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Karade SS, Franco EJ, Rojas AC, Hanrahan KC, Kolesnikov A, Yu W, MacKerell AD, Hill DC, Weber DJ, Brown AN, Treston AM, Mariuzza RA. Structure-Based Design of Potent Iminosugar Inhibitors of Endoplasmic Reticulum α-Glucosidase I with Anti-SARS-CoV-2 Activity. J Med Chem 2023; 66:2744-2760. [PMID: 36762932 PMCID: PMC10278443 DOI: 10.1021/acs.jmedchem.2c01750] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Enveloped viruses depend on the host endoplasmic reticulum (ER) quality control (QC) machinery for proper glycoprotein folding. The endoplasmic reticulum quality control (ERQC) enzyme α-glucosidase I (α-GluI) is an attractive target for developing broad-spectrum antivirals. We synthesized 28 inhibitors designed to interact with all four subsites of the α-GluI active site. These inhibitors are derivatives of the iminosugars 1-deoxynojirimycin (1-DNJ) and valiolamine. Crystal structures of ER α-GluI bound to 25 1-DNJ and three valiolamine derivatives revealed the basis for inhibitory potency. We established the structure-activity relationship (SAR) and used the Site Identification by Ligand Competitive Saturation (SILCS) method to develop a model for predicting α-GluI inhibition. We screened the compounds against SARS-CoV-2 in vitro to identify those with greater antiviral activity than the benchmark α-glucosidase inhibitor UV-4. These host-targeting compounds are candidates for investigation in animal models of SARS-CoV-2 and for testing against other viruses that rely on ERQC for correct glycoprotein folding.
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Affiliation(s)
- Sharanbasappa S. Karade
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Evelyn J. Franco
- Institute for Therapeutic Innovation, Department of Medicine, College of Medicine, University of Florida, Orlando, FL 32827, USA
| | - Ana C. Rojas
- Institute for Therapeutic Innovation, Department of Medicine, College of Medicine, University of Florida, Orlando, FL 32827, USA
| | - Kaley C. Hanrahan
- Institute for Therapeutic Innovation, Department of Medicine, College of Medicine, University of Florida, Orlando, FL 32827, USA
| | - Alexander Kolesnikov
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
| | - Wenbo Yu
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
- Computer-Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201, USA
- Center for Biomolecular Therapeutics (CBT), Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Alexander D. MacKerell
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
- Computer-Aided Drug Design Center, Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, MD 21201, USA
- Center for Biomolecular Therapeutics (CBT), Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | | | - David J. Weber
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
- Center for Biomolecular Therapeutics (CBT), Department of Biochemistry and Molecular Biology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Ashley N. Brown
- Institute for Therapeutic Innovation, Department of Medicine, College of Medicine, University of Florida, Orlando, FL 32827, USA
| | - Anthony M. Treston
- Emergent BioSolutions, Gaithersburg, MD 20879, USA
- Current address: Treadwell Therapeutics, Toronto M5G 2M9, Canada
| | - Roy A. Mariuzza
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, MD 20850, USA
- Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA
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Karade SS, Kolesnikov A, Treston AM, Mariuzza RA. Identification of Endoplasmic Reticulum α-Glucosidase I from a Thermophilic Fungus as a Platform for Structure-Guided Antiviral Drug Design. Biochemistry 2022; 61:822-832. [PMID: 35476408 DOI: 10.1021/acs.biochem.2c00092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
