Discrimination between lumenal and cytosolic sites of deglycosylation in endoplasmic reticulum-associated degradation of glycoproteins by using benzyl mannose in CHO cell lines.
Recent studies demonstrated that deglycosylation step is a prerequisite for endoplasmic reticulum (ER)-associated degradation of misfolded glycoproteins. Here, we report the advantages of using benzyl mannose during pulse-chase experiments to study the subcellular location of the deglycosylation step in Chinese hamster ovary (CHO) cell lines. Benzyl mannose inhibited both the ER-to-cytosol transport of oligomannosides and the trimming of cytosolic-labeled oligomannosides by the cytosolic mannosidase in vivo. We pointed out the occurrence of two subcellular sites of deglycosylation. The first one is located in the ER lumen, and led to the formation of Man8GlcNAc2 (isomer B) in wild-type CHO cell line and Man4GlcNAc2 in Man-P-Dol-deficient cell line. The second one was revealed in CHO mutant cell lines for which a high rate of glycoprotein degradation was required. It occurred in the cytosol and led to the liberation of oligosaccharides species with one GlcNAc residue and with a pattern similar to the one bound onto glycoproteins. The cytosolic deglycosylation site was not specific for CHO mutant cell lines, since we demonstrated the occurrence of cytosolic pathway when the formation of truncated glycans was induced in wild-type cells.
Duvet
Sandrine
S
Unité de Glycobiologie Structurale et Fonctionnelle, UMR CNRS 8576, IFR 118, GDR CNRS 2590, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq, France.
Foulquier
François
F
Mir
Anne-Marie
AM
Chirat
Frédéric
F
Cacan
René
R
D000818:Animals; D001692:Biological Transport; D016466:CHO Cells; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation; D006868:Hydrolysis; D008358:Mannose / Q000378:metabolism*; D009844:Oligosaccharides / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
D006023:Glycoproteins; D009844:Oligosaccharides; C028569:oligomannoside; D008358:Mannose