A cytosolic reductase pathway is required for efficient N-glycosylation of an STT3B-dependent acceptor site

van Lith, M., Pringle, M. A. , Fleming, B., Gaeta, G., Im, J., Gilmore, R. and Bulleid, N. J. (2021) A cytosolic reductase pathway is required for efficient N-glycosylation of an STT3B-dependent acceptor site. Journal of Cell Science, 134(22), jcs259340. (doi: 10.1242/jcs.259340) (PMID:34734627) (PMCID:PMC8645230)

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N-linked glycosylation of proteins entering the secretory pathway is an essential modification required for protein stability and function. Previously, it has been shown that there is a temporal relationship between protein folding and glycosylation, which influences the occupancy of specific glycosylation sites. Here we use an in vitro translation system that reproduces the initial stages of secretory protein translocation, folding and glycosylation under defined redox conditions. We found that the efficiency of glycosylation of hemopexin was dependent upon a robust NADPH-dependent cytosolic reductive pathway, which could also be mimicked by the addition of a membrane impermeable reducing agent. The identified hypoglycosylated acceptor site is adjacent to a cysteine involved in a short range disulfide, which has been shown to be dependent on the STT3B-containing oligosaccharyl transferase. We also show that efficient glycosylation at this site is influenced by the cytosolic reductive pathway acting on both STT3A and STT3B-dependent glycosylation. Our results provide further insight into the important role of the ER redox conditions in glycosylation site occupancy and demonstrate a link between redox conditions in the cytosol and glycosylation efficiency.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Van Lith, Dr Marcel and Fleming, Miss Bethany and Bulleid, Professor Neil and Pringle, Mrs Marie
Authors: van Lith, M., Pringle, M. A., Fleming, B., Gaeta, G., Im, J., Gilmore, R., and Bulleid, N. J.
College/School:College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
Journal Name:Journal of Cell Science
Publisher:Company of Biologists
ISSN (Online):1477-9137
Published Online:04 November 2021
Copyright Holders:Copyright © 2021 The Company of Biologists Ltd
First Published:First published in Journal of Cell Science 134(22): jcs259340
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
190840Protein Folding and Thiol Modification in the Mammalian Endoplasmic ReticulumNeil BulleidWellcome Trust (WELLCOTR)103720/Z/14/ZInstitute of Molecular, Cell & Systems Biology
308212Giorgia Gaeta Vacation StudentshipNeil BulleidMedical Research Scotland (MEDRESSC)VAC-1417-2019Institute of Molecular, Cell & Systems Biology