Biosynthesis of the human asialoglycoprotein receptor.
The asialoglycoprotein receptor (ASGP-R) isolated from human liver is a single polypeptide of Mr = 46,000. Monospecific polyclonal anti-human ASGP-R antibodies as well as anti-rat ASGP-R antibodies specifically inhibit binding of 125I-asialoorosomucoid to human hepatoma Hep G2 ASGP-R. These anti-ASGP-R antibodies specifically immunoprecipitate the 46,000-Da polypeptide from hepatoma cells labeled biosynthetically with 35S-amino acid. The receptor is initially synthesized as a 40,000-Da precursor which is converted to the mature 46,000-Da species with a t1/2 of approximately 45 min. The precursor species is sensitive to endo-beta-N-acetylglucosaminidase H and becomes resistant coincident with the appearance of the mature 46,000-Da receptor. In addition, the receptor synthesized in the presence of tunicamycin is approximately 34,000 Da. The newly synthesized ASGP-R reaches the cell surface after 45-60 min, where only the mature 46,000-Da species is present. In Hep G2 cells, the ASGP-R has a mean lifetime of approximately 30 h, a value which is unaltered during maximal rates of receptor-mediated endocytosis of ASGP.
D037263:Asialoglycoprotein Receptor; D006528:Carcinoma, Hepatocellular / Q000032:analysis; D006026:Glycoside Hydrolases / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000032:analysis; D008113:Liver Neoplasms; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008970:Molecular Weight; D011956:Receptors, Cell Surface / Q000096:biosynthesis*; D014357:Trypsin / Q000378:metabolism
D037263:Asialoglycoprotein Receptor; D011956:Receptors, Cell Surface; D006026:Glycoside Hydrolases; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D014357:Trypsin