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De Masi R, Orlando S. GANAB and N-Glycans Substrates Are Relevant in Human Physiology, Polycystic Pathology and Multiple Sclerosis: A Review. Int J Mol Sci 2022; 23:7373. [PMID: 35806376 PMCID: PMC9266668 DOI: 10.3390/ijms23137373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 06/22/2022] [Accepted: 06/28/2022] [Indexed: 11/29/2022] Open
Abstract
Glycans are one of the four fundamental macromolecular components of living matter, and they are highly regulated in the cell. Their functions are metabolic, structural and modulatory. In particular, ER resident N-glycans participate with the Glc3Man9GlcNAc2 highly conserved sequence, in protein folding process, where the physiological balance between glycosylation/deglycosylation on the innermost glucose residue takes place, according GANAB/UGGT concentration ratio. However, under abnormal conditions, the cell adapts to the glucose availability by adopting an aerobic or anaerobic regimen of glycolysis, or to external stimuli through internal or external recognition patterns, so it responds to pathogenic noxa with unfolded protein response (UPR). UPR can affect Multiple Sclerosis (MS) and several neurological and metabolic diseases via the BiP stress sensor, resulting in ATF6, PERK and IRE1 activation. Furthermore, the abnormal GANAB expression has been observed in MS, systemic lupus erythematous, male germinal epithelium and predisposed highly replicating cells of the kidney tubules and bile ducts. The latter is the case of Polycystic Liver Disease (PCLD) and Polycystic Kidney Disease (PCKD), where genetically induced GANAB loss affects polycystin-1 (PC1) and polycystin-2 (PC2), resulting in altered protein quality control and cyst formation phenomenon. Our topics resume the role of glycans in cell physiology, highlighting the N-glycans one, as a substrate of GANAB, which is an emerging key molecule in MS and other human pathologies.
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Affiliation(s)
- Roberto De Masi
- Complex Operative Unit of Neurology, “F. Ferrari” Hospital, Casarano, 73042 Lecce, Italy;
- Laboratory of Neuroproteomics, Multiple Sclerosis Centre, “F. Ferrari” Hospital, Casarano, 73042 Lecce, Italy
| | - Stefania Orlando
- Laboratory of Neuroproteomics, Multiple Sclerosis Centre, “F. Ferrari” Hospital, Casarano, 73042 Lecce, Italy
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2
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Kuribara T, Imagawa A, Hirano M, Ito Y, Totani K. Metabolic syndrome perturbs deglucosylation and reglucosylation in the glycoprotein folding cycle. FEBS Lett 2020; 594:1759-1769. [DOI: 10.1002/1873-3468.13780] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2019] [Revised: 03/05/2020] [Accepted: 03/05/2020] [Indexed: 12/26/2022]
Affiliation(s)
- Taiki Kuribara
- Department of Materials and Life Science Seikei University Musashino Japan
| | - Ayami Imagawa
- Department of Materials and Life Science Seikei University Musashino Japan
| | - Makoto Hirano
- Department of Pharmacy Yasuda Women’s University Hiroshima Japan
| | - Yukishige Ito
- Synthetic Cellular Chemistry Laboratory RIKEN Wako Japan
| | - Kiichiro Totani
- Department of Materials and Life Science Seikei University Musashino Japan
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3
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Caputo AT, Alonzi DS, Marti L, Reca IB, Kiappes JL, Struwe WB, Cross A, Basu S, Lowe ED, Darlot B, Santino A, Roversi P, Zitzmann N. Structures of mammalian ER α-glucosidase II capture the binding modes of broad-spectrum iminosugar antivirals. Proc Natl Acad Sci U S A 2016; 113:E4630-8. [PMID: 27462106 PMCID: PMC4987793 DOI: 10.1073/pnas.1604463113] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The biosynthesis of enveloped viruses depends heavily on the host cell endoplasmic reticulum (ER) glycoprotein quality control (QC) machinery. This dependency exceeds the dependency of host glycoproteins, offering a window for the targeting of ERQC for the development of broad-spectrum antivirals. We determined small-angle X-ray scattering (SAXS) and crystal structures of the main ERQC enzyme, ER α-glucosidase II (α-GluII; from mouse), alone and in complex with key ligands of its catalytic cycle and antiviral iminosugars, including two that are in clinical trials for the treatment of dengue fever. The SAXS data capture the enzyme's quaternary structure and suggest a conformational rearrangement is needed for the simultaneous binding of a monoglucosylated glycan to both subunits. The X-ray structures with key catalytic cycle intermediates highlight that an insertion between the +1 and +2 subsites contributes to the enzyme's activity and substrate specificity, and reveal that the presence of d-mannose at the +1 subsite renders the acid catalyst less efficient during the cleavage of the monoglucosylated substrate. The complexes with iminosugar antivirals suggest that inhibitors targeting a conserved ring of aromatic residues between the α-GluII +1 and +2 subsites would have increased potency and selectivity, thus providing a template for further rational drug design.
