bims-mitmed 2023-07-16 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2023–07–16
43 papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

Ribonucleotide synthesis by NME6 fuels mitochondrial gene expression.
Mitochondrial transport in symmetric and asymmetric axons with multiple branching junctions: a computational study.
Mitochondrial haplotype mutation alleviates respiratory defect of MELAS by restoring taurine modification in tRNA with 3243A > G mutation.
Defects in Mitochondrial Biogenesis Drive Mitochondrial Alterations in PINK1-deficient Human Dopamine Neurons.
Longitudinal in vivo metabolic labeling reveals tissue-specific mitochondrial proteome turnover rates and proteins selectively altered by parkin deficiency.
Local coordination of mRNA storage and degradation near mitochondria modulates C. elegans ageing.
Immunoproteasome-specific subunit PSMB9 induction is required to regulate cellular proteostasis upon mitochondrial dysfunction.
A case of mitochondrial DNA depletion syndrome type 11 - expanding the genotype and phenotype.
Mitochondrial respiratory complex I deficiency inhibits brown adipogenesis by limiting heme regulation of histone demethylation.
Conduction Defects in Pediatric Patients with Pearson Syndrome: When to Pace?
Succinyl-CoA Synthetase Dysfunction as a Mechanism of Mitochondrial Encephalomyopathy: More than Just an Oxidative Energy Deficit.
Targeting the TCA cycle can ameliorate widespread axonal energy deficiency in neuroinflammatory lesions.
Loss of STING in parkin mutant flies suppresses muscle defects and mitochondria damage.
Drug Drop Test: How to Quickly Identify Potential Therapeutic Compounds for Mitochondrial Diseases Using Yeast Saccharomyces cerevisiae.
The role of placental aging in adverse pregnancy outcomes: A mitochondrial perspective.
MSTO1 is a cytoplasmic pro-mitochondrial fusion protein, whose mutation induces myopathy and ataxia in humans.
Mitochondrial Dysfunction and Skeletal Muscle Atrophy: Causes, Mechanisms, and Treatment Strategies.
Eight diseases for gene therapy accelerator.
Mitochondria-derived peptides in healthy ageing and therapy of age-related diseases.
Regulation of mitochondrial morphology and cristae architecture by the TLR4 pathway in human skeletal muscle.
Duchenne muscular dystrophy: disease mechanism and therapeutic strategies.
The Troyer syndrome protein spartin mediates selective autophagy of lipid droplets.
IF1 ablation prevents ATP synthase oligomerization, enhances mitochondrial ATP turnover and promotes an adenosine-mediated pro-inflammatory phenotype.
Mitochondrial DNA Analysis.
Disruption of mitochondrial and lysosomal functions by human CACNA1C variants expressed in HEK 293 and CHO cells.
Maintenance of cellular vitamin B6 levels and mitochondrial oxidative function depend on pyridoxal 5'-phosphate homeostasis protein (PLPHP).
Mitochondria-derived cell-to-cell communication.
Hyporeninemic hypoaldosteronism in RMND1-related mitochondrial disease.
The Highs and Lows of Memantine-An Autophagy and Mitophagy Inducing Agent That Protects Mitochondria.
NAD+ precursor nutritional supplements sensitize the brain to future ischemic events.
Glutathione limits RUNX2 oxidation and degradation to regulate bone formation.
Pathophysiology of Cerebellar Degeneration in Mitochondrial Disorders: Insights from the Harlequin Mouse.
Fetal manipulation of maternal metabolism is a critical function of the imprinted Igf2 gene.
A framework for individualized splice-switching oligonucleotide therapy.
Mitochondrial quality control and its emerging role in the pathogenesis of diabetic kidney disease.
NAD metabolism: Role in senescence regulation and aging.
High-Resolution Respirometry to Assess Mitochondrial Function in Human Spermatozoa.
NAD metabolism modulates inflammation and mitochondria function in diabetic kidney disease.
Increased mitochondrial free Ca2+ during ischemia is suppressed, but not eliminated by, germline deletion of the mitochondrial Ca2+ uniporter.
Mitofusin-2 in nucleus accumbens D2-MSNs regulates social dominance and neuronal function.
Tethering ATG16L1 or LC3 induces targeted autophagic degradation of protein aggregates and mitochondria.
TCA cycle deficiency in multiple sclerosis.
Cell fragmentation in mouse preimplantation embryos induced by ectopic activation of the polar body extrusion pathway.

EMBO J. 2023 Jul 13. e113256

Ribonucleotide synthesis by NME6 fuels mitochondrial gene expression.

Nils Grotehans, Lynn McGarry, Hendrik Nolte, Vanessa Xavier, Moritz Kroker, Álvaro Jesús Narbona-Pérez, Soni Deshwal, Patrick Giavalisco, Thomas Langer, Thomas MacVicar.

  Replication of the mitochondrial genome and expression of the genes it encodes both depend on a sufficient supply of nucleotides to mitochondria. Accordingly, dysregulated nucleotide metabolism not only destabilises the mitochondrial genome, but also affects its transcription. Here, we report that a mitochondrial nucleoside diphosphate kinase, NME6, supplies mitochondria with pyrimidine ribonucleotides that are necessary for the transcription of mitochondrial genes. Loss of NME6 function leads to the depletion of mitochondrial transcripts, as well as destabilisation of the electron transport chain and impaired oxidative phosphorylation. These deficiencies are rescued by an exogenous supply of pyrimidine ribonucleosides. Moreover, NME6 is required for the maintenance of mitochondrial DNA when the access to cytosolic pyrimidine deoxyribonucleotides is limited. Our results therefore reveal an important role for ribonucleotide salvage in mitochondrial gene expression.

Keywords:  NME6; mitochondria; mitochondrial DNA; mitochondrial transcription; nucleotide metabolism

DOI:  https://doi.org/10.15252/embj.2022113256
Comput Methods Biomech Biomed Engin. 2023 Jul 10. 1-20

Mitochondrial transport in symmetric and asymmetric axons with multiple branching junctions: a computational study.

Ivan A Kuznetsov, Andrey V Kuznetsov.

  Mitochondrial aging has been proposed to be involved in a variety of neurodegenerative disorders, such as Parkinson's disease. Here, we explore the impact of multiple branching junctions in axons on the mean age of mitochondria and their age density distributions in demand sites. The study examined mitochondrial concentration, mean age, and age density distribution in relation to the distance from the soma. We developed models for a symmetric axon containing 14 demand sites and an asymmetric axon containing 10 demand sites. We investigated how the concentration of mitochondria changes when an axon splits into two branches at the branching junction. Additionally, we studied whether mitochondrial concentrations in the branches are affected by what proportion of mitochondrial flux enters the upper branch versus the lower branch. Furthermore, we explored whether the distributions of mitochondrial mean age and age density in branching axons are affected by how the mitochondrial flux splits at the branching junction. When the mitochondrial flux is unevenly split at the branching junction of an asymmetric axon, with a greater proportion of the flux entering the longer branch, the average age of mitochondria (system age) in the axon increases. Our findings elucidate the effects of axonal branching on the mitochondrial age.

Keywords:  Neurodegeneration; Parkinson’s disease; computational biology; large axonal arbors; mitochondrial aging

DOI:  https://doi.org/10.1080/10255842.2023.2226787
Nucleic Acids Res. 2023 Jul 13. pii: gkad591. [Epub ahead of print]

Mitochondrial haplotype mutation alleviates respiratory defect of MELAS by restoring taurine modification in tRNA with 3243A > G mutation.

