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Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. J Biol Chem 2024; 300:107584. [PMID: 39025454 PMCID: PMC11365447 DOI: 10.1016/j.jbc.2024.107584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 07/20/2024] Open
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multistep pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 congenital disorders of glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multispanning membrane protein located in the ER, with its N and C termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
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Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Ken-Taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Grace I Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA
| | - George N Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, Brussels, Belgium
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, New York, USA.
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Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.03.587922. [PMID: 38617304 PMCID: PMC11014557 DOI: 10.1101/2024.04.03.587922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multi-step pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 Congenital Disorders of Glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multi-spanning membrane protein located in the ER, with its N and C-termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
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Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ken-taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Grace I. Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - George N. Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, 1050 Brussels, Belgium
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
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3
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Chen S, Pei CX, Xu S, Li H, Liu YS, Wang Y, Jin C, Dean N, Gao XD. Rft1 catalyzes lipid-linked oligosaccharide translocation across the ER membrane. Nat Commun 2024; 15:5157. [PMID: 38886340 PMCID: PMC11182771 DOI: 10.1038/s41467-024-48999-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Accepted: 05/20/2024] [Indexed: 06/20/2024] Open
Abstract
The eukaryotic asparagine (N)-linked glycan is pre-assembled as a fourteen-sugar oligosaccharide on a lipid carrier in the endoplasmic reticulum (ER). Seven sugars are first added to dolichol pyrophosphate (PP-Dol) on the cytoplasmic face of the ER, generating Man5GlcNAc2-PP-Dol (M5GN2-PP-Dol). M5GN2-PP-Dol is then flipped across the bilayer into the lumen by an ER translocator. Genetic studies identified Rft1 as the M5GN2-PP-Dol flippase in vivo but are at odds with biochemical data suggesting Rft1 is dispensable for flipping in vitro. Thus, the question of whether Rft1 plays a direct or an indirect role during M5GN2-PP-Dol translocation has been controversial for over two decades. We describe a completely reconstituted in vitro assay for M5GN2-PP-Dol translocation and demonstrate that purified Rft1 catalyzes the translocation of M5GN2-PP-Dol across the lipid bilayer. These data, combined with in vitro results demonstrating substrate selectivity and rft1∆ phenotypes, confirm the molecular identity of Rft1 as the M5GN2-PP-Dol ER flippase.
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Affiliation(s)
- Shuai Chen
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
- State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing, China
| | - Cai-Xia Pei
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Si Xu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Hanjie Li
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Yi-Shi Liu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China
| | - Yicheng Wang
- State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China
- Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing, China
| | - Cheng Jin
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
| | - Neta Dean
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, USA.
| | - Xiao-Dong Gao
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, China.
- State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
- Key Laboratory of Biopharmaceutical Preparation and Delivery, Chinese Academy of Sciences, Beijing, China.
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4
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Ramírez AS, Locher KP. Structural and mechanistic studies of the N-glycosylation machinery: from lipid-linked oligosaccharide biosynthesis to glycan transfer. Glycobiology 2023; 33:861-872. [PMID: 37399117 PMCID: PMC10859629 DOI: 10.1093/glycob/cwad053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 06/26/2023] [Accepted: 06/27/2023] [Indexed: 07/05/2023] Open
Abstract
N-linked protein glycosylation is a post-translational modification that exists in all domains of life. It involves two consecutive steps: (i) biosynthesis of a lipid-linked oligosaccharide (LLO), and (ii) glycan transfer from the LLO to asparagine residues in secretory proteins, which is catalyzed by the integral membrane enzyme oligosaccharyltransferase (OST). In the last decade, structural and functional studies of the N-glycosylation machinery have increased our mechanistic understanding of the pathway. The structures of bacterial and eukaryotic glycosyltransferases involved in LLO elongation provided an insight into the mechanism of LLO biosynthesis, whereas structures of OST enzymes revealed the molecular basis of sequon recognition and catalysis. In this review, we will discuss approaches used and insight obtained from these studies with a special emphasis on the design and preparation of substrate analogs.
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Affiliation(s)
- Ana S Ramírez
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich 8093, Switzerland
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, Eidgenössische Technische Hochschule (ETH), Zürich 8093, Switzerland
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5
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Piirainen MA, Frey AD. The Impact of Glycoengineering on the Endoplasmic Reticulum Quality Control System in Yeasts. Front Mol Biosci 2022; 9:910709. [PMID: 35720120 PMCID: PMC9201249 DOI: 10.3389/fmolb.2022.910709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 05/02/2022] [Indexed: 11/13/2022] Open
Abstract
Yeasts are widely used and established production hosts for biopharmaceuticals. Despite of tremendous advances on creating human-type N-glycosylation, N-glycosylated biopharmaceuticals manufactured with yeasts are missing on the market. The N-linked glycans fulfill several purposes. They are essential for the properties of the final protein product for example modulating half-lives or interactions with cellular components. Still, while the protein is being formed in the endoplasmic reticulum, specific glycan intermediates play crucial roles in the folding of or disposal of proteins which failed to fold. Despite of this intricate interplay between glycan intermediates and the cellular machinery, many of the glycoengineering approaches are based on modifications of the N-glycan processing steps in the endoplasmic reticulum (ER). These N-glycans deviate from the canonical structures required for interactions with the lectins of the ER quality control system. In this review we provide a concise overview on the N-glycan biosynthesis, glycan-dependent protein folding and quality control systems and the wide array glycoengineering approaches. Furthermore, we discuss how the current glycoengineering approaches partially or fully by-pass glycan-dependent protein folding mechanisms or create structures that mimic the glycan epitope required for ER associated protein degradation.
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Affiliation(s)
- Mari A. Piirainen
- Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland
| | - Alexander D. Frey
- Department of Bioproducts and Biosystems, Aalto University, Espoo, Finland
- Kemistintie 1, Aalto University, Otakaari, Finland
- *Correspondence: Alexander D. Frey,
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6
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Verchère A, Cowton A, Jenni A, Rauch M, Häner R, Graumann J, Bütikofer P, Menon AK. Complexity of the eukaryotic dolichol-linked oligosaccharide scramblase suggested by activity correlation profiling mass spectrometry. Sci Rep 2021; 11:1411. [PMID: 33446867 PMCID: PMC7809446 DOI: 10.1038/s41598-020-80956-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 12/31/2020] [Indexed: 01/22/2023] Open
Abstract
The oligosaccharide required for asparagine (N)-linked glycosylation of proteins in the endoplasmic reticulum (ER) is donated by the glycolipid Glc3Man9GlcNAc2-PP-dolichol. Remarkably, whereas glycosylation occurs in the ER lumen, the initial steps of Glc3Man9GlcNAc2-PP-dolichol synthesis generate the lipid intermediate Man5GlcNAc2-PP-dolichol (M5-DLO) on the cytoplasmic side of the ER. Glycolipid assembly is completed only after M5-DLO is translocated to the luminal side. The membrane protein (M5-DLO scramblase) that mediates M5-DLO translocation across the ER membrane has not been identified, despite its importance for N-glycosylation. Building on our ability to recapitulate scramblase activity in proteoliposomes reconstituted with a crude mixture of ER membrane proteins, we developed a mass spectrometry-based 'activity correlation profiling' approach to identify scramblase candidates in the yeast Saccharomyces cerevisiae. Data curation prioritized six polytopic ER membrane proteins as scramblase candidates, but reconstitution-based assays and gene disruption in the protist Trypanosoma brucei revealed, unexpectedly, that none of these proteins is necessary for M5-DLO scramblase activity. Our results instead strongly suggest that M5-DLO scramblase activity is due to a protein, or protein complex, whose activity is regulated at the level of quaternary structure.
