Infection of Immune Competent Macrophages Expressing Functional Slc11a1 Alters Global Gene Expression, Regulation of Metal Ions, and Infection Outcomes

Janiszewski, Lara

Graduate Thesis Or Dissertation

Infection of Immune Competent Macrophages Expressing Functional Slc11a1 Alters Global Gene Expression, Regulation of Metal Ions, and Infection Outcomes Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/3x816n988

Abstract

Nutritional immunity involves cellular and physiological responses to invading pathogens, such as limiting iron availability, increasing exposure to bactericidal copper, and manipulating zinc to restrict the growth of pathogens. Manipulation of zinc at the host-pathogen interface depends on both the pathogen’s identity and the nature of the host cell. Here I examine infection of bone marrow-derived macrophages from 129S6/SvEvTac mice by Salmonella Typhimurium. Unlike Balb/c and C57BL/6 mice, 129S6/SvEvTac mice possess a functional Slc11a1 (Nramp-1), a phagosomal transporter of divalent cations. I carried out global RNA sequencing upon treatment with live or heat-killed Salmonella at 2 Hrs and 18 Hrs post-infection and observed widespread changes in metal transport, metal-dependent, and metal homeostasis genes, suggesting significant remodeling of iron, copper, and zinc availability by host cells. Changes in host cell gene expression suggest infection increases cytosolic zinc while simultaneously limiting zinc within the phagosome. Using a genetically encoded sensor, I demonstrate that cytosolic labile zinc increases 36-fold 12 hrs post-infection. Further, manipulation of zinc in the media alters bacterial clearance and replication, with zinc depletion inhibiting both processes. Comparing my results to published data on infection of C57BL/6 macrophages revealed notable differences in metal regulation and the global immune response, with 129S6 macrophages transitioning from M1 to M2 polarization over the course of infection and showing signs of recovery. My results reveal that functional Slc11a1 profoundly affects the transcriptional landscape upon infection. Further, my results suggest that manipulation of zinc at the host-pathogen interface is more nuanced than that of iron or copper. 129S6 macrophage leverage intricate means of manipulating zinc availability and distribution to limit the pathogen’s access to zinc while simultaneously ensuring sufficient zinc to support the immune response.

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