Saori Ueda, Mikako Yagi, Ena Tomoda, Shinya Matsumoto, Yasushi Ueyanagi, Yura Do, Daiki Setoyama, Yuichi Matsushima, Asuteka Nagao, Tsutomu Suzuki, Tomomi Ide, Yusuke Mori, Noriko Oyama, Dongchon Kang, Takeshi Uchiumi.

The 3243A > G in mtDNA is a representative mutation in mitochondrial diseases. Mitochondrial protein synthesis is impaired due to decoding disorder caused by severe reduction of 5-taurinomethyluridine (τm5U) modification of the mutant mt-tRNALeu(UUR) bearing 3243A > G mutation. The 3243A > G heteroplasmy in peripheral blood reportedly decreases exponentially with age. Here, we found three cases with mild respiratory symptoms despite bearing high rate of 3243A > G mutation (>90%) in blood mtDNA. These patients had the 3290T > C haplotypic mutation in addition to 3243A > G pathogenic mutation in mt-tRNALeu(UUR) gene. We generated cybrid cells of these cases to examine the effects of the 3290T > C mutation on mitochondrial function and found that 3290T > C mutation improved mitochondrial translation, formation of respiratory chain complex, and oxygen consumption rate of pathogenic cells associated with 3243A > G mutation. We measured τm5U frequency of mt-tRNALeu(UUR) with 3243A > G mutation in the cybrids by a primer extension method assisted with chemical derivatization of τm5U, showing that hypomodification of τm5U was significantly restored by the 3290T > C haplotypic mutation. We concluded that the 3290T > C is a haplotypic mutation that suppresses respiratory deficiency of mitochondrial disease by restoring hypomodified τm5U in mt-tRNALeu(UUR) with 3243A > G mutation, implying a potential therapeutic measure for mitochondrial disease associated with pathogenic mutations in mt-tRNAs.

DOI: https://doi.org/10.1093/nar/gkad591
bioRxiv. 2023 Jun 26. pii: 2023.06.23.546087. [Epub ahead of print]

Defects in Mitochondrial Biogenesis Drive Mitochondrial Alterations in PINK1-deficient Human Dopamine Neurons.

Hu Wang, Rong Chen, Liming Xiao, Manoj Kumar, Jesús Acevedo-Cintrón, Joanna Siuda, Dariusz Koziorowski, Zbigniew K Wszolek, Valina L Dawson, Ted M Dawson.

Mutations and loss of activity in the protein kinase PINK1 play a role in the pathogenesis of Parkinson's disease (PD). PINK1 regulates many aspects of mitochondrial quality control including mitochondrial autophagy (mitophagy), fission, fusion, transport, and biogenesis. Defects in mitophagy are though to play a predominant role in the loss of dopamine (DA) neurons in PD. Here we show that, although there are defects in mitophagy in human DA neurons lacking PINK1, mitochondrial deficits induced by the absence of PINK1 are primarily due to defects in mitochondrial biogenesis. Upregulation of PARIS and the subsequent down regulation of PGC-1α accounts for the mitochondrial biogenesis defects. CRISPR/Cas9 knockdown of PARIS completely restores the mitochondrial biogenesis defects and mitochondrial function without impacting the deficits in mitophagy due to the absence of PINK1. These results highlight the importance mitochondrial biogenesis in the pathogenesis of PD due to inactivation or loss of PINK1 in human DA neurons.

DOI: https://doi.org/10.1101/2023.06.23.546087
Sci Rep. 2023 Jul 14. 13(1): 11414

Longitudinal in vivo metabolic labeling reveals tissue-specific mitochondrial proteome turnover rates and proteins selectively altered by parkin deficiency.

K L Stauch, S Totusek, A J Trease, L D Estrella, K Emanuel, A Fangmeier, H S Fox.

Our study utilizes a longitudinal isotopic metabolic labeling approach in vivo in combination with organelle fraction proteomics to address the role of parkin in mitochondrial protein turnover in mice. The use of metabolic labeling provides a method to quantitatively determine the global changes in protein half-lives whilst simultaneously assessing protein expression. Studying two diverse mitochondrial populations, we demonstrated the median half-life of brain striatal synaptic mitochondrial proteins is significantly greater than that of hepatic mitochondrial proteins (25.7 vs. 3.5 days). Furthermore, loss of parkin resulted in an overall, albeit modest, increase in both mitochondrial protein abundance and half-life. Pathway and functional analysis of our proteomics data identified both known and novel pathways affected by loss of parkin that are consistent with its role in both mitochondrial quality control and neurodegeneration. Our study therefore adds to a growing body of evidence suggesting dependence on parkin is low for basal mitophagy in vivo and provides a foundation for the investigation of novel parkin targets.

DOI: https://doi.org/10.1038/s41598-023-38484-0
EMBO J. 2023 Jul 10. e112446

Local coordination of mRNA storage and degradation near mitochondria modulates C. elegans ageing.

Ioanna Daskalaki, Maria Markaki, Ilias Gkikas, Nektarios Tavernarakis.

  Mitochondria are central regulators of healthspan and lifespan, yet the intricate choreography of multiple, tightly controlled steps regulating mitochondrial biogenesis remains poorly understood. Here, we uncover a pivotal role for specific elements of the 5'-3' mRNA degradation pathway in the regulation of mitochondrial abundance and function. We find that the mRNA degradation and the poly-A tail deadenylase CCR4-NOT complexes form distinct foci in somatic Caenorhabditis elegans cells that physically and functionally associate with mitochondria. Components of these two multi-subunit complexes bind transcripts of nuclear-encoded mitochondria-targeted proteins to regulate mitochondrial biogenesis during ageing in an opposite manner. In addition, we show that balanced degradation and storage of mitochondria-targeted protein mRNAs are critical for mitochondrial homeostasis, stress resistance and longevity. Our findings reveal a multifaceted role of mRNA metabolism in mitochondrial biogenesis and show that fine-tuning of mRNA turnover and local translation control mitochondrial abundance and promote longevity in response to stress and during ageing.

Keywords:  ageing; mRNA metabolism; mitochondria; protein synthesis; stress

DOI:  https://doi.org/10.15252/embj.2022112446
Nat Commun. 2023 07 11. 14(1): 4092

Immunoproteasome-specific subunit PSMB9 induction is required to regulate cellular proteostasis upon mitochondrial dysfunction.

Minji Kim, Remigiusz A Serwa, Lukasz Samluk, Ida Suppanz, Agata Kodroń, Tomasz M Stępkowski, Praveenraj Elancheliyan, Biniyam Tsegaye, Silke Oeljeklaus, Michal Wasilewski, Bettina Warscheid, Agnieszka Chacinska.

Perturbed cellular protein homeostasis (proteostasis) and mitochondrial dysfunction play an important role in neurodegenerative diseases, however, the interplay between these two phenomena remains unclear. Mitochondrial dysfunction leads to a delay in mitochondrial protein import, causing accumulation of non-imported mitochondrial proteins in the cytosol and challenging proteostasis. Cells respond by increasing proteasome activity and molecular chaperones in yeast and C. elegans. Here, we demonstrate that in human cells mitochondrial dysfunction leads to the upregulation of a chaperone HSPB1 and, interestingly, an immunoproteasome-specific subunit PSMB9. Moreover, PSMB9 expression is dependent on the translation elongation factor EEF1A2. These mechanisms constitute a defense response to preserve cellular proteostasis under mitochondrial stress. Our findings define a mode of proteasomal activation through the change in proteasome composition driven by EEF1A2 and its spatial regulation, and are useful to formulate therapies to prevent neurodegenerative diseases.

