Autoproteolysis of PIDD marks the bifurcation between pro-death caspase-2 and pro-survival NF-κB pathway

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Abstract
Upon DNA damage, a complex called the PIDDosome is formed and either signals NF‐κB activation and thus cell survival or alternatively triggers caspase‐2 activation and apoptosis. PIDD (p53‐induced protein with a death domain) is constitutively processed giving rise to a 48‐kDa N‐terminal fragment containing the leucine‐rich repeats (LRRs, PIDD‐N) and a 51‐kDa C‐terminal fragment containing the death domain (DD, PIDD‐C). The latter undergoes further cleavage resulting in a 37‐kDa fragment (PIDD‐CC). Here we show that processing occurs at S446 (generating PIDD‐C) and S588 (generating PIDD‐CC) by an auto‐processing mechanism similar to that found in the nuclear pore protein Nup98/96 and inteins. Auto‐cleavage of PIDD determines the outcome of the downstream signaling events. Whereas initially formed PIDD‐C mediates the activation of NF‐κB via the recruitment of RIP1 and NEMO, subsequent formation of PIDD‐CC causes caspase‐2 activation and thus cell death. A non‐cleavable PIDD mutant is unable to translocate from the cytoplasm to the nucleus and loses both activities. In this way, auto‐proteolysis of PIDD might participate in the orchestration of the DNA damage‐induced life and death signaling pathways.