Shames Research Project Summary

Intracellular bacterial pathogens utilize highly evolved virulence factors to replicate in eukaryotic cells. Legionella pneumophila (Lpn) naturally parasitizes unicellular fresh water protozoa but can cause a severe pneumonia in humans called Legionnaires’ disease. Human infection results from inhalation of Lpn originating from anthropomorphic fresh water environments containing the bacteria and subsequent bacterial replication in alveolar macrophages. Lpn replication within phagocytes is facilitated by a large arsenal of virulence factors termed effector proteins that are translocated directly into infected host cells. The long-term objectives of this proposal are to develop chemical inhibitors of effector function as therapeutics to treat infectious diseases and enhance understanding of bacterial pathogenesis mechanisms. The Lpn effector Lpg2505 is a ‘metaeffector’ that interacts directly with another Lpn effector called SidI. SidI function is toxic to eukaryotic cells; however, this toxicity is suppressed by Lpg2505 to promote Lpn replication. Consequently, expression of sidI in the absence of Lpg2505 is detrimental to Lpn replication in protozoa and macrophages. Thus, the central hypothesis of this proposal is that chemical inhibition of Lpg2505-mediated regulation of SidI will impair Lpn intracellular replication. To test the central hypothesis, the following specific aims will be pursued. Aim 1 is to use genetics, structural biology, and chemical biology to define the Lpg2505-SidI protein-protein interaction interface. Aim 2 is to collaborate with the CBID IDAD Core at the University of Kansas to perform a high-throughput screen to identify chemical inhibitors of Lpg2505-mediated regulation of SidI. Identified compounds will be evaluated for their ability to control Lpn replication in protozoan and mammalian hosts. The results of this work will improve human health by through the development of compounds that can utilized to (1) impair Lpn intracellular replication; (2) enhance understanding of metaeffector function; and (3) reveal molecular mechanisms of bacterial pathogenesis that enable replication within eukaryotic phagocytes. Thus, this work will provide a foundation for use of chemical biology to study effector function and development of chemical inhibitors of virulence factor function as a means to combat a variety of infectious diseases.