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Tyrrell BE, Kumar A, Gangadharan B, Alonzi D, Brun J, Hill M, Bharucha T, Bosworth A, Graham V, Dowall S, Miller JL, Zitzmann N. Exploring the Potential of Iminosugars as Antivirals for Crimean-Congo Haemorrhagic Fever Virus, Using the Surrogate Hazara Virus: Liquid-Chromatography-Based Mapping of Viral N-Glycosylation and In Vitro Antiviral Assays. Pathogens 2023; 12:399. [PMID: 36986321 PMCID: PMC10057787 DOI: 10.3390/pathogens12030399] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Revised: 02/09/2023] [Accepted: 02/22/2023] [Indexed: 03/06/2023] Open
Abstract
Crimean-Congo haemorrhagic fever virus (CCHFV) is a pathogen of increasing public health concern, being a widely distributed arbovirus and the causative agent of the potentially fatal Crimean-Congo haemorrhagic fever. Hazara virus (HAZV) is a genetically and serologically related virus that has been proposed as a surrogate for antiviral and vaccine testing for CCHFV. Glycosylation analysis of HAZV has been limited; first, we confirmed for the first time the occupation of two N-glycosylation sites in the HAZV glycoprotein. Despite this, there was no apparent antiviral efficacy of a panel of iminosugars against HAZV, as determined by quantification of the total secretion and infectious virus titres produced following infection of SW13 and Vero cells. This lack of efficacy was not due to an inability of deoxynojirimycin (DNJ)-derivative iminosugars to access and inhibit endoplasmic reticulum α-glucosidases, as demonstrated by free oligosaccharide analysis in uninfected and infected SW13 and uninfected Vero cells. Even so, iminosugars may yet have potential as antivirals for CCHFV since the positions and importance of N-linked glycans may differ between the viruses, a hypothesis requiring further evaluation.
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Affiliation(s)
- Beatrice E. Tyrrell
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Abhinav Kumar
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Bevin Gangadharan
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Dominic Alonzi
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Juliane Brun
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Michelle Hill
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Tehmina Bharucha
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Andrew Bosworth
- UK Health Security Agency (UKHSA), Porton Down, Salisbury SP4 0JG, UK
| | - Victoria Graham
- UK Health Security Agency (UKHSA), Porton Down, Salisbury SP4 0JG, UK
| | - Stuart Dowall
- UK Health Security Agency (UKHSA), Porton Down, Salisbury SP4 0JG, UK
| | - Joanna L. Miller
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
| | - Nicole Zitzmann
- Department of Biochemistry and Kavli Institute for Nanoscience Discovery, University of Oxford, Oxford OX1 3QU, UK
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Burchill L, Males A, Kaur A, Davies GJ, Williams SJ. Structure, Function and Mechanism of N‐Glycan Processing Enzymes:
endo
‐α‐1,2‐Mannanase and
endo
‐α‐1,2‐Mannosidase. Isr J Chem 2022. [DOI: 10.1002/ijch.202200067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Laura Burchill
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute University of Melbourne Parkville Victoria Australia 3010
| | - Alexandra Males
- Department of Chemistry University of York York YO10 5DD United Kingdom
| | - Arashdeep Kaur
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute University of Melbourne Parkville Victoria Australia 3010
| | - Gideon J. Davies
- Department of Chemistry University of York York YO10 5DD United Kingdom
| | - Spencer J. Williams
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute University of Melbourne Parkville Victoria Australia 3010
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3
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Kuribara T, Usui R, Totani K. Glycan structure-based perspectives on the entry and release of glycoproteins in the calnexin/calreticulin cycle. Carbohydr Res 2021; 502:108273. [PMID: 33713911 DOI: 10.1016/j.carres.2021.108273] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 02/16/2021] [Accepted: 02/23/2021] [Indexed: 12/16/2022]
Abstract
N-glycans are attached to newly synthesised polypeptides and are involved in the folding, secretion, and degradation of N-linked glycoproteins. In particular, the calnexin/calreticulin cycle, which is the central mechanism of the entry and release of N-linked glycoproteins depending on the folding sates, has been well studied. In addition to biological studies on the calnexin/calreticulin cycle, several studies have revealed complementary roles of in vitro chemistry-based research in the structure-based understanding of the cycle. In this mini-review, we summarise chemistry-based results and highlight their importance for further understanding of the cycle.
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Affiliation(s)
- Taiki Kuribara
- Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1 Kichijoji-kitamachiMusashino-shi, Tokyo, 180-8633, Japan
| | - Ruchio Usui
- Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1 Kichijoji-kitamachiMusashino-shi, Tokyo, 180-8633, Japan
| | - Kiichiro Totani
- Department of Materials and Life Science, Faculty of Science and Technology, Seikei University, 3-3-1 Kichijoji-kitamachiMusashino-shi, Tokyo, 180-8633, Japan.
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Abstract
Folding of proteins is essential so that they can exert their functions. For proteins that transit the secretory pathway, folding occurs in the endoplasmic reticulum (ER) and various chaperone systems assist in acquiring their correct folding/subunit formation. N-glycosylation is one of the most conserved posttranslational modification for proteins, and in eukaryotes it occurs in the ER. Consequently, eukaryotic cells have developed various systems that utilize N-glycans to dictate and assist protein folding, or if they consistently fail to fold properly, to destroy proteins for quality control and the maintenance of homeostasis of proteins in the ER.
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Structure of human endo-α-1,2-mannosidase (MANEA), an antiviral host-glycosylation target. Proc Natl Acad Sci U S A 2020; 117:29595-29601. [PMID: 33154157 PMCID: PMC7703563 DOI: 10.1073/pnas.2013620117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mammalian protein N-linked glycosylation is critical for glycoprotein folding, quality control, trafficking, recognition, and function. N-linked glycans are synthesized from Glc3Man9GlcNAc2 precursors that are trimmed and modified in the endoplasmic reticulum (ER) and Golgi apparatus by glycoside hydrolases and glycosyltransferases. Endo-α-1,2-mannosidase (MANEA) is the sole endo-acting glycoside hydrolase involved in N-glycan trimming and is located within the Golgi, where it allows ER-escaped glycoproteins to bypass the classical N-glycosylation trimming pathway involving ER glucosidases I and II. There is considerable interest in the use of small molecules that disrupt N-linked glycosylation as therapeutic agents for diseases such as cancer and viral infection. Here we report the structure of the catalytic domain of human MANEA and complexes with substrate-derived inhibitors, which provide insight into dynamic loop movements that occur on substrate binding. We reveal structural features of the human enzyme that explain its substrate preference and the mechanistic basis for catalysis. These structures have inspired the development of new inhibitors that disrupt host protein N-glycan processing of viral glycans and reduce the infectivity of bovine viral diarrhea and dengue viruses in cellular models. These results may contribute to efforts aimed at developing broad-spectrum antiviral agents and help provide a more in-depth understanding of the biology of mammalian glycosylation.
