bims-mitmed 2021-10-24 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2021–10–24
twenty papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

Quantitative analysis of mitochondrial morphologies in human induced pluripotent stem cells for Leigh syndrome.
Interrogating Mitochondrial Biology and Disease Using CRISPR/Cas9 Gene Editing.
Adult-Onset Leigh Syndrome due to an m.13513G>A Mutation.
Creating Cell Model 2.0 Using Patient Samples Carrying a Pathogenic Mitochondrial DNA Mutation: iPSC Approach for LHON.
Sub-Cellular Metabolomics Contributes Mitochondria-Specific Metabolic Insights to a Mouse Model of Leigh Syndrome.
Identification of a Novel m.3955G>A Variant in MT-ND1 Associated with Leigh Syndrome.
The Genetic Landscape of Mitochondrial Diseases in Spain: A Nationwide Call.
On the dynamic and even reversible nature of Leigh syndrome: Lessons from human imaging and mouse models.
An in vitro system to silence mitochondrial gene expression.
Expanding the phenotypic spectrum of BCS1L-related mitochondrial disease.
Ceramide accumulation induces mitophagy and impairs β-oxidation in PINK1 deficiency.
Multi-Omics Approach to Mitochondrial DNA Damage in Human Muscle Fibers.
Human COQ4 deficiency: delineating the clinical, metabolic and neuroimaging phenotypes.
Cardiolipin remodeling enables protein crowding in the inner mitochondrial membrane.
Mitochondrial dysfunction in the erythroid compartment.
Precise control of mitophagy through ubiquitin proteasome system and deubiquitin proteases and their dysfunction in Parkinson's disease.
Mitochondrial Mutations in Ethambutol-Induced Optic Neuropathy.
Celecoxib decreases mitochondrial complex IV activity and induces oxidative stress in isolated rat heart mitochondria: An analysis for its cardiotoxic adverse effect.
Mitophagy reporter mouse analysis reveals increased mitophagy activity in disuse-induced muscle atrophy.
Full-coverage regulations of autophagy by ROS: from induction to maturation.

Stem Cell Res. 2021 Oct 12. pii: S1873-5061(21)00419-0. [Epub ahead of print]57 102572

Quantitative analysis of mitochondrial morphologies in human induced pluripotent stem cells for Leigh syndrome.

Fibi Meshrkey, Ana Cabrera Ayuso, Raj R Rao, Shilpa Iyer.

  Mitochondria are dynamic organelles with wide range of morphologies contributing to regulating different signaling pathways and several cellular functions. Leigh syndrome (LS) is a classic pediatric mitochondrial disorder characterized by complex and variable clinical pathologies, and primarily affects the nervous system during early development. It is important to understand the differences between mitochondrial morphologies in healthy and diseased states so that focused therapies can target the disease during its early stages. In this study, we performed a comprehensive analysis of mitochondrial dynamics in five patient-derived human induced pluripotent stem cells (hiPSCs) containing different mutations associated with LS. Our results suggest that subtle alterations in mitochondrial morphologies are specific to the mtDNA variant. Three out of the five LS-hiPSCs exhibited characteristics consistent with fused mitochondria. To our knowledge, this is the first comprehensive study that quantifies mitochondrial dynamics in hiPSCs specific to mitochondrial disorders. In addition, we observed an overall decrease in mitochondrial membrane potential in all five LS-hiPSCs. A more thorough analysis of the correlations between mitochondrial dynamics, membrane potential dysfunction caused by mutations in the mtDNA in hiPSCs and differentiated derivatives will aid in identifying unique morphological signatures of various mitochondrial disorders during early stages of embryonic development.

Keywords:  Human induced pluripotent stem cells; Leigh syndrome; Mitochondrial disorders; Mitochondrial dynamics; Mitochondrial membrane potential; Mitochondrial morphology

DOI:  https://doi.org/10.1016/j.scr.2021.102572
Genes (Basel). 2021 Oct 12. pii: 1604. [Epub ahead of print]12(10):

Interrogating Mitochondrial Biology and Disease Using CRISPR/Cas9 Gene Editing.

Jia-Xin Tang, Angela Pyle, Robert W Taylor, Monika Oláhová.

  Mitochondrial disease originates from genetic changes that impact human bodily functions by disrupting the mitochondrial oxidative phosphorylation system. MitoCarta is a curated and published inventory that sheds light on the mitochondrial proteome, but the function of some mitochondrially-localised proteins remains poorly characterised. Consequently, various gene editing systems have been employed to uncover the involvement of these proteins in mitochondrial biology and disease. CRISPR/Cas9 is an efficient, versatile, and highly accurate genome editing tool that was first introduced over a decade ago and has since become an indispensable tool for targeted genetic manipulation in biological research. The broad spectrum of CRISPR/Cas9 applications serves as an attractive and tractable system to study genes and pathways that are essential for the regulation and maintenance of mitochondrial health. It has opened possibilities of generating reliable cell and animal models of human disease, and with further exploitation of the technology, large-scale genomic screenings have uncovered a wealth of fundamental mechanistic insights. In this review, we describe the applications of CRISPR/Cas9 system as a genome editing tool to uncover new insights into pathomechanisms of mitochondrial diseases and/or biological processes involved in mitochondrial function.

