1
|
Pharmacologic inhibition of N-linked glycan trimming with kifunensine disrupts GLUT1 trafficking and glucose uptake. Biochimie 2020; 174:18-29. [PMID: 32298759 DOI: 10.1016/j.biochi.2020.04.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Revised: 03/26/2020] [Accepted: 04/06/2020] [Indexed: 02/06/2023]
Abstract
The facilitative glucose transport GLUT1 (SLC2A1) is a constitutively expressed membrane protein involved in basal uptake of blood glucose. GLUT1 modification by N-linked glycosylation at a single asparagine residue (N45) appears to play multiple roles in the trafficking, stability and transport activity of this protein. Here we examine the role of complex N-glycosylation on GLUT1 function in renal epithelial cells by arresting this modification at the high-mannose stage with the mannosidase I inhibitor kifunensine. Consistent with prior work in which GLUT1 glycosylation was completely inhibited, we find that kifunensine treatment results in a time-dependent decrease of up to 40% in cellular glucose uptake. We further demonstrate that this effect is primarily a result of deficient GLUT1 trafficking to the cell membrane due to quality control mechanisms that instead direct GLUT1 to the ER-associated degradation (ERAD) pathway. Unlike tunicamycin, which inhibits the first step in N-glycosyl transfer and causes dramatic cell cycle arrest, kifunensine causes only a modest decrease in GLUT1 levels and cell cycle progression in both normal and transformed renal cells. The effect of kifunensine on the cell cycle appears to be independent of its effect on GLUT1, since all renal cell types in this study displayed decreased proliferation regardless of their dependence on glucose uptake for growth and survival. Together these results indicate that proper N-glycan processing plays an important role in directing GLUT1 to the cell surface and that disruption of mannosidase activity results in aberrant degradation of GLUT1 by the ERAD pathway.
Collapse
|
2
|
Massarweh A, Bosco M, Iatmanen-Harbi S, Tessier C, Amana L, Busca P, Chantret I, Gravier-Pelletier C, Moore SEH. Brefeldin A promotes the appearance of oligosaccharyl phosphates derived from Glc3Man9GlcNAc2-PP-dolichol within the endomembrane system of HepG2 cells. J Lipid Res 2016; 57:1477-91. [PMID: 27281477 DOI: 10.1194/jlr.m068551] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Indexed: 01/04/2023] Open
Abstract
We reported an oligosaccharide diphosphodolichol (DLO) diphosphatase (DLODP) that generates dolichyl-phosphate and oligosaccharyl phosphates (OSPs) from DLO in vitro. This enzyme could underlie cytoplasmic OSP generation and promote dolichyl-phosphate recycling from truncated endoplasmic reticulum (ER)-generated DLO intermediates. However, during subcellular fractionation, DLODP distribution is closer to that of a Golgi apparatus (GA) marker than those of ER markers. Here, we examined the effect of brefeldin A (BFA), which fuses the GA with the ER on OSP metabolism. In order to increase the steady state level of truncated DLO while allowing formation of mature DLO (Glc3Man9GlcNAc2-PP-dolichol), dolichyl-P-mannose Man7GlcNAc2-PP-dolichol mannosyltransferase was partially downregulated in HepG2 cells. We show that BFA provokes GA endomannosidase trimming of Glc3Man9GlcNAc2-PP-dolichol to yield a Man8GlcNAc2-PP-dolichol structure that does not give rise to cytoplasmic Man8GlcNAc2-P. BFA also strikingly increased OSP derived from mature DLO within the endomembrane system without affecting levels of Man7GlcNAc2-PP-dolichol or cytoplasmic Man7GlcNAc2-P. The BFA-provoked increase in endomembrane-situated OSP is sensitive to nocodazole, and BFA causes partial redistribution of DLODP activity from GA- to ER-containing regions of density gradients. These findings are consistent with BFA-provoked microtubule-dependent GA-to-ER transport of a previously reported DLODP that acts to generate a novel endomembrane-situated OSP population.
