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Kim Y, Li H, Choi J, Boo J, Jo H, Hyun JY, Shin I. Glycosidase-targeting small molecules for biological and therapeutic applications. Chem Soc Rev 2023; 52:7036-7070. [PMID: 37671645 DOI: 10.1039/d3cs00032j] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Glycosidases are ubiquitous enzymes that catalyze the hydrolysis of glycosidic linkages in oligosaccharides and glycoconjugates. These enzymes play a vital role in a wide variety of biological events, such as digestion of nutritional carbohydrates, lysosomal catabolism of glycoconjugates, and posttranslational modifications of glycoproteins. Abnormal glycosidase activities are associated with a variety of diseases, particularly cancer and lysosomal storage disorders. Owing to the physiological and pathological significance of glycosidases, the development of small molecules that target these enzymes is an active area in glycoscience and medicinal chemistry. Research efforts carried out thus far have led to the discovery of numerous glycosidase-targeting small molecules that have been utilized to elucidate biological processes as well as to develop effective chemotherapeutic agents. In this review, we describe the results of research studies reported since 2018, giving particular emphasis to the use of fluorescent probes for detection and imaging of glycosidases, activity-based probes for covalent labelling of these enzymes, glycosidase inhibitors, and glycosidase-activatable prodrugs.
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Affiliation(s)
- Yujun Kim
- Department of Chemistry, Yonsei University, 03722 Seoul, Republic of Korea.
| | - Hui Li
- Department of Chemistry, Yonsei University, 03722 Seoul, Republic of Korea.
| | - Joohee Choi
- Department of Chemistry, Yonsei University, 03722 Seoul, Republic of Korea.
| | - Jihyeon Boo
- Department of Chemistry, Yonsei University, 03722 Seoul, Republic of Korea.
| | - Hyemi Jo
- Department of Chemistry, Yonsei University, 03722 Seoul, Republic of Korea.
- Department of Drug Discovery, Data Convergence Drug Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Republic of Korea.
| | - Ji Young Hyun
- Department of Drug Discovery, Data Convergence Drug Research Center, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Republic of Korea.
| | - Injae Shin
- Department of Chemistry, Yonsei University, 03722 Seoul, Republic of Korea.
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2
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Wannitikul P, Wattana-Amorn P, Sathitnaitham S, Sakulkoo J, Suttangkakul A, Wonnapinij P, Bassel GW, Simister R, Gomez LD, Vuttipongchaikij S. Disruption of a DUF247 Containing Protein Alters Cell Wall Polysaccharides and Reduces Growth in Arabidopsis. PLANTS (BASEL, SWITZERLAND) 2023; 12:1977. [PMID: 37653894 PMCID: PMC10221614 DOI: 10.3390/plants12101977] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Revised: 05/09/2023] [Accepted: 05/10/2023] [Indexed: 09/02/2023]
Abstract
Plant cell wall biosynthesis is a complex process that requires proteins and enzymes from glycan synthesis to wall assembly. We show that disruption of At3g50120 (DUF247-1), a member of the DUF247 multigene family containing 28 genes in Arabidopsis, results in alterations to the structure and composition of cell wall polysaccharides and reduced growth and plant size. An ELISA using cell wall antibodies shows that the mutants also exhibit ~50% reductions in xyloglucan (XyG), glucuronoxylan (GX) and heteromannan (HM) epitopes in the NaOH fraction and ~50% increases in homogalacturonan (HG) epitopes in the CDTA fraction. Furthermore, the polymer sizes of XyGs and GXs are reduced with concomitant increases in short-chain polymers, while those of HGs and mHGs are slightly increased. Complementation using 35S:DUF247-1 partially recovers the XyG and HG content, but not those of GX and HM, suggesting that DUF247-1 is more closely associated with XyGs and HGs. DUF247-1 is expressed throughout Arabidopsis, particularly in vascular and developing tissues, and its disruption affects the expression of other gene members, indicating a regulatory control role within the gene family. Our results demonstrate that DUF247-1 is required for normal cell wall composition and structure and Arabidopsis growth.
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Affiliation(s)
- Pitchaporn Wannitikul
- Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand; (P.W.); (S.S.); (J.S.); (A.S.); (P.W.)
| | - Pakorn Wattana-Amorn
- Special Research Unit for Advanced Magnetic Resonance and Center of Excellence for Innovation in Chemistry, Department of Chemistry, Faculty of Science, Kasetsart University, Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand;
| | - Sukhita Sathitnaitham
- Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand; (P.W.); (S.S.); (J.S.); (A.S.); (P.W.)
| | - Jenjira Sakulkoo
- Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand; (P.W.); (S.S.); (J.S.); (A.S.); (P.W.)
| | - Anongpat Suttangkakul
- Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand; (P.W.); (S.S.); (J.S.); (A.S.); (P.W.)
- Center of Advanced studies for Tropical Natural Resources, Kasetsart University, Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand
| | - Passorn Wonnapinij
- Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand; (P.W.); (S.S.); (J.S.); (A.S.); (P.W.)
- Center of Advanced studies for Tropical Natural Resources, Kasetsart University, Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand
- Omics Center for Agriculture, Bioresources, Food and Health, Kasetsart University (OmiKU), Bangkok 10900, Thailand
| | - George W. Bassel
- School of Life Sciences, The University of Warwick, Coventry CV4 7AL, UK;
| | - Rachael Simister
- CNAP, Department of Biology, University of York, Heslington, York YO10 5DD, UK; (R.S.); (L.D.G.)
| | - Leonardo D. Gomez
- CNAP, Department of Biology, University of York, Heslington, York YO10 5DD, UK; (R.S.); (L.D.G.)
| | - Supachai Vuttipongchaikij
- Department of Genetics, Faculty of Science, Kasetsart University, 50 Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand; (P.W.); (S.S.); (J.S.); (A.S.); (P.W.)
- Center of Advanced studies for Tropical Natural Resources, Kasetsart University, Ngam Wong Wan Road, Chattuchak, Bangkok 10900, Thailand
- Omics Center for Agriculture, Bioresources, Food and Health, Kasetsart University (OmiKU), Bangkok 10900, Thailand
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3
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Morikawa C, Sugiura K, Kondo K, Yamamoto Y, Kojima Y, Ozawa Y, Yoshioka H, Miura N, Piao J, Okada K, Hanamatsu H, Tsuda M, Tanaka S, Furukawa JI, Shinohara Y. Evaluation of the context of downstream N- and free N-glycomic alterations induced by swainsonine in HepG2 cells. Biochim Biophys Acta Gen Subj 2022; 1866:130168. [PMID: 35594965 DOI: 10.1016/j.bbagen.2022.130168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 04/27/2022] [Accepted: 05/02/2022] [Indexed: 11/27/2022]
Abstract
Swainsonine (SWA), a potent inhibitor of class II α-mannosidases, is present in a number of plant species worldwide and causes severe toxicosis in livestock grazing these plants. The mechanisms underlying SWA-induced animal poisoning are not fully understood. In this study, we analyzed the alterations that occur in N- and free N-glycomic upon addition of SWA to HepG2 cells to understand better SWA-induced glycomic alterations. After SWA addition, we observed the appearance of SWA-specific glycomic alterations, such as unique fucosylated hybrid-type and fucosylated M5 (M5F) N-glycans, and a remarkable increase in all classes of Gn1 FNGs. Further analysis of the context of these glycomic alterations showed that (fucosylated) hybrid type N-glycans were not the precursors of these Gn1 FNGs and vice versa. Time course analysis revealed the dynamic nature of glycomic alterations upon exposure of SWA and suggested that accumulation of free N-glycans occurred earlier than that of hybrid-type N-glycans. Hybrid-type N-glycans, of which most were uniquely core fucosylated, tended to increase slowly over time, as was observed for M5F N-glycans. Inhibition of swainsonine-induced unique fucosylation of hybrid N-glycans and M5 by coaddition of 2-fluorofucose caused significant increases in paucimannose- and fucosylated paucimannose-type N-glycans, as well as paucimannose-type free N-glycans. The results not only revealed the gross glycomic alterations in HepG2 cells induced by swainsonine, but also provide information on the global interrelationships between glycomic alterations.
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Affiliation(s)
- Chie Morikawa
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Kanako Sugiura
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Keina Kondo
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Yurie Yamamoto
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Yuma Kojima
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Yurika Ozawa
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Hiroki Yoshioka
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan
| | - Nobuaki Miura
- Division of Bioinformatics, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Chuo-ku, Niigata 951-8514, Japan
| | - Jinhua Piao
- Department of Advanced Clinical Glycobiology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita21, Nishi11, Kita-ku, Sapporo 001-0021, Japan
| | - Kazue Okada
- Department of Advanced Clinical Glycobiology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita21, Nishi11, Kita-ku, Sapporo 001-0021, Japan
| | - Hisatoshi Hanamatsu
- Department of Advanced Clinical Glycobiology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita21, Nishi11, Kita-ku, Sapporo 001-0021, Japan
| | - Masumi Tsuda
- Department of Cancer Pathology, Faculty of Medicine, Hokkaido University, Sapporo, Japan; Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan
| | - Shinya Tanaka
- Department of Cancer Pathology, Faculty of Medicine, Hokkaido University, Sapporo, Japan; Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Japan
| | - Jun-Ichi Furukawa
- Department of Advanced Clinical Glycobiology, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Kita21, Nishi11, Kita-ku, Sapporo 001-0021, Japan
| | - Yasuro Shinohara
- Department of Pharmacy, Kinjo Gakuin University, Nagoya 463-8521, Japan.
