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Structure type: oligomer
Trivial name: carbohydrate chain of the transferrin receptor (TfR)
Compound class: N-glycan, mannan
Contained glycoepitopes: IEDB_123886,IEDB_130701,IEDB_135813,IEDB_137340,IEDB_137485,IEDB_141793,IEDB_141807,IEDB_144983,IEDB_151531,IEDB_152206,IEDB_153212,IEDB_548907,IEDB_983930,SB_197,SB_198,SB_33,SB_44,SB_67,SB_72,SB_73,SB_74,SB_85

• Article ID: 5964
  Mehlert A, Wormald MR, Ferguson MAJ "Modeling of the N-glycosylated transferrin receptor suggests how transferrin binding can occur within the surface coat of Trypanosoma brucei" - PLoS Pathogens 8(4) (2012) e1002618
  

  The transferrin receptor of bloodstream form Trypanosoma brucei is a heterodimer encoded by expression site associated genes 6 and 7. This low-abundance glycoprotein with a single glycosylphosphatidylinositol membrane anchor and eight potential N-glycosylation sites is located in the flagellar pocket. The receptor is essential for the parasite, providing its only source of iron by scavenging host transferrin from the bloodstream. Here, we demonstrate that both receptor subunits contain endoglycosidase H-sensitive and endoglycosidase H-resistant N-glycans. Lectin blotting of the purified receptor and structural analysis of the released N-glycans revealed oligomannose and paucimannose structures but, contrary to previous suggestions, no poly-N-acetyllactosamine structures were found. Overlay experiments suggest that the receptor can bind to other trypanosome glycoproteins, which may explain this discrepancy. Nevertheless, these data suggest that a current model, in which poly-N-acetyllactosamine glycans are directly involved in receptor-mediated endocytosis in bloodstream form Trypanosoma brucei, should be revised. Sequential endoglycosidase H and peptide-N-glycosidase F treatment, followed by tryptic peptide analysis, allowed the mapping of oligomannose and paucimannose structures to four of the receptor N-glycosylation sites. These results are discussed with respect to the current model for protein N-glycosylation in the parasite. Finally, the glycosylation data allowed the creation of a molecular model for the parasite transferrin receptor. This model, when placed in the context of a model for the dense variant surface glycoprotein coat in which it is embedded, suggests that receptor N-glycosylation may play an important role in providing sufficient space for the approach and binding of transferrin to the receptor, without significantly disrupting the continuity of the protective variant surface glycoprotein coat.

  glycoproteins, Glycosylphosphatidylinositol, N-glycosylation, Trypanosoma brucei, variant surface glycoprotein, transferrin receptor

  NCBI PubMed ID: 22496646
  Publication DOI: 10.1371/journal.ppat.1002618
  Journal NLM ID: 101238921
  Publisher: San Francisco, CA: Public Library of Science
  Correspondence: m.a.j.ferguson@dundee.ac.uk
  Institutions: Division of Biological Chemistry and Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
  Methods: SDS-PAGE, HPAEC, Western blotting, radiolabeling, enzymatic digestion, affinity chromatography, HPTLC, LC-MS, LC-MS/MS, lectin blotting
  
   
  
  Trypanosoma brucei
  CSDB ID 7334 (all data & tools)
• Article ID: 8598
  Harada Y, Huang C, Yamaki S, Dohmae N, Suzuki T "Phosphorylated oligosaccharides (POSs) are produced by the degradation of dolichol-linked oligosaccharides (DLOs) by an unclarified mechanism in mammalian cells. Although POSs are exclusively found in the cytosol, their intracellular fates remain unclear. Our findings indicate that POSs are catabolized via a non-lysosomal glycan degradation pathway that involves a cytosolic endo-β-N-acetylglucosaminidase (ENGase). Quantitative and structural analyses of POSs revealed that ablation of the ENGase results in the significant accumulation of POSs with a hexasaccharide structure composed of Manα1,2Manα1,3(Manα1,6)Manβ1,4GlcNAcβ1,4GlcNAc.In vitroENGase assays revealed that the presence of an α1,2-linked mannose residue facilitates the hydrolysis of POSs by the ENGase. Liquid chromatography-mass spectrometric analyses and fluorescent labeling experiments show that such POSs contain one phosphate group at the reducing end. These results indicate that ENGase efficiently hydrolyzes POSs that are larger than Man4GlcNAc2-P, generating GlcNAc-1-P and neutral Gn1-type free oligosaccharides. These results provide insight into important aspects of the generation and degradation of POSs." - Journal of Biological Chemistry 291(15) (2016) 8048-8058
  

  Phosphorylated oligosaccharides (POSs) are produced by the degradation of dolichol-linked oligosaccharides (DLOs) by an unclarified mechanism in mammalian cells. Although POSs are exclusively found in the cytosol, their intracellular fates remain unclear. Our findings indicate that POSs are catabolized via a non-lysosomal glycan degradation pathway that involves a cytosolic endo-β-N-acetylglucosaminidase (ENGase). Quantitative and structural analyses of POSs revealed that ablation of the ENGase results in the significant accumulation of POSs with a hexasaccharide structure composed of Manα1,2Manα1,3(Manα1,6)Manβ1,4GlcNAcβ1,4GlcNAc.In vitroENGase assays revealed that the presence of an α1,2-linked mannose residue facilitates the hydrolysis of POSs by the ENGase. Liquid chromatography-mass spectrometric analyses and fluorescent labeling experiments show that such POSs contain one phosphate group at the reducing end. These results indicate that ENGase efficiently hydrolyzes POSs that are larger than Man4GlcNAc2-P, generating GlcNAc-1-P and neutral Gn1-type free oligosaccharides. These results provide insight into important aspects of the generation and degradation of POSs.

  oligosaccharide, N-linked glycosylation, glycobiology, Carbohydrate Metabolism, endoplasmic reticulum (ER), endo-β-N-acetylglucosaminidase, dolichol-linked oligosaccharides, non-lysosomal glycan degradation, phosphorylated oligosaccharides

  NCBI PubMed ID: 26858256
  Publication DOI: 10.1074/jbc.M115.685313
  Journal NLM ID: 2985121R
  Publisher: Baltimore, MD: American Society for Biochemistry and Molecular Biology
  Correspondence: Suzuki T
  Institutions: Glycometabolome Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center, Global Research Cluster, RIKEN, Wako, Saitama, Japan, Global Application Development Center, Analytical and Measuring Instruments Division, Shimadzu Corp., Hadano, Kanagawa, Japan, Collaboration Promotion Unit, RIKEN Global Research Cluster, Wako, Saitama, Japan
  Methods: HPLC, LC-MS, fluorescent labeling with 2-aminopyridine
  
   
  
  Saccharomyces cerevisiae alg11Δ
  CSDB ID 49429 (all data & tools)