THE TRAF FAMILY OF SIGNAL TRANSDUCERS MEDIATES NF-KAPPA-B ACTIVATION BY THE TRANCE RECEPTOR

Tumor necrosis factor (TNF)-related activation-induced cytokine (TRANC E), a member of the TNF family expressed on activated T-cells, bone ma rrow stromal cells, and osteoblasts, regulates the function of dendrit ic cells (DC) and osteoclasts. The TRANCE receptor (TRANCE-R), recentl y identified as receptor activator of NF-kappa beta (RANK), activates NF-kappa B, a transcription factor critical in the differentiation and activation of those cells. In this report we identify the TNF recepto r-associated factor (TRAF) family of signal transducers as important c omponents of TRANCE-R-mediated NF-kappa B activation. Coimmunoprecipit ation experiments suggested potential interactions between the cytopla smic tail of TRANCE-R with TRAF1, TRAF2, TRAF3, TRAF5, and TRAF6. Domi nant negative forms of TRAF2, TRAF5, and TRAF6 and an endogenous inhib itor of TRAF2, TRAF-interacting protein (TRIP), substantially inhibite d TRANCE-R-mediated NF-kappa B activation, suggesting a role of TRAFs in regulating DC and osteoclast function. Overexpression of combinatio ns of TRAF dominant negative proteins revealed competition between TRA F proteins for the TRANCE-R and the possibility of a TRAF-independent NF-kappa B pathway. Analysis of TRANCE-R deletion mutants suggested th at the TRAF2 and TRAF5 interaction sites were restricted to the C-term inal 93 amino acids (C-region). TRAF6 also complexed to the C-region i n addition to several regions N-terminal to the TRAF2 and TRAF5 associ ation sites. Furthermore, transfection experiments with TRANCE-R delet ion mutants revealed that multiple regions of the TRANCE-R can mediate NF-kappa B activation.