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Bakshi T, Pham D, Kaur R, Sun B. Hidden Relationships between N-Glycosylation and Disulfide Bonds in Individual Proteins. Int J Mol Sci 2022; 23:ijms23073742. [PMID: 35409101 PMCID: PMC8998389 DOI: 10.3390/ijms23073742] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 03/25/2022] [Accepted: 03/28/2022] [Indexed: 02/04/2023] Open
Abstract
N-Glycosylation (NG) and disulfide bonds (DBs) are two prevalent co/post-translational modifications (PTMs) that are often conserved and coexist in membrane and secreted proteins involved in a large number of diseases. Both in the past and in recent times, the enzymes and chaperones regulating these PTMs have been constantly discovered to directly interact with each other or colocalize in the ER. However, beyond a few model proteins, how such cooperation affects N-glycan modification and disulfide bonding at selective sites in individual proteins is largely unknown. Here, we reviewed the literature to discover the current status in understanding the relationships between NG and DBs in individual proteins. Our results showed that more than 2700 human proteins carry both PTMs, and fewer than 2% of them have been investigated in the associations between NG and DBs. We summarized both these proteins with the reported relationships in the two PTMs and the tools used to discover the relationships. We hope that, by exposing this largely understudied field, more investigations can be encouraged to unveil the hidden relationships of NG and DBs in the majority of membranes and secreted proteins for pathophysiological understanding and biotherapeutic development.
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Affiliation(s)
- Tania Bakshi
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada;
| | - David Pham
- Department of Computing Science, Simon Fraser University, Burnaby, BC V5A 1S6, Canada;
| | - Raminderjeet Kaur
- Faculty of Health Science, Simon Fraser University, Burnaby, BC V5A 1S6, Canada;
| | - Bingyun Sun
- Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada;
- Department of Chemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada
- Correspondence:
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Identification of difructose dianhydride I synthase/hydrolase from an oral bacterium establishes a novel glycoside hydrolase family. J Biol Chem 2021; 297:101324. [PMID: 34688653 PMCID: PMC8605356 DOI: 10.1016/j.jbc.2021.101324] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 10/07/2021] [Accepted: 10/07/2021] [Indexed: 11/30/2022] Open
Abstract
Fructooligosaccharides and their anhydrides are widely used as health-promoting foods and prebiotics. Various enzymes acting on β-D-fructofuranosyl linkages of natural fructan polymers have been used to produce functional compounds. However, enzymes that hydrolyze and form α-D-fructofuranosyl linkages have been less studied. Here, we identified the BBDE_2040 gene product from Bifidobacterium dentium (α-D-fructofuranosidase and difructose dianhydride I synthase/hydrolase from Bifidobacterium dentium [αFFase1]) as an enzyme with α-D-fructofuranosidase and α-D-arabinofuranosidase activities and an anomer-retaining manner. αFFase1 is not homologous with any known enzymes, suggesting that it is a member of a novel glycoside hydrolase family. When caramelized fructose sugar was incubated with αFFase1, conversions of β-D-Frup-(2→1)-α-D-Fruf to α-D-Fruf-1,2′:2,1′-β-D-Frup (diheterolevulosan II) and β-D-Fruf-(2→1)-α-D-Fruf (inulobiose) to α-D-Fruf-1,2′:2,1′-β-D-Fruf (difructose dianhydride I [DFA I]) were observed. The reaction equilibrium between inulobiose and DFA I was biased toward the latter (1:9) to promote the intramolecular dehydrating condensation reaction. Thus, we named this enzyme DFA I synthase/hydrolase. The crystal structures of αFFase1 in complex with β-D-Fruf and β-D-Araf were determined at the resolutions of up to 1.76 Å. Modeling of a DFA I molecule in the active site and mutational analysis also identified critical residues for catalysis and substrate binding. The hexameric structure of αFFase1 revealed the connection of the catalytic pocket to a large internal cavity via a channel. Molecular dynamics analysis implied stable binding of DFA I and inulobiose to the active site with surrounding water molecules. Taken together, these results establish DFA I synthase/hydrolase as a member of a new glycoside hydrolase family (GH172).
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Ninagawa S. N-glycan Dependent Protein Quality Control System in the Endoplasmic Reticulum. TRENDS GLYCOSCI GLYC 2021. [DOI: 10.4052/tigg.2108.2e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Satoshi Ninagawa
- Department of Biophysics, Graduate School of Science, Kyoto University
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Ninagawa S. N-glycan Dependent Protein Quality Control System in the Endoplasmic Reticulum. TRENDS GLYCOSCI GLYC 2021. [DOI: 10.4052/tigg.2108.2j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Satoshi Ninagawa
- Department of Biophysics, Graduate School of Science, Kyoto University
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8
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Mathew C, Weiß RG, Giese C, Lin CW, Losfeld ME, Glockshuber R, Riniker S, Aebi M. Glycan-protein interactions determine kinetics of N-glycan remodeling. RSC Chem Biol 2021; 2:917-931. [PMID: 34212152 PMCID: PMC8207518 DOI: 10.1039/d1cb00019e] [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] [Indexed: 12/12/2022] Open
Abstract
A hallmark of N-linked glycosylation in the secretory compartments of eukaryotic cells is the sequential remodeling of an initially uniform oligosaccharide to a site-specific, heterogeneous ensemble of glycostructures on mature proteins. To understand site-specific processing, we used protein disulfide isomerase (PDI), a model protein with five glycosylation sites, for molecular dynamics (MD) simulations and compared the result to a biochemical in vitro analysis with four different glycan processing enzymes. As predicted by an analysis of the accessibility of the N-glycans for their processing enzymes derived from the MD simulations, N-glycans at different glycosylation sites showed different kinetic properties for the processing enzymes. In addition, altering the tertiary structure of the glycoprotein PDI affected its N-glycan remodeling in a site-specific way. We propose that the observed differential N-glycan reactivities depend on the surrounding protein tertiary structure and lead to different glycan structures in the same protein through kinetically controlled processing pathways. Atomistic glycoprotein simulations reveal a site-specific availability of glycan substrates in time-resolved mass spectrometry of maturating enzyme kinetics.![]()
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Affiliation(s)
- Corina Mathew
- Institute of Microbiology, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
| | - R Gregor Weiß
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
| | - Christoph Giese
- Institute of Molecular Biology & Biophysics, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
| | - Chia-Wei Lin
- Institute of Microbiology, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland .,Functional Genomics Center Zürich 8057 Zürich Switzerland
| | - Marie-Estelle Losfeld
- Institute of Microbiology, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
| | - Rudi Glockshuber
- Institute of Molecular Biology & Biophysics, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
| | - Sereina Riniker
- Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
| | - Markus Aebi
- Institute of Microbiology, Department of Biology, Swiss Federal Institute of Technology, ETH Zürich 8093 Zürich Switzerland
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Thines L, Stribny J, Morsomme P. From the Uncharacterized Protein Family 0016 to the GDT1 family: Molecular insights into a newly-characterized family of cation secondary transporters. MICROBIAL CELL 2020; 7:202-214. [PMID: 32743000 PMCID: PMC7380456 DOI: 10.15698/mic2020.08.725] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The Uncharacterized Protein Family 0016 (UPF0016) gathers poorly studied membrane proteins well conserved through evolution that possess one or two copies of the consensus motif Glu-x-Gly-Asp-(Arg/Lys)-(Ser/Thr). Members are found in many eukaryotes, bacteria and archaea. The interest for this protein family arose in 2012 when its human member TMEM165 was linked to the occurrence of Congenital Disorders of Glycosylation (CDGs) when harbouring specific mutations. Study of the UPF0016 family is undergone through the characterization of the bacterium Vibrio cholerae (MneA), cyanobacterium Synechocystis (SynPAM71), yeast Saccharomyces cerevisiae (Gdt1p), plant Arabidopsis thaliana (PAM71 and CMT1), and human (TMEM165) members. These proteins have all been identified as transporters of cations, more precisely of Mn2+, with an extra reported function in Ca2+ and/or H+ transport for some of them. Apart from glycosylation in humans, the UPF0016 members are required for lactation in humans, photosynthesis in plants and cyanobacteria, Ca2+ signaling in yeast, and Mn2+ homeostasis in the five aforementioned species. The requirement of the UPF0016 members for key physiological processes most likely derives from their transport activity at the Golgi membrane in human and yeast, the chloroplasts membranes in plants, the thylakoid and plasma membranes in cyanobacteria, and the cell membrane in bacteria. In the light of these studies on various UPF0016 members, this family is not considered as uncharacterized anymore and has been renamed the Gdt1 family according to the name of its S. cerevisiae member. This review aims at assembling and confronting the current knowledge in order to identify shared and distinct features in terms of transported molecules, mode of action, structure, etc., as well as to better understand their corresponding physiological roles.
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Affiliation(s)
- Louise Thines
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Jiri Stribny
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
| | - Pierre Morsomme
- Louvain Institute of Biomolecular Science and Technology, UCLouvain, Louvain-la-Neuve, Belgium
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Zhang J, Wu J, Liu L, Li J. The Crucial Role of Demannosylating Asparagine-Linked Glycans in ERADicating Misfolded Glycoproteins in the Endoplasmic Reticulum. FRONTIERS IN PLANT SCIENCE 2020; 11:625033. [PMID: 33510762 PMCID: PMC7835635 DOI: 10.3389/fpls.2020.625033] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 12/08/2020] [Indexed: 05/04/2023]
Abstract
Most membrane and secreted proteins are glycosylated on certain asparagine (N) residues in the endoplasmic reticulum (ER), which is crucial for their correct folding and function. Protein folding is a fundamentally inefficient and error-prone process that can be easily interfered by genetic mutations, stochastic cellular events, and environmental stresses. Because misfolded proteins not only lead to functional deficiency but also produce gain-of-function cellular toxicity, eukaryotic organisms have evolved highly conserved ER-mediated protein quality control (ERQC) mechanisms to monitor protein folding, retain and repair incompletely folded or misfolded proteins, or remove terminally misfolded proteins via a unique ER-associated degradation (ERAD) mechanism. A crucial event that terminates futile refolding attempts of a misfolded glycoprotein and diverts it into the ERAD pathway is executed by removal of certain terminal α1,2-mannose (Man) residues of their N-glycans. Earlier studies were centered around an ER-type α1,2-mannosidase that specifically cleaves the terminal α1,2Man residue from the B-branch of the three-branched N-linked Man9GlcNAc2 (GlcNAc for N-acetylglucosamine) glycan, but recent investigations revealed that the signal that marks a terminally misfolded glycoprotein for ERAD is an N-glycan with an exposed α1,6Man residue generated by members of a unique folding-sensitive α1,2-mannosidase family known as ER-degradation enhancing α-mannosidase-like proteins (EDEMs). This review provides a historical recount of major discoveries that led to our current understanding on the role of demannosylating N-glycans in sentencing irreparable misfolded glycoproteins into ERAD. It also discusses conserved and distinct features of the demannosylation processes of the ERAD systems of yeast, mammals, and plants.
