Isolation, Detection, and Ligand Binding Specificity of a Lectin Uniquely Found in Rat Kupffer Cells

Abstract

The rat Kupffer cell receptor was originally isolated as a result of studies examining the clearance to liver of fucose-containing glycoproteins from the blood of rats and mice (Prieels et al. 1978; Furbish et al. 1980; Lehrman et al. 1986b). In order to isolate the receptor or receptors involved in this clearance process, Triton X-100 extracts of rat liver were chromatographed on an affinity adsorbent of the neoglycoprotein L-fucose-β-BSA conjugated to agarose. Three proteins were specifically retained on this column: one protein of M_r = 32 000 corresponding to the mannose/N-acetylglucosamine lectin (Mizuno et al. 1981) thought to be involved in antibody-independent defensive reactions against pathogens (Ikeda et al. 1987; Ezekowitz et al. 1988); a second protein of M_r = 162 000 − 180 000 corresponding to the mannose receptor (Haltiwanger and Hill 1986) involved in the receptor-mediated endocytosis of mannose-containing glycoconjugates (Haltiwanger et al. 1986; Taylor et al. 1990) and phagocytosis of yeast cells (Ezekowitz et al. 1990); and the third protein, made up of two polypeptides of M_r = 88 000 and 77 000 originally named the fucose-binding protein to distinguish it from other hepatic lectins (Lehrman and Hill 1986). The lower molecular weight species is now known to be a proteolytic degradation product of the higher molecular weight species (Hoyle and Hill 1988) and this protein has been renamed the Kupffer cell receptor since immunofluorescence staining of liver thin sections and immunoblots of other cell and tissue types indicated that it is expressed uniquely in Kupffer cells, the resident liver macrophages (Haltiwanger et al. 1986).