DOI: https://doi.org/10.1038/s41467-023-39642-8
Neuromuscul Disord. 2023 Jun 21. pii: S0960-8966(23)00152-9. [Epub ahead of print]

A case of mitochondrial DNA depletion syndrome type 11 - expanding the genotype and phenotype.

Emanuelle Bianchi da Silva Rocha, Ketteny de Lima Rodrigues, Laura Alonso Matheus Montouro, Érica Nogueira Coelho, João Aris Kouyoumdjian, Fernando Kok, Paulo Ribeiro Nóbrega, Carla Renata Graca, Maria da Penha Ananias Morita, Eduardo de Paula Estephan.

  Mitochondrial DNA depletion syndrome type 11 (MTDPS11) is caused by pathogenic variants in MGME1 gene. We report a woman, 40-year-old, who presented slow progressive drop eyelid at 11-year-old with, learning difficulty and frequent falls. Phisical examination revealed: mild scoliosis, elbow hyperextensibility, flat feet, chronic progressive external ophthalmoplegia with upper eyelid ptosis, diffuse hypotonia, and weakness of arm abduction and neck flexion. Investigation evidenced mild serum creatine kinase increase and glucose intolerance; second-degree atrioventricular block; mild mixed-type respiratory disorder and atrophy and granular appearance of the retinal pigment epithelium. Brain magnetic resonance showed cerebellar atrophy. Muscle biopsy was compatible with mitochondrial myopathy. Genetic panel revealed a homozygous pathogenic variant in the MGME1 gene, consistent with MTDPS11 (c.862C>T; p.Gln288*). This case of MTDPS11 can contribute to the phenotypic characterization of this ultra-rare mitochondrial disorder, presenting milder respiratory and nutritional involvement than the previously reported cases, with possible additional features.

Keywords:  Chronic progressive external ophthalmoplegia; MGME1; Mitochondrial diseases; mtDNA depletion syndrome

DOI:  https://doi.org/10.1016/j.nmd.2023.06.004
Mitochondrion. 2023 Jul 12. pii: S1567-7249(23)00067-3. [Epub ahead of print]

Mitochondrial respiratory complex I deficiency inhibits brown adipogenesis by limiting heme regulation of histone demethylation.

Jingjing Liu, Wen Lu, Dongyue Yan, Junyuan Guo, Li Zhou, Bimin Shi, Xiong Su.

  Mitochondrial functions play a crucial role in determining the metabolic and thermogenic status of brown adipocytes. Increasing evidence reveals that the mitochondrial oxidative phosphorylation (OXPHOS) system plays an important role in brown adipogenesis, but the mechanistic insights are limited. Herein, we explored the potential metabolic mechanisms leading to OXPHOS regulation of brown adipogenesis in pharmacological and genetic models of mitochondrial respiratory complex I deficiency. OXPHOS deficiency inhibits brown adipogenesis through disruption of the brown adipogenic transcription circuit without affecting ATP levels. Neither blockage of calcium signaling nor antioxidant treatment can rescue the suppressed brown adipogenesis. Metabolomics analysis revealed a decrease in levels of tricarboxylic acid cycle intermediates and heme. Heme supplementation specifically enhances respiratory complex I activity without affecting complex II and partially reverses the inhibited brown adipogenesis by OXPHOS deficiency. Moreover, the regulation of brown adipogenesis by the OXPHOS-heme axis may be due to the suppressed histone methylation status by increasing histone demethylation. In summary, our findings identified a heme-sensing retrograde signaling pathway that connects mitochondrial OXPHOS to the regulation of brown adipocyte differentiation and metabolic functions.

Keywords:  brown adipocytes; differentiation; heme; histone methylation; oxidative phosphorylation

DOI:  https://doi.org/10.1016/j.mito.2023.07.004
Heart Rhythm. 2023 Jul 11. pii: S1547-5271(23)02414-1. [Epub ahead of print]

Conduction Defects in Pediatric Patients with Pearson Syndrome: When to Pace?

Saneeha Shahid, Iqbal El Assaad, Akash Patel, Sumit Parikh, Peter F Aziz.



Keywords:  Pearson syndrome; conduction defect; heart block; mitochondrial disease; pacemaker

DOI:  https://doi.org/10.1016/j.hrthm.2023.07.004
Int J Mol Sci. 2023 Jun 27. pii: 10725. [Epub ahead of print]24(13):

Succinyl-CoA Synthetase Dysfunction as a Mechanism of Mitochondrial Encephalomyopathy: More than Just an Oxidative Energy Deficit.

Makayla S Lancaster, Brett H Graham.

  Biallelic pathogenic variants in subunits of succinyl-CoA synthetase (SCS), a tricarboxylic acid (TCA) cycle enzyme, are associated with mitochondrial encephalomyopathy in humans. SCS catalyzes the interconversion of succinyl-CoA to succinate, coupled to substrate-level phosphorylation of either ADP or GDP, within the TCA cycle. SCS-deficient encephalomyopathy typically presents in infancy and early childhood, with many patients succumbing to the disease during childhood. Common symptoms include abnormal brain MRI, basal ganglia lesions and cerebral atrophy, severe hypotonia, dystonia, progressive psychomotor regression, and growth deficits. Although subunits of SCS were first identified as causal genes for progressive metabolic encephalomyopathy in the early 2000s, recent investigations are now beginning to unravel the pathomechanisms underlying this metabolic disorder. This article reviews the current understanding of SCS function within and outside the TCA cycle as it relates to the complex and multifactorial mechanisms underlying SCS-related mitochondrial encephalomyopathy.

Keywords:  encephalomyopathy; mitochondria; mitochondrial DNA; protein succinylation; succinyl-CoA synthetase; tricarboxylic acid cycle

DOI:  https://doi.org/10.3390/ijms241310725
Nat Metab. 2023 Jul 10.

Targeting the TCA cycle can ameliorate widespread axonal energy deficiency in neuroinflammatory lesions.

Yi-Heng Tai, Daniel Engels, Giuseppe Locatelli, Ioanna Emmanouilidis, Caroline Fecher, Delphine Theodorou, Stephan A Müller, Simon Licht-Mayer, Mario Kreutzfeldt, Ingrid Wagner, Natalia Prudente de Mello, Sofia-Natsouko Gkotzamani, Laura Trovò, Arek Kendirli, Almir Aljović, Michael O Breckwoldt, Ronald Naumann, Florence M Bareyre, Fabiana Perocchi, Don Mahad, Doron Merkler, Stefan F Lichtenthaler, Martin Kerschensteiner, Thomas Misgeld.

Inflammation in the central nervous system can impair the function of neuronal mitochondria and contributes to axon degeneration in the common neuroinflammatory disease multiple sclerosis (MS). Here we combine cell-type-specific mitochondrial proteomics with in vivo biosensor imaging to dissect how inflammation alters the molecular composition and functional capacity of neuronal mitochondria. We show that neuroinflammatory lesions in the mouse spinal cord cause widespread and persisting axonal ATP deficiency, which precedes mitochondrial oxidation and calcium overload. This axonal energy deficiency is associated with impaired electron transport chain function, but also an upstream imbalance of tricarboxylic acid (TCA) cycle enzymes, with several, including key rate-limiting, enzymes being depleted in neuronal mitochondria in experimental models and in MS lesions. Notably, viral overexpression of individual TCA enzymes can ameliorate the axonal energy deficits in neuroinflammatory lesions, suggesting that TCA cycle dysfunction in MS may be amendable to therapy.

