title: Improvement of dolichol-linked oligosaccharide biosynthesis by the squalene synthase inhibitor zaragozic acid.
abstract: The majority of congenital disorders of glycosylation (CDG) are caused by defects of dolichol (Dol)-linked oligosaccharide assembly, which lead to under-occupancy of N-glycosylation sites. Most mutations encountered in CDG are hypomorphic, thus leaving residual activity to the affected biosynthetic enzymes. We hypothesized that increased cellular levels of Dol-linked substrates might compensate for the low biosynthetic activity and thereby improve the output of protein N-glycosylation in CDG. To this end, we investigated the potential of the squalene synthase inhibitor zaragozic acid A to redirect the flow of the polyisoprene pathway toward Dol by lowering cholesterol biosynthesis. The addition of zaragozic acid A to CDG fibroblasts with a Dol-P-Man synthase defect led to the formation of longer Dol-P species and to increased Dol-P-Man levels. This treatment was shown to decrease the pathologic accumulation of incomplete Dol pyrophosphate-GlcNAc(2)Man(5) in Dol-P-Man synthase-deficient fibroblasts. Zaragozic acid A treatment also decreased the amount of truncated protein N-linked oligosaccharides in these CDG fibroblasts. The increased cellular levels of Dol-P-Man and possibly the decreased cholesterol levels in zaragozic acid A-treated cells also led to increased availability of the glycosylphosphatidylinositol anchor as shown by the elevated cell-surface expression of the CD59 protein. This study shows that manipulation of the cellular Dol pool, as achieved by zaragozic acid A addition, may represent a valuable approach to improve N-linked glycosylation in CDG cells.
authors.affiliation: Institute of Physiology, University of Zürich, CH-8057 Zürich, Switzerland.
authors.forename: Micha A
authors.initials: MA
authors.lastname: Haeuptle
authors.forename: Michael
authors.initials: M
authors.lastname: Welti
authors.forename: Heinz
authors.initials: H
authors.lastname: Troxler
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Hülsmeier
authors.forename: Timo
authors.initials: T
authors.lastname: Imbach
authors.forename: Thierry
authors.initials: T
authors.lastname: Hennet
mesh_terms: D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology*; D018957:CD59 Antigens / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D002784:Cholesterol / Q000096:biosynthesis / Q000235:genetics; D018981:Congenital Disorders of Glycosylation / Q000235:genetics / Q000378:metabolism*; D004286:Dolichols / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D013186:Farnesyl-Diphosphate Farnesyltransferase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D008364:Mannosyltransferases / Q000235:genetics / Q000378:metabolism; D009844:Oligosaccharides / Q000096:biosynthesis* / Q000235:genetics; D014233:Tricarboxylic Acids / Q000494:pharmacology*
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D018957:CD59 Antigens; D004286:Dolichols; D004791:Enzyme Inhibitors; D009844:Oligosaccharides; D014233:Tricarboxylic Acids; C051590:CD59 protein, human; C075117:squalestatin 1; D002784:Cholesterol; D008364:Mannosyltransferases; C022755:dolichyl-phosphate beta-D-mannosyltransferase; D013186:Farnesyl-Diphosphate Farnesyltransferase