1
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Huang C, Seino J, Honda A, Fujihira H, Wu D, Okahara K, Kitazume S, Nakaya S, Kitajima K, Sato C, Suzuki T. Rat hepatocytes secrete free oligosaccharides. J Biol Chem 2024; 300:105712. [PMID: 38309509 PMCID: PMC10912633 DOI: 10.1016/j.jbc.2024.105712] [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: 08/09/2023] [Revised: 01/24/2024] [Accepted: 01/25/2024] [Indexed: 02/05/2024] Open
Abstract
We recently established a method for the isolation of serum-free oligosaccharides, and characterized various features of their structures. However, the precise mechanism for how these glycans are formed still remains unclarified. To further investigate the mechanism responsible for these serum glycans, here, we utilized rat primary hepatocytes to examine whether they are able to secrete free glycans. Our findings indicated that a diverse array of free oligosaccharides such as sialyl/neutral free N-glycans (FNGs), as well as sialyl lactose/LacNAc-type glycans, were secreted into the culture medium by primary hepatocytes. The structural features of these free glycans in the medium were similar to those isolated from the sera of the same rat. Further evidence suggested that an oligosaccharyltransferase is involved in the release of the serum-free N-glycans. Our results indicate that the liver is indeed secreting various types of free glycans directly into the serum.
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Affiliation(s)
- Chengcheng Huang
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Junichi Seino
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Akinobu Honda
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Haruhiko Fujihira
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan
| | - Di Wu
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Chikusa, Nagoya, Japan
| | - Kyohei Okahara
- Discovery Concept Validation Function, KAN Research Institute, Inc, Kobe, Japan
| | - Shinobu Kitazume
- Department of Clinical Laboratory Sciences, School of Health Sciences, Fukushima Medical University, Fukushima, Japan
| | - Shuichi Nakaya
- Analytical & Measuring Instruments Division, Shimadzu Corporation, Kyoto, Japan
| | - Ken Kitajima
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Chikusa, Nagoya, Japan
| | - Chihiro Sato
- Bioscience and Biotechnology Center, Nagoya University, Chikusa, Nagoya, Japan; Institute for Glyco-core Research (iGCORE), Nagoya University, Chikusa, Nagoya, Japan
| | - Tadashi Suzuki
- Glycometabolic Biochemistry Laboratory, RIKEN-Cluster for Pioneering Research, Wako, Saitama, Japan.
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2
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Huang JY, Wang HC, Chen YC, Wang PS, Lin SJ, Chang YS, Liu KF, Lo CF. A shrimp glycosylase protein, PmENGase, interacts with WSSV envelope protein VP41B and is involved in WSSV pathogenesis. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2020; 108:103667. [PMID: 32147468 DOI: 10.1016/j.dci.2020.103667] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 02/28/2020] [Accepted: 02/29/2020] [Indexed: 06/10/2023]
Abstract
Viral glycoproteins are expressed by many viruses, and during infection they usually play very important roles, such as receptor attachment or membrane fusion. The mature virion of the white spot syndrome virus (WSSV) is unusual in that it contains no glycosylated proteins, and there are currently no reports of any glycosylation mechanisms in the pathogenesis of this virus. In this study, we cloned a glycosylase, mannosyl-glycoprotein endo-β-N-acetylglucosaminidase (ENGase, EC 3.2.1.96), from Penaeus monodon and found that it was significantly up-regulated in WSSV-infected shrimp. A yeast two-hybrid assay showed that PmENGase interacted with both structural and non-structural proteins, and GST-pull down and co-immunoprecipitation (Co-IP) assays confirmed its interaction with the envelope protein VP41B. In the WSSV challenge tests, the cumulative mortality and viral copy number were significantly decreased in the PmEngase-silenced shrimp, from which we conclude that shrimp glycosylase interacts with WSSV in a way that benefits the virus. Lastly, we speculate that the deglycosylation activity of PmENGase might account for the absence of glycosylated proteins in the WSSV virion.
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Affiliation(s)
- Jiun-Yan Huang
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, 701, Taiwan
| | - Hao-Ching Wang
- Program for Translational Medicine, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei, 110, Taiwan; Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, 110, Taiwan
| | - Yu-Chun Chen
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, 701, Taiwan
| | - Po-Sue Wang
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, 701, Taiwan
| | - Shin-Jen Lin
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, 701, Taiwan
| | - Yun-Shiang Chang
- Department of Molecular Biotechnology, College of Biotechnology and Bioresources, Da-Yeh University, Changhua, 515, Taiwan
| | - Kuan-Fu Liu
- Tungkang Biotechnology Research Center, Fisheries Research Institute, Council of Agriculture, Pingtung, Taiwan
| | - Chu-Fang Lo
- International Center for the Scientific Development of Shrimp Aquaculture, National Cheng Kung University, Tainan, 701, Taiwan.
