Ancestral roles of eukaryotic frataxin: mitochondrial frataxin function and heterologous expression of hydrogenosomal Trichomonas homologues in trypanosomes.
Frataxin is a small conserved mitochondrial protein; in humans, mutations affecting frataxin expression or function result in Friedreich's ataxia. Much of the current understanding of frataxin function comes from informative studies with yeast models, but considerable debates remain with regard to the primary functions of this ubiquitous protein. We exploit the tractable reverse genetics of Trypanosoma brucei in order to specifically consider the importance of frataxin in an early branching lineage. Using inducible RNAi, we show that frataxin is essential in T. brucei and that its loss results in reduced activity of the marker Fe-S cluster-containing enzyme aconitase in both the mitochondrion and cytosol. Activities of mitochondrial succinate dehydrogenase and fumarase also decreased, but the concentration of reactive oxygen species increased. Trypanosomes lacking frataxin also exhibited a low mitochondrial membrane potential and reduced oxygen consumption. Crucially, however, iron did not accumulate in frataxin-depleted mitochondria, and as T. brucei frataxin does not form large complexes, it suggests that it plays no role in iron storage. Interestingly, RNAi phenotypes were ameliorated by expression of frataxin homologues from hydrogenosomes of another divergent protist Trichomonas vaginalis. Collectively, the data suggest trypanosome frataxin functions primarily only in Fe-S cluster biogenesis and protection from reactive oxygen species.
Long
Shaojun
S
Biology Centre, Institute of Parasitology, Czech Academy of Sciences, and Faculty of Natural Sciences, University of South Bohemia, Ceské Budejovice (Budweis), Czech Republic.
Jirků
Milan
M
Mach
Jan
J
Ginger
Michael L
ML
Sutak
Robert
R
Richardson
Des
D
Tachezy
Jan
J
Lukes
Julius
J
D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D005057:Eukaryotic Cells / Q000145:classification / Q000502:physiology; D019143:Evolution, Molecular; D015870:Gene Expression; D006801:Humans; D033862:Iron-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D011387:Prokaryotic Cells / Q000145:classification / Q000502:physiology; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D016415:Sequence Alignment; D014244:Trichomonas / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D000096923:Frataxin
D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D000096923:Frataxin