Characterization of BAG3 cleavage during apoptosis of pancreatic cancer cells.

Caspases are a conserved family of cell death proteases that cleave intracellular substrates at Asp residues to modify their function and promote apoptosis. In this report, we identify BAG3 as a novel caspases substrate. Here, we show that one of these BAG proteins, BAG3, is cleaved during apoptosis. BAG3 cleavage is inhibited by several different caspase inhibitors. The analysis of BAG3 cleavage by recombinant caspase proteins shows that BAG3 is efficiently cleaved by caspase-3, to a smaller extent by caspases-1 and -8, and relatively inefficient by caspase-9. Cleavage of the BAG3 protein occurs in the C-terminal part of the protein majorly at Asp347 (KEVD347 downward arrow S) in vitro and in pancreatic cancer SW1990 and PANC-1 cells undergoing apoptosis. We also demonstrate that unlike cleavage of Bcl-2 and Bcl-XL, cleaved form of BAG3 does not result in pro-apoptotic fragments, however, cleavage of BAG3 lead to loss its per se anti-apoptotic property. This novel regulation of BAG3 may have important implications for its role in apoptosis. (c) 2010 Wiley-Liss, Inc.