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3
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Caspase-8 Regulates Endoplasmic Reticulum Stress-Induced Necroptosis Independent of the Apoptosis Pathway in Auditory Cells. Int J Mol Sci 2019; 20:ijms20235896. [PMID: 31771290 PMCID: PMC6928907 DOI: 10.3390/ijms20235896] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 11/15/2019] [Accepted: 11/21/2019] [Indexed: 12/20/2022] Open
Abstract
The aim of this study is to elucidate the detailed mechanism of endoplasmic reticulum (ER) stress-induced auditory cell death based on the function of the initiator caspases and molecular complex of necroptosis. Here, we demonstrated that ER stress initiates not only caspase-9-dependent intrinsic apoptosis along with caspase-3, but also receptor-interacting serine/threonine kinase (RIPK)1-dependent necroptosis in auditory cells. We observed the ultrastructural characteristics of both apoptosis and necroptosis in tunicamycin-treated cells under transmission electron microscopy (TEM). We demonstrated that ER stress-induced necroptosis was dependent on the induction of RIPK1, negatively regulated by caspase-8 in auditory cells. Our data suggested that ER stress-induced intrinsic apoptosis depends on the induction of caspase-9 along with caspase-3 in auditory cells. The results of this study reveal that necroptosis could exist for the alternative backup cell death route of apoptosis in auditory cells under ER stress. Interestingly, our data results in a surge in the recognition that therapies aimed at the inner ear protection effect by caspase inhibitors like zVAD-fmk might arrest apoptosis but can also have the unanticipated effect of promoting necroptosis. Thus, RIPK1-dependent necroptosis would be a new therapeutic target for the treatment of sensorineural hearing loss due to ER stress.
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Hirayama H. Biology of Free Oligosaccharides: Function and Metabolism of Free N-Glycans in Eukaryote. TRENDS GLYCOSCI GLYC 2018. [DOI: 10.4052/tigg.1761.1e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Hiroto Hirayama
- Suzuki Project, T-CiRA Joint Program, Glycometabolic Biochemistry Laboratory, RIKEN
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5
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Deglycosylating enzymes acting on N- glycans in fungi: Insights from a genome survey. Biochim Biophys Acta Gen Subj 2017; 1861:2551-2558. [DOI: 10.1016/j.bbagen.2017.08.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 08/16/2017] [Accepted: 08/28/2017] [Indexed: 11/19/2022]
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6
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Kishino A, Hayashi K, Hidai C, Masuda T, Nomura Y, Oshima T. XBP1-FoxO1 interaction regulates ER stress-induced autophagy in auditory cells. Sci Rep 2017; 7:4442. [PMID: 28667325 PMCID: PMC5493624 DOI: 10.1038/s41598-017-02960-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 04/21/2017] [Indexed: 01/07/2023] Open
Abstract
The purpose of this study was to clarify the relationship among X-box-binding protein 1 unspliced, spliced (XBP1u, s), Forkhead box O1 (FoxO1) and autophagy in the auditory cells under endoplasmic reticulum (ER) stress. In addition, the relationship between ER stress that causes unfolded protein response (UPR) and autophagy was also investigated. The present study reported ER stress induction by tunicamycin treatment that resulted in IRE1α-mediated XBP1 mRNA splicing and autophagy. XBP1 mRNA splicing and FoxO1 were found to be involved in ER stress-induced autophagy. This inference was based on the observation that the expression of LC3-II was suppressed by knockdown of IRE1α, XBP1 or FoxO1. In addition, XBP1u was found to interact with XBP1s in auditory cells under ER stress, functioning as a negative feedback regulator that was based on two important findings. Firstly, there was a significant inverse correlation between XBP1u and XBP1s expressions, and secondly, the expression of XBP1 protein showed different dynamics compared to the XBP1 mRNA level. Furthermore, our results regarding the relationship between XBP1 and FoxO1 by small interfering RNA (siRNA) paradoxically showed negative regulation of FoxO1 expression by XBP1. Our findings revealed that the XBP1-FoxO1 interaction regulated the ER stress-induced autophagy in auditory cells.
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Affiliation(s)
- Akihiro Kishino
- Department of Otolaryngology, School of Medicine, Nihon University, Tokyo, 173-8610, Japan
| | - Ken Hayashi
- Department of Otolaryngology, Kamio Memorial Hospital, Tokyo, 101-0063, Japan
| | - Chiaki Hidai
- Department of Physiology, School of Medicine, Nihon University, Tokyo, 173-8610, Japan
| | - Takeshi Masuda
- Department of Otolaryngology, School of Medicine, Nihon University, Tokyo, 173-8610, Japan
| | - Yasuyuki Nomura
- Department of Otolaryngology, School of Medicine, Nihon University, Tokyo, 173-8610, Japan
| | - Takeshi Oshima
- Department of Otolaryngology, School of Medicine, Nihon University, Tokyo, 173-8610, Japan.
