Identification of a Salmonella PhoP/PhoQ system inhibitor from a dynamic combinatorial library

LOBERTTI, C.; CABEZUDO, I.; FURLAN, R. L.; ELEONORA, GARCIA VÉSCOVI

Salta

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

SAIB-PABMB

Salmonella is an enteropathogen that causes a wide range of diseases in humans and animals. PhoP/PhoQ is a two-component system (TCS)distributed amongst several Gramnegative bacteria, consisting of the histidine kinase PhoQ, and the transcriptional regulator PhoP. In S.typhimurium, the PhoP/PhoQ system regulates the adaptation to Mg2+-limiting environments and controls key virulence phenotypes such as theinvasion and proliferation within host cells. As signal transduction in mammals does not involve TCS, the PhoP/PhoQ system is an attractivetarget to develop new antimicrobial agents. We have previously reported a methodology based on a TLC-overlay as a new strategy for the searchand identification of antimicrobial agents targeting the PhoP/PhoQ system. We applied this bioguided strategy using a strain carrying a PhoPcontrolledreporter gene, to the screening of a dynamic combinatorial library of hidrazones in the search for inhibitors. As a result, two librariesof hydrazones and three libraries of thiocarbazones totalling over 370 members were screened for their inhibitory activity through a rapidinexpensive TLC strategy. Satisfactorily, a complex library of hydrazones that can repress the PhoP/PhoQ system was selected from the initialscreening, to further study its members. Through iterative deconvolution of over 100 library members we identified a potential inhibitor, A25B4.This compound could be synthesized in its pure form, characterized, and it was confirmed that it does not affect the growth of Salmonella. By-galactosidase assays we confirmed its inhibitory activity and it was found that the response was dose-dependent and selective aswell. Once the mechanism of action of A25B4 in the system is known, a target protein domain of the TCS will be used to template a library ofhydrazones, biasing the composition of the dynamic library towards A25B4. This step will further confirm its affinity and mechanism of action.This strategy allow to us to establish a novel methodology for the discovery of PhoP/PhoQ system inhibitors to fight against Salmonella bornedisease.