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Affiliation(s)
- Alice Verchère
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Ave, New York, NY, 10065, USA
| | - Andrew Cowton
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstr. 28, 3012, Bern, Switzerland
| | - Aurelio Jenni
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstr. 28, 3012, Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Mittelstr. 43, 3012, Bern, Switzerland
| | - Monika Rauch
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstr. 28, 3012, Bern, Switzerland
| | - Robert Häner
- Department of Chemistry and Biochemistry, University of Bern, Freiestr. 3, 3012, Bern, Switzerland
| | - Johannes Graumann
- Max Planck Institute for Heart and Lung Research, W.G. Kerckhoff Institute, Ludwigstr. 43, 61231, Bad Nauheim, Germany.,German Centre for Cardiovascular Research (DZHK), Rhine-Main site, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Peter Bütikofer
- Institute of Biochemistry and Molecular Medicine, University of Bern, Bühlstr. 28, 3012, Bern, Switzerland.
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Ave, New York, NY, 10065, USA.
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7
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Abstract
N-glycosylation is a highly conserved glycan modification, and more than 7000 proteins are N-glycosylated in humans. N-glycosylation has many biological functions such as protein folding, trafficking, and signal transduction. Thus, glycan modification to proteins is profoundly involved in numerous physiological and pathological processes. The N-glycan precursor is biosynthesized in the endoplasmic reticulum (ER) from dolichol phosphate by sequential enzymatic reactions to generate the dolichol-linked oligosaccharide composed of 14 sugar residues, Glc3Man9GlcNAc2. The oligosaccharide is then en bloc transferred to the consensus sequence N-X-S/T (X represents any amino acid except proline) of nascent proteins. Subsequently, the N-glycosylated nascent proteins enter the folding step, in which N-glycans contribute largely to attaining the correct protein fold by recruiting the lectin-like chaperones, calnexin, and calreticulin. Despite the N-glycan-dependent folding process, some glycoproteins do not fold correctly, and these misfolded glycoproteins are destined to degradation by proteasomes in the cytosol. Properly folded proteins are transported to the Golgi, and N-glycans undergo maturation by the sequential reactions of glycosidases and glycosyltransferases, generating complex-type N-glycans. N-Acetylglucosaminyltransferases (GnT-III, GnT-IV, and GnT-V) produce branched N-glycan structures, affording a higher complexity to N-glycans. In this chapter, we provide an overview of the biosynthetic pathway of N-glycans in the ER and Golgi.
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8
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Kuk ACY, Hao A, Guan Z, Lee SY. Visualizing conformation transitions of the Lipid II flippase MurJ. Nat Commun 2019; 10:1736. [PMID: 30988294 PMCID: PMC6465408 DOI: 10.1038/s41467-019-09658-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Accepted: 03/22/2019] [Indexed: 02/06/2023] Open
Abstract
The biosynthesis of many polysaccharides, including bacterial peptidoglycan and eukaryotic N-linked glycans, requires transport of lipid-linked oligosaccharide (LLO) precursors across the membrane by specialized flippases. MurJ is the flippase for the lipid-linked peptidoglycan precursor Lipid II, a key player in bacterial cell wall synthesis, and a target of recently discovered antibacterials. However, the flipping mechanism of LLOs including Lipid II remains poorly understood due to a dearth of structural information. Here we report crystal structures of MurJ captured in inward-closed, inward-open, inward-occluded and outward-facing conformations. Together with mutagenesis studies, we elucidate the conformational transitions in MurJ that mediate lipid flipping, identify the key ion for function, and provide a framework for the development of inhibitors. MurJ is the flippase for the lipid-linked peptidoglycan precursor Lipid II, a key player in bacterial cell wall synthesis, but the flipping mechanism remains poorly understood. Here authors report crystal structures of MurJ in different conformations which shed light on the MurJ transitions that mediate lipid flipping.
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Affiliation(s)
- Alvin C Y Kuk
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, NC, 27710, USA
| | - Aili Hao
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, NC, 27710, USA
| | - Ziqiang Guan
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, NC, 27710, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University Medical Center, 303 Research Drive, Durham, NC, 27710, USA.
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9
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Nadeem T, Khan MA, Ijaz B, Ahmed N, Rahman ZU, Latif MS, Ali Q, Rana MA. Glycosylation of Recombinant Anticancer Therapeutics in Different Expression Systems with Emerging Technologies. Cancer Res 2018; 78:2787-2798. [DOI: 10.1158/0008-5472.can-18-0032] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 03/22/2018] [Accepted: 04/03/2018] [Indexed: 11/16/2022]
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10
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Mathieu-Rivet E, Lerouge P, Bardor M. Chlamydomonas reinhardtii: Protein Glycosylation and Production of Biopharmaceuticals. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/978-3-319-66360-9_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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11
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Gottier P, Gonzalez-Salgado A, Menon AK, Liu YC, Acosta-Serrano A, Bütikofer P. RFT1 Protein Affects Glycosylphosphatidylinositol (GPI) Anchor Glycosylation. J Biol Chem 2016; 292:1103-1111. [PMID: 27927990 DOI: 10.1074/jbc.m116.758367] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 11/17/2016] [Indexed: 12/16/2022] Open
Abstract
The membrane protein RFT1 is essential for normal protein N-glycosylation, but its precise function is not known. RFT1 was originally proposed to translocate the glycolipid Man5GlcNAc2-PP-dolichol (needed to synthesize N-glycan precursors) across the endoplasmic reticulum membrane, but subsequent studies showed that it does not play a direct role in transport. In contrast to the situation in yeast, RFT1 is not essential for growth of the parasitic protozoan Trypanosoma brucei, enabling the study of its function in a null background. We now report that lack of T. brucei RFT1 (TbRFT1) not only affects protein N-glycosylation but also glycosylphosphatidylinositol (GPI) anchor side-chain modification. Analysis by immunoblotting, metabolic labeling, and mass spectrometry demonstrated that the major GPI-anchored proteins of T. brucei procyclic forms have truncated GPI anchor side chains in TbRFT1 null parasites when compared with wild-type cells, a defect that is corrected by expressing a tagged copy of TbRFT1 in the null background. In vivo and in vitro labeling experiments using radiolabeled GPI precursors showed that GPI underglycosylation was not the result of decreased formation of the GPI precursor lipid or defective galactosylation of GPI intermediates in the endoplasmic reticulum, but rather due to modifications that are expected to occur in the Golgi apparatus. Unexpectedly, immunofluorescence microscopy localized TbRFT1 to both the endoplasmic reticulum and the Golgi, consistent with the proposal that TbRFT1 plays a direct or indirect role in GPI anchor glycosylation in the Golgi apparatus. Our results implicate RFT1 in a wider range of glycosylation processes than previously appreciated.
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Affiliation(s)
- Petra Gottier
- From the Institute of Biochemistry and Molecular Medicine and.,Graduate School of Cellular and Biochemical Sciences, University of Bern, 3012 Bern, Switzerland
| | | | - Anant K Menon
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065, and
| | | | - Alvaro Acosta-Serrano
- the Departments of Parasitology and.,Vector Biology, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | - Peter Bütikofer
- From the Institute of Biochemistry and Molecular Medicine and
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12
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Pomorski TG, Menon AK. Lipid somersaults: Uncovering the mechanisms of protein-mediated lipid flipping. Prog Lipid Res 2016; 64:69-84. [PMID: 27528189 DOI: 10.1016/j.plipres.2016.08.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 08/10/2016] [Indexed: 12/22/2022]
Abstract
Membrane lipids diffuse rapidly in the plane of the membrane but their ability to flip spontaneously across a membrane bilayer is hampered by a significant energy barrier. Thus spontaneous flip-flop of polar lipids across membranes is very slow, even though it must occur rapidly to support diverse aspects of cellular life. Here we discuss the mechanisms by which rapid flip-flop occurs, and what role lipid flipping plays in membrane homeostasis and cell growth. We focus on conceptual aspects, highlighting mechanistic insights from biochemical and in silico experiments, and the recent, ground-breaking identification of a number of lipid scramblases.
