title: Basal autophagy is required for the efficient catabolism of sialyloligosaccharides.
abstract: Macroautophagy is an essential, homeostatic process involving degradation of a cell's own components; it plays a role in catabolizing cellular components, such as protein or lipids, and damaged or excess organelles. Here, we show that in Atg5(-/-) cells, sialyloligosaccharides specifically accumulated in the cytosol. Accumulation of these glycans was observed under non-starved conditions, suggesting that non-induced, basal autophagy is essential for their catabolism. Interestingly, once accumulated in the cytosol, sialylglycans cannot be efficiently catabolized by resumption of the autophagic process, suggesting that functional autophagy is important for preventing sialyloligosaccharides from accumulating in the cytosol. Moreover, knockdown of sialin, a lysosomal transporter of sialic acids, resulted in a significant reduction of sialyloligosaccharides, implying that autophagy affects the substrate specificity of this transporter. This study thus provides a surprising link between basal autophagy and catabolism of N-linked glycans.
authors.affiliation: From the Glycometabolome Team, Systems Glycobiology Research Group, RIKEN Max Planck Joint Research Center, RIKEN Global Research Cluster, Saitama 351-0198, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Seino
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Harada
authors.forename: Chengcheng
authors.initials: C
authors.lastname: Huang
authors.forename: Kumiko
authors.initials: K
authors.lastname: Ishii
authors.forename: Noboru
authors.initials: N
authors.lastname: Mizushima
authors.forename: Tadashi
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D003600:Cytosol / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology; D005786:Gene Expression Regulation; D008247:Lysosomes / Q000378:metabolism; D008660:Metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D009844:Oligosaccharides / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D008869:Microtubule-Associated Proteins; D009844:Oligosaccharides; D034741:RNA, Small Interfering; C016735:sialooligosaccharides
keywords: Autophagy; Glycan Catabolism; Glycoprotein; Lysosomal Glycoproteins; Lysosomes; Oligosaccharide; Sialic Acid; Sialin; Sialyloligosaccharides