Collapse
Affiliation(s)
- Ahmad Massarweh
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France Université Pierre et Marie Curie, Paris 6, Paris, France
| | - Michaël Bosco
- Université Paris Descartes, CICB-Paris, CNRS UMR8601, LCBPT, Paris, France
| | | | - Clarice Tessier
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| | - Laura Amana
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| | - Patricia Busca
- Université Paris Descartes, CICB-Paris, CNRS UMR8601, LCBPT, Paris, France
| | - Isabelle Chantret
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| | | | - Stuart E H Moore
- INSERM U1149, Paris, France Université Denis Diderot, Paris 7, Paris, France
| |
Collapse
|
3
|
Rymen D, Peanne R, Millón MB, Race V, Sturiale L, Garozzo D, Mills P, Clayton P, Asteggiano CG, Quelhas D, Cansu A, Martins E, Nassogne MC, Gonçalves-Rocha M, Topaloglu H, Jaeken J, Foulquier F, Matthijs G. MAN1B1 deficiency: an unexpected CDG-II. PLoS Genet 2013; 9:e1003989. [PMID: 24348268 PMCID: PMC3861123 DOI: 10.1371/journal.pgen.1003989] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Accepted: 10/09/2013] [Indexed: 11/18/2022] Open
Abstract
Congenital disorders of glycosylation (CDG) are a group of rare metabolic diseases, due to impaired protein and lipid glycosylation. In the present study, exome sequencing was used to identify MAN1B1 as the culprit gene in an unsolved CDG-II patient. Subsequently, 6 additional cases with MAN1B1-CDG were found. All individuals presented slight facial dysmorphism, psychomotor retardation and truncal obesity. Generally, MAN1B1 is believed to be an ER resident alpha-1,2-mannosidase acting as a key factor in glycoprotein quality control by targeting misfolded proteins for ER-associated degradation (ERAD). However, recent studies indicated a Golgi localization of the endogenous MAN1B1, suggesting a more complex role for MAN1B1 in quality control. We were able to confirm that MAN1B1 is indeed localized to the Golgi complex instead of the ER. Furthermore, we observed an altered Golgi morphology in all patients' cells, with marked dilatation and fragmentation. We hypothesize that part of the phenotype is associated to this Golgi disruption. In conclusion, we linked mutations in MAN1B1 to a Golgi glycosylation disorder. Additionally, our results support the recent findings on MAN1B1 localization. However, more work is needed to pinpoint the exact function of MAN1B1 in glycoprotein quality control, and to understand the pathophysiology of its deficiency. Glycosylation concerns the synthesis of sugar chains, their addition onto proteins and/or lipids, and their subsequent modifications. The resulting glycoproteins serve many critical roles in metabolism. The importance of this pathway is illustrated by a group of diseases called Congenital Disorders of Glycosylation (CDG). To date, over 60 distinct disorders have been described. In the present study, we demonstrated that mutations in MAN1B1, a gene formerly linked to non-syndromic intellectual disability, cause CDG. We described 7 patients with similar clinical features (developmental delay, intellectual disability, facial dysmorphism and obesity), defining MAN1B1-CDG as a syndrome. Furthermore, we confirmed that the MAN1B1 protein is localized into the Golgi apparatus instead of the endoplasmic reticulum, where it was assumed to reside for many years. Moreover, we showed that mutations in MAN1B1 lead to alterations of the Golgi structure.
