Lec23 Chinese hamster ovary (CHO) cells have been shown to possess a unique lectin resistance phenotype and genotype compared with previously isolated CHO glycosylation mutants (Stanley, P., Sallustio, S., Krag, S.S., and Dunn, B. (1990) Somatic Cell Mol. Genet. 16, 211-223). In this paper, a biochemical basis for the lec23 mutation is identified. The carbohydrates associated with the G glycoprotein of vesicular stomatitis virus (VSV) grown in Lec23 cells (Lec23/VSV) were found to possess predominantly oligomannosyl carbohydrates that bound strongly to concanavalin A-Sepharose, eluted 3 sugar eq beyond a Man9GlcNAc marker oligosaccharide on ion suppression high pressure liquid chromatography, and were susceptible to digestion with jack bean α-mannosidase. Monosaccharide analyses revealed that the oligomannosyl carbohydrates contained glucose, indicating a defect in α-glucosidase activity. This was confirmed by further structural characterization of the Lec23/VSV oligomannosyl carbohydrates using purified rat mammary gland α-glucosidase I, jack bean α-mannosidase, and 1H NMR spectroscopy at 500 MHz. [3H]Glucose-labeled Glc3Man9GlcNAc was prepared from CHO/VSV labeled with [3H]galactose in the presence of the processing inhibitors castanospermine and deoxymannojirimycin. Subsequently, [3H]Glc2Man9GlcNAc was prepared by purified α-glucosidase I digestion of [3H] Glc3Man9GlcNAc. When these oligosaccharides were used as α-glucosidase substrates it was revealed that Lec23 cells are specifically defective in α-glucosidase I, a deficiency not previously identified among mammalian cell glycosylation mutants.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - 1991|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology