Hypoglycosylation of a brain glycoprotein (β-trace protein) in CDG syndromes due to phosphomannomutase deficiency and N-acetylglucosaminyl-transferase II deficiency

Open Access
Publisher Website
Google Scholar
Abstract
Human β-trace protein is a major intrathecally synthesized polypeptide constituent of human cerebrospinal fluid. We have previously shown that this protein is almost quantitatively modified with biantennary complex-type N-linked oli-gosaccharides which show “brain-type” glycosylation characteristics (Hoffmann,A. et al, J. Neurochenu, 63, pp. 2185-2191,1994). In the present study human β-trace protein from the cerebrospinal fluid (CSF) of patients with carbohydrate-deficient glycoprotein syndrome (CDGS) due to phospho-mannomutase (PMM) deficiency and N-acetyl-glucosami-nyltransferase II (GlcNAc-T II) deficiency as well as from control individuals was studied by Western blot analysis. The protein from pooled CSFs was purified by immunoaffinity chromatography. The protein from the five patients with CDGS PMM deficiency showed three protein bands upon SDS-PAGE analysis corresponding to the di-, mono-, and unglycosylated polypeptide forms. Carbohydrate structural analysis of the enzymatically liberated N-glycans was performed applying mapping by HPAEC-PAD, methylation analysis as well as MALD/TOF-MS. Essentially identical oli-gosaccharide structures were detected in β-TP from type I patients and control adult pooled CSF. The β-trace protein from two patients with GlcNAc-T II deficiency showed a single di-N-glycosylated protein band with a significantly lower molecular weight than the di-glycosylated polypeptide from control patients and the β-trace protein from pooled adult CSF. β-TP from GlcNAc-T II deficiency patients shared only three oligosaccharides out of the 13 observed in β-TP from controls or patients with PMM deficiency. The major oligosaccharide structures of the glycoprotein from patients with GlcNAc-T n deficiency were found to be monoanten-nary asialo- or monosialylated lactosamine-type chains with proximal fucose and bisecting GlcNAc.

This publication has 0 references indexed in Scilit: