PPARγ1 attenuates cytosol to membrane translocation of PKCα to desensitize monocytes/macrophages

Recently, we provided evidence that PKC alpha depletion in monocytes/macrophages contributes to cellular desensitization during sepsis. We demonstrate that peroxisome proliferator-activated receptor gamma (PPAR gamma) agonists dose dependently block PKCa depletion in response to the diacylglycerol homologue PMA in RAW 264.7 and human monocyte-derived macrophages. In these cells, we observed PPAR gamma-dependent inhibition of nuclear factor-kappa B (NF-kappa B) activation and TNF-alpha expression in response to PMA. Elucidating the underlying mechanism, we found PPAR gamma 1 expression not only in the nucleus but also in the cytoplasm. Activation of PPAR gamma 1 wild type, but not an agonist-binding mutant of PPAR gamma 1, attenuated PMA-mediated PKCa cytosol to membrane translocation. Coimmunoprecipitation assays pointed to a protein-protein interaction of PKCa and PPAR gamma 1, which was further substantiated using a mammalian two- hybrid system. Applying PPAR gamma 1 mutation and deletion constructs, we identified the hinge helix 1 domain of PPAR gamma 1 that is responsible for PKCa binding. Therefore, we conclude that PPAR gamma 1-dependent inhibition of PKCa translocation implies a new model of macrophage desensitization.