Quantification of labile heme in live malaria parasites using a genetically encoded biosensor

Area of Science:

• Biochemistry
• Parasitology
• Cellular Biology

Background:

• Heme is essential but its labile pool maintenance is poorly understood.
• Quantitative analysis of labile heme is critical for understanding cellular function and redox damage.
• Heme's role in cellular processes necessitates understanding its bioavailability and regulation.

Purpose of the Study:

• To develop and characterize a novel protein-based fluorescent sensor for quantifying labile heme.
• To measure cytosolic labile heme levels in the human malarial parasite, Plasmodium falciparum.
• To investigate the impact of antimalarial drugs on heme homeostasis.

Main Methods:

• Development of a genetically encoded, heme-binding fluorescent protein sensor.
• Quantitative fluorescence quenching assay to measure heme concentration.
• Application of the sensor in intact, blood-stage Plasmodium falciparum parasites.

Main Results:

• Quantified a stable cytosolic labile heme pool of approximately 1.6 µM in P. falciparum.
• Demonstrated stable heme levels throughout parasite development within red blood cells.
• Showed that chloroquine increases labile cytosolic heme, suggesting dysregulation of heme homeostasis.

Conclusions:

• The developed sensor enables quantitative measurement of labile heme in live parasites.
• A stable heme pool is maintained by P. falciparum, despite extensive hemoglobin degradation.
• Chloroquine's effect on heme levels may contribute to its antimalarial activity, highlighting potential therapeutic strategies.