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Affiliation(s)
- Jianjun Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Jiarui Wu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Linchuan Liu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
| | - Jianming Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou, China
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, United States
- *Correspondence: Jianming Li, ;
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Tax G, Lia A, Santino A, Roversi P. Modulation of ERQC and ERAD: A Broad-Spectrum Spanner in the Works of Cancer Cells? JOURNAL OF ONCOLOGY 2019; 2019:8384913. [PMID: 31662755 PMCID: PMC6791201 DOI: 10.1155/2019/8384913] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Accepted: 08/27/2019] [Indexed: 12/21/2022]
Abstract
Endoplasmic reticulum glycoprotein folding quality control (ERQC) and ER-associated degradation (ERAD) preside over cellular glycoprotein secretion and maintain steady glycoproteostasis. When cells turn malignant, cancer cell plasticity is affected and supported either by point mutations, preferential isoform selection, altered expression levels, or shifts to conformational equilibria of a secreted glycoprotein. Such changes are crucial in mediating altered extracellular signalling, metabolic behavior, and adhesion properties of cancer cells. It is therefore conceivable that interference with ERQC and/or ERAD can be used to selectively damage cancers. Indeed, inhibitors of the late stages of ERAD are already in the clinic against cancers such as multiple myeloma. Here, we review recent advances in our understanding of the complex relationship between glycoproteostasis and cancer biology and discuss the potential of ERQC and ERAD modulators for the selective targeting of cancer cell plasticity.
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Affiliation(s)
- Gábor Tax
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7RH, UK
| | - Andrea Lia
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7RH, UK
- Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
| | - Angelo Santino
- Institute of Sciences of Food Production, C.N.R. Unit of Lecce, via Monteroni, I-73100 Lecce, Italy
| | - Pietro Roversi
- Leicester Institute of Structural and Chemical Biology, Department of Molecular and Cell Biology, University of Leicester, Henry Wellcome Building, Lancaster Road, Leicester LE1 7RH, UK
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Lamriben L, Oster ME, Tamura T, Tian W, Yang Z, Clausen H, Hebert DN. EDEM1's mannosidase-like domain binds ERAD client proteins in a redox-sensitive manner and possesses catalytic activity. J Biol Chem 2018; 293:13932-13945. [PMID: 30021839 DOI: 10.1074/jbc.ra118.004183] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 06/26/2018] [Indexed: 11/06/2022] Open
Abstract
Endoplasmic reticulum (ER) degradation-enhancing α-mannosidase-like 1 protein (EDEM1) is a protein quality control factor that was initially proposed to recognize N-linked glycans on misfolded proteins through its mannosidase-like domain (MLD). However, recent studies have demonstrated that EDEM1 binds to some misfolded proteins in a glycan-independent manner, suggesting a more complex binding landscape for EDEM1. In this study, we have identified a thiol-dependent substrate interaction between EDEM1 and the α1-antitrypsin ER-associated protein degradation (ERAD) clients Z and NHK, specifically through the single Cys residue on Z/NHK (Cys256), required for binding under stringent detergent conditions. In addition to the thiol-dependent interaction, the presence of weaker protein-protein interactions was confirmed, suggestive of bipartite client-binding properties. About four reactive thiols on EDEM1 were identified and were not directly responsible for the observed redox-sensitive binding by EDEM1. Moreover, a protein construct comprising the EDEM1 MLD had thiol-dependent binding properties along with its active glycan-trimming activities. Lastly, we identified an additional intrinsically disordered region (IDR) located at the C terminus of EDEM1 in addition to its previously identified N-terminal IDR. We also determined that both IDRs are required for binding to the ERAD component ERdj5 as an interaction with ERdj5 was not observed with the MLD alone. Together, our findings indicate that EDEM1 employs different binding modalities to interact with ERAD clients and ER quality control (ERQC) machinery partners and that some of these properties are shared with its homologues EDEM2 and EDEM3.
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Affiliation(s)
- Lydia Lamriben
- From the Department of Biochemistry and Molecular Biology and.,Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003 and
| | - Michela E Oster
- From the Department of Biochemistry and Molecular Biology and
| | - Taku Tamura
- From the Department of Biochemistry and Molecular Biology and
| | - Weihua Tian
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Zhang Yang
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Henrik Clausen
- Copenhagen Center for Glycomics, Department of Cellular and Molecular Medicine, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark
| | - Daniel N Hebert
- From the Department of Biochemistry and Molecular Biology and .,Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003 and
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Thines L, Deschamps A, Sengottaiyan P, Savel O, Stribny J, Morsomme P. The yeast protein Gdt1p transports Mn 2+ ions and thereby regulates manganese homeostasis in the Golgi. J Biol Chem 2018; 293:8048-8055. [PMID: 29632074 DOI: 10.1074/jbc.ra118.002324] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 04/05/2018] [Indexed: 11/06/2022] Open
Abstract
The uncharacterized protein family 0016 (UPF0016) is a family of secondary ion transporters implicated in calcium homeostasis and some diseases. More precisely, genetic variants of the human UPF0016 ortholog transmembrane protein 165 (TMEM165) have been linked to congenital disorders of glycosylation (CDG). The Saccharomyces cerevisiae ortholog Gdt1p has been shown to be involved in calcium homeostasis and protein glycosylation. Moreover, plant and bacterial UPF0016 members appear to have putative roles in Mn2+ homeostasis. Here, we produced the yeast UPF0016 member Gdt1p in the bacterial host Lactococcus lactis Using Mn2+-induced quenching of Fura-2-emitted fluorescence, we observed that Gdt1p mediates Mn2+ influx, in addition to its previously reported regulation of Ca2+ influx. The estimated Km values of Gdt1p of 15.6 ± 2.6 μm for Ca2+ and 83.2 ± 9.8 μm for Mn2+ indicated that Gdt1p has a higher affinity for Ca2+ than for Mn2+ In yeast cells, we found that Gdt1p is involved in the resistance to high Mn2+ concentration and controls total Mn2+ stores. Lastly, we demonstrated that GDT1 deletion affects the activity of the yeast Mn2+-dependent Sod2p superoxide dismutase, most likely by modulating cytosolic Mn2+ concentrations. Taken together, we obtained first evidence that Gdt1p from yeast directly transports manganese, which strongly reinforces the suggested link between the UPF0016 family and Mn2+ homeostasis and provides new insights into the molecular causes of human TMEM165-associated CDGs. Our results also shed light on how yeast cells may regulate Golgi intraluminal concentrations of manganese, a key cofactor of many enzymes involved in protein glycosylation.
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Affiliation(s)
- Louise Thines
- Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Antoine Deschamps
- Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Palanivelu Sengottaiyan
- Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Oksana Savel
- Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Jiri Stribny
- Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium
| | - Pierre Morsomme
- Institut des Sciences de la Vie, Université catholique de Louvain, B-1348 Louvain-la-Neuve, Belgium.
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14
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Sato M, Liebschner D, Yamada Y, Matsugaki N, Arakawa T, Wills SS, Hattie M, Stubbs KA, Ito T, Senda T, Ashida H, Fushinobu S. The first crystal structure of a family 129 glycoside hydrolase from a probiotic bacterium reveals critical residues and metal cofactors. J Biol Chem 2017; 292:12126-12138. [PMID: 28546425 DOI: 10.1074/jbc.m117.777391] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 05/22/2017] [Indexed: 11/06/2022] Open
Abstract
The α-N-acetylgalactosaminidase from the probiotic bacterium Bifidobacterium bifidum (NagBb) belongs to the glycoside hydrolase family 129 and hydrolyzes the glycosidic bond of Tn-antigen (GalNAcα1-Ser/Thr). NagBb is involved in assimilation of O-glycans on mucin glycoproteins by B. bifidum in the human gastrointestinal tract, but its catalytic mechanism has remained elusive because of a lack of sequence homology around putative catalytic residues and of other structural information. Here we report the X-ray crystal structure of NagBb, representing the first GH129 family structure, solved by the single-wavelength anomalous dispersion method based on sulfur atoms of the native protein. We determined ligand-free, GalNAc, and inhibitor complex forms of NagBb and found that Asp-435 and Glu-478 are located in the catalytic domain at appropriate positions for direct nucleophilic attack at the anomeric carbon and proton donation for the glycosidic bond oxygen, respectively. A highly conserved Asp-330 forms a hydrogen bond with the O4 hydroxyl of GalNAc in the -1 subsite, and Trp-398 provides a stacking platform for the GalNAc pyranose ring. Interestingly, a metal ion, presumably Ca2+, is involved in the recognition of the GalNAc N-acetyl group. Mutations at Asp-435, Glu-478, Asp-330, and Trp-398 and residues involved in metal coordination (including an all-Ala quadruple mutant) significantly reduced the activity, indicating that these residues and the metal ion play important roles in substrate recognition and catalysis. Interestingly, NagBb exhibited some structural similarities to the GH101 endo-α-N-acetylgalactosaminidases, but several critical differences in substrate recognition and reaction mechanism account for the different activities of these two enzymes.