Collapse
Affiliation(s)
- Daisy Rymen
- Center for Human Genetics, University of Leuven, Leuven, Belgium
- Center for Metabolic Diseases, University Hospital Gasthuisberg, Leuven, Belgium
| | - Romain Peanne
- Center for Human Genetics, University of Leuven, Leuven, Belgium
| | - María B. Millón
- Centro de Estudio Metabalopatías Congénitas, Faculdad de Ciencias Médicas, Universidad Nacional de Córdoba, Hospital de Niños de la Santísima Trinidad, Córdoba, Argentina
| | - Valérie Race
- Center for Human Genetics, University of Leuven, Leuven, Belgium
| | - Luisa Sturiale
- Institute of Chemistry and Technology of Polymers, CNR, Catania, Italy
| | - Domenico Garozzo
- Institute of Chemistry and Technology of Polymers, CNR, Catania, Italy
| | - Philippa Mills
- Clinical & Molecular Genetics Unit, Institute of Child Health, University College and Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom
| | - Peter Clayton
- Clinical & Molecular Genetics Unit, Institute of Child Health, University College and Great Ormond Street Hospital for Children NHS Trust, London, United Kingdom
| | - Carla G. Asteggiano
- Centro de Estudio Metabalopatías Congénitas, Faculdad de Ciencias Médicas, Universidad Nacional de Córdoba, Hospital de Niños de la Santísima Trinidad, Córdoba, Argentina
| | - Dulce Quelhas
- Unidade de Genética Médica, Departamento de Genética Humana, Centro de Genética Médica - Dr. Jacinto Magalhães - INSA, IP. Porto, Portugal
| | - Ali Cansu
- Gazi University Faculty of Medicine, Department of Paediatric Neurology, Besevler/Ankara, Turkey
| | - Esmeralda Martins
- Unidade de Doenças Metabólicas, Hospital de Crianças Maria Pia, Porto, Portugal
| | - Marie-Cécile Nassogne
- Université Catholique de Louvain, Cliniques Universitaires Saint-Luc, Brussels, Belgium
| | - Miguel Gonçalves-Rocha
- Unidade de Genética Médica, Departamento de Genética Humana, Centro de Genética Médica - Dr. Jacinto Magalhães - INSA, IP. Porto, Portugal
| | - Haluk Topaloglu
- Department of Child Neurology, Hacettepe University Children's Hospital, Ankara, Turkey
| | - Jaak Jaeken
- Center for Metabolic Diseases, University Hospital Gasthuisberg, Leuven, Belgium
| | - François Foulquier
- Structural and Functional Glycobiology Unit, UMR CNRS/USTL 8576, IFR 147, University of Lille 1, Villeneuve d'Ascq, France
| | - Gert Matthijs
- Center for Human Genetics, University of Leuven, Leuven, Belgium
- * E-mail:
| |
Collapse
|
4
|
Merulla J, Fasana E, Soldà T, Molinari M. Specificity and Regulation of the Endoplasmic Reticulum-Associated Degradation Machinery. Traffic 2013; 14:767-77. [DOI: 10.1111/tra.12068] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/18/2013] [Accepted: 03/23/2013] [Indexed: 02/05/2023]
Affiliation(s)
| | - Elisa Fasana
- Institute for Research in Biomedicine; Protein Folding and Quality Control; CH-6500; Bellinzona; Switzerland
| | - Tatiana Soldà
- Institute for Research in Biomedicine; Protein Folding and Quality Control; CH-6500; Bellinzona; Switzerland
| | | |
Collapse
|
5
|
Jadid N, Mialoundama AS, Heintz D, Ayoub D, Erhardt M, Mutterer J, Meyer D, Alioua A, Van Dorsselaer A, Rahier A, Camara B, Bouvier F. DOLICHOL PHOSPHATE MANNOSE SYNTHASE1 mediates the biogenesis of isoprenyl-linked glycans and influences development, stress response, and ammonium hypersensitivity in Arabidopsis. THE PLANT CELL 2011; 23:1985-2005. [PMID: 21558543 PMCID: PMC3123950 DOI: 10.1105/tpc.111.083634] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 04/19/2011] [Accepted: 05/01/2011] [Indexed: 05/17/2023]
Abstract
The most abundant posttranslational modification in nature is the attachment of preassembled high-mannose-type glycans, which determines the fate and localization of the modified protein and modulates the biological functions of glycosylphosphatidylinositol-anchored and N-glycosylated proteins. In eukaryotes, all mannose residues attached to glycoproteins from the luminal side of the endoplasmic reticulum (ER) derive from the polyprenyl monosaccharide carrier, dolichol P-mannose (Dol-P-Man), which is flipped across the ER membrane to the lumen. We show that in plants, Dol-P-Man is synthesized when Dol-P-Man synthase1 (DPMS1), the catalytic core, interacts with two binding proteins, DPMS2 and DPMS3, that may serve as membrane anchors for DPMS1 or provide catalytic assistance. This configuration is reminiscent of that observed in mammals but is distinct from the single DPMS protein catalyzing Dol-P-Man biosynthesis in bakers' yeast and protozoan parasites. Overexpression of DPMS1 in Arabidopsis thaliana results in disorganized stem morphology and vascular bundle arrangements, wrinkled seed coat, and constitutive ER stress response. Loss-of-function mutations and RNA interference-mediated reduction of DPMS1 expression in Arabidopsis also caused a wrinkled seed coat phenotype and most remarkably enhanced hypersensitivity to ammonium that was manifested by extensive chlorosis and a strong reduction of root growth. Collectively, these data reveal a previously unsuspected role of the prenyl-linked carrier pathway for plant development and physiology that may help integrate several aspects of candidate susceptibility genes to ammonium stress.