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Affiliation(s)
- Alessandro T Caputo
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Dominic S Alonzi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Lucia Marti
- Institute of Sciences of Food Production, Consiglio Nazionale delle Ricerche Unit of Lecce, 73100 Lecce, Italy
| | - Ida-Barbara Reca
- Institute of Sciences of Food Production, Consiglio Nazionale delle Ricerche Unit of Lecce, 73100 Lecce, Italy
| | - J L Kiappes
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Weston B Struwe
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Alice Cross
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Souradeep Basu
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Edward D Lowe
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Benoit Darlot
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom; Ecole Nationale Supérieure de Chimie de Montpellier, 34296 Montpellier Cedex 5, France
| | - Angelo Santino
- Institute of Sciences of Food Production, Consiglio Nazionale delle Ricerche Unit of Lecce, 73100 Lecce, Italy
| | - Pietro Roversi
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
| | - Nicole Zitzmann
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom;
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4
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D'Alessio C, Dahms NM. Glucosidase II and MRH-domain containing proteins in the secretory pathway. Curr Protein Pept Sci 2015; 16:31-48. [PMID: 25692846 DOI: 10.2174/1389203716666150213160438] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2014] [Revised: 08/25/2014] [Accepted: 11/13/2014] [Indexed: 12/24/2022]
Abstract
N-glycosylation in the endoplasmic reticulum (ER) consists of the transfer of a preassembled glycan conserved among species (Glc3Man9GlcNAc2) from a lipid donor to a consensus sequence within a nascent protein that is entering the ER. The protein-linked glycans are then processed by glycosidases and glycosyltransferases in the ER producing specific structures that serve as signalling molecules for the fate of the folding glycoprotein: to stay in the ER during the folding process, to be retrotranslocated to the cytosol for proteasomal degradation if irreversibly misfolded, or to pursue transit through the secretory pathway as a mature glycoprotein. In the ER, each glycan signalling structure is recognized by a specific lectin. A domain similar to that of the mannose 6-phosphate receptors (MPRs) has been identified in several proteins of the secretory pathway. These include the beta subunit of glucosidase II (GII), a key enzyme in the early processing of the transferred glycan that removes middle and innermost glucoses and is involved in quality control of glycoprotein folding in the ER (QC), the lectins OS-9 and XTP3-B, proteins involved in the delivery of ER misfolded proteins to degradation (ERAD), the gamma subunit of the Golgi GlcNAc-1-phosphotransferase, an enzyme involved in generating the mannose 6-phosphate (M6P) signal for sorting acidic hydrolases to lysosomes, and finally the MPRs that deliver those hydrolytic enzymes to the lysosome. Each of the MRH-containing proteins recognizes a different signalling N-glycan structure. Three-dimensional structures of some of the MRH domains have been solved, providing the basis to understand recognition mechanisms.
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Affiliation(s)
| | - Nancy M Dahms
- Laboratory of Glycobiology, Fundación Instituto Leloir - Instituto de Investigaciones Bioquimicas de Buenos Aires-CONICET, Av. Patricias Argentinas 435, C1405BWE, Buenos Aires, Argentina, and School of Sciences, University of Buenos Aires, C1428EHA, Buenos Aires, Argentina.
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5
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Synthesis and α-Glucosidase II inhibitory activity of valienamine pseudodisaccharides relevant to N-glycan biosynthesis. Bioorg Med Chem Lett 2011; 21:5219-23. [DOI: 10.1016/j.bmcl.2011.07.046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 07/11/2011] [Accepted: 07/12/2011] [Indexed: 11/18/2022]
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6
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Takeda Y, Totani K, Matsuo I, Ito Y. The action of bromoconduritol on ER glucosidase II. Bioorg Med Chem Lett 2010; 20:5357-9. [DOI: 10.1016/j.bmcl.2009.05.125] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 05/29/2009] [Accepted: 05/30/2009] [Indexed: 11/26/2022]
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7
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D'Alessio C, Caramelo JJ, Parodi AJ. UDP-GlC:glycoprotein glucosyltransferase-glucosidase II, the ying-yang of the ER quality control. Semin Cell Dev Biol 2010; 21:491-9. [PMID: 20045480 DOI: 10.1016/j.semcdb.2009.12.014] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Accepted: 12/17/2009] [Indexed: 12/22/2022]
Abstract
The N-glycan-dependent quality control of glycoprotein folding prevents endoplasmic to Golgi exit of folding intermediates, irreparably misfolded glycoproteins and incompletely assembled multimeric complexes. It also enhances folding efficiency by preventing aggregation and facilitating formation of proper disulfide bonds. The control mechanism essentially involves four components, resident lectin-chaperones that recognize monoglucosylated polymannose glycans, a lectin-associated oxidoreductase acting on monoglucosylated glycoproteins, a glucosyltransferase that creates monoglucosytlated epitopes in protein-linked glycans and a glucosidase that removes the glucose units added by the glucosyltransferase. This last enzyme is the only mechanism component sensing glycoprotein conformations as it creates monoglucosylated glycans exclusively in not properly folded species or in not completely assembled complexes. The glucosidase is a dimeric heterodimer composed of a catalytic subunit and an additional one that is partially responsible for the ER localization of the enzyme and for the enhancement of the deglucosylation rate as its mannose 6-phosphate receptor homologous domain presents the substrate to the catalytic site. This review deals with our present knowledge on the glucosyltransferase and the glucosidase.
