Trafficking of galectin-3 through endosomal organelles of polarized and non-polarized cells.

In epithelial cells, the β-galactoside-binding lectin galectin-3 mediates the non-raft-dependent glycoprotein targeting to the apical membrane domain. In this study, we aimed to identify intracellular compartments involved in the trafficking of galectin-3. By studying fluorescent fusion proteins in living cells, we could show that galectin-3 accumulates intracellularly in acidified endosomes. Total internal reflection fluorescence microscopy studies of the apical surface of polarized MDCK cells revealed that galectin-3 is enriched in tubular and vesicular Rab11-positive recycling endosomes in the vicinity of the apical cell surface. These endosomal organelles are candidate compartments for the association between galectin-3 and exocytic apical cargo.