All viruses depend on host cell proteins for replication. Denying viruses' access to the function of critical host proteins can result in antiviral activity against multiple virus families. In particular, small-molecule drug candidates which inhibit the α-glucosidase enzymes of the endoplasmic reticulum (ER) translation quality control (QC) pathway have demonstrated broad-spectrum antiviral activities and low risk for development of viral resistance. However, antiviral drug discovery focused on the ERQC enzyme α-glucosidase I (α-GluI) has been hampered by difficulties in obtaining crystal structures of complexes with inhibitors. We report here the identification of an orthologous enzyme from a thermophilic fungus, Chaetomium thermophilum (Ct), as a robust surrogate for mammalian ER α-GluI and a platform for inhibitor design. Previously annotated only as a hypothetical protein, the Ct protein was validated as a bona fide α-glucosidase by comparing its crystal structure to that of mammalian α-GluI, by demonstrating enzymatic activity on the unusual α-d-Glcp-(1 → 2)-α-d-Glcp-(1 → 3) substrate glycan, and by showing that well-known inhibitors of mammalian α-GluI (1-DNJ, UV-4, UV-5) also inhibit Ct α-GluI. Crystal structures of Ct α-GluI in complex with three such inhibitors (UV-4, UV-5, EB-0159) revealed extensive interactions with all four enzyme subsites and provided insights into the catalytic mechanism. Identification of ER Ct α-GluI as a surrogate for mammalian α-GluI will accelerate the structure-guided discovery of broad-spectrum antivirals. This study also highlights Ct as a source of thermostable eukaryotic proteins, such as ER α-Glu I, that lack orthologs in bacterial or archaeal thermophiles.
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Affiliation(s)
- Sharanbasappa S Karade
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, United States
| | - Alexander Kolesnikov
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, United States
| | | | - Roy A Mariuzza
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland 20850, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, United States
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Karade SS, Hill ML, Kiappes JL, Manne R, Aakula B, Zitzmann N, Warfield KL, Treston AM, Mariuzza RA. N-Substituted Valiolamine Derivatives as Potent Inhibitors of Endoplasmic Reticulum α-Glucosidases I and II with Antiviral Activity. J Med Chem 2021; 64:18010-18024. [PMID: 34870992 DOI: 10.1021/acs.jmedchem.1c01377] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Most enveloped viruses rely on the host cell endoplasmic reticulum (ER) quality control (QC) machinery for proper folding of glycoproteins. The key ER α-glucosidases (α-Glu) I and II of the ERQC machinery are attractive targets for developing broad-spectrum antivirals. Iminosugars based on deoxynojirimycin have been extensively studied as ER α-glucosidase inhibitors; however, other glycomimetic compounds are less established. Accordingly, we synthesized a series of N-substituted derivatives of valiolamine, the iminosugar scaffold of type 2 diabetes drug voglibose. To understand the basis for up to 100,000-fold improved inhibitory potency, we determined high-resolution crystal structures of mouse ER α-GluII in complex with valiolamine and 10 derivatives. The structures revealed extensive interactions with all four α-GluII subsites. We further showed that N-substituted valiolamines were active against dengue virus and SARS-CoV-2 in vitro. This study introduces valiolamine-based inhibitors of the ERQC machinery as candidates for developing potential broad-spectrum therapeutics against the existing and emerging viruses.