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Affiliation(s)
- Cecilia D'Alessio
- Laboratory of Glycobiology, Fundación Instituto Leloir, Avda. Patricias Argentinas 435, C1405BWE, Buenos Aires, Argentina
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8
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Takeda Y, Totani K, Matsuo I, Ito Y. Chemical approaches toward understanding glycan-mediated protein quality control. Curr Opin Chem Biol 2009; 13:582-91. [DOI: 10.1016/j.cbpa.2009.09.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Revised: 09/01/2009] [Accepted: 09/05/2009] [Indexed: 10/20/2022]
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9
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Stigliano ID, Caramelo JJ, Labriola CA, Parodi AJ, D'Alessio C. Glucosidase II beta subunit modulates N-glycan trimming in fission yeasts and mammals. Mol Biol Cell 2009; 20:3974-84. [PMID: 19605557 DOI: 10.1091/mbc.e09-04-0316] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Glucosidase II (GII) plays a key role in glycoprotein biogenesis in the endoplasmic reticulum (ER). It is responsible for the sequential removal of the two innermost glucose residues from the glycan (Glc(3)Man(9)GlcNAc(2)) transferred to Asn residues in proteins. GII participates in the calnexin/calreticulin cycle; it removes the single glucose unit added to folding intermediates and misfolded glycoproteins by the UDP-Glc:glycoprotein glucosyltransferase. GII is a heterodimer whose alpha subunit (GIIalpha) bears the glycosyl hydrolase active site, whereas its beta subunit (GIIbeta) role is controversial and has been reported to be involved in GIIalpha ER retention and folding. Here, we report that in the absence of GIIbeta, the catalytic subunit GIIalpha of the fission yeast Schizosaccharomyces pombe (an organism displaying a glycoprotein folding quality control mechanism similar to that occurring in mammalian cells) folds to an active conformation able to hydrolyze p-nitrophenyl alpha-d-glucopyranoside. However, the heterodimer is required to efficiently deglucosylate the physiological substrates Glc(2)Man(9)GlcNAc(2) (G2M9) and Glc(1)Man(9)GlcNAc(2) (G1M9). The interaction of the mannose 6-phosphate receptor homologous domain present in GIIbeta and mannoses in the B and/or C arms of the glycans mediates glycan hydrolysis enhancement. We present evidence that also in mammalian cells GIIbeta modulates G2M9 and G1M9 trimming.
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Affiliation(s)
- Ivan D Stigliano
- Laboratories of Glycobiology and Structural Cell Biology, Fundación Instituto Leloir, Consejo Nacional de Investigaciones Científicas y Técnicas, C1405BWE, Buenos Aires, Argentina
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10
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Quinn RP, Mahoney SJ, Wilkinson BM, Thornton DJ, Stirling CJ. A novel role for Gtb1p in glucose trimming of N-linked glycans. Glycobiology 2009; 19:1408-16. [PMID: 19542522 DOI: 10.1093/glycob/cwp087] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Glucosidase II (GluII) is a glycan-trimming enzyme active on nascent glycoproteins in the endoplasmic reticulum (ER). It trims the middle and innermost glucose residues (Glc2 and Glc1) from N-linked glycans. The monoglucosylated glycan produced by the first GluII trimming reaction is recognized by calnexin/calreticulin and serves as the signal for entry into this folding pathway. GluII is a heterodimer of alpha and beta subunits corresponding to yeast Gls2p and Gtb1p, respectively. While Gls2p contains the glucosyl hydrolase active site, the Gtb1p subunit has previously been shown to be essential for the Glc1 trimming event. Here we demonstrate that Gtb1p also determines the rate of Glc2 trimming. In order to further dissect these activities we mutagenized a number of conserved residues across the protein. Our data demonstrate that both the MRH and G2B domains of Gtb1p contribute to the Glc2 trimming event but that the MRH domain is essential for Glc1 trimming.
