Origins and consequences of kinetoplast loss in trypanosome
The kinetoplast is the large mitochondrial genome present in the eponymous Kinetoplastida. African trypanosomes can lose their kinetoplast DNA (kDNA), however, when the nuclear-encoded gamma subunit of the mitochondrial ATP-synthase (g-ATPase) is mutated. These mutations are also associated with multidrug resistance, tsetse-fly independent mechanical transmission, and geographical spread of these parasites beyond Africa. Here we engineer kinetoplast-independent kinetoplastids and explore origins and consequences of kDNA loss in Trypanosoma brucei. We used oligo targeting to edit the native g-ATPase gene, and selection with the ATP-synthase targeting drug oligomycin to enrich the desired mutants. Using this approach, we identified novel M282F, M282W, and M282Y mutants, and subsequently generated precision-edited strains expressing the M282F mutant or the previously described L262P or A273P mutants. These heterozygous mutants retained sensitivity to the kDNA-targeting drug acriflavine, however, and failed to yield kDNA negative cells following acriflavine selection. In contrast, T. brucei with a homozygous M282F edit were acriflavine resistant and readily tolerated acriflavine-induced kDNA loss. Proteomics analysis of the homozygous mutants revealed highly specific depletion of ATP synthase-associated proteins. Complete kDNA-loss in these cells was associated with substantial depletion of kDNA-binding proteins and mitochondrial RNA-processing factors. In contrast, mitochondrial membrane-associated transporters were increased in abundance. These results reveal g-ATPase defects that are analogous to a broken camshaft at the core of the ATP synthase rotary motor. In summary, T. brucei cells with a bi-allelic g-ATPase defect assemble a remodelled ATP synthase, and readily tolerate kDNA-loss, accompanied by substantial remodelling of the mitochondrial proteome.