DOI: https://doi.org/10.1038/s42255-023-00838-3
PLoS Genet. 2023 Jul 13. 19(7): e1010828

Loss of STING in parkin mutant flies suppresses muscle defects and mitochondria damage.

Andrew T Moehlman, Gil Kanfer, Richard J Youle.

The early pathogenesis and underlying molecular causes of motor neuron degeneration in Parkinson's Disease (PD) remains unresolved. In the model organism Drosophila melanogaster, loss of the early-onset PD gene parkin (the ortholog of human PRKN) results in impaired climbing ability, damage to the indirect flight muscles, and mitochondrial fragmentation with swelling. These stressed mitochondria have been proposed to activate innate immune pathways through release of damage associated molecular patterns (DAMPs). Parkin-mediated mitophagy is hypothesized to suppress mitochondrial damage and subsequent activation of the cGAS/STING innate immunity pathway, but the relevance of this interaction in the fly remains unresolved. Using a combination of genetics, immunoassays, and RNA sequencing, we investigated a potential role for STING in the onset of parkin-null phenotypes. Our findings demonstrate that loss of Drosophila STING in flies rescues the thorax muscle defects and the climbing ability of parkin-/- mutants. Loss of STING also suppresses the disrupted mitochondrial morphology in parkin-/- flight muscles, suggesting unexpected feedback of STING on mitochondria integrity or activation of a compensatory mitochondrial pathway. In the animals lacking both parkin and sting, PINK1 is activated and cell death pathways are suppressed. These findings support a unique, non-canonical role for Drosophila STING in the cellular and organismal response to mitochondria stress.

DOI: https://doi.org/10.1371/journal.pgen.1010828
Int J Mol Sci. 2023 Jun 27. pii: 10696. [Epub ahead of print]24(13):

Drug Drop Test: How to Quickly Identify Potential Therapeutic Compounds for Mitochondrial Diseases Using Yeast Saccharomyces cerevisiae.

Martina Magistrati, Alexandru Ionut Gilea, Maria Carla Gerra, Enrico Baruffini, Cristina Dallabona.

  Mitochondrial diseases (MDs) refer to a group of clinically and genetically heterogeneous pathologies characterized by defective mitochondrial function and energy production. Unfortunately, there is no effective treatment for most MDs, and current therapeutic management is limited to relieving symptoms. The yeast Saccharomyces cerevisiae has been efficiently used as a model organism to study mitochondria-related disorders thanks to its easy manipulation and well-known mitochondrial biogenesis and metabolism. It has been successfully exploited both to validate alleged pathogenic variants identified in patients and to discover potential beneficial molecules for their treatment. The so-called "drug drop test", a phenotype-based high-throughput screening, especially if coupled with a drug repurposing approach, allows the identification of molecules with high translational potential in a cost-effective and time-saving manner. In addition to drug identification, S. cerevisiae can be used to point out the drug's target or pathway. To date, drug drop tests have been successfully carried out for a variety of disease models, leading to very promising results. The most relevant aspect is that studies on more complex model organisms confirmed the effectiveness of the drugs, strengthening the results obtained in yeast and demonstrating the usefulness of this screening as a novel approach to revealing new therapeutic molecules for MDs.

Keywords:  Saccharomyces cerevisiae; drug drop test; drug repurposing; mitochondrial diseases; yeast model

DOI:  https://doi.org/10.3390/ijms241310696
Life Sci. 2023 Jul 08. pii: S0024-3205(23)00559-3. [Epub ahead of print] 121924

The role of placental aging in adverse pregnancy outcomes: A mitochondrial perspective.

Meijun Pan, Jing Zhou, Jing Wang, Wenli Cao, Lisha Li, Ling Wang.

  Premature placental aging is associated with placental insufficiency, which reduces the functional capacity of the placenta, leading to adverse pregnancy outcomes. Placental mitochondria are vital organelles that provide energy and play essential roles in placental development and functional maintenance. In response to oxidative stress, damage, and senescence, an adaptive response is induced to selectively remove mitochondria through the mitochondrial equivalent of autophagy. However, adaptation can be disrupted when mitochondrial abnormalities or dysfunctions persist. This review focuses on the adaptation and transformation of mitochondria during pregnancy. These changes modify placental function throughout pregnancy and can cause complications. We discuss the relationship between placental aging and adverse pregnancy outcomes from the perspective of mitochondria and potential approaches to improve abnormal pregnancy outcomes.

Keywords:  Adverse pregnancy outcomes; Bioenergetics; Mitochondria; Mitochondrial morphology; Placental aging

DOI:  https://doi.org/10.1016/j.lfs.2023.121924
EMBO Mol Med. 2023 Jul 11. e17911

MSTO1 is a cytoplasmic pro-mitochondrial fusion protein, whose mutation induces myopathy and ataxia in humans.

Aniko Gal, Peter Balicza, David Weaver, Shamim Naghdi, Suresh K Joseph, Péter Várnai, Tibor Gyuris, Attila Horváth, Laszlo Nagy, Erin L Seifert, Maria Judit Molnar, György Hajnóczky.

DOI: https://doi.org/10.15252/emmm.202317911
Mitochondrion. 2023 Jul 12. pii: S1567-7249(23)00066-1. [Epub ahead of print]

Mitochondrial Dysfunction and Skeletal Muscle Atrophy: Causes, Mechanisms, and Treatment Strategies.

Gokhan Burcin Kubat, Esmaa Bouhamida, Oner Ulger, Ibrahim Turkel, Gaia Pedriali, Daniela Ramaccini, Ozgur Ekinci, Berkay Ozerklig, Ozbeyen Atalay, Simone Patergnani, Beyza Nur Sahin, Giampaolo Morciano, Meltem Tuncer, Elena Tremoli, Paolo Pinton.

  Skeletal muscle, which accounts for approximately 40% of total body weight, is one of the most dynamic and plastic tissues in the human body and plays a vital role in movement, posture and force production. More than just a component of the locomotor system, skeletal muscle functions as an endocrine organ capable of producing and secreting hundreds of bioactive molecules. Therefore, maintaining healthy skeletal muscles is crucial for supporting overall body health. Various pathological conditions, such as prolonged immobilization, cachexia, aging, drug-induced toxicity, and cardiovascular diseases (CVDs), can disrupt the balance between muscle protein synthesis and degradation, leading to skeletal muscle atrophy. Mitochondrial dysfunction is a major contributing mechanism to skeletal muscle atrophy, as it plays crucial roles in various biological processes, including energy production, metabolic flexibility, maintenance of redox homeostasis, and regulation of apoptosis. In this review, we critically examine recent knowledge regarding the causes of muscle atrophy (disuse, cachexia, aging, etc.) and its contribution to CVDs. Additionally, we highlight the mitochondrial signaling pathways involvement to skeletal muscle atrophy, such as the ubiquitin-proteasome system, autophagy and mitophagy, mitochondrial fission-fusion, and mitochondrial biogenesis. Furthermore, we discuss current strategies, including exercise, mitochondria-targeted antioxidants, in vivo transfection of PGC-1α, and the potential use of mitochondrial transplantation as a possible therapeutic approach.

Keywords:  Skeletal muscle atrophy; cardiovascular diseases; exercise; mitochondria; mitochondrial transplantation

DOI:  https://doi.org/10.1016/j.mito.2023.07.003
Nat Biotechnol. 2023 Jul;41(7): 888

Eight diseases for gene therapy accelerator.