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Affiliation(s)
- Robert P Quinn
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, UK
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11
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Watanabe T, Totani K, Matsuo I, Maruyama JI, Kitamoto K, Ito Y. Genetic analysis of glucosidase II beta-subunit in trimming of high-mannose-type glycans. Glycobiology 2009; 19:834-40. [PMID: 19395677 DOI: 10.1093/glycob/cwp061] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Glucosidase II (G-II) is a glycoprotein-processing enzyme that successively cleaves two alpha1,3-linked glucose residues from N-linked oligosaccharides in the endoplasmic reticulum. G-II is a heterodimer whose alpha-subunit contains a glycosidase active site, but the function(s) of the beta-subunit remain poorly defined. We report here an in vivo enzymatic analysis using gene disruptants lacking either the G-II alpha- or beta-subunit in the filamentous fungus Aspergillus oryzae. Using synthetic oligosaccharides as probes, G-II activity of the membranous fraction of the gene disruptants was investigated. The fraction lacking the beta-subunit retained hydrolytic activity toward p-nitrophenyl alpha-D-glucopyranoside but was inactive toward both Glc(2)Man(9)GlcNAc(2) and Glc(1)Man(9)GlcNAc(2). When the fraction containing the beta-subunit was added to the one including the alpha-subunit, the glucosidase activity was restored. These results suggested that the beta-subunit confers the substrate specificity toward di- and monoglucosylated glycans on the glucose-trimming activity of the alpha-subunit.
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12
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Carbasugar–thioether pseudodisaccharides related to N-glycan biosynthesis. Carbohydr Res 2009; 344:454-9. [DOI: 10.1016/j.carres.2008.12.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Revised: 12/16/2008] [Accepted: 12/24/2008] [Indexed: 11/20/2022]
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13
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Bosis E, Nachliel E, Cohen T, Takeda Y, Ito Y, Bar-Nun S, Gutman M. Endoplasmic reticulum glucosidase II is inhibited by its end products. Biochemistry 2008; 47:10970-80. [PMID: 18803404 DOI: 10.1021/bi801545d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The calnexin/calreticulin cycle is a quality control system responsible for promoting the folding of newly synthesized glycoproteins entering the endoplasmic reticulum (ER). The association of calnexin and calreticulin with the glycoproteins is regulated by ER glucosidase II, which hydrolyzes Glc 2Man X GlcNAc 2 glycans to Glc 1Man X GlcNAc 2 and further to Glc 0Man X GlcNAc 2 ( X represents any number between 5 and 9). To gain new insights into the reaction mechanism of glucosidase II, we developed a kinetic model that describes the interactions between glucosidase II, calnexin/calreticulin, and the glycans. Our model accurately reconstructed the hydrolysis of glycans with nine mannose residues and glycans with seven mannose residues, as measured by Totani et al. [Totani, K., Ihara, Y., Matsuo, I., and Ito, Y. (2006) J. Biol. Chem. 281, 31502-31508]. Intriguingly, our model predicted that glucosidase II was inhibited by its nonglucosylated end products, where the inhibitory effect of Glc 0Man 7GlcNAc 2 was much stronger than that of Glc 0Man 9GlcNAc 2. These predictions were confirmed experimentally. Moreover, our model suggested that glycans with a different number of mannose residues can be equivalent substrates of glucosidase II, in contrast to what had been previously thought. We discuss the possibility that nonglucosylated glycans, existing in the ER, might regulate the entry of newly synthesized glycoproteins into the calnexin/calreticulin cycle. Our model also shows that glucosidase II does not interact with monoglucosylated glycans while they are bound to calnexin or calreticulin.
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Affiliation(s)
- Eran Bosis
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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14
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Schallus T, Jaeckh C, Fehér K, Palma AS, Liu Y, Simpson JC, Mackeen M, Stier G, Gibson TJ, Feizi T, Pieler T, Muhle-Goll C. Malectin: a novel carbohydrate-binding protein of the endoplasmic reticulum and a candidate player in the early steps of protein N-glycosylation. Mol Biol Cell 2008; 19:3404-14. [PMID: 18524852 DOI: 10.1091/mbc.e08-04-0354] [Citation(s) in RCA: 212] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
N-Glycosylation starts in the endoplasmic reticulum (ER) where a 14-sugar glycan composed of three glucoses, nine mannoses, and two N-acetylglucosamines (Glc(3)Man(9)GlcNAc(2)) is transferred to nascent proteins. The glucoses are sequentially trimmed by ER-resident glucosidases. The Glc(3)Man(9)GlcNAc(2) moiety is the substrate for oligosaccharyltransferase; the Glc(1)Man(9)GlcNAc(2) and Man(9)GlcNAc(2) intermediates are signals for glycoprotein folding and quality control in the calnexin/calreticulin cycle. Here, we report a novel membrane-anchored ER protein that is highly conserved in animals and that recognizes the Glc(2)-N-glycan. Structure determination by nuclear magnetic resonance showed that its luminal part is a carbohydrate binding domain that recognizes glucose oligomers. Carbohydrate microarray analyses revealed a uniquely selective binding to a Glc(2)-N-glycan probe. The localization, structure, and binding specificity of this protein, which we have named malectin, open the way to studies of its role in the genesis, processing and secretion of N-glycosylated proteins.
