A Novel Cluster of Lectin-like Receptor Genes Expressed in Monocytic, Dendritic and Endothelial Cells Maps Close to the NK Receptor Genes in the Human NK Gene Complex

The NK gene complex is a region on human chromosome 12 containing several families of lectin-like genes including the CD94 and NKG2 NK receptor genes. We report here that the region telomeric of CD94 contains in addition to the LOX-1 gene the novel human DECTIN-1 and the CLEC-1 and CLEC-2 genes within about 100 kb. Sequence similarities and chromosomal arrangement suggest that these genes form a separate subfamily of lectin-like genes within the NK gene complex. DECTIN-1 is selectively expressed in dendritic cells and to a lower extent in monocytes and macrophages. mRNA forms with and without a stalk exon are observed. During functional maturation of dendritic cells the level of DECTIN-1 mRNA is down-regulated several-fold. CLEC-1 is found to be not only expressed in dendritic cells, but also in endothelial cells and in the latter aspect resembles the LOX-1 gene. Whereas recombinant full-length DECTIN-1 and LOX-1 are transported to the cell surface, CLEC-1 proteins accumulate in perinuclear compartments. We propose that this family of lectin-like genes encodes receptors with important immune and/or scavenger functions in monocytic, dendritic and endothelial cells.