Keywords:  CRISPR/Cas9; cell and animal models; genome editing; genome-wide CRISPR libraries screening; mitochondrial biology; mitochondrial disease

DOI:  https://doi.org/10.3390/genes12101604
Intern Med. 2021 Oct 19.

Adult-Onset Leigh Syndrome due to an m.13513G>A Mutation.

Hiroaki Hirosawa, Takamasa Nukui, Kyo Noguchi, Yuji Nakatsuji.



Keywords:  Leigh syndrome; mitochondrial disease; renal failure

DOI:  https://doi.org/10.2169/internalmedicine.8445-21
Methods Mol Biol. 2021 Oct 21.

Creating Cell Model 2.0 Using Patient Samples Carrying a Pathogenic Mitochondrial DNA Mutation: iPSC Approach for LHON.

Pragya Singh, Tyler Bahr, Xiaoxu Zhao, Peiqing Hu, Marcel Daadi, TaoSheng Huang, Yidong Bai.

  Leber's Hereditary Optic Neuropathy is the most prevalent mitochondrial neurological disease caused by mutations in mitochondrial DNA encoded respiratory complex I subunits. Although the genetic origin for Leber's hereditary optic neuropathy was identified about 30 years ago, the underlying pathogenesis is still unclear primarily due to the lack of a relevant system or cell model. Current models are limited to lymphoblasts, fibroblasts, or cybrid cell lines. As the disease phenotype is limited to retinal ganglion cells, induced pluripotent stem cells will serve as an excellent model for studying this tissue-specific disease, elucidating its underlying molecular mechanisms, and identifying novel therapeutic targets. Here, we describe a detailed protocol for the generation of retinal ganglion cells, and also cardiomyocytes for proof of iPSC pluripotency.

Keywords:  Induced pluripotent stem cell; LHON; Retinal ganglion cells; mtDNA

DOI:  https://doi.org/10.1007/7651_2021_384
Metabolites. 2021 Sep 28. pii: 658. [Epub ahead of print]11(10):

Sub-Cellular Metabolomics Contributes Mitochondria-Specific Metabolic Insights to a Mouse Model of Leigh Syndrome.

Gunter van der Walt, Jeremie Z Lindeque, Shayne Mason, Roan Louw.

  Direct injury of mitochondrial respiratory chain (RC) complex I by Ndufs4 subunit mutations results in complex I deficiency (CID) and a progressive encephalomyopathy, known as Leigh syndrome. While mitochondrial, cytosolic and multi-organelle pathways are known to be involved in the neuromuscular LS pathogenesis, compartment-specific metabolomics has, to date, not been applied to murine models of CID. We thus hypothesized that sub-cellular metabolomics would be able to contribute organelle-specific insights to known Ndufs4 metabolic perturbations. To that end, whole brains and skeletal muscle from late-stage Ndufs4 mice and age/sex-matched controls were harvested for mitochondrial and cytosolic isolation. Untargeted 1H-NMR and semi-targeted LC-MS/MS metabolomics was applied to the resulting cell fractions, whereafter important variables (VIPs) were selected by univariate statistics. A predominant increase in multiple targeted amino acids was observed in whole-brain samples, with a more prominent effect at the mitochondrial level. Similar pathways were implicated in the muscle tissue, showing a greater depletion of core metabolites with a compartment-specific distribution, however. The altered metabolites expectedly implicate altered redox homeostasis, alternate RC fueling, one-carbon metabolism, urea cycling and dysregulated proteostasis to different degrees in the analyzed tissues. A first application of EDTA-chelated magnesium and calcium measurement by NMR also revealed tissue- and compartment-specific alterations, implicating stress response-related calcium redistribution between neural cell compartments, as well as whole-cell muscle magnesium depletion. Altogether, these results confirm the ability of compartment-specific metabolomics to capture known alterations related to Ndufs4 KO and CID while proving its worth in elucidating metabolic compartmentalization in said pathways that went undetected in the diluted whole-cell samples previously studied.

Keywords:  1H-NMR; LC-MS/MS; Ndufs4; complex I deficiency; cytosol; metabolomics; mitochondria; mitochondrial disease; sub-cellular metabolomics

DOI:  https://doi.org/10.3390/metabo11100658
Mitochondrion. 2021 Oct 14. pii: S1567-7249(21)00142-2. [Epub ahead of print]

Identification of a Novel m.3955G>A Variant in MT-ND1 Associated with Leigh Syndrome.

