Cloning and characterization of Siglec-10, a novel sialic acid binding member of the Ig superfamily, from human dendritic cells

The Siglecs (sialic acid-binding Ig-like lectins) are a subfamily of I-type lectins, which specifically recognize sialic acids. Nine members of the fa mily have been identified thus far. We have obtained a novel cDNA clone fro m a human dendritic cell cDNA library encoding a protein with sequence and structural features of the Siglec family, hence designated as Siglec-10. Th e full-length Siglec-10 cDNA encodes a type I transmembrane protein contain ing four extracellular immunoglobulinlike domains, a transmembrane region, and a cytoplasmic tail with two classical immunoreceptor tyrosine-based inh ibitory motifs. The N-terminal V-set Ig domain has most of the amino acid r esidues typical of the Siglecs. Siglec-10 shows the closest homology to Sig lec-5 and Siglec-3/CD33. Various cells and cell lines including monocytes a nd dendritic cells express Siglec-10. High levels of mRNA expression were s een in peripheral blood leukocytes, spleen, and liver. When expressed on CO S-7 cells, Siglec-10 was able to bind human red blood cells and soluble sia loglycoconjugates in a sialic acid-dependent manner. The identification of Siglec-1-0 as a new Siglec family member and its expression profile, togeth er with its sialic acid-dependent binding capacity, suggest that it may be involved in cell-cell recognition by interacting with sialylated ligands ex pressed on specific cell populations.