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Affiliation(s)
- Sharanbasappa S Karade
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, United States
| | - Michelle L Hill
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, U.K
| | - J L Kiappes
- Department of Chemistry, University College, London WC1H 0AJ, U.K
| | - Rajkumar Manne
- Sai Life Sciences Ltd., Hyderabad, 500032 Telangana, India
| | | | - Nicole Zitzmann
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, U.K
| | - Kelly L Warfield
- Emergent BioSolutions, Gaithersburg, Maryland 20879, United States
| | | | - Roy A Mariuzza
- University of Maryland Institute for Bioscience and Biotechnology Research, Rockville, Maryland 20850, United States.,Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, United States
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Hada N, Umeda Y, Kumada H, Shimazaki Y, Yamano K, Schweizer F, Oshima N, Takeda T, Kiuchi F. Synthesis of the Non Reducing End Oligosaccharides of Glycosphingolipids from <i>Ascaris suum</i>. Chem Pharm Bull (Tokyo) 2019; 67:143-154. [DOI: 10.1248/cpb.c18-00768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Noriyasu Hada
- Faculty of Pharmaceutical Sciences, Tokyo University of Science
- Faculty of Pharmacy, Keio University
| | | | | | | | | | - Frank Schweizer
- Departments of Chemistry and Medical Microbiology, University of Manitoba
| | - Naohiro Oshima
- Faculty of Pharmaceutical Sciences, Tokyo University of Science
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Hada N, Kitamura A, Yamano K, Schweizer F, Kiuchi F. Synthesis and Antigenicity against Human Sera of a Biotin-Labeled Oligosaccharide Portion of a Glycosphingolipid from the Parasite Echinococcus multilocularis. Chem Pharm Bull (Tokyo) 2016; 64:865-73. [DOI: 10.1248/cpb.c16-00211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
| | | | | | - Frank Schweizer
- Departments of Chemistry and Medical Microbiology, University of Manitoba
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Koizumi A, Yamano K, Schweizer F, Takeda T, Kiuchi F, Hada N. Synthesis of the carbohydrate moiety from the parasite Echinococcus multilocularis and their antigenicity against human sera. Eur J Med Chem 2011; 46:1768-78. [DOI: 10.1016/j.ejmech.2011.02.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 02/10/2011] [Accepted: 02/14/2011] [Indexed: 10/18/2022]
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Attolino E, Cumpstey I, Fairbanks AJ. Synthesis of the Glc3Man N-glycan tetrasaccharide by iterative allyl IAD. Carbohydr Res 2006; 341:1609-18. [PMID: 16529733 DOI: 10.1016/j.carres.2006.02.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 02/15/2006] [Accepted: 02/22/2006] [Indexed: 11/17/2022]
Abstract
The synthesis of the tetrasaccharide alpha-D-Glcp-(1-->2)-alpha-D-Glcp-(1-->3)-alpha-D-Glcp-(1-->3)-alpha-D-Manp-OMe, corresponding to the terminal tetrasaccharide portion of the glucose terminated arm of the N-glycan tetradecasaccharide, was achieved with complete stereocontrol by the use of iterative allyl protecting group mediated intramolecular aglycon delivery (allyl IAD) demonstrating the utility of intramolecular glycosylation for the stereocontrolled construction of multiple glycosidic linkages during the synthesis of an oligosaccharide.
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Affiliation(s)
- Emanuele Attolino
- Chemistry Research Laboratory, Oxford University, Mansfield Road, Oxford OX1 3TA, UK
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Matsuo I, Kashiwagi T, Totani K, Ito Y. First chemical synthesis of triglucosylated tetradecasaccharide (Glc3Man9GlcNAc2), a common precursor of asparagine-linked oligosaccharides. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.04.056] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Shoemaker GK, Lorieau J, Lau LH, Gillmor CS, Palcic MM. Multiple Sampling in Single-Cell Enzyme Assays Using CE-Laser-Induced Fluorescence to Monitor Reaction Progress. Anal Chem 2005; 77:3132-7. [PMID: 15889901 DOI: 10.1021/ac0481304] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel method for assaying enzymes from a single cell or small cell populations is described. The key advantage of this method is the ability to repeatedly sample a single cell enzyme reaction. Whereas multiple sampling has been achieved for larger cell types with a diameter of 1 mm, we report a technique by which single cell enzyme assays of small cells (15 microm in diameter) can be repeatedly carried out. Individual cells were isolated using an in-house-built micromanipulator and placed in nanoliter-scale reaction vessels. The cells were lysed with solution containing substrate, and enzyme activity was assayed by removing 5-nL aliquots with a recently developed nanopipettor. The reaction aliquot was then analyzed using capillary electrophoresis with laser-induced fluorescence detection to quantitate enzyme activity. Sf9 cells were assayed at the single cell level and found to be highly heterogeneous with respect to alpha-glucosidase II activity. Since only 5 nL of the single cell reaction was removed, multiple sampling was possible, allowing triplicate analysis of enzyme activity for each individual cell. Multiple sampling also permitted a single cell reaction to be monitored over time. The sensitivity of this method was demonstrated in the analysis of a low-abundance enzyme, alpha1,3-N-acetylgalactosaminyltransferase, from single HT29 cells. Detecting the product of this enzyme reaction required minimizing the dilution of cellular contents. To demonstrate the potential applications of this methodology in small scale biochemical analyses, single Arabidopsis knf embryos lacking the alpha-glucosidase I encoding KNOPF gene were assayed. Mutant embryos demonstrated insignificant conversion of a triglucose substrate, as compared to wild type, confirming the deletion of alpha-glucosidase I. Embryos were simultaneously assayed for a second enzyme, beta-galactosidase, illustrating that the mutants were viable except for their lack of alpha-glucosidase I activity.