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7
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Fujihira H, Masahara-Negishi Y, Tamura M, Huang C, Harada Y, Wakana S, Takakura D, Kawasaki N, Taniguchi N, Kondoh G, Yamashita T, Funakoshi Y, Suzuki T. Lethality of mice bearing a knockout of the Ngly1-gene is partially rescued by the additional deletion of the Engase gene. PLoS Genet 2017; 13:e1006696. [PMID: 28426790 PMCID: PMC5398483 DOI: 10.1371/journal.pgen.1006696] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 03/15/2017] [Indexed: 11/25/2022] Open
Abstract
The cytoplasmic peptide:N-glycanase (Ngly1 in mammals) is a de-N-glycosylating enzyme that is highly conserved among eukaryotes. It was recently reported that subjects harboring mutations in the NGLY1 gene exhibited severe systemic symptoms (NGLY1-deficiency). While the enzyme obviously has a critical role in mammals, its precise function remains unclear. In this study, we analyzed Ngly1-deficient mice and found that they are embryonic lethal in C57BL/6 background. Surprisingly, the additional deletion of the gene encoding endo-β-N-acetylglucosaminidase (Engase), which is another de-N-glycosylating enzyme but leaves a single GlcNAc at glycosylated Asn residues, resulted in the partial rescue of the lethality of the Ngly1-deficient mice. Additionally, we also found that a change in the genetic background of C57BL/6 mice, produced by crossing the mice with an outbred mouse strain (ICR) could partially rescue the embryonic lethality of Ngly1-deficient mice. Viable Ngly1-deficient mice in a C57BL/6 and ICR mixed background, however, showed a very severe phenotype reminiscent of the symptoms of NGLY1-deficiency subjects. Again, many of those defects were strongly suppressed by the additional deletion of Engase in the C57BL/6 and ICR mixed background. The defects observed in Ngly1/Engase-deficient mice (C57BL/6 background) and Ngly1-deficient mice (C57BL/6 and ICR mixed background) closely resembled some of the symptoms of patients with an NGLY1-deficiency. These observations strongly suggest that the Ngly1- or Ngly1/Engase-deficient mice could serve as a valuable animal model for studies related to the pathogenesis of the NGLY1-deficiency, and that cytoplasmic ENGase represents one of the potential therapeutic targets for this genetic disorder. Ngly1 is a cytoplasmic de-N-glycosylating enzyme that is ubiquitously found in eukaryotes. This enzyme is involved in a process referred to as endoplasmic reticulum-associated degradation (ERAD), one of the quality control mechanisms for newly synthesized proteins. A genetic disorder, NGLY1-deficiency, caused by mutations in the NGLY1 gene has recently been discovered. However, the precise mechanism for the pathogenesis of this devastating disease continues to remain unclear. We report herein that Ngly1-deficient mice are embryonically lethal in a C57BL/6 background. Surprisingly, the lethality was suppressed by crossing the mice with an outbred mouse strain (ICR), suggesting that the phenotypic consequence of Ngly1 is greatly influenced by their genetic background. In both cases, the additional deletion of Engase in Ngly1-deficient mice could strongly mitigate the phenotypes. Interestingly, the remaining defects in Ngly1-deficient or Ngly1/Engase-deficient mice were reminiscent of the symptoms of subjects with an NGLY1-deficiency. Our results clearly point to the importance of Ngly1 in mammals and show that the inhibition of ENGase represents an effective therapy for treating an NGLY1-deficiency. Most importantly, the mice described herein could serve as valuable viable model mice for studies related to the pathophysiology of an NGLY1-deficiency.
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Affiliation(s)
- Haruhiko Fujihira
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
| | - Yuki Masahara-Negishi
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
| | - Masaru Tamura
- Technology and Development Team for Mouse Phenotype Analysis, Japan Mouse Clinic, BioResourse Center, RIKEN, Ibaraki, Japan
| | - Chengcheng Huang
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
| | - Yoichiro Harada
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
| | - Shigeharu Wakana
- Technology and Development Team for Mouse Phenotype Analysis, Japan Mouse Clinic, BioResourse Center, RIKEN, Ibaraki, Japan
| | - Daisuke Takakura
- Graduate School of Medical Life Science, Yokohama City University, Kanagawa, Japan
| | - Nana Kawasaki
- Graduate School of Medical Life Science, Yokohama City University, Kanagawa, Japan
| | - Naoyuki Taniguchi
- Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
| | - Gen Kondoh
- Laboratory of Integrative Biological Science, Institute for Frontier Life and Medical Sciences, Kyoto University, Kyoto, Japan
| | - Tadashi Yamashita
- Laboratory of Biochemistry, School of Veterinary Medicine, Azabu University, Kanagawa, Japan
| | - Yoko Funakoshi
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
| | - Tadashi Suzuki
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Saitama, Japan
- * E-mail:
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8
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Occurrence of complex type free N-glycans with a single GlcNAc residue at the reducing termini in the fresh-water plant, Egeria densa. Glycoconj J 2017; 34:229-240. [DOI: 10.1007/s10719-016-9758-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/26/2016] [Accepted: 12/22/2016] [Indexed: 10/20/2022]
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9
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Katoh T, Katayama T, Tomabechi Y, Nishikawa Y, Kumada J, Matsuzaki Y, Yamamoto K. Generation of a Mutant Mucor hiemalis Endoglycosidase That Acts on Core-fucosylated N-Glycans. J Biol Chem 2016; 291:23305-23317. [PMID: 27629418 DOI: 10.1074/jbc.m116.737395] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Indexed: 11/06/2022] Open
Abstract
Endo-β-N-acetylglucosaminidase M (Endo-M), an endoglycosidase from the fungus Mucor hiemalis, is a useful tool for chemoenzymatic synthesis of glycoconjugates, including glycoprotein-based therapeutics having a precisely defined glycoform, by virtue of its transglycosylation activity. Although Endo-M has been known to act on various N-glycans, it does not act on core-fucosylated N-glycans, which exist widely in mammalian glycoproteins, thus limiting its application. Therefore, we performed site-directed mutagenesis on Endo-M to isolate mutant enzymes that are able to act on mammalian-type core-α1,6-fucosylated glycans. Among the Endo-M mutant enzymes generated, those in which the tryptophan at position 251 was substituted with alanine or asparagine showed altered substrate specificities. Such mutant enzymes exhibited increased hydrolysis of a synthetic α1,6-fucosylated trimannosyl core structure, whereas their activity on the afucosylated form decreased. In addition, among the Trp-251 mutants, the W251N mutant was most efficient in hydrolyzing the core-fucosylated substrate. W251N mutants could act on the immunoglobulin G-derived core-fucosylated glycopeptides and human lactoferrin glycoproteins. This mutant was also capable of transferring the sialyl glycan from an activated substrate intermediate (sialyl glyco-oxazoline) onto an α1,6-fucosyl-N-acetylglucosaminyl biotin. Furthermore, the W251N mutant gained a glycosynthase-like activity when a N175Q substitution was introduced and it caused accumulation of the transglycosylation products. These findings not only give insights into the substrate recognition mechanism of glycoside hydrolase family 85 enzymes but also widen their scope of application in preparing homogeneous glycoforms of core-fucosylated glycoproteins for the production of potent glycoprotein-based therapeutics.
