bims-mitdis Biomed News
on Mitochondrial disorders
Issue of 2023–03–12
48 papers selected by
Catalina Vasilescu, Helmholz Munich
  1. Mitochondrial molecule controls inflammation.
  2. Recessive pathogenic variants in MCAT cause combined oxidative phosphorylation deficiency.
  3. Modeling mitochondrial DNA diseases: from base editing to pluripotent stem-cell-derived organoids.
  4. MT-ATP6 mitochondrial disease identified by newborn screening reveals a distinct biochemical phenotype.
  5. A mitochondrial SCF-FBXL4 ubiquitin E3 ligase complex degrades BNIP3 and NIX to restrain mitophagy and prevent mitochondrial disease.
  6. Fractal dynamics of individual mitochondrial oscillators measure local inter-mitochondrial coupling.
  7. Fumarate induces vesicular release of mtDNA to drive innate immunity.
  8. Determinants and outcomes of mitochondrial dynamics.
  9. Parkinson's Disease, Parkinsonisms, and Mitochondria: the Role of Nuclear and Mitochondrial DNA.
  10. Mitochondrial redox adaptations enable alternative aspartate synthesis in SDH-deficient cells.
  11. A cryptic pathogenic NDUFV1 variant identified by RNA-seq in a patient with normal complex I activity in muscle and transient magnetic resonance imaging changes.
  12. The Role of Mitophagy in Skeletal Muscle Damage and Regeneration.
  13. Oxygen toxicity causes cyclic damage by destabilizing specific Fe-S cluster-containing protein complexes.
  14. Optic Nerve Injury Enhanced Mitochondrial Fission and Increased Mitochondrial Density without Altering the Uniform Mitochondrial Distribution in the Unmyelinated Axons of Retinal Ganglion Cells in a Mouse Model.
  15. Preservation of mitochondrial membrane potential is necessary for lifespan extension from dietary restriction.
  16. Mitochondrial mechanisms in Alzheimer's disease: quest for therapeutics.
  17. Dynamic interplay between RPL3- and RPL3L-containing ribosomes modulates mitochondrial activity in the mammalian heart.
  18. Isolated Mitochondrial Preparations and In organello Assays: A Powerful and Relevant Ex vivo Tool for Assessment of Brain (Patho)physiology.
  19. Pathophysiology and Management of Fatigue in Neuromuscular Diseases.
  20. Brain ethanol metabolism and mitochondria.
  21. Proliferating Astrocytes in Primary Culture Do Not Depend upon Mitochondrial Respiratory Complex I Activity or Oxidative Phosphorylation.
  22. Leber Hereditary Optic Neuropathy in a Family of Carriers of MT-ND5 m.13042G>T (A236S) Novel Variant.
  23. Autonomic instability, arrhythmia and visual impairment in a new presentation of MTFMT-related mitochondrial disease.
  24. Optogenetic rejuvenation of mitochondrial membrane potential extends C. elegans lifespan.
  25. Real-Time Visualization of Cytosolic and Mitochondrial ATP Dynamics in Response to Metabolic Stress in Cultured Cells.
  26. Transferred mitochondria accumulate reactive oxygen species, promoting proliferation.
  27. Cardiomyocyte-specific PCSK9 deficiency compromises mitochondrial bioenergetics and heart function.
  28. Germline TFAM levels regulate mitochondrial DNA copy number and mutant heteroplasmy in C. elegans.
  29. mtR_find: A Parallel Processing Tool to Identify and Annotate RNAs Derived from the Mitochondrial Genome.
  30. The autophagy-NAD axis in longevity and disease.
  31. MitoStores: a place for precursors to ride out the storm.
  32. Multi-Omics Profiling of Hypertrophic Cardiomyopathy Reveals Altered Mechanisms in Mitochondrial Dynamics and Excitation-Contraction Coupling.
  33. Monitoring Live Mitochondrial Metabolism in Real-Time Using NMR Spectroscopy.
  34. Redox proteomics combined with proximity labeling enables monitoring of localized cysteine oxidation in cells.
  35. Protein-metabolite interactomics of carbohydrate metabolism reveal regulation of lactate dehydrogenase.
  36. ATP diffusional gradients are sufficient to maintain bioenergetic homeostasis in synaptic boutons lacking mitochondria.
  37. Discovery-Based Proteomics Identify Skeletal Muscle Mitochondrial Alterations as an Early Metabolic Defect in a Mouse Model of β-Thalassemia.
  38. Primary cilia sense glutamine availability and respond via asparagine synthetase.
  39. Basal re-esterification finetunes mitochondrial fatty acid utilization.
  40. Macrophage fumarate hydratase restrains mtRNA-mediated interferon production.
  41. Mitochondria Localized microRNAs: An Unexplored miRNA Niche in Alzheimer's Disease and Aging.
  42. Mitochondria-melanocyte cellular interactions : an emerging mechanism of vitiligo pathogenesis.
  43. Mitochondrial Dysfunction in Cardiac Arrhythmias.
  44. Insights into Neurodegeneration in Parkinson's Disease from Single-Cell and Spatial Genomics.
  45. Deficits in mitochondrial TCA cycle and OXPHOS precede rod photoreceptor degeneration during chronic HIF activation.
  46. Protocol to differentiate monolayer human induced pluripotent stem cells into inflammatory responsive astrocytes.
  47. An atypically mild case of ethylmalonic encephalopathy with pathogenic ETHE1 variant.
  48. Changes in Liver Lipidomic Profile in G2019S-LRRK2 Mouse Model of Parkinson's Disease.
  1. Nature. 2023 Mar 08.
    Mitochondrial molecule controls inflammation.
    Taylor A Poor, Navdeep S Chandel.
      
    Keywords:  Cell biology; Immunology; Metabolism
    DOI:  https://doi.org/10.1038/d41586-023-00596-y
  2. Elife. 2023 Mar 07. pii: e68047. [Epub ahead of print]12
    Recessive pathogenic variants in MCAT cause combined oxidative phosphorylation deficiency.
    Bryn D Webb, Sara M Nowinski, Ashley Solmonson, Jaya Ganesh, Richard J Rodenburg, Joao Leandro, Anthony Evans, Hieu S Vu, Thomas P Naidich, Bruce D Gelb, Ralph J DeBerardinis, Jared Rutter, Sander M Houten.
      Malonyl-CoA-acyl carrier protein transacylase (MCAT) is an enzyme involved in mitochondrial fatty acid synthesis (mtFAS) and catalyzes the transfer of the malonyl moiety of malonyl-CoA to the mitochondrial acyl carrier protein (ACP). Previously, we showed that loss-of-function of mtFAS genes, including Mcat, is associated with severe loss of electron transport chain (ETC) complexes in mouse immortalized skeletal myoblasts (Nowinski et al., 2020). Here, we report a proband presenting with hypotonia, failure to thrive, nystagmus, and abnormal brain MRI findings. Using whole exome sequencing, we identified biallelic variants in MCAT. Protein levels for NDUFB8 and COXII, subunits of complex I and IV respectively, were markedly reduced in lymphoblasts and fibroblasts, as well as SDHB for complex II in fibroblasts. ETC enzyme activities were decreased in parallel. Re-expression of wild-type MCAT rescued the phenotype in patient fibroblasts. This is the first report of a patient with MCAT pathogenic variants and combined oxidative phosphorylation deficiency.
    Keywords:  MCAT; genetics; genomics; human; mitochondria; mitochondrial disease
    DOI:  https://doi.org/10.7554/eLife.68047
  3. EMBO Rep. 2023 Mar 06. e55678
    Modeling mitochondrial DNA diseases: from base editing to pluripotent stem-cell-derived organoids.
    Isabella Tolle, Valeria Tiranti, Alessandro Prigione.
      Mitochondrial DNA (mtDNA) diseases are multi-systemic disorders caused by mutations affecting a fraction or the entirety of mtDNA copies. Currently, there are no approved therapies for the majority of mtDNA diseases. Challenges associated with engineering mtDNA have in fact hindered the study of mtDNA defects. Despite these difficulties, it has been possible to develop valuable cellular and animal models of mtDNA diseases. Here, we describe recent advances in base editing of mtDNA and the generation of three-dimensional organoids from patient-derived human-induced pluripotent stem cells (iPSCs). Together with already available modeling tools, the combination of these novel technologies could allow determining the impact of specific mtDNA mutations in distinct human cell types and might help uncover how mtDNA mutation load segregates during tissue organization. iPSC-derived organoids could also represent a platform for the identification of treatment strategies and for probing the in vitro effectiveness of mtDNA gene therapies. These studies have the potential to increase our mechanistic understanding of mtDNA diseases and may open the way to highly needed and personalized therapeutic interventions.
    Keywords:  iPSCs; mitochondria; mitochondrial diseases; mitochondrial genome editing; organoids
    DOI:  https://doi.org/10.15252/embr.202255678
  4. Am J Med Genet A. 2023 Mar 08.
    MT-ATP6 mitochondrial disease identified by newborn screening reveals a distinct biochemical phenotype.
    Christina G Tise, Courtney P Verscaj, Bryce A Mendelsohn, Jeremy Woods, Chung U Lee, Gregory M Enns, Zinandré Stander, Patricia L Hall, Tina M Cowan, Kristina P Cusmano-Ozog.
      Although decreased citrulline is used as a newborn screening (NBS) marker to identify proximal urea cycle disorders (UCDs), it is also a feature of some mitochondrial diseases, including MT-ATP6 mitochondrial disease. Here we describe biochemical and clinical features of 11 children born to eight mothers from seven separate families who were identified with low citrulline by NBS (range 3-5 μM; screening cutoff >5) and ultimately diagnosed with MT-ATP6 mitochondrial disease. Follow-up testing revealed a pattern of hypocitrullinemia together with elevated propionyl-(C3) and 3-hydroxyisovaleryl-(C5-OH) acylcarnitines, and a homoplasmic pathogenic variant in MT-ATP6 in all cases. Single and multivariate analysis of NBS data from the 11 cases using Collaborative Laboratory Integrated Reports (CLIR; https://clir.mayo.edu) demonstrated citrulline <1st percentile, C3 > 50th percentile, and C5-OH >90th percentile when compared with reference data, as well as unequivocal separation from proximal UCD cases and false-positive low citrulline cases using dual scatter plots. Five of the eight mothers were symptomatic at the time of their child(ren)'s diagnosis, and all mothers and maternal grandmothers evaluated molecularly and biochemically had a homoplasmic pathogenic variant in MT-ATP6, low citrulline, elevated C3, and/or elevated C5-OH. All molecularly confirmed individuals (n = 17) with either no symptoms (n = 12), migraines (n = 1), or a neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP) phenotype (n = 3) were found to have an A or U mitochondrial haplogroup, while one child with infantile-lethal Leigh syndrome had a B haplogroup.
