NORE1A directs apoptotic switch of TNF signaling through reciprocal modulation of ITCH-mediated destruction of TNFRI and BAX.

NORE1A (RASSF5) is a tumor suppressor of the Ras-association domain family (RASSF) that is commonly inactivated in multiple human cancers. However, the molecular mechanism underlying its growth inhibition function remains largely undefined. Here we report that NORE1A antagonizes tumor necrosis factor receptor I (TNFRI) through the assembly of ITCH-mediated destruction complex to suppress TNF-NF-κB signaling and tumorigenesis. Moreover, NORE1A is identified as a transcription target of NF-κB, which directs an apoptotic switch of TNF effect by blocking ITCH interaction with and ubiquitination of BAX. Mechanistically, NORE1A binds directly to TNFRI and ITCH via the C1 and PPXY domains, respectively to facilitate the formation of ITCH-mediated destruction complex followed by ubiquitination-mediated lysosomal degradation of TNFRI. Through this function, NORE1A suppresses TNF-induced NF-κB-mediated transcription of pro-inflammatory and tumor-promoting genes, epithelial-to-mesenchymal transition, invasion and migration of tumor cells, and also debilitates tumor cell activation of macrophage and fibroblast. While NORE1A suppresses TNF receptor-mediated apoptosis, it activates TNF-induced apoptosis through BAX activation by protecting BAX from ITCH binding and ubiquitination. Cytotoxic response to TNF is substantially attenuated in NORE1A-depleted cells and tumors, and NORE1A-induced tumor regression is highly impeded in BAX-depleted tumors. An inverse correlation is shown between NORE1A and TNFRI expression in both cancer cell lines and primary tumors, and NORE1A effect on survival of cancer patients is strongly associated with expression status of ITCH. Collectively, this study uncovers that NORE1A directs a substrate switch of ITCH favoring TNFRI over BAX to terminate TNF signaling and accelerate apoptosis, illuminating the mechanistic consequence of NORE1A inactivation in tumorigenesis.

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