Manting Xu, Robert Kopajtich, Matthias Elstner, Hua Li, Zhimei Liu, Junling Wang, Holger Prokisch, Fang Fang.

  Leigh syndrome (LS) is one of the most common mitochondrial diseases in children, for which at least 90 causative genes have been identified. However, many LS patients have no genetic diagnosis, indicating that more disease-related genes remain to be identified. In this study, we identified a novel variant, m.3955G>A, in mitochondrially encoded NADH:ubiquinone oxidoreductase core subunit 1 (MT-ND1) in two unrelated LS patients, manifesting as infancy-onset frequent seizures, neurodegeneration, elevated lactate levels, and bilateral symmetrical lesions in the brainstem, basal ganglia, and thalamus. Transfer of the mutant mtDNA with m.3955G>A into cybrids disturbed the MT-ND1 expression and CI assembly, followed by remarkable mitochondrial dysfunction, reactive oxygen species production, and mitochondrial membrane potential reduction. Our findings demonstrated the pathogenicity of the novel m.3955G>A variant, and extend the spectrum of pathogenic mtDNA variants.

Keywords:  Leigh syndrome; MT-ND1; Novel mitochondrial DNA variant; cybrid cells

DOI:  https://doi.org/10.1016/j.mito.2021.10.002
Genes (Basel). 2021 Oct 09. pii: 1590. [Epub ahead of print]12(10):

The Genetic Landscape of Mitochondrial Diseases in Spain: A Nationwide Call.

Marcello Bellusci, Abraham J Paredes-Fuentes, Eduardo Ruiz-Pesini, Beatriz Gómez, Mitospain Working Group, Miguel A Martín, Julio Montoya, Rafael Artuch.

  The frequency of mitochondrial diseases (MD) has been scarcely documented, and only a few studies have reported data in certain specific geographical areas. In this study, we arranged a nationwide call in Spain to obtain a global estimate of the number of cases. A total of 3274 cases from 49 Spanish provinces were reported by 39 centres. Excluding duplicated and unsolved cases, 2761 patients harbouring pathogenic mutations in 140 genes were recruited between 1990 and 2020. A total of 508 patients exhibited mutations in nuclear DNA genes (75% paediatric patients) and 1105 in mitochondrial DNA genes (33% paediatric patients). A further 1148 cases harboured mutations in the MT-RNR1 gene (56% paediatric patients). The number of reported cases secondary to nuclear DNA mutations increased in 2014, owing to the implementation of next-generation sequencing technologies. Between 2014 and 2020, excepting MT-RNR1 cases, the incidence was 6.34 (95% CI: 5.71-6.97) cases per million inhabitants at the paediatric age and 1.36 (95% CI: 1.22-1.50) for adults. In conclusion, this is the first study to report nationwide epidemiological data for MD in Spain. The lack of identification of a remarkable number of mitochondrial genes necessitates the systematic application of high-throughput technologies in the routine diagnosis of MD.

Keywords:  Spanish registry; epidemiological data; incidence; mitochondrial DNA mutations; mitochondrial diseases; nuclear DNA mutations

DOI:  https://doi.org/10.3390/genes12101590
Curr Opin Neurobiol. 2021 Oct 13. pii: S0959-4388(21)00107-0. [Epub ahead of print]72 80-90

On the dynamic and even reversible nature of Leigh syndrome: Lessons from human imaging and mouse models.

Melissa A Walker, Maria Miranda, Amanda Allred, Vamsi K Mootha.

Leigh syndrome (LS) is a neurodegenerative disease characterized by bilaterally symmetric brainstem or basal ganglia lesions. More than 80 genes, largely impacting mitochondrial energy metabolism, can underlie LS, and no approved medicines exist. Described 70 years ago, LS was initially diagnosed by the characteristic, necrotic lesions on autopsy. It has been broadly assumed that antemortem neuroimaging abnormalities in these regions correspond to end-stage histopathology. However, clinical observations and animal studies suggest that neuroimaging findings may represent an intermediate state, that is more dynamic than previously appreciated, and even reversible. We review this literature, discuss related conditions that are treatable, and present two new LS cases with radiographic improvement. We review studies in which hypoxia reverses advanced LS in a mouse model. The fluctuating and potentially reversible nature of radiographic LS lesions will be important in clinical trial design. Better understanding of this plasticity could lead to new therapies.

DOI: https://doi.org/10.1016/j.conb.2021.09.006
Cell. 2021 Oct 11. pii: S0092-8674(21)01116-8. [Epub ahead of print]

An in vitro system to silence mitochondrial gene expression.

Luis Daniel Cruz-Zaragoza, Sven Dennerlein, Andreas Linden, Roya Yousefi, Elena Lavdovskaia, Abhishek Aich, Rebecca R Falk, Ridhima Gomkale, Thomas Schöndorf, Markus T Bohnsack, Ricarda Richter-Dennerlein, Henning Urlaub, Peter Rehling.

