Subrtova 2013 Abstract MiP2013

Subrtova K, Panicucci B, Zikova A (2013) Hypothetical Trypanosoma protein helps to anchor the F1ATPase moiety to the mitochondrial membrane. Mitochondr Physiol Network 18.08.

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MiP2013, Book of Abstracts Open Access

Subrtova K, Panicucci B, Zikova A (2013)

Event: MiPNet18.08_MiP2013

Trypanosoma brucei is a parasitic flagellate that causes devastating diseases of humans and lifestock. The infective form dwells in the glucose rich environment of mammalian blood and generate energy solely via glycolysis. In consequence, the bloodstream stage single mitochondrion is highly reduced lacking key Krebs cycle enzymes and traditional cytochrome mediated respiratory chain. Interestingly, the essential mitochondrial membrane potential (Δψ_mt) is maintained by hydrolytic activity of the unique FoF1-ATPase, which contains several trypanosoma specific subunits of unknown function [1].

We determined that one of the largest novel subunit, Tb2930 (43 kDa), is membrane-bound and localizes into monomeric and multimeric assemblies of the FoF1-ATPase. RNAi silencing of Tb2930 led to a significant decrease of Δψ_mt and consequently to T. brucei growth inhibition, indicating that the FoF1-ATPase is not functioning properly even though its structural intergrity seems to be almost unchanged. To further explore the function of this protein, we employed naturally occuring trypanosoma strain that lacks mtDNA (dyskinetoplastic, Dk) including subunit a, an essential component of the Fo-moiety and proton pore. These Dk cells maintain Δψ_mt by electrogenic exchange of ATP4-/ADP3- by the ATP/ADP carrier (AAC) and hydrolytic activity of the soluble F1-ATPase [2]. So far, it has been assumed that only the F1-moiety subunits are present and will be essential for these parasites. Interestingly, glycerol gradient sedimentation and native electrophoresis of Dk mitochondria revealed the presence of high molecular weight ATPase complexes that correspond to the bloodstream stage monomeric and multimeric FoF1-ATPase. Furthermore, the Tb2930 subunit is expressed in Dk cells and co-sediments with these high molecular weight membrane bound complexes. The RNAi study demonstrated that Tb2930 subunit is essential for Dk trypanosoma cells and crucial for maintaining Δψ_mt. Importantly, upon ablation of Tb2930 we observed a shift of the FoF1-ATPase complexes to the lower S-values on glycerol gradient, where the free F1-ATPase sediments, indicating changes in the structural integrity of the Dk FoF1-ATPase. In conclusion, we propose that Tb2930 is responsible for connecting the Dk F1-ATPase to the mitochondrial membrane in the absence of subunit a of the Fo-moiety, thus increasing the efficiency of the functional association between F1-ATPase and AAC.

• O2k-Network Lab: CZ Ceske Budejovice Zikova A

Labels: MiParea: mtDNA;mt-genetics, Comparative MiP;environmental MiP 

Organism: Other mammals, Protists 

Preparation: Intact organism, Isolated mitochondria  Enzyme: Complex V;ATP synthase  Regulation: mt-Membrane potential 

MiP2013 

Affiliations and author contributions

1 - Faculty of Science, University of South Bohemia, Czech Republic; 2 - Laboratory of Functional Genomics of Protists, Dept of Molecular Parasitology, Institute of Parasitology, Czech Republic. - Email: [email protected]

References

1. Zíková A, Schnaufer A, Dalley R, Panigrahi AK, Stuart KD (2009) The F0F1-ATP synthase complex contains novel subunits and is essential for procyclic Trypanosoma brucei. PLoS pathog 5: e1000436.
2. Schnaufer A, Clark-Walker GD, Steinberg AG, Stuart KD (2005) The F1-ATP synthase complex in bloodstream stage trypanosomes has an unusual and essential function. EMBO J 24: 4029–4040.