TY - JOUR
T1 - Galactose and N-acetylgalactosamine-specific endocytosis of glycopeptides by isolated rat hepatocytes
AU - Baenziger, Jacques U.
AU - Fiete, Dorothy
N1 - Funding Information:
This investigation was supported by a grant from the National Cancer Institute and by the following companies: Brown and William-son Tobacco Corporation; Philip Morris, Incorporated; R. J. Reynolds Tobacco Company and United States Tobacco Company. J. U. B. is a recipient of a Research Career Development Award from the National Cancer institute.
PY - 1980
Y1 - 1980
N2 - We have examined the kinetics of binding and uptake of iodinated glycoproteins and glycopeptides bearing terminal Gal or GalNAc moieties in an isolated rat hepatocyte system. Asparagine-linked, triantennary complex oligosaccharides with three terminal Gal residues are endocytosed with the same kinetics as asialo-orosomucoid, whereas biantennary, complex oligosaccharides with one or two terminal Gal residues are not endocytosed. Glycopeptides bearing as few as four O-glycosidically-linked Galβ1, 3GalNAc or GalNAc moieties are also rapidly endocytosed, while glycopeptides with one or two more closely spaced moieties are not endocytosed. All the endocytosable glycoproteins and glycopeptides have similar apparent dissociation constants and a similar number of binding sites on the surface of the intact hepatocyte. The ligand-binding properties of the receptor in the plasma membrane of intact cells differ from those of the solubilized receptor, suggesting that interaction with other as yet undefined cellular components confers the ability to discriminate among closely related oligosaccharide structures. This is consistent with a model in which only glycopeptides bearing terminal Gal or GalNAc residues that fall within a restricted spatial relationship can induce a conformational alteration in the receptor which is required for uptake to occur. The endocytosis of a number of glycoproteins such as human asialo-ceruloplasmin can be accounted for by the presence of a single, complex oligosaccharide with the appropriate structure.
AB - We have examined the kinetics of binding and uptake of iodinated glycoproteins and glycopeptides bearing terminal Gal or GalNAc moieties in an isolated rat hepatocyte system. Asparagine-linked, triantennary complex oligosaccharides with three terminal Gal residues are endocytosed with the same kinetics as asialo-orosomucoid, whereas biantennary, complex oligosaccharides with one or two terminal Gal residues are not endocytosed. Glycopeptides bearing as few as four O-glycosidically-linked Galβ1, 3GalNAc or GalNAc moieties are also rapidly endocytosed, while glycopeptides with one or two more closely spaced moieties are not endocytosed. All the endocytosable glycoproteins and glycopeptides have similar apparent dissociation constants and a similar number of binding sites on the surface of the intact hepatocyte. The ligand-binding properties of the receptor in the plasma membrane of intact cells differ from those of the solubilized receptor, suggesting that interaction with other as yet undefined cellular components confers the ability to discriminate among closely related oligosaccharide structures. This is consistent with a model in which only glycopeptides bearing terminal Gal or GalNAc residues that fall within a restricted spatial relationship can induce a conformational alteration in the receptor which is required for uptake to occur. The endocytosis of a number of glycoproteins such as human asialo-ceruloplasmin can be accounted for by the presence of a single, complex oligosaccharide with the appropriate structure.
UR - http://www.scopus.com/inward/record.url?scp=0019159338&partnerID=8YFLogxK
U2 - 10.1016/0092-8674(80)90371-2
DO - 10.1016/0092-8674(80)90371-2
M3 - Article
C2 - 7448875
AN - SCOPUS:0019159338
VL - 22
SP - 611
EP - 620
JO - Cell
JF - Cell
SN - 0092-8674
IS - 2
ER -