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Affiliation(s)
- Glen K Shoemaker
- Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
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Lorieau J, Shoemaker GK, Palcic MM. Quantitative nanopipettor for miniaturized chemical and biochemical reaction sampling. Anal Chem 2004; 75:6351-4. [PMID: 14616021 DOI: 10.1021/ac0302410] [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: 11/29/2022]
Abstract
A novel and readily available pipettor capable of nanoliter-sized volume manipulation was developed to improve and increase the flexibility of small-scale reaction processing. The volume delivery was found to be reproducible, with typical relative standard deviations of 1-5%, and easily tunable over a range of nanoliter-sized aliquots. The nanopipettor was combined with capillary electrophoresis using laser-induced fluorescence detection to monitor a small-scale enzyme reaction (beta-galactosidase) using a tetramethylrhodamine-labeled substrate. The results were in good agreement with a standard enzyme assay using a micropipet, thus demonstrating the nanopipettor's potential in developing new nanoscale utrasensitive enzyme assays.
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Affiliation(s)
- Justin Lorieau
- Chemistry Department, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
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Cumpstey I, Butters TD, Tennant-Eyles RJ, Fairbanks AJ, France RR, Wormald MR. Synthesis of fluorescence-labelled disaccharide substrates of glucosidase II. Carbohydr Res 2004; 338:1937-49. [PMID: 14499570 DOI: 10.1016/s0008-6215(03)00255-6] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The fluorescence-labelled disaccharides Glcalpha(1-->3)GlcalphaOR and Glcalpha(1-->3)ManalphaOR, both substrates for the glycoprotein-processing enzyme glucosidase II, were synthesised via the use of a n-pentenyl-derived linker at the anomeric position. This allowed incorporation of a pyrenebutyric acid label, via a sequence of oxidative hydroboration, mesylation, azide displacement, reduction with concomitant global deprotection, and peptide coupling. Selective activation of a fully armed thioglycoside in the presence of n-pentenyl glycosides was readily achieved by the use of methyl triflate as promoter.
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Affiliation(s)
- Ian Cumpstey
- Dyson Perrins Laboratory, Oxford University, South Parks Road, Oxford OX1 3QY, UK
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Gillmor CS, Poindexter P, Lorieau J, Palcic MM, Somerville C. Alpha-glucosidase I is required for cellulose biosynthesis and morphogenesis in Arabidopsis. J Cell Biol 2002; 156:1003-13. [PMID: 11901167 PMCID: PMC2173474 DOI: 10.1083/jcb.200111093] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Novel mutations in the RSW1 and KNOPF genes were identified in a large-scale screen for mutations that affect cell expansion in early Arabidopsis embryos. Embryos from both types of mutants were radially swollen with greatly reduced levels of crystalline cellulose, the principal structural component of the cell wall. Because RSW1 was previously shown to encode a catalytic subunit of cellulose synthase, the similar morphology of knf and rsw1-2 embryos suggests that the radially swollen phenotype of knf mutants is largely due to their cellulose deficiency. Map-based cloning of the KNF gene and enzyme assays of knf embryos demonstrated that KNF encodes alpha-glucosidase I, the enzyme that catalyzes the first step in N-linked glycan processing. The strongly reduced cellulose content of knf mutants indicates that N-linked glycans are required for cellulose biosynthesis. Because cellulose synthase catalytic subunits do not appear to be N glycosylated, the N-glycan requirement apparently resides in other component(s) of the cellulose synthase machinery. Remarkably, cellular processes other than extracellular matrix biosynthesis and the formation of protein storage vacuoles appear unaffected in knf embryos. Thus in Arabidopsis cells, like yeast, N-glycan trimming is apparently required for the function of only a small subset of N-glycoproteins.
