Clin Res Cardiol (2022). https://doi.org/10.1007/s00392-022-02002-5

BNIP3 regulates cardiac energy metabolism by interaction with F1FO ATP-synthase

A.-L. Beerlage1, S. Settelmeier1, H. Döpper1, J. Heinen-Weiler1, V. Giorgio2, T. Rassaf1, U. Hendgen-Cotta1

1Klinik für Kardiologie und Angiologie, Universitätsklinikum Essen, Essen; 2Biomedical and Neuromotor Sciences, University Bologna, Bologna, IT;

Background: Mitochondria are the main energy source of the heart and produce ATP via the electron transport chain (ETC). Cardiac contractility is highly dependent on proper mitochondrial function, and a decrease in myocardial ATP levels is frequently associated with cardiovascular disease. However, mitochondrial dysfunction remains an unmet therapeutic challenge. F1FO ATP-synthase, the last enzyme complex of the ETC, catalyzes the final step of generation of ATP by oxidative phosphorylation, determining the respiratory function of cardiac mitochondria. Increasing the available ATP pool during cardiovascular challenges by regulating the F1FO ATP synthase activity might significantly improve the clinical outcome of affected patients. BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3) is a member of the BCL2 family, which has been suggested to be involved in regulating the metabolic efficiency of neurons through interaction with the mitochondrial F1FO ATP synthase. Methods & Results: With native gel-electrophoresis, cardiac BNIP3 of C57BL/6J mice was first identified in higher oligomeric complexes in similar molecular weight range as mitochondrial F1FO ATP-synthase. Using 60Å-precise proximity-ligation assays to determine possible binding partners, F1FO ATP-synthase was uncovered for the first time as an interacting protein of BNIP3. This interaction was confirmed by co-immunoprecipitation of BNIP3 and F1FO ATP-synthase and by spatial localization using electron microscopy. Functional analysis using extracellular flux analyzer technology revealed significantly elevated mitochondrial respiratory activity in mice lacking BNIP3. Increased ATP levels in C57BL/6J mice after acute inhibition of BNIP3 confirmed the observed regulatory effect of BNIP3 on F1FO ATP-synthase activity. Elevated levels of phosphorylated proteins in BNIP3-depleted mice suggest a shift within the cardiac phosphoproteome attributable to a negative regulatory activity of BNIP3 on oxidative phosphorylation. Finally, depletion of BNIP3 in mice improves stress resistance with an augmented chronotropic capacity during dobutamine-induced cardiac stress. Conclusion: Depletion of BNIP3 suggests a regulatory role of BNIP3 in cardiac mitochondrial energy homeostasis via interaction with F1F0 ATP-synthase in oligomeric complexes. Since acute inhibition of BNIP3 activity allows positive modulation of cardiac performance by elevating the available ATP pool, this may serve as a beneficial treatment for patients with cardiovascular disease in the future.

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