Crosstalk between PKCζ and the IL4/Stat6 pathway during T-cell-mediated hepatitis

Abstract

PKCζ is required for nuclear factor κ-B (NF-κB) activation in several cell systems. NF-κB is a suppressor of liver apoptosis during development and in concanavalin A (ConA)-induced T-cell-mediated hepatitis. Here we show that PKCζ-/- mice display inhibited ConA-induced NF-κB activation and reduced damage in liver. As the IL-4/Stat6 pathway is necessary for ConA-induced hepatitis, we addressed here the potential role of PKCζ, in this cascade. Interestingly, the loss of PKCζ severely attenuated serum IL-5 and liver eotaxin-1 levels, two critical mediators of liver damage. Stat6 tyrosine phosphorylation and Jak1 activation were ablated in the liver of ConA-injected PKCζ-/- mice and in IL-4-stimulated PKCζ-/- fibroblasts. PKCζ interacts with and phosphorylates Jak1 and PKCζ activity is required for Jak1 function. In contrast, Par-4-/- mice have increased sensitivity to ConA-induced liver damage and IL-4 signaling. This unveils a novel and critical involvement of PKCζ in the IL-4/Stat6 signaling pathway in vitro and in vivo.