Suramin action in African trypanosomes involves a RuvB-like DNA helicase

Area of Science:

• Parasitology
• Drug Resistance Mechanisms
• Molecular Biology

Background:

• Suramin is a long-standing treatment for African sleeping sickness and surra.
• The precise mode of action for suramin remains incompletely understood despite its extensive use.
• Suramin is known to interact with multiple protein targets.

Purpose of the Study:

• To investigate the molecular mechanisms underlying suramin resistance in African trypanosomes.
• To identify specific proteins involved in suramin's action and resistance.
• To explore the role of DNA helicases in suramin sensitivity.

Main Methods:

• Long-term selection of Trypanosoma brucei rhodesiense for suramin resistance.
• Identification of mutations in drug-resistant strains using genetic analysis.
• Reverse genetics to introduce specific mutations into drug-sensitive trypanosomes.
• RNA interference (RNAi) to silence the expression of T. brucei RuvBL1 and RuvBL2 genes.
• Phenotypic analysis of trypanosomes following gene silencing, focusing on cell division.

Main Results:

• A homozygous point mutation (Isoleucine-312 to Valine) was identified in T. brucei RuvBL1 in suramin-resistant trypanosomes, located near the ATP binding site.
• Introducing this mutation into drug-sensitive trypanosomes significantly reduced their sensitivity to suramin.
• A similar mutation (to Leucine) was observed in the corresponding residue of T. evansi RuvBL1 in a resistant field isolate.
• Silencing of T. brucei RuvBL1 or RuvBL2 via RNAi led to cell death within 72 hours.
• RNAi induction resulted in cytokinesis defects, with accumulation of cells containing multiple nuclei and kinetoplasts.

Conclusions:

• The DNA helicase T. brucei RuvBL1 plays a critical role in suramin's action against African trypanosomes.
• Mutations in RuvBL1 can confer resistance to suramin, highlighting its importance in the drug's efficacy.
• Targeting RuvBL1 or its associated proteins, like RuvBL2, represents a potential strategy for combating suramin resistance.