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Affiliation(s)
- Thomas Schallus
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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15
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How sugars convey information on protein conformation in the endoplasmic reticulum. Semin Cell Dev Biol 2007; 18:732-42. [PMID: 17997334 DOI: 10.1016/j.semcdb.2007.09.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2007] [Revised: 07/24/2007] [Accepted: 09/05/2007] [Indexed: 11/21/2022]
Abstract
The N-glycan-dependent quality control of glycoprotein folding prevents endoplasmic reticulum to Golgi exit of folding intermediates, irreparably misfolded glycoproteins and not completely assembled multimeric complexes. It also enhances folding efficiency by preventing aggregation and facilitating formation of proper disulfide bonds. The control mechanism essentially involves four components, resident lectin-chaperones that recognize monoglucosylated polymannose glycans, a lectin-associated oxidoreductase acting on monoglucosylated glycoproteins, a glucosyltransferase and a glucosidase that creates monoglucosylated epitopes in glycans transferred in protein N-glycosylation or removes the glucose units added by the glucosyltransferase. This last enzyme is the only mechanism component sensing glycoprotein conformations as it creates monoglucosylated glycans exclusively in not properly folded species or in not completely assembled complexes. The purpose of the review is to describe the most significant recent findings on the mechanism of glycoprotein folding and assembly quality control and to discuss the main still unanswered questions.
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16
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Totani K, Ihara Y, Matsuo I, Ito Y. Substrate Specificity Analysis of Endoplasmic Reticulum Glucosidase II Using Synthetic High Mannose-type Glycans. J Biol Chem 2006. [DOI: 10.1016/s0021-9258(19)84063-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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17
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Totani K, Ihara Y, Matsuo I, Ito Y. Substrate Specificity Analysis of Endoplasmic Reticulum Glucosidase II Using Synthetic High Mannose-type Glycans. J Biol Chem 2006; 281:31502-8. [PMID: 16940048 DOI: 10.1074/jbc.m605457200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Glucosidase II (Glc'ase II) is a glycan-processing enzyme that trims two alpha1,3-linked Glc residues in succession from the glycoprotein oligosaccharide Glc2Man9GlcNAc2 to give Glc1Man9GlcNAc2 and Man9GlcNAc2 in the endoplasmic reticulum (ER). Monoglucosylated glycans, such as Glc1-Man9GlcNAc2, generated by this process play a key role in glycoprotein quality control in the ER, because they are primary ligands for the lectin chaperones calnexin (CNX) and calreticulin (CRT). A precise analysis of the substrate specificity of Glc'ase II is expected to further our understanding of the molecular basis to glycoprotein quality control, because Glc'ase II potentially competes with CNX/CRT for the same glycans, Glc1Man7-9GlcNAc2. In this study, a quantitative analysis of the specificity of Glc'ase II using a series of structurally defined synthetic glycans was carried out. In the presence of CRT, Glc'ase II-mediated trimming from Glc2Man9GlcNAc2 stopped at Glc1Man9GlcNAc2, supporting the notion that the glycan structure delivered to the CNX/CRT cycle is Glc1Man9GlcNAc2. Unexpectedly, our experiments showed that Glc1Man8(B)GlcNAc2 had nearly the same reactivity as Glc1Man9GlcNAc2, which was markedly greater than that of its positional isomer Glc1Man8(C)GlcNAc2. An analysis with glycoprotein-like probes revealed the stepwise formation of Glc1Man9GlcNAc2 and Man9GlcNAc2 from Glc2Man9GlcNAc2, even in the presence of CRT. It was also shown that Glc1Man8(B)GlcNAc2 had even greater reactivity than Glc1Man9GlcNAc2 at the glycoprotein level. Moreover, inhibitory activities by nonglucosylated glycans suggested that Glc'ase II recognized the C arm (Manalpha1, 2Manalpha1, 6Man-) of high mannose-type glycans.
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Affiliation(s)
- Kiichiro Totani
- RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan
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18
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Wilkinson BM, Purswani J, Stirling CJ. Yeast GTB1 Encodes a Subunit of Glucosidase II Required for Glycoprotein Processing in the Endoplasmic Reticulum. J Biol Chem 2006; 281:6325-33. [PMID: 16373354 DOI: 10.1074/jbc.m510455200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Glucosidase II is essential for sequential removal of two glucose residues from N-linked glycans during glycoprotein biogenesis in the endoplasmic reticulum. The enzyme is a heterodimer whose alpha-subunit contains the glycosyl hydrolase active site. The function of the beta-subunit has yet to be defined, but mutations in the human gene have been linked to an autosomal dominant form of polycystic liver disease. Here we report the identification and characterization of a Saccharomyces cerevisiae gene, GTB1, encoding a polypeptide with 21% sequence similarity to the beta-subunit of human glucosidase II. The Gtb1 protein was shown to be a soluble glycoprotein (96-102 kDa) localized to the endoplasmic reticulum lumen where it was present in a complex together with the yeast alpha-subunit homologue Gls2p. Surprisingly, we found that Deltagtb1 mutant cells were specifically defective in the processing of monoglucosylated glycans. Thus, although Gls2p is sufficient for cleavage of the penultimate glucose residue, Gtb1p is essential for cleavage of the final glucose. Our data demonstrate that Gtb1p is required for normal glycoprotein biogenesis and reveal that the final two glucose-trimming steps in N-glycan processing are mechanistically distinct.
