Galectins: A New Family of Regulators of Inflammation

Galectins are members of an animal lectin family defined by shared consensus amino acid sequences and affinity for beta -galactose-containing oligosaccharides. This is an evolutionarily highly conserved family and homologues exist in lower organisms such as nematodes and sponges. In mammals, 10 members have been designated as galectins (galectin-1 through -10); a large number of additional members are likely to be discovered and many identifiable homologues are already present in the published database. The family can be subdivided into prototype (galectin-1, -2, -5, -7, and -10), existing as monomers or homodimers consisting of one carbohydrate-recognition domain (CRD); chimera type (galectin-3), containing a nonlectin part connected to a CRD; and tandem repeat type (galectin-4, -6, -8, and -9), composed of two distinct but homologous CRDs in a single polypeptide chain. Proteins containing sequence similarities with galectins but without demonstrable lectin activity also exist. For example, a novel protein structurally related to galectins, but lacking beta -galactoside-binding activity, has been identified in the lens and designated GRIFIN (galectin-related interfiber protein). Therefore, there exists a galectin superfamily, members of which may or may not possess lectin properties. There are a number of reviews dealing with various aspects of this family and this review focuses on the roles of this family in inflammation.