Collapse
Affiliation(s)
- Nurul Jadid
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
- Department of Biology, Botanical and Plant Tissue Culture Laboratory, Sepuluh Nopember Institut of Technology (Its), Gedung H Kampus Its Sukolilo, Surabaya 60111, East-Java, Indonesia
| | - Alexis Samba Mialoundama
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Dimitri Heintz
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Daniel Ayoub
- Laboratoire de Spectrométrie de Masse Bio-Organique, Département des Sciences Analytiques, Institut Pluridisciplinaire Hubert Curien du Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Université de Strasbourg, 67087 Strasbourg Cedex, France
| | - Mathieu Erhardt
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Jérôme Mutterer
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Denise Meyer
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Abdelmalek Alioua
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Alain Van Dorsselaer
- Laboratoire de Spectrométrie de Masse Bio-Organique, Département des Sciences Analytiques, Institut Pluridisciplinaire Hubert Curien du Centre National de la Recherche Scientifique, Unité Mixte de Recherche 7178, Université de Strasbourg, 67087 Strasbourg Cedex, France
| | - Alain Rahier
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Bilal Camara
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
| | - Florence Bouvier
- Institut de Biologie Moléculaire des Plantes du Centre National de la Recherche Scientifique, Université de Strasbourg, 67084 Strasbourg Cedex, France
- Address correspondence to
| |
Collapse
|
6
|
Vleugels W, Duvet S, Peanne R, Mir AM, Cacan R, Michalski JC, Matthijs G, Foulquier F. Identification of phosphorylated oligosaccharides in cells of patients with a congenital disorders of glycosylation (CDG-I). Biochimie 2011; 93:823-33. [PMID: 21315133 DOI: 10.1016/j.biochi.2011.01.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 01/29/2011] [Indexed: 11/24/2022]
Abstract
Protein N-glycosylation is initiated by the dolichol cycle in which the oligosaccharide precursor Glc(3)Man(9)GlcNAc(2)-PP-dolichol is assembled in the endoplasmic reticulum (ER). One critical step in the dolichol cycle concerns the availability of Dol-P at the cytosolic face of the ER membrane. In RFT1 cells, the lipid-linked oligosaccharide (LLO) intermediate Man(5)GlcNAc(2)-PP-Dol accumulates at the cytosolic face of the ER membrane. Since Dol-P is a rate-limiting intermediate during protein N-glycosylation, continuous accumulation of Man(5)GlcNAc(2)-PP-Dol would block the dolichol cycle. Hence, we investigated the molecular mechanisms by which accumulating Man(5)GlcNAc(2)-PP-Dol could be catabolized in RFT1 cells. On the basis of metabolic labeling experiments and in comparison to human control cells, we identified phosphorylated oligosaccharides (POS), not found in human control cells and present evidence that they originate from the accumulating LLO intermediates. In addition, POS were also detected in other CDG patients' cells accumulating specific LLO intermediates at different cellular locations. Moreover, the enzymatic activity that hydrolyses oligosaccharide-PP-Dol into POS was identified in human microsomal membranes and required Mn(2+) for optimal activity. In CDG patients' cells, we thus identified and characterized POS that could result from the catabolism of accumulating LLO intermediates.