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Affiliation(s)
- Mayo Sato
- Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Dorothee Liebschner
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Yusuke Yamada
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Naohiro Matsugaki
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Takatoshi Arakawa
- Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Siobhán S Wills
- School of Molecular Sciences, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Mitchell Hattie
- School of Molecular Sciences, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Keith A Stubbs
- School of Molecular Sciences, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Tasuku Ito
- Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Toshiya Senda
- Structural Biology Research Center, Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba 305-0801, Japan
| | - Hisashi Ashida
- Faculty of Biology-Oriented Science and Technology, Kindai University, 930 Nishimitani, Kinokawa-shi, Wakayama 649-6493, Japan
| | - Shinya Fushinobu
- Department of Biotechnology, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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15
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Substrate recognition and catalysis by GH47 α-mannosidases involved in Asn-linked glycan maturation in the mammalian secretory pathway. Proc Natl Acad Sci U S A 2016; 113:E7890-E7899. [PMID: 27856750 DOI: 10.1073/pnas.1611213113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Maturation of Asn-linked oligosaccharides in the eukaryotic secretory pathway requires the trimming of nascent glycan chains to remove all glucose and several mannose residues before extension into complex-type structures on the cell surface and secreted glycoproteins. Multiple glycoside hydrolase family 47 (GH47) α-mannosidases, including endoplasmic reticulum (ER) α-mannosidase I (ERManI) and Golgi α-mannosidase IA (GMIA), are responsible for cleavage of terminal α1,2-linked mannose residues to produce uniquely trimmed oligomannose isomers that are necessary for ER glycoprotein quality control and glycan maturation. ERManI and GMIA have similar catalytic domain structures, but each enzyme cleaves distinct residues from tribranched oligomannose glycan substrates. The structural basis for branch-specific cleavage by ERManI and GMIA was explored by replacing an essential enzyme-bound Ca2+ ion with a lanthanum (La3+) ion. This ion swap led to enzyme inactivation while retaining high-affinity substrate interactions. Cocrystallization of La3+-bound enzymes with Man9GlcNAc2 substrate analogs revealed enzyme-substrate complexes with distinct modes of glycan branch insertion into the respective enzyme active-site clefts. Both enzymes had glycan interactions that extended across the entire glycan structure, but each enzyme engaged a different glycan branch and used different sets of glycan interactions. Additional mutagenesis and time-course studies of glycan cleavage probed the structural basis of enzyme specificity. The results provide insights into the enzyme catalytic mechanisms and reveal structural snapshots of the sequential glycan cleavage events. The data also indicate that full steric access to glycan substrates determines the efficiency of mannose-trimming reactions that control the conversion to complex-type structures in mammalian cells.
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16
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Quality control of glycoprotein folding and ERAD: the role of N-glycan handling, EDEM1 and OS-9. Histochem Cell Biol 2016; 147:269-284. [DOI: 10.1007/s00418-016-1513-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/20/2016] [Indexed: 02/03/2023]
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17
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Htm1p-Pdi1p is a folding-sensitive mannosidase that marks N-glycoproteins for ER-associated protein degradation. Proc Natl Acad Sci U S A 2016; 113:E4015-24. [PMID: 27357682 DOI: 10.1073/pnas.1608795113] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Our understanding of how the endoplasmic reticulum (ER)-associated protein degradation (ERAD) machinery efficiently targets terminally misfolded proteins while avoiding the misidentification of nascent polypeptides and correctly folded proteins is limited. For luminal N-glycoproteins, demannosylation of their N-glycan to expose a terminal α1,6-linked mannose is necessary for their degradation via ERAD, but whether this modification is specific to misfolded proteins is unknown. Here we report that the complex of the mannosidase Htm1p and the protein disulfide isomerase Pdi1p (Htm1p-Pdi1p) acts as a folding-sensitive mannosidase for catalyzing this first committed step in Saccharomyces cerevisiae We reconstitute this step in vitro with Htm1p-Pdi1p and model glycoprotein substrates whose structural states we can manipulate. We find that Htm1p-Pdi1p is a glycoprotein-specific mannosidase that preferentially targets nonnative glycoproteins trapped in partially structured states. As such, Htm1p-Pdi1p is suited to act as a licensing factor that monitors folding in the ER lumen and preferentially commits glycoproteins trapped in partially structured states for degradation.
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18
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Hang I, Lin CW, Grant OC, Fleurkens S, Villiger TK, Soos M, Morbidelli M, Woods RJ, Gauss R, Aebi M. Analysis of site-specific N-glycan remodeling in the endoplasmic reticulum and the Golgi. Glycobiology 2015; 25:1335-49. [PMID: 26240167 PMCID: PMC4634314 DOI: 10.1093/glycob/cwv058] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 07/14/2015] [Accepted: 07/27/2015] [Indexed: 11/14/2022] Open
Abstract
The hallmark of N-linked protein glycosylation is the generation of diverse glycan structures in the secretory pathway. Dynamic, non-template-driven processes of N-glycan remodeling in the endoplasmic reticulum and the Golgi provide the cellular setting for structural diversity. We applied newly developed mass spectrometry-based analytics to quantify site-specific N-glycan remodeling of the model protein Pdi1p expressed in insect cells. Molecular dynamics simulation, mutational analysis, kinetic studies of in vitro processing events and glycan flux analysis supported the defining role of the protein in N-glycan processing.
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Affiliation(s)
- Ivan Hang
- Institute of Microbiology, Department of Biology
| | - Chia-wei Lin
- Institute of Microbiology, Department of Biology
| | - Oliver C Grant
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA
| | | | - Thomas K Villiger
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Miroslav Soos
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Massimo Morbidelli
- Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Robert J Woods
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602, USA
| | - Robert Gauss
- Institute of Microbiology, Department of Biology
| | - Markus Aebi
- Institute of Microbiology, Department of Biology
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19
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Emerging structural insights into glycoprotein quality control coupled with N-glycan processing in the endoplasmic reticulum. Molecules 2015; 20:2475-91. [PMID: 25647580 PMCID: PMC6272264 DOI: 10.3390/molecules20022475] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 01/04/2015] [Accepted: 01/22/2015] [Indexed: 01/22/2023] Open
Abstract
In the endoplasmic reticulum (ER), the sugar chain is initially introduced onto newly synthesized proteins as a triantennary tetradecasaccharide (Glc3Man9GlcNAc2). The attached oligosaccharide chain is subjected to stepwise trimming by the actions of specific glucosidases and mannosidases. In these processes, the transiently expressed N-glycans, as processing intermediates, function as signals for the determination of glycoprotein fates, i.e., folding, transport, or degradation through interactions of a series of intracellular lectins. The monoglucosylated glycoforms are hallmarks of incompletely folded states of glycoproteins in this system, whereas the outer mannose trimming leads to ER-associated glycoprotein degradation. This review outlines the recently emerging evidence regarding the molecular and structural basis of this glycoprotein quality control system, which is regulated through dynamic interplay among intracellular lectins, glycosidases, and glycosyltransferase. Structural snapshots of carbohydrate-lectin interactions have been provided at the atomic level using X-ray crystallographic analyses. Conformational ensembles of uncomplexed triantennary high-mannose-type oligosaccharides have been characterized in a quantitative manner using molecular dynamics simulation in conjunction with nuclear magnetic resonance spectroscopy. These complementary views provide new insights into glycoprotein recognition in quality control coupled with N-glycan processing.
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20
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Iannotti MJ, Figard L, Sokac AM, Sifers RN. A Golgi-localized mannosidase (MAN1B1) plays a non-enzymatic gatekeeper role in protein biosynthetic quality control. J Biol Chem 2014; 289:11844-11858. [PMID: 24627495 DOI: 10.1074/jbc.m114.552091] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Conformation-based disorders are manifested at the level of protein structure, necessitating an accurate understanding of how misfolded proteins are processed by the cellular proteostasis network. Asparagine-linked glycosylation plays important roles for protein quality control within the secretory pathway. The suspected role for the MAN1B1 gene product MAN1B1, also known as ER mannosidase I, is to function within the ER similar to the yeast ortholog Mns1p, which removes a terminal mannose unit to initiate a glycan-based ER-associated degradation (ERAD) signal. However, we recently discovered that MAN1B1 localizes to the Golgi complex in human cells and uncovered its participation in ERAD substrate retention, retrieval to the ER, and subsequent degradation from this organelle. The objective of the current study was to further characterize the contribution of MAN1B1 as part of a Golgi-based quality control network. Multiple lines of experimental evidence support a model in which neither the mannosidase activity nor catalytic domain is essential for the retention or degradation of the misfolded ERAD substrate Null Hong Kong. Instead, a highly conserved, vertebrate-specific non-enzymatic decapeptide sequence in the luminal stem domain plays a significant role in controlling the fate of overexpressed Null Hong Kong. Together, these findings define a new functional paradigm in which Golgi-localized MAN1B1 can play a mannosidase-independent gatekeeper role in the proteostasis network of higher eukaryotes.
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Affiliation(s)
- Michael J Iannotti
- Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030; Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas 77030
| | - Lauren Figard
- Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Anna M Sokac
- Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030
| | - Richard N Sifers
- Interdepartmental Program in Cell and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030; Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas 77030; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, Texas 77030; Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030.