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Affiliation(s)
- Barrie M Wilkinson
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
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Geysens S, Pakula T, Uusitalo J, Dewerte I, Penttilä M, Contreras R. Cloning and characterization of the glucosidase II alpha subunit gene of Trichoderma reesei: a frameshift mutation results in the aberrant glycosylation profile of the hypercellulolytic strain Rut-C30. Appl Environ Microbiol 2005; 71:2910-24. [PMID: 15932985 PMCID: PMC1151825 DOI: 10.1128/aem.71.6.2910-2924.2005] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
We describe isolation and characterization of the gene encoding the glucosidase II alpha subunit (GIIalpha) of the industrially important fungus Trichoderma reesei. This subunit is the catalytic part of the glucosidase II heterodimeric enzyme involved in the structural modification within the endoplasmic reticulum (ER) of N-linked oligosaccharides present on glycoproteins. The gene encoding GIIalpha (gls2alpha) in the hypercellulolytic strain Rut-C30 contains a frameshift mutation resulting in a truncated gene product. Based on the peculiar monoglucosylated N-glycan pattern on proteins produced by the strain, we concluded that the truncated protein can still hydrolyze the first alpha-1,3-linked glucose residue but not the innermost alpha-1,3-linked glucose residue from the Glc2Man9GlcNAc2 N-glycan ER structure. Transformation of the Rut-C30 strain with a repaired T. reesei gls2alpha gene changed the glycosylation profile significantly, decreasing the amount of monoglucosylated structures and increasing the amount of high-mannose N-glycans. Full conversion to high-mannose carbohydrates was not obtained, and this was probably due to competition between the endogenous mutant subunit and the introduced wild-type GIIalpha protein. Since glucosidase II is also involved in the ER quality control of nascent polypeptide chains, its transcriptional regulation was studied in a strain producing recombinant tissue plasminogen activator (tPA) and in cultures treated with the stress agents dithiothreitol (DTT) and brefeldin A (BFA), which are known to block protein transport and to induce the unfolded protein response. While the mRNA levels were clearly upregulated upon tPA production or BFA treatment, no such enhancement was observed after DTT addition.
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Affiliation(s)
- Steven Geysens
- Fundamental and Applied Molecular Biology, Department for Molecular Biomedical Research, Ghent University and VIB (Flemish Interuniversity Institute for Biotechnology), Ghent-Zwijnaarde, Belgium
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Deprez P, Gautschi M, Helenius A. More Than One Glycan Is Needed for ER Glucosidase II to Allow Entry of Glycoproteins into the Calnexin/Calreticulin Cycle. Mol Cell 2005; 19:183-95. [PMID: 16039588 DOI: 10.1016/j.molcel.2005.05.029] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Revised: 05/04/2005] [Accepted: 05/27/2005] [Indexed: 10/25/2022]
Abstract
Nascent and newly synthesized glycoproteins enter the calnexin (Cnx)/calreticulin (Crt) cycle when two out of three glucoses in the core N-linked glycans have been trimmed sequentially by endoplasmic reticulum (ER) glucosidases I (GI) and II (GII). By analyzing arrested glycopeptides in microsomes, we found that GI removed the outermost glucose immediately after glycan addition. However, although GII associated with singly glycosylated nascent chains, trimming of the second glucose only occurred efficiently when a second glycan was present in the chain. Consistent with a requirement for multiple glycans to activate GII, pancreatic RNase in live cells needed more than one glycan to enter the Cnx/Crt cycle. Thus, whereas GI trimming occurs as an automatic extension of glycosylation, trimming by GII is a regulated process. By adjusting the number and location of glycans, glycoproteins can instruct the cell to engage them in an individually determined folding and quality control pathway.
