Biosynthesis and turnover of the mannose 6-phosphate receptor in cultured Chinese hamster ovary cells.

摘要: The natural history of the mannose 6-phosphate receptor was examined by radiolabeling cells in monolayers or suspension; isolated immuno- affinity precipitation followed polyacrylamide gel electrophoresis. found to contain asparagine-linked oligosaccharide chains and phosphorylated serine residues. Newly made sensitive endo-beta-N-acetylglucosaminidase H (endo-H) slowly converted a mature endo-H resistant form; phosphate on only. had an apparent molecular weight 215,000 at all times, as determined under reducing denaturing conditions; unreduced greater electrophoretic mobility, suggesting presence intrachain disulfide linkages. synthesis immunoreactive occurred with lag 50 min functional 70 min, indicating requirement for some post-translational event(s) acquisition immunoreactivity binding activity. Maturation oligosaccharides not requisite modification, since deglycosylated bound both antibody insoluble phosphomannan; however, much less detected tunicamycin. Immunoprecipitable [3H]leucine-labeled degraded t1/2 16 h 6 suspension, respectively, whereas 32P lost corresponding 2.3 4 h. A pool cell surface identified separation Percoll gradients well iodination 125I; this similar that total receptor, even saturating concentration ligand. During endocytosis, ligand (beta-galactosidase) 125I-receptor separated, accumulating within lysosomes. These results are consistent current concepts recycling receptor.