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Affiliation(s)
- Toshihiko Katoh
- From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan,
| | - Takane Katayama
- From the Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.,the Host-Microbe Interaction Research Laboratory and
| | - Yusuke Tomabechi
- the Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi, Ishikawa 921-8836, Japan, and
| | - Yoshihide Nishikawa
- Tokyo Chemical Industry Co., Ltd., 6-15-9 Toshima, Kita-ku, Tokyo 114-0003, Japan
| | - Jyunichi Kumada
- Tokyo Chemical Industry Co., Ltd., 6-15-9 Toshima, Kita-ku, Tokyo 114-0003, Japan
| | - Yuji Matsuzaki
- Tokyo Chemical Industry Co., Ltd., 6-15-9 Toshima, Kita-ku, Tokyo 114-0003, Japan
| | - Kenji Yamamoto
- the Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi, Ishikawa 921-8836, Japan, and
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10
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Sakaguchi K, Katoh T, Yamamoto K. Transglycosidase-like activity ofMucor hiemalisendoglycosidase mutants enabling the synthesis of glycoconjugates using a natural glycan donor. Biotechnol Appl Biochem 2015; 63:812-819. [DOI: 10.1002/bab.1433] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Accepted: 08/06/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Kouta Sakaguchi
- Research Institute for Bioresources and Biotechnology; Ishikawa Prefectural University; Nonoichi Ishikawa Japan
| | - Toshihiko Katoh
- Research Institute for Bioresources and Biotechnology; Ishikawa Prefectural University; Nonoichi Ishikawa Japan
| | - Kenji Yamamoto
- Research Institute for Bioresources and Biotechnology; Ishikawa Prefectural University; Nonoichi Ishikawa Japan
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11
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Harada Y, Masahara-Negishi Y, Suzuki T. Cytosolic-free oligosaccharides are predominantly generated by the degradation of dolichol-linked oligosaccharides in mammalian cells. Glycobiology 2015. [DOI: 10.1093/glycob/cwv055] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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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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13
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Hirayama H, Hosomi A, Suzuki T. Physiological and molecular functions of the cytosolic peptide:N-glycanase. Semin Cell Dev Biol 2015; 41:110-20. [DOI: 10.1016/j.semcdb.2014.11.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Revised: 11/25/2014] [Accepted: 11/26/2014] [Indexed: 01/04/2023]
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14
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Endo-β-N-acetylglucosaminidase forms N-GlcNAc protein aggregates during ER-associated degradation in Ngly1-defective cells. Proc Natl Acad Sci U S A 2015; 112:1398-403. [PMID: 25605922 DOI: 10.1073/pnas.1414593112] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cytoplasmic peptide:N-glycanase (PNGase; Ngly1 in mice) is a deglycosylating enzyme involved in the endoplasmic reticulum (ER)-associated degradation (ERAD) process. The precise role of Ngly1 in the ERAD process, however, remains unclear in mammals. The findings reported herein, using mouse embryonic fibroblast (MEF) cells, that the ablation of Ngly1 causes dysregulation of the ERAD process. Interestingly, not only delayed degradation but also the deglycosylation of a misfolded glycoprotein was observed in Ngly1(-/-) MEF cells. The unconventional deglycosylation reaction was found to be catalyzed by the cytosolic endo-β-N-acetylglucosaminidase (ENGase), generating aggregation-prone N-GlcNAc proteins. The ERAD dysregulation in cells lacking Ngly1 was restored by the additional knockout of ENGase gene. Thus, our study underscores the functional importance of Ngly1 in the ERAD process and provides a potential mechanism underlying the phenotypic consequences of a newly emerging genetic disorder caused by mutation of the human NGLY1 gene.
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15
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Suzuki T, Harada Y. Non-lysosomal degradation pathway for N-linked glycans and dolichol-linked oligosaccharides. Biochem Biophys Res Commun 2014; 453:213-9. [PMID: 24866240 DOI: 10.1016/j.bbrc.2014.05.075] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 05/16/2014] [Indexed: 01/11/2023]
Abstract
There is growing evidence that asparagine (N)-linked glycans play pivotal roles in protein folding and intra- or intercellular trafficking of N-glycosylated proteins. During the N-glycosylation of proteins, significant amounts of free oligosaccharides (fOSs) and phosphorylated oligosaccharides (POSs) are generated at the endoplasmic reticulum (ER) membrane by unclarified mechanisms. fOSs are also formed in the cytosol by the enzymatic deglycosylation of misfolded glycoproteins destined for proteasomal degradation. This article summarizes the current knowledge of the molecular and regulatory mechanisms underlying the formation of fOSs and POSs in mammalian cells and Saccharomyces cerevisiae.
