Abstract
Siglecs are a family of immunoglobulin superfamily proteins recognizing glycans that contain sialic acid. Most CD33-related Siglecs were thought to recognize sialylated glycans rather promiscuously, while other, more evolutionarily conserved Siglecs recognize glycans with high specificity. However, recent studies have revealed unexpectedly specific glycan recognition by some of the CD33-related Siglecs, such as human Siglec-8 and mouse Siglec-F. Studies of CD22/Siglec-2 and myelin-associated glycoprotein/Siglec-4 suggest that both cis- and trans-ligands may be involved in regulation of Siglec functions. Preferential recognition of specific glycans by some CD33-related Siglecs may imply the presence of specific trans-ligands, and this possibility should be tested by a search for such ligands and biological assays using cellular and/or animal models.