Collapse
Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, B-3000 Leuven, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Vleugels W, Haeuptle MA, Ng BG, Michalski JC, Battini R, Dionisi-Vici C, Ludman MD, Jaeken J, Foulquier F, Freeze HH, Matthijs G, Hennet T. RFT1 deficiency in three novel CDG patients. Hum Mutat 2009; 30:1428-34. [PMID: 19701946 DOI: 10.1002/humu.21085] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The medical significance of N-glycosylation is underlined by a group of inherited human disorders called Congenital Disorders of Glycosylation (CDG). One key step in the biosynthesis of the Glc(3)Man(9)GlcNAc(2)-PP-dolichol precursor, essential for N-glycosylation, is the translocation of Man(5)GlcNAc(2)-PP-dolichol across the endoplasmic reticulum membrane. This step is facilitated by the RFT1 protein. Recently, the first RFT1-deficient CDG (RFT1-CDG) patient was identified and presented a severe N-glycosylation disorder. In the present study, we describe three novel CDG patients with an RFT1 deficiency. The first patient was homozygous for the earlier reported RFT1 missense mutation (c.199C>T; p.R67C), whereas the two other patients were homozygous for the missense mutation c.454A>G (p.K152E) and c.892G>A (p.E298 K), respectively. The pathogenic character of the novel mutations was illustrated by the accumulation of Man(5)GlcNAc(2)-PP-dolichol and by reduced recombinant DNase 1 secretion. Both the glycosylation pattern and recombinant DNase 1 secretion could be normalized by expression of normal RFT1 cDNA in the patients' fibroblasts. The clinical phenotype of these patients comprised typical CDG symptoms in addition to sensorineural deafness, rarely reported in CDG patients. The identification of additional RFT1-deficient patients allowed to delineate the main clinical picture of RFT1-CDG and confirmed the crucial role of RFT1 in Man(5)GlcNAc(2)-PP-dolichol translocation.
Collapse
Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, Leuven, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
8
|
Aebi M, Bernasconi R, Clerc S, Molinari M. N-glycan structures: recognition and processing in the ER. Trends Biochem Sci 2009; 35:74-82. [PMID: 19853458 DOI: 10.1016/j.tibs.2009.10.001] [Citation(s) in RCA: 339] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Revised: 09/30/2009] [Accepted: 10/01/2009] [Indexed: 11/26/2022]
Abstract
The processing of N-linked glycans determines secretory protein homeostasis in the eukaryotic cell. Folding and degradation of glycoproteins in the endoplasmic reticulum (ER) are regulated by molecular chaperones and enzymes recruited by specific oligosaccharide structures. Recent findings have identified several components of this protein quality control system that specifically modify N-linked glycans, thereby generating oligosaccharide structures recognized by carbohydrate-binding proteins, lectins. In turn, lectins direct newly synthesized polypeptides to the folding, secretion or degradation pathways. The "glyco-code of the ER" displays the folding status of a multitude of cargo proteins. Deciphering this code will be instrumental in understanding protein homeostasis regulation in eukaryotic cells and for intervention because such processes can have crucial importance for clinical and industrial applications.
