Analytical Chemistry

Identification of novel high mannose N-glycan isomers undescribed by current multicellular eukaryotic biosynthetic pathways

Authors

  • Chi-Kung Ni Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan & Department of Chemistry, National Tsing Hua University, Hsinchu, 30013, Taiwan & Molecular Science and Technology (MST), Taiwan International Graduate Program (TIGP), Academia Sinica, Taipei 10617, Taiwan ,
  • Chia Yen Liew Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan & Molecular Science and Technology (MST), Taiwan International Graduate Program (TIGP), Academia Sinica, Taipei 10617, Taiwan & International Graduate Program of Molecular Science and Technology, National Taiwan University (NTU-MST), Taipei 10617, Taiwan ,
  • Hong-Sheng Luo Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan & Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan ,
  • Ting-Yi Yang Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan & Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan ,
  • An-Ti Hung Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan & Department of Chemistry, National Tsing Hua University, Hsinchu, 30013, Taiwan ,
  • Bryan John Abel Magoling Institute of Biochemical Sciences, College of Life Science, National Taiwan University, Taipei, 10617 Taiwan & Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 11529 Taiwan & Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan ,
  • Charles Pin-Kuang Lai Chemical Biology and Molecular Biophysics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 11529 Taiwan & Genome and Systems Biology Degree Program, National Taiwan University and Academia Sinica, Taipei, 10617 Taiwan & Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan

Abstract

N-linked glycosylation is one of the most important post-translational modifications of proteins. Current knowledge of multicellular eukaryote N-glycan biosynthesis suggests high mannose N-glycans are generated in the endoplasmic reticulum and Golgi apparatus through conserved biosynthetic pathways. As a part of post-translational modifications, lipid dolichol-phosphate linked oligosaccharide Glc3Man9GlcNAc2 is transferred to proteins, and glucoses and mannose are sequentially removed by various ER- and Golgi-localized glucosidases and -1,2-mannosidases. According to reported biosynthetic pathways, four Man7GlcNAc2 isomers, three Man6GlcNAc2 isomers, and one Man5GlcNAc2 isomer are generated during this process. In this study, we applied our latest mass spectrometry method, logically derived sequence tandem mass spectrometry (LODES/MSn) to re-examine high mannose N-glycans extracted from various multicellular eukaryotes. LODES/MSn identified many high mannose N-glycan isomers previously unreported in plantae, animalia, cancer cells, and fungi. Importantly, their synthesis is yet described by known biosynthetic pathways, thereby suggesting additional and unidentified pathways for these N-glycans isomers in multicellular eukaryotic cells.

Content

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