Protein kinase C activates multiple pathways to induce dendritic cell differentiation

Abstract

Abstract Dendritic cell (DC) differentiation is a complex process that requires multiple signaling pathways to induce this response. Tumor derived factors can block this process, and one way in which this occurs is through repression of the protein kinase C (PKC) isoform PKCβ at the gene level. However, the role PKCβ plays in DC differentiation has yet to be fully characterized. To address this question, we used the K562 cell line, which our lab and others has shown to be capable of differentiating into DCs with PMA. Inhibition of either the ERK or NFκB pathways in the presence of PMA led to DCs that were unable to activate T-cells. Upon further examination of either pathway, we uncovered novel interactions for PKC signaling and ERK or NFκB during the early stages of DC differentiation. Multiple PKCs induced C-Raf activation, in part through RKIP repression. PKC signaling also induced changes in multiple ERK targets, including degradation of Foxo3a, an interaction not shown previously in DCs. PKCβ was the sole PKC isoform required for canonical NFκB signaling through a mechanism involving the CARD11 complex and PKCβ was required for CARD11 complex formation. However, the IKK kinase TAK1 was not required for downstream NFκB signaling, as opposed to its established role in B-cell and T-cell receptor induced NFκB signaling, indicating an alternative mechanism by which PKCβ induces NFκB signaling. PKCβ was also required for non-canonical NFκB signaling outside of the established TRAF and cIAP cascade. We also found crosstalk between the ERK and NFκB pathways at both protein-protein interaction and protein expression levels. Taken together, these results indicate PKC as an important signaling node for DC differentiation.