Identification and analysis of dominant negative mutants of RAIDD and PIDD.

Caspases are cysteine proteases that are essential during the initiation and execution of apoptosis and inflammation. The formation of large oligomeric protein complexes is critical to the activation of caspases in apoptotic and inflammatory signaling pathways. These oligomeric protein complexes function as a platform to recruit caspases, which leads to caspase activation via a proximity-induced mechanism. One well-known oligomeric caspase-activating complex is the PIDDosome for caspase-2 activation, which is composed of 3 protein components, PIDD, RAIDD and Caspase-2. Despite the significant role that caspase-2 activated by PIDDosome plays during genotoxic stress-induced apoptosis, the oligomerization mechanism and the method by which the caspase-activating process is mediated by the formation of PIDDosome is currently not well understood. Here, we show that the assembly mechanism of the core of PIDDosome is time-dependent and salt concentration-dependent. In addition, we demonstrate that point mutations on RAIDD (R147E) and on PIDD (Y814A) exert a dominant negative effect on the formation of the PIDDosome, and that this effect cannot be applied after the PIDDosome has been formed.