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21
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Fujimoto Z, Tateno H, Hirabayashi J. Lectin structures: classification based on the 3-D structures. Methods Mol Biol 2014; 1200:579-606. [PMID: 25117265 DOI: 10.1007/978-1-4939-1292-6_46] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Recent progress in structural biology has elucidated the three-dimensional structures and carbohydrate-binding mechanisms of most lectin families. Lectins are classified into 48 families based on their three-dimensional structures. A ribbon drawing gallery of the crystal and solution structures of representative lectins or lectin-like proteins is appended and may help to convey the diversity of lectin families, the similarity and differences between lectin families, as well as the carbohydrate-binding architectures of lectins.
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Affiliation(s)
- Zui Fujimoto
- Biomolecular Research Unit, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, 305-8602, Japan,
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22
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Thompson AJ, Dabin J, Iglesias-Fernández J, Ardèvol A, Dinev Z, Williams SJ, Bande O, Siriwardena A, Moreland C, Hu TC, Smith DK, Gilbert HJ, Rovira C, Davies GJ. The Reaction Coordinate of a Bacterial GH47 α-Mannosidase: A Combined Quantum Mechanical and Structural Approach. Angew Chem Int Ed Engl 2012; 51:10997-1001. [DOI: 10.1002/anie.201205338] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Indexed: 11/10/2022]
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23
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Thompson AJ, Dabin J, Iglesias-Fernández J, Ardèvol A, Dinev Z, Williams SJ, Bande O, Siriwardena A, Moreland C, Hu TC, Smith DK, Gilbert HJ, Rovira C, Davies GJ. The Reaction Coordinate of a Bacterial GH47 α-Mannosidase: A Combined Quantum Mechanical and Structural Approach. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201205338] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Bontjer I, Melchers M, Eggink D, David K, Moore JP, Berkhout B, Sanders RW. Stabilized HIV-1 envelope glycoprotein trimers lacking the V1V2 domain, obtained by virus evolution. J Biol Chem 2010; 285:36456-70. [PMID: 20826824 DOI: 10.1074/jbc.m110.156588] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The envelope glycoproteins (Env) are the focus of HIV-1 vaccine development strategies based on the induction of humoral immunity, but the mechanisms the virus has evolved to limit the induction and binding of neutralizing antibodies (NAbs) constitute substantial obstacles. Conserved neutralization epitopes are shielded by variable regions and carbohydrates, so one strategy to increase their exposure and, it is hoped, their immunogenicity is to delete the overlying variable loops. However, deleting the variable regions from Env trimers can be problematic, because hydrophobic patches that are normally solvent-inaccessible now become exposed, causing protein misfolding or aggregation, for example. Here, we describe the construction and characterization of recombinant gp140 trimers lacking variable domains 1 and 2 (ΔV1V2). The design of the trimers was guided by HIV-1 evolution studies that identified compensatory changes in V1V2-deleted but functional Env proteins (Bontjer, I., Land, A., Eggink, D., Verkade, E., Tuin, K., Baldwin, C., Pollakis, G., Paxton, W. A., Braakman, I., Berkhout, B., and Sanders, R. W. (2009) J. Virol. 83, 368-383). We now show that specific compensatory changes improved the function of ΔV1V2 Env proteins and hence HIV-1 replication. The changes acted by reducing the exposure of a hydrophobic surface either by replacing a hydrophobic residue with a hydrophilic one or by covering the surface with a glycan. The compensatory changes allowed the efficient expression of well folded, soluble gp140 trimers derived from various HIV-1 isolates. The evolved ΔV1V2 Env viruses were extremely sensitive to NAbs, indicating that neutralization epitopes are well exposed, which was confirmed by studies of NAb binding to the soluble ΔV1V2 gp140 trimers. These evolved ΔV1V2 trimers could be useful reagents for immunogenicity and structural studies.
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Affiliation(s)
- Ilja Bontjer
- Laboratory of Experimental Virology, Department of Medical Microbiology, Academic Medical Center of the University of Amsterdam, 1105 AZ Amsterdam, The Netherlands
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25
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Endoplasmic reticulum associated protein degradation: a chaperone assisted journey to hell. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:694-705. [PMID: 20219571 DOI: 10.1016/j.bbamcr.2010.02.005] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 02/11/2010] [Accepted: 02/18/2010] [Indexed: 01/16/2023]
Abstract
Recognition and elimination of misfolded proteins are essential cellular processes. More than thirty percent of the cellular proteins are proteins of the secretory pathway. They fold in the lumen or membrane of the endoplasmic reticulum from where they are sorted to their site of action. The folding process, as well as any refolding after cell stress, depends on chaperone activity. In case proteins are unable to acquire their native conformation, chaperones with different substrate specificity and activity guide them to elimination. For most misfolded proteins of the endoplasmic reticulum this requires retro-translocation to the cytosol and polyubiquitylation of the misfolded protein by an endoplasmic reticulum associated machinery. Thereafter ubiquitylated proteins are guided to the proteasome for degradation. This review summarizes our up to date knowledge of chaperone classes and chaperone function in endoplasmic reticulum associated degradation of protein waste.
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26
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Hosokawa N, Tremblay LO, Sleno B, Kamiya Y, Wada I, Nagata K, Kato K, Herscovics A. EDEM1 accelerates the trimming of 1,2-linked mannose on the C branch of N-glycans. Glycobiology 2010; 20:567-75. [DOI: 10.1093/glycob/cwq001] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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27
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Vangheluwe P, Sepúlveda MR, Missiaen L, Raeymaekers L, Wuytack F, Vanoevelen J. Intracellular Ca2+- and Mn2+-Transport ATPases. Chem Rev 2009; 109:4733-59. [DOI: 10.1021/cr900013m] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Peter Vangheluwe
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - M. Rosario Sepúlveda
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Ludwig Missiaen
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Luc Raeymaekers
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Frank Wuytack
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - Jo Vanoevelen
- Laboratory of Ca2+-transport ATPases and Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium
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Zhou J, Lin CZ, Zheng XZ, Lin XJ, Sang WJ, Wang SH, Wang ZH, Ebbole D, Lu GD. Functional analysis of an α-1,2-mannosidase from Magnaporthe oryzae. Curr Genet 2009; 55:485-96. [DOI: 10.1007/s00294-009-0261-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Revised: 06/28/2009] [Accepted: 07/03/2009] [Indexed: 11/25/2022]
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29
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Liu XQ, Wu L, Guo XJ. Effect of Bu-Zhong-Yi-Qi-Tang on deficiency of N-glycan/nitric oxide and islet damage induced by streptozotocin in diabetic rats. World J Gastroenterol 2009; 15:1730-7. [PMID: 19360916 PMCID: PMC2668778 DOI: 10.3748/wjg.15.1730] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effect of Bu-Zhong-Yi-Qi-Tang (Decoction for Reinforcing Middle Jiao and Replenishing Qi) on deficiency of N-glycan/nitric oxide (NO) and islet damage induced by injecting two medium doses of streptozotocin (STZ).
METHODS: Diabetes was induced by intraperitoneal injection of STZ at 55 mg/kg on day 1 and day 8. Islet damage was evaluated using a scoring system. Nitrite, nitrate, α-mannosidase and amylase activities were measured by colorimetry. N-glycan patterns of amylase were determined with lectin [ConA, pisum sativum agglutinin (PSA), peanut agglutinin (PNA), and lens culinaris agglutinin (LCA)] affinity precipitation method.
RESULTS: Severe islet necrosis and mild islet atrophy were observed in diabetic rats. The number and size of islets, the activities of α-mannosidase, amylase and nitrite were decreased, while the binding of PNA and LCA to amylase was increased. All of which were improved after treatment with Bu-Zhong-Yi-Qi-Tang. Islet damage was significantly correlated with nitrite, nitrate, α-mannosidase, amylase and the binding of LCA, PNA, and PSA to amylase.
CONCLUSION: STZ-induced islet damage is related to N-glycan deficiency in proteins by blocking α-mannosidase activity and no deficiency, accumulation of unfolded proteins, and endoplasmic reticulum stress and activation of cellular signals, all of which are improved after treatment with Bu-Zhong-Yi-Qi-Tang.
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Cantú D, Nerinckx W, Reilly PJ. Theory and computation show that Asp463 is the catalytic proton donor in human endoplasmic reticulum α-(1→2)-mannosidase I. Carbohydr Res 2008; 343:2235-42. [DOI: 10.1016/j.carres.2008.05.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 05/07/2008] [Accepted: 05/13/2008] [Indexed: 11/25/2022]
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Structural biology of pectin degradation by Enterobacteriaceae. Microbiol Mol Biol Rev 2008; 72:301-16, table of contents. [PMID: 18535148 DOI: 10.1128/mmbr.00038-07] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
SUMMARY Pectin is a structural polysaccharide that is integral for the stability of plant cell walls. During soft rot infection, secreted virulence factors from pectinolytic bacteria such as Erwinia spp. degrade pectin, resulting in characteristic plant cell necrosis and tissue maceration. Catabolism of pectin and its breakdown products by pectinolytic bacteria occurs within distinct cellular environments. This process initiates outside the cell, continues within the periplasmic space, and culminates in the cytoplasm. Although pectin utilization is well understood at the genetic and biochemical levels, an inclusive structural description of pectinases and pectin binding proteins by both extracellular and periplasmic enzymes has been lacking, especially following the recent characterization of several periplasmic components and protein-oligogalacturonide complexes. Here we provide a comprehensive analysis of the protein folds and mechanisms of pectate lyases, polygalacturonases, and carbohydrate esterases and the binding specificities of two periplasmic pectic binding proteins from Enterobacteriaceae. This review provides a structural understanding of the molecular determinants of pectin utilization and the mechanisms driving catabolite selectivity and flow through the pathway.
