The Cellular Prion Protein Negatively Regulates Phagocytosis and Cytokine Expression in Murine Bone Marrow-Derived Macrophages

The cellular prion protein (PrP(C)) is a glycosylphosphatidylinositol (GPI)-anchored glycoprotein on the cell surface. Previous studies have demonstrated contradictory roles for PrP(C) in connection with the phagocytic ability of macrophages. In the present work, we investigated the function of PrP(C) in phagocytosis and cytokine expression in bone marrow-derived macrophages infected with Escherichia coli. E. coli infection induced an increase in the PRNP mRNA level. Knockout of PrP(C) promoted bacterial uptake; upregulated Rab5, Rab7, and Eea1 mRNA expression; and increased the recruitment of lysosomal-associated membrane protein-2 to phagosomes, suggesting enhanced microbicidal activity. Remarkably, knockout of PrP(C) suppressed the proliferation of internalized bacteria and increased the expression of cytokines such as interleukin-1β. Collectively, our data reveal an important role of PrP(C) as a negative regulator for phagocytosis, phagosome maturation, cytokine expression, and macrophage microbicidal activity.