Design, synthesis, and evaluation of cholera toxin inhibitors and [alpha]-helix mimetics of dormancy survival regulator

Abstract

Infectious diseases cause millions of deaths each year. The top single disease killers include tuberculosis (TB) and diarrheal diseases. The diarrheal diseases caused by cholera toxin (CT) and Escherichia coli heat-labile enterotoxin (LT) constitute a large part of the diarrhea-related deaths worldwide each year. While there have been some efficacious drugs against Vibrio cholerae in the market, their resistance is developing very quickly. Our group is engaged in developing synthetic molecules that could bind to CT with a high affinity to block the enzymatic reaction catalyzed by CT. We report here the design, synthesis and biological evaluation of bisubstrate analogues targeting the active site of CT. The most potent inhibitor demonstrated an IC50 of around 40 muM, which is 350-fold more potent than the natural substrate NAD. This compound could potentially serve as a lead for the discovery of therapeutic reagent to treat cholera.The other project is the exploration of the use of alpha-helix mimetics for probing the protein-protein interactions of dormancy survival regulator (DosR). The main function of DosR is to mediate the transition of Mycobacteria tuberculosis into dormancy and may contribute to latency. Disruption of the dimerization of DosR could keep M. tuberculosis in an active state, so that the existing drugs could treat them effectively. We employed both the small molecule approach and peptide approach to design potent alpha-helix mimetics and so far the most potent compound showed an IC50 of around 40 muM. The long linear peptide inhibitors synthesized in this study demonstrated an IC50 of around 100 muM. This opens up the possibility of systematic investigation of the DosR interface by incorporating different side chains. This strategy could be extended to study other interfaces with protein-protein interaction.