Human African trypanosomiasis (HAT) is caused by the parasitic protozoan Trypanosoma brucei. HAT exerts a large burden in both health and economic costs to the affected regions. There is a great need to translate recent advances in the understanding ofthe basic biology ofthe parasite into new drugs. Polyamines are essential metabolites that are required for cell growth. The polyamine biosynthetic enzymes, including ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) are essential to the parasite, and ODC is the target of a currently utilized anti-trypanosomal drug called eflornithine. In order to better understand the pathway and its potential to be exploited for additional drug discovery my lab has been using genetic, biochemical and structural approaches to determine which enzymes in the pathway are essential, to characterize regulatory mechanisms used to control pathway flux, to understand structure function relationships influencing catalysis and ligand binding to ODC and AdoMetDC, and to discover new inhibitors of pathway enzymes. In this fund period we have shown that spermidine synthase and glutathione synthase are essential enzymes, we have built on our previous discovery that that AdoMetDC is regulated by a novel mechanism by identifying both cis and trans factors that may contribute to translational regulation ofthe AdoMetDC regulatory subunit prozyme and we have identified new inhibitors of both ODC and AdoMetDC. Finally in a new direction we have begun studies on the role of deoxyhypusine synthase (DHS) in T. brucei. We remarkedly discovered that similarly to AdoMetDC, DHS is activated by oligomerization with a catalytically dead paralog, showing that this novel mechanism has evolved twice within the trypanosomatid polyamine metabolic pathway. Future studies will build on these findings to: 1) characterize cis/trans regulatory factors influencing translation of prozyme, 2) solve the X-ray structure sof both the AdoMetDC and DHS 3) identify other proteins in T. brucei that are regulated by inactive paralogs, and 4) study the role of deoxyhypusine modification of elF5A in T. brucei.

Public Health Relevance

Human African sleeping sickness is a fatal insect borne disease and current drug therapies are toxic and difficult to administer. The work described in this proposal characterizes the biology of an essential metabolic pathway (polyamine and trypanothione biosynthesis) that has unique features in the parasite, with the goal of providing insight into the potential to target this pathway for drug discovery.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Method to Extend Research in Time (MERIT) Award (R37)
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No Study Section (in-house review) (NSS)
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Mcgugan, Glen C
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Phillips, Margaret A (2018) Polyamines in protozoan pathogens. J Biol Chem 293:18746-18756
Afanador, Gustavo A; Tomchick, Diana R; Phillips, Margaret A (2018) Trypanosomatid Deoxyhypusine Synthase Activity Is Dependent on Shared Active-Site Complementation between Pseudoenzyme Paralogs. Structure 26:1499-1512.e5
Patel, Manish M; Volkov, Oleg A; Leija, Christopher et al. (2018) A dual regulatory circuit consisting of S-adenosylmethionine decarboxylase protein and its reaction product controls expression of the paralogous activator prozyme in Trypanosoma brucei. PLoS Pathog 14:e1007404
Volkov, Oleg A; Brockway, Anthony J; Wring, Stephen A et al. (2018) Species-Selective Pyrimidineamine Inhibitors of Trypanosoma brucei S-Adenosylmethionine Decarboxylase. J Med Chem 61:1182-1203
Brockway, Anthony J; Volkov, Oleg A; Cosner, Casey C et al. (2017) Synthesis and evaluation of analogs of 5'-(((Z)-4-amino-2-butenyl)methylamino)-5'-deoxyadenosine (MDL 73811, or AbeAdo) - An inhibitor of S-adenosylmethionine decarboxylase with antitrypanosomal activity. Bioorg Med Chem 25:5433-5440
Volkov, Oleg A; Cosner, Casey C; Brockway, Anthony J et al. (2017) Identification of Trypanosoma brucei AdoMetDC Inhibitors Using a High-Throughput Mass Spectrometry-Based Assay. ACS Infect Dis 3:512-526
Leija, Christopher; Rijo-Ferreira, Filipa; Kinch, Lisa N et al. (2016) Pyrimidine Salvage Enzymes Are Essential for De Novo Biosynthesis of Deoxypyrimidine Nucleotides in Trypanosoma brucei. PLoS Pathog 12:e1006010
BiƩler, Sylvain; Waltenberger, Harald; Barrett, Michael P et al. (2016) Evaluation of Antigens for Development of a Serological Test for Human African Trypanosomiasis. PLoS One 11:e0168074
Volkov, Oleg A; Kinch, Lisa; Ariagno, Carson et al. (2016) Relief of autoinhibition by conformational switch explains enzyme activation by a catalytically dead paralog. Elife 5:
Brockway, Anthony J; Cosner, Casey C; Volkov, Oleg A et al. (2016) Improved Synthesis of MDL 73811 - a Potent AdoMetDC Inhibitor and Anti-Trypanosomal Compound. Synthesis (Stuttg) 48:2065-2068

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