    Keywords:  MT-ATP6 mitochondrial disease; elevated C3; elevated C5-OH; low citrulline; newborn screening; proximal urea cycle disorders
    DOI:  https://doi.org/10.1002/ajmg.a.63159
  5. EMBO J. 2023 Mar 10. e113033
    A mitochondrial SCF-FBXL4 ubiquitin E3 ligase complex degrades BNIP3 and NIX to restrain mitophagy and prevent mitochondrial disease.
    Yu Cao, Jing Zheng, Huayun Wan, Yuqiu Sun, Song Fu, Shanshan Liu, Baiyu He, Gaihong Cai, Yang Cao, Huanwei Huang, Qi Li, Yan Ma, She Chen, Fengchao Wang, Hui Jiang.
      Mitophagy is a fundamental quality control mechanism of mitochondria. Its regulatory mechanisms and pathological implications remain poorly understood. Here, via a mitochondria-targeted genetic screen, we found that knockout (KO) of FBXL4, a mitochondrial disease gene, hyperactivates mitophagy at basal conditions. Subsequent counter screen revealed that FBXL4-KO hyperactivates mitophagy via two mitophagy receptors BNIP3 and NIX. We determined that FBXL4 functions as an integral outer-membrane protein that forms an SCF-FBXL4 ubiquitin E3 ligase complex. SCF-FBXL4 ubiquitinates BNIP3 and NIX to target them for degradation. Pathogenic FBXL4 mutations disrupt SCF-FBXL4 assembly and impair substrate degradation. Fbxl4-/- mice exhibit elevated BNIP3 and NIX proteins, hyperactive mitophagy, and perinatal lethality. Importantly, knockout of either Bnip3 or Nix rescues metabolic derangements and viability of the Fbxl4-/- mice. Together, beyond identifying SCF-FBXL4 as a novel mitochondrial ubiquitin E3 ligase restraining basal mitophagy, our results reveal hyperactivated mitophagy as a cause of mitochondrial disease and suggest therapeutic strategies.
    Keywords:  BNIP3/NIX; FBXL4; mitochondrial disease; mitophagy; ubiquitin-proteasome pathway
    DOI:  https://doi.org/10.15252/embj.2022113033
  6. Biophys J. 2023 Mar 09. pii: S0006-3495(23)00164-9. [Epub ahead of print]
    Fractal dynamics of individual mitochondrial oscillators measure local inter-mitochondrial coupling.
    Felix T Kurz, Miguel A Aon, Heinz-Peter Schlemmer, Johann Me Jende, Brian O'Rourke, Antonis A Armoundas.
      Mitochondrial inner membrane potentials in cardiomyocytes may oscillate in cycles of depolarization/repolarization when the mitochondrial network is exposed to metabolic or oxidative stress. The frequencies of such oscillations are dynamically changing while clusters of weakly coupled mitochondrial oscillators adjust to a common phase and frequency. Across the cardiac myocyte, the averaged signal of the mitochondrial population follows self-similar or fractal dynamics; however, fractal properties of individual mitochondrial oscillators have not yet been examined. We show that the largest synchronously oscillating cluster exhibits a fractal dimension,D, that is indicative of self-similar behavior with D=1.27±0.11, in contrast to the remaining network mitochondria whose fractal dimension is close to that of Brownian noise,D=1.58±0.10 . We further demonstrate that fractal behavior is correlated with local coupling mechanisms, while it is only weakly linked to measures of functional connections between mitochondria. Our findings suggest that individual mitochondrial fractal dimensions may serve as a simple measure of local mitochondrial coupling.
    Keywords:  cardiac myocyte; fractal dimension; mitochondrial oscillator; wavelets
    DOI:  https://doi.org/10.1016/j.bpj.2023.03.011
  7. Nature. 2023 Mar 08.
    Fumarate induces vesicular release of mtDNA to drive innate immunity.
    Vincent Zecchini, Vincent Paupe, Irene Herranz-Montoya, Joëlle Janssen, Inge M N Wortel, Jordan L Morris, Ashley Ferguson, Suvagata Roy Chowdury, Marc Segarra-Mondejar, Ana S H Costa, Gonçalo C Pereira, Laura Tronci, Timothy Young, Efterpi Nikitopoulou, Ming Yang, Dóra Bihary, Federico Caicci, Shun Nagashima, Alyson Speed, Kalliopi Bokea, Zara Baig, Shamith Samarajiwa, Maxine Tran, Thomas Mitchell, Mark Johnson, Julien Prudent, Christian Frezza.
      Mutations in fumarate hydratase (FH) cause hereditary leiomyomatosis and renal cell carcinoma1. Loss of FH in the kidney elicits several oncogenic signalling cascades through the accumulation of the oncometabolite fumarate2. However, although the long-term consequences of FH loss have been described, the acute response has not so far been investigated. Here we generated an inducible mouse model to study the chronology of FH loss in the kidney. We show that loss of FH leads to early alterations of mitochondrial morphology and the release of mitochondrial DNA (mtDNA) into the cytosol, where it triggers the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-TANK-binding kinase 1 (TBK1) pathway and stimulates an inflammatory response that is also partially dependent on retinoic-acid-inducible gene I (RIG-I). Mechanistically, we show that this phenotype is mediated by fumarate and occurs selectively through mitochondrial-derived vesicles in a manner that depends on sorting nexin 9 (SNX9). These results reveal that increased levels of intracellular fumarate induce a remodelling of the mitochondrial network and the generation of mitochondrial-derived vesicles, which allows the release of mtDNAin the cytosol and subsequent activation of the innate immune response.
    DOI:  https://doi.org/10.1038/s41586-023-05770-w
  8. Mol Cell. 2023 Feb 28. pii: S1097-2765(23)00115-6. [Epub ahead of print]
    Determinants and outcomes of mitochondrial dynamics.
    Rubén Quintana-Cabrera, Luca Scorrano.
      Mitochondria are not only central organelles in metabolism and energy conversion but are also platforms for cellular signaling cascades. Classically, the shape and ultrastructure of mitochondria were depicted as static. The discovery of morphological transitions during cell death and of conserved genes controlling mitochondrial fusion and fission contributed to establishing the concept that mitochondrial morphology and ultrastructure are dynamically regulated by mitochondria-shaping proteins. These finely tuned, dynamic changes in mitochondrial shape can in turn control mitochondrial function, and their alterations in human diseases suggest that this space can be explored for drug discovery. Here, we review the basic tenets and molecular mechanisms of mitochondrial morphology and ultrastructure, describing how they can coordinately define mitochondrial function.
    Keywords:  cristae; cristae remodeling; fusion fission; mitochondria
    DOI:  https://doi.org/10.1016/j.molcel.2023.02.012
  9. Curr Neurol Neurosci Rep. 2023 Mar 07.
    Parkinson's Disease, Parkinsonisms, and Mitochondria: the Role of Nuclear and Mitochondrial DNA.
    A Legati, D Ghezzi.
       PURPOSE OF REVIEW: Overwhelming evidence indicates that mitochondrial dysfunction is a central factor in Parkinson's disease (PD) pathophysiology. This paper aims to review the latest literature published, focusing on genetic defects and expression alterations affecting mitochondria-associated genes, in support of their key role in PD pathogenesis.
    RECENT FINDINGS: Thanks to the use of new omics approaches, a growing number of studies are discovering alterations affecting genes with mitochondrial functions in patients with PD and parkinsonisms. These genetic alterations include pathogenic single-nucleotide variants, polymorphisms acting as risk factors, and transcriptome modifications, affecting both nuclear and mitochondrial genes. We will focus on alterations of mitochondria-associated genes described by studies conducted on patients or on animal/cellular models of PD or parkinsonisms. We will comment how these findings can be taken into consideration for improving the diagnostic procedures or for deepening our knowledge on the role of mitochondrial dysfunctions in PD.
    Keywords:  Mitochondria; Mitochondrial DNA; Nuclear DNA; Omics; Parkinsonism; Parkinson’s disease
    DOI:  https://doi.org/10.1007/s11910-023-01260-8
  10. Elife. 2023 Mar 08. pii: e78654. [Epub ahead of print]12
    Mitochondrial redox adaptations enable alternative aspartate synthesis in SDH-deficient cells.
    Madeleine L Hart, Evan Quon, Anna-Lena B G Vigil, Ian A Engstrom, Oliver J Newsom, Kristian Davidsen, Pia Hoellerbauer, Samantha M Carlisle, Lucas B Sullivan.
      The oxidative tricarboxylic acid (TCA) cycle is a central mitochondrial pathway integrating catabolic conversions of NAD+ to NADH and anabolic production of aspartate, a key amino acid for cell proliferation. Several TCA cycle components are implicated in tumorigenesis, including loss of function mutations in subunits of succinate dehydrogenase (SDH), also known as complex II of the electron transport chain (ETC), but mechanistic understanding of how proliferating cells tolerate the metabolic defects of SDH loss is still lacking. Here, we identify that SDH supports human cell proliferation through aspartate synthesis but, unlike other ETC impairments, the effects of SDH inhibition are not ameliorated by electron acceptor supplementation. Interestingly, we find aspartate production and cell proliferation are restored to SDH-impaired cells by concomitant inhibition of ETC complex I (CI). We determine that the benefits of CI inhibition in this context depend on decreasing mitochondrial NAD+/NADH, which drives SDH-independent aspartate production through pyruvate carboxylation and reductive carboxylation of glutamine. We also find that genetic loss or restoration of SDH selects for cells with concordant CI activity, establishing distinct modalities of mitochondrial metabolism for maintaining aspartate synthesis. These data therefore identify a metabolically beneficial mechanism for CI loss in proliferating cells and reveal how compartmentalized redox changes can impact cellular fitness.
    Keywords:  biochemistry; cancer biology; chemical biology; human
    DOI:  https://doi.org/10.7554/eLife.78654
  11. Am J Med Genet A. 2023 Mar 09.
    A cryptic pathogenic NDUFV1 variant identified by RNA-seq in a patient with normal complex I activity in muscle and transient magnetic resonance imaging changes.
    Sharmila Kiss, John Christodoulou, David R Thorburn, Jeremy L Freeman, Andrew J Kornberg, Simone Mandelstam, Alison G Compton, Beryl Cummings, Lynn Pais, Joy Yaplito-Lee, Susan M White.
