PKC driven DC differentiation utilizes the NFκB and ERK signaling pathways

Abstract

Abstract A key activator of adaptive immune responses is the dendritic cell (DC), which is a professional antigen presenting cell that has multiple roles in immunity from combating infections to recognizing tumor cells in order to activate T-cell mediated immune responses. Our lab has previously shown that the PKC isoform PKCβII is required for DC differentiation and that tumor derived factors can inhibit PKCβII expression, which in turn inhibits DC differentiation. However, how PKCβII induces DC differentiation and the pathways activated downstream of PKCβII remains to be characterized. In order to study this, we used the K562 cell line, which our lab and others have shown to be capable of differentiating into DCs with the addition of PMA, a known chemical activator of PKCβII. We have shown previously that PMA specifically activates PKCβII in K562 cells and not the other conventional PKC kinases. We found that both the ERK and NFκB pathways are activated by PKCβII in K562 cells. Chemical inhibition of either pathway yielded DCs with a reduced capacity to stimulate T-cell proliferation. Both the canonical and non-canonical NFκB pathways are activated by PKCβII and knockdown of PKCβII shows inhibition of both pathways. The canonical NFκB pathway is activated in an atypical fashion that has previously not been shown for PKCβII. PKC signaling also induced the activity of specific components of the ERK signaling cascade, including the modulation of downstream ERK effectors. Active Ras levels increased with PKC signaling, indicating GEF induced activity not previously associated with PKCβII. Taken together, these results show that PKCβII utilizes the NFκB and ERK signaling pathways and initiates these pathways in a novel manner to induce DC differentiation.