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Crystal Structure of YihS in Complex with d-Mannose: Structural Annotation of Escherichia coli and Salmonella enterica yihS-encoded Proteins to an Aldose–Ketose Isomerase. J Mol Biol 2008; 377:1443-59. [DOI: 10.1016/j.jmb.2008.01.090] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 01/18/2008] [Accepted: 01/22/2008] [Indexed: 11/20/2022]
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33
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Lobsanov YD, Yoshida T, Desmet T, Nerinckx W, Yip P, Claeyssens M, Herscovics A, Howell PL. Modulation of activity by Arg407: structure of a fungal alpha-1,2-mannosidase in complex with a substrate analogue. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2008; 64:227-36. [PMID: 18323617 DOI: 10.1107/s0907444907065572] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Accepted: 12/04/2007] [Indexed: 11/10/2022]
Abstract
Class I alpha-mannosidases (glycoside hydrolase family GH47) play key roles in the maturation of N-glycans and the ER-associated degradation of unfolded glycoproteins. The 1.95 A resolution structure of a fungal alpha-1,2-mannosidase in complex with the substrate analogue methyl-alpha-D-lyxopyranosyl-(1',2)-alpha-D-mannopyranoside (LM) shows the intact disaccharide spanning the -1/+1 subsites, with the D-lyxoside ring in the -1 subsite in the 1C4 chair conformation, and provides insight into the mechanism of catalysis. The absence of the C5' hydroxymethyl group on the D-lyxoside moiety results in the side chain of Arg407 adopting two alternative conformations: the minor one interacting with Asp375 and the major one interacting with both the D-lyxoside and the catalytic base Glu409, thus disrupting its function. Chemical modification of Asp375 has previously been shown to inactivate the enzyme. Taken together, the data suggest that Arg407, which belongs to the conserved sequence motif RPExxE, may act to modulate the activity of the enzyme. The proposed mechanism for modulating the activity is potentially a general mechanism for this superfamily.
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Affiliation(s)
- Yuri D Lobsanov
- Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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34
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Abbott DW, Boraston AB. A family 2 pectate lyase displays a rare fold and transition metal-assisted beta-elimination. J Biol Chem 2007; 282:35328-36. [PMID: 17881361 DOI: 10.1074/jbc.m705511200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The family 2 pectate lyase from Yersinia enterocolitica (YePL2A), solved to 1.5A, reveals it to be the first prokaryotic protein reported to display the rare (alpha/alpha)(7) barrel fold. In addition to its apo form, we have also determined the structure of a metal-bound form of YePL2A (to 2.0A) and a trigalacturonic acid-bound substrate complex (to 2.1A) Although its fold is rare, the catalytic center of YePL2A can be superimposed with structurally unrelated families, underlining the conserved catalytic amino acid architecture of the beta-elimination mechanism. In addition to its overall structure, YePL2A also has two other unique features: 1) it utilizes a metal atom other than calcium for catalysis, and 2) its Brønstead base is in an alternate conformation and directly interacts with the uronate group of the substrate.
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Affiliation(s)
- D Wade Abbott
- Biochemistry & Microbiology, University of Victoria, Victoria, British Columbia V8W 3P6, Canada
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35
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Mora-Montes HM, López-Romero E, Zinker S, Ponce-Noyola P, Flores-Carreón A. Conversion of α1,2-mannosidase E-I from Candida albicans to α1,2-mannosidase E-II by limited proteolysis. Antonie van Leeuwenhoek 2007; 93:61-9. [PMID: 17588125 DOI: 10.1007/s10482-007-9179-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Accepted: 05/23/2007] [Indexed: 10/23/2022]
Abstract
Previous studies demonstrated the presence in Candida albicans ATCC 26555 of two soluble alpha1,2-mannosidases: E-I and E-II. In contrast, in the C. albicans CAI-4 mutant only E-I was detected and it could be processed by a membrane-bound proteolytic activity from the ATCC 26555 strain, generating an active 43 kDa polypeptide. Here, alpha1,2-mannosidase E-I from strain ATCC 26555 was purified by conventional methods of protein isolation and affinity chromatography in Concanavalin A-Sepharose 4B. Analytical electrophoresis of the purified enzyme revealed two polypeptides of 52 and 23 kDa, the former being responsible for enzyme activity as revealed by zymogram analysis. Time course proteolysis with an aspartyl protease from Aspergillus saitoi, converted alpha1,2-mannosidase E-I into an active polypeptide of 43 kDa which trimmed Man(9)GlcNAc(2), generating Man(8)GlcNAc(2) isomer B and mannose. Trimming was inhibited preferentially by 1-deoxymannojirimycin. Both, the molecular mass and the enzyme properties of the proteolytic product were identical to those described for alpha1,2-mannosidase E-II therefore supporting the notion that E-I is the precursor of E-II.
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Affiliation(s)
- Héctor Manuel Mora-Montes
- Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Apartado postal 187, Guanajuato, Gto, CP 36000, Mexico
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36
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Chevrier C, Defoin A, Tarnus C. Synthesis and evaluation of amino-threoses in d- and l-series: Are five membered ring amino-sugars more potent glycosidase inhibitors than the six membered ones? Bioorg Med Chem 2007; 15:4125-35. [PMID: 17434740 DOI: 10.1016/j.bmc.2007.03.073] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Revised: 03/18/2007] [Accepted: 03/23/2007] [Indexed: 11/18/2022]
Abstract
Cyclic D- and L-4-aminothreose were synthesised from ethyl D- and L-tartrate, respectively. D-aminothreose was a potent inhibitor of alpha-glucosidase and of alpha-mannosidase. From the glycosidase inhibition potencies of the four 4-amino-4-deoxy-tetroses, the contribution of binding of each functionality of the 5 and 6 membered ring amino-sugars towards the various glycosidases is discussed.
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Affiliation(s)
- Carine Chevrier
- Laboratoire de Chimie Organique et Bioorganique, UMR 7015, Ecole Nationale Supérieure de Chimie de Mulhouse, Université de Haute-Alsace, 3, rue Alfred Werner, F-68093 Mulhouse Cédex, France
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37
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Mulakala C, Nerinckx W, Reilly PJ. The fate of β-d-mannopyranose after its formation by endoplasmic reticulum α-(1→2)-mannosidase I catalysis. Carbohydr Res 2007; 342:163-9. [PMID: 17157281 DOI: 10.1016/j.carres.2006.11.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2006] [Revised: 10/26/2006] [Accepted: 11/07/2006] [Indexed: 11/21/2022]
Abstract
The automated docking program AutoDock was used to dock all 38 characteristic beta-D-mannopyranose ring conformers into the active site of the yeast endoplasmic reticulum alpha-(1-->2)-mannosidase I, a Family 47 glycoside hydrolase that converts Man9GlcNAc2 to Man8GlcNAc2. The subject of this work is to establish the conformational pathway that allows the cleaved glycon product to leave the enzyme active site and eventually reach the ground-state conformation. Twelve of the 38 conformers optimally dock in the active site where the inhibitors 1-deoxymannonojirimycin and kifunensine are found in enzyme crystal structures. A further 23 optimally dock in a second site on the side of the active-site well, while three dock outside the active-site cavity. It appears, through analysis of the internal energies of different ring conformations, of intermolecular energies between the ligands and enzyme, and of forces exerted on the ligands by the enzyme, that beta-D-mannopyranose follows the path 3E-->1C4-->1H2-->B2,5 before being expelled by the enzyme. The highly conserved second site that strongly binds beta-D-mannopyranose-4C1 may exist to prevent competitive inhibition by the product, and is worthy of further investigation.
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Affiliation(s)
- Chandrika Mulakala
- Department of Chemical and Biological Engineering, 2114 Sweeney Hall, Iowa State University, Ames, IA 50011, USA
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38
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Abstract
This chapter focuses on protein engineering strategies that aim to increase the chances of obtaining crystals suitable for X-ray diffraction. The chapter is divided into three main parts: one dealing with protein engineering through a bioinformatics approach, the second focusing on DNA modifications via random mutagenesis, and the third describing a nonexhaustive number of in vitro modifications based on site-directed mutagenesis.
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Affiliation(s)
- Sonia Longhi
- Architecture et Fonction des Macromolécules Biologiques, Centre National de la Recherche Scientifique, Universités Aix-Marseille I et II, Marseille, France
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39
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Tremblay LO, Nagy Kovács E, Daniels E, Wong NK, Sutton-Smith M, Morris HR, Dell A, Marcinkiewicz E, Seidah NG, McKerlie C, Herscovics A. Respiratory distress and neonatal lethality in mice lacking Golgi alpha1,2-mannosidase IB involved in N-glycan maturation. J Biol Chem 2006; 282:2558-66. [PMID: 17121831 DOI: 10.1074/jbc.m608661200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
There are three mammalian Golgi alpha1,2-mannosidases, encoded by different genes, that form Man5GlcNAc2 from Man(8-9)GlcNAc2 for the biosynthesis of hybrid and complex N-glycans. Northern blot analysis and in situ hybridization indicate that the three paralogs display distinct developmental and tissue-specific expression. The physiological role of Golgi alpha1,2-mannosidase IB was investigated by targeted gene ablation. The null mice have normal gross appearance at birth, but they display respiratory distress and die within a few hours. Histology of fetal lungs the day before birth indicate some delay in development, whereas neonatal lungs show extensive pulmonary hemorrhage in the alveolar region. No significant histopathological changes occur in other tissues. No remarkable ultrastructural differences are detected between wild type and null lungs. The membranes of a subset of bronchiolar epithelial cells are stained with lectins from Phaseolus vulgaris (leukoagglutinin and erythroagglutinin) and Datura stramonium in wild type lungs, but this staining disappears in lungs from null mice. Mass spectrometry of N-glycans from different tissues shows no significant changes in global N-glycans of null mice. Therefore, only a few glycoproteins required for normal lung function depend on alpha1,2-mannosidase IB for maturation. There are no apparent differences in the expression of several lung epithelial cell and endothelial cell markers between null and wild type mice. The alpha1,2-mannosidase IB null phenotype differs from phenotypes caused by ablation of other enzymes in N-glycan biosynthesis and from other mouse gene disruptions that affect pulmonary development and function.
