Mitochondrial Contact Site and Cristae Organization System and F1FO-ATP Synthase Crosstalk Is a Fundamental Property of Mitochondrial Cristae

Mitochondrial cristae are polymorphic invaginations of the inner membrane that are the fabric of cellular respiration. Both the mitochondrial contact site and cristae organization system (MICOS) and the F1FO-ATP synthase are vital for sculpting cristae by opposing membrane-bending forces. While MICOS promotes negative curvature at crista junctions, dimeric F1FO-ATP synthase is crucial for positive curvature at crista rims. Crosstalk between these two complexes has been observed in baker's yeast, the model organism of the Opisthokonta supergroup. Here, we report that this property is con-served in Trypanosoma brucei, a member of the Discoba clade that separated from the Opisthokonta similar to 2 billion years ago. Specifically, one of the paralogs of the core MICOS subunit Mic10 interacts with dimeric F1FO-ATP synthase, whereas the other core Mic60 subunit has a counteractive effect on F1FO-ATP synthase oligomerization. This is evoca-tive of the nature of MICOS-F1FO-ATP synthase crosstalk in yeast, which is remarkable given the diversification that these two complexes have undergone during almost 2 eons of independent evolution. Furthermore, we identified a highly diverged, putative homolog of subunit e, which is essential for the stability of F1FO-ATP synthase dimers in yeast. Just like subunit e, it is preferentially associated with dimers and interacts with Mic10, and its silencing results in severe defects to cristae and the disintegration of F1FO-ATP synthase dimers. Our findings indicate that crosstalk between MICOS and dimeric F1FO-ATP synthase is a fundamental property impacting crista shape throughout eukaryotes. IMPORTANCE Mitochondria have undergone profound diversification in separate line-ages that have radiated since the last common ancestor of eukaryotes some eons ago. Most eukaryotes are unicellular protists, including etiological agents of infec-tious diseases, like Trypanosoma brucei. Thus, the study of a broad range of protists can reveal fundamental features shared by all eukaryotes and lineage-specific inno-vations. Here, we report that two different protein complexes, MICOS and F1FO-ATP synthase, known to affect mitochondrial architecture, undergo crosstalk in T. brucei, just as in baker's yeast. This is remarkable considering that these complexes have otherwise undergone many changes during their almost 2 billion years of independ-ent evolution. Thus, this crosstalk is a fundamental property needed to maintain proper mitochondrial structure even if the constituent players considerably diverged.

Automated summary

Mitochondrial cristae are shaped by the interaction between the MICOS and F1FO-ATP synthase complexes, promoting negative and positive curvature respectively. This crosstalk is conserved in different eukaryotic lineages, such as baker's yeast and Trypanosoma brucei, despite significant evolutionary divergence between the complexes.