CD14 is a Member of the Family of Leucine-rich Proteins and is Encoded by a Gene Syntenic with Multiple Receptor Genes

We have isolated and characterized genomic and cDNA clones encoding the murine homolog of the human monocyte/granulocyte cell surface glycoprotein, CD14. As in man, the expression of murine CD14 is limited to the myeloid lineage. The murine and human CD14 genes are highly conserved in their intron-exon organization and nucleotide sequence. Their deduced protein sequences show 66% amino acid identity. In both mouse and man, the CD14 protein contains a repeating (10 times) leucine-rich motif (LXXLXLX) that is also found in a group of heterogeneous proteins from phylogenetically distant species. The CD14 gene has been mapped to mouse chromosome 18 which also contains at least five genes encoding receptors (Pdgfr, Adrb2r, li, Grl-1, Fms). Thus CD14 and the receptor genes form a conserved syntenic group localized on mouse chromosome 18 and human chromosome 5. The inclusion of CD14 in the family of leucine-rich proteins, its expression profile and the murine chromosomal localization support the hypothesis that CD14 may function as a receptor.