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Precisely heterogeneous ‐ the making of N‐glycoproteins
Author(s) -
Aebi Markus
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.249.1
Subject(s) - glycan , golgi apparatus , glycosyltransferase , endoplasmic reticulum , glycoprotein , biochemistry , chemistry , endoglycosidase , glycosylation , glycobiology , microbiology and biotechnology , biology , enzyme
Two dedicated organelles, the Endoplasmic Reticulum (ER) and the Golgi contain the synthetic machinery that generates N‐linked glycans, the most divers modification of proteins. The ER pathway generates a structurally highly conserved oligosaccharide that is transferred to selected asparagine residues of nascent polypeptide chains. These oligosaccharides are essential for the folding and the quality control process of glycoproteins. The subsequent trimming and remodeling of N‐linked glycans in the Golgi compartment follows a completely different regime and generates a heterogeneous assembly of N‐glycans in a species‐, protein‐ and site‐specific manner. We have established MS‐based analytical systems for the site‐specific quantification of N‐linked glycans and combined it with expression systems of model glycoproteins (such as IgG) in different cell lines. We quantified the site‐specific glyco‐heterogeneity and showed that the interaction of the glycan with the protein surface defined the processing in a given setting of hydrolases and glycosyltransferases. We hypothesized that this site‐dependent processing requires a kinetic control of glycan remodeling in the Golgi, which, in turn, is the cause for the well‐known microheterogeneity of N‐glycans. We have experimentally addressed this concept of glycan processing and followed the time‐course of intracellular N‐glycan processing in vivo using time‐resolved SILAC experiments. In addition, we assessed site‐specific N‐glycan processing in vitro using purified glycosyltransferases and hydrolases. We conclude that the compartmentalization of glycosyltransferases and hydrolases in the different Golgi stacks is a prerequisite for site‐specific N‐glycan processing. The lamellar structures of the Golgi cisternae is necessary to provide the high concentration of processing enzymes that can act only for a short time on secreted substrates. Support or Funding Information Supported by the Swiss National Science Foundation and ETH Zurich This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .