Identification of RIP3, a RIP-like kinase that activates apoptosis and NF kappa B

The tumor necrosis factor receptor 1 (TNFR1) and the Pas receptor recruit c omplexes formed by the interactions between RIP kinase, TRADD, FADD and RAI DD - adaptor proteins that contain death domains - which in turn recruit ot her proteins to initiate signaling [1-5], To identify proteins associated w ith 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), RI P3 could be co immunoprecipitated with RIP, TRAF2 and TNFR1 in mammalian ce lls, The carboxy-terminal domain of RIP3, like that of RIP, could activate the transcription factor NF kappa B 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) o f RIP2 [6-8] or any other apoptosis-inducing domain. As with RIP and RIP2, the kinase domain of RIP3 was not required for either NF kappa B activation or apoptosis induction. Overexpression of a dominant-negative mutant of RI P3 strongly inhibited the caspase activation but not the NF kappa B activat ion induced by TNF alpha. Therefore, RIP3 appears to function as an interme diary in TNF alpha-induced apoptosis. (C) Elsevier Science Ltd ISSN 0960-98 22.