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Affiliation(s)
- Linda O Tremblay
- McGill Cancer Centre, McGill University, Montréal, Québec, Canada
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40
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Mulakala C, Nerinckx W, Reilly PJ. Docking studies on glycoside hydrolase Family 47 endoplasmic reticulum alpha-(1-->2)-mannosidase I to elucidate the pathway to the substrate transition state. Carbohydr Res 2006; 341:2233-45. [PMID: 16806128 DOI: 10.1016/j.carres.2006.05.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2006] [Revised: 05/03/2006] [Accepted: 05/11/2006] [Indexed: 11/23/2022]
Abstract
Alpha-(1-->2)-mannosidase I from the endoplasmic reticulum (ERManI), a Family 47 glycoside hydrolase, is a key enzyme in the N-glycan synthesis pathway. Catalytic-domain crystal structures of yeast and human ERMan1s have been determined, the former with a hydrolytic product and the latter without ligands, with the inhibitors 1-deoxymannojirimycin and kifunensine, and with a thiodisaccharide substrate analog. Both inhibitors were bound at the base of the funnel-shaped active site as the unusual 1C4 conformer, while the substrate analog glycon is a 3S1 conformer. In the current study, AutoDock was used to dock alpha-D-mannopyranosyl-(1-->2)-alpha-D-mannopyranose with its glycon in chair (1C4,4C1), half-chair (3H2,3H4,4H3), skew-boat (OS2,3S1,5S1), boat (2,5B,3,OB,B1,4,B2,5), and envelope (3E,4E,E3,E4) conformations into the yeast ERManI active site. Both docked energies and forces on docked ligand atoms were calculated to determine how the ligand distorts to the transition state. From these, we can conclude that (1) both 1C4 and OS2 can be the starting conformers; (2) the most likely binding pathway is 1C4-->3H2-->OS2-->3,OB-->3S1-->3E; (3) the transition state is likely to be close to a 3E conformation.
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Affiliation(s)
- Chandrika Mulakala
- Department of Chemical and Biological Engineering, 2114 Sweeney Hall, Iowa State University, Ames, IA 50011, USA
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41
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Hirao K, Natsuka Y, Tamura T, Wada I, Morito D, Natsuka S, Romero P, Sleno B, Tremblay LO, Herscovics A, Nagata K, Hosokawa N. EDEM3, a soluble EDEM homolog, enhances glycoprotein endoplasmic reticulum-associated degradation and mannose trimming. J Biol Chem 2006; 281:9650-8. [PMID: 16431915 DOI: 10.1074/jbc.m512191200] [Citation(s) in RCA: 198] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Quality control in the endoplasmic reticulum ensures that only properly folded proteins are retained in the cell through mechanisms that recognize and discard misfolded or unassembled proteins in a process called endoplasmic reticulum-associated degradation (ERAD). We previously cloned EDEM (ER degradation-enhancing alpha-mannosidase-like protein) and showed that it accelerates ERAD of misfolded glycoproteins. We now cloned mouse EDEM3, a soluble homolog of EDEM. EDEM3 consists of 931 amino acids and has all the signature motifs of Class I alpha-mannosidases (glycosyl hydrolase family 47) in its N-terminal domain and a protease-associated motif in its C-terminal region. EDEM3 accelerates glycoprotein ERAD in transfected HEK293 cells, as shown by increased degradation of misfolded alpha1-antitrypsin variant (null (Hong Kong)) and of TCRalpha. Overexpression of EDEM3 also greatly stimulates mannose trimming not only from misfolded alpha1-AT null (Hong Kong) but also from total glycoproteins, in contrast to EDEM, which has no apparent alpha1,2-mannosidase activity. Furthermore, overexpression of the E147Q EDEM3 mutant, which has the mutation in one of the conserved acidic residues essential for enzyme activity of alpha1,2-mannosidases, abolishes the stimulation of mannose trimming and greatly decreases the stimulation of ERAD by EDEM3. These results show that EDEM3 has alpha1,2-mannosidase activity in vivo, suggesting that the mechanism whereby EDEM3 accelerates glycoprotein ERAD is different from that of EDEM.
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Affiliation(s)
- Kazuyoshi Hirao
- Department of Molecular and Cellular Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8397, Japan, CREST, JST, Saitama 332-0012, Japan
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42
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Abstract
Alpha-mannosidases in eukaryotic cells are involved in both glycan biosynthetic reactions and glycan catabolism. Two broad families of enzymes have been identified that cleave terminal mannose linkages from Asn-linked oligosaccharides (Moremen, 2000), including the Class 1 mannosidases (CAZy GH family 47 (Henrissat and Bairoch, 1996)) of the early secretory pathway involved in the processing of N-glycans and quality control and the Class 2 mannosidases (CAZy family GH38 [Henrissat and Bairoch, 1996]) involved in glycoprotein biosynthesis or catabolism. Within the Class 1 family of alpha-mannosidases, three subfamilies of enzymes have been identified (Moremen, 2000). The endoplasmic reticulum (ER) alpha1,2-mannosidase I (ERManI) subfamily acts to cleave a single residue from Asn-linked glycans in the ER. The Golgi alpha-mannosidase I (GolgiManI) subfamily has at least three members in mammalian systems (Herscovics et al., 1994; Lal et al., 1994; Tremblay and Herscovics, 2000) involved in glycan maturation in the Golgi complex to form the Man(5)GlcNAc(2) processing intermediate. The third subfamily of GH47 proteins comprises the ER degradation, enhancing alpha-mannosidase-like proteins (EDEM proteins) (Helenius and Aebi, 2004; Hirao et al., 2006; Mast et al., 2005). These proteins have been proposed to accelerate the degradation of misfolded proteins in the lumen of the ER by a lectin function that leads to retrotranslocation to the cytosol and proteasomal degradation. Recent studies have also indicated that ERManI acts as a timer for initiation of glycoprotein degradation via the ubiquitin-proteasome pathway (Hosokawa et al., 2003; Wu et al., 2003). This article discusses methods for analysis of the GH47 alpha-mannosidases, including expression, purification, activity assays, generation of point mutants, and binding studies by surface plasmon resonance.
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Affiliation(s)
- Steven W Mast
- Department of Biochemistry & Molecular Biology, University of Georgia Complex Carbohydrate Research Center, Athens, GA, USA
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43
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Hering KW, Karaveg K, Moremen KW, Pearson WH. A Practical Synthesis of Kifunensine Analogues as Inhibitors of Endoplasmic Reticulum α-Mannosidase I. J Org Chem 2005; 70:9892-904. [PMID: 16292820 DOI: 10.1021/jo0516382] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[reaction: see text] A practical synthesis of the potent class I alpha-mannosidase inhibitor kifunensine (1) beginning from the inexpensive and readily available starting material L-ascorbic acid (15) is described. The protected amino-alcohol ((2R,3R,4R,5R)-5-amino-2,3:4,6-diisopropylidenedioxyhexanol, 11) served as a key intermediate from which several N-1 substituted kifunensine analogues (including N-methyl, N-cyclohexyl, and N-bis(hydroxymethyl)methyl) and 2-desoxakifunensine analogues (including N-H and N-methyl) were prepared and screened for inhibition of human endoplasmic reticulum alpha-mannosidase I (ER Man I) and mouse Golgi alpha-mannosidase IA (Golgi Man IA). In addition, several pseudodisaccharide kifunensine analogues in which a mannose residue was tethered to N-1 of kifunensine via a two-, three-, or four-carbon linker and an affinity-bound kifunensine analogue were also prepared and evaluated for biological activity. While the synthesized N-1 kifunesine analogues were found to be less potent inhibitors of Class I alpha-mannosidases than kifuensine itself, the bis(hydroxymethyl)methylkifunensine analogue 6 was shown to selectively inhibit ER Man I over Golgi Man IA.
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Affiliation(s)
- Kirk W Hering
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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44
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Fujiyama K, Sakuradani S, Moran DG, Yoshida T, Seki T. Effect of alpha1,2-mannosidic linkage located in a alpha1,3-branch of Man6GlcNAc2 oligosaccharide on enzyme activity of recombinant human Man9-mannosidase produced in Escherichia coli. J Biosci Bioeng 2005; 91:419-21. [PMID: 16233015 DOI: 10.1263/jbb.91.419] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2000] [Accepted: 01/18/2001] [Indexed: 11/17/2022]
Abstract
We produced the human kidney Man9-mannosidase in Escherichia coli and studied the effect of the alpha-1,2-mannosidic linkage located in the alpha branch of Manalpha1-6(Manalpha1-2Manalpha1-3)Manalpha1-6(Manalpha1-3)Manbeta1-4GlcNAcbeta1-4-GlcNAc, an N-linked oligosaccharide, on the enzyme activity. The alpha1,2-mannose residue influenced the rate of hydrolysis of and substrate preference for other alpha-1,2-mannosidic linkages.
