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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7
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Unique nuclear localization of Nile tilapia ( Oreochromis niloticus ) Neu4 sialidase is regulated by nuclear transport receptor importin α/β. Biochimie 2018; 149:92-104. [DOI: 10.1016/j.biochi.2018.04.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 04/04/2018] [Indexed: 02/02/2023]
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8
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Di W, Fujita A, Hamaguchi K, Delannoy P, Sato C, Kitajima K. Diverse subcellular localizations of the insect CMP-sialic acid synthetases. Glycobiology 2018; 27:329-341. [PMID: 27986833 DOI: 10.1093/glycob/cww128] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 12/07/2016] [Indexed: 11/12/2022] Open
Abstract
The occurrence and biological importance of sialic acid (Sia) and its metabolic enzymes in insects have been studied using Drosophila melanogaster. The most prominent feature of D. melanogaster CMP-Sia synthetase (DmCSS) is its Golgi-localization, contrasted with nuclear localization of vertebrate CSSs. However, it remains unclear if the Golgi-localization is common to other insect CSSs and why it happens. To answer these questions, Aedes aegypti (mosquito) CSS (AaCSS) and Tribolium castaneum (beetle) CSS (TcCSS) were cloned and characterized for their activity and subcellular localization. Our new findings show: (1) AaCSS and TcCSS share a common overall structure with DmCSS in terms of evolutionarily conserved motifs and the absence of the C-terminal domain typical to vertebrate CSSs; (2) when expressed in mammalian and insect cells, AaCSS and TcCSS showed in vivo and in vitro CSS activities, similar to DmCSS. In contrast, when expressed in bacteria, they lacked CSS activity because the N-terminal hydrophobic region appeared to induce protein aggregation; (3) when expressed in Drosophila S2 cells, AaCSS and TcCSS were predominantly localized in the ER, but not in the Golgi. Surprisingly, DmCSS was mainly secreted into the culture medium, although partially detected in Golgi. Consistent with these results, the N-terminal hydrophobic regions of AaCSS and TcCSS functioned as a signal peptide to render them soluble in the ER, while the N-terminus of DmCSS functioned as a membrane-spanning region of type II transmembrane proteins whose cytosolic KLK sequence functioned as an ER export signal. Accordingly, the differential subcellular localization of insect CSSs are distinctively more diverse than previously recognized.
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Affiliation(s)
- Wu Di
- Bioscience and Biotechnology Center, and Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.,Program for Leading Graduate Schools, Integrative Graduate Education and Research Program in Green Natural Sciences, Nagoya University, Nagoya, Japan
| | - Akiko Fujita
- Bioscience and Biotechnology Center, and Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Kayo Hamaguchi
- Bioscience and Biotechnology Center, and Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Philippe Delannoy
- University of Lille, CNRS, UMR 8576-UGS-Unité de Glycobiologie Structurale et Fonctionnelle, Lille, France
| | - Chihiro Sato
- Bioscience and Biotechnology Center, and Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.,Program for Leading Graduate Schools, Integrative Graduate Education and Research Program in Green Natural Sciences, Nagoya University, Nagoya, Japan
| | - Ken Kitajima
- Bioscience and Biotechnology Center, and Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.,Program for Leading Graduate Schools, Integrative Graduate Education and Research Program in Green Natural Sciences, Nagoya University, Nagoya, Japan
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9
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Abeln M, Borst KM, Cajic S, Thiesler H, Kats E, Albers I, Kuhn M, Kaever V, Rapp E, Münster-Kühnel A, Weinhold B. Sialylation Is Dispensable for Early Murine Embryonic Development in Vitro. Chembiochem 2017; 18:1305-1316. [PMID: 28374933 PMCID: PMC5502888 DOI: 10.1002/cbic.201700083] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Indexed: 12/19/2022]
Abstract
The negatively charged nonulose sialic acid (Sia) is essential for murine development in vivo. In order to elucidate the impact of sialylation on differentiation processes in the absence of maternal influences, we generated mouse embryonic stem cell (mESC) lines that lack CMP‐Sia synthetase (CMAS) and thereby the ability to activate Sia to CMP‐Sia. Loss of CMAS activity resulted in an asialo cell surface accompanied by an increase in glycoconjugates with terminal galactosyl and oligo‐LacNAc residues, as well as intracellular accumulation of free Sia. Remarkably, these changes did not impact intracellular metabolites or the morphology and transcriptome of pluripotent mESC lines. Moreover, the capacity of Cmas−/− mESCs for undirected differentiation into embryoid bodies, germ layer formation and even the generation of beating cardiomyocytes provides first and conclusive evidence that pluripotency and differentiation of mESC in vitro can proceed in the absence of (poly)sialoglycans.
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Affiliation(s)
- Markus Abeln
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Kristina M Borst
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Samanta Cajic
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106, Magdeburg, Germany
| | - Hauke Thiesler
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Elina Kats
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Iris Albers
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Maike Kuhn
- TWINCORE Centre for Experimental and Clinical Infection Research GmbH, A joint venture between Hannover Medical School, Feodor-Lynen-Strasse 7, 30625, Hannover, Germany.,Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124, Braunschweig, Germany
| | - Volkhard Kaever
- Research Core Unit Metabolomics, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Erdmann Rapp
- Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, 39106, Magdeburg, Germany.,glyXera GmbH, Leipziger Strasse 44, 39120, Magdeburg, Germany
| | - Anja Münster-Kühnel
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
| | - Birgit Weinhold
- Institute of Clinical Biochemistry, Hannover Medical School, Carl-Neuberg-Strasse 1, 30625, Hannover, Germany
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10
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Ketterer MR, Rice PA, Gulati S, Kiel S, Byerly L, Fortenberry JD, Soper DE, Apicella MA. Desialylation of Neisseria gonorrhoeae Lipooligosaccharide by Cervicovaginal Microbiome Sialidases: The Potential for Enhancing Infectivity in Men. J Infect Dis 2016; 214:1621-1628. [PMID: 27471322 DOI: 10.1093/infdis/jiw329] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/07/2016] [Indexed: 12/22/2022] Open
Abstract
Previous studies have demonstrated that Neisseria gonorrhoeae sialylates the terminal N-acetyllactosamine present on its lipooligosaccharide (LOS) by acquiring CMP-N-acetyl-5-neuraminic acid upon entering human cells during infection. This renders the organism resistant to killing by complement in normal human serum. N-acetyllactosamine residues on LOS must be free of N-acetyl-5-neuraminc acid (Neu5Ac; also known as "sialic acid") in order for organisms to bind to and enter urethral epithelial cells during infection in men. This raises the question of how the gonococcus infects men if N-acetyllactosamine residues are substituted by Neu5Ac during infection in women. Here, we demonstrate that women with gonococcal infections have levels of sialidases present in cervicovaginal secretions that can result in desialylation of (sialylated) gonococcal LOS. The principle sialidases responsible for this desialylation appear to be bacterial in origin. These studies suggest that members of the cervicovaginal microbiome can modify N. gonorrhoeae, which will enhance successful transmission to men.
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Affiliation(s)
- Margaret R Ketterer
- Department of Microbiology, University of Iowa Carver College of Medicine, Iowa City
| | - Peter A Rice
- Department of Medicine/Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester
| | - Sunita Gulati
- Department of Medicine/Division of Infectious Diseases and Immunology, University of Massachusetts Medical School, Worcester
| | - Steven Kiel
- Department of Microbiology, University of Iowa Carver College of Medicine, Iowa City
| | - Luke Byerly
- Department of Microbiology, University of Iowa Carver College of Medicine, Iowa City
| | | | - David E Soper
- Division of Obstetric and Gynecologic Specialists, Medical College of South Carolina Hospital, Charleston
| | - Michael A Apicella
- Department of Microbiology, University of Iowa Carver College of Medicine, Iowa City
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11
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Sellmeier M, Weinhold B, Münster-Kühnel A. CMP-Sialic Acid Synthetase: The Point of Constriction in the Sialylation Pathway. Top Curr Chem (Cham) 2015; 366:139-67. [PMID: 24141690 DOI: 10.1007/128_2013_477] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Sialoglycoconjugates form the outermost layer of animal cells and play a crucial role in cellular communication processes. An essential step in the biosynthesis of sialylated glycoconjugates is the activation of sialic acid to the monophosphate diester CMP-sialic acid. Only the activated sugar is transported into the Golgi apparatus and serves as a substrate for the linkage-specific sialyltransferases. Interference with sugar activation abolishes sialylation and is embryonic lethal in mammals. In this chapter we focus on the enzyme catalyzing the activation of sialic acid, the CMP-sialic acid synthetase (CMAS), and compare the enzymatic properties of CMASs isolated from different species. Information concerning the reaction mechanism and active site architecture is included. Moreover, the unusual nuclear localization of vertebrate CMASs as well as the biotechnological application of bacterial CMAS enzymes is addressed.
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Affiliation(s)
- Melanie Sellmeier
- Institute for Cellular Chemistry, Hannover Medical School (MHH), Hannover, 30625, Germany
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12
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The role of Drosophila cytidine monophosphate-sialic acid synthetase in the nervous system. J Neurosci 2013; 33:12306-15. [PMID: 23884937 DOI: 10.1523/jneurosci.5220-12.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
While sialylation plays important functions in the nervous system, the complexity of glycosylation pathways and limitations of genetic approaches preclude the efficient analysis of these functions in mammalian organisms. Drosophila has recently emerged as a promising model for studying neural sialylation. Drosophila sialyltransferase, DSiaT, was shown to be involved in the regulation of neural transmission. However, the sialylation pathway was not investigated in Drosophila beyond the DSiaT-mediated step. Here we focused on the function of Drosophila cytidine monophosphate-sialic acid synthetase (CSAS), the enzyme providing a sugar donor for DSiaT. Our results revealed that the expression of CSAS is tightly regulated and restricted to the CNS throughout development and in adult flies. We generated CSAS mutants and analyzed their phenotypes using behavioral and physiological approaches. Our experiments demonstrated that mutant phenotypes of CSAS are similar to those of DSiaT, including decreased longevity, temperature-induced paralysis, locomotor abnormalities, and defects of neural transmission at neuromuscular junctions. Genetic interactions between CSAS, DSiaT, and voltage-gated channel genes paralytic and seizure were consistent with the hypothesis that CSAS and DSiaT function within the same pathway regulating neural excitability. Intriguingly, these interactions also suggested that CSAS and DSiaT have some additional, independent functions. Moreover, unlike its mammalian counterparts that work in the nucleus, Drosophila CSAS was found to be a glycoprotein-bearing N-glycans and predominantly localized in vivo to the Golgi compartment. Our work provides the first systematic analysis of in vivo functions of a eukaryotic CSAS gene and sheds light on evolutionary relationships among metazoan CSAS proteins.
