The major subunit of the asialoglycoprotein receptor is expressed on the hepatocellular surface in mice lacking the minor receptor subunit

Item Type:	Article
Title:	The major subunit of the asialoglycoprotein receptor is expressed on the hepatocellular surface in mice lacking the minor receptor subunit
Creators Name:	Braun, J.R. and Willnow, T.E. and Ishibashi, S. and Ashwell, G. and Herz, J.
Abstract:	The mammalian asialoglycoprotein receptor (ASGPR) is located on the sinusoidal membrane of hepatocytes where it binds and endocytoses galactose-terminated glycoproteins (asialoglycoproteins). ASGPR is composed of two highly homologous subunits, termed hepatic lectin 1 and 2. Despite numerous studies the contribution of both subunits to biosynthesis and functional activity of ASGPR in vivo has remained controversial. Mice lacking the murine hepatic lectin (MHL)-2 subunit are viable and fertile without obvious phenotypic abnormalities. In the absence of MHL-2, knockout mice express MHL-1 protein at reduced levels. Here, we examine the intracellular fate and function of this remaining subunit. The results show that MHL-1 reaches the hepatocellular surface in knockout mice but is unable to effectively remove any one of three different radiolabeled ligands within 30 min. A small but detectable residual ligand clearance in knockout mice at 4 h is apparently not mediated by remaining MHL-1. Serum concentrations of galactose-terminating glycoproteins are not elevated in these ASGPR-deficient mice. However, competitive in vitro degradation experiments suggest that other endogenous ASGPR ligands, the nature of which remain to be determined, accumulate in serum of knockout animals.
Keywords:	Asialoglycoprotein Receptor, Asialoglycoproteins, Cell Membrane, Lectins, Liver, Inbred C57BL Mice, Knockout Mice, Phenotype, Radioligand Assay, Cell Surface Receptors, Animals, Mice
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	271
Number:	35
Page Range:	21160-21166
Date:	30 August 1996
Official Publication:	https://doi.org/10.1074/jbc.271.35.21160
PubMed:	View item in PubMed

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