Suppression of Bcl-xL deamidation in human hepatocellular carcinomas.

Bcl-xL is an antiapoptotic member of the Bcl-2 family, which inhibits apoptosis initiated by various cellular stresses, and has a pivotal role in the survival of tumor cells. Researchers have previously observed elevated expression of Bcl-xL in some human malignancies. In this study, we present evidence that human Bcl-xL is deamidated at asparagines 52 and 66 and that the rate of Bcl-xL deamidation is significantly lower in hepatocellular carcinomas than in normal or adjacent nontumor liver tissues. Because protein deamidation of Bcl-xL imports a complete "loss of function" of this antiapoptotic molecule, the present study indicates that tumor cells may acquire resistance to apoptosis and a survival advantage by suppressing deamidation as well as by increasing the expression of Bcl-xL. Thus, suppression of Bcl-xL deamidation may play a critical role in the regulation of cell death by apoptosis.