bims-resufa 2020-10-04 papers

Issue of 2020–10–04
three papers selected by
Vera Strogolova, Marquette University

Cells. 2020 Sep 29. pii: E2197. [Epub ahead of print]9(10):

Hypoxia Promotes Mitochondrial Complex I Abundance via HIF-1α in Complex III and Complex IV Eficient Cells.

Amy Saldana-Caboverde, Nadee Nissanka, Sofia Garcia, Anne Lombès, Francisca Diaz.

Murine fibroblasts deficient in mitochondria respiratory complexes III (CIII) and IV (CIV) produced by either the ablation of Uqcrfs1 (encoding for Rieske iron sulfur protein, RISP) or Cox10 (encoding for protoheme IX farnesyltransferase, COX10) genes, respectively, showed a pleiotropic effect in complex I (CI). Exposure to 1-5% oxygen increased the levels of CI in both RISP and COX10 KO fibroblasts. De novo assembly of the respiratory complexes occurred at a faster rate and to higher levels in 1% oxygen compared to normoxia in both RISP and COX10 KO fibroblasts. Hypoxia did not affect the levels of assembly of CIII in the COX10 KO fibroblasts nor abrogated the genetic defect impairing CIV assembly. Mitochondrial signaling involving reactive oxygen species (ROS) has been implicated as necessary for HIF-1α stabilization in hypoxia. We did not observe increased ROS production in hypoxia. Exposure to low oxygen levels stabilized HIF-1α and increased CI levels in RISP and COX10 KO fibroblasts. Knockdown of HIF-1α during hypoxic conditions abrogated the beneficial effect of hypoxia on the stability/assembly of CI. These findings demonstrate that oxygen and HIF-1α regulate the assembly of respiratory complexes.

Keywords: COX10; HIF-1α; Rieske iron sulfur protein; complex I; complex III; complex IV; hypoxia; mitochondrial respiratory supercomplexes; oxidative phosphorylation

DOI: https://doi.org/10.3390/cells9102197

Int J Mol Sci. 2020 Sep 30. pii: E7254. [Epub ahead of print]21(19):

Functions of Cytochrome c oxidase Assembly Factors.

Shane A Watson, Gavin P McStay.

Cytochrome c oxidase is the terminal complex of eukaryotic oxidative phosphorylation in mitochondria. This process couples the reduction of electron carriers during metabolism to the reduction of molecular oxygen to water and translocation of protons from the internal mitochondrial matrix to the inter-membrane space. The electrochemical gradient formed is used to generate chemical energy in the form of adenosine triphosphate to power vital cellular processes. Cytochrome c oxidase and most oxidative phosphorylation complexes are the product of the nuclear and mitochondrial genomes. This poses a series of topological and temporal steps that must be completed to ensure efficient assembly of the functional enzyme. Many assembly factors have evolved to perform these steps for insertion of protein into the inner mitochondrial membrane, maturation of the polypeptide, incorporation of co-factors and prosthetic groups and to regulate this process. Much of the information about each of these assembly factors has been gleaned from use of the single cell eukaryote Saccharomyces cerevisiae and also mutations responsible for human disease. This review will focus on the assembly factors of cytochrome c oxidase to highlight some of the outstanding questions in the assembly of this vital enzyme complex.

Keywords: cytochrome c oxidase; electron transport chain; mitochondria; oxidative phosphorylation

DOI: https://doi.org/10.3390/ijms21197254

STAR Protoc. 2020 Sep 18. pii: 100089. [Epub ahead of print]1(2):

Protocol for the Analysis of Yeast and Human Mitochondrial Respiratory Chain Complexes and Supercomplexes by Blue Native Electrophoresis.

Alba Timón-Gómez, Rafael Pérez-Pérez, Eva Nyvltova, Cristina Ugalde, Flavia Fontanesi, Antoni Barrientos.

By using negatively charged Coomassie brilliant blue G-250 dye to induce a charge shift on proteins, blue native polyacrylamide gel electrophoresis (BN-PAGE) allows resolution of enzymatically active multiprotein complexes extracted from cellular or subcellular lysates while retaining their native conformation. BN-PAGE was first developed to analyze the size, composition, and relative abundance of the complexes and supercomplexes that form the mitochondrial respiratory chain and OXPHOS system. Here, we present a detailed protocol of BN-PAGE to obtain robust and reproducible results. For complete details on the use and execution of this protocol, please refer to Lobo-Jarne et al. (2018) and Timón-Gómez et al. (2020).

DOI: https://doi.org/10.1016/j.xpro.2020.100089