Protein kinase C dependent development of dendritic cells.

Abstract

Abstract Dendritic cells (DC) are professional antigen presenting cells that are important activators of adaptive immune responses and play a role in the activation of CD8+ T cells that target tumor cells. Our lab has also previously shown that protein kinase C (PKC) βII is essential for DC differentiation and that tumor derived factors, particularly IL-6, inhibit DC differentiation by repressing the expression of PKCβII through a Stat3 dependent mechanism. However, the pathways activated downstream of PKCβII during DC differentiation have yet to be fully characterized. To study this, we used the K562 cell line, which differentiates into DCs with addition of PMA, a known chemical activator of conventional PKC isoenzymes. We have also shown previously that PMA specifically activates PKCβII in K562 cells. Addition of PMA to K562 cells showed the activation of the ERK1/2 and NFκB pathways, including both the canonical and non-canonical NFκB pathways. Chemical inhibition of either the ERK1/2 or NFκB pathway yielded immature DCs with a reduced capacity to stimulate T-cell proliferation when incubated with PMA. Inhibition of ERK1/2 also showed a change in levels of RelB, a NFκB transcription factor, with PMA treatment and during PMA induced DC differentiation. Our lab has also shown that matured DCs reduce Foxo3a protein levels with the stimulation of CD80/CD86 through an Akt dependent mechanism. Inhibition of either the ERK1/2 or NFκB pathways showed an increase in Foxo3a levels, indicating a role for the ERK1/2 and NFκB pathways in Foxo3a regulation during differentiation into mature DCs outside of Akt. Taken together, these results show an integral role for both the ERK and NFκB pathways downstream of PKCβII activation during DC differentiation.