Welti M Hülsmeier AJ 2014 Deficiency in N-linked protein glycosylation is a long-known characteristic of alcoholic liver disease and congenital disorders of glycosylation. Previous investigations of ethanol-induced glycosylation deficiency demonstrated perturbations in the early steps of substrate synthesis and in the final steps of capping N-linked glycans in the Golgi. The significance of the biosynthesis of N-glycan precursors in the endoplasmic reticulum, however, has not yet been addressed in alcoholic liver disease. Ethanol-metabolizing hepatoma cells were treated with increasing concentrations of ethanol. Transcript analysis of genes involved in the biosynthesis of N-glycans, activity assays of related enzymes, dolichol-phosphate quantification, and analysis of dolichol-linked oligosaccharides were performed. Upon treatment of cells with ethanol, we found a decrease in the final N-glycan precursor Dol-PP-GlcNAc(2) Man(9) Glc(3) and in C95- and C100-dolichol-phosphate levels. Transcript analysis of genes involved in N-glycosylation showed a 17% decrease in expression levels of DPM1, a subunit of the dolichol-phosphate-mannose synthase, and an 8% increase in RPN2, a subunit of the oligosaccharyl transferase. Ethanol treatment decreases the biosynthesis of dolichol-phosphate. Consequently, the formation of N-glycan precursors is affected, resulting in an aberrant precursor assembly. Messenger RNA levels of genes involved in N-glycan biosynthesis are slightly affected by ethanol treatment, indicating that the assembly of N-glycan precursors is not regulated at the transcriptional level. This study confirms that ethanol impairs N-linked glycosylation by affecting dolichol biosynthesis leading to impaired dolichol-linked oligosaccharide assembly. Together our data help to explain the underglycosylation phenotype observed in alcoholic liver disease and congenital disorders of glycosylation. application/pdf https://sonar.ch/global/documents/121103 eng info:eu-repo/semantics/altIdentifier/doi/10.1002/jcb.24713 info:eu-repo/semantics/altIdentifier/pmid/24243557 info:eu-repo/semantics/openAccess Journal of cellular biochemistry. - 2014 ALCOHOLIC LIVER DISEASE CONGENITAL DISORDER OF GLYCOSYLATION DOLICHOL DOLICHOL-LINKED OLIGOSACCHARIDES N-LINKED GLYCOSYLATION Alcohol Dehydrogenase Carbohydrate Conformation Cells, Cultured Cytochrome P-450 CYP2E1 Dolichol Phosphates Dolichols Ethanol Gene Expression Regulation Glycosylation Hepatocytes Hexosyltransferases Humans Inactivation, Metabolic Mannosyltransferases Oligosaccharides Polysaccharides Proteasome Endopeptidase Complex Transferrin Ethanol-induced impairment in the biosynthesis of N-linked glycosylation. http://purl.org/coar/resource_type/c_6501