Functional and molecular characterization of host cell microRNAs controlling Salmonella infection

• Applicant: Dr. Ana Sofia Bregieiro Eulalio, Ph.D.
• Subject Area: Parasitology and Biology of Tropical Infectious Disease Pathogens
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 247690251

Bacterial pathogens manipulate a vast range of host cellular functions to ensure their survival and replication. A still largely unexplored question in host-pathogen interactions is the interplay between bacteria and host cell microRNAs. Considering that microRNAs play a pervasive role in the modulation of host gene expression, it is perhaps not surprising that pathogens may have evolved mechanisms to subvert the microRNA pathway for their own benefit and, conversely, that this pathway may be used by infected cells to mount a proper antibacterial response.This project aims to characterize the molecular mechanisms by which selected microRNAs influence Salmonella infection, as well as the reciprocal effect of Salmonella infection on the regulation of the abundance of these microRNAs. Recently, using a functional high-throughput screening of microRNA libraries, we have determined that microRNAs play a critical role in Salmonella infection. Among other microRNAs, we have identified miR-744, let-7i*, and the miR-15 and miR-181 microRNA families as microRNAs that very efficiently inhibit Salmonella infection. Interestingly, the analysis of microRNA expression of Salmonella-infected cells by deep-sequencing demonstrated that upon Salmonella infection the abundance of these microRNAs in decreased, suggesting a dynamic host-pathogen interplay.In this research project, we will characterize the mechanisms by which miR-744, let-7i*, and the miR-15 and miR-181 microRNA families regulate infection by Salmonella. This will involve the evaluation of the effect of the microRNAs during multiple steps of infection and in various target cells, namely epithelial cells and macrophages. Using a combination of experimental and bioinformatic approaches, we will also identify and characterize the targets of these microRNAs that are critical for inhibiting Salmonella infection. We will also clarify the molecular mechanisms employed by Salmonella to downregulate the levels of these microRNAs. We will identify the bacterial stimulus responsible for triggering the microRNA regulation, determine if this regulation occurs at the level of microRNA biogenesis and/or stability, and determine whether this mechanism is conserved in other cell types. Furthermore, we will also determine if bacterial effector proteins are involved in this process, which will be an important finding, since to date no bacterial effectors have been shown to subvert the microRNA pathway of host mammalian cells. Overall, this project will substantially increase our current understanding of the interplay between host cells and bacterial pathogens by revealing the targeting of the microRNA pathway as a novel strategy in host-pathogen interactions.

• DFG Programme: Research Grants