Pharmacophore-based screening and modification of amiloride analogs for targeting the NhaP-type cation-proton antiporter in Vibrio cholerae

Abstract

The genome of Vibrio cholerae contains three structural genes for the NhaP-type cation-proton antiporter paralogues, Vc-NhaP1, Vc-NhaP2, and Vc-NhaP3, mediating exchange of K+ and or Na+ for protons across the membrane. Based on phenotypic analysis of chromosomal Vc-NhaP1, Vc-NhaP2, and Vc-NhaP3 triple deletion mutants, we suggest that Vc-NhaP paralogues are primarily K+/H+ antiporters and might play a role in the acid tolerance response of V. cholerae as it passes through the gastric acid barrier of the stomach. Comparison of the biochemical properties of Vc-NhaP isoforms revealed that Vc-NhaP2 was the most active among all three paralogues. Therefore, the Vc-NhaP2 antiporter is a plausible therapeutic target for developing novel inhibitors targeting these ion exchangers. Our structural and mutational analysis of Vc-NhaP2 identified a putative cation-binding pocket formed by antiparallel extended regions of two transmembrane segments (TMSs V and XII) along with TMS VI. Molecular dynamics simulations suggested that the flexibility of TMSs V and XII is crucial for intramolecular conformational events in Vc-NhaP2. In this study, we developed putative Vc-NhaP2 inhibitors from amiloride analogs. Molecular docking of the modified amiloride analogs revealed promising binding properties. The four selected drugs potentially interacted with functionally important amino acid residues located on the cytoplasmic side of TMS VI, the extended chain region of TMSs V and XII, and the loop region between TMSs VIIII and IX. Molecular dynamics simulations revealed that binding of the selected drugs can potentially destabilize Vc-NhaP2 and alter the flexibility of functionally important TMS VI. This work presents the utility of in silico approaches for the rational identification of potential targets and drugs that could target NhaP2 cation proton antiporters to control V. cholerae. The goal was to identify potential drugs that could be validated in future experiments.