Dual function of mitochondrial complex III in Plasmodium falciparum

Area of Science:

• Mitochondrial physiology
• Parasitic biochemistry
• Drug discovery

Background:

• Complex III in the Plasmodium falciparum mitochondrial electron transport chain (mtETC) is a target for antimalarials.
• Its primary role is ubiquinone regeneration, essential for pyrimidine biosynthesis via dihydroorotate dehydrogenase (DHOD).
• Parasite resistance to mtETC inhibitors can be achieved by bypassing mtETC with yeast DHOD, but complete elimination of mtDNA remains unsuccessful.

Purpose of the Study:

• To investigate the hypothesis that Complex III has dual functions: ubiquinone regeneration and processing of imported mitochondrial proteins.
• To determine the essentiality of mitochondrial processing peptidase alpha (MPPα), a Complex III component, in Plasmodium falciparum.

Main Methods:

• Generation of transgenic Plasmodium falciparum lines with conditional expression of MPPα.
• Assessment of parasite viability and drug sensitivity upon MPPα knockdown.
• Pulldown assays with MPPα followed by proteomics to identify associated proteins.

Main Results:

• MPPα is essential for parasite survival, independent of its role in the mtETC.
• MPPα knockdown leads to hypersensitivity to proguanil, which synergizes with mtETC inhibitors.
• Proteomic analysis revealed MPPα associates with other Complex III components and multiple mitochondrially targeted proteins.

Conclusions:

• Complex III in Plasmodium falciparum possesses essential dual functions in both mtETC activity and mitochondrial protein processing.
• Targeting Complex III's protein processing role may offer novel antimalarial therapeutic strategies.
• The findings explain the inability to eliminate mtDNA and highlight Complex III as a multifaceted target.