An antibody to p16INK4A recognizes a modified form of galectin-3

Galectin-3 is a carbohydrate binding protein involved in multiple processes including cell-cycle regulation and apoptosis, The ability of galectin-3 t o protect cells from apoptosis is dependent upon a region of the protein kn own as a BH-1 domain for its homology to the anti-apoptotic protein Bcl-2, Here, we show that a monoclonal antibody (MAb) to the human tumor suppresso r protein p16INK4A recognizes a post-translationally modified form of human galectin-3, The modified form is detectable in only a subset of cell types expressing galectin-3, indicating that the modification is cell-type-speci fic. Although there is little amino acid sequence homology between p16INK4a and galectin-3, we show by epitope mapping that the modification directly affects the structure of galectin-3's BH-1 domain. Elucidation of the natur e of this modification might provide further insight into galectin-3 functi on.