DOI: https://doi.org/10.1038/s41587-023-01871-z
Adv Protein Chem Struct Biol. 2023 ;pii: S1876-1623(23)00036-6. [Epub ahead of print]136 197-215

Mitochondria-derived peptides in healthy ageing and therapy of age-related diseases.

Siarhei A Dabravolski.

  Mitochondrial-derived peptides (MDPs) are small bioactive peptides encoded by mitochondrial DNA and involved in various stress-protecting mechanisms. To date, eight mitochondrial-derived peptides have been identified: MOTS-c sequence is hidden in the 12 S rRNA gene (MT-RNR1), and the other 7 (humanin and small humanin-like peptides 1-6) are encoded by the 16 S rRNA (MT-RNR2) gene. While the anti-apoptotic, anti-inflammatory and cardioprotective activities of MDPs are well described, recent research suggests that MDPs are sensitive metabolic sensors, closely connected with mtDNA mutation-associated diseases and age-associated metabolic disorders. In this chapter, we focus on the recent progress in understanding the metabolo-protective properties of MDPs, their role in maintenance of the cellular and mitochondrial homeostasis associated with age-related diseases: Alzheimer's disease, cognitive decline, macular degeneration and cataracts. Also, we will discuss MDPs-based and MDPs-targeted interventions to treat age-related diseases and extend a healthy lifespan.

Keywords:  Age-related macular degeneration; Ageing; Alzheimer’s disease; Healthspan; Humanin; Lifespan; MOTS-c; Mitochondria-derived peptides; SHLPs

DOI:  https://doi.org/10.1016/bs.apcsb.2023.02.015
Front Cell Dev Biol. 2023 ;11 1212779

Regulation of mitochondrial morphology and cristae architecture by the TLR4 pathway in human skeletal muscle.

Mauricio Castro-Sepulveda, Mauro Tuñón-Suárez, Giovanni Rosales-Soto, Ronald Vargas-Foitzick, Louise Deldicque, Hermann Zbinden-Foncea.

  In skeletal muscle (SkM), a reduced mitochondrial elongate phenotype is associated with several metabolic disorders like type 2 diabetes mellitus (T2DM). However, the mechanisms contributing to this reduction in mitochondrial elongate phenotype in SkM have not been fully elucidated. It has recently been shown in a SkM cell line that toll-like receptor 4 (TLR4) contributes to the regulation of mitochondrial morphology. However, this has not been investigated in human SkM. Here we found that in human SkM biopsies, TLR4 protein correlated negatively with Opa1 (pro-mitochondrial fusion protein). Moreover, the incubation of human myotubes with LPS reduced mitochondrial size and elongation and induced abnormal mitochondrial cristae, which was prevented with the co-incubation of LPS with TAK242. Finally, T2DM myotubes were found to have reduced mitochondrial elongation and mitochondrial cristae density. Mitochondrial morphology, membrane structure, and insulin-stimulated glucose uptake were restored to healthy levels in T2DM myotubes treated with TAK242. In conclusion, mitochondrial morphology and mitochondrial cristae seem to be regulated by the TLR4 pathway in human SkM. Those mitochondrial alterations might potentially contribute to insulin resistance in the SkM of patients with T2DM.

Keywords:  Lipopolysaccharide; TAK242; mitochondrial dynamics; mitochondrial nanotunnels; skeletal muscle function; type 2 diabetes

DOI:  https://doi.org/10.3389/fcell.2023.1212779
Front Physiol. 2023 ;14 1183101

Duchenne muscular dystrophy: disease mechanism and therapeutic strategies.

Addeli Bez Batti Angulski, Nora Hosny, Houda Cohen, Ashley A Martin, Dongwoo Hahn, Jack Bauer, Joseph M Metzger.

  Duchenne muscular dystrophy (DMD) is a severe, progressive, and ultimately fatal disease of skeletal muscle wasting, respiratory insufficiency, and cardiomyopathy. The identification of the dystrophin gene as central to DMD pathogenesis has led to the understanding of the muscle membrane and the proteins involved in membrane stability as the focal point of the disease. The lessons learned from decades of research in human genetics, biochemistry, and physiology have culminated in establishing the myriad functionalities of dystrophin in striated muscle biology. Here, we review the pathophysiological basis of DMD and discuss recent progress toward the development of therapeutic strategies for DMD that are currently close to or are in human clinical trials. The first section of the review focuses on DMD and the mechanisms contributing to membrane instability, inflammation, and fibrosis. The second section discusses therapeutic strategies currently used to treat DMD. This includes a focus on outlining the strengths and limitations of approaches directed at correcting the genetic defect through dystrophin gene replacement, modification, repair, and/or a range of dystrophin-independent approaches. The final section highlights the different therapeutic strategies for DMD currently in clinical trials.

Keywords:  Duchenne muscular dystrophy; dystrophin; muscle disease; pathophysiology; skeletal muscle; therapeutic strategies

DOI:  https://doi.org/10.3389/fphys.2023.1183101
Nat Cell Biol. 2023 Jul 13.

The Troyer syndrome protein spartin mediates selective autophagy of lipid droplets.

Jeeyun Chung, Joongkyu Park, Zon Weng Lai, Talley J Lambert, Ruth C Richards, Jiuchun Zhang, Tobias C Walther, Robert V Farese.

Lipid droplets (LDs) are crucial organelles for energy storage and lipid homeostasis. Autophagy of LDs is an important pathway for their catabolism, but the molecular mechanisms mediating LD degradation by selective autophagy (lipophagy) are unknown. Here we identify spartin as a receptor localizing to LDs and interacting with core autophagy machinery, and we show that spartin is required to deliver LDs to lysosomes for triglyceride mobilization. Mutations in SPART (encoding spartin) lead to Troyer syndrome, a form of complex hereditary spastic paraplegia1. Interfering with spartin function in cultured human neurons or murine brain neurons leads to LD and triglyceride accumulation. Our identification of spartin as a lipophagy receptor, thus, suggests that impaired LD turnover contributes to Troyer syndrome development.

DOI: https://doi.org/10.1038/s41556-023-01178-w
Cell Death Dis. 2023 Jul 12. 14(7): 413

IF1 ablation prevents ATP synthase oligomerization, enhances mitochondrial ATP turnover and promotes an adenosine-mediated pro-inflammatory phenotype.

Sonia Domínguez-Zorita, Inés Romero-Carramiñana, Fulvio Santacatterina, Pau B Esparza-Moltó, Carolina Simó, Araceli Del-Arco, Cristina Núñez de Arenas, Jorge Saiz, Coral Barbas, José M Cuezva.