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Affiliation(s)
- Tadashi Suzuki
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, RIKEN Global Research Cluster, Japan.
| | - Yoichiro Harada
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, RIKEN Global Research Cluster, Japan
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16
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Katoh T, Takase J, Tani Y, Amamoto R, Aoshima N, Tiemeyer M, Yamamoto K, Ashida H. Deficiency of α-glucosidase I alters glycoprotein glycosylation and lifespan in Caenorhabditis elegans. Glycobiology 2013; 23:1142-51. [PMID: 23836288 DOI: 10.1093/glycob/cwt051] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Endoplasmic reticulum (ER) α-glucosidase I is an enzyme that trims the distal α1,2-linked glucose (Glc) residue from the Glc3Man9GlcNAc2 oligosaccharide following its addition to nascent glycoproteins in the initial step of processing. This reaction is critical to the subsequent processing of N-glycans and thus defects in α-glucosidase I gene in human cause congenital disorder of glycosylation (CDG) type IIb. We identified the Caenorhabditis elegans α-glucosidase I gene (F13H10.4, designated agl-1) that encodes a polypeptide with 36% identity to human α-glucosidase I. The agl-1 cDNA restored the expression of complex-type N-glycans on the cell surface of α-glucosidase I-defective Chinese hamster ovary Lec23 cells. RNAi knockdown of agl-1 [agl-1(RNAi)] produced worms that were visibly similar to wild-type, but lifespan was reduced to about half of the control. Analyses of N-glycosylation in agl-1(RNAi) animals by western blotting and mass spectrometry showed reduction of paucimannose and complex-type glycans and dramatic increase of glucosylated oligomannose glycans. In addition, a significant amount of unusual terminally fucosylated N-glycans were found in agl-1(RNAi) animals. ER stress response was also provoked, leading to the accumulation of large amounts of triglucosylated free oligosaccharides (FOSs) (Glc3Man4-5GlcNAc1-2) in agl-1(RNAi) animals. Acceleration of ER-associated degradation in response to the accumulation of unfolded glycoproteins and insufficient interaction with calnexin/calreticulin in the ER lumen likely accounts for the increase of FOSs. Taken together, these studies in C. elegans demonstrate that decreased ER α-glucosidase I affects the entire N-glycan profile and induces chronic ER stress, which may contribute to the pathophysiology of CDG-IIb in humans.
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Affiliation(s)
- Toshihiko Katoh
- Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602-4712, USA
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17
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Murakami S, Takaoka Y, Ashida H, Yamamoto K, Narimatsu H, Chiba Y. Identification and characterization of endo-β-N-acetylglucosaminidase from methylotrophic yeast Ogataea minuta. Glycobiology 2013; 23:736-44. [PMID: 23436287 DOI: 10.1093/glycob/cwt012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
In four yeast strains, Ogataea minuta, Candida parapolymorpha, Pichia anomala and Zygosaccharomyces rouxii, we identified endo-β-N-acetylglucosaminidase (ENGase) homologous sequences by database searches; in each of the four species, a corresponding enzyme activity was also confirmed in crude cell extract obtained from each strain. The O. minuta ENGase (Endo-Om)-encoding gene was directly amplified from O. minuta genomic DNA and sequenced. The Endo-Om-encoding gene contained a 2319-bp open-reading frame; the deduced amino acid sequence indicated that the putative protein belonged to glycoside hydrolase family 85. The gene was introduced into O. minuta, and the recombinant Endo-Om was overexpressed and purified. When the enzyme assay was performed using an agalacto-biantennary oligosaccharide as a substrate, Endo-Om exhibited both hydrolysis and transglycosylation activities. Endo-Om exhibited hydrolytic activity for high-mannose, hybrid, biantennary and (2,6)-branched triantennary N-linked oligosaccharides, but not for tetraantennary, (2,4)-branched triantennary, bisecting N-acetylglucosamine structure and core-fucosylated biantennary N-linked oligosaccharides. Endo-Om also was able to hydrolyze N-glycans attached to RNase B and human transferrin under both denaturing and nondenaturing conditions. Thus, the present study reports the detection and characterization of a novel yeast ENGase.
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Affiliation(s)
- Satoshi Murakami
- Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba Central 6, 1-1-1 Higashi, Tsukuba 305-8566, Japan
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18
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Geyer H, Schmidt M, Müller M, Schnabel R, Geyer R. Mass spectrometric comparison of N-glycan profiles from Caenorhabditis elegans mutant embryos. Glycoconj J 2012; 29:135-45. [PMID: 22407488 DOI: 10.1007/s10719-012-9371-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 02/17/2012] [Accepted: 02/21/2012] [Indexed: 11/29/2022]
Abstract
The free-living nematode Caenorhabditis elegans is a well-characterized eukaryotic model organism. Recent glycomic analyses of the glycosylation potential of this worm revealed an extremely high structural variability of its N-glycans. Moreover, the glycan patterns of each developmental stage appeared to be unique. In this study we have determined the N-glycan profiles of wild-type embryos in comparison to mutant embryos arresting embryogenesis early before differentiation and causing extensive transformations of cell identities, which allows to follow the diversification of N-glycans during development using mass spectrometry. As a striking feature, wild-type embryos obtained from liquid culture expressed a less heterogeneous oligosaccharide pattern than embryos recovered from agar plates. N-glycan profiles of mutant embryos displayed, in part, distinct differences in comparison to wild-type embryos suggesting alterations in oligosaccharide trimming and processing, which may be linked to specific cell fate alterations in the embryos.
