title: In vivo metabolic labeling of sialoglycans in the mouse brain by using a liposome-assisted bioorthogonal reporter strategy.
abstract: Mammalian brains are highly enriched with sialoglycans, which have been implicated in brain development and disease progression. However, in vivo labeling and visualization of sialoglycans in the mouse brain remain a challenge because of the blood-brain barrier. Here we introduce a liposome-assisted bioorthogonal reporter (LABOR) strategy for shuttling 9-azido sialic acid (9AzSia), a sialic acid reporter, into the brain to metabolically label sialoglycoconjugates, including sialylated glycoproteins and glycolipids. Subsequent bioorthogonal conjugation of the incorporated 9AzSia with fluorescent probes via click chemistry enabled fluorescence imaging of brain sialoglycans in living animals and in brain sections. Newly synthesized sialoglycans were found to widely distribute on neuronal cell surfaces, in particular at synaptic sites. Furthermore, large-scale proteomic profiling identified 140 brain sialylated glycoproteins, including a wealth of synapse-associated proteins. Finally, by performing a pulse-chase experiment, we showed that dynamic sialylation is spatially regulated, and that turnover of sialoglycans in the hippocampus is significantly slower than that in other brain regions. The LABOR strategy provides a means to directly visualize and monitor the sialoglycan biosynthesis in the mouse brain and will facilitate elucidating the functional role of brain sialylation.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China;
authors.forename: Ran
authors.initials: R
authors.lastname: Xie
authors.affiliation: Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China;
authors.forename: Lu
authors.initials: L
authors.lastname: Dong
authors.affiliation: Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China;
authors.forename: Yifei
authors.initials: Y
authors.lastname: Du
authors.affiliation: Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China;
authors.forename: Yuntao
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China;
authors.forename: Rui
authors.initials: R
authors.lastname: Hua
authors.affiliation: State Key Laboratory of Membrane Biology, School of Life Sciences, Peking University, Beijing 100871, China; PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing 100871, China;
authors.forename: Chen
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China; Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China; Synthetic and Functional Biomolecules Center, Peking University, Beijing 100871, China; Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, Peking University, Beijing 100871, China xingchen@pku.edu.cn.
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D017930:Genes, Reporter / Q000502:physiology*; D008081:Liposomes / Q000737:chemistry*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence / Q000379:methods; D057054:Molecular Imaging / Q000379:methods*; D011134:Polysaccharides / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012794:Sialic Acids / Q000378:metabolism*; D013194:Staining and Labeling / Q000379:methods; D014018:Tissue Distribution
chemical_list: D008081:Liposomes; D011134:Polysaccharides; D011994:Recombinant Proteins; D012794:Sialic Acids
keywords: brain; glycoproteomics; histochemistry; live imaging; sialic acid