The glycan code of the endoplasmic reticulum: asparagine-linked carbohydrates as protein maturation and quality-control tags.
The majority of proteins that traverse the secretory pathway receive asparagine (Asn)-linked glycosylations. Glycans are bulky hydrophilic modifications that serve a variety of structural and functional roles within the cell. Here, we review the recent growing knowledge on the role of Asn-linked glycans as maturation and quality-control protein tags in the early secretory pathway. The carbohydrate composition encodes crucial information about the structure, localization and age of glycoproteins. The "glycan code" is encoded by a series of glycosidases and carbohydrate transferases that line the secretory pathway. This code is deciphered by carbohydrate-binding proteins that possess distinct carbohydrate binding properties and act as molecular chaperones or sorting receptors. These glycosidases and transferases work in concert with resident secretory pathway carbohydrate-binding proteins to form a network that assists in the maturation and trafficking of both native and aberrant glycoproteins within the cell.
Hebert
Daniel N
DN
Department of Biochemistry and Molecular Biology, Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, MA 01003, USA. dhebert@biochem.umass.edu
Garman
Scott C
SC
Molinari
Maurizio
M
D000818:Animals; D001216:Asparagine / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000378:metabolism*; D006023:Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D011134:Polysaccharides / Q000737:chemistry / Q000378:metabolism*; D017510:Protein Folding; D011499:Protein Processing, Post-Translational; D021381:Protein Transport
C486654:EDEM1 protein, human; D006023:Glycoproteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011134:Polysaccharides; D001216:Asparagine