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13
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Büll C, Boltje TJ, Wassink M, de Graaf AMA, van Delft FL, den Brok MH, Adema GJ. Targeting aberrant sialylation in cancer cells using a fluorinated sialic acid analog impairs adhesion, migration, and in vivo tumor growth. Mol Cancer Ther 2013; 12:1935-46. [PMID: 23974695 DOI: 10.1158/1535-7163.mct-13-0279] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cancer cells decorate their surface with a dense layer of sialylated glycans by upregulating the expression of sialyltransferases and other glycogenes. Although sialic acids play a vital role in many biologic processes, hypersialylation in particular has been shown to contribute to cancer cell progression and metastasis. Accordingly, selective strategies to interfere with sialic acid synthesis might offer a powerful approach in cancer therapy. In the present study, we assessed the potential of a recently developed fluorinated sialic acid analogue (P-3F(ax)-Neu5Ac) to block the synthesis of sialoglycans in murine melanoma cells and the consequences on cell adhesion, migration, and in vivo growth. The results showed that P-3F(ax)-Neu5Ac readily caused depletion of α2,3-/α2,6-linked sialic acids in B16F10 cells for several days. Long-term inhibition of sialylation for 28 days was feasible without affecting cell viability or proliferation. Moreover, P-3F(ax)-Neu5Ac proved to be a highly potent inhibitor of sialylation even at high concentrations of competing sialyltransferase substrates. P-3F(ax)-Neu5Ac-treated cancer cells exhibited impaired binding to poly-l-lysine, type I collagen, and fibronectin and diminished migratory capacity. Finally, blocking sialylation of B16F10 tumor cells with this novel sialic acid analogue reduced their growth in vivo. These results indicate that P-3F(ax)-Neu5Ac is a powerful glycomimetic capable of inhibiting aberrant sialylation that can potentially be used for anticancer therapy.
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Affiliation(s)
- Christian Büll
- Corresponding Author: Gosse J. Adema, 278 Department of Tumor Immunology, Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen Medical Centre P.O. Box 9101, Nijmegen 6500 HB, the Netherlands.
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14
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Weinhold B, Sellmeier M, Schaper W, Blume L, Philippens B, Kats E, Bernard U, Galuska SP, Geyer H, Geyer R, Worthmann K, Schiffer M, Groos S, Gerardy-Schahn R, Münster-Kühnel AK. Deficits in sialylation impair podocyte maturation. J Am Soc Nephrol 2012; 23:1319-28. [PMID: 22745475 DOI: 10.1681/asn.2011090947] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The role of sialylation in kidney biology is not fully understood. The synthesis of sialoglycoconjugates, which form the outermost structures of animal cells, requires CMP-sialic acid, which is a product of the nuclear enzyme CMAS. We used a knock-in strategy to create a mouse with point mutations in the canonical nuclear localization signal of CMAS, which relocated the enzyme to the cytoplasm of transfected cells without affecting its activity. Although insufficient to prevent nuclear entry in mice, the mutation led to a drastically reduced concentration of nuclear-expressed enzyme. Mice homozygous for the mutation died from kidney failure within 72 hours after birth. The Cmas(nls) mouse exhibited podocyte foot process effacement, absence of slit diaphragms, and massive proteinuria, recapitulating features of nephrin-knockout mice and of patients with Finnish-type congenital nephrotic syndrome. Although the Cmas(nls) mouse displayed normal sialylation in all organs including kidney, a critical shortage of CMP-sialic acid prevented sialylation of nephrin and podocalyxin in the maturing podocyte where it is required during the formation of foot processes. Accordingly, the sialylation defects progressed with time and paralleled the morphologic changes. In summary, sialylation is critical during the development of the glomerular filtration barrier and required for the proper function of nephrin. Whether altered sialylation impairs nephrin function in human disease requires further study.
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Affiliation(s)
- Birgit Weinhold
- Institute for Cellular Chemistry, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany
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15
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Schaper W, Bentrop J, Ustinova J, Blume L, Kats E, Tiralongo J, Weinhold B, Bastmeyer M, Münster-Kühnel AK. Identification and biochemical characterization of two functional CMP-sialic acid synthetases in Danio rerio. J Biol Chem 2012; 287:13239-48. [PMID: 22351762 DOI: 10.1074/jbc.m111.327544] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sialic acids (Sia) form the nonreducing end of the bulk of cell surface-expressed glycoconjugates. They are, therefore, major elements in intercellular communication processes. The addition of Sia to glycoconjugates requires metabolic activation to CMP-Sia, catalyzed by CMP-Sia synthetase (CMAS). This highly conserved enzyme is located in the cell nucleus in all vertebrates investigated to date, but its nuclear function remains elusive. Here, we describe the identification and characterization of two Cmas enzymes in Danio rerio (dreCmas), one of which is exclusively localized in the cytosol. We show that the two cmas genes most likely originated from the third whole genome duplication, which occurred at the base of teleost radiation. cmas paralogues were maintained in fishes of the Otocephala clade, whereas one copy got subsequently lost in Euteleostei (e.g. rainbow trout). In zebrafish, the two genes exhibited a distinct spatial expression pattern. The products of these genes (dreCmas1 and dreCmas2) diverged not only with respect to subcellular localization but also in substrate specificity. Nuclear dreCmas1 favored N-acetylneuraminic acid, whereas the cytosolic dreCmas2 showed highest affinity for 5-deamino-neuraminic acid. The subcellular localization was confirmed for the endogenous enzymes in fractionated zebrafish lysates. Nuclear entry of dreCmas1 was mediated by a bipartite nuclear localization signal, which seemed irrelevant for other enzymatic functions. With the current demonstration that in zebrafish two subfunctionalized cmas paralogues co-exist, we introduce a novel and unique model to detail the roles that CMAS has in the nucleus and in the sialylation pathways of animal cells.