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Affiliation(s)
- Thomas Günther Pomorski
- Faculty of Chemistry and Biochemistry, Molecular Biochemistry, Ruhr University Bochum, Universitätstrasse 150, D-44780 Bochum, Germany; Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Department of Plant and Environmental Sciences, University of Copenhagen, Frederiksberg C, Denmark.
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, NY 10065, USA.
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13
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Lombard J. The multiple evolutionary origins of the eukaryotic N-glycosylation pathway. Biol Direct 2016; 11:36. [PMID: 27492357 PMCID: PMC4973528 DOI: 10.1186/s13062-016-0137-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 07/26/2016] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND The N-glycosylation is an essential protein modification taking place in the membranes of the endoplasmic reticulum (ER) in eukaryotes and the plasma membranes in archaea. It shares mechanistic similarities based on the use of polyisoprenol lipid carriers with other glycosylation pathways involved in the synthesis of bacterial cell wall components (e.g. peptidoglycan and teichoic acids). Here, a phylogenomic analysis was carried out to examine the validity of rival hypotheses suggesting alternative archaeal or bacterial origins to the eukaryotic N-glycosylation pathway. RESULTS The comparison of several polyisoprenol-based glycosylation pathways from the three domains of life shows that most of the implicated proteins belong to a limited number of superfamilies. The N-glycosylation pathway enzymes are ancestral to the eukaryotes, but their origins are mixed: Alg7, Dpm and maybe also one gene of the glycosyltransferase 1 (GT1) superfamily and Stt3 have proteoarchaeal (TACK superphylum) origins; alg2/alg11 may have resulted from the duplication of the original GT1 gene; the lumen glycosyltransferases were probably co-opted and multiplied through several gene duplications during eukaryogenesis; Alg13/Alg14 are more similar to their bacterial homologues; and Alg1, Alg5 and a putative flippase have unknown origins. CONCLUSIONS The origin of the eukaryotic N-glycosylation pathway is not unique and less straightforward than previously thought: some basic components likely have proteoarchaeal origins, but the pathway was extensively developed before the eukaryotic diversification through multiple gene duplications, protein co-options, neofunctionalizations and even possible horizontal gene transfers from bacteria. These results may have important implications for our understanding of the ER evolution and eukaryogenesis. REVIEWERS This article was reviewed by Pr. Patrick Forterre and Dr. Sergei Mekhedov (nominated by Editorial Board member Michael Galperin).
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Affiliation(s)
- Jonathan Lombard
- National Evolutionary Synthesis Center, 2024 W. Main Street Suite A200, Durham, NC, 27705, USA.
- Biosciences, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter, EX4 4QD, UK.
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14
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Structural basis for phospholipid scrambling in the TMEM16 family. Curr Opin Struct Biol 2016; 39:61-70. [PMID: 27295354 DOI: 10.1016/j.sbi.2016.05.020] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Revised: 04/28/2016] [Accepted: 05/30/2016] [Indexed: 11/21/2022]
Abstract
Upon activation, lipid scramblases dissipate the lipid asymmetry of membranes, in an ATP-independent manner, by catalyzing flip-flop of lipids between the leaflets. The molecular identities of these proteins long remained obscure, but in recent years the TMEM16 family of proteins has been found to constitute Ca2+-activated scramblases. Recently, the X-ray structure of a fungal TMEM16 homologue has provided insight into the architecture of this protein family and into potential scrambling mechanisms. The protein forms homodimers with each subunit containing a membrane-spanning hydrophilic cleft. This region is of sufficient size to harbor polar headgroups on their way across the membrane and thus may lower the energetic barrier for the diffusion of lipids between the two leaflets of the bilayer. A regulatory Ca2+ binding site located within the membrane adjacent to this hydrophobic cleft is responsible for activation by yet unknown mechanisms.
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15
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Schmoll M, Dattenböck C, Carreras-Villaseñor N, Mendoza-Mendoza A, Tisch D, Alemán MI, Baker SE, Brown C, Cervantes-Badillo MG, Cetz-Chel J, Cristobal-Mondragon GR, Delaye L, Esquivel-Naranjo EU, Frischmann A, Gallardo-Negrete JDJ, García-Esquivel M, Gomez-Rodriguez EY, Greenwood DR, Hernández-Oñate M, Kruszewska JS, Lawry R, Mora-Montes HM, Muñoz-Centeno T, Nieto-Jacobo MF, Nogueira Lopez G, Olmedo-Monfil V, Osorio-Concepcion M, Piłsyk S, Pomraning KR, Rodriguez-Iglesias A, Rosales-Saavedra MT, Sánchez-Arreguín JA, Seidl-Seiboth V, Stewart A, Uresti-Rivera EE, Wang CL, Wang TF, Zeilinger S, Casas-Flores S, Herrera-Estrella A. The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species. Microbiol Mol Biol Rev 2016; 80:205-327. [PMID: 26864432 PMCID: PMC4771370 DOI: 10.1128/mmbr.00040-15] [Citation(s) in RCA: 121] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The genus Trichoderma contains fungi with high relevance for humans, with applications in enzyme production for plant cell wall degradation and use in biocontrol. Here, we provide a broad, comprehensive overview of the genomic content of these species for "hot topic" research aspects, including CAZymes, transport, transcription factors, and development, along with a detailed analysis and annotation of less-studied topics, such as signal transduction, genome integrity, chromatin, photobiology, or lipid, sulfur, and nitrogen metabolism in T. reesei, T. atroviride, and T. virens, and we open up new perspectives to those topics discussed previously. In total, we covered more than 2,000 of the predicted 9,000 to 11,000 genes of each Trichoderma species discussed, which is >20% of the respective gene content. Additionally, we considered available transcriptome data for the annotated genes. Highlights of our analyses include overall carbohydrate cleavage preferences due to the different genomic contents and regulation of the respective genes. We found light regulation of many sulfur metabolic genes. Additionally, a new Golgi 1,2-mannosidase likely involved in N-linked glycosylation was detected, as were indications for the ability of Trichoderma spp. to generate hybrid galactose-containing N-linked glycans. The genomic inventory of effector proteins revealed numerous compounds unique to Trichoderma, and these warrant further investigation. We found interesting expansions in the Trichoderma genus in several signaling pathways, such as G-protein-coupled receptors, RAS GTPases, and casein kinases. A particularly interesting feature absolutely unique to T. atroviride is the duplication of the alternative sulfur amino acid synthesis pathway.
