Bcl-2 regulates the levels of the cysteine proteases ICH and CPP32/Yama in human neuronal precursor cells.

Members of the Bcl-2 family are major regulators of cell death and survival. Bcl-2 has been shown to heterodimerize with the death-inducing protein Bax, but the mechanism of action of Bcl-2 is not fully understood. Here we show, using the human NT-2 neuronal cell line, that overexpression of Bcl-2 leads to dramatic down-regulation of the cysteine proteases ICH and CPP32/Yama, which are directly involved in cell death. In addition, the nuclear enzyme poly(ADP-ribose) polymerase was cleaved in control cells but not in cells overexpressing Bcl-2 following induction of apoptosis. The mRNA levels of ICH and CPP32/Yama were differentially affected by Bcl-2 overexpression, suggesting both transcriptional and post-transcriptional effects of the protein. These results demonstrate novel mechanisms of action of Bcl-2 in influencing the expression of death effectors such as the cysteine proteases. The relative levels of Bcl-2 and of various cysteine proteases ultimately determine survival and death of different cells, including neurons.