The MKK6/p38 mitogen-activated protein kinase pathway is capable of inducing SOCS3 gene expression and inhibits IL-6-induced transcription

In this study we show that activation of p38(MAPK) by IL-6 acts as an inhibitory signal on IL-6-mediated activation of STAT and the alpha (2)-macroglobulin promoter. We analyzed the role of MKK6/p38(MAPK) for IL-6 signal transduction and transcriptional activation of the suppressor of cytokine signaling (SOCS) 3 promoter. Pretreatment of cells with the p38(MAPK)-specific inhibitor SB202190 downregulates the induction of SOCS3-mRNA expression by IL-6. Accordingly, overexpression of a constitutively active MKK6 in HepG2 cells enhanced basal activity or IL-6-induced transcriptional activation of a SOCS3 promoter reporter construct, whereas overexpression of a dominant negative mutant of MKK6 downregulated the IL-6-mediated activation of the SOCS3 promoter. These data indicate that p38(MAPK)-activation is crucial for IL-6-induced SOCS3 expression and downregulation of IL-6-mediated gene induction.