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Affiliation(s)
- Monika Schmoll
- Austrian Institute of Technology, Department Health and Environment, Bioresources Unit, Tulln, Austria
| | - Christoph Dattenböck
- Austrian Institute of Technology, Department Health and Environment, Bioresources Unit, Tulln, Austria
| | | | | | - Doris Tisch
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria
| | - Mario Ivan Alemán
- Cinvestav, Department of Genetic Engineering, Irapuato, Guanajuato, Mexico
| | - Scott E Baker
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Christopher Brown
- University of Otago, Department of Biochemistry and Genetics, Dunedin, New Zealand
| | | | - José Cetz-Chel
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
| | | | - Luis Delaye
- Cinvestav, Department of Genetic Engineering, Irapuato, Guanajuato, Mexico
| | | | - Alexa Frischmann
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria
| | | | - Monica García-Esquivel
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
| | | | - David R Greenwood
- The University of Auckland, School of Biological Sciences, Auckland, New Zealand
| | - Miguel Hernández-Oñate
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
| | - Joanna S Kruszewska
- Polish Academy of Sciences, Institute of Biochemistry and Biophysics, Laboratory of Fungal Glycobiology, Warsaw, Poland
| | - Robert Lawry
- Lincoln University, Bio-Protection Research Centre, Lincoln, Canterbury, New Zealand
| | | | | | | | | | | | | | - Sebastian Piłsyk
- Polish Academy of Sciences, Institute of Biochemistry and Biophysics, Laboratory of Fungal Glycobiology, Warsaw, Poland
| | - Kyle R Pomraning
- Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Aroa Rodriguez-Iglesias
- Austrian Institute of Technology, Department Health and Environment, Bioresources Unit, Tulln, Austria
| | | | | | - Verena Seidl-Seiboth
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria
| | | | | | - Chih-Li Wang
- National Chung-Hsing University, Department of Plant Pathology, Taichung, Taiwan
| | - Ting-Fang Wang
- Academia Sinica, Institute of Molecular Biology, Taipei, Taiwan
| | - Susanne Zeilinger
- Research Division Biotechnology and Microbiology, Institute of Chemical Engineering, TU Wien, Vienna, Austria University of Innsbruck, Institute of Microbiology, Innsbruck, Austria
| | | | - Alfredo Herrera-Estrella
- LANGEBIO, National Laboratory of Genomics for Biodiversity, Cinvestav-Irapuato, Guanajuato, Mexico
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16
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Rush JS. Role of Flippases in Protein Glycosylation in the Endoplasmic Reticulum. Lipid Insights 2016; 8:45-53. [PMID: 26917968 PMCID: PMC4762491 DOI: 10.4137/lpi.s31784] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 01/12/2016] [Accepted: 01/15/2016] [Indexed: 12/21/2022] Open
Abstract
Glycosylation is essential to the synthesis, folding, and function of glycoproteins in eukaryotes. Proteins are co- and posttranslationally modified by a variety of glycans in the endoplasmic reticulum (ER); modifications include C- and O-mannosylation, N-glycosylation, and the addition of glycosylphosphatidylinositol membrane anchors. Protein glycosylation in the ER of eukaryotes involves enzymatic steps on both the cytosolic and lumenal surfaces of the ER membrane. The glycans are first assembled as precursor glycolipids, on the cytosolic surface of the ER, which are tethered to the membrane by attachment to a long-chain polyisoprenyl phosphate (dolichol) containing a reduced α-isoprene. The lipid-anchored building blocks then migrate transversely (flip) across the ER membrane to the lumenal surface, where final assembly of the glycan is completed. This strategy allows the cell to export high-energy biosynthetic intermediates as lipid-bound glycans, while constraining the glycosyl donors to the site of assembly on the membrane surface. This review focuses on the flippases that participate in protein glycosylation in the ER.
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Affiliation(s)
- Jeffrey S Rush
- Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY, USA
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17
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Ruiz N. Lipid Flippases for Bacterial Peptidoglycan Biosynthesis. Lipid Insights 2016; 8:21-31. [PMID: 26792999 PMCID: PMC4714577 DOI: 10.4137/lpi.s31783] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 11/10/2015] [Accepted: 11/30/2015] [Indexed: 12/26/2022] Open
Abstract
The biosynthesis of cellular polysaccharides and glycoconjugates often involves lipid-linked intermediates that need to be translocated across membranes. Essential pathways such as N-glycosylation in eukaryotes and biogenesis of the peptidoglycan (PG) cell wall in bacteria share a common strategy where nucleotide-sugars are used to build a membrane-bound oligosaccharide precursor that is linked to a phosphorylated isoprenoid lipid. Once made, these lipid-linked intermediates must be translocated across a membrane so that they can serve as substrates in a different cellular compartment. How translocation occurs is poorly understood, although it clearly requires a transporter or flippase. Identification of these transporters is notoriously difficult, and, in particular, the identity of the flippase of lipid II, an intermediate required for PG biogenesis, has been the subject of much debate. Here, I will review the body of work that has recently fueled this controversy, centered on proposed flippase candidates FtsW, MurJ, and AmJ.
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Affiliation(s)
- Natividad Ruiz
- Associate Professor, Department of Microbiology, The Ohio State University, Columbus, OH, USA
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18
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Harada Y, Hirayama H, Suzuki T. Generation and degradation of free asparagine-linked glycans. Cell Mol Life Sci 2015; 72:2509-33. [PMID: 25772500 PMCID: PMC11113800 DOI: 10.1007/s00018-015-1881-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 02/19/2015] [Accepted: 03/05/2015] [Indexed: 10/23/2022]
Abstract
Asparagine (N)-linked protein glycosylation, which takes place in the eukaryotic endoplasmic reticulum (ER), is important for protein folding, quality control and the intracellular trafficking of secretory and membrane proteins. It is known that, during N-glycosylation, considerable amounts of lipid-linked oligosaccharides (LLOs), the glycan donor substrates for N-glycosylation, are hydrolyzed to form free N-glycans (FNGs) by unidentified mechanisms. FNGs are also generated in the cytosol by the enzymatic deglycosylation of misfolded glycoproteins during ER-associated degradation. FNGs derived from LLOs and misfolded glycoproteins are eventually merged into one pool in the cytosol and the various glycan structures are processed to a near homogenous glycoform. This article summarizes the current state of our knowledge concerning the formation and catabolism of FNGs.
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Affiliation(s)
- Yoichiro Harada
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
| | - Hiroto Hirayama
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
| | - Tadashi Suzuki
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 Japan
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19
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Rush JS, Subramanian T, Subramanian KL, Onono FO, Waechter CJ, Spielmann HP. Novel Citronellyl-Based Photoprobes Designed to Identify ER Proteins Interacting with Dolichyl Phosphate in Yeast and Mammalian Cells. ACTA ACUST UNITED AC 2015; 9:123-141. [PMID: 27099830 DOI: 10.2174/2212796810666160216221610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
BACKGROUND Dolichyl phosphate-linked mono- and oligosaccharides (DLO) are essential intermediates in protein N-glycosylation, C- and O-mannosylation and GPI anchor biosynthesis. While many membrane proteins in the endoplasmic reticulum (ER) involved in the assembly of DLOs are known, essential proteins believed to be required for the transbilayer movement (flip-flopping) and proteins potentially involved in the regulation of DLO synthesis remain to be identified. METHODS The synthesis of a series of Dol-P derivatives composed of citronellyl-based photoprobes with benzophenone groups equipped with alkyne moieties for Huisgen "click" chemistry is now described to utilize as tools for identifying ER proteins involved in regulating the biosynthesis and transbilayer movement of lipid intermediates. In vitro enzymatic assays were used to establish that the photoprobes contain the critical structural features recognized by pertinent enzymes in the dolichol pathway. ER proteins that photoreacted with the novel probes were identified by MS. RESULTS The potential of the newly designed photoprobes, m-PAL-Cit-P and p-PAL-Cit-P, for identifying previously unidentified Dol-P-interacting proteins is supported by the observation that they are enzymatically mannosylated by Man-P-Dol synthase (MPDS) from Chinese Hamster Ovary (CHO) cells at an enzymatic rate similar to that for Dol-P. MS analyses reveal that DPM1, ALG14 and several other yeast ER proteins involved in DLO biosynthesis and lipid-mediated protein O-mannosylation photoreacted with the novel probes. CONCLUSION The newly-designed photoprobes described in this paper provide promising new tools for the identification of yet to be identified Dol-P interacting ER proteins in yeast and mammalian cells, including the Dol-P flippase required for the "re-cycling" of the glycosyl carrier lipid from the lumenal monolayer of the ER to the cytoplasmic leaflet for new rounds of DLO synthesis.