  The human mitochondrial genome encodes thirteen core subunits of the oxidative phosphorylation system, and defects in mitochondrial gene expression lead to severe neuromuscular disorders. However, the mechanisms of mitochondrial gene expression remain poorly understood due to a lack of experimental approaches to analyze these processes. Here, we present an in vitro system to silence translation in purified mitochondria. In vitro import of chemically synthesized precursor-morpholino hybrids allows us to target translation of individual mitochondrial mRNAs. By applying this approach, we conclude that the bicistronic, overlapping ATP8/ATP6 transcript is translated through a single ribosome/mRNA engagement. We show that recruitment of COX1 assembly factors to translating ribosomes depends on nascent chain formation. By defining mRNA-specific interactomes for COX1 and COX2, we reveal an unexpected function of the cytosolic oncofetal IGF2BP1, an RNA-binding protein, in mitochondrial translation. Our data provide insight into mitochondrial translation and innovative strategies to investigate mitochondrial gene expression.

Keywords:  IGF2BP1; antisense; mitochondria; mitochondrial ribosome; morpholino; oxidative phosphorylation; translation

DOI:  https://doi.org/10.1016/j.cell.2021.09.033
Ann Clin Transl Neurol. 2021 Oct 18.

Expanding the phenotypic spectrum of BCS1L-related mitochondrial disease.

Omar Hikmat, Pirjo Isohanni, Nandaki Keshavan, Matteo P Ferla, Elisa Fassone, Mary-Alice Abbott, Marcello Bellusci, Niklas Darin, David Dimmock, Daniele Ghezzi, Henry Houlden, Federica Invernizzi, Nazreen B Kamarus Jaman, Manju A Kurian, Eva Morava, Karin Naess, Juan Darío Ortigoza-Escobar, Sumit Parikh, Alessandra Pennisi, Giulia Barcia, Karin B Tylleskär, Damien Brackman, Saskia B Wortmann, Jenny C Taylor, Laurence A Bindoff, Vineta Fellman, Shamima Rahman.

OBJECTIVE: To delineate the full phenotypic spectrum of BCS1L-related disease, provide better understanding of the genotype-phenotype correlations and identify reliable prognostic disease markers.
METHODS: We performed a retrospective multinational cohort study of previously unpublished patients followed in 15 centres from 10 countries. Patients with confirmed biallelic pathogenic BCS1L variants were considered eligible. Clinical, laboratory, neuroimaging and genetic data were analysed. Patients were stratified into different groups based on the age of disease onset, whether homozygous or compound heterozygous for the c.232A>G (p.Ser78Gly) variant, and those with other pathogenic BCS1L variants.
RESULTS: Thirty-three patients were included. We found that growth failure, lactic acidosis, tubulopathy, hepatopathy and early death were more frequent in those with disease onset within the first month of life. In those with onset after 1 month, neurological features including movement disorders and seizures were more frequent. Novel phenotypes, particularly involving movement disorder, were identified in this group. The presence of the c.232A>G (p.Ser78Gly) variant was associated with significantly worse survival and exclusively found in those with disease onset within the first month of life, whilst other pathogenic BCS1L variants were more frequent in those with later symptom onset.
INTERPRETATION: The phenotypic spectrum of BCS1L-related disease comprises a continuum of clinical features rather than a set of separate syndromic clinical identities. Age of onset defines BCS1L-related disease clinically and early presentation is associated with poor prognosis. Genotype correlates with phenotype in the presence of the c.232A>G (p.Ser78Gly) variant.

DOI: https://doi.org/10.1002/acn3.51470
Proc Natl Acad Sci U S A. 2021 Oct 26. pii: e2025347118. [Epub ahead of print]118(43):

Ceramide accumulation induces mitophagy and impairs β-oxidation in PINK1 deficiency.

Melissa Vos, Marija Dulovic-Mahlow, Frida Mandik, Lisa Frese, Yuliia Kanana, Sokhna Haissatou Diaw, Julia Depperschmidt, Claudia Böhm, Jonas Rohr, Thora Lohnau, Inke R König, Christine Klein.