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Affiliation(s)
- Wiebke Schaper
- Institute of Cellular Chemistry, Hannover Medical School (MHH), Carl-Neuberg-Strasse1, D-30625 Hannover, Germany
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16
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Li Y, Yu H, Cao H, Muthana S, Chen X. Pasteurella multocida CMP-sialic acid synthetase and mutants of Neisseria meningitidis CMP-sialic acid synthetase with improved substrate promiscuity. Appl Microbiol Biotechnol 2011; 93:2411-23. [PMID: 21968653 DOI: 10.1007/s00253-011-3579-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 08/11/2011] [Accepted: 09/13/2011] [Indexed: 01/19/2023]
Abstract
Cytidine 5'-monophosphate (CMP)-sialic acid synthetases (CSSs) catalyze the formation of CMP-sialic acid from CTP and sialic acid, a key step for sialyltransferase-catalyzed biosynthesis of sialic acid-containing oligosaccharides and glycoconjugates. More than 50 different sialic acid forms have been identified in nature. To facilitate the enzymatic synthesis of sialosides with diverse naturally occurring sialic acid forms and their non-natural derivatives, CMP-sialic acid synthetases with promiscuous substrate specificity are needed. Herein we report the cloning, characterization, and substrate specificity studies of a new CSS from Pasteurella multocida strain P-1059 (PmCSS) and a CSS from Haemophillus ducreyi (HdCSS). Based on protein sequence alignment and substrate specificity studies of these two CSSs and a Neisseria meningitidis CSS (NmCSS), as well as crystal structure modeling and analysis of NmCSS, NmCSS mutants (NmCSS_S81R and NmCSS_Q163A) with improved substrate promiscuity were generated. The strategy of combining substrate specificity studies of enzymes from different sources and protein crystal structure studies can be a general approach for designing enzyme mutants with improved activity and substrate promiscuity.
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Affiliation(s)
- Yanhong Li
- Department of Chemistry, University of California-Davis, Davis, CA 95616, USA
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17
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Carter H, Samayoa J, Hruban RH, Karchin R. Prioritization of driver mutations in pancreatic cancer using cancer-specific high-throughput annotation of somatic mutations (CHASM). Cancer Biol Ther 2010; 10:582-7. [PMID: 20581473 DOI: 10.4161/cbt.10.6.12537] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Over 20,000 genes were recently sequenced in a series of 24 pancreatic cancers. We applied CHASM (Cancer-specific High-throughput Annotation of Somatic Mutations) to 963 of the missense somatic missense mutations discovered in these 24 cancers. CHASM identified putative driver mutations (false discovery rate ≤0.3) in three known pancreatic cancer driver genes (P53, SMAD4, CDKN2A). An additional 15 genes with putative driver mutations include genes coding for kinases (PIK3CG, DGKA, STK33, TTK and PRKCG), for cell cycle related proteins (NEK8), and for proteins involved in cell adhesion (CMAS, PCDHB2). These and other mutations identified by CHASM point to potential "driver genes" in pancreatic cancer that should be prioritized for additional follow-up.
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Affiliation(s)
- Hannah Carter
- Department of Biomedical Engineering and Institute for Computational Medicine, The Sol Goldman Pancreatic Cancer Research Center, Johns Hopkins Kimmel Cancer Center, Baltimore, MD, USA
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18
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Horsfall LE, Nelson A, Berry A. Identification and characterization of important residues in the catalytic mechanism of CMP-Neu5Ac synthetase from Neisseria meningitidis. FEBS J 2010; 277:2779-90. [PMID: 20491913 PMCID: PMC2901514 DOI: 10.1111/j.1742-4658.2010.07696.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Sialylated oligosaccharides, present on mammalian outer-cell surfaces, play vital roles in cellular interactions and some bacteria are able to mimic these structures to evade their host’s immune system. It would be of great benefit to the study of infectious and autoimmune diseases and cancers, to understand the pathway of sialylation in detail to enable the design and production of inhibitors and mimetics. Sialylation occurs in two stages, the first to activate sialic acid and the second to transfer it to the target molecule. The activation step is catalysed by the enzyme CMP-Neu5Ac synthetase (CNS). Here we used crystal structures of CNS and similar enzymes to predict residues of importance in the CNS from Neisseria meningitidis. Nine residues were mutated to alanine, and the steady-state enzyme kinetic parameters were measured using a continuous assay to detect one of the products of the reaction, pyrophosphate. Mutations that caused the greatest loss in activity included K142A, D211A, D209A and a series of mutations at residue Q104, highlighted from sequence-alignment studies of related enzymes, demonstrating significant roles for these residues in the catalytic mechanism of CNS. The mutations of D211A and D209A provide strong evidence for a previously proposed metal-binding site in the enzyme, and the results of our mutations at residue Q104 lead us to include this residue in the metal-binding site of an intermediate complex. This suggests that, like the sugar-activating lipopolysaccharide-synthesizing CMP-2-keto-3-deoxy-manno-octonic acid synthetase enzyme KdsB, CNS recruits two Mg2+ ions during the catalytic cycle.
