Identification of RIP3, a RIP-like kinase that activates apoptosis and NFkB

Curr Biol 1999 May 20;9(10):539-42.

The tumor necrosis factor receptor 1 (TNFR1) and the Fas receptor recruit complexes formed by the interactions between RIP kinase, TRADD, FADD and RAIDD - adaptor proteins that contain death signaling. To identify proteins associated with the TNF signaling pathway, we performed a yeast two-hybrid interaction screen using RIP as bait. We isolated a kinase, RIP3, which shares homology with the kinase domain of RIP and RIP2 (also known as Rick or CARDIAK). RIP3 could be co-immunoprecipitated with RIP, TRAF2, and TNFR1 in mammalian cells. The carboxy-terminal domain of RIP3, like that of RIP, could activate the transcription factor NFkB and induce apoptosis when expressed in mammalian cells. Interestingly, this region shares no significant sequence homology to the death domain of RIP, the caspase-recruiting domain (CARD) of RIP2 or any other apoptosis-inducing domain. As with RIP and RIP2, the kinase domain of RIP3 was not required for either NFkB activation or apoptosis induction. Overexpression of a dominant-negative mutant of RIP3 strongly inhibited the caspase activation, but not the NFkB activation induced by TNFa. Therefore, RIP3 appears to function as an intermediary in TNFa-induced apoptosis.