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Redox Homeostasis within the Drug-Resistant Malarial Parasite Digestive Vacuole
Andreas Willems1, Therese Oertel1, Paul D Roepe1
1Depts. of Chemistry and of Biochemistry and Cellular and Molecular Biology, Georgetown University, 37th and O Streets NW, Washington, District of Columbia 20057, United States.
Biochemistry
|May 1, 2025
Summary
We created new fluorescent probes to measure glutathione (GSH) levels in malaria parasites. These probes help understand drug resistance and parasite biology.
Area of Science:
- Biochemistry
- Medicinal Chemistry
- Parasitology
Background:
- Glutathione (GSH) is a key indicator of cellular redox state.
- Understanding redox homeostasis in Plasmodium falciparum is crucial for antimalarial drug development.
- Existing methods for measuring GSH in live parasites are limited.
Purpose of the Study:
- To develop and validate novel coumarin-based fluorescent probes for measuring glutathione levels.
- To investigate the subcellular localization and reporting capabilities of these probes in live malaria parasites.
- To assess the utility of these probes in understanding antimalarial drug action and resistance.
Main Methods:
- Cost-effective synthesis of azetidinyl coumarin fluorophore derivatives.
- Functionalization of coumarin probes with cyano side chains and conjugation to dextrans or morpholino groups.
- Titration of probe fluorescence versus GSH concentration in vitro.
- Single-cell photometry (SCP) for measuring probe localization and fluorescence in live intraerythrocytic P. falciparum.
- Live-cell perfusion studies to monitor parasite redox homeostasis under drug pressure.
Main Results:
- Validated azetidinyl conformation for enhanced GSH-dependent fluorescence.
- Demonstrated successful subcellular localization of probes in parasite cytosol and digestive vacuole (DV).
- Showcased the morpholino probe's ability to report cytosolic GSH levels and dextran-conjugated probes to report DV redox homeostasis.
- Quantified rapid changes in DV redox homeostasis in response to antimalarial drugs in sensitive and resistant parasite strains.
Conclusions:
- Developed a versatile platform of coumarin-based fluorescent probes for monitoring GSH and redox homeostasis.
- The probes provide valuable insights into parasite redox biology and antimalarial drug mechanisms.
- These tools are essential for advancing research into malaria parasite drug resistance and developing new therapeutics.
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