Accessory subunit NUYM (NDUFS4) is required for stability of the electron input module and activity of mitochondrial complex I

Abstract

Mitochondrial complex I is an intricate 1MDa membrane protein complex with a central role in aerobic energy metabolism. The minimal form of complex I consists of fourteen central subunits that are conserved from bacteria to man. In addition, eukaryotic complex I comprises some 30 accessory subunits of largely unknown function. The gene for the accessory NDUFS4 subunit of human complex I is a hot spot for fatal pathogenic mutations in humans. We have deleted the gene for the orthologous NUYM subunit in the aerobic yeast Yarrowia lipolytica, an established model system to study eukaryotic complex I and complex I linked diseases. We observed assembly of complex I which lacked only subunit NUYM and retained weak interaction with assembly factor N7BML (human NDUFAF2). Absence of NUYM caused distortion of iron sulfur clusters of the electron input domain leading to decreased complex I activity and increased release of reactive oxygen species. We conclude that NUYM has an important stabilizing function for the electron input module of complex I and is essential for proper complex I function.

High-resolution cryo-EM structures of respiratory complex I: Mechanism, assembly, and disease

“…Our yeast genetic model system enables us to study the structural basis of NDUFS4-linked Leigh syndrome in detail. In a Y. lipolytica ndufs4 Δ strain, complex I levels dropped to ~40% of wild type, indicating a less efficient assembly process, and complex I lacking NDUFS4 was associated with the assembly factor NDUFAF2 ( 12 ). However, NDUFAF2 was lost during protein purification in detergent, suggesting weak interaction.…”

“…However, NDUFAF2 was lost during protein purification in detergent, suggesting weak interaction. Biochemical and spectroscopic analysis of the mutant complex indicated reduced electron transfer activity, increased ROS production, and prominent changes in the electron paramagnetic resonance (EPR) spectra of FeS clusters N1b and N3 ( 12 ).…”

“…Various Ndufs4 knockout mouse models were generated to study the physiology of complex I dysfunction but have failed to clarify the molecular basis of the disease ( 11 ). NDUFS4 stabilizes the N module ( 12 ) and is thought to play a role in complex I assembly linked with the assembly factor NDUFAF2. NDUFAF2 is a paralog of accessory subunit NDUFA12 ( 13 ).…”

The Mitochondrial Isoform of FASTK Modulates Nonopsonic Phagocytosis of Bacteria by Macrophages via Regulation of Respiratory Complex I

“…In this article, several lines of evidence implicate CI in the modulation of bacterial phagocytosis by macrophages: 1) FASTK ─/─ macrophages show decreased CI activity and increased nonopsonic bacterial phagocytosis, and the re-expression of mitoFASTK alone is able to rescue the phenotype; 2) treatment with rotenone, a specific inhibitor of CI, and shRNA-mediated silencing of NDUFS3 and NDUFS4 also lead to increased phagocytosis of nonopsonized bacteria by macrophages. NDUFS3 is an integral subunit of the Q module of the mitochondrial respiratory CI (26), whereas NDUFS4 is an accessory subunit required for stability of CI (27,40). Mutations in NDUSF3 and NDUFS4 genes result in Leigh syndrome, a progressive neurodegenerative disorder (41)(42)(43)(44).…”

Papel de la isoforma mitocondrial de FASTK en la modulación de la fagocitosis no opsónica de bacterias por los macrófagos

“…In this article, several lines of evidence implicate CI in the modulation of bacterial phagocytosis by macrophages: 1) FASTK ─/─ macrophages show decreased CI activity and increased nonopsonic bacterial phagocytosis, and the re-expression of mitoFASTK alone is able to rescue the phenotype; 2) treatment with rotenone, a specific inhibitor of CI, and shRNA-mediated silencing of NDUFS3 and NDUFS4 also lead to increased phagocytosis of nonopsonized bacteria by macrophages. NDUFS3 is an integral subunit of the Q module of the mitochondrial respiratory CI (26), whereas NDUFS4 is an accessory subunit required for stability of CI (27,40). Mutations in NDUSF3 and NDUFS4 genes result in Leigh syndrome, a progressive neurodegenerative disorder (41)(42)(43)(44).…”