bims-cytox1 2023-12-17 papers

Issue of 2023‒12‒17
three papers selected by
Gavin McStay, Liverpool John Moores University

Int J Mol Sci. 2023 Nov 23. pii: 16636. [Epub ahead of print]24(23):

Novel COX11 Mutations Associated with Mitochondrial Disorder: Functional Characterization in Patient Fibroblasts and Saccharomyces cerevisiae.

Chenelle A Caron-Godon, Stefania Della Vecchia, Alessandro Romano, Stefano Doccini, Flavio Dal Canto, Rosa Pasquariello, Anna Rubegni, Roberta Battini, Filippo Maria Santorelli, D Moira Glerum, Claudia Nesti.

Genetic defects in the nuclear encoded subunits and assembly factors of cytochrome c oxidase (mitochondrial complex IV) are very rare and are associated with a wide variety of phenotypes. Biallelic pathogenic variants in the COX11 protein were previously identified in two unrelated children with infantile-onset mitochondrial encephalopathies. Through comprehensive clinical, genetic and functional analyses, here we report on a new patient harboring novel heterozygous variants in COX11, presenting with Leigh-like features, and provide additional experimental evidence for a direct correlation between COX11 protein expression and sensitivity to oxidative stress. To sort out the contribution of the single mutations to the phenotype, we employed a multi-faceted approach using Saccharomyces cerevisiae as a genetically manipulable system, and in silico structure-based analysis of human COX11. Our results reveal differential effects of the two novel COX11 mutations on yeast growth, respiration, and cellular redox status, as well as their potential impact on human protein stability and function. Strikingly, the functional deficits observed in patient fibroblasts are recapitulated in yeast models, validating the conservation of COX11's role in mitochondrial integrity across evolutionarily distant organisms. This study not only expands the mutational landscape of COX11-associated mitochondrial disorders but also underscores the continued translational relevance of yeast models in dissecting complex molecular pathways.

Keywords: COX11 mutation; COX11 protein structure; mitochondrial diseases; yeast model

DOI: https://doi.org/10.3390/ijms242316636

Sci Adv. 2023 Dec 08. 9(49): eadh4179

Time-resolved serial crystallography to track the dynamics of carbon monoxide in the active site of cytochrome c oxidase.

Cytochrome c oxidase (CcO) is part of the respiratory chain and contributes to the electrochemical membrane gradient in mitochondria as well as in many bacteria, as it uses the energy released in the reduction of oxygen to pump protons across an energy-transducing biological membrane. Here, we use time-resolved serial femtosecond crystallography to study the structural response of the active site upon flash photolysis of carbon monoxide (CO) from the reduced heme a3 of ba3-type CcO. In contrast with the aa3-type enzyme, our data show how CO is stabilized on CuB through interactions with a transiently ordered water molecule. These results offer a structural explanation for the extended lifetime of the CuB-CO complex in ba3-type CcO and, by extension, the extremely high oxygen affinity of the enzyme.

DOI: https://doi.org/10.1126/sciadv.adh4179

Stem Cell Res Ther. 2023 Dec 10. 14(1): 357

COX6A2 deficiency leads to cardiac remodeling in human pluripotent stem cell-derived cardiomyocytes.

Mengqi Jiang, Yuanxiu Song, Xi Chen, Wenjing Lu, Min Zhu, Mingyu Wei, Feng Lan, Ming Cui, Yun Bai.

BACKGROUND: Cardiac remodeling is the initiating factor for the development of heart failure, which can result from various cardiomyopathies. Cytochrome c oxidase subunit 6A2 (COX6A2) is one of the components of cytochrome c oxidase that drives oxidative phosphorylation. The pathogenesis of myocardial remodeling caused by COX6A2 deficiency in humans remains unclear because there are no suitable research models. In this study, we established a COX6A2-deficient human cardiac myocyte (CM) model that mimics the human COX6A2 homozygous mutation and determined the effects of COX6A2 dysfunction and its underlying mechanism.METHODS: A human COX6A2 homozygous knockout cardiomyocyte model was established by combining CRISPR/Cas9 gene editing technology and hiPSC-directed differentiation technology. Cell model phenotypic assays were done to characterize the pathological features of the resulting COX6A2-deficient cardiomyocytes.
RESULTS: COX6A2 gene knockout did not affect the pluripotency and differentiation efficiency of hiPSCs. Myocardial cells with a COX6A2 gene knockout showed abnormal energy metabolism, increased oxidative stress levels, abnormal calcium transport activity, and decreased contractility. In addition, L-carnitine and trimetazidine significantly improved energy metabolism in the COX6A2-deficient human myocardial model.
CONCLUSIONS: We have established a COX6A2-deficient human cardiomyocyte model that exhibits abnormal energy metabolism, elevated oxidative stress levels, abnormal calcium transport, and reduced contractility. This model represents an important tool to gain insight into the mechanism of action of energy metabolism disorders resulting in myocardial remodeling, elucidate the gene-phenotype relationship of COX6A2 deficiency, and facilitate drug screening.

Keywords: COX6A2; CRISPR/Cas9; Cardiac remodeling; Drug discovery; Human cardiomyocyte; Oxidative stress; hiPSCs

DOI: https://doi.org/10.1186/s13287-023-03596-x