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Affiliation(s)
- Louise E Horsfall
- Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds, UK
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19
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Tomiya N. Humanization of recombinant glycoproteins expressed in insect cells. TRENDS GLYCOSCI GLYC 2009. [DOI: 10.4052/tigg.21.71] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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20
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Chemoenzymatic synthesis of CMP-N-acetyl-7-fluoro-7-deoxy-neuraminic acid. Carbohydr Res 2008; 343:2075-82. [PMID: 18353292 DOI: 10.1016/j.carres.2008.02.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 01/31/2008] [Accepted: 02/04/2008] [Indexed: 11/20/2022]
Abstract
7-Fluoro sialic acid was prepared and activated as cytidine monophosphate (CMP) ester. The synthesis started with d-glucose, which was efficiently converted into N-acetyl-4-fluoro-4-deoxy-d-mannosamine. Aldolase catalyzed transformation yielded the corresponding fluorinated sialic acid which was activated as CMP ester using three different synthetases in the presence as well as in the absence of pyrophosphatase which possesses inhibitory properties. Finally, conditions were optimized to perform a one-pot reaction starting from fluorinated mannosamine, which yielded the 7-fluoro-7-deoxy-CMP-sialic acid by incubation with three enzymes.
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21
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Jones HM, Bailey MA, Baty CJ, Macgregor GG, Syme CA, Hamilton KL, Devor DC. An NH2-terminal multi-basic RKR motif is required for the ATP-dependent regulation of hIK1. Channels (Austin) 2007; 1:80-91. [PMID: 18690018 DOI: 10.4161/chan.3999] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
We previously demonstrated that the ATP/PKA-dependent activation of the human intermediate conductance, Ca2+-activated K+ channel, hIK1, is dependent upon a C-terminal motif. The NH2-terminus of hIK1 contains a multi-basic 13RRRKR17 motif, known to be important in the trafficking and function of ion channels. While individual mutations within this domain have no effect on channel function, the triple mutation (15RKR17/AAA), as well as additional double mutations, result in a near complete loss of functional channels, as assessed by whole-cell patch-clamp. However, cell-surface immunoprecipitation studies confirmed expression of these mutated channels at the plasma membrane. To elucidate the functional consequences of the (15)RKR(17)/AAA mutation we performed inside-out patch clamp recordings where we observed no difference in Ca2+ affinity between the wild-type and mutated channels. However, in contrast to wild-type hIK1, channels expressing the 15RKR17/AAA mutation exhibited rundown, which could not be reversed by the addition of ATP. Wild-type hIK1 channel activity was reduced by alkaline phosphatase both in the presence and absence of ATP, indicative of a phosphorylation event, whereas the 15RKR17/AAA mutation eliminated this effect of alkaline phosphatase. Further, single channel analysis demonstrated that the 15RKR17/AAA mutation resulted in a four-fold lower channel open probability (P(o)), in the presence of saturating Ca2+ and ATP, compared to wild-type hIK1. In conclusion, these results represent the first demonstration for a role of the NH2-terminus in the second messenger-dependent regulation of hIK1 and, in combination with our previous findings, suggest that this regulation is dependent upon a close NH2/C-terminal association.
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Affiliation(s)
- Heather M Jones
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA
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22
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Fujita A, Sato C, Kitajima K. Identification of the nuclear export signals that regulate the intracellular localization of the mouse CMP-sialic acid synthetase. Biochem Biophys Res Commun 2007; 355:174-80. [PMID: 17292865 DOI: 10.1016/j.bbrc.2007.01.139] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 01/23/2007] [Indexed: 11/19/2022]
Abstract
The CMP-sialic acid synthetase (CSS) catalyzes the activation of sialic acid (Sia) to CMP-Sia which is a donor substrate of sialyltransferases. The vertebrate CSSs are usually localized in nucleus due to the nuclear localization signal (NLS) on the molecule. In this study, we first point out that a small, but significant population of the mouse CMP-sialic acid synthetase (mCSS) is also present in cytoplasm, though mostly in nucleus. As a mechanism for the localization in cytoplasm, we first identified two nuclear export signals (NESs) in mCSS, based on the localization studies of the potential NES-deleted mCSS mutants as well as the potential NES-tagged eGFP proteins. These two NESs are conserved among mammalian and fish CSSs, but not present in the bacterial or insect CSS. These results suggest that the intracellular localization of vertebrate CSSs is regulated by not only the NLS, but also the NES sequences.
