The mevalonate pathway couples lipid metabolism to amino acid synthesis via ubiquinone-dependent redox control

The mevalonate pathway produces sterols and isoprenoids that support cancer cell growth, yet its broader metabolic functions remain incompletely defined. Here, we show that this pathway sustains amino acid biosynthesis by promoting mitochondrial NAD⁺ regeneration through ubiquinone-dependent electron transport. Statin-mediated inhibition of the mevalonate pathway impairs oxidative phosphorylation, lowers the NAD⁺/NADH ratio, and suppresses de novo serine and aspartate synthesis, thereby activating the GCN2–eIF2α–ATF4 amino acid deprivation response. The resulting depletion of serine-derived glycine and one-carbon units, together with reduced aspartate availability, limits purine and pyrimidine nucleotide production. Expression of the bacterial NADH oxidase LbNOX or the alternative oxidase AOX restores NAD⁺ levels and rescues statin-induced growth inhibition. These findings suggest that impaired NAD⁺ regeneration is a key mechanism contributing to the anti-proliferative activity of statins, linking the mevalonate pathway to mitochondrial electron transport– dependent control of amino acid metabolism.