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Affiliation(s)
- Hildegard Geyer
- Institute of Biochemistry, Faculty of Medicine, University of Giessen, Friedrichstrasse 24, 35392, Giessen, Germany
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19
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Hirayama H, Suzuki T. Metabolism of free oligosaccharides is facilitated in the och1Δ mutant of Saccharomyces cerevisiae. Glycobiology 2011; 21:1341-8. [PMID: 21622726 DOI: 10.1093/glycob/cwr073] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In eukaryotic cells, it is known that N-glycans play a pivotal role in quality control of carrier proteins. Although "free" forms of oligosaccharides (fOSs) are known to be accumulated in the cytosol, the precise mechanism of their formation, degradation and biological relevance remains poorly understood. It has been shown that, in budding yeast, almost all fOSs are formed from misfolded glycoproteins. Precise structural analysis of fOSs revealed that several yeast fOSs bear a yeast-specific modification by Golgi-resident α-1,6-mannosyltransferase, Och1. In this study, structural diversity of fOSs in och1Δ cells was analyzed. To our surprise, several fOSs in och1Δ cells have unusual α-1,3-linked mannose residues at their non-reducing termini. These mannose residues were not observed in wild-type cells, suggesting that the addition of these unique mannoses occurred as a compensation of Och1 defect. A significant increase in the amount of fOSs modified by Golgi-localized mannosyltransferases was also observed in och1Δ cells. Moreover, the amount of processed fOSs and intracellular α-mannosidase (Ams1) both increased in this mutant. Up-regulation of Ams1 activity was also apparent for cells treated with cell wall perturbation reagent. These results provide an insight into a possible link between catabolism of fOSs and cell wall stress.
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Affiliation(s)
- Hiroto Hirayama
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako Saitama 351-0198, Japan
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Kato A, Wang L, Ishii K, Seino J, Asano N, Suzuki T. Calystegine B3 as a specific inhibitor for cytoplasmic alpha-mannosidase, Man2C1. J Biochem 2011; 149:415-22. [PMID: 21217149 DOI: 10.1093/jb/mvq153] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cytoplasmic α-mannosidase (Man2C1) has been implicated in non-lysosomal catabolism of free oligosaccharides derived from N-linked glycans accumulated in the cytosol. Suppression of Man2C1 expression reportedly induces apoptosis in various cell lines, but its molecular mechanism remains unclear. Development of a specific inhibitor for Man2C1 is critical to understanding its biological significance. In this study, we identified a plant-derived alkaloid, calystegine B(3), as a potent specific inhibitor for Man2C1 activity. Biochemical enzyme assay revealed that calystegine B(3) was a highly specific inhibitor for Man2C1 among various α-mannosidases prepared from rat liver. Consistent with this in vitro result, an in vivo experiment also showed that treatment of mammalian-derived cultured cells with this compound resulted in drastic change in both structure and quantity of free oligosaccharides in the cytosol, whereas no apparent change was seen in cell-surface oligosaccharides. Calystegine B(3) could thus serve as a potent tool for the development of a highly specific in vivo inhibitor for Man2C1.
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Affiliation(s)
- Atsushi Kato
- Department of Hospital Pharmacy, University of Toyama, Toyama 930-0194, Japan
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21
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Chantret I, Fasseu M, Zaoui K, Le Bizec C, Sadou Yayé H, Dupré T, Moore SEH. Identification of roles for peptide: N-glycanase and endo-beta-N-acetylglucosaminidase (Engase1p) during protein N-glycosylation in human HepG2 cells. PLoS One 2010; 5:e11734. [PMID: 20668520 PMCID: PMC2909182 DOI: 10.1371/journal.pone.0011734] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 06/04/2010] [Indexed: 11/29/2022] Open
Abstract
Background During mammalian protein N-glycosylation, 20% of all dolichol-linked oligosaccharides (LLO) appear as free oligosaccharides (fOS) bearing the di-N-acetylchitobiose (fOSGN2), or a single N-acetylglucosamine (fOSGN), moiety at their reducing termini. After sequential trimming by cytosolic endo β-N-acetylglucosaminidase (ENGase) and Man2c1 mannosidase, cytosolic fOS are transported into lysosomes. Why mammalian cells generate such large quantities of fOS remains unexplored, but fOSGN2 could be liberated from LLO by oligosaccharyltransferase, or from glycoproteins by NGLY1-encoded Peptide-N-Glycanase (PNGase). Also, in addition to converting fOSGN2 to fOSGN, the ENGASE-encoded cytosolic ENGase of poorly defined function could potentially deglycosylate glycoproteins. Here, the roles of Ngly1p and Engase1p during fOS metabolism were investigated in HepG2 cells. Methods/Principal Findings During metabolic radiolabeling and chase incubations, RNAi-mediated Engase1p down regulation delays fOSGN2-to-fOSGN conversion, and it is shown that Engase1p and Man2c1p are necessary for efficient clearance of cytosolic fOS into lysosomes. Saccharomyces cerevisiae does not possess ENGase activity and expression of human Engase1p in the png1Δ deletion mutant, in which fOS are reduced by over 98%, partially restored fOS generation. In metabolically radiolabeled HepG2 cells evidence was obtained for a small but significant Engase1p-mediated generation of fOS in 1 h chase but not 30 min pulse incubations. Ngly1p down regulation revealed an Ngly1p-independent fOSGN2 pool comprising mainly Man8GlcNAc2, corresponding to ∼70% of total fOS, and an Ngly1p-dependent fOSGN2 pool enriched in Glc1Man9GlcNAc2 and Man9GlcNAc2 that corresponds to ∼30% of total fOS. Conclusions/Significance As the generation of the bulk of fOS is unaffected by co-down regulation of Ngly1p and Engase1p, alternative quantitatively important mechanisms must underlie the liberation of these fOS from either LLO or glycoproteins during protein N-glycosylation. The fully mannosylated structures that occur in the Ngly1p-dependent fOSGN2 pool indicate an ERAD process that does not require N-glycan trimming.
