Mitochondrial matrix RTN4IP1/OPA10 is an oxidoreductase for coenzyme Q synthesis

Abstract

<jats:title>Abstract</jats:title><jats:p>Targeting proximity-labeling enzymes to specific cellular locations is a viable strategy for profiling subcellular proteomes. Here, we generated transgenic mice (MAX-Tg) expressing a mitochondrial matrix-targeted ascorbate peroxidase. Comparative analysis of matrix proteomes from the muscle tissues showed differential enrichment of mitochondrial proteins. We found that reticulon 4-interacting protein 1 (RTN4IP1), also known as optic atrophy-10, is enriched in the mitochondrial matrix of muscle tissues and is an NADPH oxidoreductase. Interactome analysis and in vitro enzymatic assays revealed an essential role for RTN4IP1 in coenzyme Q (CoQ) biosynthesis by regulating the <jats:italic>O</jats:italic>-methylation activity of COQ3. <jats:italic>Rtn4ip1-</jats:italic>knockout myoblasts had markedly decreased CoQ<jats:sub>9</jats:sub> levels and impaired cellular respiration. Furthermore, muscle-specific knockdown of <jats:italic>d</jats:italic><jats:italic>Rtn4ip1</jats:italic> in flies resulted in impaired muscle function, which was reversed by dietary supplementation with soluble CoQ. Collectively, these results demonstrate that RTN4IP1 is a mitochondrial NAD(P)H oxidoreductase essential for supporting mitochondrial respiration activity in the muscle tissue.</jats:p>