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6
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α-glucosidase inhibitors as host-directed antiviral agents with potential for the treatment of COVID-19. Biochem Soc Trans 2020; 48:1287-1295. [PMID: 32510142 DOI: 10.1042/bst20200505] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 04/28/2020] [Accepted: 05/11/2020] [Indexed: 01/12/2023]
Abstract
The ongoing COVID-19 pandemic, caused by SARS-CoV-2, has pushed the health systems of many countries to breaking point and precipitated social distancing measures that have crippled economic activities across the globe. A return to normality is unlikely until effective therapeutics and a vaccine are available. The immediacy of this problem suggests that drug strategies should focus on repurposing approved drugs or late-stage clinical candidates, as these have the shortest path to use in the clinic. Here, we review and discuss the role of host cell N-glycosylation pathways to virus replication and the drugs available to disrupt these pathways. In particular, we make a case for evaluation of the well-tolerated drugs miglitol, celgosivir and especially miglustat for the treatment of COVID-19.
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Abstract
The site of protein folding and maturation for the majority of proteins that are secreted, localized to the plasma membrane or targeted to endomembrane compartments is the endoplasmic reticulum (ER). It is essential that proteins targeted to the ER are properly folded in order to carry out their function, as well as maintain protein homeostasis, as accumulation of misfolded proteins could lead to the formation of cytotoxic aggregates. Because protein folding is an error-prone process, the ER contains protein quality control networks that act to optimize proper folding and trafficking of client proteins. If a protein is unable to reach its native state, it is targeted for ER retention and subsequent degradation. The protein quality control networks of the ER that oversee this evaluation or interrogation process that decides the fate of maturing nascent chains is comprised of three general types of families: the classical chaperones, the carbohydrate-dependent system, and the thiol-dependent system. The cooperative action of these families promotes protein quality control and protein homeostasis in the ER. This review will describe the families of the ER protein quality control network and discuss the functions of individual members.
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Affiliation(s)
- Benjamin M Adams
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 240 Thatcher Road, Amherst, MA, 01003, USA
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA, 01003, USA
| | - Michela E Oster
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 240 Thatcher Road, Amherst, MA, 01003, USA
| | - Daniel N Hebert
- Department of Biochemistry and Molecular Biology, University of Massachusetts, 240 Thatcher Road, Amherst, MA, 01003, USA.
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA, 01003, USA.
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Mechanisms of Antiviral Activity of Iminosugars Against Dengue Virus. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1062:277-301. [PMID: 29845540 PMCID: PMC7121742 DOI: 10.1007/978-981-10-8727-1_20] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The antiviral mechanism of action of iminosugars against many enveloped viruses, including dengue virus (DENV), HIV, influenza and hepatitis C virus, is believed to be mediated by inducing misfolding of viral N-linked glycoproteins through inhibition of host endoplasmic reticulum-resident α-glucosidase enzymes. This leads to reduced secretion and/or infectivity of virions and hence lower viral titres, both in vitro and in vivo. Free oligosaccharide analysis from iminosugar-treated cells shows that antiviral activity correlates with production of mono- and tri-glucosylated sugars, indicative of inhibition of ER α-glucosidases. We demonstrate that glucose-mimicking iminosugars inhibit isolated glycoprotein and glycolipid processing enzymes and that this inhibition also occurs in primary cells treated with these drugs. Galactose-mimicking iminosugars that have been tested do not inhibit glycoprotein processing but do inhibit glycolipid processing, and are not antiviral against DENV. By comparison, the antiviral activity of glucose-mimetic iminosugars that inhibit endoplasmic reticulum-resident α-glucosidases, but not glycolipid processing, demonstrates that inhibition of α-glucosidases is responsible for iminosugar antiviral activity against DENV. This monograph will review the investigations of many researchers into the mechanisms of action of iminosugars and the contribution of our current understanding of these mechanisms for optimising clinical delivery of iminosugars. The effects of iminosugars on enzymes other than glucosidases, the induction of ER stress and viral receptors will be also put into context. Data suggest that inhibition of α-glucosidases results in inhibited release of virus and is the primary antiviral mechanism of action of iminosugars against DENV.
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Tyrrell BE, Sayce AC, Warfield KL, Miller JL, Zitzmann N. Iminosugars: Promising therapeutics for influenza infection. Crit Rev Microbiol 2017; 43:521-545. [PMID: 27931136 PMCID: PMC5470110 DOI: 10.1080/1040841x.2016.1242868] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 09/02/2016] [Accepted: 09/27/2016] [Indexed: 01/11/2023]
Abstract
Influenza virus causes three to five million severe respiratory infections per year in seasonal epidemics, and sporadic pandemics, three of which occurred in the twentieth century and are a continuing global threat. Currently licensed antivirals exclusively target the viral neuraminidase or M2 ion channel, and emerging drug resistance necessitates the development of novel therapeutics. It is believed that a host-targeted strategy may combat the development of antiviral drug resistance. To this end, a class of molecules known as iminosugars, hydroxylated carbohydrate mimics with the endocyclic oxygen atom replaced by a nitrogen atom, are being investigated for their broad-spectrum antiviral potential. The influenza virus glycoproteins, hemagglutinin and neuraminidase, are susceptible to inhibition of endoplasmic reticulum α-glucosidases by certain iminosugars, leading to reduced virion production or infectivity, demonstrated by in vitro and in vivo studies. In some experiments, viral strain-specific effects are observed. Iminosugars may also inhibit other host and virus targets with antiviral consequences. While investigations of anti-influenza iminosugar activities have been conducted since the 1980s, recent successes of nojirimycin derivatives have re-invigorated investigation of the therapeutic potential of iminosugars as orally available, low cytotoxicity, effective anti-influenza drugs.