      Mitochondrial respiratory chain disorders (MRC) are amongst the most common group of inborn errors of metabolism. MRC, of which complex I deficiency accounts for approximately a quarter, are very diverse, causing a wide range of clinical problems and can be difficult to diagnose. We report an illustrative MRC case whose diagnosis was elusive. Clinical signs included failure to thrive caused by recurrent vomiting, hypotonia and progressive loss of motor milestones. Initial brain imaging suggested Leigh syndrome but without expected diffusion restriction. Muscle respiratory chain enzymology was unremarkable. Whole-genome sequencing identified a maternally inherited NDUFV1 missense variant [NM_007103.4 (NDUFV1):c.1157G > A; p.(Arg386His)] and a paternally inherited synonymous variant [NM_007103.4 (NDUFV1):c.1080G > A; (p.Ser360=)]. RNA sequencing demonstrated aberrant splicing. This case emphasizes the diagnostic odyssey of a patient in whom a confirmed diagnosis was elusive because of atypical features and normal muscle respiratory chain enzyme (RCE) activities, along with a synonymous variant, which are often filtered out from genomic analyses. It also illustrates the following points: (1) complete resolution of magnetic resonance imaging changes may be part of the picture in mitochondrial disease; (2) analysis for synonymous variants is important for undiagnosed patients; and (3) RNA-seq is a powerful tool to demonstrate pathogenicity of putative splicing variants.
    Keywords:  NDUFV1; RNA; complex I deficiency; mitochondrial
    DOI:  https://doi.org/10.1002/ajmg.a.63170
  12. Cells. 2023 Feb 24. pii: 716. [Epub ahead of print]12(5):
    The Role of Mitophagy in Skeletal Muscle Damage and Regeneration.
    Eirini Chatzinikita, Maria Maridaki, Konstantinos Palikaras, Michael Koutsilieris, Anastassios Philippou.
      Mitochondria are cellular organelles that play an essential role in generating the chemical energy needed for the biochemical reactions in cells. Mitochondrial biogenesis, i.e., de novo mitochondria formation, results in enhanced cellular respiration, metabolic processes, and ATP generation, while autophagic clearance of mitochondria (mitophagy) is required to remove damaged or useless mitochondria. The balance between the opposing processes of mitochondrial biogenesis and mitophagy is highly regulated and crucial for the maintenance of the number and function of mitochondria as well as for the cellular homeostasis and adaptations to metabolic demands and extracellular stimuli. In skeletal muscle, mitochondria are essential for maintaining energy homeostasis, and the mitochondrial network exhibits complex behaviors and undergoes dynamic remodeling in response to various conditions and pathologies characterized by changes in muscle cell structure and metabolism, such as exercise, muscle damage, and myopathies. In particular, the involvement of mitochondrial remodeling in mediating skeletal muscle regeneration following damage has received increased attention, as modifications in mitophagy-related signals arise from exercise, while variations in mitochondrial restructuring pathways can lead to partial regeneration and impaired muscle function. Muscle regeneration (through myogenesis) following exercise-induced damage is characterized by a highly regulated, rapid turnover of poor-functioning mitochondria, permitting the synthesis of better-functioning mitochondria to occur. Nevertheless, essential aspects of mitochondrial remodeling during muscle regeneration remain poorly understood and warrant further characterization. In this review, we focus on the critical role of mitophagy for proper muscle cell regeneration following damage, highlighting the molecular mechanisms of the mitophagy-associated mitochondrial dynamics and network reformation.
    Keywords:  exercise; mitochondrial biogenesis; mitochondrial network; mitophagy; muscle damage; myogenesis; regeneration
    DOI:  https://doi.org/10.3390/cells12050716
  13. Mol Cell. 2023 Mar 06. pii: S1097-2765(23)00116-8. [Epub ahead of print]
    Oxygen toxicity causes cyclic damage by destabilizing specific Fe-S cluster-containing protein complexes.
    Alan H Baik, Augustinus G Haribowo, Xuewen Chen, Bruno B Queliconi, Alec M Barrios, Ankur Garg, Mazharul Maishan, Alexandre R Campos, Michael A Matthay, Isha H Jain.
      Oxygen is toxic across all three domains of life. Yet, the underlying molecular mechanisms remain largely unknown. Here, we systematically investigate the major cellular pathways affected by excess molecular oxygen. We find that hyperoxia destabilizes a specific subset of Fe-S cluster (ISC)-containing proteins, resulting in impaired diphthamide synthesis, purine metabolism, nucleotide excision repair, and electron transport chain (ETC) function. Our findings translate to primary human lung cells and a mouse model of pulmonary oxygen toxicity. We demonstrate that the ETC is the most vulnerable to damage, resulting in decreased mitochondrial oxygen consumption. This leads to further tissue hyperoxia and cyclic damage of the additional ISC-containing pathways. In support of this model, primary ETC dysfunction in the Ndufs4 KO mouse model causes lung tissue hyperoxia and dramatically increases sensitivity to hyperoxia-mediated ISC damage. This work has important implications for hyperoxia pathologies, including bronchopulmonary dysplasia, ischemia-reperfusion injury, aging, and mitochondrial disorders.
    Keywords:  DNA damage; Fe-S clusters; hyperoxia; lung injury; mitochondria; oxygen; purine synthesis; redox; translation fidelity
    DOI:  https://doi.org/10.1016/j.molcel.2023.02.013
  14. Int J Mol Sci. 2023 Feb 22. pii: 4356. [Epub ahead of print]24(5):
    Optic Nerve Injury Enhanced Mitochondrial Fission and Increased Mitochondrial Density without Altering the Uniform Mitochondrial Distribution in the Unmyelinated Axons of Retinal Ganglion Cells in a Mouse Model.
    Takahiro Tsuji, Tomoya Murase, Yoshiyuki Konishi, Masaru Inatani.
      Glaucomatous optic neuropathy (GON), a major cause of blindness, is characterized by the loss of retinal ganglion cells (RGCs) and the degeneration of their axons. Mitochondria are deeply involved in maintaining the health of RGCs and their axons. Therefore, lots of attempts have been made to develop diagnostic tools and therapies targeting mitochondria. Recently, we reported that mitochondria are uniformly distributed in the unmyelinated axons of RGCs, possibly owing to the ATP gradient. Thus, using transgenic mice expressing yellow fluorescent protein targeting mitochondria exclusively in RGCs within the retina, we assessed the alteration of mitochondrial distributions induced by optic nerve crush (ONC) via in vitro flat-mount retinal sections and in vivo fundus images captured with a confocal scanning ophthalmoscope. We observed that the mitochondrial distribution in the unmyelinated axons of survived RGCs after ONC remained uniform, although their density increased. Furthermore, via in vitro analysis, we discovered that the mitochondrial size is attenuated following ONC. These results suggest that ONC induces mitochondrial fission without disrupting the uniform mitochondrial distribution, possibly preventing axonal degeneration and apoptosis. The in vivo visualization system of axonal mitochondria in RGCs may be applicable in the detection of the progression of GON in animal studies and potentially in humans.
    Keywords:  Thy1-mito-YFP mice; confocal scanning ophthalmoscope; distribution; glaucoma; mitochondria; optic nerve crush; optic neuropathy
    DOI:  https://doi.org/10.3390/ijms24054356
  15. Geroscience. 2023 Mar 06.
    Preservation of mitochondrial membrane potential is necessary for lifespan extension from dietary restriction.
    Brandon J Berry, Evan Mjelde, Fatima Carreno, Kathryn Gilham, Emily J Hanson, Emily Na, Matt Kaeberlein.
      Dietary restriction (DR) increases lifespan in many organisms, but its underlying mechanisms are not fully understood. Mitochondria play a central role in metabolic regulation and are known to undergo changes in structure and function in response to DR. Mitochondrial membrane potential (Δψm) is the driving force for ATP production and mitochondrial outputs that integrate many cellular signals. One such signal regulated by Δψm is nutrient-status sensing. Here, we tested the hypothesis that DR promotes longevity through preserved Δψm during adulthood. Using the nematode Caenorhabditis elegans, we find that Δψm declines with age relatively early in the lifespan, and this decline is attenuated by DR. Pharmacologic depletion of Δψm blocked the longevity and health benefits of DR. Genetic perturbation of Δψm and mitochondrial ATP availability similarly prevented lifespan extension from DR. Taken together, this study provides further evidence that appropriate regulation of Δψm is a critical factor for health and longevity in response to DR.
    Keywords:  Aging; Bioenergetics; Calorie restriction; Fasting; Metabolism; Mitochondrial uncoupling
    DOI:  https://doi.org/10.1007/s11357-023-00766-w
  16. Drug Discov Today. 2023 Mar 03. pii: S1359-6446(23)00063-6. [Epub ahead of print] 103547
    Mitochondrial mechanisms in Alzheimer's disease: quest for therapeutics.
    Komal Kalani, Poonam Chaturvedi, Pankaj Chaturvedi, Vinod Kumar Verma, Nand Lal, Sudhir K Awasthi, Anuradha Kalani.
      Mitochondrial function is essential for maintaining neuronal integrity, because neurons have a high energy demand. Neurodegenerative diseases, such as Alzheimer's disease (AD), are exacerbated by mitochondrial dysfunction. Mitochondrial autophagy (mitophagy) attenuates neurodegenerative diseases by eradicating dysfunctional mitochondria. In neurodegenerative disorders, there is disruption of the mitophagy process. High levels of iron also interfere with the mitophagy process and the mtDNA released after mitophagy is proinflammatory and triggers the cGAS-STING pathway that aids AD pathology. In this review, we critically discuss the factors that affect mitochondrial impairment and different mitophagy processes in AD. Furthermore, we discuss the molecules used in mouse studies as well as clinical trials that could result in potential therapeutics in the future. Teaser: This review reports the novel therapeutic molecules that are underway in clinical trials for neurodegenerative diseases like Alzheimer's disease, demonstrating how mitochondria become dysfunctional and how they can be rescued.
    Keywords:  Alzheimer’s disease; bioenergetics; exosomes; mitochondria; mitophagy; neurodegenerative disorders
    DOI:  https://doi.org/10.1016/j.drudis.2023.103547
  17. Nucleic Acids Res. 2023 Mar 07. pii: gkad121. [Epub ahead of print]
    Dynamic interplay between RPL3- and RPL3L-containing ribosomes modulates mitochondrial activity in the mammalian heart.
    Ivan Milenkovic, Helaine Graziele Santos Vieira, Morghan C Lucas, Jorge Ruiz-Orera, Giannino Patone, Scott Kesteven, Jianxin Wu, Michael Feneley, Guadalupe Espadas, Eduard Sabidó, Norbert Hübner, Sebastiaan van Heesch, Mirko Völkers, Eva Maria Novoa.
