Protein import and genome replication are essential processes for mitochondrial biogenesis and propagation. The J-domain proteins Pam16 and Pam18 regulate the presequence translocase of the mitochondrial inner membrane. In the protozoan Trypanosoma brucei, their counterparts are TbPam16 and TbPam18, which are essential for the procyclic form (PCF) of the parasite, though not involved in mitochondrial protein import. Here, we show that during evolution, the 2 proteins have been repurposed to regulate the replication of maxicircles within the intricate kDNA network, the most complex mitochondrial genome known. TbPam18 and TbPam16 have inactive J-domains suggesting a function independent of heat shock proteins. However, their single transmembrane domain is essential for function. Pulldown of TbPam16 identifies a putative client protein, termed MaRF11, the depletion of which causes the selective loss of maxicircles, akin to the effects observed for TbPam18 and TbPam16. Moreover, depletion of the mitochondrial proteasome results in increased levels of MaRF11. Thus, we have discovered a protein complex comprising TbPam18, TbPam16, and MaRF11, that controls maxicircle replication. We propose a working model in which the matrix protein MaRF11 functions downstream of the 2 integral inner membrane proteins TbPam18 and TbPam16. Moreover, we suggest that the levels of MaRF11 are controlled by the mitochondrial proteasome.

• MeSH
• DNA, Mitochondrial * genetics   metabolism   MeSH
• Mitochondrial Proteins metabolism   genetics   MeSH
• Mitochondria metabolism   genetics   MeSH
• Evolution, Molecular MeSH
• Protozoan Proteins * metabolism   genetics   MeSH
• DNA Replication * MeSH
• Trypanosoma brucei brucei * metabolism   genetics   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA, Mitochondrial * MeSH
• Mitochondrial Proteins MeSH
• Protozoan Proteins * MeSH

The long slender bloodstream form Trypanosoma brucei maintains its essential mitochondrial membrane potential (ΔΨm) through the proton-pumping activity of the FoF1-ATP synthase operating in the reverse mode. The ATP that drives this hydrolytic reaction has long been thought to be generated by glycolysis and imported from the cytosol via an ATP/ADP carrier (AAC). Indeed, we demonstrate that AAC is the only carrier that can import ATP into the mitochondrial matrix to power the hydrolytic activity of the FoF1-ATP synthase. However, contrary to expectations, the deletion of AAC has no effect on parasite growth, virulence or levels of ΔΨm. This suggests that ATP is produced by substrate-level phosphorylation pathways in the mitochondrion. Therefore, we knocked out the succinyl-CoA synthetase (SCS) gene, a key mitochondrial enzyme that produces ATP through substrate-level phosphorylation in this parasite. Its absence resulted in changes to the metabolic landscape of the parasite, lowered virulence, and reduced mitochondrial ATP content. Strikingly, these SCS mutant parasites become more dependent on AAC as demonstrated by a 25-fold increase in their sensitivity to the AAC inhibitor, carboxyatractyloside. Since the parasites were able to adapt to the loss of SCS in culture, we also analyzed the more immediate phenotypes that manifest when SCS expression is rapidly suppressed by RNAi. Importantly, when performed under nutrient-limited conditions mimicking various host environments, SCS depletion strongly affected parasite growth and levels of ΔΨm. In totality, the data establish that the long slender bloodstream form mitochondrion is capable of generating ATP via substrate-level phosphorylation pathways.

• MeSH
• Adenosine Triphosphate metabolism   MeSH
• Phosphorylation MeSH
• Mitochondria metabolism   MeSH
• Trypanosoma brucei brucei * metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adenosine Triphosphate MeSH

Many of the currently available anti-parasitic and anti-fungal frontline drugs have severe limitations, including adverse side effects, complex administration, and increasing occurrence of resistance. The discovery and development of new therapeutic agents is a costly and lengthy process. Therefore, repurposing drugs with already established clinical application offers an attractive, fast-track approach for novel treatment options. In this study, we show that the anti-cancer drug candidate MitoTam, a mitochondria-targeted analog of tamoxifen, efficiently eliminates a wide range of evolutionarily distinct pathogens in vitro, including pathogenic fungi, Plasmodium falciparum, and several species of trypanosomatid parasites, causative agents of debilitating neglected tropical diseases. MitoTam treatment was also effective in vivo and significantly reduced parasitemia of two medically important parasites, Leishmania mexicana and Trypanosoma brucei, in their respective animal infection models. Functional analysis in the bloodstream form of T. brucei showed that MitoTam rapidly altered mitochondrial functions, particularly affecting cellular respiration, lowering ATP levels, and dissipating mitochondrial membrane potential. Our data suggest that the mode of action of MitoTam involves disruption of the inner mitochondrial membrane, leading to rapid organelle depolarization and cell death. Altogether, MitoTam is an excellent candidate drug against several important pathogens, for which there are no efficient therapies and for which drug development is not a priority.

