Exploring in vivo and in vitro Regulation of the Shigella Type Three Secterion System ATPase Spa47

Diarrheal disease is caused by a diverse group of enteric pathogens and is one of the leading causes of preventable deaths worldwide. Some of the most common causes of diarrheal disease are bacterial pathogens such as Salmonella, E. coli, Cholera, and Shigella. Many bacterial enteric pathogens use a type three secretion system (T3SS) to cause infection. The T3SS uses a needle and syringe like apparatus that allows the bacteria to inject proteins into the host cell to cause infection. Striking similarities in T3SSs from all pathogens that utilize them makes the T3SS an attractive target for the development of non-antibiotic drugs to combat them. With its high global burden, emergence of multi drug resistant strains, and lack of vaccine, Shigella is a prime target for study of the T3SS and is the focus of this dissertation. In Shigella, the ATPase Spa47 resides at the base of the T3SS and is responsible for powering the system. Here, we explore how Shigella regulates Spa47 activity finding two proteins that can both increase and decrease Spa47 activity depending on the oligomeric state of Spa47. Additionally, we explore chemical inhibitors and identify several that efficiently inhibit Spa47 activity and Shigella’s ability to secrete proteins necessary to cause infection. Testing the Shigella ATPase inhibitors on T3SS ATPases from E. Coli and Salmonella showed similar levels of inhibition, demonstrating the potential for developing cross pathogen therapeutics against pathogens that use one or more T3SSs. Together, these findings advance the understanding of how Shigella regulate its T3SS and move us one step closer to developing broadly active therapeutics against an important class of human pathogens.