ATPase Inhibitory Factor 1 (IF1) regulates the activity of mitochondrial ATP synthase. The expression of IF1 in differentiated human and mouse cells is highly variable. In intestinal cells, the overexpression of IF1 protects against colon inflammation. Herein, we have developed a conditional IF1-knockout mouse model in intestinal epithelium to investigate the role of IF1 in mitochondrial function and tissue homeostasis. The results show that IF1-ablated mice have increased ATP synthase/hydrolase activities, leading to profound mitochondrial dysfunction and a pro-inflammatory phenotype that impairs the permeability of the intestinal barrier compromising mouse survival upon inflammation. Deletion of IF1 prevents the formation of oligomeric assemblies of ATP synthase and alters cristae structure and the electron transport chain. Moreover, lack of IF1 promotes an intramitochondrial Ca2+ overload in vivo, minimizing the threshold to Ca2+-induced permeability transition (mPT). Removal of IF1 in cell lines also prevents the formation of oligomeric assemblies of ATP synthase, minimizing the threshold to Ca2+-induced mPT. Metabolomic analyses of mice serum and colon tissue highlight that IF1 ablation promotes the activation of de novo purine and salvage pathways. Mechanistically, lack of IF1 in cell lines increases ATP synthase/hydrolase activities and installs futile ATP hydrolysis in mitochondria, resulting in the activation of purine metabolism and in the accumulation of adenosine, both in culture medium and in mice serum. Adenosine, through ADORA2B receptors, promotes an autoimmune phenotype in mice, stressing the role of the IF1/ATP synthase axis in tissue immune responses. Overall, the results highlight that IF1 is required for ATP synthase oligomerization and that it acts as a brake to prevent ATP hydrolysis under in vivo phosphorylating conditions in intestinal cells.

DOI: https://doi.org/10.1038/s41419-023-05957-z
Methods Mol Biol. 2023 ;2685 331-349

Mitochondrial DNA Analysis.

Ashley M Cooley.

  Mitochondrial DNA (mtDNA) is a 16,569 base pair (bp) circular genome that is passed from generation to generation through the maternal line. mtDNA analysis in the context of the forensic science field usually involves unidentified human remains or missing persons. These cases tend to have more challenging sample types (e.g., rootless hairs, bone, blood, and saliva), and mtDNA analysis can be an additional method to assist in identification efforts. Due to the multifaceted protection of mtDNA within cells, mtDNA is able to be extracted even in cases of extreme degradation. mtDNA analysis for forensic science has been both peer-reviewed in academic journals and has been testified to in criminal court procedures since the late 1990s, allowing for consistent and reliable usage in casework. This chapter describes the general methodology of extracting, amplifying, quantifying, and analyzing an mtDNA sequence for use in forensic casework, specifically for these common items of evidence.

Keywords:  Bone analysis; DNA sequencing; DNA typing; Forensic DNA analysis; Forensic science; Hair analysis; Mitochondrial DNA

DOI:  https://doi.org/10.1007/978-1-0716-3295-6_20
Front Mol Neurosci. 2023 ;16 1209760

Disruption of mitochondrial and lysosomal functions by human CACNA1C variants expressed in HEK 293 and CHO cells.

Miriam Kessi, Baiyu Chen, Langui Pan, Li Yang, Lifen Yang, Jing Peng, Fang He, Fei Yin.

   Objective: To investigate the pathogenesis of three novel de novo CACNA1C variants (p.E411D, p.V622G, and p.A272V) in causing neurodevelopmental disorders and arrhythmia.
Methods: Several molecular experiments were carried out on transfected human embryonic kidney 293 (HEK 293) and Chinese hamster ovary (CHO) cells to explore the effects of p.E411D, p.V622G, and p.A272V variants on electrophysiology, mitochondrial and lysosomal functions. Electrophysiological studies, RT-qPCR, western blot, apoptosis assay, mito-tracker fluorescence intensity, lyso-tracker fluorescence intensity, mitochondrial calcium concentration test, and cell viability assay were performed. Besides, reactive oxygen species (ROS) levels, ATP levels, mitochondrial copy numbers, mitochondrial complex I, II, and cytochrome c functions were measured.
Results: The p.E411D variant was found in a patient with attention deficit-hyperactive disorder (ADHD), and moderate intellectual disability (ID). This mutant demonstrated reduced calcium current density, mRNA, and protein expression, and it was localized in the nucleus, cytoplasm, lysosome, and mitochondria. It exhibited an accelerated apoptosis rate, impaired autophagy, and mitophagy. It also demonstrated compromised mitochondrial cytochrome c oxidase, complex I, and II enzymes, abnormal mitochondrial copy numbers, low ATP levels, abnormal mitochondria fluorescence intensity, impaired mitochondrial fusion and fission, and elevated mitochondrial calcium ions. The p.V622G variant was identified in a patient who presented with West syndrome and moderate global developmental delay. The p.A272V variant was found in a patient who presented with epilepsy and mild ID. Both mutants (p.V622G and p.A272V) exhibited reduced calcium current densities, decreased mRNA and protein expressions, and they were localized in the nucleus, cytoplasm, lysosome, and mitochondria. They exhibited accelerated apoptosis and proliferation rates, impaired autophagy, and mitophagy. They also exhibited abnormal mitochondrial cytochrome c oxidase, complex I and II enzymes, abnormal mitochondrial copy numbers, low ATP, high ROS levels, abnormal mitochondria fluorescence intensity, impaired mitochondrial fusion and fission, as well as elevated mitochondrial calcium ions.
Conclusion: The p.E411D, p.V622G and p.A272V mutations of human CACNA1C reduce the expression level of CACNA1C proteins, and impair mitochondrial and lysosomal functions. These effects induced by CACNA1C variants may contribute to the pathogenesis of CACNA1C-related disorders.

Keywords:  CACNA1C; loss of calcium current density; lysosomal dysfunction; mitochondrial dysfunction; mitochondrial fission; mitochondrial fusion; mitophagy; molecular mechanisms

DOI:  https://doi.org/10.3389/fnmol.2023.1209760
J Biol Chem. 2023 Jul 12. pii: S0021-9258(23)02075-6. [Epub ahead of print] 105047

Maintenance of cellular vitamin B6 levels and mitochondrial oxidative function depend on pyridoxal 5'-phosphate homeostasis protein (PLPHP).

Jolita Ciapaite, Carlo W T van Roermund, Marjolein Bosma, Johan Gerrits, Sander M Houten, Lodewijk IJlst, Hans R Waterham, Clara D M van Karnebeek, Ronald J A Wanders, Fried J T Zwartkruis, Judith J Jans, Nanda M Verhoeven-Duif.

  Recently, biallelic variants in PLPBP coding for pyridoxal 5'-phosphate homeostasis protein (PLPHP) were identified as a novel cause of early-onset vitamin B6-dependent epilepsy. The molecular function and precise role of PLPHP in vitamin B6 metabolism are not well understood. To address these questions we used PLPHP deficient patient skin fibroblasts and HEK293 cells, and YBL036C (PLPHP ortholog) deficient yeast. We showed that independent of extracellular B6 vitamer type (pyridoxine, pyridoxamine or pyridoxal), intracellular PLP was lower in PLPHP deficient fibroblasts and HEK293 cells compared to controls. Culturing cells with pyridoxine or pyridoxamine led to the concentration-dependent accumulation of pyridoxine 5'-phosphate and pyridoxamine 5'-phosphate (PMP), respectively, suggesting insufficient pyridox(am)ine 5'-phosphate oxidase (PNPO) activity. Experiments utilizing 13C4-pyridoxine confirmed lower PNPO activity and revealed increased fractional turnovers of PLP and pyridoxal, indicating increased PLP hydrolysis to pyridoxal in PLPHP deficient cells. This effect could be partly counteracted by inactivation of pyridoxal phosphatase. PLPHP deficiency had a distinct effect on mitochondrial PLP and PMP, suggesting impaired activity of mitochondrial transaminases. Moreover, in YBL036C deficient yeast PLP was depleted and PMP accumulated only with carbon sources requiring mitochondrial metabolism. Lactate and pyruvate accumulation along with the decrease of tricarboxylic acid cycle intermediates downstream of α-ketoglutarate suggested impaired mitochondrial oxidative metabolism in PLPHP deficient HEK293 cells. We hypothesize that impaired activity of mitochondrial transaminases may contribute to this depletion. Taken together, our study provides new insights into the pathomechanisms of PLPBP deficiency and reinforces the link between PLPHP function, vitamin B6 metabolism and mitochondrial oxidative metabolism.

