A Genome-Wide siRNA Screen Reveals Positive and Negative Regulators of the NOD2 and NF-κB Signaling Pathways

The cytoplasmic receptor NOD2 (nucleotide-binding oligomerization domain 2) senses peptidoglycan fragments and triggers host defense pathways, including activation of nuclear factor kappa B (NF-kappa B) signaling, which lead to inflammatory immune responses. Dysregulation of NOD2 signaling is associated with inflammatory diseases, such as Crohn's disease and Blau syndrome. We used a genome-wide small interfering RNA (siRNA) screen to identify regulators of the NOD2 signaling pathway. Several genes associated with Crohn's disease risk were identified in the screen. A comparison of candidates from this screen with other omics data sets revealed interconnected networks of genes implicated in NF-kappa B signaling, thus supporting a role for NOD2 and NF-kappa B pathways in the pathogenesis of Crohn's disease. Many of these regulators were validated in secondary assays, such as measurement of interleukin-8 secretion, which is partially dependent on NF-kappa B. Knockdown of putative regulators in human embryonic kidney 293 (HEK 293) cells followed by stimulation with tumor necrosis factor-alpha revealed that most of the genes identified were general regulators of NF-kappa B signaling. Overall, the genes identified here provide a resource to facilitate the elucidation of the molecular mechanisms that regulate NOD2- and NF-kappa B-mediated inflammation.