dolichols and dolichol-pyrophosphate

In the majority of congenital disorders of glycosylation, the assembly of the glycan precursor GlcNAc(2)Man(9)Glc(3) on the polyprenol carrier dolichyl-pyrophosphate is compromised. Because N-linked glycosylation is essential to life, most types of congenital disorders of glycosylation represent partial losses of enzymatic activity. Consequently, increased availability of substrates along the glycosylation pathway can be beneficial to increase product formation by the compromised enzymes. Recently, we showed that increased dolichol availability and improved N-linked glycosylation can be achieved by inhibition of squalene biosynthesis. This review summarizes the current knowledge on the biosynthesis of dolichol-linked glycans with respect to deficiencies in N-linked glycosylation. Additionally, perspectives on therapeutic treatments targeting dolichol and dolichol-linked glycan biosynthesis are examined.

Topics: Carbohydrate Sequence; Congenital Disorders of Glycosylation; Dolichol Phosphates; Dolichols; Glycosylation; Humans; Polysaccharides

This review deals with the structure and addition of the different types of oligosaccharides to asparagine residues in proteins. This process occurs in several steps, first an oligosaccharide which contains N-acetylglucosamine mannose and glucose is built up joined to dolichyl diphosphate. The oligosaccharide is then transferred to a polypeptide chain, loses its glucose, and is modified by removal of some monosaccharides and addition of others giving rise to a variety of saccharides.

Topics: Acetylglucosamine; Acetylglucosaminidase; Animals; Asparagine; Cells, Cultured; Dolichol Phosphates; Dolichols; Fungi; Glucose; Glycoproteins; Humans; Insecta; Mannose; Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; Models, Biological; Oligosaccharides; Peptides; Plants; Polyisoprenyl Phosphates; Viruses

Citronellyl- and solanesyl-based dolichol linked oligosaccharide (DLO) analogs were synthesized and tested along with undecaprenyl compounds for their ability to inhibit the release of [

Topics: Animals; Dolichol Phosphates; Dolichols; Humans; Liver; Monoterpenes; Oligosaccharides; Phosphoric Diester Hydrolases; Phosphoric Monoester Hydrolases; Polyisoprenyl Phosphate Sugars; Polyisoprenyl Phosphates; Substrate Specificity

In all three domains of life, N-glycosylation begins with the assembly of glycans on phosphorylated polyisoprenoid carriers. Like eukaryotes, archaea also utilize phosphorylated dolichol for this role, yet whereas the assembled oligosaccharide is transferred to target proteins from dolichol pyrophosphate in eukaryotes, archaeal N-linked glycans characterized to date are derived from a dolichol monophosphate carrier, apart from a single example. In this study, glycan-charged dolichol phosphate from the hyperthermophile Pyrococcus furiosus was identified and structurally characterized. Normal and reverse phase liquid chromatography-electrospray ionization mass spectrometry revealed the existence of dolichol phosphate charged with the heptasaccharide recently described in in vitro studies of N-glycosylation on this species. As with other described archaeal dolichol phosphates, the α- and ω-terminal isoprene subunits of the P. furiosus lipid are saturated, in contrast to eukaryal phosphodolichols that present only a saturated α-position isoprene subunit. Interestingly, an additional 1-4 of the 12-14 isoprene subunits comprising P. furiosus dolichol phosphate are saturated, making this lipid not only the longest archaeal dolichol phosphate described to date but also the most highly saturated.

Topics: Archaea; Butadienes; Dolichol Phosphates; Dolichols; Glycosylation; Hemiterpenes; Oligosaccharides; Pentanes; Phosphate Transport Proteins; Polysaccharides; Pyrococcus furiosus

Defects in the synthesis of dolichol-linked oligosaccharide (or lipid-linked oligosaccharide [LLO]) cause severe, multisystem human diseases called type 1 congenital disorders of glycosylation (CDG type 1). LLOs are also involved in another disease, neuronal ceroid lipofuscinosis. Because of the low abundance of LLOs, almost all studies of LLO synthesis have relied upon metabolic labeling of the oligosaccharides with radioactive sugar precursors such as [3H]mannose or [14C]glucosamine, and therefore have been limited almost entirely to cell cultures and tissue slices. A procedure is presented for a facile, accurate, and sensitive non-radioactive method for LLO pathway analysis based on fluorophore-assisted carbohydrate electrophoresis (FACE). It is feasible to analyze almost any component in the LLO pathway with the application FACE, from sugar precursors to mature LLO (Glc3Man9GlcNAc2-P-P-dolichol).