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Affiliation(s)
- Akiko Fujita
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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23
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Hershfield JR, Madhavarao CN, Moffett JR, Benjamins JA, Garbern JY, Namboodiri A. Aspartoacylase is a regulated nuclear‐cytoplasmic enzyme. FASEB J 2006; 20:2139-41. [PMID: 16935940 DOI: 10.1096/fj.05-5358fje] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Mutations in the gene for aspartoacylase (ASPA), which catalyzes deacetylation of N-acetyl-L-aspartate in the central nervous system (CNS), result in Canavan Disease, a fatal dysmyelinating disease. Consistent with its role in supplying acetate for myelin lipid synthesis, ASPA is thought to be cytoplasmic. Here we describe the occurrence of ASPA within nuclei of rat brain and kidney, and in cultured rodent oligodendrocytes. Immunohistochemistry showed cytoplasmic and nuclear ASPA staining, the specificity of which was demonstrated by its absence from tissues of the Tremor rat, an ASPA-null mutant. Subcellular fractionation analysis revealed low enzyme activity against NAA in nuclear fractions from normal rats. Whereas two recent reports have indicated that ASPA exists as a dimer, size-exclusion chromatography of subcellular fractions showed ASPA is an active monomer in both subcellular fractions. Western blotting detected ASPA as a single 38 kD band. Because ASPA is small enough to passively diffuse into the nucleus, we constructed, expressed, and detected in COS-7 cells a green fluorescent protein-human ASPA (GFP-hASPA) fusion protein larger than the permissible size for the nuclear pore complex. GFP-hASPA was enzymatically active and showed mixed nuclear-cytoplasmic distribution. We conclude that ASPA is a regulated nuclear-cytoplasmic protein that may have distinct functional roles in the two cellular compartments.
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Affiliation(s)
- Jeremy R Hershfield
- Dept. of Anatomy, Physiology, and Genetics, USUHS, 4301 Jones Bridge Rd, Bethesda, MD 20814, USA
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24
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Viswanathan K, Tomiya N, Park J, Singh S, Lee YC, Palter K, Betenbaugh MJ. Expression of a functional Drosophila melanogaster CMP-sialic acid synthetase. Differential localization of the Drosophila and human enzymes. J Biol Chem 2006; 281:15929-40. [PMID: 16537535 DOI: 10.1074/jbc.m512186200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CMP-N-acetylneuraminic acid is a critical metabolite in the generation of glycoconjugates that play a role in development and other physiological processes. Whereas pathways for its generation are firmly established in vertebrates, the presence and function of the relevant synthetic enzyme in insects and other protostomes is unknown. In this study, we characterize the first functional CMP-sialic acid synthase (DmCSAS) from any protostome lineage expressed from a D. melanogaster cDNA clone. Homologous genes were subsequently identified in other insect species. The gene is developmentally regulated, with expression first appearing at 12-24 h of embryogenesis, low expression through larval and pupal stages, and greatly enriched expression in the adult head, suggesting a possible role in the central nervous system. Activity of the enzyme was verified by an increase in in vitro and in vivo CMP-N-acetylneuraminic acid levels when expressed in a heterologous host. Unlike all known vertebrate CMP-sialic acid synthetase (CSAS) proteins that localize to the nucleus, the D. melanogaster CSAS protein was targeted to the Golgi compartment when expressed in both heterologous mammalian and insect cell lines. Replacement of the N-terminal leader sequence of DmCSAS with the human CSAS N-terminal sequence resulted in the redirection of the chimeric CSAS protein to the nucleus but with a concomitant loss of enzymatic activity. The localization of CSAS orthologs to different intracellular organelles represents, to our knowledge, the first example of differential protein targeting of orthologs in eukaryotes and reveals how the sialylation pathway diverged during the evolution of protostomes and deuterostomes.
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Affiliation(s)
- Karthik Viswanathan
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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25
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Yarovaya N, Schot R, Fodero L, McMahon M, Mahoney A, Williams R, Verbeek E, de Bondt A, Hampson M, van der Spek P, Stubbs A, Masters CL, Verheijen FW, Mancini GMS, Venter DJ. Sialin, an anion transporter defective in sialic acid storage diseases, shows highly variable expression in adult mouse brain, and is developmentally regulated. Neurobiol Dis 2005; 19:351-65. [PMID: 16023578 DOI: 10.1016/j.nbd.2004.12.020] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2004] [Revised: 11/15/2004] [Accepted: 12/22/2004] [Indexed: 01/27/2023] Open
Abstract
Sialin is a lysosomal membrane protein encoded by the SLC17A5 gene, which is mutated in patients with sialic acid storage diseases (SASD). To further understand the role of sialin in normal CNS development and in the progressive neuronal atrophy and dysmyelination seen in SASD, we investigated its normal cellular distribution in adult and developing mice. Overall, sialin showed granular immunoreactivity, consistent with a vesicular protein. Adult mice showed widespread sialin expression, including in the brain, heart, lung, and liver. High-level immunoreactivity was seen in the neuropil of the hippocampus, striatum, and cerebral cortex, as well as in the perikarya of cerebellar Purkinje cells, globus pallidus, and certain thalamic and brainstem nuclei. In mouse embryos, the highest levels of expression were observed in the nervous system. We discuss the possible role of sialin in normal development and in SASD pathogenesis, as a framework for further investigation of its function in these contexts.