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Affiliation(s)
- Beatrice Ellen Tyrrell
- Department of Biochemistry, University of Oxford Medical Sciences DivisionOxfordUnited Kingdom of Great Britain and Northern Ireland
| | - Andrew Cameron Sayce
- Department of Biochemistry, University of Oxford Medical Sciences DivisionOxfordUnited Kingdom of Great Britain and Northern Ireland
| | - Kelly Lyn Warfield
- Antiviral Research and Development, Emergent BioSolutions IncGaithersburgMDUnited States
| | - Joanna Louise Miller
- Department of Biochemistry, University of Oxford Medical Sciences DivisionOxfordUnited Kingdom of Great Britain and Northern Ireland
| | - Nicole Zitzmann
- Department of Biochemistry, University of Oxford Medical Sciences DivisionOxfordUnited Kingdom of Great Britain and Northern Ireland
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10
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Warfield KL, Barnard DL, Enterlein SG, Smee DF, Khaliq M, Sampath A, Callahan MV, Ramstedt U, Day CW. The Iminosugar UV-4 is a Broad Inhibitor of Influenza A and B Viruses ex Vivo and in Mice. Viruses 2016; 8:71. [PMID: 27072420 PMCID: PMC4810261 DOI: 10.3390/v8030071] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 02/11/2016] [Accepted: 02/16/2016] [Indexed: 12/02/2022] Open
Abstract
Iminosugars that are competitive inhibitors of endoplasmic reticulum (ER) α-glucosidases have been demonstrated to have antiviral activity against a diverse set of viruses. A novel iminosugar, UV-4B, has recently been shown to provide protection against lethal infections with dengue and influenza A (H1N1) viruses in mice. In the current study, the breadth of activity of UV-4B against influenza was examined ex vivo and in vivo. Efficacy of UV-4B against influenza A and B viruses was shown in primary human bronchial epithelial cells, a principal target tissue for influenza. Efficacy of UV-4B against influenza A (H1N1 and H3N2 subtypes) and influenza B was demonstrated using multiple lethal mouse models with readouts including mortality and weight loss. Clinical trials are ongoing to demonstrate safety of UV-4B and future studies to evaluate antiviral activity against influenza in humans are planned.
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Affiliation(s)
| | - Dale L Barnard
- Institute for Antiviral Research, Utah State University, Logan, UT 84322-5600, USA.
| | | | - Donald F Smee
- Institute for Antiviral Research, Utah State University, Logan, UT 84322-5600, USA.
| | | | | | - Michael V Callahan
- Division of Infectious Diseases, Massachusetts General Hospital/Harvard Medical School, Boston, MA 02114, USA.
- Unither Virology, LLC, Silver Spring, MD 20910, USA.
| | | | - Craig W Day
- Institute for Antiviral Research, Utah State University, Logan, UT 84322-5600, USA.
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11
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Levy-Ontman O, Fisher M, Shotland Y, Tekoah Y, Malis Arad S. Insight into glucosidase II from the red marine microalga Porphyridium sp. (Rhodophyta). JOURNAL OF PHYCOLOGY 2015; 51:1075-87. [PMID: 26987003 DOI: 10.1111/jpy.12341] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 07/29/2015] [Indexed: 05/21/2023]
Abstract
N-glycosylation of proteins is one of the most important post-translational modifications that occur in various organisms, and is of utmost importance for protein function, stability, secretion, and loca-lization. Although the N-linked glycosylation pathway of proteins has been extensively characterized in mammals and plants, not much information is available regarding the N-glycosylation pathway in algae. We studied the α 1,3-glucosidase glucosidase II (GANAB) glycoenzyme in a red marine microalga Porphyridium sp. (Rhodophyta) using bioinformatic and biochemical approaches. The GANAB-gene was found to be highly conserved evolutionarily (compo-sed of all the common features of α and β subunits) and to exhibit similar motifs consistent with that of homolog eukaryotes GANAB genes. Phylogenetic analysis revealed its wide distribution across an evolutionarily vast range of organisms; while the α subunit is highly conserved and its phylogenic tree is similar to the taxon evolutionary tree, the β subunit is less conserved and its pattern somewhat differs from the taxon tree. In addition, the activity of the red microalgal GANAB enzyme was studied, including functional and biochemical characterization using a bioassay, indicating that the enzyme is similar to other eukaryotes ortholog GANAB enzymes. A correlation between polysaccharide production and GANAB activity, indicating its involvement in polysaccharide biosynthesis, is also demonstrated. This study represents a valuable contribution toward understanding the N-glycosylation and polysaccharide biosynthesis pathways in red microalgae.
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Affiliation(s)
- Oshrat Levy-Ontman
- Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
- Department of Chemical Engineering, Sami Shamoon College of Engineering, Beer-Sheva, 8410001, Israel
| | - Merav Fisher
- Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
| | - Yoram Shotland
- Department of Chemical Engineering, Sami Shamoon College of Engineering, Beer-Sheva, 8410001, Israel
| | - Yoram Tekoah
- Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
- Protalix Biotherapeutics, Carmiel, 2161401, Israel
| | - Shoshana Malis Arad
- Department of Biotechnology Engineering, Ben-Gurion University of the Negev, Beer-Sheva, 8410501, Israel
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12
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Warfield KL, Plummer E, Alonzi DS, Wolfe GW, Sampath A, Nguyen T, Butters TD, Enterlein SG, Stavale EJ, Shresta S, Ramstedt U. A Novel Iminosugar UV-12 with Activity against the Diverse Viruses Influenza and Dengue (Novel Iminosugar Antiviral for Influenza and Dengue). Viruses 2015; 7:2404-27. [PMID: 25984714 PMCID: PMC4452912 DOI: 10.3390/v7052404] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Accepted: 05/07/2015] [Indexed: 12/30/2022] Open
Abstract
Iminosugars are capable of targeting the life cycles of multiple viruses by blocking host endoplasmic reticulum α-glucosidase enzymes that are required for competent replication of a variety of enveloped, glycosylated viruses. Iminosugars as a class are approved for use in humans with diseases such as diabetes and Gaucher’s disease, providing evidence for safety of this class of compounds. The in vitro antiviral activity of iminosugars has been described in several publications with a subset of these demonstrating in vivo activity against flaviviruses, herpesviruses, retroviruses and filoviruses. Although there is compelling non-clinical in vivo evidence of antiviral efficacy, the efficacy of iminosugars as antivirals has yet to be demonstrated in humans. In the current study, we report a novel iminosugar, UV-12, which has efficacy against dengue and influenza in mouse models. UV-12 exhibits drug-like properties including oral bioavailability and good safety profile in mice and guinea pigs. UV-12 is an example of an iminosugar with activity against multiple virus families that should be investigated in further safety and efficacy studies and demonstrates potential value of this drug class as antiviral therapeutics.
