Mitochondria are widely known for being the major site of ATP production in cells. The two enzyme pathways are oxidative phosphorylation (OXPHOS) and the tricarboxylic acid (TCA) cycle. The only structural link between these two systems was thought to be succinate dehydrogenase (complex II).

A research team, led by Nils-Göran Larsson (Karolinska Institute) and Albert J. R. Heck (Utrecht University), wondered if there might be other connections. They used multiple procedures, including in-solution crosslinking mass spectrometry, to determine the location of ATP synthase in multiple mouse models and tissues. They found that ATP synthase (complex V) interacts with several TCA enzymes. The results were published in the journal Nature Communications.

The researchers found that portions of ATP synthase interact with the TCA cycle enzymes. They also showed that disrupting mitochondrial DNA gene expression destabilizes ATP synthase and induces additional interactions with the TCA cycle. They also took advantage of heart- and skeletal-muscle-specific Lrpprc-knockout mice. Using this well-established model of impaired mitochondrial gene expression, the team found that ATP synthase was remodeled and increased the interactions with various metabolic proteins in the mitochondrial matrix.

The study showed that ATP synthase is remodeled in response to impaired gene expression. This work documents how mitochondria may adapt their metabolism to accommodate the loss of key mitochondrial enzymes.

A Statement of Significance by Drs. Larsson and Misic

Our study adds a new dimension to our understanding of mitochondrial energy metabolism by revealing previously unrecognized spatial connections between ATP synthase and several TCA-cycle enzymes. These findings suggest that the molecular organization of mitochondrial energy metabolism is more interconnected than previously appreciated. Particularly intriguing is the observation that these interactions become more prominent when mitochondrial gene expression is impaired, suggesting that the physical organization of metabolic enzymes is dynamic and undergoes remodeling during mitochondrial dysfunction. Although the physiological significance of these interactions remains to be established, they raise important questions about whether such rearrangements contribute to metabolic adaptation under conditions of impaired energy production. More broadly, our findings provide a new perspective on how mitochondrial metabolic machinery is organized and remodeled, opening new avenues for understanding mitochondrial function in health and disease.

A Conversation with the Authors

MitoWorld: Can you give us an idea of what directions your research might take to further advance the findings of the current paper?

Drs. Larsson and Misic: We have a long-standing interest in the organization of the respiratory chain in physiology and disease. Why do the respiratory chain complexes from supercomplexes? We previously found that the supercomplexes do not increase the efficiency of the respiratory chain or prevent ROS production. We now report unexpected novel connections between the ATP synthase and TCA cycle enzymes.

MitoWorld: Your results show that ATP synthase interacts in complex ways with multiple TCA enzymes that are affected by mtDNA mutations. Are these many interactions simply to facilitate energy production or is there another rationale?

Drs. Larsson and Misic: The physiological importance of the interactions between the ATP synthase and the TCA cycle enzymes is unknown. These interactions increase when mtDNA gene expression is impaired and may provide a compensatory mechanism.

MitoWorld: The ability of the multi-enzyme complexes to adapt to different metabolic demands is amazing. Can you speculate on the mechanism that allows the interactions to rearrange themselves under these circumstances?

Drs. Larsson and Misic: Our data show a protein-protein interaction between the ATP synthase and some TCA cycle enzymes, such as malate dehydrogenase (MDH). Interestingly, a recent Cell paper on proteomics of microorganisms has shown that Acanthamoeba has a stable interaction between ATP synthase and MDH, arguing that this interaction may be important for metabolism.

MitoWorld: XL-MS is a powerful tool for exploring protein interactions. Do you plan to use it to examine other aspects of OXPHOS?

Drs. Larsson and Misic: We already used it to study the organization of respiratory chain supercomplexes in the mitochondrial inner membrane.

MitoWorld: Do your findings have any potential clinical applications, and if so, do you have any plans to follow up on those? 

Drs. Larsson and Misic: Our study is a basic science contribution and much more work is needed to determine if the interactions we report can provide a target for drug development.

Reference

Pérez Pañeda L, Misic J, Kadavá T, Larsson NG, Heck AJ (2026) Investigating the relationship between ATP synthase and the TCA cycle by crosslinking mass spectrometry. Nature Communications 17(1): 5563. https://www.nature.com/articles/s41467-026-74730-5.pdf