Role of Carbon Metabolism and Virulence of Shigella flexneri

The long-term goal of our research is to understand how human pathogens adapt to the environment of the host. These studies have focused on Shigella flexneri, a human intestinal pathogen that causes dysentery. Because this pathogen must transit the gastrointestinal tract, penetrate the mucous layer, and invade and replicate within intestinal epithelial cells, it must cope with multiple environments. Previous studies from our lab have shown that S. flexneri uses the availability of carbon sources or products of carbon metabolism to detect where they are within the host or external environment. In response to these signals, S. flexneri regulates the expression of genes, including virulence genes, to maximize survival and growth in a particular niche. A mechanistic understanding of these regulatory pathways is needed in order to design effective methods for preventing infection or disease caused by Shigella. Both human intestinal organoids and traditional cell culture methods will be used to study the interactions between S. flexneri and human cells. Bacterial mutants defective in carbon metabolism pathways or in carbon signaling (e.g. ppGpp or CsrA) pathways will be studied in association with human cells to determine the effects on invasion, intracellular replication, and spread of the bacteria to adjacent cells. Dual RNA-Seq will be used to determine the Shigella and host genes that are regulated during infection, and this will guide the construction of additional mutants for analysis. The use of human organoids for the experiments will provide additional information because these contain multiple cell types, which can be separated for analysis, and they have more complete innate immune responses than monolayers of epithelial cells. One innate immune signaling pathway that will be analyzed in detail is Type I interferon (IFN- β) signaling. IFN-β has a mild protective effect against Shigella infection, and fewer bacteria are able to invade cultured Henle cells or intestinal organoids. However, those bacteria that are successful in invading host cells spread more rapidly and cause larger lesions in the presence than in the absence of IFN. This indicates that S. flexneri has a mechanism(s) for not only overcoming interferon-beta induced protective responses but also increasing its virulence in response to interferon in human cell. How S. flexneri evades the protective effects of interferon on host cells will be determinized. Project Number: 4R37AI016935-39 | Fiscal Year: 2025 | NIH Institute/Center: National Institute of Allergy and Infectious Diseases (NIAID) | Principal Investigator: Shelley Payne | Institution: UNIVERSITY OF TEXAS AT AUSTIN, AUSTIN, TX | Award Amount: $391,709 | Activity Code: R37 | Study Section: NSS View on NIH RePORTER: https://reporter.nih.gov/project-details/4R37AI01693539