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Affiliation(s)
| | - Emily Plummer
- La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.
| | | | | | | | - Tam Nguyen
- Tam Nguyen LLC, Gaithersburg, MD 20879, USA.
| | | | | | - Eric J Stavale
- Integrated Biotherapeutics, Gaithersburg, MD 20878, USA.
| | - Sujan Shresta
- La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.
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In vivo therapeutic protection against influenza A (H1N1) oseltamivir-sensitive and resistant viruses by the iminosugar UV-4. PLoS One 2015; 10:e0121662. [PMID: 25786028 PMCID: PMC4364785 DOI: 10.1371/journal.pone.0121662] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/02/2015] [Indexed: 01/26/2023] Open
Abstract
Our lead iminosugar analog called UV-4 or N-(9-methoxynonyl)-1-deoxynojirimycin inhibits activity of endoplasmic reticulum (ER) α-glucosidases I and II and is a potent, host-targeted antiviral candidate. The mechanism of action for the antiviral activity of iminosugars is proposed to be inhibition of ER α-glucosidases leading to misfolding of critical viral glycoproteins. These misfolded glycoproteins would then be incorporated into defective virus particles or targeted for degradation resulting in a reduction of infectious progeny virions. UV-4, and its hydrochloride salt known as UV-4B, is highly potent against dengue virus in vitro and promotes complete survival in a lethal dengue virus mouse model. In the current studies, UV-4 was shown to be highly efficacious via oral gavage against both oseltamivir-sensitive and -resistant influenza A (H1N1) infections in mice even if treatment was initiated as late as 48-72 hours after infection. The minimal effective dose was found to be 80-100 mg/kg when administered orally thrice daily. UV-4 treatment did not affect the development of protective antibody responses after either influenza infection or vaccination. Therefore, UV-4 is a promising candidate for further development as a therapeutic intervention against influenza.
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14
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Tannous A, Patel N, Tamura T, Hebert DN. Reglucosylation by UDP-glucose:glycoprotein glucosyltransferase 1 delays glycoprotein secretion but not degradation. Mol Biol Cell 2014; 26:390-405. [PMID: 25428988 PMCID: PMC4310732 DOI: 10.1091/mbc.e14-08-1254] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
UDP-glucose:glycoprotein glucosyltransferase 1 (UGT1) is a central quality control gatekeeper in the mammalian endoplasmic reticulum (ER). The reglucosylation of glycoproteins supports their rebinding to the carbohydrate-binding ER molecular chaperones calnexin and calreticulin. A cell-based reglucosylation assay was used to investigate the role of UGT1 in ER protein surveillance or the quality control process. UGT1 was found to modify wild-type proteins or proteins that are expected to eventually traffic out of the ER through the secretory pathway. Trapping of reglucosylated wild-type substrates in their monoglucosylated state delayed their secretion. Whereas terminally misfolded substrates or off-pathway proteins were most efficiently reglucosylated by UGT1, the trapping of these mutant substrates in their reglucosylated or monoglucosylated state did not delay their degradation by the ER-associated degradation pathway. This indicated that monoglucosylated mutant proteins were actively extracted from the calnexin/calreticulin binding-reglucosylation cycle for degradation. Therefore trapping proteins in their monoglucosylated state was sufficient to delay their exit to the Golgi but had no effect on their rate of degradation, suggesting that the degradation selection process progressed in a dominant manner that was independent of reglucosylation and the glucose-containing A-branch on the substrate glycans.
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Affiliation(s)
- Abla Tannous
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003 Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003
| | - Nishant Patel
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003
| | - Taku Tamura
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003
| | - Daniel N Hebert
- Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003 Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003
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15
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Inhibition of endoplasmic reticulum-resident glucosidases impairs severe acute respiratory syndrome coronavirus and human coronavirus NL63 spike protein-mediated entry by altering the glycan processing of angiotensin I-converting enzyme 2. Antimicrob Agents Chemother 2014; 59:206-16. [PMID: 25348530 DOI: 10.1128/aac.03999-14] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Endoplasmic reticulum (ER)-resident glucosidases I and II sequentially trim the three terminal glucose moieties on the N-linked glycans attached to nascent glycoproteins. These reactions are the first steps of N-linked glycan processing and are essential for proper folding and function of many glycoproteins. Because most of the viral envelope glycoproteins contain N-linked glycans, inhibition of ER glucosidases with derivatives of 1-deoxynojirimycin, i.e., iminosugars, efficiently disrupts the morphogenesis of a broad spectrum of enveloped viruses. However, like viral envelope proteins, the cellular receptors of many viruses are also glycoproteins. It is therefore possible that inhibition of ER glucosidases not only compromises virion production but also disrupts expression and function of viral receptors and thus inhibits virus entry into host cells. Indeed, we demonstrate here that iminosugar treatment altered the N-linked glycan structure of angiotensin I-converting enzyme 2 (ACE2), which did not affect its expression on the cell surface or its binding of the severe acute respiratory syndrome coronavirus (SARS-CoV) spike glycoprotein. However, alteration of N-linked glycans of ACE2 impaired its ability to support the transduction of SARS-CoV and human coronavirus NL63 (HCoV-NL63) spike glycoprotein-pseudotyped lentiviral particles by disruption of the viral envelope protein-triggered membrane fusion. Hence, in addition to reducing the production of infectious virions, inhibition of ER glucosidases also impairs the entry of selected viruses via a post-receptor-binding mechanism.