      The existence of naturally occurring ribosome heterogeneity is now a well-acknowledged phenomenon. However, whether this heterogeneity leads to functionally diverse 'specialized ribosomes' is still a controversial topic. Here, we explore the biological function of RPL3L (uL3L), a ribosomal protein (RP) paralogue of RPL3 (uL3) that is exclusively expressed in skeletal muscle and heart tissues, by generating a viable homozygous Rpl3l knockout mouse strain. We identify a rescue mechanism in which, upon RPL3L depletion, RPL3 becomes up-regulated, yielding RPL3-containing ribosomes instead of RPL3L-containing ribosomes that are typically found in cardiomyocytes. Using both ribosome profiling (Ribo-seq) and a novel orthogonal approach consisting of ribosome pulldown coupled to nanopore sequencing (Nano-TRAP), we find that RPL3L modulates neither translational efficiency nor ribosome affinity towards a specific subset of transcripts. In contrast, we show that depletion of RPL3L leads to increased ribosome-mitochondria interactions in cardiomyocytes, which is accompanied by a significant increase in ATP levels, potentially as a result of fine-tuning of mitochondrial activity. Our results demonstrate that the existence of tissue-specific RP paralogues does not necessarily lead to enhanced translation of specific transcripts or modulation of translational output. Instead, we reveal a complex cellular scenario in which RPL3L modulates the expression of RPL3, which in turn affects ribosomal subcellular localization and, ultimately, mitochondrial activity.
    DOI:  https://doi.org/10.1093/nar/gkad121
  18. Curr Neuropharmacol. 2023 Mar 03.
    Isolated Mitochondrial Preparations and In organello Assays: A Powerful and Relevant Ex vivo Tool for Assessment of Brain (Patho)physiology.
    Faraz Ahmad, Siva Ramamorthy, Mohammed Y Areeshi, Ghulam Md Ashraf, Shafiul Haque.
      Mitochondria regulate multiple aspects of neuronal development, physiology, plasticity, and pathology through their regulatory roles in bioenergetic, calcium, redox, and cell survival/death signalling. While several reviews have addressed these different aspects, a comprehensive discussion focussing on the relevance of isolated brain mitochondria and their utilities in neuroscience research has been lacking. This is relevant because the employment of isolated mitochondria rather than their in situ functional evaluation, offers definitive evidence of organelle-specificity, negating the interference from extra mitochondrial cellular factors/signals. This mini-review was designed primarily to explore the commonly employed in organello analytical assays for the assessment of mitochondrial physiology and its dysfunction, with a particular focus on neuroscience research. The authors briefly discuss the methodologies for biochemical isolation of mitochondria, their quality assessment, and cryopres- ervation. Further, the review attempts to accumulate the key biochemical protocols for in organello assessment of a multitude of mitochondrial functions critical for neurophysiology, including assays for bioenergetic activity, calcium and redox homeostasis, and mitochondrial protein translation. The purpose of this review is not to examine each and every method or study related to the functional assessment of isolated brain mitochondria, but rather to assemble the commonly used protocols of in organello mitochondrial research in a single publication. The hope is that this review will provide a suitable platform aiding neuroscientists to choose and apply the required protocols and tools to address their particular mechanistic, diagnostic, or therapeutic question dealing within the confines of the research area of mitochondrial patho-physiology in the neuronal perspective.
    Keywords:  Intrasynaptic mitochondria; Trolox equivalent antioxidant capacity (TEAC).; calcium capacitance; density gradient centrifugation; electron transport chain (ETC); glutathione (GSH); mitochondrial membrane potential (MMP); reactive oxygen species (ROS)
    DOI:  https://doi.org/10.2174/1570159X21666230303123555
  19. Int J Mol Sci. 2023 Mar 05. pii: 5005. [Epub ahead of print]24(5):
    Pathophysiology and Management of Fatigue in Neuromuscular Diseases.
    Francesca Torri, Piervito Lopriore, Vincenzo Montano, Gabriele Siciliano, Michelangelo Mancuso, Giulia Ricci.
      Fatigue is a major determinant of quality of life and motor function in patients affected by several neuromuscular diseases, each of them characterized by a peculiar physiopathology and the involvement of numerous interplaying factors. This narrative review aims to provide an overview on the pathophysiology of fatigue at a biochemical and molecular level with regard to muscular dystrophies, metabolic myopathies, and primary mitochondrial disorders with a focus on mitochondrial myopathies and spinal muscular atrophy, which, although fulfilling the definition of rare diseases, as a group represent a representative ensemble of neuromuscular disorders that the neurologist may encounter in clinical practice. The current use of clinical and instrumental tools for fatigue assessment, and their significance, is discussed. A summary of therapeutic approaches to address fatigue, encompassing pharmacological treatment and physical exercise, is also overviewed.
    Keywords:  fatigue; metabolic myopathies; mitochondrial diseases; muscular dystrophies; neuromuscular disorders; spinal muscular atrophy
    DOI:  https://doi.org/10.3390/ijms24055005
  20. Curr Top Biochem Res. 2022 ;23 1-13
    Brain ethanol metabolism and mitochondria.
    Jaylyn Waddell, Mary C McKenna, Tibor Kristian.
      Alcohol abuse and dependence in humans causes an extreme shift in metabolism for which the human brain is not evolutionarily prepared. Oxidation of ethanol and acetaldehyde are not regulated, making ethanol a dominating metabolic substrate that prevents the activity of enzymes from oxidizing their usual endogenous substrates. The enzymes required to oxidize ethanol across the variety of affected tissues all produce acetaldehyde which is then converted to acetate by aldehyde dehydrogenases (ALDHs). ALDHs are NAD+-dependent enzymes, and mitochondrial ALDH2 is likely the primary contributor to ethanol-derived acetaldehyde clearance in cells. Metabolism of alcohol has several adverse effects on mitochondria including increased free radical levels, hyperacetylation of mitochondrial proteins, and excessive mitochondrial fragmentation. This review discusses the role of astrocytic and neuronal mitochondria in ethanol metabolism that contributes to the acute and chronic changes in mitochondrial function and morphology, that might promote tolerance, dependence and withdrawal. We also propose potential modes of therapeutic intervention to reduce the toxicity of chronic alcohol consumption.
    Keywords:  brain; ethanol; mitochondria
  21. Cells. 2023 Feb 21. pii: 683. [Epub ahead of print]12(5):
    Proliferating Astrocytes in Primary Culture Do Not Depend upon Mitochondrial Respiratory Complex I Activity or Oxidative Phosphorylation.
    Ellen A Silva, Ana P Dalla Costa, Juliana S Ruas, Edilene S Siqueira-Santos, Annelise Francisco, Roger F Castilho.
      Understanding the role of astrocytes in the development of the nervous system and neurodegenerative disorders implies a necessary knowledge of the oxidative metabolism of proliferating astrocytes. The electron flux through mitochondrial respiratory complexes and oxidative phosphorylation may impact the growth and viability of these astrocytes. Here, we aimed at assessing to which extent mitochondrial oxidative metabolism is required for astrocyte survival and proliferation. Primary astrocytes from the neonatal mouse cortex were cultured in a physiologically relevant medium with the addition of piericidin A or oligomycin at concentrations that fully inhibit complex I-linked respiration and ATP synthase, respectively. The presence of these mitochondrial inhibitors for up to 6 days in a culture medium elicited only minor effects on astrocyte growth. Moreover, neither the morphology nor the proportion of glial fibrillary acidic protein-positive astrocytes in culture was affected by piericidin A or oligomycin. Metabolic characterization of the astrocytes showed a relevant glycolytic metabolism under basal conditions, despite functional oxidative phosphorylation and large spare respiratory capacity. Our data suggest that astrocytes in primary culture can sustainably proliferate when their energy metabolism relies only on aerobic glycolysis since their growth and survival do not require electron flux through respiratory complex I or oxidative phosphorylation.
    Keywords:  OXPHOS; astrocytes; bioenergetic; mitochondria; oligomycin; piericidin A
    DOI:  https://doi.org/10.3390/cells12050683
  22. J Neuroophthalmol. 2023 Mar 10.
    Leber Hereditary Optic Neuropathy in a Family of Carriers of MT-ND5 m.13042G>T (A236S) Novel Variant.
    Sanja Petrović Pajić, Maja Suštar Habjan, Jelka Brecelj, Ana Fakin, Marija Volk, Aleš Maver, Gregor Jezernik, Borut Peterlin, Damjan Glavač, Marko Hawlina, Martina Jarc-Vidmar.
       BACKGROUND: A Slovenian three-generation family with 3 individuals with bilateral optic neuropathy and 2 unaffected relatives with a novel homoplasmic missense variant m.13042G > T (A236S) in the ND5 gene is described. A detailed phenotype at initial diagnosis and a follow-up of bilateral optic neuropathy progression is presented for 2 affected individuals.
    METHODS: A detailed phenotype analysis with clinical examination in the early and chronic phase with electrophysiology and OCT segmentation is presented. Genotype analysis with full mitochondrial genome sequencing was performed.
    RESULTS: Two affected male individuals (maternal cousins) had a profound visual loss at an early age (11 and 20 years) with no recovery. The maternal grandmother exhibited bilateral optic atrophy with a history of visual loss at the age 58 years. The visual loss of both affected male individuals was characterized by centrocecal scotoma, abnormal color vision, abnormal PERG N95, and VEP. Later with disease progression, retinal nerve fiber layer thinning was observed on OCT. We observed no other extraocular clinical features. Mitochondrial sequencing identified a homoplasmic novel variant m.13042G > T (A236S) in the MT-ND5 gene, belonging to a haplogroup K1a.
    CONCLUSION: Novel homoplasmic variant m.13042G > T (A236S) in the ND5 gene in our family was associated with Leber hereditary optic neuropathy-like phenotype. However, predicting the pathogenicity of a novel ultra-rare missense variant in the mitochondrial ND5 gene is challenging. Genetic counseling should consider genotypic and phenotypic heterogeneity, incomplete penetrance, haplogroup type, and tissue-specific thresholds.
    DOI:  https://doi.org/10.1097/WNO.0000000000001820
  23. JIMD Rep. 2023 Mar;64(2): 150-155
    Autonomic instability, arrhythmia and visual impairment in a new presentation of MTFMT-related mitochondrial disease.
    Caoimhe Howard, Arundhati Dev-Borman, John Stokes, Declan O'Rourke, Ciara Gillespie, Eilish Twomey, Ina Knerr, Ritma Boruah.
      Mitochondrial methionyl-tRNA formyltransferase (MTFMT) is required for the initiation of translation in mitochondria. Pathogenic variants in MTFMT have been described in association with clinical presentations with Leigh syndrome, as well with as multisystem involvement (particularly cardiac and ocular involvement). There is a spectrum of severity, but many reported presentations have been milder with a better prognosis than other pathogenic variants associated with Leigh syndrome. We describe the case of a 9-year-old boy homozygous for a pathogenic MTFMT variant (c.626C > T/p.Ser209Leu) who presented with hypertensive crisis on a background of hyperphagia and visual impairment. His clinical course was complicated by supraventricular tachycardia and severe autonomic instability, requiring intensive care unit admission. He also developed seizures, neurogenic bladder and bowel and had a markedly abnormal eye examination with bilateral optic atrophy. Magnetic resonance image brain showed abnormal high T2/fluid-attenuated inversion recovery signal within the dorsal brainstem and in the right globus pallidus with some reduced diffusivity. Despite recovery from the acute neurological and cardiac manifestations, he has ongoing deficits in his gross motor skills and continues to have hyperphagia with rapid weight gain (approx. 20 kg in 2 years). Ophthalmic findings are persistent. This case expands the phenotype associated with MTFMT disease.