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Affiliation(s)
- Natalia Yarovaya
- Murdoch Children's Research Institute, Melbourne, Victoria 3052, Australia
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26
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Fujita A, Sato C, Münster-Kühnel AK, Gerardy-Schahn R, Kitajima K. Development of a simple and efficient method for assaying cytidine monophosphate sialic acid synthetase activity using an enzymatic reduced nicotinamide adenine dinucleotide/oxidized nicotinamide adenine dinucleotide converting system. Anal Biochem 2005; 337:12-21. [PMID: 15649371 DOI: 10.1016/j.ab.2004.10.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Indexed: 11/24/2022]
Abstract
A new reliable method to assay the activity of cytidine monophosphate sialic acid (CMP-Sia) synthetase (CSS) has been developed. The activation of sialic acids (Sia) to CMP-Sia is a prerequisite for the de novo synthesis of sialoglycoconjugates. In vertebrates, CSS has been cloned from human, mouse, and rainbow trout, and the crystal structure has been resolved for the mouse enzyme. The mouse and rainbow trout enzyme have been compared with respect to substrate specificity, demonstrating that the mouse enzyme exhibits a pronounced specificity for N-acetylneuraminic acid (Neu5Ac), while the rainbow trout CSS is equally active with either of three Sia species, Neu5Ac, N-glycolylneuraminic acid (Neu5Gc), and deaminoneuraminic acid (KDN). However, molecular details that explain the pronounced substrate specificities are unknown. Understanding the catalytic mechanisms of these enzymes is of major importance, since CSSs play crucial roles in cellular sialylation patterns and thus are potential drug targets in a number of pathophysiological situations. The availability of the cDNAs and the obtained structural data enable rational approaches; however, these efforts are limited by the lack of a reliable high-throughput assay system. Here we describe a new assay system that allows product quantification in a reduced nicotinamide adenine dinucleotide (NADH)-dependent color reaction. The activation reaction catalyzed by CSS, CTP+Sia-->CMP-Sia+pyrophosphate, was evaluated by a consumption of Sia, which corresponds to that of NADH on the following two successive reactions: (i) Sia-->pyruvate+ManNAc (or Man), catalyzed by a sialic acid lyase (SAL), and (ii) pyruvate+NADH-->lactate+oxidized nicotinamide adenine dinucleotide (NAD+), catalyzed by a lactate dehydrogenase (LDH). Consumption of NADH can be photometrically monitored on a microtiter plate reader for a number of test samples at the same time. Furthermore, based on the quantification of CSS used in the SAL/LDH assay, relative activities toward Sia derivatives have been obtained. The preference of mouse CSS toward Neu5Ac and the ability of the rainbow trout enzyme to activate both KDN and Neu5Ac were confirmed. Thus, this simple and time-saving method is suitable for a systematic comparison of enzyme activity of structurally mutated enzymes based on the relative specific activity.
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Affiliation(s)
- Akiko Fujita
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
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27
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Krause S, Hinderlich S, Amsili S, Horstkorte R, Wiendl H, Argov Z, Mitrani-Rosenbaum S, Lochmüller H. Localization of UDP-GlcNAc 2-epimerase/ManAc kinase (GNE) in the Golgi complex and the nucleus of mammalian cells. Exp Cell Res 2005; 304:365-79. [PMID: 15748884 DOI: 10.1016/j.yexcr.2004.11.010] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Revised: 10/31/2004] [Accepted: 11/04/2004] [Indexed: 01/24/2023]
Abstract
The bifunctional enzyme UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) is essential for early embryonic development and catalyzes the rate limiting step in sialic acid biosynthesis. Although epimerase and kinase activities have been attributed to GNE, little is known about the regulation, differential expression, and subcellular localization of GNE in vivo. Mutations in GNE cause a rare inherited muscle disorder in humans called hereditary inclusion body myopathy (HIBM). However, the role of GNE in HIBM pathogenesis has not been defined yet. Here, we show that the GNE protein is expressed in various mammalian cells and tissues with highest levels found in cancer cells and liver. In human skeletal muscle, GNE protein is developmentally regulated: high levels are found in immature myoblasts but low levels in mature skeletal muscle. The GNE protein colocalizes with resident proteins of the Golgi compartment in a variety of human cells including muscle. Drug-induced disruption of the Golgi and subsequent recovery reveals co-distribution of GNE along with Golgi-targeted proteins. This subcellular localization of GNE is in good agreement with its established role as the key enzyme of sialic acid biosynthesis, since the sialylation of glycoconjugates takes place in the Golgi complex. Surprisingly, GNE is also detected in the nucleus. Upon nocodazole treatment, GNE redistributes to the cytoplasm suggesting that GNE may act as a nucleocytoplasmic shuttling protein. A regulatory role for GNE shifting between the nuclear and the Golgi compartment is proposed. Further insight into GNE regulation may promote the understanding of HIBM pathogenesis.
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Affiliation(s)
- Sabine Krause
- Friedrich-Baur-Institute, Department of Neurology and Gene Center, Ludwig-Maximilians-University, Genzentrum München, Feodor-Lynen-Str. 25, 81377 München, Germany
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28
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Shostak Y, Yamamoto KR. Overlapping but separable determinants of DNA binding and nuclear localization map to the C-terminal end of the Caenorhabditis elegans DAF-12 DNA binding domain. J Biol Chem 2005; 280:6554-60. [PMID: 15611047 DOI: 10.1074/jbc.m412928200] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteins are commonly viewed as modular assemblies of functional domains. We analyzed a loss-of-function mutation in the Caenorhabditis elegans intracellular receptor DAF-12, a conservative substitution of an arginine to a lysine at position 197 (R197K). Arg(197) resides in region similar to a nuclear localization signal, just downstream of the receptor minimal zinc finger DNA binding domain (DBD) core. We found that the R197K, but not mutations of neighboring arginine or lysine residues, dramatically reduced DAF-12 transcriptional regulatory activity in a yeast reporter assay. This reduction in regulatory activity correlated with greatly decreased DNA binding affinity in vitro, suggesting a role for the DAF-12 DBD C-terminal region (dbdC), and specifically for Arg(197), in DNA binding. Remarkably, three basic residues immediately contiguous with Arg(197) played little role in DNA binding and rather affected nuclear localization; in contrast, Arg(197) itself was dispensable for nuclear localization. Thus, DAF-12 dbdC harbors overlapping but separable determinants of DNA binding and nuclear localization in a single small region.