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16
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Hussain S, Miller JL, Harvey DJ, Gu Y, Rosenthal PB, Zitzmann N, McCauley JW. Strain-specific antiviral activity of iminosugars against human influenza A viruses. J Antimicrob Chemother 2014; 70:136-52. [PMID: 25223974 PMCID: PMC4267503 DOI: 10.1093/jac/dku349] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Objectives Drugs that target host cell processes can be employed to complement drugs that specifically target viruses, and iminosugar compounds that inhibit host α-glucosidases have been reported to show antiviral activity against multiple viruses. Here the effect and mechanism of two iminosugar α-glucosidase inhibitors, N-butyl-deoxynojirimycin (NB-DNJ) and N-nonyl-deoxynojirimycin (NN-DNJ), on human influenza A viruses was examined. Methods The viruses examined were a recently circulating seasonal influenza A(H3N2) virus strain A/Brisbane/10/2007, an older H3N2 strain A/Udorn/307/72, and A/Lviv/N6/2009, a strain representative of the currently circulating pandemic influenza A(H1N1)pdm09 virus. Results The inhibitors had the strongest effect on Brisbane/10 and NN-DNJ was more potent than NB-DNJ. Both compounds showed antiviral activity in cell culture against three human influenza A viruses in a strain-specific manner. Consistent with its action as an α-glucosidase inhibitor, NN-DNJ treatment resulted in an altered glycan processing of influenza haemagglutinin (HA) and neuraminidase (NA), confirmed by MS. NN-DNJ treatment was found to reduce the cell surface expression of the H3 subtype HA. The level of sialidase activity of NA was reduced in infected cells, but the addition of exogenous sialidase to the cells did not complement the NN-DNJ-mediated inhibition of virus replication. Using reassortant viruses, the drug susceptibility profile was determined to correlate with the origin of the HA. Conclusions NN-DNJ inhibits influenza A virus replication in a strain-specific manner that is dependent on the HA.
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Affiliation(s)
- S Hussain
- Division of Virology, Medical Research Council National Institute for Medical Research, Mill Hill, London NW7 1AA, UK Division of Physical Biochemistry, Medical Research Council National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - J L Miller
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - D J Harvey
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK Department of Biological Sciences, Gibbet Hill Campus, University of Warwick, Coventry CV4 7AL, UK
| | - Y Gu
- Confocal Imaging and Analysis Laboratory, Medical Research Council National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - P B Rosenthal
- Division of Physical Biochemistry, Medical Research Council National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - N Zitzmann
- Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
| | - J W McCauley
- Division of Virology, Medical Research Council National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
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Alonzi DS, Kukushkin NV, Allman SA, Hakki Z, Williams SJ, Pierce L, Dwek RA, Butters TD. Glycoprotein misfolding in the endoplasmic reticulum: identification of released oligosaccharides reveals a second ER-associated degradation pathway for Golgi-retrieved proteins. Cell Mol Life Sci 2013; 70:2799-814. [PMID: 23503623 PMCID: PMC11113499 DOI: 10.1007/s00018-013-1304-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2012] [Revised: 01/31/2013] [Accepted: 02/18/2013] [Indexed: 10/27/2022]
Abstract
Endoplasmic reticulum-associated degradation (ERAD) is a key cellular process whereby misfolded proteins are removed from the endoplasmic reticulum (ER) for subsequent degradation by the ubiquitin/proteasome system. In the present work, analysis of the released, free oligosaccharides (FOS) derived from all glycoproteins undergoing ERAD, has allowed a global estimation of the mechanisms of this pathway rather than following model proteins through degradative routes. Examining the FOS produced in endomannosidase-compromised cells following α-glucosidase inhibition has revealed a mechanism for clearing Golgi-retrieved glycoproteins that have failed to enter the ER quality control cycle. The Glc3Man7GlcNAc2 FOS species has been shown to be produced in the ER lumen by a mechanism involving a peptide: N-glycanase-like activity, and its production was sensitive to disruption of Golgi-ER trafficking. The detection of this oligosaccharide was unaffected by the overexpression of EDEM1 or cytosolic mannosidase, both of which increased the production of previously characterised cytosolically localised FOS. The lumenal FOS identified are therefore distinct in their production and regulation compared to FOS produced by the conventional route of misfolded glycoproteins directly removed from the ER. The production of such lumenal FOS is indicative of a novel degradative route for cellular glycoproteins that may exist under certain conditions.
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Affiliation(s)
- Dominic S. Alonzi
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Nikolay V. Kukushkin
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Sarah A. Allman
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Zalihe Hakki
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, VIC 3010 Australia
| | - Spencer J. Williams
- School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, 30 Flemington Road, Parkville, VIC 3010 Australia
| | - Lorna Pierce
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Raymond A. Dwek
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
| | - Terry D. Butters
- Department of Biochemistry, Oxford Glycobiology Institute, University of Oxford, South Parks Road, Oxford, OX1 3QU UK
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18
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Kukushkin NV, Easthope IS, Alonzi DS, Butters TD. Restricted processing of glycans by endomannosidase in mammalian cells. Glycobiology 2012; 22:1282-8. [DOI: 10.1093/glycob/cws088] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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19
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Demonstration that endoplasmic reticulum-associated degradation of glycoproteins can occur downstream of processing by endomannosidase. Biochem J 2011; 438:133-42. [DOI: 10.1042/bj20110186] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During quality control in the ER (endoplasmic reticulum), nascent glycoproteins are deglucosylated by ER glucosidases I and II. In the post-ER compartments, glycoprotein endo-α-mannosidase provides an alternative route for deglucosylation. Previous evidence suggests that endomannosidase non-selectively deglucosylates glycoproteins that escape quality control in the ER, facilitating secretion of aberrantly folded as well as normal glycoproteins. In the present study, we employed FOS (free oligosaccharides) released from degrading glycoproteins as biomarkers of ERAD (ER-associated degradation), allowing us to gain a global rather than single protein-centred view of ERAD. Glucosidase inhibition was used to discriminate between glucosidase- and endomannosidase-mediated ERAD pathways. Endomannosidase expression was manipulated in CHO (Chinese-hamster ovary)-K1 cells, naturally lacking a functional version of the enzyme, and HEK (human embryonic kidney)-293T cells. Endomannosidase was shown to decrease the levels of total FOS, suggesting decreased rates of ERAD. However, following pharmacological inhibition of ER glucosidases I and II, endomannosidase expression resulted in a partial switch between glucosylated FOS, released from ER-confined glycoproteins, to deglucosylated FOS, released from endomannosidase-processed glycoproteins transported from the Golgi/ERGIC (ER/Golgi intermediate compartment) to the ER. Using this approach, we have identified a previously unknown pathway of glycoprotein flow, undetectable by the commonly employed methods, in which secretory cargo is targeted back to the ER after being processed by endomannosidase.
