Development of phenolic small molecule inhibitors of PfATP6, a Plasmodium calcium ATPase

Project Summary/Abstract Malaria, an infectious disease caused by Plasmodium parasites, continues to pose a serious global health problem. PfATP6, a calcium-transporting enzyme present in Plasmodium falciparum, has been identified as a target for new antimalarial drugs. Therefore, specific and potent inhibitors of PfATP6 hold promise as a new generation of antimalarial agents. They may also be of value as research tools for the elucidation of the enzyme’s physiological roles. Only a few PfATP6 inhibitors are presently known and most of them suffer from limitations due to their high structural complexity, restricting their availability. A notable exception is a group of structurally simple phenolic compounds that were originally identified in library screens. As they feature hydroquinone and naphthoquinone scaffolds, they can be synthesized straightforwardly, which is a major advantage. The proposed project focusses on the design and characterization of novel PfATP6 inhibitors, with initial focus on the hydroquinone/naphthoquinone scaffolds. The long term goal of this research is to obtain a comprehensive understanding of the interactions between PfATP6 and small inhibitory molecules at the molecular level. As a first step, the objective of this proposal is to identify and characterize inhibitors that are good candidates for future development. Preliminary data suggest that the development of new PfATP6 inhibitors based on the targeted scaffolds is an achievable goal. To reach it, the following two Specific Aims will be pursued: Aim 1: Establish the structural requirements for effective PfATP6 inhibition. An initial library of 50-60 potential inhibitors will be obtained from vendors or be synthesized. These compounds will first be evaluated in inhibition assays with purified PfATP6 and then in viability assays with living parasites. The results will furnish structure-activity relationships that identify structural elements critical for inhibition. Aim 2: Identify novel inhibitor scaffolds using structural models of the inhibitor binding site of PfATP6. Applying computational techniques, structural models of the currently unknown inhibitor binding site will be generated. After having validated the models, their predictive capabilities will be employed for virtual screens of compound libraries to identify alternative inhibitor types. The ultimate goal is to increase the structural variety of the PfATP6 inhibitor pool by adding compounds with new scaffolds. The proposed research is innovative because it will be the first to systematically explore small molecule PfATP6 inhibitors by a combination of experimental and computational approaches. It is significant as it provides fundamental information necessary to develop novel anti-malarial agents and valuable new research tools. Moreover, the project will enable the PI to initiate and sustain a meritorious research program at Sacramento State, engaging students interested in a future career in biomedicine in a multi-disciplinary drug design project.