Deficient glycan extension and endoplasmic reticulum stresses in ALG3-CDG.
J Inherit Metab Dis
; 47(4): 766-777, 2024 Jul.
Article
in En
| MEDLINE
| ID: mdl-38597022
ABSTRACT
ALG3-CDG is a rare congenital disorder of glycosylation (CDG) with a clinical phenotype that includes neurological manifestations, transaminitis, and frequent infections. The ALG3 enzyme catalyzes the first step of endoplasmic reticulum (ER) luminal glycan extension by adding mannose from Dol-P-Man to Dol-PP-Man5GlcNAc2 (Man5) forming Dol-PP-Man6. Such glycan extension is the first and fastest cellular response to ER stress, which is deficient in ALG3-CDG. In this study, we provide evidence that the unfolded protein response (UPR) and ER-associated degradation activities are increased in ALG3-CDG patient-derived cultured skin fibroblasts and there is constitutive activation of UPR mediated by the IRE1-α pathway. In addition, we show that N-linked Man3-4 glycans are increased in cellular glycoproteins and secreted plasma glycoproteins with hepatic or non-hepatic origin. We found that like other CDGs such as ALG1- or PMM2-CDG, in transferrin, the assembling intermediate Man5 in ALG3-CDG, are likely further processed into a distinct glycan, NeuAc1Gal1GlcNAc1Man3GlcNAc2, probably by Golgi mannosidases and glycosyltransferases. We predict it to be a mono-antennary glycan with the same molecular weight as the truncated glycan described in MGAT2-CDG. In summary, this study elucidates multiple previously unrecognized biochemical consequences of the glycan extension deficiency in ALG3-CDG which will have important implications in the pathogenesis of CDG.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Polysaccharides
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Congenital Disorders of Glycosylation
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Endoplasmic Reticulum Stress
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Fibroblasts
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Mannosyltransferases
Limits:
Humans
Language:
En
Journal:
J Inherit Metab Dis
Year:
2024
Document type:
Article
Affiliation country:
United States
Publication country:
EEUU
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ESTADOS UNIDOS
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ESTADOS UNIDOS DA AMERICA
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EUA
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UNITED STATES
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UNITED STATES OF AMERICA
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US
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USA