Collapse
Affiliation(s)
- Markus Aebi
- Institute of Microbiology, Department of Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland.
| | | | | | | |
Collapse
|
9
|
Vleugels W, Keldermans L, Jaeken J, Butters TD, Michalski JC, Matthijs G, Foulquier F. Quality control of glycoproteins bearing truncated glycans in an ALG9-defective (CDG-IL) patient. Glycobiology 2009; 19:910-7. [PMID: 19451548 DOI: 10.1093/glycob/cwp067] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We describe an ALG9-defective (congenital disorders of glycosylation type IL) patient who is homozygous for the p.Y286C (c.860A>G) mutation. This patient presented with psychomotor retardation, axial hypotonia, epilepsy, failure to thrive, inverted nipples, hepatomegaly, and pericardial effusion. Due to the ALG9 deficiency, the cells of this patient accumulated the lipid-linked oligosaccharides Man(6)GlcNAc(2)-PP-dolichol and Man(8)GlcNAc(2)-PP-dolichol. It is known that the oligosaccharide structure has a profound effect on protein glycosylation. Therefore, we investigated the influence of these truncated oligosaccharide structures on the protein transfer efficiency, the quality control of newly synthesized glycoproteins, and the eventual degradation of the truncated glycoproteins formed in this patient. We demonstrated that lipid-linked Man(6)GlcNAc(2) and Man(8)GlcNAc(2) are transferred onto proteins with the same efficiency. In addition, glycoproteins bearing these Man(6)GlcNAc(2) and Man(8)GlcNAc(2) structures efficiently entered in the glucosylation/deglucosylation cycle of the quality control system to assist in protein folding. We also showed that in comparison with control cells, patient's cells degraded misfolded glycoproteins at an increasing rate. The Man(8)GlcNAc(2) isomer C on the patient's glycoproteins was found to promote the degradation of misfolded glycoproteins.
Collapse
Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, Leuven, Belgium
| | | | | | | | | | | | | |
Collapse
|
10
|
Clerc S, Hirsch C, Oggier DM, Deprez P, Jakob C, Sommer T, Aebi M. Htm1 protein generates the N-glycan signal for glycoprotein degradation in the endoplasmic reticulum. ACTA ACUST UNITED AC 2009; 184:159-72. [PMID: 19124653 PMCID: PMC2615083 DOI: 10.1083/jcb.200809198] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
To maintain protein homeostasis in secretory compartments, eukaryotic cells harbor a quality control system that monitors protein folding and protein complex assembly in the endoplasmic reticulum (ER). Proteins that do not fold properly or integrate into cognate complexes are degraded by ER-associated degradation (ERAD) involving retrotranslocation to the cytoplasm and proteasomal peptide hydrolysis. N-linked glycans are essential in glycoprotein ERAD; the covalent oligosaccharide structure is used as a signal to display the folding status of the host protein. In this study, we define the function of the Htm1 protein as an alpha1,2-specific exomannosidase that generates the Man(7)GlcNAc(2) oligosaccharide with a terminal alpha1,6-linked mannosyl residue on degradation substrates. This oligosaccharide signal is decoded by the ER-localized lectin Yos9p that in conjunction with Hrd3p triggers the ubiquitin-proteasome-dependent hydrolysis of these glycoproteins. The Htm1p exomannosidase activity requires processing of the N-glycan by glucosidase I, glucosidase II, and mannosidase I, resulting in a sequential order of specific N-glycan structures that reflect the folding status of the glycoprotein.
Collapse
Affiliation(s)
- Simone Clerc
- Department of Biology, Institute of Microbiology, Eidgenössische Technische Hochschule Zürich, Zürich, Switzerland
| | | | | | | | | | | | | |
Collapse
|
11
|
Hiss JA, Resch E, Schreiner A, Meissner M, Starzinski-Powitz A, Schneider G. Domain organization of long signal peptides of single-pass integral membrane proteins reveals multiple functional capacity. PLoS One 2008; 3:e2767. [PMID: 18648515 PMCID: PMC2447879 DOI: 10.1371/journal.pone.0002767] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 06/25/2008] [Indexed: 01/22/2023] Open
Abstract
Targeting signals direct proteins to their extra - or intracellular destination such as the plasma membrane or cellular organelles. Here we investigated the structure and function of exceptionally long signal peptides encompassing at least 40 amino acid residues. We discovered a two-domain organization (“NtraC model”) in many long signals from vertebrate precursor proteins. Accordingly, long signal peptides may contain an N-terminal domain (N-domain) and a C-terminal domain (C-domain) with different signal or targeting capabilities, separable by a presumably turn-rich transition area (tra). Individual domain functions were probed by cellular targeting experiments with fusion proteins containing parts of the long signal peptide of human membrane protein shrew-1 and secreted alkaline phosphatase as a reporter protein. As predicted, the N-domain of the fusion protein alone was shown to act as a mitochondrial targeting signal, whereas the C-domain alone functions as an export signal. Selective disruption of the transition area in the signal peptide impairs the export efficiency of the reporter protein. Altogether, the results of cellular targeting studies provide a proof-of-principle for our NtraC model and highlight the particular functional importance of the predicted transition area, which critically affects the rate of protein export. In conclusion, the NtraC approach enables the systematic detection and prediction of cryptic targeting signals present in one coherent sequence, and provides a structurally motivated basis for decoding the functional complexity of long protein targeting signals.
