Interaction of SOCS3 with NonO attenuates IL-1beta-dependent MUC8 gene expression

The intracellular negatively regulatory mechanism which affects IL-1β-induced MUC8 gene expression remains unclear. We found that SOCS3 overexpression suppressed IL-1β-induced MUC8 gene expression in NCI-H292 cells, whereas silencing of SOCS3 restored IL-1β-induced MUC8 gene expression. Sequentially activated ERK1/2, RSK1, and CREB by IL-1β were not affected by SOCS3, indicating that SOCS3 has an independent mechanism of action. Using immunoprecipitaion and nano LC mass analysis, we found that SOCS3 bound NonO (non-POU-domain containing, octamer-binding domain protein) in the absence of IL-1β, whereas IL-1β treatment dissociated the direct binding of SOCS3 and NonO. A dominant-negative SOCS3 mutant (Y204F/Y221F) did not bind to NonO. Interestingly, SOCS3 overexpression dramatically suppressed MUC8 gene expression in cells transfected with wild-type or siRNA of NonO. Moreover, silencing of SOCS3 dramatically increased NonO-mediated MUC8 gene expression caused by IL-1β compared to NonO overexpression alone, suggesting that SOCS3 acts as a suppressor by regulating the action of NonO.