Regulation of Cancer Metabolism by F-ATP synthase inhibitory factor 1: Interactions with c-Myc and PGC1α

Cancer cells has the ability to alter cellular metabolism to enable them to sustain higher rates of proliferation and survive even in harsh microenvironmental conditions. This metabolic reprogramming phenomena gives advantage to tumor where cancer cells frequently switch their energy production to a form of glucose metabolism known as aerobic glycolysis. This shift allows cancer cells to produce energy more rapidly, though less efficiently, to meet the increased demands of growth and proliferation. The F-ATP synthase inhibitory factor 1 (IF1) plays a significant role in the metabolic reprogramming of cancer cells. F-ATP synthase which is an essential mitochondrial enzyme synthesizes ATP using the proton gradient generated by the electron transport chain during oxidative phosphorylation. IF1 binds to F-ATP synthase and inhibits its activity. There is an urgent need to understand these metabolic shifts to design targeted therapies aimed at disrupting the cancer metabolic pathways.

To address this challenge, a new study published in Frontiers in Oncology and led by Dr. Lishu Guo and Dr. Zhenglong Gu examined the role of IF1 in regulating metabolic reprogramming in cancer cells, particularly through its interactions with the transcription factors c-Myc and PGC1α.  The team started by examining the expression levels of IF1, c-Myc, and PGC1α in cancer cell lines using western blot analysis. They also investigated the localization of these proteins within the cells, particularly focusing on their presence in mitochondria, using immunofluorescence staining and confocal microscopy. The authors found that IF1 expression varied among different cell lines and correlates with the metabolic phenotype of the cells. Both c-Myc and PGC1α were found to localize to the mitochondria, a process that appeared to be IF1-dependent, especially under conditions of mitochondrial stress. They used co-immunoprecipitation assays to explore the physical interactions between IF1 and Thr-58 phosphorylated c-Myc, as well as between IF1 and PGC1α. These experiments were conducted in both the cytosolic and mitochondrial fractions to confirm the specificity of these interactions. The researchers found IF1 directly bind to Thr-58 phosphorylated c-Myc and PGC1α in mitochondria, suggesting a targeted regulatory mechanism that influences mitochondrial function and metabolic reprogramming. When the researchers employed the Seahorse XF Analyzer to measure changes in the metabolic profile of cancer cells following the manipulation of IF1, c-Myc, and PGC1α levels which involves assessing the rates of glycolysis and oxidative phosphorylation under various conditions, including IF1 knockout and overexpression, they observed that ablation of IF1 led to an increase in oxidative phosphorylation and a decrease in glycolytic activity, indicating a metabolic shift from glycolysis to oxidative metabolism. Conversely, overexpression of IF1 promoted glycolysis, supporting the Warburg effect observed in cancer cells. The authors’ data also showed that the interactions of IF1 with c-Myc and PGC1α are crucial for these metabolic shifts.

Moreover, the authors performed CRISPR/Cas9 technology to create IF1 knockout cell lines. This allowed the team to dissect the role of IF1 in metabolic regulation without the confounding effects of endogenous IF1. The team demonstrated IF1 knockout cells to have a marked decrease in the interaction with c-Myc and PGC1α, further confirming the essential role of IF1 in regulating these interactions and their metabolic consequences. Furthermore, the researchers exposed cancer cells to high glucose conditions to simulate the hyperglycemic tumor microenvironment. They then assessed the impact of this condition on the localization of c-Myc and Thr-58 phosphorylated c-Myc to mitochondria and their interaction with IF1. They observed enhanced mitochondrial localization of c-Myc and Thr-58 phosphorylated c-Myc and its interaction with IF1 in high glucose conditions, suggesting that IF1-mediated metabolic reprogramming is responsive to environmental glucose levels. PGC1α, a master regulator of mitochondrial biogenesis and oxidative metabolism, is another critical player in metabolic reprogramming. The interaction of IF1 with PGC1α inhibits its activity, further contributing to the shift towards glycolysis. This inhibition of PGC1α by IF1 is a critical mechanism through which cancer cells adapt their metabolism to proliferate and survive under various stress conditions, including hypoxia.

In conclusion, this work conducted by the authors advances our understanding of the complex molecular interactions that underpin metabolic reprogramming in cancer cells. The authors demonstrated the central role of IF1 in regulating the activity of c-Myc and PGC1α, and this study opens new avenues for targeting metabolic pathways in cancer therapy. The balance between glycolysis and oxidative phosphorylation mediated by IF1represents a potential therapeutic target, offering the promise of more effective cancer treatments.