Previous genetic studies of the nematode Caenorhabditis elegans identi
fied three important components of the cell death machinery. CED-3 and
CED-4 function to kill cells, whereas CED-9 protects cells from death
. Here CED-9 and its mammalian homolog Bcl-x(L) (a member of the Bcl-2
family of cell death regulators) were both found to interact with and
inhibit the function of CED-4. In addition, analysis revealed that CE
D-4 can simultaneously interact with CED-3 and its mammalian counterpa
rts interleukin-1 beta-converting enzyme (ICE) and FLICE. Thus, CED-4
plays a central role in the cell death pathway, biochemically linking
CED-9 and the Bcl-2 family to CED3 and the ICE family of pro-apoptotic
cysteine proteases.