    Keywords:  Leigh syndrome; MTFMT; autonomic instability; optic atrophy
    DOI:  https://doi.org/10.1002/jmd2.12355
  24. Nat Aging. 2023 Feb;3(2): 157-161
    Optogenetic rejuvenation of mitochondrial membrane potential extends C. elegans lifespan.
    Brandon J Berry, Anežka Vodičková, Annika Müller-Eigner, Chen Meng, Christina Ludwig, Matt Kaeberlein, Shahaf Peleg, Andrew P Wojtovich.
      Mitochondrial dysfunction plays a central role in aging but the exact biological causes are still being determined. Here, we show that optogenetically increasing mitochondrial membrane potential during adulthood using a light-activated proton pump improves age-associated phenotypes and extends lifespan in C. elegans. Our findings provide direct causal evidence that rescuing the age-related decline in mitochondrial membrane potential is sufficient to slow the rate of aging and extend healthspan and lifespan.
    DOI:  https://doi.org/10.1038/s43587-022-00340-7
  25. Cells. 2023 Feb 22. pii: 695. [Epub ahead of print]12(5):
    Real-Time Visualization of Cytosolic and Mitochondrial ATP Dynamics in Response to Metabolic Stress in Cultured Cells.
    Donnell White, Lothar Lauterboeck, Parnia Mobasheran, Tetsuya Kitaguchi, Antoine H Chaanine, Qinglin Yang.
      Adenosine 5' triphosphate (ATP) is the energy currency of life, which is produced in mitochondria (~90%) and cytosol (less than 10%). Real-time effects of metabolic changes on cellular ATP dynamics remain indeterminate. Here we report the design and validation of a genetically encoded fluorescent ATP indicator that allows for real-time, simultaneous visualization of cytosolic and mitochondrial ATP in cultured cells. This dual-ATP indicator, called smacATPi (simultaneous mitochondrial and cytosolic ATP indicator), combines previously described individual cytosolic and mitochondrial ATP indicators. The use of smacATPi can help answer biological questions regarding ATP contents and dynamics in living cells. As expected, 2-deoxyglucose (2-DG, a glycolytic inhibitor) led to substantially decreased cytosolic ATP, and oligomycin (a complex V inhibitor) markedly decreased mitochondrial ATP in cultured HEK293T cells transfected with smacATPi. With the use of smacATPi, we can also observe that 2-DG treatment modestly attenuates mitochondrial ATP and oligomycin reduces cytosolic ATP, indicating the subsequent changes of compartmental ATP. To evaluate the role of ATP/ADP carrier (AAC) in ATP trafficking, we treated HEK293T cells with an AAC inhibitor, Atractyloside (ATR). ATR treatment attenuated cytosolic and mitochondrial ATP in normoxia, suggesting AAC inhibition reduces ADP import from the cytosol to mitochondria and ATP export from mitochondria to cytosol. In HEK293T cells subjected to hypoxia, ATR treatment increased mitochondrial ATP along with decreased cytosolic ATP, implicating that ACC inhibition during hypoxia sustains mitochondrial ATP but may not inhibit the reversed ATP import from the cytosol. Furthermore, both mitochondrial and cytosolic signals decrease when ATR is given in conjunction with 2-DG in hypoxia. Thus, real-time visualization of spatiotemporal ATP dynamics using smacATPi provides novel insights into how cytosolic and mitochondrial ATP signals respond to metabolic changes, providing a better understanding of cellular metabolism in health and disease.
    Keywords:  ATP; biosensor; fluorescence; metabolism; mitochondria
    DOI:  https://doi.org/10.3390/cells12050695
  26. Elife. 2023 Mar 06. pii: e85494. [Epub ahead of print]12
    Transferred mitochondria accumulate reactive oxygen species, promoting proliferation.
    Chelsea U Kidwell, Joseph R Casalini, Soorya Pradeep, Sandra D Scherer, Daniel Greiner, Defne Bayik, Dionysios C Watson, Gregory S Olson, Justin D Lathia, Jarrod S Johnson, Jared Rutter, Alana L Welm, Thomas A Zangle, Minna Roh-Johnson.
      Recent studies reveal that lateral mitochondrial transfer, the movement of mitochondria from one cell to another, can affect cellular and tissue homeostasis1,2. Most of what we know about mitochondrial transfer stems from bulk cell studies and have led to the paradigm that functional transferred mitochondria restore bioenergetics and revitalize cellular functions to recipient cells with damaged or non-functional mitochondrial networks3. However, we show that mitochondrial transfer also occurs between cells with functioning endogenous mitochondrial networks, but the mechanisms underlying how transferred mitochondria can promote such sustained behavioral reprogramming remain unclear. We report that unexpectedly, transferred macrophage mitochondria are dysfunctional and accumulate reactive oxygen species in recipient cancer cells. We further discovered that reactive oxygen species accumulation activates ERK signaling, promoting cancer cell proliferation. Pro-tumorigenic macrophages exhibit fragmented mitochondrial networks, leading to higher rates of mitochondrial transfer to cancer cells. Finally, we observe that macrophage mitochondrial transfer promotes tumor cell proliferation in vivo. Collectively these results indicate that transferred macrophage mitochondria activate downstream signaling pathways in a ROS-dependent manner in cancer cells, and provide a model of how sustained behavioral reprogramming can be mediated by a relatively small amount of transferred mitochondria in vitro and in vivo.
    Keywords:  cancer biology; cell biology; human; mouse
    DOI:  https://doi.org/10.7554/eLife.85494
  27. Cardiovasc Res. 2023 Mar 06. pii: cvad041. [Epub ahead of print]
    Cardiomyocyte-specific PCSK9 deficiency compromises mitochondrial bioenergetics and heart function.
    Marion Laudette, Malin Lindbom, Muhammad Arif, Mathieu Cinato, Mario Ruiz, Stephen Doran, Azra Miljanovic, Mikael Rutberg, Linda Andersson, Martina Klevstig, Marcus Henricsson, Per-Olof Bergh, Entela Bollano, Nay Aung, J Gustav Smith, Marc Pilon, Tuulia Hyötyläinen, Matej Orešič, Rosie Perkins, Adil Mardinoglu, Malin C Levin, Jan Borén.
       AIMS: PCSK9, which is expressed mainly in the liver and at low levels in the heart, regulates cholesterol levels by directing low-density lipoprotein receptors to degradation. Studies to determine the role of PCSK9 in the heart are complicated by the close link between cardiac function and systemic lipid metabolism. Here, we sought to elucidate the function of PCSK9 specifically in the heart by generating and analysing mice with cardiomyocyte-specific Pcsk9 deficiency (CM-Pcsk9-/- mice) and by silencing Pcsk9 acutely in a cell culture model of adult cardiomyocyte-like cells.
    METHODS AND RESULTS: Mice with cardiomyocyte-specific deletion of Pcsk9 had reduced contractile capacity, impaired cardiac function and left ventricular dilatation at 28 weeks of age and died prematurely. Transcriptomic analyses revealed alterations of signalling pathways linked to cardiomyopathy and energy metabolism in hearts from CM-Pcsk9-/- mice versus wildtype littermates. In agreement, levels of genes and proteins involved in mitochondrial metabolism were reduced in CM-Pcsk9-/- hearts. By using a Seahorse flux analyser, we showed that mitochondrial but not glycolytic function was impaired in cardiomyocytes from CM-Pcsk9-/- mice. We further showed that assembly and activity of electron transport chain (ETC) complexes were altered in isolated mitochondria from CM-Pcsk9-/- mice. Circulating lipid levels were unchanged in CM-Pcsk9-/- mice, but the lipid composition of mitochondrial membranes was altered. In addition, cardiomyocytes from CM-Pcsk9-/- mice had an increased number of mitochondria-ER contacts and alterations in the morphology of cristae, the physical location of the ETC complexes. We also showed that acute Pcsk9 silencing in adult cardiomyocyte-like cells reduced the activity of ETC complexes and impaired mitochondrial metabolism.
    CONCLUSION: PCSK9, despite its low expression in cardiomyocytes, contributes to cardiac metabolic function, and PCSK9 deficiency in cardiomyocytes is linked to cardiomyopathy, impaired heart function, and compromised energy production.
    TRANSLATIONAL PERSPECTIVE: PCSK9 is mainly present in the circulation where it regulates plasma cholesterol levels. Here we show that PCSK9 mediates intracellular functions that differ from its extracellular functions. We further show that intracellular PCSK9 in cardiomyocytes, despite low expression levels, is important for maintaining physiological cardiac metabolism and function.
    Keywords:  Pro-protein convertase subtilisin-kexin type 9 (PCSK9); cardiac dysfunction; cardiomyocyte; metabolic inflexibility; mitochondria
    DOI:  https://doi.org/10.1093/cvr/cvad041
  28. MicroPubl Biol. 2023 ;2023
    Germline TFAM levels regulate mitochondrial DNA copy number and mutant heteroplasmy in C. elegans.
    Aaron Z A Schwartz, Jeremy Nance.
      The mitochondrial genome (mtDNA) is packaged into discrete protein-DNA complexes called nucleoids. mtDNA packaging factor TFAM (mitochondrial transcription factor-A) promotes nucleoid compaction and is required for mtDNA replication. Here, we investigate how changing TFAM levels affects mtDNA in the Caenorhabditis elegans germ line. We show that increasing germline TFAM activity boosts mtDNA number and significantly increases the relative proportion of a selfish mtDNA mutant, uaDf5 . We conclude that TFAM levels must be tightly controlled to ensure appropriate mtDNA composition in the germ line.
    DOI:  https://doi.org/10.17912/micropub.biology.000727
  29. Int J Mol Sci. 2023 Feb 22. pii: 4373. [Epub ahead of print]24(5):
    mtR_find: A Parallel Processing Tool to Identify and Annotate RNAs Derived from the Mitochondrial Genome.
    Asan M S H Mohideen, Steinar D Johansen, Igor Babiak.