• Keywords
• Candida, Cryptococcus, Leishmania, Plasmodium, Trypanosoma, drug, mitochondria,
• MeSH
• Membrane Potential, Mitochondrial MeSH
• Plasmodium falciparum MeSH
• Drug Repositioning MeSH
• Antineoplastic Agents * metabolism   pharmacology   MeSH
• Trypanosoma brucei brucei * MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antineoplastic Agents * MeSH

Mitochondrial F-type adenosine triphosphate (ATP) synthases are commonly introduced as highly conserved membrane-embedded rotary machines generating the majority of cellular ATP. This simplified view neglects recently revealed striking compositional diversity of the enzyme and the fact that in specific life stages of some parasites, the physiological role of the enzyme is to maintain the mitochondrial membrane potential at the expense of ATP rather than to produce ATP. In addition, mitochondrial ATP synthases contribute indirectly to the organelle's other functions because they belong to major determinants of submitochondrial morphology. Here, we review current knowledge about the trypanosomal ATP synthase composition and architecture in the context of recent advances in the structural characterization of counterpart enzymes from several eukaryotic supergroups. We also discuss the physiological function of mitochondrial ATP synthases in three trypanosomatid parasites, Trypanosoma cruzi, Trypanosoma brucei and Leishmania, with a focus on their disease-causing life cycle stages. We highlight the reversed proton-pumping role of the ATP synthase in the T. brucei bloodstream form, the enzyme's potential link to the regulation of parasite's glycolysis and its role in generating mitochondrial membrane potential in the absence of mitochondrial DNA.

• Keywords
• ATP synthase, cryo-EM, mitochondria, mitochondrial membrane potential, oxidative phosphorylation,
• MeSH
• Genetic Engineering * MeSH
• Leishmania enzymology   MeSH
• Membrane Potential, Mitochondrial MeSH
• Mitochondrial Proton-Translocating ATPases genetics   metabolism   MeSH
• Protozoan Proteins genetics   metabolism   MeSH
• Trypanosoma brucei brucei enzymology   MeSH
• Trypanosoma cruzi enzymology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Mitochondrial Proton-Translocating ATPases MeSH
• Protozoan Proteins MeSH

A recently redescribed two-flagellar trypanosomatid Vickermania ingenoplastis is insensitive to the classical inhibitors of respiration and thrives under anaerobic conditions. Using genomic and transcriptomic data, we analyzed its genes of the core metabolism and documented that subunits of the mitochondrial respiratory complexes III and IV are ablated, while those of complexes I, II, and V are all present, along with an alternative oxidase. This explains the previously reported conversion of glucose to acetate and succinate by aerobic fermentation. Glycolytic pyruvate is metabolized to acetate and ethanol by pyruvate dismutation, whereby a unique type of alcohol dehydrogenase (shared only with Phytomonas spp.) processes an excess of reducing equivalents formed under anaerobic conditions, leading to the formation of ethanol. Succinate (formed to maintain the glycosomal redox balance) is converted to propionate by a cyclic process involving three enzymes of the mitochondrial methyl-malonyl-CoA pathway, via a cyclic process, which results in the formation of additional ATP. The unusual structure of the V. ingenoplastis genome and its similarity with that of Phytomonas spp. imply their relatedness or convergent evolution. Nevertheless, a critical difference between these two trypanosomatids is that the former has significantly increased its genome size by gene duplications, while the latter streamlined its genome.

