Introduction to galectins

Galectins are a family of proteins defined by their affinity for beta-galactosides and by conserved sequence elements. Ten galectins from mammals are known, as well as many from other phyla including birds, amphibians, fish, nematodes, sponges and fungi. Galectins are unusual among lectins in that they are cytosolic proteins. From the cytosol they may be secreted by non-classical pathways, but they may also be targeted to the nucleus or specific sub-cytosolic sites. Their function in the extracellular compartment has attracted most attention; there they are thought to act by cross-linking beta-galactoside containing glycoconjugates, resulting in modulation of cell adhesion and cell signaling. However, they may also have functions in the cytosol and nucleus. Their non-classical secretory pathways per se, of which little is known in general, is another area of great interest. Although first discovered based on their beta-galactoside binding activity, with the definition of characteristic sequence elements and the advent of molecular biological techniques, galectins are now being discovered in a variety of other interesting ways. Galectins, galectin inhibitors, or anti-galectin antibodies may possibly be used in therapy and diagnosis of cancer and inflammatory disorders.