  Energy production via the mitochondrial electron transport chain (ETC) and mitophagy are two important processes affected in Parkinson's disease (PD). Interestingly, PINK1, mutations of which cause early-onset PD, plays a key role in both processes, suggesting that these two mechanisms are connected. However, the converging link of both pathways currently remains enigmatic. Recent findings demonstrated that lipid aggregation, along with defective mitochondria, is present in postmortem brains of PD patients. In addition, an increasing body of evidence shows that sphingolipids, including ceramide, are altered in PD, supporting the importance of lipids in the pathophysiology of PD. Here, we identified ceramide to play a crucial role in PINK1-related PD that was previously linked almost exclusively to mitochondrial dysfunction. We found ceramide to accumulate in mitochondria and to negatively affect mitochondrial function, most notably the ETC. Lowering ceramide levels improved mitochondrial phenotypes in pink1-mutant flies and PINK1-deficient patient-derived fibroblasts, showing that the effects of ceramide are evolutionarily conserved. In addition, ceramide accumulation provoked ceramide-induced mitophagy upon PINK1 deficiency. As a result of the ceramide accumulation, β-oxidation in PINK1 mutants was decreased, which was rescued by lowering ceramide levels. Furthermore, stimulation of β-oxidation was sufficient to rescue PINK1-deficient phenotypes. In conclusion, we discovered a cellular mechanism resulting from PD-causing loss of PINK1 and found a protective role of β-oxidation in ETC dysfunction, thus linking lipids and mitochondria in the pathophysiology of PINK1-related PD. Furthermore, our data nominate β-oxidation and ceramide as therapeutic targets for PD.

Keywords:  PINK1; Parkinson’s disease; ceramide; mitochondria; β-oxidation

DOI:  https://doi.org/10.1073/pnas.2025347118
Int J Mol Sci. 2021 Oct 14. pii: 11080. [Epub ahead of print]22(20):

Multi-Omics Approach to Mitochondrial DNA Damage in Human Muscle Fibers.

Matthias Elstner, Konrad Olszewski, Holger Prokisch, Thomas Klopstock, Marta Murgia.

  Mitochondrial DNA deletions affect energy metabolism at tissue-specific and cell-specific threshold levels, but the pathophysiological mechanisms determining cell fate remain poorly understood. Chronic progressive external ophthalmoplegia (CPEO) is caused by mtDNA deletions and characterized by a mosaic distribution of muscle fibers with defective cytochrome oxidase (COX) activity, interspersed among fibers with retained functional respiratory chain. We used diagnostic histochemistry to distinguish COX-negative from COX-positive fibers in nine muscle biopsies from CPEO patients and performed laser capture microdissection (LCM) coupled to genome-wide gene expression analysis. To gain molecular insight into the pathogenesis, we applied network and pathway analysis to highlight molecular differences of the COX-positive and COX-negative fiber transcriptome. We then integrated our results with proteomics data that we previously obtained comparing COX-positive and COX-negative fiber sections from three other patients. By virtue of the combination of LCM and a multi-omics approach, we here provide a comprehensive resource to tackle the pathogenic changes leading to progressive respiratory chain deficiency and disease in mitochondrial deletion syndromes. Our data show that COX-negative fibers upregulate transcripts involved in translational elongation and protein synthesis. Furthermore, based on functional annotation analysis, we find that mitochondrial transcripts are the most enriched among those with significantly different expression between COX-positive and COX-negative fibers, indicating that our unbiased large-scale approach resolves the core of the pathogenic changes. Further enrichments include transcripts encoding LIM domain proteins, ubiquitin ligases, proteins involved in RNA turnover, and, interestingly, cell cycle arrest and cell death. These pathways may thus have a functional association to the molecular pathogenesis of the disease. Overall, the transcriptome and proteome show a low degree of correlation in CPEO patients, suggesting a relevant contribution of post-transcriptional mechanisms in shaping this disease phenotype.

Keywords:  disease models; mtDNA deletions; myopathy; proteomics; skeletal muscle; transcriptomics

DOI:  https://doi.org/10.3390/ijms222011080
J Med Genet. 2021 Oct 16. pii: jmedgenet-2021-107729. [Epub ahead of print]

Human COQ4 deficiency: delineating the clinical, metabolic and neuroimaging phenotypes.

Lucia Laugwitz, Annette Seibt, Diran Herebian, Susana Peralta, Imke Kienzle, Rebecca Buchert, Ruth Falb, Darja Gauck, Amelie Müller, Mona Grimmel, Stefanie Beck-Woedel, Jan Kern, Karim Daliri, Pegah Katibeh, Katharina Danhauser, Steffen Leiz, Viola Alesi, Fabian Baertling, Gessica Vasco, Robert Steinfeld, Matias Wagner, Ahmet Okay Caglayan, Hakan Gumus, Margit Burmeister, Ertan Mayatepek, Diego Martinelli, Parag Mohan Tamhankar, Vasundhara Tamhankar, Pascal Joset, Katharina Steindl, Anita Rauch, Penelope E Bonnen, Tawfiq Froukh, Samuel Groeschel, Ingeborg Krägeloh-Mann, Tobias B Haack, Felix Distelmaier.