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Affiliation(s)
- C Stewart Gillmor
- Carnegie Institution, Department of Plant Biology, Stanford, CA 94305, USA
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Krylov SN, Arriaga EA, Chan NW, Dovichi NJ, Palcic MM. Metabolic cytometry: monitoring oligosaccharide biosynthesis in single cells by capillary electrophoresis. Anal Biochem 2000; 283:133-5. [PMID: 10906232 DOI: 10.1006/abio.2000.4648] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- S N Krylov
- Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
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Gerwig GJ, Bause E, Nuytinck LK, Vliegenthart JF, Breuer W, Kamerling JP, Espeel MF, Martin JJ, Chan NW, Dacremont GA. A novel disorder caused by defective biosynthesis of N-linked oligosaccharides due to glucosidase I deficiency. Am J Hum Genet 2000; 66:1744-56. [PMID: 10788335 PMCID: PMC1378052 DOI: 10.1086/302948] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Accepted: 03/14/2000] [Indexed: 12/23/2022] Open
Abstract
Glucosidase I is an important enzyme in N-linked glycoprotein processing, removing specifically distal alpha-1,2-linked glucose from the Glc3Man9GlcNAc2 precursor after its en bloc transfer from dolichyl diphosphate to a nascent polypeptide chain in the endoplasmic reticulum. We have identified a glucosidase I defect in a neonate with severe generalized hypotonia and dysmorphic features. The clinical course was progressive and was characterized by the occurrence of hepatomegaly, hypoventilation, feeding problems, seizures, and fatal outcome at age 74 d. The accumulation of the tetrasaccharide Glc(alpha1-2)Glc(alpha1-3)Glc(alpha1-3)Man in the patient's urine indicated a glycosylation disorder. Enzymological studies on liver tissue and cultured skin fibroblasts revealed a severe glucosidase I deficiency. The residual activity was <3% of that of controls. Glucosidase I activities in cultured skin fibroblasts from both parents were found to be 50% of those of controls. Tissues from the patient subjected to SDS-PAGE followed by immunoblotting revealed strongly decreased amounts of glucosidase I protein in the homogenate of the liver, and a less-severe decrease in cultured skin fibroblasts. Molecular studies showed that the patient was a compound heterozygote for two missense mutations in the glucosidase I gene: (1) one allele harbored a G-->C transition at nucleotide (nt) 1587, resulting in the substitution of Arg at position 486 by Thr (R486T), and (2) on the other allele a T-->C transition at nt 2085 resulted in the substitution of Phe at position 652 by Leu (F652L). The mother was heterozygous for the G-->C transition, whereas the father was heterozygous for the T-->C transition. These base changes were not seen in 100 control DNA samples. A causal relationship between the alpha-glucosidase I deficiency and the disease is postulated.
