Endo180, an endocytic recycling glycoprotein related to the macrophage mannose receptor is expressed on fibroblasts, endothelial cells and macrophages and functions as a lectin receptor

Endol80 was previously characterized as a novel, cell type specific, recycl ing transmembrane glycoprotein, This manuscript describes the isolation of a full length human Endol80 cDNA clone which was shown to encode a fourth m ember of a family of proteins comprising the macrophage mannose receptor, t he phospholipase A(2) receptor and the DEC-205/MR6 receptor, This receptor family is unusual in that they contain 8-10 C-type lectin carbohydrate reco gnition domains in a single polypeptide backbone, however, only the macroph age mannose receptor had been shown to function as a lectin, Sequence analy sis of Endol80 reveals that the second carbohydrate recognition domain has retained key conserved amino acids found in other functional C-type lectins . Furthermore, it is demonstrated that this protein displays Ca2+-dependent binding to N-acetylglucosamine but not mannose affinity columns. In order to characterize the physiological function of Endol80, a series of biochemi cal and morphological studies were undertaken. Endol80 is found to be predo minantly expressed in vivo and in vitro on fibroblasts, endothelial cells a nd macrophages, and the distribution and post-translational processing in t hese cells is consistent with Endol80 functioning to internalize glycosylat ed ligands from the extracellular milieu for release in an endosomal compar tment.