Involvement of PKCα/β in TLR4 and TLR2 dependent activation of NF-κB

Protein kinase C (PKC)α/β dependent signaling events downstream of TLR4 or TLR2 were investigated in neutrophils stimulated with LPS or PGN. Pretreatment of neutrophils with the structurally distinct PKCα/β inhibitors Gö6976 or GF109203X decreased nuclear translocation of NF-κB and production of the proinflammatory cytokine TNF-α. Inhibition of PKCα/β also prevented LPS or PGN induced phosphorylation of IKKα/β, phosphorylation and degradation of IκB-α, as well as phosphorylation of the p65 subunit of NF-κB. Activation of p38, JNK, and ERK 1/2 in response to TLR2 engagement was diminished in neutrophils in which PKCα/β was inhibited. However, no alteration in the activation of these kinases was found in TLR4 stimulated neutrophils when PKCα/β was blocked. Such results indicate that distinct intracellular signalling pathways leading to MAPK activation are induced by TLR4 and TLR2 stimulation. PKCα/β can regulate NF-κB dependent transcription in neutrophils both by enhancing nuclear translocation of NF-κB and also by stimulating phosphorylation of the p65 subunit.