Proteomic analysis of U2OS cells treated with the dihydroorotate dehydrogenase (DHODH) inhibitor Brequinar

The mitochondrial respiratory chain assembles into higher order complexes termed supercomplexes (SCs) under certain physiological or metabolic stimuli. A small molecule screen developed by the lab identified DHODH inhibitors as potent activators of SC assembly in cancer cells. To investigate the proteomic regulation of SCs under nucleotide deficiency, we treated U2OS cells for 48 hours with Brequinar (500 nM). Proteomic analysis highlighted strong signatures of respiratory chain subunit abundance and peroxisomal-derived ether phospholipid synthesis enzymes. Bypassing DHODH inhibition through uridine supplementation prevented these alterations. These findings establish a coordinated cellular response to reduced nucleotide pools that stimulates ether phospholipid synthesis and respiratory chain supra-assembly.