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Updated: Jan 25, 2026

Development and Assessment of Intracellular Infection Models for Staphylococcus aureus
Published on: January 17, 2025
Identification of Small Molecule Inhibitors of Staphylococcus aureus RnpA
Jennifer M Colquhoun1, Lisha Ha2, Andrew Beckley3
1Department of Microbiology and Immunology, University of Rochester School of Medicine, Rochester, NY 14642, USA. jennifer_colquhoun@urmc.rochester.edu.
Abstract:
Staphylococcus aureus RnpA is thought to be a unique dual functional antimicrobial target that is required for two essential cellular processes, precursor tRNA processing and messenger RNA degradation. Herein, we used a previously described whole cell-based mupirocin synergy assay to screen members of a 53,000 compound small molecule diversity library and simultaneously enrich for agents with cellular RnpA inhibitory activity. A medicinal chemistry-based campaign was launched to generate a preliminary structure activity relationship and guide early optimization of two novel chemical classes of RnpA inhibitors identified, phenylcarbamoyl cyclic thiophene and piperidinecarboxamide. Representatives of each chemical class displayed potent anti-staphylococcal activity, limited the protein's in vitro ptRNA processing and mRNA degradation activities, and exhibited favorable therapeutic indexes. The most potent piperidinecarboxamide RnpA inhibitor, JC2, displayed inhibition of cellular RnpA mRNA turnover, RnpA-depletion strain hypersusceptibility, and exhibited antimicrobial efficacy in a wax worm model of S. aureus infection. Taken together, these results establish that the whole cell screening assay used is amenable to identifying small molecule RnpA inhibitors within large chemical libraries and that the chemical classes identified here may represent progenitors of new classes of antimicrobials that target RnpA.
Insights
Researchers identified novel small molecules targeting Staphylococcus aureus RnpA, a dual-function protein essential for bacterial survival. These compounds show potent anti-staphylococcal activity and may lead to new antimicrobial therapies.
Area of Science:
- Microbiology
- Drug Discovery
- Biochemistry
Background:
- Staphylococcus aureus RnpA is a unique antimicrobial target essential for precursor tRNA processing and mRNA degradation.
- Developing novel antimicrobials against S. aureus is crucial due to rising resistance.
Purpose of the Study:
- To screen a large small molecule library for inhibitors of S. aureus RnpA.
- To identify and optimize novel chemical classes targeting RnpA.
- To evaluate the anti-staphylococcal activity and therapeutic potential of identified inhibitors.
Main Methods:
- Utilized a whole cell-based mupirocin synergy assay to screen a 53,000-compound library.
- Employed medicinal chemistry to establish structure-activity relationships for identified RnpA inhibitors.
- Assessed in vitro enzyme activity, cellular RnpA inhibition, and in vivo efficacy in a wax worm model.
Main Results:
- Identified two novel chemical classes of RnpA inhibitors: phenylcarbamoyl cyclic thiophene and piperidinecarboxamide.
- Compounds demonstrated potent anti-staphylococcal activity, inhibited RnpA's in vitro functions, and had favorable therapeutic indexes.
- The lead piperidinecarboxamide inhibitor, JC2, showed cellular RnpA mRNA turnover inhibition and in vivo efficacy.
Conclusions:
- The whole cell screening assay is effective for identifying small molecule RnpA inhibitors from large libraries.
- The identified chemical classes represent promising progenitors for new RnpA-targeting antimicrobials.
- Targeting RnpA offers a viable strategy for combating Staphylococcus aureus infections.
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