The p38 MAP kinase inhibitor SB203580 enhances nuclear factor-kappa B transcriptional activity by a non-specific effect upon the ERK pathway

摘要

In the present study we investigated a possible role for the p38 mitogen-activated protein (MAP) kinase pathway in mediating nuclear factor-kappa B (NF-κB) transcriptional activity in the erythroleukaemic cell line TF-1.TF-1 cells stimulated with the phosphatase inhibitor okadaic acid (OA) demonstrated enhanced NF-κB and GAL4p65-regulated transcriptional activity which was associated with elevated p38 phosphorylation. However, pretreatment with the p38 MAPK specific inhibitor SB203580 (1 μM) or overexpression of kinase-deficient mutants of MKK3 or MKK6 did not affect OA-enhanced NF-κB transcriptional potency, as determined in transient transfection assays. In fact, 5 and 10 μM SB203580 enhanced rather than inhibited NF-κB-mediated promoter activity by 2 fold, which was independent of phosphorylation of the p65 subunit.The SB203580-mediated increase in NF-κB transcriptional activity was associated with enhanced phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and c-Jun N-terminal kinase (JNK), but not p38 kinase.Overexpression of kinase-deficient mutants belonging to the ERK1/2, JNK, and p38 pathways showed that only dominant-negative Raf-1 abrogated SB203580-enhanced NF-κB activity. This would implicate the involvement of the ERK1/2 pathway in the enhancing effects of SB203580 on NF-κB-mediated gene transcription.This study demonstrates that the p38 MAP kinase pathway is not involved in the OA-induced activation of NF-κB. SB203580 at higher concentrations activates the ERK pathway, which subsequently enhances NF-κB transcriptional activity.