   BACKGROUND: Human coenzyme Q4 (COQ4) is essential for coenzyme Q10 (CoQ10) biosynthesis. Pathogenic variants in COQ4 cause childhood-onset neurodegeneration. We aimed to delineate the clinical spectrum and the cellular consequences of COQ4 deficiency.
METHODS: Clinical course and neuroradiological findings in a large cohort of paediatric patients with COQ4 deficiency were analysed. Functional studies in patient-derived cell lines were performed.
RESULTS: We characterised 44 individuals from 36 families with COQ4 deficiency (16 newly described). A total of 23 different variants were identified, including four novel variants in COQ4. Correlation analyses of clinical and neuroimaging findings revealed three disease patterns: type 1: early-onset phenotype with neonatal brain anomalies and epileptic encephalopathy; type 2: intermediate phenotype with distinct stroke-like lesions; and type 3: moderate phenotype with non-specific brain pathology and a stable disease course. The functional relevance of COQ4 variants was supported by in vitro studies using patient-derived fibroblast lines. Experiments revealed significantly decreased COQ4 protein levels, reduced levels of cellular CoQ10 and elevated levels of the metabolic intermediate 6-demethoxyubiquinone.
CONCLUSION: Our study describes the heterogeneous clinical presentation of COQ4 deficiency and identifies phenotypic subtypes. Cell-based studies support the pathogenic characteristics of COQ4 variants. Due to the insufficient clinical response to oral CoQ10 supplementation, alternative treatment strategies are warranted.

Keywords:  early diagnosis; epilepsy; nervous system diseases; pediatrics

DOI:  https://doi.org/10.1136/jmedgenet-2021-107729
EMBO J. 2021 Oct 18. e108428

Cardiolipin remodeling enables protein crowding in the inner mitochondrial membrane.

Yang Xu, Hediye Erdjument-Bromage, Colin K L Phoon, Thomas A Neubert, Mindong Ren, Michael Schlame.

  Mitochondrial cristae are extraordinarily crowded with proteins, which puts stress on the bilayer organization of lipids. We tested the hypothesis that the high concentration of proteins drives the tafazzin-catalyzed remodeling of fatty acids in cardiolipin, thereby reducing bilayer stress in the membrane. Specifically, we tested whether protein crowding induces cardiolipin remodeling and whether the lack of cardiolipin remodeling prevents the membrane from accumulating proteins. In vitro, the incorporation of large amounts of proteins into liposomes altered the outcome of the remodeling reaction. In yeast, the concentration of proteins involved in oxidative phosphorylation (OXPHOS) correlated with the cardiolipin composition. Genetic ablation of either remodeling or biosynthesis of cardiolipin caused a substantial drop in the surface density of OXPHOS proteins in the inner membrane of the mouse heart and Drosophila flight muscle mitochondria. Our data suggest that OXPHOS protein crowding induces cardiolipin remodelling and that remodeled cardiolipin supports the high concentration of these proteins in the inner mitochondrial membrane.

Keywords:  Barth syndrome; lipid-protein interaction; macromolecular crowding; mitochondria; oxidative phosphorylation

DOI:  https://doi.org/10.15252/embj.2021108428
Nat Immunol. 2021 Oct 20.

Mitochondrial dysfunction in the erythroid compartment.

Mariana J Kaplan.

DOI: https://doi.org/10.1038/s41590-021-01050-9
BMB Rep. 2021 Oct 22. pii: 5426. [Epub ahead of print]

Precise control of mitophagy through ubiquitin proteasome system and deubiquitin proteases and their dysfunction in Parkinson's disease.

Ga Hyun Park, Joon Hyung Park, Kwang Chul Chung.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the elderly population and is caused by the loss of dopaminergic neurons. PD has been predominantly attributed to mitochondrial dysfunction. The structural alteration of α-synuclein triggers toxic oligomer formation in the neurons, which greatly contributes to PD. In this article, we discuss the role of several familial PD-related proteins, such as α-synuclein, DJ-1, LRRK2, PINK1, and parkin in mitophagy, which entails a selective degradation of mitochondria via autophagy. Defective changes in mitochondrial dynamics and their biochemical and functional interaction induce the formation of toxic α-synuclein-containing protein aggregates in PD. In addition, these gene products play an essential role in ubiquitin proteasome system (UPS)-mediated proteolysis as well as mitophagy. Interestingly, a few deubiquitinating enzymes (DUBs) additionally modulate these two pathways negatively or positively. Based on these findings, we summarize the close relationship between several DUBs and the precise modulation of mitophagy. For example, the USP8, USP10, and USP15, among many DUBs are reported to specifically regulate the K48- or K63-linked de-ubiquitination reactions of several target proteins associated with the mitophagic process, in turn upregulating the mitophagy and protecting neuronal cells from α-synuclein-derived toxicity. In contrast, USP30 inhibits mitophagy by opposing parkin-mediated ubiquitination of target proteins. Furthermore, the association between these changes and PD pathogenesis will be discussed. Taken together, although the functional roles of several PD-related genes have yet to be fully understood, they are substantially associated with mitochondrial quality control as well as UPS. Therefore, a better understanding of their relationship provides valuable therapeutic clues for appropriate management strategies.
Front Cell Dev Biol. 2021 ;9 754676

Mitochondrial Mutations in Ethambutol-Induced Optic Neuropathy.