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Affiliation(s)
- Paola Deprez
- Institute of Biochemistry, Swiss Federal Institute of Technology (ETH) Zurich, Switzerland
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21
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Stereoselective ring-opening reactions with AcBr and AcCl. A new method for preparation of some haloconduritols. Tetrahedron 2004. [DOI: 10.1016/j.tet.2003.11.054] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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22
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Baran A, Kazaz C, Seçen H, Sütbeyaz Y. Synthesis of haloconduritols from an endo-cycloadduct of furan and vinylene carbonate. Tetrahedron 2003. [DOI: 10.1016/s0040-4020(03)00510-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Roth J, Ziak M, Zuber C. The role of glucosidase II and endomannosidase in glucose trimming of asparagine-linked oligosaccharides. Biochimie 2003; 85:287-94. [PMID: 12770767 DOI: 10.1016/s0300-9084(03)00049-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
This review covers various aspects of glucose trimming reactions occurring on asparagine-linked oligosaccharides. Structural and functional features of two enzymes, glucosidase II and endo-alpha-mannosidase, prominently involved in this process are summarized and their striking differences in terms of substrate specificities are highlighted. Recent results of analyses by immunoelectron microscopy of their distribution pattern are presented which demonstrate that glucose trimming is not restricted to the endoplasmic reticulum (ER) but additionally is a function accommodated by the Golgi apparatus. The mutually exclusive subcellular distribution of glucosidase II and endomannosidase are discussed in terms of their significance for quality control of protein folding and N-glycosylation.
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Affiliation(s)
- Jürgen Roth
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, Switzerland.
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Roth J. Protein N-glycosylation along the secretory pathway: relationship to organelle topography and function, protein quality control, and cell interactions. Chem Rev 2002; 102:285-303. [PMID: 11841244 DOI: 10.1021/cr000423j] [Citation(s) in RCA: 334] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Jürgen Roth
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, CH-8091 Zurich, Switzerland.
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Salvucci M. Effect of the alpha-glucosidase inhibitor, bromoconduritol, on carbohydrate metabolism in the silverleaf whitefly, Bemisia argentifolii. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2000; 45:117-128. [PMID: 11169751 DOI: 10.1002/1520-6327(200011)45:3<117::aid-arch3>3.0.co;2-t] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The involvement of alpha-glucosidase in the partitioning of ingested sucrose between excretion and incorporation was investigated in the silverleaf whitefly (Bemisia argentifolii). Approximately half of the alpha-glucosidase activity in adult whiteflies was soluble and the remainder was associated with membranes. In contrast, almost all of the trehalulose synthase was membrane-associated. Isoelectric focusing revealed that soluble and membrane-associated alpha-glucosidases were each composed of several isozymes in the pH 5 to 6.5 range, but the distribution of activity among the various isozymes was different. Bromoconduritol, an inhibitor of glucosidases, inhibited trehalulose synthase and alpha-glucosidase activities in whitefly extracts. Inhibition was greatest when bromoconduritol was incubated with extracts prior to the addition of sucrose, consistent with the irreversible nature of this inhibitor. Addition of bromoconduritol to artificial diets decreased the extractable trehalulose synthase and alpha-glucosidase activities by about 30 and 50%, respectively. Ingestion of bromoconduritol reduced the amount of carbohydrate excreted by about 80% without changing the distribution of the major honeydew sugars or causing an increase in the proportion of sucrose that was excreted. Ingestion of bromoconduritol did not affect respiration, the content and distribution of soluble carbohydrates in whitefly bodies, or the conversion of labeled sucrose into glucose, trehalose and isobemisiose. The results indicate that partitioning of ingested carbon between excretion and metabolism in whiteflies is highly regulated, probably involving multiple forms of alpha-glucosidase that facilitate a separation of the processes involved in the metabolic utilization of sucrose from those involved in excretion of excess carbohydrate. Arch. Insect Biochem. Physiol. 45:117-128, 2000. Published 2001 Wiley-Liss, Inc.
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Affiliation(s)
- M Salvucci
- U.S. Department of Agriculture, Agricultural Research Service, Western Cotton Research Laboratory, Phoenix, Arizona 85040-8830, USA.
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Pelletier MF, Marcil A, Sevigny G, Jakob CA, Tessier DC, Chevet E, Menard R, Bergeron JJ, Thomas DY. The heterodimeric structure of glucosidase II is required for its activity, solubility, and localization in vivo. Glycobiology 2000; 10:815-27. [PMID: 10929008 DOI: 10.1093/glycob/10.8.815] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Glucosidase II is an ER heterodimeric enzyme that cleaves sequentially the two innermost alpha-1,3-linked glucose residues from N-linked oligosaccharides on nascent glycoproteins. This processing allows the binding and release of monoglucosylated (Glc(1)Man(9)GlcNAc(2)) glycoproteins with calnexin and calreticulin, the lectin-like chaperones of the endoplasmic reticulum. We have isolated two cDNA isoforms of the human alpha subunit (alpha1 and alpha2) differing by a 66 bp stretch, and a cDNA for the corresponding beta subunit. The alpha1 and alpha2 forms have distinct mobilities on SDS-PAGE and are expressed in most of the cell lines we have tested, but were absent from the glucosidase II-deficient cell line PHA(R) 2.7. Using COS7 cells, the coexpression of the beta subunit with the catalytic alpha subunit was found to be essential for enzymatic activity, solubilization, and/or stability, and ER retention of the alpha/beta complex. Transfected cell extracts expressing either alpha1 or alpha2 forms with the beta subunit showed similar activities, while mutating( )the nucleophile (D542N) predicted from the glycoside hydrolase Family 31 active site consensus sequence abolished enzymatic activity. In order to compare the kinetic parameters of both alpha1/beta and alpha2/beta forms of human glucosidase II the protein was expressed with the baculovirus expression system. Expression of the human alpha or beta subunit alone led to the formation of active human/insect heteroenzymes, demonstrating functional complementation by the endogenous insect glucosidase II subunits. The activity of both forms of recombinant human glucosidase II was examined with a p-nitrophenyl alpha-D-glucopyranoside substrate, and a two binding site kinetic model for this substrate was shown. The K(M1-2) values and apparent K(i1-2 )for deoxynojirimycin and castanospermine were determined and found to be identical for both isoforms suggesting they have similar catalysis and inhibition characteristics. The substrate specificities of both isoforms using the physiological oligosaccharides were assessed and found to be similar.