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Affiliation(s)
- Jeffrey S Rush
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Thangaiah Subramanian
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Karunai Leela Subramanian
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Fredrick O Onono
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
| | - Charles J Waechter
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA
| | - H Peter Spielmann
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA; University of Kentucky College of Medicine, Markey Cancer Center, University of Kentucky, Lexington, Kentucky 40536, USA; Kentucky Center for Structural Biology, University of Kentucky, Lexington, Kentucky 40536, USA; Department of Chemistry, University of Kentucky, Lexington, Kentucky 40536, USA
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20
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Comparative Analysis of Protein Glycosylation Pathways in Humans and the Fungal Pathogen Candida albicans. Int J Microbiol 2014; 2014:267497. [PMID: 25104959 PMCID: PMC4106090 DOI: 10.1155/2014/267497] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 06/06/2014] [Indexed: 11/30/2022] Open
Abstract
Protein glycosylation pathways are present in all kingdoms of life and are metabolic pathways found in all the life kingdoms. Despite sharing commonalities in their synthesis, glycans attached to glycoproteins have species-specific structures generated by the presence of different sets of enzymes and acceptor substrates in each organism. In this review, we present a comparative analysis of the main glycosylation pathways shared by humans and the fungal pathogen Candida albicans: N-linked glycosylation, O-linked mannosylation and glycosylphosphatidylinositol-anchorage. The knowledge of similarities and divergences between these metabolic pathways could help find new pharmacological targets for C. albicans infection.
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21
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Jarrell KF, Ding Y, Meyer BH, Albers SV, Kaminski L, Eichler J. N-linked glycosylation in Archaea: a structural, functional, and genetic analysis. Microbiol Mol Biol Rev 2014; 78:304-41. [PMID: 24847024 PMCID: PMC4054257 DOI: 10.1128/mmbr.00052-13] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
N-glycosylation of proteins is one of the most prevalent posttranslational modifications in nature. Accordingly, a pathway with shared commonalities is found in all three domains of life. While excellent model systems have been developed for studying N-glycosylation in both Eukarya and Bacteria, an understanding of this process in Archaea was hampered until recently by a lack of effective molecular tools. However, within the last decade, impressive advances in the study of the archaeal version of this important pathway have been made for halophiles, methanogens, and thermoacidophiles, combining glycan structural information obtained by mass spectrometry with bioinformatic, genetic, biochemical, and enzymatic data. These studies reveal both features shared with the eukaryal and bacterial domains and novel archaeon-specific aspects. Unique features of N-glycosylation in Archaea include the presence of unusual dolichol lipid carriers, the use of a variety of linking sugars that connect the glycan to proteins, the presence of novel sugars as glycan constituents, the presence of two very different N-linked glycans attached to the same protein, and the ability to vary the N-glycan composition under different growth conditions. These advances are the focus of this review, with an emphasis on N-glycosylation pathways in Haloferax, Methanococcus, and Sulfolobus.
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Affiliation(s)
- Ken F Jarrell
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Yan Ding
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Benjamin H Meyer
- Molecular Biology of Archaea, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Sonja-Verena Albers
- Molecular Biology of Archaea, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Lina Kaminski
- Department of Life Sciences, Ben Gurion University, Beersheva, Israel
| | - Jerry Eichler
- Department of Life Sciences, Ben Gurion University, Beersheva, Israel
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22
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Gao N, Holmes J, Lehrman MA. Letter to the Glycoforum: Improved protocols for preparing lipid-linked and related saccharides for Fluorophore-Assisted Carbohydrate Electrophoresis (FACE). Glycobiology 2014; 23:1111. [PMID: 24014203 DOI: 10.1093/glycob/cwt067] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Ningguo Gao
- Department of Pharmacology, UT Southwestern Medical Center at Dallas, 6001 Forest Park Rd. Dallas, TX 75390-9041
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23
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Breitling J, Aebi M. N-linked protein glycosylation in the endoplasmic reticulum. Cold Spring Harb Perspect Biol 2013; 5:a013359. [PMID: 23751184 DOI: 10.1101/cshperspect.a013359] [Citation(s) in RCA: 203] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The attachment of glycans to asparagine residues of proteins is an abundant and highly conserved essential modification in eukaryotes. The N-glycosylation process includes two principal phases: the assembly of a lipid-linked oligosaccharide (LLO) and the transfer of the oligosaccharide to selected asparagine residues of polypeptide chains. Biosynthesis of the LLO takes place at both sides of the endoplasmic reticulum (ER) membrane and it involves a series of specific glycosyltransferases that catalyze the assembly of the branched oligosaccharide in a highly defined way. Oligosaccharyltransferase (OST) selects the Asn-X-Ser/Thr consensus sequence on polypeptide chains and generates the N-glycosidic linkage between the side-chain amide of asparagine and the oligosaccharide. This ER-localized pathway results in a systemic modification of the proteome, the basis for the Golgi-catalyzed modification of the N-linked glycans, generating the large diversity of N-glycoproteome in eukaryotic cells. This article focuses on the processes in the ER. Based on the highly conserved nature of this pathway we concentrate on the mechanisms in the eukaryotic model organism Saccharomyces cerevisiae.
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Affiliation(s)
- Jörg Breitling
- Institute of Microbiology, Department of Biology, ETH Zurich, CH-8093 Zurich, Switzerland
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24
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Jelk J, Gao N, Serricchio M, Signorell A, Schmidt RS, Bangs JD, Acosta-Serrano A, Lehrman MA, Bütikofer P, Menon AK. Glycoprotein biosynthesis in a eukaryote lacking the membrane protein Rft1. J Biol Chem 2013; 288:20616-23. [PMID: 23720757 PMCID: PMC3711325 DOI: 10.1074/jbc.m113.479642] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 05/21/2013] [Indexed: 12/13/2022] Open
Abstract
Mature dolichol-linked oligosaccharides (mDLOs) needed for eukaryotic protein N-glycosylation are synthesized by a multistep pathway in which the biosynthetic lipid intermediate Man5GlcNAc2-PP-dolichol (M5-DLO) flips from the cytoplasmic to the luminal face of the endoplasmic reticulum. The endoplasmic reticulum membrane protein Rft1 is intimately involved in mDLO biosynthesis. Yeast genetic analyses implicated Rft1 as the M5-DLO flippase, but because biochemical tests challenged this assignment, the function of Rft1 remains obscure. To understand the role of Rft1, we sought to analyze mDLO biosynthesis in vivo in the complete absence of the protein. Rft1 is essential for yeast viability, and no Rft1-null organisms are currently available. Here, we exploited Trypanosoma brucei (Tb), an early diverging eukaryote whose Rft1 homologue functions in yeast. We report that TbRft1-null procyclic trypanosomes grow nearly normally. They have normal steady-state levels of mDLO and significant N-glycosylation, indicating robust M5-DLO flippase activity. Remarkably, the mutant cells have 30-100-fold greater steady-state levels of M5-DLO than wild-type cells. All N-glycans in the TbRft1-null cells originate from mDLO indicating that the M5-DLO excess is not available for glycosylation. These results suggest that rather than facilitating M5-DLO flipping, Rft1 facilitates conversion of M5-DLO to mDLO by another mechanism, possibly by acting as an M5-DLO chaperone.
