Galectin 3 and Glial Cells of the CNS: A Fruitful Crosstalk with Remyelinating Potential

Galectins (Gals) are a group of 15 proteins characterized by a highly conserved carbohydrate-recognition domain (CRD) and made up of approximately 130 amino-acids which bind β-galactose in glycoconjugates. Gals are classified into three groups according to their structures [1-3], i.e. proto, chimera and tandem-repeat. Proto Gals, which have a single CRD, include Gal-1, Gal-2, Gal5, Gal-7, Gal-10, Gal-11, Gal-13, Gal-14, and Gal-15. In turn, tandem-repeat Gals contain two similar CRD and comprise Gal-4, Gal-6, Gal-8, Gal-9, and Gal-12. The only member of the chimera class, Gal-3 has three structural domains: (a) the NH2 terminal domain containing serine phosphorylation, important for nuclear localization, secretion and oligomerization; (b) a sequence susceptible to metalloprotease (MMP) cleavage; and (c) a C-terminal domain containing the CRD and an anti-death motif [4,5]. Worth pointing out, the N-terminal domain allows the formation of pentamers upon the interaction of Gal-3 monomers with glycoproteins or glycolipids.