Xiao-Hui Zhang, Yue Xie, Quan-Gang Xu, Kai Cao, Ke Xu, Zi-Bing Jin, Yang Li, Shi-Hui Wei.

  Background: Ethambutol-induced optic neuropathy (EON) is a well-recognized ocular complication in patients who take ethambutol as a tuberculosis treatment. The aim of the current study was to investigate the presence of mitochondrial mutations, including OPA1 and Leber's hereditary optic neuropathy (LHON)-mitochondrial DNA (mtDNA), in patients with EON and to determine their effect on clinical features of these patients. Methods: All 47 patients underwent clinical evaluations, including best-corrected visual acuity, fundus examination, and color fundus photography; 37 patients were then followed up over time. Molecular screening methods, including PCR-based sequencing of the OPA1 gene and LHON-mtDNA mutations, together with targeted exome sequencing, were used to detect mutations. Results: We detected 15 OPA1 mutations in 18 patients and two LHON-mtDNA mutations in four patients, for an overall mutation detection rate of 46.8%. The mean presentation age was significantly younger in the patients with the mitochondrial mutations (27.5 years) than in those without mutations (48 years). Fundus examination revealed a greater prevalence of optic disc hyperemia in the patients with mutations (70.5%) than without mutations (48%). Half of the patients with mutations and 91% of the patients without mutations had improved vision. After adjusting for confounders, the logistic regression revealed that the patients with optic disc pallor on the first visit (p = 0.004) or the patients with the mitochondrial mutations (p < 0.001) had a poorer vision prognosis. Conclusion: Our results indicated that carriers with OPA1 mutations might be more vulnerable for the toxicity of EMB to develop EON.

Keywords:  OPA1; ethambutol; mitochondrial DNA; mutation; optic neuropathy

DOI:  https://doi.org/10.3389/fcell.2021.754676
J Biochem Mol Toxicol. 2021 Oct 19. e22934

Celecoxib decreases mitochondrial complex IV activity and induces oxidative stress in isolated rat heart mitochondria: An analysis for its cardiotoxic adverse effect.

Saman Atashbar, Zhaleh Jamali, Saleh Khezri, Ahmad Salimi.

  In spite of the cardiotoxic effect of selective cyclooxygenase-2 inhibitors, they are most widely used as anti-inflammatory and analgesic drugs. Today, valdecoxib and rofecoxib have been withdrawn in the market but celecoxib remains. In this study, we focused on an analysis of celecoxib toxic effects on isolated mitochondria. Isolated rat heart mitochondria were obtained using differential centrifugation. Using flow cytometry and biochemical assays, we searched succinate dehydrogenases, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) formation, mitochondrial swelling, ATP/ADP ratio, lipid peroxidation, and mitochondrial complexes activity in rat heart isolated mitochondria. Herein, our results indicated a significant decrease in the activity of complex IV after exposure with celecoxib (16 µg/ml). This decrease in the activity of complex IV is paralleled by the MMP collapse, ROS formation, mitochondrial swelling, depletion of ATP, and lipid peroxidation. For the first time, this introductory study has shown a significant decrease in the activity of complex IV and mitochondrial dysfunction after exposure with celecoxib in rat heart isolated mitochondria.

Keywords:  cardiotoxicity; celecoxib; heart; mitochondria; mitochondrial complexes

DOI:  https://doi.org/10.1002/jbt.22934
J Cell Physiol. 2021 Nov;236(11): 7612-7624

Mitophagy reporter mouse analysis reveals increased mitophagy activity in disuse-induced muscle atrophy.

Shun-Ichi Yamashita, Masanao Kyuuma, Keiichi Inoue, Yuki Hata, Ryu Kawada, Masaki Yamabi, Yasuyuki Fujii, Junko Sakagami, Tomoyuki Fukuda, Kentaro Furukawa, Satoshi Tsukamoto, Tomotake Kanki.

  Muscle disuse induces atrophy through increased reactive oxygen species (ROS) released from damaged mitochondria. Mitophagy, the autophagic degradation of mitochondria, is associated with increased ROS production. However, the mitophagy activity status during disuse-induced muscle atrophy has been a subject of debate. Here, we developed a new mitophagy reporter mouse line to examine how disuse affected mitophagy activity in skeletal muscles. Mice expressing tandem mCherry-EGFP proteins on mitochondria were then used to monitor the dynamics of mitophagy activity. The reporter mice demonstrated enhanced mitophagy activity and increased ROS production in atrophic soleus muscles following a 14-day hindlimb immobilization. Results also showed an increased expression of multiple mitophagy genes, including Bnip3, Bnip3l, and Park2. Our findings thus conclude that disuse enhances mitophagy activity and ROS production in atrophic skeletal muscles and suggests that mitophagy is a potential therapeutic target for disuse-induced muscle atrophy.