      RNAs originating from mitochondrial genomes are abundant in transcriptomic datasets produced by high-throughput sequencing technologies, primarily in short-read outputs. Specific features of mitochondrial small RNAs (mt-sRNAs), such as non-templated additions, presence of length variants, sequence variants, and other modifications, necessitate the need for the development of an appropriate tool for their effective identification and annotation. We have developed mtR_find, a tool to detect and annotate mitochondrial RNAs, including mt-sRNAs and mitochondria-derived long non-coding RNAs (mt-lncRNA). mtR_find uses a novel method to compute the count of RNA sequences from adapter-trimmed reads. When analyzing the published datasets with mtR_find, we identified mt-sRNAs significantly associated with the health conditions, such as hepatocellular carcinoma and obesity, and we discovered novel mt-sRNAs. Furthermore, we identified mt-lncRNAs in early development in mice. These examples show the immediate impact of miR_find in extracting a novel biological information from the existing sequencing datasets. For benchmarking, the tool has been tested on a simulated dataset and the results were concordant. For accurate annotation of mitochondria-derived RNA, particularly mt-sRNA, we developed an appropriate nomenclature. mtR_find encompasses the mt-ncRNA transcriptomes in unpreceded resolution and simplicity, allowing re-analysis of the existing transcriptomic databases and the use of mt-ncRNAs as diagnostic or prognostic markers in the field of medicine.
    Keywords:  mitochondria; mitochondrial long non-coding RNAs; mitochondrial small RNAs; mitochondrial tRFs; multiprocessing; read count algorithm; small RNA tool
    DOI:  https://doi.org/10.3390/ijms24054373
  30. Trends Cell Biol. 2023 Mar 04. pii: S0962-8924(23)00023-5. [Epub ahead of print]
    The autophagy-NAD axis in longevity and disease.
    Niall Wilson, Tetsushi Kataura, Miriam E Korsgen, Congxin Sun, Sovan Sarkar, Viktor I Korolchuk.
      Autophagy is an intracellular degradation pathway that recycles subcellular components to maintain metabolic homeostasis. NAD is an essential metabolite that participates in energy metabolism and serves as a substrate for a series of NAD+-consuming enzymes (NADases), including PARPs and SIRTs. Declining levels of autophagic activity and NAD represent features of cellular ageing, and consequently enhancing either significantly extends health/lifespan in animals and normalises metabolic activity in cells. Mechanistically, it has been shown that NADases can directly regulate autophagy and mitochondrial quality control. Conversely, autophagy has been shown to preserve NAD levels by modulating cellular stress. In this review we highlight the mechanisms underlying this bidirectional relationship between NAD and autophagy, and the potential therapeutic targets it provides for combatting age-related disease and promoting longevity.
    Keywords:  PARP; Parkinson's disease; ageing; mitophagy; neurodegeneration; nicotinamide; sirtuins
    DOI:  https://doi.org/10.1016/j.tcb.2023.02.004
  31. EMBO J. 2023 Mar 06. e113576
    MitoStores: a place for precursors to ride out the storm.
    Megan Balzarini, Zixuan Yuan, Hilla Weidberg.
      The fate of unimported mitochondrial precursors has been increasingly studied in recent years, mostly focusing on protein degradation. In this issue of the EMBO journal, Krämer et al discovered MitoStores, a new protective mechanism that temporarily stores mitochondrial proteins in cytosolic deposits.
    DOI:  https://doi.org/10.15252/embj.2023113576
  32. Int J Mol Sci. 2023 Mar 01. pii: 4724. [Epub ahead of print]24(5):
    Multi-Omics Profiling of Hypertrophic Cardiomyopathy Reveals Altered Mechanisms in Mitochondrial Dynamics and Excitation-Contraction Coupling.
    Jarrod Moore, Jourdan Ewoldt, Gabriela Venturini, Alexandre C Pereira, Kallyandra Padilha, Matthew Lawton, Weiwei Lin, Raghuveera Goel, Ivan Luptak, Valentina Perissi, Christine E Seidman, Jonathan Seidman, Michael T Chin, Christopher Chen, Andrew Emili.
      Hypertrophic cardiomyopathy is one of the most common inherited cardiomyopathies and a leading cause of sudden cardiac death in young adults. Despite profound insights into the genetics, there is imperfect correlation between mutation and clinical prognosis, suggesting complex molecular cascades driving pathogenesis. To investigate this, we performed an integrated quantitative multi-omics (proteomic, phosphoproteomic, and metabolomic) analysis to illuminate the early and direct consequences of mutations in myosin heavy chain in engineered human induced pluripotent stem-cell-derived cardiomyocytes relative to late-stage disease using patient myectomies. We captured hundreds of differential features, which map to distinct molecular mechanisms modulating mitochondrial homeostasis at the earliest stages of pathobiology, as well as stage-specific metabolic and excitation-coupling maladaptation. Collectively, this study fills in gaps from previous studies by expanding knowledge of the initial responses to mutations that protect cells against the early stress prior to contractile dysfunction and overt disease.
    Keywords:  human induced pluripotent stem-cell-derived cardiomyocytes; hypertrophic cardiomyopathy; liquid chromatography–tandem mass spectrometry; metabolomics; myectomy; network systems biology; phosphoproteomics
    DOI:  https://doi.org/10.3390/ijms24054724
  33. Magn Reson Chem. 2023 Mar 07.
    Monitoring Live Mitochondrial Metabolism in Real-Time Using NMR Spectroscopy.
    G A Nagana Gowda, Vadim Pascua, John A Lusk, Natalie N Hong, Lin Guo, Jiang Dong, Ian R Sweet, Daniel Raftery.
      Investigation of mitochondrial metabolism is gaining increased interest owing to the growing recognition of the role of mitochondria in health and numerous diseases. Studies of isolated mitochondria promise novel insights into the metabolism devoid of confounding effects from other cellular organelles such as cytoplasm. This study describes the isolation of mitochondria from mouse skeletal myoblast cells (C2C12) and the investigation of live mitochondrial metabolism in real time using isotope tracer-based NMR spectroscopy. [3-13 C1 ]pyruvate was used as the substrate to monitor the dynamic changes of the downstream metabolites in mitochondria. The results demonstrate an intriguing phenomenon, in which lactate is produced from pyruvate inside the mitochondria and the results were confirmed by treating mitochondria with an inhibitor of mitochondrial pyruvate carrier (UK5099). Lactate is associated with health and numerous diseases including cancer and, to date, it is known to occur only in the cytoplasm. The insight that lactate is also produced inside mitochondria opens avenues for exploring new pathways of lactate metabolism. Further, experiments performed using inhibitors of the mitochondrial respiratory chain, FCCP and rotenone, show that [2-13 C1 ]acetyl coenzyme A, which is produced from [3-13 C1 ]pyruvate and acts as a primary substrate for the tricarboxylic acid cycle in mitochondria, exhibits a remarkable sensitivity to the inhibitors. These results offer a direct approach to visualize mitochondrial respiration through altered levels of the associated metabolites.
    Keywords:  13C; 1H; NMR; [2-13C1]acetyl coenzyme A; [3-13C1]lactate; [3-13C1]pyruvate; live mitochondria; metabolism
    DOI:  https://doi.org/10.1002/mrc.5341
  34. Cell Chem Biol. 2023 Mar 01. pii: S2451-9456(23)00055-7. [Epub ahead of print]
    Redox proteomics combined with proximity labeling enables monitoring of localized cysteine oxidation in cells.
    Eleni A Kisty, Julia A Falco, Eranthie Weerapana.
      Reactive oxygen species (ROS) can modulate protein function through cysteine oxidation. Identifying protein targets of ROS can provide insight into uncharacterized ROS-regulated pathways. Several redox-proteomic workflows, such as oxidative isotope-coded affinity tags (OxICAT), exist to identify sites of cysteine oxidation. However, determining ROS targets localized within subcellular compartments and ROS hotspots remains challenging with existing workflows. Here, we present a chemoproteomic platform, PL-OxICAT, which combines proximity labeling (PL) with OxICAT to monitor localized cysteine oxidation events. We show that TurboID-based PL-OxICAT can monitor cysteine oxidation events within subcellular compartments such as the mitochondrial matrix and intermembrane space. Furthermore, we use ascorbate peroxidase (APEX)-based PL-OxICAT to monitor oxidation events within ROS hotspots by using endogenous ROS as the source of peroxide for APEX activation. Together, these platforms further hone our ability to monitor cysteine oxidation events within specific subcellular locations and ROS hotspots and provide a deeper understanding of the protein targets of endogenous and exogenous ROS.
    Keywords:  APEX; OxICAT; TurboID; cysteine oxidation; proximity labeling; reactive oxygen species
    DOI:  https://doi.org/10.1016/j.chembiol.2023.02.006
  35. Science. 2023 Mar 10. 379(6636): 996-1003
    Protein-metabolite interactomics of carbohydrate metabolism reveal regulation of lactate dehydrogenase.
    Kevin G Hicks, Ahmad A Cluntun, Heidi L Schubert, Sean R Hackett, Jordan A Berg, Paul G Leonard, Mariana A Ajalla Aleixo, Youjia Zhou, Alex J Bott, Sonia R Salvatore, Fei Chang, Aubrie Blevins, Paige Barta, Samantha Tilley, Aaron Leifer, Andrea Guzman, Ajak Arok, Sarah Fogarty, Jacob M Winter, Hee-Chul Ahn, Karen N Allen, Samuel Block, Iara A Cardoso, Jianping Ding, Ingrid Dreveny, William C Gasper, Quinn Ho, Atsushi Matsuura, Michael J Palladino, Sabin Prajapati, Pengkai Sun, Kai Tittmann, Dean R Tolan, Judith Unterlass, Andrew P VanDemark, Matthew G Vander Heiden, Bradley A Webb, Cai-Hong Yun, Pengkai Zhao, Bei Wang, Francisco J Schopfer, Christopher P Hill, Maria Cristina Nonato, Florian L Muller, James E Cox, Jared Rutter.
      Metabolic networks are interconnected and influence diverse cellular processes. The protein-metabolite interactions that mediate these networks are frequently low affinity and challenging to systematically discover. We developed mass spectrometry integrated with equilibrium dialysis for the discovery of allostery systematically (MIDAS) to identify such interactions. Analysis of 33 enzymes from human carbohydrate metabolism identified 830 protein-metabolite interactions, including known regulators, substrates, and products as well as previously unreported interactions. We functionally validated a subset of interactions, including the isoform-specific inhibition of lactate dehydrogenase by long-chain acyl-coenzyme A. Cell treatment with fatty acids caused a loss of pyruvate-lactate interconversion dependent on lactate dehydrogenase isoform expression. These protein-metabolite interactions may contribute to the dynamic, tissue-specific metabolic flexibility that enables growth and survival in an ever-changing nutrient environment.
