Dendritic cell differentiation mediated by IRF4 and IRF8 requires PKCβII (P4480)

Abstract

To better understand how Dendritic Cell (DC) subsets are differentiating, we investigated two essential arms of DC differentiation and how they interact to mediate this process. The transcription factors Interferon Regulatory Factor 4 and 8 (IRF4 and IRF8) are critical for DC differentiation, but have varying roles depending on the stimuli. While IRF8 is required for FLT3-L induced plasmacytoid DC differentiation, and IRF4 is required for GM-CSF induced conventional DC differentiation, it is not well characterized how these two molecules are differentially regulated. We found that Protein Kinase C βII (PKCβII) is activated by both FLT3-L and GM-CSF, and that it is required for DC differentiation when either of these stimuli is used to generate DCs from progenitor cells. Since PKCβII and these IRFs are contributing to DC differentiation we hypothesized they were interacting. We discovered that PKCβII upregulates IRF8 when activated by FLT3-L or phorbol ester (PMA, a known activator of PKCβII), and IRF8 upregulation is lost with the addition of a PKCβII inhibitor. Likewise, IRF4 upregulation is induced by PKCβII in cells treated with GM-CSF or PMA, and lost in the presence of a PKCβII inhibitor. We have also found that in IRF8 knockout DCs there are higer levels of PKCβII, suggesting a feedback mechanism by which these IRFs can be autoregulated. Thus, PKCβII regulating these IRFs may be the key to understanding and manipulating DC differentiation.