• Keywords
• Phytomonas, Vickermania ingenoplastis, genome sequencing, metabolism,
• Publication type
• Journal Article MeSH

Trypanosoma brucei is a parasitic protozoan that undergoes a complex life cycle involving insect and mammalian hosts that present dramatically different nutritional environments. Mitochondrial metabolism and gene expression are highly regulated to accommodate these environmental changes, including regulation of mRNAs that require extensive uridine insertion/deletion (U-indel) editing for their maturation. Here, we use high throughput sequencing and a method for promoting life cycle changes in vitro to assess the mechanisms and timing of developmentally regulated edited mRNA expression. We show that edited CYb mRNA is downregulated in mammalian bloodstream forms (BSF) at the level of editing initiation and/or edited mRNA stability. In contrast, edited COIII mRNAs are depleted in BSF by inhibition of editing progression. We identify cell line-specific differences in the mechanisms abrogating COIII mRNA editing, including the possible utilization of terminator gRNAs that preclude the 3' to 5' progression of editing. By examining the developmental timing of altered mitochondrial mRNA levels, we also reveal transcript-specific developmental checkpoints in epimastigote (EMF), metacyclic (MCF), and BSF. These studies represent the first analysis of the mechanisms governing edited mRNA levels during T. brucei development and the first to interrogate U-indel editing in EMF and MCF life cycle stages.

• MeSH
• RNA Editing genetics   MeSH
• RNA, Guide, Kinetoplastida genetics   MeSH
• RNA, Messenger genetics   MeSH
• Mitochondria genetics   MeSH
• Protozoan Proteins genetics   MeSH
• RNA, Mitochondrial genetics   MeSH
• RNA, Protozoan genetics   MeSH
• RNA Stability genetics   MeSH
• Trypanosoma brucei brucei genetics   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• RNA, Guide, Kinetoplastida MeSH
• RNA, Messenger MeSH
• mitochondrial messenger RNA MeSH Browser
• Protozoan Proteins MeSH
• RNA, Mitochondrial MeSH
• RNA, Protozoan MeSH

ZapE/Afg1 is a component of the inner cell membrane of some eubacteria and the inner mitochondrial membrane of eukaryotes. This protein is involved in FtsZ-dependent division of eubacteria. In the yeast and human mitochondrion, ZapE/Afg1 likely interacts with Oxa1 and facilitates the degradation of mitochondrion-encoded subunits of respiratory complexes. Furthermore, the depletion of ZapE increases resistance to apoptosis, decreases oxidative stress tolerance, and impacts mitochondrial protein homeostasis. It remains unclear whether ZapE is a multifunctional protein, or whether some of the described effects are just secondary phenotypes. Here, we have analyzed the functions of ZapE in Trypanosoma brucei, a parasitic protist, and an important model organism. Using a newly developed proximity-dependent biotinylation approach (BioID2), we have identified the inner mitochondrial membrane insertase Oxa1 among three putative interacting partners of ZapE, which is present in two paralogs. RNAi-mediated depletion of both ZapE paralogs likely affected the function of respiratory complexes I and IV. Consistently, we show that the distribution of mitochondrial ZapE is restricted only to organisms with Oxa1, respiratory complexes, and a mitochondrial genome. We propose that the evolutionarily conserved interaction of ZapE with Oxa1, which is required for proper insertion of many inner mitochondrial membrane proteins, is behind the multifaceted phenotype caused by the ablation of ZapE.

• MeSH
• Biotinylation MeSH
• Gene Deletion * MeSH
• Down-Regulation MeSH
• Eukaryota genetics   MeSH
• Phenotype MeSH
• Phylogeny MeSH
• Genome, Mitochondrial MeSH
• Mitochondrial Proteins metabolism   MeSH
• Mitochondria metabolism   MeSH
• Protozoan Proteins metabolism   MeSH
• Electron Transport Complex I metabolism   MeSH
• Electron Transport Complex IV metabolism   MeSH
• Trypanosoma brucei brucei metabolism   MeSH
• Protein Binding MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Mitochondrial Proteins MeSH
• Protozoan Proteins MeSH
• Electron Transport Complex I MeSH
• Electron Transport Complex IV MeSH

Introduced about a century ago, suramin remains a frontline drug for the management of early-stage East African trypanosomiasis (sleeping sickness). Cellular entry into the causative agent, the protozoan parasite Trypanosoma brucei, occurs through receptor-mediated endocytosis involving the parasite's invariant surface glycoprotein 75 (ISG75), followed by transport into the cytosol via a lysosomal transporter. The molecular basis of the trypanocidal activity of suramin remains unclear, but some evidence suggests broad, but specific, impacts on trypanosome metabolism (i.e. polypharmacology). Here we observed that suramin is rapidly accumulated in trypanosome cells proportionally to ISG75 abundance. Although we found little evidence that suramin disrupts glycolytic or glycosomal pathways, we noted increased mitochondrial ATP production, but a net decrease in cellular ATP levels. Metabolomics highlighted additional impacts on mitochondrial metabolism, including partial Krebs' cycle activation and significant accumulation of pyruvate, corroborated by increased expression of mitochondrial enzymes and transporters. Significantly, the vast majority of suramin-induced proteins were normally more abundant in the insect forms compared with the blood stage of the parasite, including several proteins associated with differentiation. We conclude that suramin has multiple and complex effects on trypanosomes, but unexpectedly partially activates mitochondrial ATP-generating activity. We propose that despite apparent compensatory mechanisms in drug-challenged cells, the suramin-induced collapse of cellular ATP ultimately leads to trypanosome cell death.