    DOI:  https://doi.org/10.1126/science.abm3452
  36. Int J Numer Method Biomed Eng. 2023 Mar 05. e3696
    ATP diffusional gradients are sufficient to maintain bioenergetic homeostasis in synaptic boutons lacking mitochondria.
    Ivan A Kuznetsov, Andrey V Kuznetsov.
      Previous work on mitochondrial distribution in axons has shown that approximately half of the presynaptic release sites do not contain mitochondria, raising the question of how the boutons that do not contain mitochondria are supplied with ATP. Here, we develop and apply a mathematical model to study this question. Specifically, we investigate whether diffusive transport of ATP is sufficient to support the exocytic functionality in synaptic boutons which lack mitochondria. Our results demonstrate that the difference in ATP concentration between a bouton containing a mitochondrion and a neighboring bouton lacking a mitochondrion is only approximately 0.4%, which is still 3.75 times larger than the ATP concentration minimally required to support synaptic vesicle release. This work therefore suggests that passive diffusion of ATP is sufficient to maintain the functionality of boutons which do not contain mitochondria.
    Keywords:  ATP; axons; diffusion-driven transport; mathematical modeling; mitochondria
    DOI:  https://doi.org/10.1002/cnm.3696
  37. Int J Mol Sci. 2023 Feb 23. pii: 4402. [Epub ahead of print]24(5):
    Discovery-Based Proteomics Identify Skeletal Muscle Mitochondrial Alterations as an Early Metabolic Defect in a Mouse Model of β-Thalassemia.
    Patricia Reboucas, Carine Fillebeen, Amy Botta, Riley Cleverdon, Alexandra P Steele, Vincent Richard, René P Zahedi, Christoph H Borchers, Yan Burelle, Thomas J Hawke, Kostas Pantopoulos, Gary Sweeney.
      Although metabolic complications are common in thalassemia patients, there is still an unmet need to better understand underlying mechanisms. We used unbiased global proteomics to reveal molecular differences between the th3/+ mouse model of thalassemia and wild-type control animals focusing on skeletal muscles at 8 weeks of age. Our data point toward a significantly impaired mitochondrial oxidative phosphorylation. Furthermore, we observed a shift from oxidative fibre types toward more glycolytic fibre types in these animals, which was further supported by larger fibre-type cross-sectional areas in the more oxidative type fibres (type I/type IIa/type IIax hybrid). We also observed an increase in capillary density in th3/+ mice, indicative of a compensatory response. Western blotting for mitochondrial oxidative phosphorylation complex proteins and PCR analysis of mitochondrial genes indicated reduced mitochondrial content in the skeletal muscle but not the hearts of th3/+ mice. The phenotypic manifestation of these alterations was a small but significant reduction in glucose handling capacity. Overall, this study identified many important alterations in the proteome of th3/+ mice, amongst which mitochondrial defects leading to skeletal muscle remodelling and metabolic dysfunction were paramount.
    Keywords:  iron; mitochondria; proteomics; skeletal muscle; thalassemia
    DOI:  https://doi.org/10.3390/ijms24054402
  38. Nat Metab. 2023 Mar 06.
    Primary cilia sense glutamine availability and respond via asparagine synthetase.
    Maria Elena Steidl, Elisa A Nigro, Anne Kallehauge Nielsen, Roberto Pagliarini, Laura Cassina, Matteo Lampis, Christine Podrini, Marco Chiaravalli, Valeria Mannella, Gianfranco Distefano, Ming Yang, Mariam Aslanyan, Giovanna Musco, Ronald Roepman, Christian Frezza, Alessandra Boletta.
      Depriving cells of nutrients triggers an energetic crisis, which is resolved by metabolic rewiring and organelle reorganization. Primary cilia are microtubule-based organelles at the cell surface, capable of integrating multiple metabolic and signalling cues, but their precise sensory function is not fully understood. Here we show that primary cilia respond to nutrient availability and adjust their length via glutamine-mediated anaplerosis facilitated by asparagine synthetase (ASNS). Nutrient deprivation causes cilia elongation, mediated by reduced mitochondrial function, ATP availability and AMPK activation independently of mTORC1. Of note, glutamine removal and replenishment is necessary and sufficient to induce ciliary elongation or retraction, respectively, under nutrient stress conditions both in vivo and in vitro by restoring mitochondrial anaplerosis via ASNS-dependent glutamate generation. Ift88-mutant cells lacking cilia show reduced glutamine-dependent mitochondrial anaplerosis during metabolic stress, due to reduced expression and activity of ASNS at the base of cilia. Our data indicate a role for cilia in responding to, and possibly sensing, cellular glutamine levels via ASNS during metabolic stress.
    DOI:  https://doi.org/10.1038/s42255-023-00754-6
  39. Mol Metab. 2023 Mar 04. pii: S2212-8778(23)00035-2. [Epub ahead of print] 101701
    Basal re-esterification finetunes mitochondrial fatty acid utilization.
    Anand Kumar Sharma, Tongtong Wang, Alaa Othman, Radhika Khandelwal, Mioslav Balaz, Salvatore Modica, Nicola Zamboni, Christian Wolfrum.
       OBJECTIVE: Emerging evidence suggest the existence of constant basal lipolysis and re-esterification of a substantial fraction of thus liberated fatty acids. In stimulated lipolysis, the re-esterification is proposed to be a protective mechanism against lipotoxicity; however, the role of the lipolysis coupled to re-esterification under basal conditions has not been deciphered.
    METHODS: We used adipocytes (in vitro differentiated brown and white adipocytes derived from a cell line or primary SVF culture) to study the effect of inhibition of re-esterification by pharmacological DGAT1 and DGAT2 inhibitors alone or in combination. We then evaluated cellular energetics, lipolysis flux, and lipidomic parameters along with mitochondrial properties and fuel utilization.
    RESULTS: In adipocytes, DGAT1 and 2 mediated re-esterification is a moderator of fatty acid oxidation. Combined inhibition of both DGATs (D1+2i) increases oxygen consumption, which is largely due to enhanced mitochondrial respiration by lipolysis-derived fatty acids (FAs). Acute D1+2i selectively affects mitochondrial respiration without affecting the transcriptional homeostasis of genes relevant to mitochondrial health and lipid metabolism. D1+2i enhances the mitochondrial import of pyruvate and activates AMP Kinase to counteract CPT1 antagonism, thus facilitating the mitochondrial import of fatty acyl-CoA.
    CONCLUSIONS: These data implicate the process of re-esterification in the regulation of mitochondrial FA usage and uncover a mechanism of FAO regulation via crosstalk with FA re-esterification.
    Keywords:  Adipose tissue; DGAT1; DGAT2; Fatty acid oxidation; Lipidomics; Lipolysis; Re-esterification
    DOI:  https://doi.org/10.1016/j.molmet.2023.101701
  40. Nature. 2023 Mar 08.
    Macrophage fumarate hydratase restrains mtRNA-mediated interferon production.
    Alexander Hooftman, Christian G Peace, Dylan G Ryan, Emily A Day, Ming Yang, Anne F McGettrick, Maureen Yin, Erica N Montano, Lihong Huo, Juliana E Toller-Kawahisa, Vincent Zecchini, Tristram A J Ryan, Alfonso Bolado-Carrancio, Alva M Casey, Hiran A Prag, Ana S H Costa, Gabriela De Los Santos, Mariko Ishimori, Daniel J Wallace, Swamy Venuturupalli, Efterpi Nikitopoulou, Norma Frizzell, Cecilia Johansson, Alexander Von Kriegsheim, Michael P Murphy, Caroline Jefferies, Christian Frezza, Luke A J O'Neill.
      Metabolic rewiring underlies the effector functions of macrophages1-3, but the mechanisms involved remain incompletely defined. Here, using unbiased metabolomics and stable isotope-assisted tracing, we show that an inflammatory aspartate-argininosuccinate shunt is induced following lipopolysaccharide stimulation. The shunt, supported by increased argininosuccinate synthase (ASS1) expression, also leads to increased cytosolic fumarate levels and fumarate-mediated protein succination. Pharmacological inhibition and genetic ablation of the tricarboxylic acid cycle enzyme fumarate hydratase (FH) further increases intracellular fumarate levels. Mitochondrial respiration is also suppressed and mitochondrial membrane potential increased. RNA sequencing and proteomics analyses demonstrate that there are strong inflammatory effects resulting from FH inhibition. Notably, acute FH inhibition suppresses interleukin-10 expression, which leads to increased tumour necrosis factor secretion, an effect recapitulated by fumarate esters. Moreover, FH inhibition, but not fumarate esters, increases interferon-β production through mechanisms that are driven by mitochondrial RNA (mtRNA) release and activation of the RNA sensors TLR7, RIG-I and MDA5. This effect is recapitulated endogenously when FH is suppressed following prolonged lipopolysaccharide stimulation. Furthermore, cells from patients with systemic lupus erythematosus also exhibit FH suppression, which indicates a potential pathogenic role for this process in human disease. We therefore identify a protective role for FH in maintaining appropriate macrophage cytokine and interferon responses.
    DOI:  https://doi.org/10.1038/s41586-023-05720-6
  41. Cells. 2023 Feb 25. pii: 742. [Epub ahead of print]12(5):
    Mitochondria Localized microRNAs: An Unexplored miRNA Niche in Alzheimer's Disease and Aging.
    Jazmin Rivera, Laxman Gangwani, Subodh Kumar.
      Mitochondria play several vital roles in the brain cells, especially in neurons to provide synaptic energy (ATP), Ca2+ homeostasis, Reactive Oxygen Species (ROS) production, apoptosis, mitophagy, axonal transport and neurotransmission. Mitochondrial dysfunction is a well-established phenomenon in the pathophysiology of many neurological diseases, including Alzheimer's disease (AD). Amyloid-beta (Aβ) and Phosphorylated tau (p-tau) proteins cause the severe mitochondrial defects in AD. A newly discovered cellular niche of microRNAs (miRNAs), so-called mitochondrial-miRNAs (mito-miRs), has recently been explored in mitochondrial functions, cellular processes and in a few human diseases. The mitochondria localized miRNAs regulate local mitochondrial genes expression and are significantly involved in the modulation of mitochondrial proteins, and thereby in controlling mitochondrial function. Thus, mitochondrial miRNAs are crucial to maintaining mitochondrial integrity and for normal mitochondrial homeostasis. Mitochondrial dysfunction is well established in AD pathogenesis, but unfortunately mitochondria miRNAs and their precise roles have not yet been investigated in AD. Therefore, an urgent need exists to examine and decipher the critical roles of mitochondrial miRNAs in AD and in the aging process. The current perspective sheds light on the latest insights and future research directions on investigating the contribution of mitochondrial miRNAs in AD and aging.