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Palcic MM, Scaman CH, Otter A, Szpacenko A, Romaniouk A, Li YX, Vijay IK. Processing alpha-glucosidase I is an inverting glycosidase. Glycoconj J 1999; 16:351-5. [PMID: 10619707 DOI: 10.1023/a:1007096011392] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Alpha-glucosidase I is a key enzyme in the biosynthesis of asparagine-linked oligosaccharides catalyzing the first processing event after the en bloc transfer of Glc3Man9GlcNAc2 to proteins. This enzyme is an inhibitor target for anti-viral agents that interfere with the formation of essential glycoproteins required in viral assembly, secretion and infectivity. Of fundamental mechanistic interest for all oligosaccharide hydrolyzing enzymes is the stereochemical course of the reaction which can occur with either retention or inversion of anomeric configuration. The stereochemistry is used to categorize enzymes and is important in designing mechanism-based inhibitors. To determine the stereochemical course of the alpha-glucosidase I reaction, the release of glucose from a synthetic trisaccharide substrate, Glc(alpha1-2)Glc(alpha1-3)Glc alphaO(CH2)8COOCH3 was directly monitored by 1H NMR spectroscopy. Both the yeast and bovine mammary gland enzymes released beta-glucose concomitant with the formation of the Glc(alpha1-3)Glc alphaO(CH2)8COOCH3 disaccharide product demonstrating that both enzymes operate with inversion of anomeric configuration.
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Affiliation(s)
- M M Palcic
- Department of Chemistry, University of Alberta, Edmonton, Canada.
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16
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Le XC, Tan W, Scaman CH, Szpacenko A, Arriaga E, Zhang Y, Dovichi NJ, Hindsgaul O, Palcic MM. Single cell studies of enzymatic hydrolysis of a tetramethylrhodamine labeled triglucoside in yeast. Glycobiology 1999; 9:219-25. [PMID: 10024659 DOI: 10.1093/glycob/9.3.219] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Several hundred molecules of enzyme reaction products were detected in a single spheroplast from yeast cells incubated with a tetramethylrhodamine (TMR) labeled triglucoside, alpha-d-Glc(1-->2)alpha-d-Glc(1-->3)alpha-d-Glc-O(CH2)8CONHCH2- CH2NH- COTMR. Product detection was accomplished using capillary electrophoresis and laser induced fluorescence following the introduction of a single spheroplast into the separation capillary. The in vivo enzymatic hydrolysis of the TMR-trisaccharide involves at least two enzymes, limited by processing alpha-glucosidase I, producing TMR-disaccharide, TMR-monosaccharide, and the free TMR-linking arm. Hydrolysis was reduced by preincubation of the cells with the processing enzyme inhibitor castanospermine. Confocal laser scanning microscopy studies confirmed the uptake and internalization of fluorescent substrate. This single cell analysis methodology can be applied for the in vivo assay of any enzyme with a fluorescent substrate.
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Affiliation(s)
- X C Le
- Department of Public Health Sciences, Faculty of Medicine, University of Alberta, Edmonton, Alberta, Canada T6G 2G3
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17
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Abstract
The properties of the N-glycan processing glycosidases located in the endoplasmic reticulum of Saccharomyces cerevisiae are described. alpha-Glucosidase I encoded by CWH41 cleaves the terminal alpha1, 2-linked glucose and alpha-glucosidase II encoded by ROT2 removes the two alpha1,3-linked glucose residues from the Glc3Man9GlcNAc2 oligosaccharide precursor while the alpha1,2-mannosidase encoded by MNS1 removes one specific mannose to form a single isomer of Man8GlcNAc2. Although trimming by these glycosidases is not essential for the formation of N-glycan outer chains, recent studies on mutants lacking these enzymes indicate that alpha-glucosidases I and II play an indirect role in cell wall beta1,6-glucan formation and that the alpha1,2-mannosidase is involved in endoplasmic reticulum quality control. Detailed structure-function studies of recombinant yeast alpha1,2-mannosidase are described that serve as a model for other members of this enzyme family that has been conserved through eukaryotic evolution.
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Affiliation(s)
- A Herscovics
- McGill Cancer Centre, McGill University, 3655 Drummond Street, Montreal, Que. H3G 1Y6, Canada.
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