title: Mutant of Chinese hamster ovary cells with altered mannose 6-phosphate receptor activity is unable to synthesize mannosylphosphoryldolichol.
abstract: B4-2-1 is a Chinese hamster ovary cell mutant previously isolated and characterized as deficient in mannose 6-phosphate receptor activity. We show here that B4-2-1 is a pleiotropic mutant, defective in biosynthesis of asparagine-linked oligosaccharides, B4-2-1 is unable to synthesize mannosylphosphoryldolichol; the consequences of this defect on glycosylation are (i) biosynthesis of one major lipid-linked oligosaccharide, characterized by its resistance to endoglycosidase H and decreased size; this oligosaccharide is similar to a minor species of lipid-liked oligosaccharide found in parental cells; (ii) transfer of this oligosaccharide to newly synthesized proteins; and (iii) absence of normal "high-mannose" oligosaccharides on mature glycoproteins isolated from B4-2-1; glycoproteins from the mutant contain complex oligosaccharides as well as endoglycosidase H-resistant, alpha-mannosidase-sensitive species. While the glycosylation defect may alter adversely the function of several glycoproteins in the mutant, including that of the mannose 6-phosphate receptor, it appears to have no effect on the formation or function of the mannose 6-phosphate recognition marker on acid hydrolases of B4-2-1.
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004287:Dolichol Monophosphate Mannose / Q000096:biosynthesis*; D005260:Female; D006600:Hexosephosphates / Q000235:genetics*; D008360:Mannosephosphates / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D010053:Ovary; D010641:Phenotype; D011105:Polyisoprenyl Phosphate Sugars / Q000096:biosynthesis*
chemical_list: D006600:Hexosephosphates; D008360:Mannosephosphates; D011105:Polyisoprenyl Phosphate Sugars; D004287:Dolichol Monophosphate Mannose