Abstract

Trypanosoma brucei, the causative agent of African trypanosomiasis, and its relatives Trypanosoma cruzi and several Leishmania species belong to a class of protozoa called kinetoplastids that cause a significant health burden in tropical and semitropical countries across the world. While an improved therapy was recently approved for African trypanosomiasis, the therapies available to treat infections caused by T. cruzi and Leishmania spp. remain relatively poor. Improving our understanding of T. brucei metabolism can inform on metabolism of its relatives. The purpose of the research presented in this dissertation was to develop novel tools and methods to study metabolism in T. brucei with the ultimate aim to improve treatments of all kinetoplastid diseases. We developed a novel tool to study glycosomal pH in the bloodstream form of T. brucei. Using this tool, we discovered that this life stage regulates glycosomal pH differently than the procyclic form, or insect-dwelling stage, and only uses sodium/proton transporters to regulate glycosomal pH. I pioneered a thermal proteome profiling method in this parasite to discover drug targets and their effects on cell pathways. Using this method, I found that other proteins may be involved in glycosomal pH regulation, including PEX11 and a vacuolar ATPase. This method also illuminated several important pathways influenced by glycosomal pH regulation, including glycosome proliferation, vesicle trafficking, protein glycosylation, and amino acid transport. Metabolic studies in kinetoplastid parasites are currently hampered by the lack of available chemical probes. We developed a novel flow cytometry-based high-throughput drug screening assay to discover chemical probes of T. brucei glycolysis. This method combines the advantages of phenotypic (or cell-based) screens with the advantage of targeted (purified protein) screens by multiplexing biosensors that measure multiple glycolytic metabolites simultaneously, such as glucose, ATP, and glycosomal pH. The complementary information gained is then used to distinguish the part of glycolysis identified inhibitors target. We validated the method using the well characterized glycolytic and alternative oxidase inhibitors 2-deoxyglucose and salicylhydroxamic acid respectively. We demonstrated the screening assay with a pilot screen of 14,976 compounds with decent hit rates for each sensor (0.2-0.4%). About 64% of rescreened hits repeated activity in at least one sensor. We demonstrated one compound with micromolar activity against two biosensors. In summary, we developed and demonstrated a novel screening method that can discover glycolytic chemical probes to better study metabolism in this and related parasites. There are few methods to study enzyme kinetics in the live-cell environment. I developed a kinetic flow cytometry assay that can measure enzyme and transporter activity using fluorescent biosensors. I demonstrated this by measuring glucose transport kinetics and alternative oxidase inhibition kinetics, with the measured kinetic parameters similar to those previously reported. We plan to expand on this method to measure transport kinetics in the glycosome and other organelles which has not been done before. We previously performed a drug screen to identify inhibitors that decrease intracellular glucose in T. brucei. I have performed preliminary work identifying the glucose transporter THT1 as one of the targets of optimized glucose inhibitors using the previously mentioned thermal proteome profiling method. We expect this finding will improve our ability to move these compounds from hit to lead in the drug discovery pipeline. Together, I have developed several flow cytometry and proteomics methods to better study metabolism in T. brucei. These tools are beginning to be used in related parasites. We expect the discoveries made using these tools will improve our ability to treat these neglected tropical diseases.

Degree

PhD

College and Department

Computational, Mathematical, and Physical Sciences; Chemistry and Biochemistry

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2024-05-07

Document Type

Dissertation

Handle

http://hdl.lib.byu.edu/1877/etd13235

Keywords

Trypanosoma brucei, glycolysis, glycosome, peroxisome, thermal proteome profiling, drug target deconvolution, fluorescent biosensor, glycosome, pH regulation, glucose sensing, proton transport, flow cytometry

Language

english

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