ラット肝細胞膜のアポ蛋白E受容体

Abstract

Liver has two distinct lipoprotein receptors; one is apolipoprotein (apo) B, E receptor and the other is apo-E receptor. We have already found that the 60k and 36k proteins in solubilized rat liver membranes bound apo-E HDLc and the latter bound apo-E HDLc in a specific and saturable manner. In this study, we characterize the lipoprotein-binding manner of the 60k proteins.Rat liver membrane was prepared by ultracentrifugation as the 8, 000 to 100, 000×g pellets after the homogenation. The liver membranes were solubilized in the presence of 40mM octylglucoside, and the membranes were fractionated using DE52 chromatography. The 60k proteins were separated from both of the apo-B, E receptor proteins and the 36k proteins using preparative gel electrophoresis. The binding of 125I-apo-E HDLc to the isolated 60k proteins showed a saturable manner, and was inhibited only by apo-E HDLc competitively but not by human LDL and canine HDL. These findings suggest that the 60k proteins are the apo-E receptor.It is, however, remained to be determined whether the 36k proteins are the degradative products of the 60k proteins or the 60k proteins are the dimer of the 36k proteins.