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Affiliation(s)
- K Fujiyama
- The International Center for Biotechnology, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
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45
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Lee JE, Smith GD, Horvatin C, Huang DJT, Cornell KA, Riscoe MK, Howell PL. Structural snapshots of MTA/AdoHcy nucleosidase along the reaction coordinate provide insights into enzyme and nucleoside flexibility during catalysis. J Mol Biol 2005; 352:559-74. [PMID: 16109423 DOI: 10.1016/j.jmb.2005.07.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2005] [Revised: 07/08/2005] [Accepted: 07/10/2005] [Indexed: 11/27/2022]
Abstract
MTA/AdoHcy nucleosidase (MTAN) irreversibly hydrolyzes the N9-C1' bond in the nucleosides, 5'-methylthioadenosine (MTA) and S-adenosylhomocysteine (AdoHcy) to form adenine and the corresponding thioribose. MTAN plays a vital role in metabolic pathways involving methionine recycling, biological methylation, polyamine biosynthesis, and quorum sensing. Crystal structures of a wild-type (WT) MTAN complexed with glycerol, and mutant-enzyme and mutant-product complexes have been determined at 2.0A, 2.0A, and 2.1A resolution, respectively. The WT MTAN-glycerol structure provides a purine-free model and in combination with the previously solved thioribose-free MTAN-ADE structure, we now have separate apo structures for both MTAN binding subsites. The purine and thioribose-free states reveal an extensive enzyme-immobilized water network in their respective binding subsites. The Asp197Asn MTAN-MTA and Glu12Gln MTAN-MTR.ADE structures are the first enzyme-substrate and enzyme-product complexes reported for MTAN, respectively. These structures provide representative snapshots along the reaction coordinate and allow insight into the conformational changes of the enzyme and the nucleoside substrate. A "catalytic movie" detailing substrate binding, catalysis, and product release is presented.
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Affiliation(s)
- Jeffrey E Lee
- Structural Biology and Biochemistry, Research Institute, Hospital for Sick Children, 555 University Avenue, Toronto, Ont., Canada
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46
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Szathmary R, Bielmann R, Nita-Lazar M, Burda P, Jakob CA. Yos9 Protein Is Essential for Degradation of Misfolded Glycoproteins and May Function as Lectin in ERAD. Mol Cell 2005; 19:765-75. [PMID: 16168372 DOI: 10.1016/j.molcel.2005.08.015] [Citation(s) in RCA: 153] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2005] [Revised: 06/28/2005] [Accepted: 08/15/2005] [Indexed: 10/25/2022]
Abstract
The Htm1/EDEM protein has been proposed to act as a "degradation lectin" for endoplasmic reticulum-associated degradation (ERAD) of misfolded glycoproteins. In this study, we provide genetic and biochemical evidence that Yos9 protein in Saccharomyces cerevisiae is essential for efficient degradation of mutant glycoproteins. Yos9 is a member of the OS-9 protein family, which is conserved among eukaryotes and shows similarities with mannose-6-phosphate receptors (MPRs). We found that amino acids conserved among OS-9 family members and MPRs were essential for Yos9 protein function. Immunoprecipitation showed that Yos9 specifically associated with misfolded carboxypeptidase Y (CPY*), an ERAD substrate, but only when it carried Man8GlcNAc2 or Man5GlcNAc2 N-glycans. Our experiments further suggested that Yos9 acts in the same pathway as Htm1/EDEM. Yos9 protein is important for glycoprotein degradation and may act via its MRH domain as a degradation lectin-like protein in the glycoprotein degradation pathway.
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Affiliation(s)
- Reka Szathmary
- Institute of Microbiology, ETH Zurich, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich, Switzerland
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47
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Movsichoff F, Castro OA, Parodi AJ. Characterization of Schizosaccharomyces pombe ER alpha-mannosidase: a reevaluation of the role of the enzyme on ER-associated degradation. Mol Biol Cell 2005; 16:4714-24. [PMID: 16079177 PMCID: PMC1237077 DOI: 10.1091/mbc.e05-03-0246] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
It has been postulated that creation of Man8GlcNAc2 isomer B (M8B) by endoplasmic reticulum (ER) alpha-mannosidase I constitutes a signal for driving irreparably misfolded glycoproteins to proteasomal degradation. Contrary to a previous report, we were able to detect in vivo (but not in vitro) an extremely feeble ER alpha-mannosidase activity in Schizosaccharomyces pombe. The enzyme yielded M8B on degradation of Man9GlcNAc2 and was inhibited by kifunensin. Live S. pombe cells showed an extremely limited capacity to demannosylate Man9GlcNAc2 present in misfolded glycoproteins even after a long residence in the ER. In addition, no preferential degradation of M8B-bearing species was detected. Nevertheless, disruption of the alpha-mannosidase encoding gene almost totally prevented degradation of a misfolded glycoprotein. This and other conflicting reports may be best explained by assuming that the role of ER mannosidase on glycoprotein degradation is independent of its enzymatic activity. The enzyme, behaving as a lectin binding polymannose glycans of varied structures, would belong together with its enzymatically inactive homologue Htm1p/Mnl1p/EDEM, to a transport chain responsible for delivering irreparably misfolded glycoproteins to proteasomes. Kifunensin and 1-deoxymannojirimycin, being mannose homologues, would behave as inhibitors of the ER mannosidase or/and Htm1p/Mnl1p/EDEM putative lectin properties.
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Affiliation(s)
- Federico Movsichoff
- Laboratory of Glycobiology, Fundación Instituto Leloir, C1405BWE Buenos Aires, Argentina
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48
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Karaveg K, Moremen KW. Energetics of Substrate Binding and Catalysis by Class 1 (Glycosylhydrolase Family 47) α-Mannosidases Involved in N-Glycan Processing and Endoplasmic Reticulum Quality Control. J Biol Chem 2005; 280:29837-48. [PMID: 15911611 DOI: 10.1074/jbc.m505130200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nascent glycoproteins are subject to quality control in the lumen of the endoplasmic reticulum (ER) where they can either be effectively folded with the aid of a collection of ER chaperones or they can be targeted for disposal in a process known as ER-associated degradation. Initiation of the ER disposal process involves selective trimming of N-glycans by ER alpha-mannosidase I and subsequent recognition by the ER degradation-enhancing alpha-mannosidase-like protein family of lectins, both members of glycosylhydrolase family 47. The kinetics and energetics of substrate binding and catalysis by members of this family were investigated here by the analysis of wild type and mutant forms of human ER alpha-mannosidase I. The contributions of several amino acid residues and an enzyme-associated Ca(2+) ion to substrate binding and catalysis were demonstrated by a combination of surface plasmon resonance and enzyme kinetic analyses. One mutant, E330Q, shown previously to alter general acid function within the catalytic site, resulted in an enzyme that possessed increased glycan binding affinity but compromised glycan hydrolysis. This mutant protein was used in a series of glycan binding studies with a library of mannose-containing ligands to examine the energetics of Man(9)GlcNAc(2) substrate interactions. These studies provide a framework for understanding the nature of the unusual substrate interactions within the family 47 mannosidases involved in glycan maturation and ER-associated glycoprotein degradation.
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Affiliation(s)
- Khanita Karaveg
- Complex Carbohydrate Research Center and the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, 30602, USA
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49
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Karaveg K, Siriwardena A, Tempel W, Liu ZJ, Glushka J, Wang BC, Moremen KW. Mechanism of Class 1 (Glycosylhydrolase Family 47) α-Mannosidases Involved in N-Glycan Processing and Endoplasmic Reticulum Quality Control. J Biol Chem 2005; 280:16197-207. [PMID: 15713668 DOI: 10.1074/jbc.m500119200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Quality control in the endoplasmic reticulum (ER) determines the fate of newly synthesized glycoproteins toward either correct folding or disposal by ER-associated degradation. Initiation of the disposal process involves selective trimming of N-glycans attached to misfolded glycoproteins by ER alpha-mannosidase I and subsequent recognition by the ER degradation-enhancing alpha-mannosidase-like protein family of lectins, both members of glycosylhydrolase family 47. The unusual inverting hydrolytic mechanism catalyzed by members of this family is investigated here by a combination of kinetic and binding analyses of wild type and mutant forms of human ER alpha-mannosidase I as well as by structural analysis of a co-complex with an uncleaved thiodisaccharide substrate analog. These data reveal the roles of potential catalytic acid and base residues and the identification of a novel (3)S(1) sugar conformation for the bound substrate analog. The co-crystal structure described here, in combination with the (1)C(4) conformation of a previously identified co-complex with the glycone mimic, 1-deoxymannojirimycin, indicates that glycoside bond cleavage proceeds through a least motion conformational twist of a properly predisposed substrate in the -1 subsite. A novel (3)H(4) conformation is proposed as the exploded transition state.
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Affiliation(s)
- Khanita Karaveg
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA
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50
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Mast SW, Diekman K, Karaveg K, Davis A, Sifers RN, Moremen KW. Human EDEM2, a novel homolog of family 47 glycosidases, is involved in ER-associated degradation of glycoproteins. Glycobiology 2004; 15:421-36. [PMID: 15537790 DOI: 10.1093/glycob/cwi014] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In the endoplasmic reticulum (ER), misfolded proteins are retrotranslocated to the cytosol and degraded by the proteasome in a process known as ER-associated degradation (ERAD). Early in this pathway, a proposed lumenal ER lectin, EDEM, recognizes misfolded glycoproteins in the ER, disengages the nascent molecules from the folding pathway, and facilitates their targeting for disposal. In humans there are a total of three EDEM homologs. The amino acid sequences of these proteins are different from other lectins but are closely related to the Class I mannosidases (family 47 glycosidases). In this study, we characterize one of the EDEM homologs from Homo sapiens, which we have termed EDEM2 (C20orf31). Using recombinantly generated EDEM2, no alpha-1,2 mannosidase activity was observed. In HEK293 cells, recombinant EDEM2 is localized to the ER where it can associate with misfolded alpha1-antitrypsin. Overexpression of EDEM2 accelerates the degradation of misfolded alpha1-antitrypsin, indicating that the protein is involved in ERAD.
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Affiliation(s)
- Steven W Mast
- Department of Biochemistry and Molecular Biology and Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602-4712, USA
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