Collapse
Affiliation(s)
- Jan A. Hiss
- Centre for Membrane Proteomics, Institute of Cell Biology and Neuroscience, Goethe-University, Frankfurt am Main, Germany
| | - Eduard Resch
- Centre for Membrane Proteomics, Institute of Cell Biology and Neuroscience, Goethe-University, Frankfurt am Main, Germany
| | - Alexander Schreiner
- Centre for Membrane Proteomics, Institute of Cell Biology and Neuroscience, Goethe-University, Frankfurt am Main, Germany
| | - Michael Meissner
- Centre for Membrane Proteomics, Institute of Cell Biology and Neuroscience, Goethe-University, Frankfurt am Main, Germany
| | - Anna Starzinski-Powitz
- Centre for Membrane Proteomics, Institute of Cell Biology and Neuroscience, Goethe-University, Frankfurt am Main, Germany
| | - Gisbert Schneider
- Centre for Membrane Proteomics, Institute of Cell Biology and Neuroscience, Goethe-University, Frankfurt am Main, Germany
- * E-mail:
| |
Collapse
|
12
|
Henquet M, Lehle L, Schreuder M, Rouwendal G, Molthoff J, Helsper J, van der Krol S, Bosch D. Identification of the gene encoding the alpha1,3-mannosyltransferase (ALG3) in Arabidopsis and characterization of downstream n-glycan processing. THE PLANT CELL 2008; 20:1652-64. [PMID: 18567790 PMCID: PMC2483356 DOI: 10.1105/tpc.108.060731] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 05/28/2008] [Accepted: 06/05/2008] [Indexed: 05/18/2023]
Abstract
Glycosyltransferases are involved in the biosynthesis of lipid-linked N-glycans. Here, we identify and characterize a mannosyltransferase gene from Arabidopsis thaliana, which is the functional homolog of the ALG3 (Dol-P-Man:Man5GlcNAc2-PP-Dol alpha1,3-mannosyl transferase) gene in yeast. The At ALG3 protein can complement a Deltaalg3 yeast mutant and is localized to the endoplasmic reticulum in yeast and in plants. A homozygous T-DNA insertion mutant, alg3-2, was identified in Arabidopsis with residual levels of wild-type ALG3, derived from incidental splicing of the 11th intron carrying the T-DNAs. N-glycan analysis of alg3-2 and alg3-2 in the complex-glycan-less mutant background, which lacks N-acetylglucosaminyl-transferase I activity, reveals that when ALG3 activity is strongly reduced, almost all N-glycans transferred to proteins are aberrant, indicating that the Arabidopsis oligosaccharide transferase complex is remarkably substrate tolerant. In alg3-2 plants, the aberrant glycans on glycoproteins are recognized by endogenous mannosidase I and N-acetylglucosaminyltransferase I and efficiently processed into complex-type glycans. Although no high-mannose-type glycoproteins are detected in alg3-2 plants, these plants do not show a growth phenotype under normal growth conditions. However, the glycosylation abnormalities result in activation of marker genes diagnostic of the unfolded protein response.
