Neuronal RING finger protein 11 (RNF11) regulates canonical NF-κB signaling

Background: The RING domain-containing protein RING finger protein 11 (RNF11) is a member of the A20 ubiquitin-editing protein complex and modulates peripheral NF-kappa B signaling. RNF11 is robustly expressed in neurons and colocalizes with a population of alpha-synuclein-positive Lewy bodies and neurites in Parkinson disease patients. The NF-kappa B pathway has an important role in the vertebrate nervous system, where the absence of NF-kappa B activity during development can result in learning and memory deficits, whereas chronic NF-kappa B activation is associated with persistent neuroinflammation. We examined the functional role of RNF11 with respect to canonical NF-kappa B signaling in neurons to gain understanding of the tight association of inflammatory pathways, including NF-kappa B, with the pathogenesis of neurodegenerative diseases. Methods and results: Luciferase assays were employed to assess NF-kappa B activity under targeted short hairpin RNA (shRNA) knockdown of RNF11 in human neuroblastoma cells and murine primary neurons, which suggested that RNF11 acts as a negative regulator of canonical neuronal NF-kappa B signaling. These results were further supported by analyses of p65 translocation to the nucleus following depletion of RNF11. Coimmunoprecipitation experiments indicated that RNF11 associates with members of the A20 ubiquitin-editing protein complex in neurons. Site-directed mutagenesis of the myristoylation domain, which is necessary for endosomal targeting of RNF11, altered the impact of RNF11 on NF-kappa B signaling and abrogated RNF11's association with the A20 ubiquitin-editing protein complex. A partial effect on canonical NF-kappa B signaling and an association with the A20 ubiquitin-editing protein complex was observed with mutagenesis of the PPxY motif, a proline-rich region involved in Nedd4-like protein interactions. Last, shRNA-mediated reduction of RNF11 in neurons and neuronal cell lines elevated levels of monocyte chemoattractant protein 1 and TNF-alpha mRNA and proteins, suggesting that NF-kappa B signaling and associated inflammatory responses are aberrantly regulated in the absence of RNF11. Conclusions: Our findings support the hypothesis that, in the nervous system, RNF11 negatively regulates canonical NF-kappa B signaling. Reduced or functionally compromised RNF11 could influence NF-.B- associated neuronal functions, including exaggerated inflammatory responses that may have implications for neurodegenerative disease pathogenesis and progression.