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Affiliation(s)
- Isabelle Chantret
- INSERM, U773, Centre de Recherche Bichat Beaujon, Paris, France; Université Paris 7 Denis Diderot, site Bichat, Paris, France.
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Hirayama H, Seino J, Kitajima T, Jigami Y, Suzuki T. Free oligosaccharides to monitor glycoprotein endoplasmic reticulum-associated degradation in Saccharomyces cerevisiae. J Biol Chem 2010; 285:12390-404. [PMID: 20150426 DOI: 10.1074/jbc.m109.082081] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
In eukaryotic cells, N-glycosylation has been recognized as one of the most common and functionally important co- or post-translational modifications of proteins. "Free" forms of N-glycans accumulate in the cytosol of mammalian cells, but the precise mechanism for their formation and degradation remains unknown. Here, we report a method for the isolation of yeast free oligosaccharides (fOSs) using endo-beta-1,6-glucanase digestion. fOSs were undetectable in cells lacking PNG1, coding the cytoplasmic peptide:N-glycanase gene, suggesting that almost all fOSs were formed from misfolded glycoproteins by Png1p. Structural studies revealed that the most abundant fOS was M8B, which is not recognized well by the endoplasmic reticulum-associated degradation (ERAD)-related lectin, Yos9p. In addition, we provide evidence that some of the ERAD substrates reached the Golgi apparatus prior to retrotranslocation to the cytosol. N-Glycan structures on misfolded glycoproteins in cells lacking the cytosol/vacuole alpha-mannosidase, Ams1p, was still quite diverse, indicating that processing of N-glycans on misfolded glycoproteins was more complex than currently envisaged. Under ER stress, an increase in fOSs was observed, whereas levels of M7C, a key glycan structure recognized by Yos9p, were unchanged. Our method can thus provide valuable information on the molecular mechanism of glycoprotein ERAD in Saccharomyces cerevisiae.
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Affiliation(s)
- Hiroto Hirayama
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan
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23
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Umekawa M, Li C, Higashiyama T, Huang W, Ashida H, Yamamoto K, Wang LX. Efficient glycosynthase mutant derived from Mucor hiemalis endo-beta-N-acetylglucosaminidase capable of transferring oligosaccharide from both sugar oxazoline and natural N-glycan. J Biol Chem 2009; 285:511-21. [PMID: 19880511 DOI: 10.1074/jbc.m109.059832] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Endo-M, an endo-beta-N-acetylglucosaminidase from Mucor hiemalis, is a family 85 glycoside hydrolase. This enzyme is unique in that it can transfer en bloc the oligosaccharide of various types of N-glycans onto different acceptors, and thereby it enzymatically generates diverse glycoconjugates. In this study, we performed mutational and kinetic studies focusing on a key catalytic asparagine 175 of Endo-M. We have shown that most of the Asn-175 mutants had significantly diminished hydrolysis activity but acted as glycosynthases capable of using synthetic sugar oxazoline for transglycosylation. Our results confirm the critical role of this asparagine residue in promoting the formation of an oxazolinium ion intermediate in the first step of the substrate-assisted catalysis. Interestingly, the N175Q mutant was found to possess dramatically enhanced glycosynthase-like activity with sugar oxazoline in comparison with N175A and a transglycosidase-like activity with "natural" N-glycan as well. These results also implicated the significance of amide side chain in the asparagine 175 of Endo-M for promoting oxazoline transglycosylation in the second step of the catalysis. The highly efficient syntheses of glycopeptides/glycoproteins by N175Q combined with synthetic sugar oxazolines or natural N-glycan substrates were exemplified. In addition, we also identified several previously unknown residues that seem to play a role in the catalysis of Endo-M.
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Affiliation(s)
- Midori Umekawa
- Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan
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24
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Katoh T, Ashida H, Yamamoto K. Generation and Metabolism of Cytosolic Free Oligosaccharides in Caenorhabditis elegans. TRENDS GLYCOSCI GLYC 2009. [DOI: 10.4052/tigg.21.163] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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25
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Ashida H, Kato T, Kawahara A, Tanaka Y, Umekawa M, Yamamoto K. Enzymes Involved in Generation and Degradation of the Free Oligosaccharides in the Cytosol of Caenorhabditis elegans. J Appl Glycosci (1999) 2009. [DOI: 10.5458/jag.56.137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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26
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Funakoshi Y, Suzuki T. Glycobiology in the cytosol: the bitter side of a sweet world. Biochim Biophys Acta Gen Subj 2008; 1790:81-94. [PMID: 18952151 DOI: 10.1016/j.bbagen.2008.09.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2008] [Revised: 08/03/2008] [Accepted: 09/11/2008] [Indexed: 01/11/2023]
Abstract
Progress in glycobiology has undergone explosive growth over the past decade with more of the researchers now realizing the importance of glycan chains in various inter- and intracellular processes. However, there is still an area of glycobiology awaiting exploration. This is especially the case for the field of "glycobiology in the cytosol" which remains rather poorly understood. Yet evidence is accumulating to demonstrate that the glycoconjugates and their recognition molecules (i.e. lectins) are often present in this subcellular compartment.
