Galectins: readers of the glycocode that come from the wrong side of the membranes
Galectins were discovered and named based on their affinity for galactose containing glycans, such as typically found on cell surface and intravesicular glycoproteins and glycolipids. Based on such activity, they were at first thought to take part in cell adhesion, and later many other functions due this extracellular activity have been defined (e.g. regulation of cell signaling, glycoprotein trafficking and endocytosis, autophagy).
However, it was also early found that galectins are made as cytosolic proteins, on the “wrong side” of the membranes where there are few galactoside containing glycoconjugates. Galectins have other activities in the cytosol and nucleus (e.g. regulation of apoptosis, signaling pathways, transcription). To reach their carbohydrate ligands, galectins need to be externalized by non-classical pathways. Somewhere in between, they accumulate around disrupted vesicles, possibly as a repair mechanism or as a coupling to autophagy.
Organismal roles in cancer, immunity, inflammation, and fibrosis suggested by studies in animals and humans have stimulated development of galectin inhibitors as therapeutics, and galectin based diagnostics.
Senior Professor in Sabbatical MAYENT ROTHSCHILD - Institut Curie, Lund Unversity
Domain 4 - UMR 3666 / U1143 - Chemical Biology of Membranes and Therapeutic Delivery