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Affiliation(s)
- Jennifer Jelk
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - Ningguo Gao
- the Department of Pharmacology, University of Texas
Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Mauro Serricchio
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - Aita Signorell
- From the Department of Biochemistry, Weill Cornell Medical
College, New York, New York 10065
| | - Remo S. Schmidt
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - James D. Bangs
- the Department of Microbiology and Immunology, School of
Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York 14214,
and
| | - Alvaro Acosta-Serrano
- the Parasitology and Vector Biology Departments,
Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | - Mark A. Lehrman
- the Department of Pharmacology, University of Texas
Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Peter Bütikofer
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - Anant K. Menon
- From the Department of Biochemistry, Weill Cornell Medical
College, New York, New York 10065
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Aebi M. N-linked protein glycosylation in the ER. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2430-7. [PMID: 23583305 DOI: 10.1016/j.bbamcr.2013.04.001] [Citation(s) in RCA: 495] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 03/25/2013] [Accepted: 04/01/2013] [Indexed: 01/18/2023]
Abstract
N-linked protein glycosylation in the endoplasmic reticulum (ER) is a conserved two phase process in eukaryotic cells. It involves the assembly of an oligosaccharide on a lipid carrier, dolichylpyrophosphate and the transfer of the oligosaccharide to selected asparagine residues of polypeptides that have entered the lumen of the ER. The assembly of the oligosaccharide (LLO) takes place at the ER membrane and requires the activity of several specific glycosyltransferases. The biosynthesis of the LLO initiates at the cytoplasmic side of the ER membrane and terminates in the lumen where oligosaccharyltransferase (OST) selects N-X-S/T sequons of polypeptide and generates the N-glycosidic linkage between the side chain amide of asparagine and the oligosaccharide. The N-glycosylation pathway in the ER modifies a multitude of proteins at one or more asparagine residues with a unique carbohydrate structure that is used as a signalling molecule in their folding pathway. In a later stage of glycoprotein processing, the same systemic modification is used in the Golgi compartment, but in this process, remodelling of the N-linked glycans in a protein-, cell-type and species specific manner generates the high structural diversity of N-linked glycans observed in eukaryotic organisms. This article summarizes the current knowledge of the N-glycosylation pathway in the ER that results in the covalent attachment of an oligosaccharide to asparagine residues of polypeptide chains and focuses on the model organism Saccharomyces cerevisiae. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Affiliation(s)
- Markus Aebi
- Department of Biology, Institute of Microbiology, Zurich, Switzerland.
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26
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Orlean P. Architecture and biosynthesis of the Saccharomyces cerevisiae cell wall. Genetics 2012; 192:775-818. [PMID: 23135325 PMCID: PMC3522159 DOI: 10.1534/genetics.112.144485] [Citation(s) in RCA: 303] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 08/06/2012] [Indexed: 01/02/2023] Open
Abstract
The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins.
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Affiliation(s)
- Peter Orlean
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
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27
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Kaminski L, Guan Z, Abu-Qarn M, Konrad Z, Eichler J. AglR is required for addition of the final mannose residue of the N-linked glycan decorating the Haloferax volcanii S-layer glycoprotein. Biochim Biophys Acta Gen Subj 2012; 1820:1664-70. [PMID: 22750201 DOI: 10.1016/j.bbagen.2012.06.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/15/2012] [Accepted: 06/18/2012] [Indexed: 10/28/2022]
Abstract
BACKGROUND Recent studies of Haloferax volcanii have begun to elucidate the steps of N-glycosylation in Archaea, where this universal post-translational modification remains poorly described. In Hfx. volcanii, a series of Agl proteins catalyzes the assembly and attachment of a N-linked pentasaccharide to the S-layer glycoprotein. Although roles have been assigned to the majority of Agl proteins, others await description. In the following, the contribution of AglR to N-glycosylation was addressed. METHODS A combination of bioinformatics, gene deletion, mass spectrometry and metabolic radiolabeling served to show a role for AglR in archaeal N-glycosylation at both the dolichol phosphate and reporter glycoprotein levels. RESULTS The modified behavior of the S-layer glycoprotein isolated from cells lacking AglR points to an involvement of this protein in N-glycosylation. In cells lacking AglR, glycan-charged dolichol phosphate, including mannose-charged dolichol phosphate, accumulates. At the same time, the S-layer glycoprotein does not incorporate mannose, the final subunit of the N-linked pentasaccharide decorating this protein. AglR is a homologue of Wzx proteins, annotated as flippases responsible for delivering lipid-linked O-antigen precursor oligosaccharides across the bacterial plasma membrane during lipopolysaccharide biogenesis. CONCLUSIONS The effects resulting from aglR deletion are consistent with AglR interacting with dolichol phosphate-mannose, possibly acting as a dolichol phosphate-mannose flippase or contributing to such activity. GENERAL SIGNIFICANCE Little is known of how lipid-linked oligosaccharides are translocated across membrane during N-glycosylation. The possibility of Hfx. volcanii AglR mediating or contributing to flippase activity could help address this situation.
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Affiliation(s)
- Lina Kaminski
- Department of Life Sciences, Ben Gurion University of the Negev, Beersheva 84105, Israel
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Islam ST, Fieldhouse RJ, Anderson EM, Taylor VL, Keates RAB, Ford RC, Lam JS. A cationic lumen in the Wzx flippase mediates anionic O-antigen subunit translocation in Pseudomonas aeruginosa PAO1. Mol Microbiol 2012; 84:1165-76. [PMID: 22554073 PMCID: PMC3412221 DOI: 10.1111/j.1365-2958.2012.08084.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Heteropolymeric B-band O-antigen (O-Ag) biosynthesis in Pseudomonas aeruginosa PAO1 follows the Wzy-dependent pathway, beginning with translocation of undecaprenyl pyrophosphate-linked anionic O-Ag subunits (O units) from the inner to the outer leaflets of the inner membrane (IM). This translocation is mediated by the integral IM flippase Wzx. Through experimentally based and unbiased topological mapping, our group previously observed that Wzx possesses many charged and aromatic amino acid residues within its 12 transmembrane segments (TMS). Herein, site-directed mutagenesis targeting 102 residues was carried out on the TMS and loops of Wzx, followed by assessment of each construct's ability to restore B-band O-Ag production, identifying eight residues important for flippase function. The importance of various charged and aromatic residues was highlighted, predominantly within the TMS of the protein, revealing functional ‘hotspots’ within the flippase, particularly within TMS2 and TMS8. Construction of a tertiary structure homology model for Wzx indicated that TMS2 and TMS8 line a central cationic lumen. This is the first report to describe a charged flippase lumen for mediating anionic O-unit translocation across the hydrophobic IM.
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Affiliation(s)
- Salim T Islam
- Department of Molecular and Cellular Biology Biophysics Interdepartmental Group, University of Guelph, Guelph, ON N1G 2W1, Canada
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Hartley MD, Imperiali B. At the membrane frontier: a prospectus on the remarkable evolutionary conservation of polyprenols and polyprenyl-phosphates. Arch Biochem Biophys 2012; 517:83-97. [PMID: 22093697 PMCID: PMC3253937 DOI: 10.1016/j.abb.2011.10.018] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2011] [Revised: 10/28/2011] [Accepted: 10/30/2011] [Indexed: 11/20/2022]
Abstract
Long-chain polyprenols and polyprenyl-phosphates are ubiquitous and essential components of cellular membranes throughout all domains of life. Polyprenyl-phosphates, which include undecaprenyl-phosphate in bacteria and the dolichyl-phosphates in archaea and eukaryotes, serve as specific membrane-bound carriers in glycan biosynthetic pathways responsible for the production of cellular structures such as N-linked protein glycans and bacterial peptidoglycan. Polyprenyl-phosphates are the only form of polyprenols with a biochemically-defined role; however, unmodified or esterified polyprenols often comprise significant percentages of the cellular polyprenol pool. The strong evolutionary conservation of unmodified polyprenols as membrane constituents and polyprenyl-phosphates as preferred glycan carriers in biosynthetic pathways is poorly understood. This review surveys the available research to explore why unmodified polyprenols have been conserved in evolution and why polyprenyl-phosphates are universally and specifically utilized for membrane-bound glycan assembly.
