The Role of ATP Synthase Subunit e (ATP5I) in Mediating the Metabolic and Antiproliferative Effects of Biguanides

Here we identify the subunit e of F ₁ F _o -ATP synthase (ATP5I) as a target of medicinal biguanides. ATP5I maintains the stability of F ₁ F _o -ATP synthase dimers which is crucial for shaping cristae morphology. Although its roles have been mainly studied in yeast models, its function in cellular energy metabolism within the context of cancer remains poorly characterized. In this study, we demonstrate that ATP5I interacts with a biguanide analogue in vitro and disabling its expression by CRISPR-Cas9 in pancreatic cancer cells leads to the same phenotype as biguanide treated cells including a decrease in the levels of some respiratory complex subunits, mitochondrial morphology alterations, inhibition of oxidative phosphorylation (OXPHOS) and a compensatory increase in glycolysis. Moreover, ATP5I knockout (KO) cells exhibit resistance to the antiproliferative effects of biguanides, but reintroduction of ATP5I rescues the metabolic and anti-proliferative effects of metformin and phenformin. These findings highlight ATP5I as a significant antineoplastic mitochondrial target of medicinal biguanides, opening new opportunities for the development of mitochondrial-targeted therapies.