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Affiliation(s)
- Yoko Funakoshi
- Glycometabolome Team, Systems Glycobiology Research Group, RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako Saitama, 351-0198, Japan
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27
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Suzuki T, Matsuo I, Totani K, Funayama S, Seino J, Taniguchi N, Ito Y, Hase S. Dual-gradient high-performance liquid chromatography for identification of cytosolic high-mannose-type free glycans. Anal Biochem 2008; 381:224-32. [PMID: 18656438 DOI: 10.1016/j.ab.2008.07.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 06/30/2008] [Accepted: 07/01/2008] [Indexed: 11/26/2022]
Abstract
It has been shown that free oligosaccharides derived from N-linked glycans accumulate in the cytosol of animal cells. Most of the glycans have only a single GlcNAc at their reducing termini (Gn1 glycans), whereas the original N-glycans retain N,N'-diacetylchitobiose at their reducing termini (Gn2 glycans). Under the conditions of high-performance liquid chromatography (HPLC) mapping established for pyridylamine (PA)-labeled Gn2 N-glycans, Gn1 glycans are not well retained on reversed-phase HPLC, making simultaneous analysis of Gn1 and Gn2 glycans problematic. We introduced a dual gradient (i.e., pH and butanol gradient) for the separation of Gn1 and Gn2 glycans in a single reversed-phase HPLC. Determination of elution time for various standard Gn2 high-mannose-type glycans, as well as Gn1 glycans found in the cytosol of animal cells, showed that elution of Gn1 and Gn2 glycans could be separated. Sufficient separation for most of the structural isomers could be achieved for Gn1 and Gn2 glycans. This HPLC, therefore, is a powerful method for identification of the structures of PA-labeled glycans, especially Gn1-type glycans, isolated from the cytosol of animal cells.
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Affiliation(s)
- Tadashi Suzuki
- RIKEN (Institute of Physical and Chemical Research), Wako, Saitama 351-0198, Japan.
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28
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Accumulation of free complex-type N-glycans in MKN7 and MKN45 stomach cancer cells. Biochem J 2008; 413:227-37. [DOI: 10.1042/bj20071562] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During the N-glycosylation reaction, it has been shown that ‘free’ N-glycans are generated either from lipid-linked oligosaccharides or from misfolded glycoproteins. In both cases, occurrence of high mannose-type free glycans is well-documented, and the molecular mechanism for their catabolism in the cytosol has been studied. On the other hand, little, if anything, is known with regard to the accumulation of more processed, complex-type free oligosaccharides in the cytosol of mammalian cells. During the course of comprehensive analysis of N-glycans in cancer cell membrane fractions [Naka et al. (2006) J. Proteome Res. 5, 88–97], we found that a significant amount of unusual, complex-type free N-glycans were accumulated in the stomach cancer-derived cell lines, MKN7 and MKN45. The most abundant and characteristic glycan found in these cells was determined to be NeuAcα2-6Galβ1-4GlcNAcβ1-2Manα1-3Manβ1-4GlcNAc. Biochemical analyses indicated that those glycans found were cytosolic glycans derived from lysosomes due to low integrity of the lysosomal membrane. Since the accumulation of these free N-glycans was specific to only two cell lines among the various cancer cell lines examined, these cytosolic N-glycans may serve as a specific biomarker for diagnosis of specific tumours. A cytosolic sialidase, Neu2, was shown to be involved in the degradation of these sialoglycans, indicating that the cytosol of mammalian cells might be equipped for metabolism of complex-type glycans.
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Glycoform analysis of Japanese cypress pollen allergen, Cha o 1: a comparison of the glycoforms of cedar and cypress pollen allergens. Biosci Biotechnol Biochem 2008; 72:485-91. [PMID: 18256506 DOI: 10.1271/bbb.70572] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A Japanese cypress (Chamaecyparis obtusa) pollen allergen, Cha o 1, is one of the major allergens that cause allergic pollinosis in Japan. Although it has been found that Cha o 1 is glycosylated and that the amino acid sequence is highly homologous with that of Japanese cedar pollen allergen (Cry j 1), the structure of N-glycans linked to Cha o 1 remains to be determined. In this study, therefore, we analyzed the structures of the N-glycans of Cha o1. The N-glycans were liberated by hydrazinolysis from purified Cha o 1, and the resulting sugar chains were N-acetylated and pyridylaminated. The structures of pyridylaminated N-glycans were analyzed by a combination of exoglycosidase digestion, two dimensional (2D-) sugar chain mapping, and electrospray ionization mass spectrometry analysis. Structural analysis indicated that the major N-glycan structure of Cha o1 is GlcNAc2Man3Xyl1Fuc1GlcNAc2 (89%), and that high-mannose type structures (Man9GlcNAc2, Man7GlcNAc2) occur as minor components (11%).
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30
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Chantret I, Moore SEH. Free oligosaccharide regulation during mammalian protein N-glycosylation. Glycobiology 2007; 18:210-24. [DOI: 10.1093/glycob/cwn003] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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31
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Suzuki T. Cytoplasmic peptide:N-glycanase and catabolic pathway for free N-glycans in the cytosol. Semin Cell Dev Biol 2007; 18:762-9. [DOI: 10.1016/j.semcdb.2007.09.010] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 08/07/2007] [Accepted: 09/05/2007] [Indexed: 10/22/2022]
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