    Keywords:  Alzheimer’s disease; aging; mitochondrial dysfunction; mitochondrial miRNAs; synaptic energy
    DOI:  https://doi.org/10.3390/cells12050742
  42. J Eur Acad Dermatol Venereol. 2023 Mar 10.
    Mitochondria-melanocyte cellular interactions : an emerging mechanism of vitiligo pathogenesis.
    Hitaishi Kaushik, Vinod Kumar, Davinder Parsad.
      Mitochondria has emerged as a potential modulator of melanocyte function other than just meeting its cellular ATP demands. Mitochondrial DNA defects are now an established cause of maternal inheritance diseases. Recent cellular studies have highlighted the mitochondrial interaction with other cellular organelles that lead to disease conditions such as in Duchenne muscular dystrophy, where defective mitochondria was found in melanocytes of these patients. Vitiligo, a depigmentory ailment of the skin, is another such disorder whose pathogenesis is now found to be associated with mitochondria. The complete absence of melanocytes at the lesioned site in vitiligo is a fact, however, the precise mechanism of this destruction is still undefined. In this review we have tried to discuss and link the emerging facts of mitochondrial function or its inter- and intra-organellar communications in vitiligo pathogenesis. Mitochondrial close association with melanosomes, molecular involvement in melanocyte-keratinocyte communication, and melanocyte survival are new paradigm of melanogenesis that could ultimately account for vitiligo. This definitely adds the new dimensions to our understanding of vitiligo, its management and designing of future mitochondrial targeted therapy for vitiligo.
    DOI:  https://doi.org/10.1111/jdv.19019
  43. Cells. 2023 Feb 21. pii: 679. [Epub ahead of print]12(5):
    Mitochondrial Dysfunction in Cardiac Arrhythmias.
    Jielin Deng, Yunqiu Jiang, Zhen Bouman Chen, June-Wha Rhee, Yingfeng Deng, Zhao V Wang.
      Electrophysiological and structural disruptions in cardiac arrhythmias are closely related to mitochondrial dysfunction. Mitochondria are an organelle generating ATP, thereby satisfying the energy demand of the incessant electrical activity in the heart. In arrhythmias, the homeostatic supply-demand relationship is impaired, which is often accompanied by progressive mitochondrial dysfunction leading to reduced ATP production and elevated reactive oxidative species generation. Furthermore, ion homeostasis, membrane excitability, and cardiac structure can be disrupted through pathological changes in gap junctions and inflammatory signaling, which results in impaired cardiac electrical homeostasis. Herein, we review the electrical and molecular mechanisms of cardiac arrhythmias, with a particular focus on mitochondrial dysfunction in ionic regulation and gap junction action. We provide an update on inherited and acquired mitochondrial dysfunction to explore the pathophysiology of different types of arrhythmias. In addition, we highlight the role of mitochondria in bradyarrhythmia, including sinus node dysfunction and atrioventricular node dysfunction. Finally, we discuss how confounding factors, such as aging, gut microbiome, cardiac reperfusion injury, and electrical stimulation, modulate mitochondrial function and cause tachyarrhythmia.
    Keywords:  ATP supply; arrhythmia; mitochondrial dysfunction; reactive oxygen species
    DOI:  https://doi.org/10.3390/cells12050679
  44. Mov Disord. 2023 Mar 07.
    Insights into Neurodegeneration in Parkinson's Disease from Single-Cell and Spatial Genomics.
    Tushar Kamath, Evan Z Macosko.
      Parkinson's disease (PD) is pathologically defined by the death of dopaminergic (DA) neurons within the pars compacta of the substantia nigra. To date, the cause of this multifaceted disease remains largely unclear, which may contribute in part to a current lack of disease-modifying therapies. Recent advances in single-cell and spatial genomic profiling tools have provided powerful new ways to measure cellular state changes in brain diseases. Here, we describe how these tools have offered insight into these complex disorders and highlight a recently performed comprehensive study of DA neuron susceptibility in PD. The data generated by this recent work provide evidence for the role of specific pathways and common genetic variants resulting in the loss of a critical DA subtype in PD. We conclude by outlining a set of basic and translational opportunities that arise from those data and insights gathered from this work. © 2023 International Parkinson and Movement Disorder Society.
    Keywords:  Parkinson's disease; dopaminergic; substantia nigra
    DOI:  https://doi.org/10.1002/mds.29374
  45. Mol Neurodegener. 2023 Mar 07. 18(1): 15
    Deficits in mitochondrial TCA cycle and OXPHOS precede rod photoreceptor degeneration during chronic HIF activation.
    Vyara Todorova, Mia Fee Stauffacher, Luca Ravotto, Sarah Nötzli, Duygu Karademir, Lynn J A Ebner, Cornelia Imsand, Luca Merolla, Stefanie M Hauck, Marijana Samardzija, Aiman S Saab, L Felipe Barros, Bruno Weber, Christian Grimm.
       BACKGROUND: Major retinal degenerative diseases, including age-related macular degeneration, diabetic retinopathy and retinal detachment, are associated with a local decrease in oxygen availability causing the formation of hypoxic areas affecting the photoreceptor (PR) cells. Here, we addressed the underlying pathological mechanisms of PR degeneration by focusing on energy metabolism during chronic activation of hypoxia-inducible factors (HIFs) in rod PR.
    METHODS: We used two-photon laser scanning microscopy (TPLSM) of genetically encoded biosensors delivered by adeno-associated viruses (AAV) to determine lactate and glucose dynamics in PR and inner retinal cells. Retinal layer-specific proteomics, in situ enzymatic assays and immunofluorescence studies were used to analyse mitochondrial metabolism in rod PRs during chronic HIF activation.
    RESULTS: PRs exhibited remarkably higher glycolytic flux through the hexokinases than neurons of the inner retina. Chronic HIF activation in rods did not cause overt change in glucose dynamics but an increase in lactate production nonetheless. Furthermore, dysregulation of the oxidative phosphorylation pathway (OXPHOS) and tricarboxylic acid (TCA) cycle in rods with an activated hypoxic response decelerated cellular anabolism causing shortening of rod photoreceptor outer segments (OS) before onset of cell degeneration. Interestingly, rods with deficient OXPHOS but an intact TCA cycle did not exhibit these early signs of anabolic dysregulation and showed a slower course of degeneration.
    CONCLUSION: Together, these data indicate an exceeding high glycolytic flux in rods and highlight the importance of mitochondrial metabolism and especially of the TCA cycle for PR survival in conditions of increased HIF activity.
    Keywords:  Aging; Energy metabolism; Hypoxia; Retinal degeneration; Retinal proteomics; Rod photoreceptor; Two-photon microscopy
    DOI:  https://doi.org/10.1186/s13024-023-00602-x
  46. STAR Protoc. 2023 Mar 06. pii: S2666-1667(23)00100-4. [Epub ahead of print]4(1): 102142
    Protocol to differentiate monolayer human induced pluripotent stem cells into inflammatory responsive astrocytes.
    Anna Maria Sole Giordano, Monah Abou Alezz, Ivan Merelli, Anna Kajaste-Rudnitski.
      Glia, and in particular astrocytes, are one of the major players in neurological and neuroinflammatory disorders. Here, we present a protocol to efficiently generate inflammatory responsive astrocytes from human induced pluripotent stem cells in a monolayer culture. We describe steps for neural differentiation to reach a homogeneous population of neural progenitor cells, followed by their differentiation into neural/glial progenitors. Finally, we detail enrichment to a 90% pure inflammatory responsive astrocyte population. For complete details on the use and execution of this protocol, please refer to Giordano et al.1.
    Keywords:  Cell Biology; Cell Differentiation; Immunology; Molecular Biology; Neuroscience; Stem Cells
    DOI:  https://doi.org/10.1016/j.xpro.2023.102142
  47. Am J Med Genet A. 2023 Mar 09.
    An atypically mild case of ethylmalonic encephalopathy with pathogenic ETHE1 variant.
    Daniel T Kashima, Christina M Sloan-Heggen, Rachel J Gottlieb-Smith, Amanda Barone Pritchard.
      Ethylmalonic encephalopathy (EE) is a rare, severe, autosomal recessive condition caused by pathogenic variants in ETHE1 leading to progressive encephalopathy, hypotonia evolving to dystonia, petechiae, orthostatic acrocyanosis, diarrhea, and elevated ethylmalonic acid in urine. In this case report, we describe a patient with only mild speech and gross motor delays, subtle biochemical abnormalities, and normal brain imaging found to be homozygous for a pathogenic ETHE1 variant (c.586G>A) via whole exome sequencing. This case highlights the clinical heterogeneity of ETHE1 mutations and the utility of whole-exome sequencing in diagnosing mild cases of EE.
    Keywords:  ETHE1 gene; ethylmalonic acid; gross-motor delay; speech delay
    DOI:  https://doi.org/10.1002/ajmg.a.63176
  48. Cells. 2023 Mar 04. pii: 806. [Epub ahead of print]12(5):
    Changes in Liver Lipidomic Profile in G2019S-LRRK2 Mouse Model of Parkinson's Disease.
    Yaiza Corral Nieto, Sokhna M S Yakhine-Diop, Paula Moreno-Cruz, Laura Manrique García, Amanda Gabrielly Pereira, José A Morales-García, Mireia Niso-Santano, Rosa A González-Polo, Elisabet Uribe-Carretero, Sylvère Durand, Maria Chiara Maiuri, Marta Paredes-Barquero, Eva Alegre-Cortés, Saray Canales-Cortés, Adolfo López de Munain, Jordi Pérez-Tur, Ana Pérez-Castillo, Guido Kroemer, José M Fuentes, José M Bravo-San Pedro.
      The identification of Parkinson's disease (PD) biomarkers has become a main goal for the diagnosis of this neurodegenerative disorder. PD has not only been intrinsically related to neurological problems, but also to a series of alterations in peripheral metabolism. The purpose of this study was to identify metabolic changes in the liver in mouse models of PD with the scope of finding new peripheral biomarkers for PD diagnosis. To achieve this goal, we used mass spectrometry technology to determine the complete metabolomic profile of liver and striatal tissue samples from WT mice, 6-hydroxydopamine-treated mice (idiopathic model) and mice affected by the G2019S-LRRK2 mutation in LRRK2/PARK8 gene (genetic model). This analysis revealed that the metabolism of carbohydrates, nucleotides and nucleosides was similarly altered in the liver from the two PD mouse models. However, long-chain fatty acids, phosphatidylcholine and other related lipid metabolites were only altered in hepatocytes from G2019S-LRRK2 mice. In summary, these results reveal specific differences, mainly in lipid metabolism, between idiopathic and genetic PD models in peripheral tissues and open up new possibilities to better understand the etiology of this neurological disorder.
    Keywords:  LRRK2; Parkinson; lipids; liver; metabolome; neurodegeneration
    DOI:  https://doi.org/10.3390/cells12050806
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