Topics: Animals; Ants; Carbohydrate Sequence; Carbohydrates; Cells, Cultured; CHO Cells; Cricetinae; Cricetulus; Dolichol Phosphates; Dolichols; Electrophoresis; Fluorescent Dyes; Glycosylation; Humans; Molecular Biology; Molecular Sequence Data; Naphthalenesulfonates; Oligosaccharides; Polyisoprenyl Phosphate Sugars; Sensitivity and Specificity; Signal Transduction

Deficiency of GDP-Man:Man1GlcNAc2-PP-dolichol mannosyltransferase (hALG2), is the cause of a new type of congenital disorders of glycosylation (CDG) designated CDG-Ii. The patient presented normal at birth but developed in the 1st year of life a multisystemic disorder with mental retardation, seizures, coloboma of the iris, hypomyelination, hepatomegaly, and coagulation abnormalities. An accumulation of Man1GlcNAc2-PP-dolichol and Man2GlcNAc2-PP-dolichol was observed in skin fibroblasts of the patient. Incubation of patient fibroblast extracts with Man1GlcNAc2-PP-dolichol and GDP-mannose revealed a severely reduced activity of the mannosyltransferase elongating Man1GlcNAc2-PP dolichol. Because the Saccharomyces cerevisiae mutant alg2-1 was known to accumulate the same shortened dolichol-linked oligosaccharides as the patient, the yeast ALG2 sequence was used to identify the human ortholog. Genetic analysis revealed that the patient was heterozygous for a single nucleotide deletion and a single nucleotide substitution in the human ortholog of yeast ALG2. Expression of wild type but not of mutant hALG2 cDNA restored the mannosyltransferase activity and the biosynthesis of dolichol-linked oligosaccharides both in patient fibroblasts and in the alg2-1 yeast cells. hALG2 was shown to act as an alpha1,3-mannosyltransferase. The resulting Manalpha1,3-ManGlcNAc2-PP dolichol is further elongated by a yet unknown alpha1,6-mannosyltransferase.

Topics: Base Sequence; Carbohydrate Metabolism, Inborn Errors; Carbohydrate Sequence; Cell Line; DNA Primers; Dolichol Phosphates; Dolichols; Female; Fibroblasts; Genetic Complementation Test; Glycosylation; Humans; Male; Molecular Sequence Data; Mutagenesis, Site-Directed; Oligosaccharides; Pedigree; Polyisoprenyl Phosphate Monosaccharides; Saccharomyces cerevisiae; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

The age-associated changes in the levels and synthesis of dolichyl phosphate and dolichyl diphosphate derivatives were investigated in brain and liver of 057B1/NNia mice. The total chloroform/methanol (2:1, v/v)-extractable phosphorylated dolichols of brain increased from 1.01 micrograms/g at 3 months to 5.22 micrograms/g at 28 months of age. The long-chain dolichyl diphosphate oligosaccharide (Dol-PP-oligo) levels of brain increased from 0.82 microgram/g in 3 months to 2.8 micrograms/g in 28-month-old animals. However, in liver and in kidney, the levels of these components were unaffected by age. Incorporation of labelled glucose from UDP-glucose into dolichyl phosphate glucose and Dol-PP-oligo in brain microsomes was unaffected by age, whereas, in liver microsomes, the rates of synthesis of both components increased by 50-150%. The increased rate of synthesis and lack of accumulation of Dol-PP-oligo in liver suggest an active utilization and/or catabolism of these glycoprotein precursors. The accumulation of Dol-PP-oligo in aging brain may reflect its decreased utilization for N-glycosylation and/or reduced catabolism.

Topics: Aging; Animals; Brain; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Dolichol Phosphates; Dolichols; Glycoproteins; Mice; Mice, Inbred C57BL; Microsomes; Microsomes, Liver; Phosphorylation; Spectrophotometry, Ultraviolet