The function of TRADD in signaling through tumor necrosis factor receptor 1 and TRIF-dependent Toll-like receptors

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Abstract
The function of the adaptor protein TRADD is uncertain. Teams led by Pasparakis and Liu solidify TRADD's function in TNF receptor signaling and extend its influence to TRIF-dependent Toll-like receptor pathways. The physiological function of the adaptor protein TRADD remains unclear because of the unavailability of a TRADD-deficient animal model. By generating TRADD-deficient mice, we found here that TRADD serves an important function in tumor necrosis factor receptor 1 (TNFR1) signaling by orchestrating the formation of TNFR1 signaling complexes. TRADD was essential for TNFR1 signaling in mouse embryonic fibroblasts but was partially dispensable in macrophages; abundant expression of the adaptor RIP in macrophages may have allowed some transmission of TNFR1 signals in the absence of TRADD. Although morphologically normal, TRADD-deficient mice were resistant to toxicity induced by TNF, lipopolysaccharide and polyinosinic-polycytidylic acid. TRADD was also required for TRIF-dependent Toll-like receptor signaling in mouse embryonic fibroblasts but not macrophages. Our findings definitively establish the biological function of TRADD in TNF signaling.