Galectins: major signaling modulators inside and outside the cell.

Galectins control cell behavior by acting on different signaling pathways. Most of the biological activities ascribed to these molecules rely upon recognition of extracellular glycoconjugates and establishment of multivalente interactions, which trigger adaptive biological responses. However, galectins are also detected within the cell in different compartments, where their regulatory functions still remain poorly understood. A deeper understanding of the entire galectin signalosome and its impact in cell behavior is therefore essential in order to delineate new strategies to specifically manipulate both galectin expression and function. This review summarizes our current knowledge of the signaling pathways activated by galectins, their glycan dependence and the cellular compartment where they become activated and are biologically relevant.