Macrophage NR4A nuclear receptors in tuberculosis pathogenesis

PROJECT SUMMARY Alveolar macrophages (AMs) are a critical cell population in the homeostasis of the lung, needing to clear pathogens and debris from the alveoli without compromising long-term lung health. However, our understanding of their unique phenotype and cellular pathways remains incomplete. This is despite their great importance in diseases such as tuberculosis (TB), in which Mycobacterium tuberculosis (M.tb) carves out its niche inside these cells. As one of the leading causes of death from a single infectious agent and becoming increasingly drug-resistant, there is an urgent need for new therapeutic approaches against TB. The overall goal of our laboratory is to identify intracellular master regulators of inflammation and metabolism that dictate human macrophage responses to M.tb and exploit them as potential host-directed therapy targets. Our lab has identified an understudied family of nuclear receptors, the NR4A family, that is highly expressed by human AMs. Previous work as well as our own data reveal a connection between these transcriptional regulators and expression of surface lipid scavenger receptors (SRs) implicated in M.tb pathogenesis. NR4A members are upregulated in response to M.tb infection of macrophages and function to control M.tb growth. The proposed research plan will use a newly developed AM model to investigate the hypothesis that one or more NR4A family members negatively regulate SR expression and therefore lipid uptake, and decrease M.tb growth in human macrophages. The Specific Aims are to: 1) Determine the role of individual NR4A family members in SR expression and lipid uptake in human macrophage models, 2) Determine whether the NR4A family is protective against M.tb infection using macrophage models, and 3) Establish how NR4A family members regulate NFB and PPAR signaling pathways in mediating M.tb macrophage resistance. In addition, this project uses CRISPR (to complement siRNA knockdown) for specific macrophage knockout of single family members to decrease off-target effects. Investigation of the NR4A family may ultimately identify new, druggable host cell targets for TB therapies. This research plan, under Dr. Schlesinger’s mentorship, affords me the ability to learn new scientific techniques, new models to study infectious diseases, detailed data analysis and the training to shape the direction of this project and my career. The training plan outlines career development activities including opportunities to improve my scientific presentation and communication skills, technical skills, critical thinking, and grantsmanship. The research and training will take place at the Texas Biomedical Research Institute with a deep commitment to scientific training, evidenced by numerous journal clubs, seminars and full support of the Texas Biomed Association for Trainees. Texas Biomed has various core facilities, high containment research labs for M.tb work both in vitro and in mice and NHPs, and all resources needed for excellent scientific training. At fellowship completion, I will be prepared to design and perform research independently and move to the next phase of my training.