• Keywords
• Trypanosoma brucei, differentiation, drug action, drug mechanisms, energy homeostasis, glycosomes, metabolomics, parasite metabolism, polypharmacology, proteomics, sleeping sickness, suramin, trypanosome,
• MeSH
• Adenosine Triphosphate metabolism   MeSH
• Energy Metabolism drug effects   MeSH
• Flagella drug effects   metabolism   ultrastructure   MeSH
• Glycolysis drug effects   MeSH
• Pyruvic Acid metabolism   MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Metabolome drug effects   MeSH
• Microbodies drug effects   metabolism   ultrastructure   MeSH
• Mitochondria drug effects   metabolism   ultrastructure   MeSH
• Models, Molecular MeSH
• Proline metabolism   MeSH
• Proteome metabolism   MeSH
• Proton-Translocating ATPases metabolism   MeSH
• Protozoan Proteins metabolism   MeSH
• Suramin pharmacology   MeSH
• Trypanosoma brucei brucei metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adenosine Triphosphate MeSH
• Pyruvic Acid MeSH
• Proline MeSH
• Proteome MeSH
• Proton-Translocating ATPases MeSH
• Protozoan Proteins MeSH
• Suramin MeSH

Mitochondrial metabolic remodeling is a hallmark of the Trypanosoma brucei digenetic life cycle because the insect stage utilizes a cost-effective oxidative phosphorylation (OxPhos) to generate ATP, while bloodstream cells switch to aerobic glycolysis. Due to difficulties in acquiring enough parasites from the tsetse fly vector, the dynamics of the parasite's metabolic rewiring in the vector have remained obscure. Here, we took advantage of in vitro-induced differentiation to follow changes at the RNA, protein, and metabolite levels. This multi-omics and cell-based profiling showed an immediate redirection of electron flow from the cytochrome-mediated pathway to an alternative oxidase (AOX), an increase in proline consumption, elevated activity of complex II, and certain tricarboxylic acid (TCA) cycle enzymes, which led to mitochondrial membrane hyperpolarization and increased reactive oxygen species (ROS) levels. Interestingly, these ROS molecules appear to act as signaling molecules driving developmental progression because ectopic expression of catalase, a ROS scavenger, halted the in vitro-induced differentiation. Our results provide insights into the mechanisms of the parasite's mitochondrial rewiring and reinforce the emerging concept that mitochondria act as signaling organelles through release of ROS to drive cellular differentiation.

• MeSH
• Adenosine Triphosphate biosynthesis   MeSH
• Cell Differentiation drug effects   MeSH
• Cell Respiration drug effects   MeSH
• Cell Line MeSH
• Electrons MeSH
• Glucose pharmacology   MeSH
• Membrane Potential, Mitochondrial drug effects   MeSH
• Metabolic Networks and Pathways drug effects   MeSH
• Metabolomics * MeSH
• Mitochondrial Proteins metabolism   MeSH
• Mitochondria drug effects   metabolism   MeSH
• Oxidation-Reduction MeSH
• Oxidoreductases metabolism   MeSH
• Proline metabolism   MeSH
• Proteome metabolism   MeSH
• Protozoan Proteins metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Plant Proteins metabolism   MeSH
• Signal Transduction MeSH
• Transcriptome genetics   MeSH
• Electron Transport drug effects   MeSH
• Trypanosoma brucei brucei drug effects   genetics   growth & development   metabolism   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Adenosine Triphosphate MeSH
• alternative oxidase MeSH Browser
• Glucose MeSH
• Mitochondrial Proteins MeSH
• Oxidoreductases MeSH
• Proline MeSH
• Proteome MeSH
• Protozoan Proteins MeSH
• Reactive Oxygen Species MeSH
• Plant Proteins MeSH