Collapse
Affiliation(s)
- Maurice Henquet
- Laboratory of Plant Physiology, Wageningen University, 6703 BD Wageningen, The Netherlands
| | | | | | | | | | | | | | | |
Collapse
|
13
|
Calì T, Vanoni O, Molinari M. The endoplasmic reticulum crossroads for newly synthesized polypeptide chains. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2008; 83:135-79. [PMID: 19186254 DOI: 10.1016/s0079-6603(08)00604-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Tito Calì
- Institute for Research in Biomedicine, Bellizona, Switzerland
| | | | | |
Collapse
|
14
|
Moremen KW, Molinari M. N-linked glycan recognition and processing: the molecular basis of endoplasmic reticulum quality control. Curr Opin Struct Biol 2006; 16:592-9. [PMID: 16938451 PMCID: PMC3976202 DOI: 10.1016/j.sbi.2006.08.005] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2006] [Revised: 07/04/2006] [Accepted: 08/16/2006] [Indexed: 12/30/2022]
Abstract
Nascent polypeptides emerging into the lumen of the endoplasmic reticulum (ER) are N-glycosylated on asparagines in Asn-Xxx-Ser/Thr motifs. Processing of the core oligosaccharide eventually determines the fate of the associated polypeptide by regulating entry into and retention by the calnexin chaperone system, or extraction from the ER folding environment for disposal. Recent advances have shown that at least two N-glycans are necessary for protein access to the calnexin chaperone system and that polypeptide cycling in the system is a rather rare event, which, for folding-defective polypeptides, is activated only upon persistent misfolding. Additionally, dismantling of the polypeptide-bound N-glycan interrupts futile folding attempts, and elicits preparation of the misfolded chain for dislocation into the cytosol and degradation.
Collapse
Affiliation(s)
- Kelley W Moremen
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602-4712, USA
| | | |
Collapse
|
15
|
Foulquier F, Duvet S, Klein A, Mir AM, Chirat F, Cacan R. Endoplasmic reticulum-associated degradation of glycoproteins bearing Man5GlcNAc2 and Man9GlcNAc2 species in the MI8-5 CHO cell line. ACTA ACUST UNITED AC 2004; 271:398-404. [PMID: 14717707 DOI: 10.1046/j.1432-1033.2003.03938.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Endoplasmic reticulum-associated degradation of newly synthesized glycoproteins has been demonstrated previously using various mammalian cell lines. Depending on the cell type, glycoproteins bearing Man9 glycans and glycoproteins bearing Man5 glycans can be efficiently degraded. A wide variety of variables can lead to defective synthesis of lipid-linked oligosaccharides and, therefore, in mammalian cells, species derived from Man9GlcNAc2 or Man5GlcNAc2 are often recovered on newly synthesized glycoproteins. The degradation of glycoproteins bearing these two species has not been studied. We used a Chinese hamster ovary cell line lacking Glc-P-Dol-dependent glucosyltransferase I to generate various proportions of Man5GlcNAc2 and Man9GlcNAc2 on newly synthesized glycoproteins. By studying the structure of the soluble oligomannosides produced by degradation of these glycoproteins, we demonstrated the presence of a higher proportion of soluble oligomannosides originating from truncated glycans, showing that glycoproteins bearing Man5GlcNAc2 glycans are degraded preferentially.
Collapse
Affiliation(s)
- François Foulquier
- Unité de Glycobiologie Structurale et Fonctionnelle, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France
| | | | | | | | | | | |
Collapse
|
16
|
Abstract
Oligosaccharyl transferase is part of the macromolecular machinery that processes nascent proteins in the endoplasmic reticulum. The enzyme is highly conserved, catalyzes the initial step in the biosynthesis of N-linked glycoproteins and acts as a 'gatekeeper' for the secretory pathway. As more proteins associated with oligosaccharyl transferase are identified, the intricacies of the enzyme and the relationship with other proteins in the lumen of the endoplasmic reticulum are starting to be unraveled.
Collapse
Affiliation(s)
- Robert E Dempski
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | | |
Collapse
|