Involvement of PKCalpha/beta in TLR4 and TLR2 dependent activation of NF-kappaB.

Protein kinase C (PKC)alpha/beta dependent signaling events downstream of TLR4 or TLR2 were investigated in neutrophils stimulated with LPS or PGN. Pretreatment of neutrophils with the structurally distinct PKCalpha/beta inhibitors Go6976 or GF109203X decreased nuclear translocation of NF-kappaB and production of the proinflammatory cytokine TNF-alpha. Inhibition of PKCalpha/beta also prevented LPS or PGN induced phosphorylation of IKKalpha/beta, phosphorylation and degradation of IkappaB-alpha, as well as phosphorylation of the p65 subunit of NF-kappaB. Activation of p38, JNK, and ERK 1/2 in response to TLR2 engagement was diminished in neutrophils in which PKCalpha/beta was inhibited. However, no alteration in the activation of these kinases was found in TLR4 stimulated neutrophils when PKCalpha/beta was blocked. Such results indicate that distinct intracellular signalling pathways leading to MAPK activation are induced by TLR4 and TLR2 stimulation. PKCalpha/beta can regulate NF-kappaB dependent transcription in neutrophils both by enhancing nuclear translocation of NF-kappaB and also by stimulating phosphorylation of the p65 subunit.