Keywords:  ROS; disuse-induced muscle atrophy; hindlimb immobilization; mitochondria; mitophagy

DOI:  https://doi.org/10.1002/jcp.30404
Autophagy. 2021 Oct 18. 1-16

Full-coverage regulations of autophagy by ROS: from induction to maturation.

Jing Zhou, Xin-Yu Li, Yu-Jia Liu, Ji Feng, Yong Wu, Han-Ming Shen, Guo-Dong Lu.

  Macroautophagy/autophagy is an evolutionarily well-conserved recycling process in response to stress conditions, including a burst of reactive oxygen species (ROS) production. High level of ROS attack key cellular macromolecules. Protein cysteinyl thiols or non-protein thiols as the major redox-sensitive targets thus constitute the first-line defense. Autophagy is unique, because it removes not only oxidized/damaged proteins but also bulky ROS-generating organelles (such as mitochondria and peroxisome) to restrict further ROS production. The oxidative regulations of autophagy occur in all processes of autophagy, from induction, phagophore nucleation, phagophore expansion, autophagosome maturation, cargo delivery to the lysosome, and finally to degradation of the cargo and recycling of the products, as well as autophagy gene transcription. Mechanically, these regulations are achieved through direct or indirect manners. Direct thiol oxidation of key proteins such as ATG4, ATM and TFEB are responsible for specific regulations in phagophore expansion, cargo recognition and autophagy gene transcription, respectively. Meanwhile, oxidation of certain redox-sensitive chaperone-like proteins (e.g. PRDX family members and PARK7) may impair a nonspecifically local reducing environment in the phagophore membrane, and influence BECN1-involved phagophore nucleation and mitophagy recognition. However, ROS do exhibit some inhibitory effects on autophagy through direct oxidation of key autophagy regulators such as ATG3, ATG7 and SENP3 proteins. SQSTM1 provides an alternative antioxidant mechanism when autophagy is unavailable or impaired. However, it is yet to be unraveled how cells evolve to equip proteins with different redox susceptibility and in their correct subcellular positions, and how cells fine-tune autophagy machinery in response to different levels of ROS.Abbreviations: AKT1/PKB: AKT serine/threonine kinase 1; AMPK: AMP-activated protein kinase; ATG: autophagy related; ATM: ATM serine/threonine kinase; BAX: BCL2 associated X, apoptosis regulator; BECN1: beclin 1; BH3: BCL2-homology-3; CAV1: caveolin 1; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CTSB: cathepsin B; CTSL: cathepsin L; DAPK: death associated protein kinase; ER: endoplasmic reticulum; ETC: electron transport chain; GSH: glutathione; GSTP1: glutathione S-transferase pi 1; H2O2: hydrogen peroxide; HK2: hexokinase 2; KEAP1: kelch like ECH associated protein 1; MAMs: mitochondria-associated ER membranes; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MAPK8/JNK1: mitogen-activated protein kinase 8; MAP3K5/ASK1: mitogen-activated protein kinase kinase kinase 5; MCOLN1: mucolipin 1; MMP: mitochondrial membrane potential; MTOR: mechanistic target of rapamycin kinase; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; NFKB1: nuclear factor kappa B subunit 1; NOX: NADPH oxidase; O2-: superoxide radical anion; p-Ub: phosphorylated Ub; PARK7/DJ-1: Parkinsonism associated deglycase; PE: phosphatidylethanolamine; PEX5: peroxisomal biogenesis factor 5; PINK1: PTEN induced kinase 1; PPP3CA/calcineurin: protein phosphatase 3 catalytic subunit beta; PRDX: peroxiredoxin; PRKAA1: protein kinase AMP-activated catalytic subunit alpha 1; PRKD/PKD: protein kinase D; PRKN/parkin: parkin RBR E3 ubiquitin protein ligase; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; PTEN: phosphatase and tensin homolog; ROS: reactive oxygen species; SENP3: SUMO specific peptidase 3; SIRT1: sirtuin 1; SOD1: superoxide dismutase 1; SQSTM1/p62: sequestosome 1; SUMO: small ubiquitin like modifier; TFEB: transcription factor EB; TRAF6: TNF receptor associated factor 6; TSC2: TSC complex subunit 2; TXN: thioredoxin; TXNRD1: thioredoxin reductase 1; TXNIP: thioredoxin interacting protein; Ub: ubiquitin; ULK1: unc-51 like autophagy activating kinase 1.

Keywords:  ATGs; ROS; autophagy; oxidative regulation; protein thiols

DOI:  https://doi.org/10.1080/15548627.2021.1984656