期刊
GLYCOBIOLOGY
卷 12, 期 5, 页码 307-317出版社
OXFORD UNIV PRESS INC
DOI: 10.1093/glycob/12.5.307
关键词
congenital disorder of glycosylation; endoplasmic reticulum stress; glycosylation; lipid-linked oligosaccharide; unfolded protein response
资金
- NIDDK NIH HHS [DK55615] Funding Source: Medline
- NIGMS NIH HHS [GM55695, GM38545] Funding Source: Medline
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.
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