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Affiliation(s)
- M F Pelletier
- Genetics Group and Enzymology Group, Biotechnology Research Institute, National Research Council of Canada, Montreal H4P 2R2, Canada
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Jakob CA, Burda P, Roth J, Aebi M. Degradation of misfolded endoplasmic reticulum glycoproteins in Saccharomyces cerevisiae is determined by a specific oligosaccharide structure. J Biophys Biochem Cytol 1998; 142:1223-33. [PMID: 9732283 PMCID: PMC2149342 DOI: 10.1083/jcb.142.5.1223] [Citation(s) in RCA: 259] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In Saccharomyces cerevisiae, transfer of N-linked oligosaccharides is immediately followed by trimming of ER-localized glycosidases. We analyzed the influence of specific oligosaccharide structures for degradation of misfolded carboxypeptidase Y (CPY). By studying the trimming reactions in vivo, we found that removal of the terminal alpha1,2 glucose and the first alpha1,3 glucose by glucosidase I and glucosidase II respectively, occurred rapidly, whereas mannose cleavage by mannosidase I was slow. Transport and maturation of correctly folded CPY was not dependent on oligosaccharide structure. However, degradation of misfolded CPY was dependent on specific trimming steps. Degradation of misfolded CPY with N-linked oligosaccharides containing glucose residues was less efficient compared with misfolded CPY bearing the correctly trimmed Man8GlcNAc2 oligosaccharide. Reduced rate of degradation was mainly observed for misfolded CPY bearing Man6GlcNAc2, Man7GlcNAc2 and Man9GlcNAc2 oligosaccharides, whereas Man8GlcNAc2 and, to a lesser extent, Man5GlcNAc2 oligosaccharides supported degradation. These results suggest a role for the Man8GlcNAc2 oligosaccharide in the degradation process. They may indicate the presence of a Man8GlcNAc2-binding lectin involved in targeting of misfolded glycoproteins to degradation in S. cerevisiae.
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Affiliation(s)
- C A Jakob
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zürich, CH-8091 Zürich, Switzerland
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Febbraio F, Barone R, D'Auria S, Rossi M, Nucci R, Piccialli G, De Napoli L, Orrù S, Pucci P. Identification of the active site nucleophile in the thermostable beta-glycosidase from the archaeon Sulfolobus solfataricus expressed in Escherichia coli. Biochemistry 1997; 36:3068-75. [PMID: 9115982 DOI: 10.1021/bi962496w] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Sulfolobus solfataricus beta-glycosidase expressed in Escherichia coli was fully inactivated at 65 degrees C, according to pseudo-first-order kinetics, by [3H]conduritol B epoxide (DL-1,2 anhydro-myo-inositol) synthesized as the active site directed inhibitor by a slight modification of Legler's procedure [Legler, G. (1977) Methods Enzymol. 46, 368-381]. The determination of kinetic constants for the inactivation showed that the process took place through the formation of a stabilized inhibitor-enzyme intermediate. Inactivation and reactivation studies suggested that the inhibitor-enzyme intermediate complex was formed more rapidly and hydrolyzed at a lower rate than it was for other glycosidases. Moreover, the stoichiometry of the binding, determined by electrospray mass spectrometric analysis, revealed that one molecule of the inhibitor was covalently bound to each enzyme subunit. The binding site for [3H]conduritol B epoxide was identified by the isolation and partial sequence analysis of the radioactive peptide obtained by cyanogen bromide and pepsin digests. Electrospray tandem mass analysis of the labeled peptide showed that the inhibitor was covalently bound to E387. This result, in agreement with data obtained from sequence alignments of S. solfataricus beta-glycosidase with other gluco- and galactosidases of the glycosyl hydrolase family 1 [Henrissat, B. (1991) Biochem. J. 280, 309-316], indicates that the conserved E387 is the nucleophilic amino acid residue in the active site of the enzyme.
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Affiliation(s)
- F Febbraio
- Institute of Protein Biochemistry and Enzymology, CNR, Naples, Italy
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