Keywords:  Pyridoxal 5’-phosphate homeostasis protein PLPHP (PROSC); mitochondrial dysfunction; pyridox(am)ine 5′-phosphate oxidase (PNPO); transaminases; vitamin B(6) metabolism; α-ketoglutarate

DOI:  https://doi.org/10.1016/j.jbc.2023.105047
Cell Rep. 2023 Jul 11. pii: S2211-1247(23)00739-8. [Epub ahead of print]42(7): 112728

Mitochondria-derived cell-to-cell communication.

Zahra Al Amir Dache, Alain R Thierry.

  In addition to their intracellular mobility, mitochondria and their components can exist outside the cells from which they originate. As a result, they are capable of acting on non-parental distant cells and mediate intercellular communication in physiological conditions and in a variety of pathologies. It has recently been demonstrated that this horizontal transfer governs a wide range of biological processes, such as tissue homeostasis, the rescue of injured recipient cells, and tumorigenesis. In addition, due to mitochondria's bacterial ancestry, they and their components can be recognized as damage-associated molecular patterns (DAMPs) by the immune cells, leading to inflammation. Here, we provide an overview of the most current and significant findings concerning the different structures of extracellular mitochondria and their by-products and their functions in the physiological and pathological context. This account illustrates the ongoing expansion of our understanding of mitochondria's biological role and functions in mammalian organisms.

Keywords:  CP: Cell biology; DAMP; circulating DNA; circulating mitochondria; inflammation; intercellular communication; mitochondria

DOI:  https://doi.org/10.1016/j.celrep.2023.112728
Pediatr Nephrol. 2023 Jul 14.

Hyporeninemic hypoaldosteronism in RMND1-related mitochondrial disease.

Martin Kömhoff, Valentina Gracchi, Henry Dijkman, Bodo B Beck, Leo Monnens.

   BACKGROUND: RMND1 is a nuclear gene needed for proper function of mitochondria. A pathogenic gene will cause multiple oxidative phosphorylation defects. A renal phenotype consisting of hyponatremia, hyperkalemia, and acidosis is frequently reported, previously considered to be due to aldosterone insensitivity.
METHODS: Clinical features and pathophysiology of three patients will be reported. DNA of these patients was subjected to exome screening.
RESULTS: In the first family, one pathogenic heterozygous and one highly probable heterozygous mutation were detected. In the second family, a homozygous pathogenic mutation was present. The electrolyte disbalance was not due to aldosterone insensitivity but to low plasma aldosterone concentration, a consequence of low plasma renin activity. This disbalance can be treated. In all three patients, the kidney function declined. In the first family, both children suffered from an unexplained arterial thrombosis with dire consequences.
CONCLUSIONS: Hyporeninemic hypoaldosteronism is the mechanism causing the electrolyte disbalance reported in patients with RMND1 mutations, and can be treated.

Keywords:  Hyporeninemic hypoaldosteronism; Inherited renal disease; Mitochondrial dysfunction; RMND1 mutations

DOI:  https://doi.org/10.1007/s00467-023-06079-6
Cells. 2023 Jun 27. pii: 1726. [Epub ahead of print]12(13):

The Highs and Lows of Memantine-An Autophagy and Mitophagy Inducing Agent That Protects Mitochondria.

Sholto de Wet, Asandile Mangali, Richard Batt, Jurgen Kriel, Nicola Vahrmeijer, Dana Niehaus, Rensu Theart, Ben Loos.

  Memantine is an FDA-approved, non-competitive NMDA-receptor antagonist that has been shown to have mitochondrial protective effects, improve cell viability and enhance clearance of Aβ42 peptide. Currently, there are uncertainties regarding the precise molecular targets as well as the most favourable treatment concentrations of memantine. Here, we made use of an imaging-based approach to investigate the concentration-dependent effects of memantine on mitochondrial fission and fusion dynamics, autophagy and mitochondrial quality control using a neuronal model of CCCP-induced mitochondrial injury so as to better unpack how memantine aids in promoting neuronal health. GT1-7 murine hypothalamic cells were cultured under standard conditions, treated with a relatively high and low concentration (100 µM and 50 µM) of memantine for 48 h. Images were acquired using a Zeiss 780 PS1 platform. Utilising the mitochondrial event localiser (MEL), we demonstrated clear concentration-dependent effects of memantine causing a protective response to mitochondrial injury. Both concentrations maintained the mitochondrial network volume whilst the low concentration caused an increase in mitochondrial number as well as increased fission and fusion events following CCCP-induced injury. Additionally, we made use of a customised Python-based image processing and analysis pipeline to quantitatively assess memantine-dependent changes in the autophagosomal and lysosomal compartments. Our results revealed that memantine elicits a differential, concentration-dependent effect on autophagy pathway intermediates. Intriguingly, low but not high concentrations of memantine lead to the induction of mitophagy. Taken together, our findings have shown that memantine is able to protect the mitochondrial network by preserving its volume upon mitochondrial injury with high concentrations of memantine inducing macroautophagy, whereas low concentrations lead to the induction of mitophagy.

Keywords:  autophagy; mitochondrial dynamics; mitochondrial function; mitophagy; proteostasis

DOI:  https://doi.org/10.3390/cells12131726
J Cereb Blood Flow Metab. 2023 Feb 22. 271678X231156500

NAD+ precursor nutritional supplements sensitize the brain to future ischemic events.

Wensheng Qu, Kenneth M Ralto, Tao Qin, Yinhong Cheng, Weifeng Zong, Xiang Luo, Miguel Perez-Pinzon, Samir M Parikh, Cenk Ayata.

  Nicotinamide adenine dinucleotide (NAD+) is a redox cofactor critical for oxidative phosphorylation. Nicotinamide (NAM) and nicotinamide riboside (NR) are NAD+ precursors widely used as nutritional supplements to augment oxidative phosphorylation. Indeed, NAD+ precursors have been reported to improve outcomes in ischemic stroke when administered as a rescue therapy after stroke onset. However, we have also reported that enhanced reliance on oxidative phosphorylation before ischemia onset might worsen outcomes. To address the paradox, we examined how NAD+ precursors modulate the outcome of middle cerebral artery occlusion in mice, when administered either 20 minutes after reperfusion or daily for three days before ischemia onset. A single post-ischemic dose of NAM or NR indeed improved tissue and neurologic outcomes examined at 72 hours. In contrast, pre-ischemic treatment for three days enlarged the infarcts and worsened neurological deficits. As a possible explanation for the diametric outcomes, a single dose of NAM or NR augmented tissue AMPK, PGC1α, SIRT1, and ATP in both naïve and ischemic brains, while the multiple-dose paradigm failed to do so. Our data suggest that NAD+ precursor supplements may sensitize the brain to subsequent ischemic events, despite their neuroprotective effect when administered after ischemia onset.

Keywords:  Cerebral ischemia; nicotinamide adenine dinucleotide; oxidative phosphorylation; proliferator-activated receptor-γ coactivator 1; sirtuin-1

DOI:  https://doi.org/10.1177/0271678X231156500
JCI Insight. 2023 Jul 11. pii: e166888. [Epub ahead of print]

Glutathione limits RUNX2 oxidation and degradation to regulate bone formation.

