UMMS Affiliation

Department of Biochemistry and Molecular Pharmacology

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Document Type



Amino Acids, Peptides, and Proteins | Biochemistry, Biophysics, and Structural Biology | Carbohydrates | Cellular and Molecular Physiology | Enzymes and Coenzymes


Global inhibition of N-linked glycosylation broadly reduces glycan occupancy on glycoproteins, but identifying how this inhibition functionally impacts specific glycoproteins is challenging. This limits our understanding of pathogenesis in the congenital disorders of glycosylation (CDG). We used selective exo-enzymatic labeling of cells deficient in the two catalytic subunits of oligosaccharyltransferase - STT3A and STT3B - to monitor the presence and glycosylation status of cell surface glycoproteins. We show reduced abundance of two canonical tyrosine receptor kinases - the insulin receptor and insulin-like growth factor 1 receptor (IGF-1R) - at the cell surface in STT3A-null cells, due to decreased N-linked glycan site occupancy and proteolytic processing in combination with increased endoplasmic reticulum localization. Providing cDNA for Golgi-resident proprotein convertase subtilisin/kexin type 5a (PCSK5a) and furin cDNA to wild-type and mutant cells produced under-glycosylated forms of PCSK5a, but not furin, in cells lacking STT3A. Reduced glycosylation of PCSK5a in STT3A-null cells or cells treated with the oligosaccharyltransferase inhibitor NGI-1 corresponded with failure to rescue receptor processing, implying that alterations in the glycosylation of this convertase have functional consequences. Collectively, our findings show that STT3A-dependent inhibition of N-linked glycosylation on receptor tyrosine kinases and their convertases combines to impair receptor processing and surface localization. These results provide new insight into CDG pathogenesis and highlight how the surface abundance of some glycoproteins can be dually impacted by abnormal glycosylation.


Congenital, Convertase, Furin, Glycoproteins, IGF-1R, INSR, Oligosaccharyltransferase, PCSK5, Protein processing, STT3B

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Copyright © 2019. Published by The Company of Biologists Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.

DOI of Published Version



Dis Model Mech. 2019 Jun 5;12(6):dmm039602. pii: dmm.039602. doi: 10.1242/dmm.039602. Link to article on publisher's site

Journal/Book/Conference Title

Disease models and mechanisms

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Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.