20-24 – Impact of Co-enzyme Q10 deficiency on mitochondrial super complex biogenesis in the neuroblastoma cell line SH-SY5Y. .

Genetic mutations in the nuclear DNA or mitochondrial DNA that codes for mitochondrial proteins or proteins involved in mitochondrial activity leads to dysfunction of the oxidative phosphorylation, causing mitochondrial diseases. The nervous system heavily relies on ATP produced from oxidative phosphorylation and is steadily involved in patients with mitochondrial disorders like Leighs syndrome, Alpers syndrome, cognitive degeneration etc. The functions carried out by the mitochondria are dependent on five intramembrane complexes and two electron carriers (cytochrome c and COQ10), which are assisted by super complexes. Usually, therapeutic intervention involves COQ10 supplementation. COQ10 also called ubiquinone is found in all cell membranes and is synthesised in almost all mammalian cells by mitochondrial proteins, although the head and tail precursors are synthesised in the cytosol. The redox ability of benzoquinone provides COQ10 valuable functions inside the mitochondria, like the transport of electron. Additionally, COQ10 provides the electrochemical proton gradient that permits ATP synthesis and transports electrons from complexes 1 and 2 to complex 3. Also, COQ10 is a structural constituent of both Complexes 1 and 3 and influences complex I stability. Hence, COQ10 deficiency can manifest in various ways. In this study SHSY-5Y cell line was cultured and COQ10 deficiency was induced using treatment with para-aminobenzoic acid or PABA which is an inhibitor of COQ2(an enzyme involved in COQ10 synthesis). Initial experiments were carried out to determine optimal PABA concentration to obtain expected reduction in COQ10 levels. Furthermore, effects of COQ10 supplementation were assessed at 5 µM. Levels of respiratory chain complexes were determined at these PABA doses using Blue Native Gel electrophoresis and respiratory chain function was assessed using Sea horse extracellular flux assay.