Hydrophobic Man-1-P derivatives correct abnormal glycosylation in Type I congenital disorder of glycosylation fibroblasts.

Abstract

Patients with Type I congenital disorders of glycosylation (CDG-I) make incomplete lipid-linked oligosaccharides (LLO). These glycans are poorly transferred to proteins resulting in unoccupied glycosylation sequons. Mutations in phosphomannomutase (PMM2) cause CDG-Ia by reducing the activity of PMM, which converts mannose (Man)-6-P to Man-1-P before formation of GDP-Man. These patients have reduced Man-1-P and GDP-Man. To replenish intracellular Man-1-P pools in CDG-Ia cells, we synthesized two hydrophobic, membrane permeable acylated versions of Man-1-P and determined their ability to normalize LLO size and N-glycosylation in CDG-Ia fibroblasts. Both compounds, compound I (diacetoxymethyl 2,3,4,6-tetra-O-acetyl-alpha-D-mannopyranosyl phosphate) (C-I) and compound II (diacetoxymethyl 2,3,4,6-tetra-O-ethyloxycarbonyl-alpha-D-mannopyranosyl phosphate) (C-II), contain two acetoxymethyl (CH2OAc) groups O-linked to phosphorous. C-I contains acetyl esters and C-II contains ethylcarbonate (CO2Et) esters on the Man residue. Both C-I and C-II normalized truncated LLO, but C-II was about 2-fold more efficient than C-I. C-II replenished the GDP-Man pool in CDG-Ia cells and was more efficiently incorporated into glycoproteins than exogenous Man at low concentrations (25-75 mM). In a glycosylation assay of DNaseI in CDG-Ia cells, C-II restored glycosylation to control cell levels. C-II also corrected impaired LLO biosynthesis in cells from a Dolichol (Dol)-P-Man deficient patient (CDG-Ie) and partially corrected LLO in cells from an ALG12 mannosyltransferase-deficient patient (CDG-Ig), whereas cells from an ALG3-deficient patient (CDG-Id) and from an MPDU1-deficient patient (CDG-If) were not corrected. These results validate the general concept of using pro-Man-1-P substrates as potential therapeutics for CDG-I patients.

• Authors: Erik A Eklund, Nabyl Merbouh, Mie Ichikawa, Atsushi Nishikawa, Jessica M Clima, James A Dorman, Thomas Norberg, Hudson H Freeze
• Journal: Glycobiology (Glycobiology) Vol. 15 Issue 11 Pg. 1084-93 (Nov 2005) ISSN: 0959-6658 [Print] England
• PMID: 16079417 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Culture Media
• Mannosephosphates
• Sugar Phosphates
• diacetoxymethyl 2,3,4,6-tetra-O-acetylmannopyranosyl phosphate
• diacetoxymethyl 2,3,4,6-tetra-O-ethyloxycarbonylmannopyranosyl phoshate
• mannose 1-phosphate
• Phosphotransferases (Phosphomutases)
• phosphomannomutase

Topics

• Carbohydrate Conformation
• Carbohydrate Metabolism
• Cell Proliferation (drug effects)
• Congenital Disorders of Glycosylation (metabolism)
• Culture Media (chemistry)
• Dose-Response Relationship, Drug
• Fibroblasts (chemistry, drug effects, metabolism)
• Glycosylation (drug effects)
• Humans
• Mannosephosphates (chemical synthesis, chemistry, pharmacology)
• Mutation
• Phosphotransferases (Phosphomutases) (genetics, metabolism)
• Sugar Phosphates (chemical synthesis, chemistry, pharmacology)
• Time Factors