The soluble form of the cellular prion protein enhances phagocytic activity and cytokine production by human monocytes via activation of ERK and NF-κB

Abstract

The PrPC is expressed in many types of immune cells including monocytes and macrophages, however, its function in immune regulation remains to be elucidated. In the present study, we examined a role for PrPC in regulation of monocyte function. Specifically, the effect of a soluble form of PrPC was studied in human monocytes. A recombinant fusion protein of soluble human PrPC fused with the Fc portion of human IgG1 (designated as soluble PrPC-Fc) bound to the cell surface of monocytes, induced differentiation to macrophage-like cells, and enhanced adherence and phagocytic activity. In addition, soluble PrPC-Fc stimulated monocytes to produce pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6. Both ERK and NF-κB signaling pathways were activated in soluble PrPC-treated monocytes, and inhibitors of either pathway abrogated monocyte adherence and cytokine production. Taken together, we conclude that soluble PrPC-Fc enhanced adherence, phagocytosis, and cytokine production of monocytes via activation of the ERK and NF-κB signaling pathways.