Identification and quantification of the rat hepatocyte asialoglycoprotein receptor.

Abstract

The asialoglycoprotein receptor from rat liver was purified by solubilization and affinity chromatography on asialoorosomucoid-Sepharose. The preparation yielded 4 distinct polypeptides of MW 40,000-120,000. A monoclonal antibody was prepared that both immunoprecipitates solubilized receptor activity and blocks the binding of galactose-terminal glycoproteins to immobilized receptor. The monoclonal antibody and a rabbit antireceptor antiserum immunoprecipitated all 4 polypeptide species. Peptide analysis by 2-dimensional chromatography of the individual 125I-labeled species showed nearly identical patterns, which also suggested that the 4 polypeptides have a similar primary structure. To identify and quantitate the asialoglycoprotein receptor on the hepatocyte cell surface, intact cells were iodinated with lactoperoxidase, and the solubilized membranes were treated with antireceptor antibody. The MW 55,000 and MW 65,000 species were the major species found. The MW of the surface receptor is probably at least 55,000 and comprises between 1-2% of the iodinated hepatocyte surface protein.