The galectins constitute a large family of carbohydrate-binding proteins with specificity for N-acetyl-lactosamine-containing glycoproteins. At least 14 mammalian galectins, which share structural similarities in their carbohydrate recognition domains (CRD), have been identified to date. Galectin-1 has been classified as a prototype galectin (-1, -2, -5, -7, -10, -11, -13, -14), which contains one CRD and exists either as a monomer or a noncovalent homodimer. The chimera galectins (such as Galectin-3) contain one CRD linked to a nonlectin domain, while the tandem-repeat galectins (-4, -6, -8, -9, -12) consist of two CRDs joined by a linker peptide. Galectins lack a classical signal peptide and can be localized to the cytosolic compartments where they have intracellular functions. However, via one or more as yet unidentified non-classical secretory pathways, galectins can also be secreted and function extracellularly. Individual members of the galectin family have different tissue distribution profiles and exhibit subtle differences in their carbohydrate-binding specificities. Each family member may preferentially bind to a unique subset of cell-surface glycoproteins (1-5).
Mouse Galectin-1, also known as beta-galactoside-binding lectin L-14-I, lactose-binding lectin 1, S-Lac lectin 1, galaptin and 14 kDa lectin, is a monomeric or homodimeric prototype galectin that is expressed in a variety of tissues and cells including muscle, heart, lymph nodes, spleen, thymus, macrophages, B cells, T cells, dendritic cells, and tumor cells. It preferentially binds laminin, fibronectin, 90K/Mac-2BP, CD45, CD43, CD7, CD2, CD3, and ganglioside GM1. Galectin-1 modulates cell growth, proliferation and differentiation, either positively or negatively, depending on the cell type and activation status. It controls cell survival by inducing apoptosis of activated T cells and immature thymocytes. It modulates cytokine secretion by inducing Th2 type cytokines and inhibiting pro-inflammatory cytokine production. Galectin-1 can also modulate cell-cell as well as cell-matrix interactions, and depending on the cell type and developmental stage, promote cell attachment or detachment. Galectin-1 has immunosuppressive and anti-inflammatory properties, and has been shown to suppress acute and chronic inflammation and autoimmunity. Mouse and human Galectin-1 share about 88% amino acid sequence similarity (1-6).