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Affiliation(s)
- Meredith D. Hartley
- Department of Biology and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Barbara Imperiali
- Department of Biology and Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
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30
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Larkin A, Imperiali B. The expanding horizons of asparagine-linked glycosylation. Biochemistry 2011; 50:4411-26. [PMID: 21506607 DOI: 10.1021/bi200346n] [Citation(s) in RCA: 176] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Asparagine-linked glycosylation involves the sequential assembly of an oligosaccharide onto a polyisoprenyl donor, followed by the en bloc transfer of the glycan to particular asparagine residues within acceptor proteins. These N-linked glycans play a critical role in a wide variety of biological processes, such as protein folding, cellular targeting and motility, and the immune response. In the past decade, research in the field of N-linked glycosylation has achieved major advances, including the discovery of new carbohydrate modifications, the biochemical characterization of the enzymes involved in glycan assembly, and the determination of the biological impact of these glycans on target proteins. It is now firmly established that this enzyme-catalyzed modification occurs in all three domains of life. However, despite similarities in the overall logic of N-linked glycoprotein biosynthesis among the three kingdoms, the structures of the appended glycans are markedly different and thus influence the functions of elaborated proteins in various ways. Though nearly all eukaryotes produce the same nascent tetradecasaccharide (Glc(3)Man(9)GlcNAc(2)), heterogeneity is introduced into this glycan structure after it is transferred to the protein through a complex series of glycosyl trimming and addition steps. In contrast, bacteria and archaea display diversity within their N-linked glycan structures through the use of unique monosaccharide building blocks during the assembly process. In this review, recent progress toward gaining a deeper biochemical understanding of this modification across all three kingdoms will be summarized. In addition, a brief overview of the role of N-linked glycosylation in viruses will also be presented.
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Affiliation(s)
- Angelyn Larkin
- Department of Chemistry Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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31
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Abstract
Cells have thousands of different lipids. In the plasma membrane, and in membranes of the late secretory and endocytotic pathways, these lipids are not evenly distributed over the two leaflets of the lipid bilayer. The basis for this transmembrane lipid asymmetry lies in the fact that glycerolipids are primarily synthesized on the cytosolic and sphingolipids on the noncytosolic surface of cellular membranes, that cholesterol has a higher affinity for sphingolipids than for glycerolipids. In addition, P4-ATPases, "flippases," actively translocate the aminophospholipids phosphatidylserine and phosphatidylethanolamine to the cytosolic surface. ABC transporters translocate lipids in the opposite direction but they generally act as exporters rather than "floppases." The steady state asymmetry of the lipids can be disrupted within seconds by the activation of phospholipases and scramblases. The asymmetric lipid distribution has multiple implications for physiological events at the membrane surface. Moreover, the active translocation also contributes to the generation of curvature in the budding of transport vesicles.
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Affiliation(s)
- Gerrit van Meer
- Bijvoet Center and Institute of Biomembranes, Utrecht University, Utrecht, The Netherlands.
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32
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Vleugels W, Duvet S, Peanne R, Mir AM, Cacan R, Michalski JC, Matthijs G, Foulquier F. Identification of phosphorylated oligosaccharides in cells of patients with a congenital disorders of glycosylation (CDG-I). Biochimie 2011; 93:823-33. [PMID: 21315133 DOI: 10.1016/j.biochi.2011.01.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 01/29/2011] [Indexed: 11/24/2022]
Abstract
Protein N-glycosylation is initiated by the dolichol cycle in which the oligosaccharide precursor Glc(3)Man(9)GlcNAc(2)-PP-dolichol is assembled in the endoplasmic reticulum (ER). One critical step in the dolichol cycle concerns the availability of Dol-P at the cytosolic face of the ER membrane. In RFT1 cells, the lipid-linked oligosaccharide (LLO) intermediate Man(5)GlcNAc(2)-PP-Dol accumulates at the cytosolic face of the ER membrane. Since Dol-P is a rate-limiting intermediate during protein N-glycosylation, continuous accumulation of Man(5)GlcNAc(2)-PP-Dol would block the dolichol cycle. Hence, we investigated the molecular mechanisms by which accumulating Man(5)GlcNAc(2)-PP-Dol could be catabolized in RFT1 cells. On the basis of metabolic labeling experiments and in comparison to human control cells, we identified phosphorylated oligosaccharides (POS), not found in human control cells and present evidence that they originate from the accumulating LLO intermediates. In addition, POS were also detected in other CDG patients' cells accumulating specific LLO intermediates at different cellular locations. Moreover, the enzymatic activity that hydrolyses oligosaccharide-PP-Dol into POS was identified in human microsomal membranes and required Mn(2+) for optimal activity. In CDG patients' cells, we thus identified and characterized POS that could result from the catabolism of accumulating LLO intermediates.
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Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, B-3000 Leuven, Belgium
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33
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Hug I, Feldman MF. Analogies and homologies in lipopolysaccharide and glycoprotein biosynthesis in bacteria. Glycobiology 2010; 21:138-51. [PMID: 20871101 DOI: 10.1093/glycob/cwq148] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Bacteria generate and attach countless glycan structures to diverse macromolecules. Despite this diversity, the mechanisms of glycoconjugate biosynthesis are often surprisingly similar. The focus of this review is on the commonalities between lipopolysaccharide (LPS) and glycoprotein assembly pathways and their evolutionary relationship. Three steps that are essential for both pathways are completed by membrane proteins. These include the initiation of glycan assembly through the attachment of a first sugar residue onto the lipid carrier undecaprenyl pyrophosphate, the translocation across the plasma membrane and the final transfer onto proteins or lipid A-core. Two families of initiating enzymes have been described: the polyprenyl-P N-acetylhexosamine-1-P transferases and the polyprenyl-P hexosamine-1-P transferases, represented by Escherichia coli WecA and Salmonella enterica WbaP, respectively. Translocases are either Wzx-like flippases or adenosine triphosphate (ATP)-binding cassette transporters (ABC transporters). The latter can consist either of two polypeptides, Wzt and Wzm, or of a single polypeptide homolog to the Campylobacter jejuni PglK. Finally, there are two families of conjugating enzymes, the N-oligosaccharyltransferases (N-OTase), best represented by C. jejuni PglB, and the O-OTases, including Neisseria meningitidis PglL and the O antigen ligases involved in LPS biosynthesis. With the exception of the N-OTases, probably restricted to glycoprotein synthesis, members of all these transmembrane protein families can be involved in the synthesis of both glycoproteins and LPS. Because many translocation and conjugation enzymes display relaxed substrate specificity, these bacterial enzymes could be exploited in engineered living bacteria for customized glycoconjugate production, generating potential vaccines and therapeutics.