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20
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Pearse BR, Tamura T, Sunryd JC, Grabowski GA, Kaufman RJ, Hebert DN. The role of UDP-Glc:glycoprotein glucosyltransferase 1 in the maturation of an obligate substrate prosaposin. ACTA ACUST UNITED AC 2010; 189:829-41. [PMID: 20498017 PMCID: PMC2878942 DOI: 10.1083/jcb.200912105] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A natural substrate for UGT1 is confirmed, revealing how the enzyme functions in the calnexin chaperone system as a quality control step in protein folding. An endoplasmic reticulum (ER) quality control system assists in efficient folding and disposal of misfolded proteins. N-linked glycans are critical in these events because their composition dictates interactions with molecular chaperones. UDP-glucose:glycoprotein glucosyltransferase 1 (UGT1) is a key quality control factor of the ER. It adds glucoses to N-linked glycans of nonglucosylated substrates that fail a quality control test, supporting additional rounds of chaperone binding and ER retention. How UGT1 functions in its native environment is poorly understood. The role of UGT1 in the maturation of glycoproteins at basal expression levels was analyzed. Prosaposin was identified as a prominent endogenous UGT1 substrate. A dramatic decrease in the secretion of prosaposin was observed in ugt1−/− cells with prosaposin localized to large juxtanuclear aggresome-like inclusions, which is indicative of its misfolding and the essential role that UGT1 plays in its proper maturation. A model is proposed that explains how UGT1 may aid in the folding of sequential domain–containing proteins such as prosaposin.
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Affiliation(s)
- Bradley R Pearse
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA
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21
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Whitby K, Pierson TC, Geiss B, Lane K, Engle M, Zhou Y, Doms RW, Diamond MS. Castanospermine, a potent inhibitor of dengue virus infection in vitro and in vivo. J Virol 2005; 79:8698-706. [PMID: 15994763 PMCID: PMC1168722 DOI: 10.1128/jvi.79.14.8698-8706.2005] [Citation(s) in RCA: 210] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Previous studies have suggested that alpha-glucosidase inhibitors such as castanospermine and deoxynojirimycin inhibit dengue virus type 1 infection by disrupting the folding of the structural proteins prM and E, a step crucial to viral secretion. We extend these studies by evaluating the inhibitory activity of castanospermine against a panel of clinically important flaviviruses including all four serotypes of dengue virus, yellow fever virus, and West Nile virus. Using in vitro assays we demonstrated that infections by all serotypes of dengue virus were inhibited by castanospermine. In contrast, yellow fever virus and West Nile virus were partially and almost completely resistant to the effects of the drug, respectively. Castanospermine inhibited dengue virus infection at the level of secretion and infectivity of viral particles. Importantly, castanospermine prevented mortality in a mouse model of dengue virus infection, with doses of 10, 50, and 250 mg/kg of body weight per day being highly effective at promoting survival (P < or = 0.0001). Correspondingly, castanospermine had no adverse or protective effect on West Nile virus mortality in an analogous mouse model. Overall, our data suggest that castanospermine has a strong antiviral effect on dengue virus infection and warrants further development as a possible treatment in humans.
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Affiliation(s)
- Kevin Whitby
- Department of Medicine, Washington University School of Medicine, 660 South Euclid Avenue, Box 8051, St. Louis, MO 63110, USA
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22
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Kitzmüller C, Caprini A, Moore SEH, Frénoy JP, Schwaiger E, Kellermann O, Ivessa NE, Ermonval M. Processing of N-linked glycans during endoplasmic-reticulum-associated degradation of a short-lived variant of ribophorin I. Biochem J 2003; 376:687-96. [PMID: 12952521 PMCID: PMC1223801 DOI: 10.1042/bj20030887] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Revised: 08/01/2003] [Accepted: 09/03/2003] [Indexed: 11/17/2022]
Abstract
Recently, the role of N-linked glycans in the process of ERAD (endoplasmic reticulum-associated degradation) of proteins has been widely recognized. In the present study, we attempted to delineate further the sequence of events leading from a fully glycosylated soluble protein to its deglycosylated form. Degradation intermediates of a truncated form of ribophorin I, namely RI(332), which contains a single N-linked oligosaccharide and is a substrate for the ERAD/ubiquitin-proteasome pathway, were characterized in HeLa cells under conditions blocking proteasomal degradation. The action of a deoxymannojirimycin- and kifunensine-sensitive alpha1,2-mannosidase was shown here to be required for both further glycan processing and progression of RI(332) in the ERAD pathway. In a first step, the Man(8) isomer B, generated by ER mannosidase I, appears to be the major oligomannoside structure associated with RI(332) intermediates. Some other trimmed N-glycan species, in particular Glc(1)Man(7)GlcNAc(2), were also found on the protein, indicating that several mannosidases might be implicated in the initial trimming of the oligomannoside. Secondly, another intermediate of degradation of RI(332) accumulated after proteasome inhibition. We demonstrated that this completely deglycosylated form arose from the action of an N-glycanase closely linked to the ER membrane. Indeed, the deglycosylated form of the protein remained membrane-associated, while being accessible from the cytoplasm to ubiquitinating enzymes and to added protease. Our results indicate that deglycosylation of a soluble ERAD substrate glycoprotein occurs in at least two distinct steps and is coupled with the retro-translocation of the protein preceding its proteasomal degradation.
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Affiliation(s)
- Claudia Kitzmüller
- Max F. Perutz Laboratories, University Departments at the Vienna Biocenter and Institute of Medical Biochemistry, Department of Molecular Genetics, University of Vienna, Austria
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23
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Andersson H, Garoff H. Lectin-mediated retention of p62 facilitates p62-E1 heterodimerization in endoplasmic reticulum of Semliki Forest virus-infected cells. J Virol 2003; 77:6676-82. [PMID: 12767987 PMCID: PMC156186 DOI: 10.1128/jvi.77.12.6676-6682.2003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Semliki Forest virus (SFV) spike subunits p62 and E1 are made from a common coding unit in the order p62-E1. The proteins are separated by the host signal peptidase upon translocation into the endoplasmic reticulum (ER). Shortly thereafter, p62 and E1 form heterodimers. Heterodimerization preferentially occurs between subunits derived from the same translation product, so-called cis heterodimerization. As the p62 protein has the capacity to leave the ER in the absence of E1, it has been postulated that there exists a retention mechanism for the p62 protein, putatively at or near the translocon, in the ER in order to promote cis heterodimerization (B. U. Barth and H. Garoff, J. Virol. 71:7857-7865, 1997). Here we show that there exists such a mechanism, that it is at least in part mediated by the ER chaperones calnexin and calreticulin, and that the retention is important for efficient cis heterodimerization.
