IDENTIFICATION OF THE LECTIN-LIKE RECEPTOR FOR OXIDIZED LOW-DENSITY-LIPOPROTEIN IN HUMAN MACROPHAGES AND ITS POTENTIAL ROLE AS A SCAVENGER RECEPTOR

A new receptor for oxidized low-density lipoprotein (LDL), lectin-like oxidized LDL receptor-1 (LOX-1), has recently been cloned from bovine endothelial cells and human lung. A limited tissue-distribution study suggested that the protein was mainly produced by the vascular endoth elium. In the present study we demonstrate that LOX-1 is also expresse d in macrophages, where it may function as a scavenger receptor. LOX-1 was not detected in undifferentiated THP-1 cells or in freshly isolat ed human blood monocytes. However, mature human monocyte-derived macro phages and differentiated THP-1 cells showed high levels of LOX-1 tran scripts. Consistent with these results, immunofluorescence staining an d FAGS analysis demonstrated that LOX-1 protein is expressed on the pl asma membrane of macrophages. Western-blot analysis of membranes from macrophages (but not those from monocytes) identified a single band, w ith an apparent molecular mass of about 40 kDa, that displayed oxidize d LDL-binding activity. These results suggest that differentiation ind uces the expression of LOX-I in macrophages, where it may play a role as a scavenger receptor and/or a receptor for oxidized LDL.