NF-κB Mediates Tumor Necrosis Factor α-Induced Expression of Optineurin, a Negative Regulator of NF-κB

Optineurin is a ubiquitously expressed multifunctional cytoplasmic protein encoded by OPTN gene. The expression of optineurin is induced by various cytokines. Here we have investigated the molecular mechanisms which regulate optineurin gene expression and the relationship between optineurin and nuclear factor kappa B (NF-kappa B). We cloned and characterized human optineurin promoter. Optineurin promoter was activated upon treatment of HeLa and A549 cells with tumor necrosis factor alpha (TNF alpha). Mutation of a putative NF-kappa B-binding site present in the core promoter resulted in loss of basal as well as TNF alpha-induced activity. Overexpression of p65 subunit of NF-kappa B activated this promoter through NF-kappa B site. Oligonucleotides corresponding to this putative NF-kappa B-binding site showed binding to NF-kappa B. TNF alpha-induced optineurin promoter activity was inhibited by expression of inhibitor of NF-kappa B (kappa B alpha) super-repressor. Blocking of NF-kappa B activation resulted in inhibition of TNF alpha-induced optineurin gene expression. Overexpressed optineurin partly inhibited TNF alpha-induced NF-kappa B activation in Hela cells. Downregulation of optineurin by shRNA resulted in an increase in TNF alpha-induced as well as basal NF-kappa B activity. These results show that optineurin promoter activity and gene expression are regulated by NF-kappa B pathway in response to TNF alpha. In addition these results suggest that there is a negative feedback loop in which TNF alpha-induced NF-kappa B activity mediates expression of optineurin, which itself functions as a negative regulator of NF-kappa B.