Suppression of LPS-Induced TNF-α Production in Macrophages by cAMP Is Mediated by PKA-AKAP95-p105

Abstract

The activation of macrophages through Toll-like receptor (TLR) pathways leads to the production of a broad array of cytokines and mediators that coordinate the immune response. The inflammatory potential of this response can be reduced by compounds, such as prostaglandin E_2, that induce the production of cyclic adenosine monophosphate (cAMP). Through experiments with cAMP analogs and multigene RNA interference (RNAi), we showed that key anti-inflammatory effects of cAMP were mediated specifically by cAMP-dependent protein kinase (PKA). Selective inhibitors of PKA anchoring, time-lapse microscopy, and RNAi screening suggested that differential mechanisms of PKA action existed. We showed a specific role for A kinase–anchoring protein 95 in suppressing the expression of the gene encoding tumor necrosis factor–, which involved phosphorylation of p105 (also known as Nfkb1) by PKA at a site adjacent to the region targeted by inhibitor of nuclear factor B kinases. These data suggest that crosstalk between the TLR4 and cAMP pathways in macrophages can be coordinated through PKA-dependent scaffolds that localize specific pools of the kinase to distinct substrates.