Extension of lipid-linked oligosaccharides is a high-priority aspect of the unfolded protein response: Endoplasmic reticulum stress in Type I congenital disorder of glycosylation fibroblasts

Jie Shang, Christian Körner, Hudson Freeze, Mark A. Lehrman

Research output: Contribution to journalArticlepeer-review

40 Scopus citations

Abstract

Asparagine (N)-linked glycans on endoplasmic reticulum (ER) glycoproteins have critical roles in multiple facets of protein folding and quality control. Inhibition of synthesis of lipid-linked oligosaccharides (LLOs), the precursors of N-linked glycans, causes glycoprotein misfolding. This results in ER stress and triggers the unfolded protein response (UPR), which consists of a set of adaptive events, or "aspects," including enhanced extension of LLO intermediates. Type I congenital disorders of glycosylation (CDGs) are characterized by diminished LLO synthesis and aberrant N-glycosylation. Such defects would be predicted to cause chronic ER stress with continuous UPR activation. We employed a quantitative pharmacological approach with dermal fibroblasts to show that (1) compared with three other well-known UPR aspects (transcriptional activation, inhibition of translation, and cell death), LLO extension was the most sensitive to ER stress; and (2) Type I CDG cells had a mild form of chronic ER stress in which LLO extension was continuously stress-activated, but other aspects of the UPR were unchanged. To our knowledge, Type I CDGs are the only human diseases shown to have chronic ER stress resulting from genetic defects in the ER quality control system. In conclusion, LLO extension has a high priority in the UPR of dermal fibroblasts. This suggests that cells stimulate N-glycosylation as part of a first line of defense against ER dysfunction. The broader implications of these results for the biological significance of the UPR are discussed.

Original languageEnglish (US)
Pages (from-to)307-317
Number of pages11
JournalGlycobiology
Volume12
Issue number5
DOIs
StatePublished - 2002

Keywords

  • Congenital disorder of glycosylation
  • Endoplasmic reticulum stress
  • Glycosylation
  • Lipid-linked oligosaccharide
  • Unfolded protein response

ASJC Scopus subject areas

  • Biochemistry

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