Galectins in Invertebrates with a focus on Caenorhabditis elegans

Abstract

Galectins are a family of β-galactoside-binding lectins widely distributed among animals and fungi, and Galβ1-4GlcNAc is considered the major recognition unit of vertebrate galectins. On the other hand, more than 10 galectins have been reported in Caenorhabditis elegans that belong to the invertebrate class and these C. elegans galectins have been confirmed to have affinity for Galβ1-4GlcNAc. However, the glycan structure differs among species and glycan containing Galβ1-4GlcNAc has not been reported in C. elegans so far. Therefore, the endogenous ligands of C. elegans galectins remained undetermined. Recent studies uncovered that the structures of endogenous ligand glycans of C. elegans galectins are different from those of vertebrate galectins, for e.g., N-glycan containing Galactoseβ1-4 fucose epitope which is not found in vertebrates. Further, C. elegans galectins play a role in host defense against infection and oxidative stress. The roles of mammalian galectins in host defense have been explored in recent years. Taken together, one of the fundamental functions of galectins is possibly host defense because both C. elegans and mammalian galectins function in host defense despite alterations of their ligand structure in the evolutionary process.