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Affiliation(s)
- Helena Andersson
- Department of Biosciences at Novum, Karolinska Institute, S-141 57 Huddinge, Sweden.
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24
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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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25
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Völker C, De Praeter CM, Hardt B, Breuer W, Kalz-Füller B, Van Coster RN, Bause E. Processing of N-linked carbohydrate chains in a patient with glucosidase I deficiency (CDG type IIb). Glycobiology 2002; 12:473-83. [PMID: 12145188 DOI: 10.1093/glycob/cwf050] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recently, we reported a novel congenital disorder of glycosylation (CDG-IIb) caused by severe deficiency of the glucosidase I. The enzyme cleaves the alpha1,2-glucose residue from the asparagine-linked Glc(3)-Man(9)-GlcNAc(2) precursor, which is crucial for oligosaccharide maturation. The patient suffering from this disease was compound-heterozygous for two mutations in the glucosidase I gene, a T-->C transition in the paternal allele and a G-->C transition in the maternal allele. This gives rise in the glucosidase I polypeptide to the substitution of Arg486 by Thr and Phe652 by Leu, respectively. Kinetic studies using detergent extracts from cultured fibroblasts showed that the glucosidase I activity in the patient's cells was < 1% of the control level, with intermediate values in the parental cells. No significant differences in the activities of other processing enzymes, including oligosaccharyltransferase, glucosidase II, and Man(9)-mannosidase, were observed. By contrast, the patient's fibroblasts displayed a two- to threefold higher endo-alpha1,2-mannosidase activity, associated with an increased level of enzyme-specific mRNA-transcripts. This points to the lack of glucosidase I activity being compensated for, to some extent, by increase in the activity of the pathway involving endo-alpha1,2-mannosidase; this would also explain the marked urinary excretion of Glc(3)-Man. Comparative analysis of [(3)H]mannose-labeled N-glycoproteins showed that, despite the dramatically reduced glucosidase I activity, the bulk of the N-linked carbohydrate chains (>80%) in the patient's fibroblasts appeared to have been processed correctly, with only approximately 16% of the N-glycans being arrested at the Glc(3)-Man(9-7)-GlcNAc(2) stage. These structural and enzymatic data provide a reasonable basis for the observation that the sialotransferrin pattern, which frequently depends on the type of glycosylation disorder, appears to be normal in the patient. The human glucosidase I gene contains four exons separated by three introns with exon-4 encoding for the large 64-kDa catalytic domain of the enzyme. The two base mutations giving rise to substitution of Arg486 by Thr and Phe652 by Leu both reside in exon-4, consistent with their deleterious effect on enzyme activity. Incorporation of either mutation into wild-type glucosidase I resulted in the overexpression of enzyme mutants in COS 1 cells displaying no measurable catalytic activity. The Phe652Leu but not the Arg486Thr protein mutant showed a weak binding to a glucosidase I-specific affinity resin, indicating that the two amino acids affect polypeptide folding and active site formation differently.
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Affiliation(s)
- Christof Völker
- Institut für Physiologische Chemie, Universität Bonn, Bonn, Germany
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26
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Elagoz A, Benjannet S, Mammarbassi A, Wickham L, Seidah NG. Biosynthesis and cellular trafficking of the convertase SKI-1/S1P: ectodomain shedding requires SKI-1 activity. J Biol Chem 2002; 277:11265-75. [PMID: 11756446 DOI: 10.1074/jbc.m109011200] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Subtilisin kexin isozyme-1 (SKI-1)/site 1 protease is a mammalian subtilase composed of distinct functional domains. Among the major substrates of SKI-1 are the sterol regulatory element-binding proteins, regulating cholesterol and fatty acid homeostasis. Other substrates include the stress response factor activating transcription factor-6, the brain-derived neurotrophic factor, and the surface glycoproteins of highly infectious viruses belonging to the family of Arenaviridae. Domain deletion and/or point mutants were used to gauge the role of the various domains of SKI-1. Biosynthesis, cellular trafficking, and sterol regulatory element-binding protein-2 cleavage activity were used as diagnostic tools. Results revealed that Arg(130) and Arg(134) are critical for the autocatalytic primary processing of the prosegment and for the subsequent efficient exit of SKI-1 from the endoplasmic reticulum. Functional mapping of the growth factor cytokine receptor motif suggested a folding role within the endoplasmic reticulum. Microsequencing of the remaining membrane-bound stub following ectodomain shedding of SKI-1 localized the shedding site to KHQKLL(953) downward arrow. Site-directed mutagenesis, in vitro cleavage of a synthetic peptide containing the shedding site, and inhibitor studies favor an autocatalytic event occurring at a non-canonical SKI-1 recognition sequence, with P2 and P1 Leu being very critical. In conclusion, multiple domains ensuring optimal functional characteristics control SKI-1 activity and cellular trafficking.
