SCAN:Protein Dysfunction Accounts for Oxidative Stress Burden in a Rare Metabolic Disease

ITQB Scan Seminar

Title: Protein Dysfunction Accounts for Oxidative Stress Burden in a Rare Metabolic Disease

Speaker: João Rodrigues

From: Protein Biochemistry Folding and Stability Laboratory

Abstract:

Defects in the mitochondrial electron transfer flavoprotein (ETF) account for multiple acyl-CoA dehydrogenation deficiency (MADD), a disorder of fatty acid, amino acid and choline metabolism. Appearance of MADD symptoms associated with the mild phenotype is often determined by sporadic factors which remain largely unknown. In this respect, oxidative stress may be an important triggering factor for the development of MADD. Although it has been postulated that ETF could be a source of reactive oxygen species, no quantitative measurements have been performed so far. Here, we employ a newly developed methodology (1) to demonstrate that ETF produces significant amounts of both superoxide and hydrogen peroxide in the presence of its partner enzyme medium-chain acyl-CoA dehydrogenase (MCAD). Thermodynamic characterization of the complex MCAD:ETF showed that protein:protein interactions modulate the redox properties of the flavin cofactor in ETF and consequently its reactivity towards molecular oxygen (2). This is supported by observing that ETF-mediated production of reactive oxygen species is partially inhibited at high MCAD:ETF ratios, whereas it is enhanced at high ionic strength. We also found that pathogenic mutations which yield dysfunctional ETF proteins (3,4) lead to increased generation of reactive oxygen species. A possible role of these processes in mitochondrial dysfunction in metabolic disorders of fatty acid β-oxidation is discussed.

[1] Rodrigues, J. V.; Gomes, C. M. Enhanced superoxide and hydrogen peroxide detection in biological assays. Free Radic Biol Med 49:61-66; 2010.

[2] Rodrigues, J. V.; Gomes, C. M. Mechanism of Superoxide and Hydrogen Peroxide Generation by Human Electron Transfer Flavoprotein and Pathological Variants. Free Radic Biol Med accepted after minor revisions.

[3] Henriques, B. J.; Rodrigues, J. V.; Olsen, R. K.; Bross, P.; Gomes, C. M. Role of flavinylation in a mild variant of multiple acyl-CoA dehydrogenation deficiency: a molecular rationale for the effects of riboflavin supplementation. J Biol Chem 284:4222-4229; 2009.

[4] Henriques, B. J.; Bross, P.; Gomes, C. M. Mutational hotspots in electron transfer flavoprotein underlie defective folding and function in multiple acyl-CoA dehydrogenase deficiency. Biochim Biophys Acta 1802:1070-1077; 2010.