title: Effect of the threonine analog beta-hydroxynorvaline on the glycosylation and secretion of alpha 1-acid glycoprotein by rat hepatocytes.
abstract: The threonine analog beta-hydroxynorvaline (Hnv) is an inhibitor of asparagine-linked glycosylation. In the presence of the analog hepatocytes synthesized immunoreactive alpha 1-acid glycoprotein with 0-6 oligosaccharide chains. Pulse-chase experiments were conducted to compare the rates of secretion of alpha 1-acid glycoprotein from untreated, tunicamycin-treated, and Hnv-treated cells. Partially glycosylated (1-5 oligosaccharide chains) and unglycosylated (tunicamycin-inhibited) molecules exited the cells more slowly than native alpha 1-acid glycoprotein. In addition, secretion of fully glycosylated (6 oligosaccharide chains) alpha 1-acid glycoprotein was retarded in Hnv-treated cells when compared to controls. The slowest rate of secretion was exhibited by the unglycosylated form from Hnv-treated cells. These results suggest that Hnv-induced changes either in the extent of glycosylation or in the peptide sequence of alpha 1-acid glycoprotein can interfere with its transport through the cell. The major intracellular forms of alpha 1-acid glycoprotein from control and Hnv-treated cells were endoglycosidase H-sensitive and contained Man9-8 GlcNAc2 oligosaccharide structures. The oligosaccharide chains on the secreted molecules from control and Hnv-treated cells were entirely of the endoglycosidase H-resistant, complex type.
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003470:Culture Media; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009961:Orosomucoid / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D011919:Rats, Inbred Strains; D013912:Threonine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D003470:Culture Media; D009961:Orosomucoid; C010994:3-hydroxynorvaline; D013912:Threonine