IκBη, a nuclear IκB protein, positively regulates the NF-κB-mediated expression of proinflammatory cytokines

摘要

NF-kB is a key mediator for inducible transcription of various proinflammatory genes in innate immune responses, and its activity is strictly regulated by several IkB proteins. Although signaling pathways leading from pattern recognition receptors to NF-kB's activation in the cytoplasm have been studied extensively, the detail regulatory mechanisms of NF-κB-mediated transcriptional activity in the nucleus still remain unclear. Here we describe a unique member of the nuclear IkB protein family, IκBη. In a gene expression analysis of dendritic cells, we found a unique gene encoding an uncharacterized protein with ankyrin repeats. As it was structurally related to the IkB family, the protein was named "IκBη" and further characterized in the innate immune response. IκBη was widely expressed in various tissues and predominantly located in the nucleus. Moreover, biochemical analysis showed that IkBi) associated with the p50 subunit of NF-κB. Knockdown of IκBt) by siRNA suppressed the transcription of a subset of NF-κB-mediated proinflammatory cytokines in LPS-stimulated and poly (I:C)-transfected macrophages. These results indicate that IκBη regulates the NF-κB-mediated transcription of a wide variety of proinflammatory genes, playing a crucial role in the regulation of innate immune responses.