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Affiliation(s)
- Isabelle Hug
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
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34
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Song H, Qian W, Wang H, Qiu B. Identification and functional characterization of the HpALG11 and the HpRFT1 genes involved in N-linked glycosylation in the methylotrophic yeast Hansenula polymorpha. Glycobiology 2010; 20:1665-74. [DOI: 10.1093/glycob/cwq121] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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35
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Peric D, Durrant-Arico C, Delenda C, Dupré T, De Lonlay P, de Baulny HO, Pelatan C, Bader-Meunier B, Danos O, Chantret I, Moore SEH. The compartmentalisation of phosphorylated free oligosaccharides in cells from a CDG Ig patient reveals a novel ER-to-cytosol translocation process. PLoS One 2010; 5:e11675. [PMID: 20652024 PMCID: PMC2907391 DOI: 10.1371/journal.pone.0011675] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 06/14/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Biosynthesis of the dolichol linked oligosaccharide (DLO) required for protein N-glycosylation starts on the cytoplasmic face of the ER to give Man(5)GlcNAc(2)-PP-dolichol, which then flips into the ER for further glycosylation yielding mature DLO (Glc(3)Man(9)GlcNAc(2)-PP-dolichol). After transfer of Glc(3)Man(9)GlcNAc(2) onto protein, dolichol-PP is recycled to dolichol-P and reused for DLO biosynthesis. Because de novo dolichol synthesis is slow, dolichol recycling is rate limiting for protein glycosylation. Immature DLO intermediates may also be recycled by pyrophosphatase-mediated cleavage to yield dolichol-P and phosphorylated oligosaccharides (fOSGN2-P). Here, we examine fOSGN2-P generation in cells from patients with type I Congenital Disorders of Glycosylation (CDG I) in which defects in the dolichol cycle cause accumulation of immature DLO intermediates and protein hypoglycosylation. METHODS AND PRINCIPAL FINDINGS In EBV-transformed lymphoblastoid cells from CDG I patients and normal subjects a correlation exists between the quantities of metabolically radiolabeled fOSGN2-P and truncated DLO intermediates only when these two classes of compounds possess 7 or less hexose residues. Larger fOSGN2-P were difficult to detect despite an abundance of more fully mannosylated and glucosylated DLO. When CDG Ig cells, which accumulate Man(7)GlcNAc(2)-PP-dolichol, are permeabilised so that vesicular transport and protein synthesis are abolished, the DLO pool required for Man(7)GlcNAc(2)-P generation could be depleted by adding exogenous glycosylation acceptor peptide. Under conditions where a glycotripeptide and neutral free oligosaccharides remain predominantly in the lumen of the ER, Man(7)GlcNAc(2)-P appears in the cytosol without detectable generation of ER luminal Man(7)GlcNAc(2)-P. CONCLUSIONS AND SIGNIFICANCE The DLO pools required for N-glycosylation and fOSGN2-P generation are functionally linked and this substantiates the hypothesis that pyrophosphatase-mediated cleavage of DLO intermediates yields recyclable dolichol-P. The kinetics of cytosolic fOSGN2-P generation from a luminally-generated DLO intermediate demonstrate the presence of a previously undetected ER-to-cytosol translocation process for either fOSGN2-P or DLO.
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Affiliation(s)
- Delphine Peric
- INSERM U773 CRB3, Paris, France
- Université Denis Diderot, Paris 7, Paris, France
| | | | | | - Thierry Dupré
- INSERM U773 CRB3, Paris, France
- Université Denis Diderot, Paris 7, Paris, France
- AP-HP, Hôpital Bichat-Claude Bernard, Biochimie Métabolique et Cellulaire, Paris, France
| | - Pascale De Lonlay
- Département de Pédiatrie, Hôpital Necker-Enfants Malades, Paris, France
| | | | - Cécile Pelatan
- Centre Hospitalier, Service de Pédiatrie, Le Mans, France
| | | | - Olivier Danos
- Généthon: Evry, France
- INSERM U781, Hôpital Necker-Enfants Malades, Paris, France
| | - Isabelle Chantret
- INSERM U773 CRB3, Paris, France
- Université Denis Diderot, Paris 7, Paris, France
| | - Stuart E. H. Moore
- INSERM U773 CRB3, Paris, France
- Université Denis Diderot, Paris 7, Paris, France
- * E-mail:
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Biochemical characterization, membrane association and identification of amino acids essential for the function of Alg11 from Saccharomyces cerevisiae, an alpha1,2-mannosyltransferase catalysing two sequential glycosylation steps in the formation of the lipid-linked core oligosaccharide. Biochem J 2010; 426:205-17. [PMID: 19929855 DOI: 10.1042/bj20091121] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The biosynthesis of asparagine-linked glycans occurs in an evolutionarily conserved manner with the assembly of the unique lipid-linked oligosaccharide precursor Glc3Man9GlcNAc2-PP-Dol at the ER (endoplasmic reticulum). In the present study we characterize Alg11 from yeast as a mannosyltransferase catalysing the sequential transfer of two alpha1,2-linked mannose residues from GDP-mannose to Man3GlcNAc2-PP-Dol and subsequently to Man4GlcNAc2-PP-Dol forming the Man5GlcNAc2-PP-Dol intermediate at the cytosolic side of the ER before flipping to the luminal side. Alg11 is predicted to contain three hydrophobic transmembrane-spanning helices. Using Alg11 topology reporter fusion constructs, we show that only the N-terminal domain fulfils this criterion. Surprisingly, this domain can be deleted without disturbing glycosyltransferase function and membrane association, indicating also that the other two hydrophobic domains contribute to ER localization, but in a non-transmembrane manner. By site-directed mutagenesis we investigated amino acids important for transferase activity. We demonstrate that the first glutamate residue in the EX7E motif, conserved in a variety of glycosyltransferases, is more critical than the second, and loss of Alg11 function occurs only when both glutamate residues are exchanged, or when the mutation of the first glutamate residue is combined with replacement of another amino acid in the motif. This indicates that perturbations in EX7E are not restricted to the second glutamate residue. Moreover, Gly85 and Gly87, within a glycine-rich domain as part of a potential flexible loop, were found to be required for Alg11 function. Similarly, a conserved lysine residue, Lys319, was identified as being important for activity, which could be involved in the binding of the phosphate of the glycosyl donor.
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37
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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38
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Jaeken J, Vleugels W, Régal L, Corchia C, Goemans N, Haeuptle MA, Foulquier F, Hennet T, Matthijs G, Dionisi-Vici C. RFT1-CDG: deafness as a novel feature of congenital disorders of glycosylation. J Inherit Metab Dis 2009; 32 Suppl 1:S335-8. [PMID: 19856127 DOI: 10.1007/s10545-009-1297-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/24/2009] [Accepted: 09/25/2009] [Indexed: 10/20/2022]
Abstract
Congenital disorders of glycosylation (CDG) are genetic diseases due to defects in the synthesis of glycans and in the attachment of glycans to lipids and proteins. Actually, some 42 CDG are known including defects in protein N-glycosylation, in protein O-glycosylation, in lipid glycosylation, and in multiple and other glycosylation pathways. Most CDG are multisystem diseases and a large number of signs and symptoms have already been reported in CDG. An exception to this is deafness. This symptom has not been observed as a consistent feature in CDG. In 2008, a novel defect was identified in protein N-glycosylation, namely in RFT1. This is a defect in the assembly of N-glycans. RFT1 is involved in the transfer of Man(5)GlcNAc(2)-PP-Dol from the cytoplasmic to the luminal side of the endoplasmic reticulum. According to the novel nomenclature (non-italicized gene symbol followed by -CDG) this defect is named RFT1-CDG. Recently, three other patients with RFT1-CDG have been reported and here we report two novel patients. Remarkably, all six patients with RFT1-CDG show sensorineural deafness as part of a severe neurological syndrome. We conclude that RFT1-CDG is the first 'deafness-CDG'. CDG should be included in the work-up of congenital, particularly syndromic, hearing loss.
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Affiliation(s)
- J Jaeken
- Center for Metabolic Disease, University of Leuven, Leuven, Belgium.
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39
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Abstract
The biosynthesis of glycoconjugates such as N-glycoproteins and GPI-anchored proteins in eukaryotes and cell wall peptidoglycan and lipopolysaccharide in bacteria requires lipid intermediates to be flipped rapidly across the endoplasmic reticulum or bacterial cytoplasmic membrane (so-called biogenic membranes). Rapid flipping is also required to normalize the number of glycerophospholipids in the two leaflets of the bilayer as the membrane expands in a growing cell. Although lipids diffuse rapidly in the plane of the membrane, the intrinsic rate at which they flip across membranes is very low. Biogenic membranes possess dedicated lipid transporters or flippases to increase flipping to a physiologically sufficient rate. The flippases are "ATP-independent" and facilitate "downhill" transport. Most predicted biogenic membrane flippases have not been identified at the molecular level, and the few flippases that have been identified by genetic approaches have not been biochemically validated. Here we summarize recent progress on this fundamental topic and speculate on the mechanism(s) by which biogenic membrane flippases facilitate transbilayer lipid movement.
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Affiliation(s)
- Sumana Sanyal
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, 1300 York Avenue, New York, New York 10065
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