Electronic Thesis and Dissertation Repository


Master of Science


Microbiology and Immunology


Dr. David E Heinrichs


Macrophages are important mediators of innate immunity and nutritional immunity via modulation of essential nutrients like iron during bacterial infection. Ferroportin (Fpn), an iron-exporting protein, is found on the plasma membrane of macrophages and, if not modulated during phagocytosis, would transport iron into phagosomes and supply phagocytosed bacteria with iron. Interestingly, the fate of Fpn during phagocytosis and bacterial infection remains unknown. We generated a Fpn-GFP fusion protein and, using fluorescence microscopy, demonstrated that, during phagocytosis in RAW264.7 macrophages, Fpn is removed from phagosomes containing IgG-coated beads or Staphylococcus aureus. Further, Fpn is present on Rab5-containing phagosomes but absent from PI(3)P- and LAMP1-positive phagosomes indicating Fpn removal occurs early during phagosome maturation. Co-localization analysis revealed that markers of cellular recycling pathways, Rab4 and transferrin receptor, do not co-localize with Fpn. Thus, our data support the conclusion that macrophages restrict Fpn residence on phagosomes presumably to prevent iron transport into phagosomes.