Plasmodium falciparum glycosylphosphatidylinositols (GPIs) have been proposed as malaria pathogenic factors based on their ability to induce proinflammatory responses in macrophages and malaria-like symptoms in mice. Parasite GPIs induce the production of inflammatory cytokines by activating the mitogen-activated protein kinase (MAPK) and NF-κB signaling pathways. Importantly, inhibition of the extracellular-signal-regulated kinase (ERK) pathway upregulates a subset of cytokines, including IL-12. We investigated the role of nuclear transcription factor, IκB-Î¶, in the GPI-induced dysregulated expression of IL-12 on inhibition of the ERK pathway. GPIs efficiently induced the expression of IκB-Î¶ in macrophages regardless of whether cells were pretreated or untreated with ERK inhibitors, indicating that ERK has no role in IκB-Î¶ expression. However, on ERK inhibition followed by stimulation with GPIs, NF-κB binding to Il12b promoter κB site was markedly increased, suggesting that the ERK pathway regulates Il12b transcription. Knockdown of IκB-Î¶ using siRNA markedly reduced the GPI-induced IL-12 production and abrogated the dysregulated IL-12 production in ERK inhibited cells. Together these results demonstrate that ERK modulates IL-12 expression by regulating IκB-Î¶-dependent binding of NF-κB transcription factors to Il12b gene promoter. Additionally, our finding that IκB-Î¶ can be knocked down efficiently in primary macrophages is valuable for studies aimed at gaining further insights into IκB-Î¶ function.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Clinical Biochemistry
- Cell Biology