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Affiliation(s)
- Yuriy Shostak
- Program in Biochemistry and Molecular Biology and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143-2280
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Horstkorte R, Mühlenhoff M, Reutter W, Nöhring S, Zimmermann-Kordmann M, Gerardy-Schahn R. Selective inhibition of polysialyltransferase ST8SiaII by unnatural sialic acids. Exp Cell Res 2004; 298:268-74. [PMID: 15242781 DOI: 10.1016/j.yexcr.2004.04.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2004] [Revised: 03/05/2004] [Indexed: 10/26/2022]
Abstract
Polysialic acid (polySia) is a unique and highly regulated posttranslational modification of the neural cell adhesion molecule (NCAM). The presence of polySia affects NCAM-dependent cell adhesion and plays an important role during brain development, neural regeneration and plastic processes including learning and memory. Polysialylated NCAM is expressed on several neuroendocrine tumors of high malignancy and correlates with poor prognosis. Two closely related enzymes, the polysialyltransferases ST8SiaII and ST8SiaIV, catalyze the biosynthesis of polySia. However, the impact of each enzyme in NCAM polysialylation is not understood. Here, we describe the selective cell-based in vitro inhibition of ST8SiaII using synthetic sialic acid precursors. We provide evidence for different substrate affinities of ST8SiaII and ST8SiaIV. These data open the possibility to study the individual role of the two enzymes during various aspects of brain development and function and in tumorigenesis.
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Affiliation(s)
- Rüdiger Horstkorte
- Institut für Molekularbiologie und Biochemie, Charité-Universitätsmedizin Berlin, D-14195 Berlin-Dahlem, Germany.
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30
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Sanz-Rodriguez F, Guerrero-Esteo M, Botella LM, Banville D, Vary CPH, Bernabéu C. Endoglin regulates cytoskeletal organization through binding to ZRP-1, a member of the Lim family of proteins. J Biol Chem 2004; 279:32858-68. [PMID: 15148318 DOI: 10.1074/jbc.m400843200] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Endoglin is a component of the transforming growth factor-beta receptor complex abundantly expressed at the surface of endothelial cells and plays an important role in cardiovascular development and vascular remodeling. By using the cytoplasmic domain of endoglin as a bait for screening protein interactors, we have identified ZRP-1 (zyxin-related protein 1), a 476-amino acid member that belongs to a family of LIM containing proteins that includes zyxin and lipoma-preferred partner. The endoglin interacting region was mapped within the three double zinc finger LIM domains of the ZRP-1 C terminus. Analysis of the subcellular distribution of ZRP-1 demonstrated that in the absence of endoglin, ZRP-1 mainly localizes to focal adhesion sites, whereas in the presence of endoglin ZRP-1 is found along actin stress fibers. Because the LIM family of proteins has been shown to associate with the actin cytoskeleton, we investigated the possibility of a regulatory role for endoglin with regard to this structure. Expression of endoglin resulted in a dramatic reorganization of the actin cytoskeleton. In the absence of endoglin, F-actin was localized to dense aggregates of bundles, whereas in the presence of endoglin, expressed in endothelial cells, F-actin was in stress fibers and colocalized with ZRP-1. Furthermore, small interfering RNA-mediated suppression of endoglin or ZRP-1, or clustering of endoglin in endothelial cells, led to mislocalization of F-actin fibers. These results suggest a regulatory role for endoglin, via its interaction with ZRP-1, in the actin cytoskeletal organization.
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31
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Krapp S, Münster-Kühnel AK, Kaiser JT, Huber R, Tiralongo J, Gerardy-Schahn R, Jacob U. The crystal structure of murine CMP-5-N-acetylneuraminic acid synthetase. J Mol Biol 2004; 334:625-37. [PMID: 14636592 DOI: 10.1016/j.jmb.2003.09.080] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Sialic acids are activated by CMP-5-N-acetylneuraminic acid synthetase prior to their transfer onto oligo- or polysaccharides. Here, we present the crystal structure of the N-terminal catalytically active domain of the murine 5-N-acetylneuraminic acid synthetase in complex with the reaction product. In contrast to the previously solved structure of 5-N-acetylneuraminic acid synthetase from Neisseria meningitidis and the related CMP-KDO-synthetase of Escherichia coli, the murine enzyme is a tetramer, which was observed with the active sites closed. In this conformation a loop is shifted by 6A towards the active site and thus an essential arginine residue can participate in catalysis. Furthermore, a network of intermolecular salt-bridges and hydrogen bonds in the dimer as well as hydrophobic interfaces between two dimers indicate a cooperative behaviour of the enzyme. In addition, a complex regulation of the enzyme activity is proposed that includes phosphorylation and dephosphorylation.
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Affiliation(s)
- Stephan Krapp
- Max-Planck-Institut für Biochemie, Abteilung für Strukturforschung, Am Klopferspitz 18a, 82152, Martinsried, Germany
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