Catabolic pathway of oligosaccharide-diphospho-dolichol. Study of the fate of the oligosaccharidic moiety in mouse splenocytes

Abstract : Metabolic labelling of mouse splenocytes with radioactive mannose indicates that the glycosylation process is accompanied by the release of soluble oligomannoside material. Chase experiments with an excess of unlabelled mannose indicate that the radioactivity is mainly chased from oligosaccharide-PP-Dol (PP-Dol = diphosphodolichol): 10% is recovered as (Man)9(GlcNAc)2-P, (Man)9(GlcNAc)2, (Man)9GlcNAc and (Man)5GlcNAc, and 90% is rapidly degraded further. Tunicamycin inhibits both oligosaccharide-PP-Do1 synthesis and the formation of the oligosaccharide material to the same extent. The results thus indicate that these soluble oligomannoside structures represent the main steps of the oligosaccharide-PP-Do1 catabolic pathway, starting with the cleavage of the diphosphate bond. However, it cannot be excluded that part of this material is released from newly formed glycoproteins. The soluble oligomannoside material does not contain glucose residues despite the fact that part of the oligosaccharide-PP-Do1 is glucosylated and it was shown, by the use of glucosidase I inhibitors (castanospermine, deoxynojirimycin) that, after cleavage, the glycan moiety of glucosylated oligosaccharide- PP-Do1 is first rapidly deglucosylated. These experiments provide a physiological basis to our previous results obtained in vitro and allow the definition of further steps in the catabolic pathway of oligosaccharide-PP-Dol.
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René Cacan, Roméo Cecchelli, André Verbert. Catabolic pathway of oligosaccharide-diphospho-dolichol. Study of the fate of the oligosaccharidic moiety in mouse splenocytes. European Journal of Biochemistry, Wiley, 1987, 166, p. 469-474. ⟨hal-00528206⟩

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