Knock-downs of iron-sulfur cluster assembly proteins IscS and IscU down-regulate the active mitochondrion of procyclic Trypanosoma brucei.
Transformation of the metabolically down-regulated mitochondrion of the mammalian bloodstream stage of Trypanosoma brucei to the ATP-producing mitochondrion of the insect procyclic stage is accompanied by the de novo synthesis of citric acid cycle enzymes and components of the respiratory chain. Because these metabolic pathways contain multiple iron-sulfur (FeS) proteins, their synthesis, including the formation of FeS clusters, is required. However, nothing is known about FeS cluster biogenesis in trypanosomes, organisms that are evolutionarily distant from yeast and humans. Here we demonstrate that two mitochondrial proteins, the cysteine desulfurase TbiscS and the metallochaperone TbiscU, are functionally conserved in trypanosomes and essential for this parasite. Knock-downs of TbiscS and TbiscU in the procyclic stage by means of RNA interference resulted in reduced activity of the marker FeS enzyme aconitase in both the mitochondrion and cytosol because of the lack of FeS clusters. Moreover, down-regulation of TbiscS and TbiscU affected the metabolism of procyclic T. brucei so that their mitochondria resembled the organelle of the bloodstream stage; mitochondrial ATP production was impaired, the activity of the respiratory chain protein complex ubiquinol-cytochrome-c reductase was reduced, and the production of pyruvate as an end product of glucose metabolism was enhanced. These results indicate that mitochondrial FeS cluster assembly is indispensable for completion of the T. brucei life cycle.
Smíd
Ondrej
O
Department of Parasitology, Faculty of Science, Charles University, 12844 Prague, Czech Republic.
Horáková
Eva
E
Vilímová
Vanda
V
Hrdy
Ivan
I
Cammack
Richard
R
Horváth
Anton
A
Lukes
Julius
J
Tachezy
Jan
J
D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D017124:Conserved Sequence; D003579:Cytochrome Reductases / Q000378:metabolism; D015536:Down-Regulation; D004578:Electron Spin Resonance Spectroscopy; D005821:Genetic Techniques; D005822:Genetic Vectors; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics*; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics*; D008957:Models, Genetic; D034622:RNA Interference; D014346:Trypanosoma brucei brucei; D014451:Ubiquinone / Q000031:analogs & derivatives / Q000737:chemistry
D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; D014451:Ubiquinone; D000255:Adenosine Triphosphate; D003579:Cytochrome Reductases; C003741:ubiquinol