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Affiliation(s)
- Aram Elagoz
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montréal, Montréal, Québec H2W 1R7, Canada
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27
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Lourenço A, Máximo P, Ferreira L, Pereira M. Indolizidine and quinolizidine alkaloids structure and bioactivity. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1572-5995(02)80038-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2023]
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28
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Ermonval M, Kitzmüller C, Mir AM, Cacan R, Ivessa NE. N-glycan structure of a short-lived variant of ribophorin I expressed in the MadIA214 glycosylation-defective cell line reveals the role of a mannosidase that is not ER mannosidase I in the process of glycoprotein degradation. Glycobiology 2001; 11:565-76. [PMID: 11447136 DOI: 10.1093/glycob/11.7.565] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A soluble form of ribophorin I (RI(332)) is rapidly degraded in Hela and Chinese hamster ovary (CHO) cells by a cytosolic proteasomal pathway, and the N-linked glycan present on the protein may play an important role in this process. Specifically, it has been suggested that endoplasmic reticulum (ER) mannosidase I could trigger the targeting of improperly folded glycoproteins to degradation. We used a CHO-derived glycosylation-defective cell line, MadIA214, for investigating the role of mannosidase(s) as a signal for glycoprotein degradation. Glycoproteins in MadIA214 cells carry truncated Glc(1)Man(5)GlcNAc(2) N-glycans. This oligomannoside structure interferes with protein maturation and folding, leading to an alteration of the ER morphology and the detection of high levels of soluble oligomannoside species caused by glycoprotein degradation. An HA-epitope-tagged soluble variant of ribophorin I (RI(332)-3HA) expressed in MadIA214 cells was rapidly degraded, comparable to control cells with the complete Glc(3)Man(9)GlcNAc(2) N-glycan. ER-associated degradation (ERAD) of RI(332)-3HA was also proteasome-mediated in MadIA214 cells, as demonstrated by inhibition of RI(332)-3HA degradation with agents specifically blocking proteasomal activities. Two inhibitors of alpha1,2-mannosidase activity also stabilized RI(332)-3HA in the glycosylation-defective cell line. This is striking, because the major mannosidase activity in the ER is the one of mannosidase I, specific for a mannose alpha1,2-linkage that is absent from the truncated Man(5) structure. Interestingly, though the Man(5) derivative was present in large amounts in the total protein pool, the two major species linked to RI(332)-3HA shortly after synthesis consisted of Glc(1)Man(5 )and Man(4), being replaced by Man(4 )and Man(3) when proteasomal degradation was inhibited. In contrast, the untrimmed intermediate of RI(332)-3HA was detected in mutant cells treated with mannosidase inhibitors. Our results unambiguously demonstrate that an alpha1,2-mannosidase that is not ER mannosidase I is involved in ERAD of RI(332-)3HA in the glycosylation-defective cell line, MadIA214.
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Affiliation(s)
- M Ermonval
- URA CNRS 1960, Département d'Immunologie Institut Pasteur, 25 rue du Docteur Roux, 75724 Paris Cedex 15, France
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29
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Branza-Nichita N, Petrescu AJ, Negroiu G, Dwek RA, Petrescu SM. N-glycosylation processing and glycoprotein folding-lessons from the tyrosinase-related proteins. Chem Rev 2000; 100:4697-712. [PMID: 11749363 DOI: 10.1021/cr990291y] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- N Branza-Nichita
- Institute of Biochemistry, Romanian Academy, Splaiul Independentei 296, 77700 Bucharest 17, Romania, and Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, South Parks Road OX1 3QU, Oxford, U.K
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30
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Zuber C, Spiro MJ, Guhl B, Spiro RG, Roth J. Golgi apparatus immunolocalization of endomannosidase suggests post-endoplasmic reticulum glucose trimming: implications for quality control. Mol Biol Cell 2000; 11:4227-40. [PMID: 11102520 PMCID: PMC15069 DOI: 10.1091/mbc.11.12.4227] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Trimming of N-linked oligosaccharides by endoplasmic reticulum (ER) glucosidase II is implicated in quality control of protein folding. An alternate glucosidase II-independent deglucosylation pathway exists, in which endo-alpha-mannosidase cleaves internally the glucose-substituted mannose residue of oligosaccharides. By immunogold labeling, we detected most endomannosidase in cis/medial Golgi cisternae (83.8% of immunogold labeling) and less in the intermediate compartment (15.1%), but none in the trans-Golgi apparatus and ER, including its transitional elements. This dual localization became more pronounced under 15 degrees C conditions indicative of two endomannosidase locations. Under experimental conditions when the intermediate compartment marker p58 was retained in peripheral sites, endomannosidase was redistributed to the Golgi apparatus. Double immunogold labeling established a mutually exclusive distribution of endomannosidase and glucosidase II, whereas calreticulin was observed in endomannosidase-reactive sites (17.3% in intermediate compartment, 5.7% in Golgi apparatus) in addition to the ER (77%). Our results demonstrate that glucose trimming of N-linked oligosaccharides is not limited to the ER and that protein deglucosylation by endomannosidase in the Golgi apparatus and intermediate compartment additionally ensures that processing to mature oligosaccharides can continue. Thus, endomannosidase localization suggests that a quality control of N-glycosylation exists in the Golgi apparatus.
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Affiliation(s)
- C Zuber
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zürich, CH-8091 Zürich, Switzerland
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31
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Spiro RG. Glucose residues as key determinants in the biosynthesis and quality control of glycoproteins with N-linked oligosaccharides. J Biol Chem 2000; 275:35657-60. [PMID: 11007802 DOI: 10.1074/jbc.r000022200] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- R G Spiro
- Departments of Biological Chemistry and Medicine, Harvard Medical School and Joslin Diabetes Center, Boston, Massachusetts 02215, USA.
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Marcus NY, Perlmutter DH. Glucosidase and mannosidase inhibitors mediate increased secretion of mutant alpha1 antitrypsin Z. J Biol Chem 2000; 275:1987-92. [PMID: 10636901 DOI: 10.1074/jbc.275.3.1987] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It is now well known that the addition and trimming of oligosaccharide side chains during post-translational modification play an important role in determining the fate of secretory, membrane, and lysosomal glycoproteins. Recent studies have suggested that trimming of oligosaccharide side chains also plays a role in the degradation of misfolded glycoproteins as a part of the quality control mechanism of the endoplasmic reticulum (ER). In this study, we examined the effect of several inhibitors of carbohydrate processing on the fate of the misfolded secretory protein alpha1 antitrypsin Z. Retention of this misfolded glycoprotein in the ER of liver cells in the classical form of alpha1 antitrypsin (alpha1-AT) deficiency is associated with severe liver injury and hepatocellular carcinoma and lack of its secretion is associated with destructive lung disease/emphysema. The results show marked alterations in the fate of alpha1 antitrypsin Z (alpha1-ATZ). Indeed, one glucosidase inhibitor, castanospermine (CST), and two mannosidase inhibitors, kifunensine (KIF) and deoxymannojirimycin (DMJ), mediate marked increases in secretion of alpha1-ATZ by distinct mechanisms. The effects of these inhibitors on secretion have interesting implications for our understanding of the quality control apparatus of the ER. These inhibitors may also constitute models for development of additional drugs for chemoprophylaxis of liver injury and emphysema in patients with alpha1-AT deficiency.
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Affiliation(s)
- N Y Marcus
- Departments of Pediatrics, Cell Biology and Physiology, Washington University School of Medicine, Division of Gastroenterology and Nutrition, Children's Hospital, St. Louis, Missouri 63110, USA
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