Galectin-3 mediates the endocytosis of beta-1 integrins by breast carcinoma cells.

Galectin-3, a beta-galactoside binding lectin, has been demonstrated to play a key role(s) in cell to extracellular matrix interaction. The precise mechanism by which it modulates cellular adhesion is presently unclear and warrants further studies. We hereby report that galectin-3 mediates the endocytosis of beta-1 integrins in a lactose-dependent manner. Interestingly we observed that galectin-3 was also rapidly internalized by the cells via the same pathway and the internalization was completely blocked by lactose. The endocytosis process was temperature dependent and was inhibited by filipin but not chlorpromazine. The endocytosis of galectin-3 and beta-1 integrins by the cells was accompanied by rapid cell spreading due to cytoskeletal reorganization. The data suggest a novel mechanism by which galectin-3 and beta-1 integrins are internalized into breast carcinoma cells via a cavaleolae-like pathway of endocytosis.