Guoli Hu, Yilin Yu, Deepika Sharma, Shondra M Pruett-Miller, Yinshi Ren, Guo-Fang Zhang, Courtney M Karner.

  Reactive oxygen species (ROS) are natural products of mitochondrial oxidative metabolism and oxidative protein folding. ROS levels must be well controlled as elevated ROS has been shown to have deleterious effects on osteoblasts. Moreover, excessive ROS is thought to underly many of the skeletal phenotypes associated with aging and sex steroid deficiency in mice and humans. The mechanisms by which osteoblasts regulate ROS and how ROS inhibits osteoblasts are not well understood. Here, we demonstrate that de novo glutathione (GSH) biosynthesis is essential to neutralize ROS and establish a pro-osteogenic REDOX environment. Using a multifaceted approach, we demonstrate that reducing GSH biosynthesis leads to acute degradation of RUNX2, impaired osteoblast differentiation and reduced bone formation. Conversely, reducing ROS using Catalase enhances RUNX2 stability and promotes osteoblast differentiation and bone formation when GSH biosynthesis is limited. Highlighting the therapeutic implications of these findings, in utero antioxidant therapy stabilizes RUNX2 and improves bone development in the Runx2+/- haploinsufficient mouse model of human Cleidocranial Dysplasia. Thus, our data establish RUNX2 as a molecular sensor of the osteoblast REDOX environment and mechanistically clarifies how ROS negatively impacts osteoblast differentiation and bone formation.

Keywords:  Amino acid metabolism; Bone Biology; Bone development; Osteoclast/osteoblast biology

DOI:  https://doi.org/10.1172/jci.insight.166888
Int J Mol Sci. 2023 Jun 30. pii: 10973. [Epub ahead of print]24(13):

Pathophysiology of Cerebellar Degeneration in Mitochondrial Disorders: Insights from the Harlequin Mouse.

Miguel Fernández de la Torre, Carmen Fiuza-Luces, Sara Laine-Menéndez, Aitor Delmiro, Joaquín Arenas, Miguel Ángel Martín, Alejandro Lucia, María Morán.

  By means of a proteomic approach, we assessed the pathways involved in cerebellar neurodegeneration in a mouse model (Harlequin, Hq) of mitochondrial disorder. A differential proteomic profile study (iTRAQ) was performed in cerebellum homogenates of male Hq and wild-type (WT) mice 8 weeks after the onset of clear symptoms of ataxia in the Hq mice (aged 5.2 ± 0.2 and 5.3 ± 0.1 months for WT and Hq, respectively), followed by a biochemical validation of the most relevant changes. Additional groups of 2-, 3- and 6-month-old WT and Hq mice were analyzed to assess the disease progression on the proteins altered in the proteomic study. The proteomic analysis showed that beyond the expected deregulation of oxidative phosphorylation, the cerebellum of Hq mice showed a marked astroglial activation together with alterations in Ca2+ homeostasis and neurotransmission, with an up- and downregulation of GABAergic and glutamatergic neurotransmission, respectively, and the downregulation of cerebellar "long-term depression", a synaptic plasticity phenomenon that is a major player in the error-driven learning that occurs in the cerebellar cortex. Our study provides novel insights into the mechanisms associated with cerebellar degeneration in the Hq mouse model, including a complex deregulation of neuroinflammation, oxidative phosphorylation and glutamate, GABA and amino acids' metabolism.

Keywords:  GABA; Harlequin mouse; OXPHOS disorders; ataxia; complex I; glutamate; long-term depression; mitochondrial diseases

DOI:  https://doi.org/10.3390/ijms241310973
Cell Metab. 2023 Jul 11. pii: S1550-4131(23)00217-6. [Epub ahead of print]35(7): 1195-1208.e6

Fetal manipulation of maternal metabolism is a critical function of the imprinted Igf2 gene.

Jorge Lopez-Tello, Hannah E J Yong, Ionel Sandovici, Georgina K C Dowsett, Efthimia R Christoforou, Esteban Salazar-Petres, Rebecca Boyland, Tina Napso, Giles S H Yeo, Brian Y H Lam, Miguel Constancia, Amanda N Sferruzzi-Perri.

  Maternal-offspring interactions in mammals involve both cooperation and conflict. The fetus has evolved ways to manipulate maternal physiology to enhance placental nutrient transfer, but the mechanisms involved remain unclear. The imprinted Igf2 gene is highly expressed in murine placental endocrine cells. Here, we show that Igf2 deletion in these cells impairs placental endocrine signaling to the mother, without affecting placental morphology. Igf2 controls placental hormone production, including prolactins, and is crucial to establish pregnancy-related insulin resistance and to partition nutrients to the fetus. Consequently, fetuses lacking placental endocrine Igf2 are growth restricted and hypoglycemic. Mechanistically, Igf2 controls protein synthesis and cellular energy homeostasis, actions dependent on the placental endocrine cell type. Igf2 loss also has additional long-lasting effects on offspring metabolism in adulthood. Our study provides compelling evidence for an intrinsic fetal manipulation system operating in placenta that modifies maternal metabolism and fetal resource allocation, with long-term consequences for offspring metabolic health.

Keywords:  fetal programming; genomic imprinting; glucose; hormones; insulin-like growth factor 2; metabolism; placenta; pregnancy; prolactin

DOI:  https://doi.org/10.1016/j.cmet.2023.06.007
Nature. 2023 Jul 12.

A framework for individualized splice-switching oligonucleotide therapy.

Jinkuk Kim, Sijae Woo, Claudio M de Gusmao, Boxun Zhao, Diana H Chin, Renata L DiDonato, Minh A Nguyen, Tojo Nakayama, Chunguang April Hu, Aubrie Soucy, Ashley Kuniholm, Jennifer Karlin Thornton, Olivia Riccardi, Danielle A Friedman, Christelle Moufawad El Achkar, Zane Dash, Laura Cornelissen, Carolina Donado, Kamli N W Faour, Lynn W Bush, Victoria Suslovitch, Claudia Lentucci, Peter J Park, Eunjung Alice Lee, Al Patterson, Anthony A Philippakis, Brad Margus, Charles B Berde, Timothy W Yu.

Splice-switching antisense oligonucleotides (ASOs) could be used to treat a subset of individuals with genetic diseases1, but the systematic identification of such individuals remains a challenge. Here we performed whole-genome sequencing analyses to characterize genetic variation in 235 individuals (from 209 families) with ataxia-telangiectasia, a severely debilitating and life-threatening recessive genetic disorder2,3, yielding a complete molecular diagnosis in almost all individuals. We developed a predictive taxonomy to assess the amenability of each individual to splice-switching ASO intervention; 9% and 6% of the individuals had variants that were 'probably' or 'possibly' amenable to ASO splice modulation, respectively. Most amenable variants were in deep intronic regions that are inaccessible to exon-targeted sequencing. We developed ASOs that successfully rescued mis-splicing and ATM cellular signalling in patient fibroblasts for two recurrent variants. In a pilot clinical study, one of these ASOs was used to treat a child who had been diagnosed with ataxia-telangiectasia soon after birth, and showed good tolerability without serious adverse events for three years. Our study provides a framework for the prospective identification of individuals with genetic diseases who might benefit from a therapeutic approach involving splice-switching ASOs.

DOI: https://doi.org/10.1038/s41586-023-06277-0
Kidney Res Clin Pract. 2023 May 22.

Mitochondrial quality control and its emerging role in the pathogenesis of diabetic kidney disease.

Jihyun Baek, Yu Ho Lee, Hye Yun Jeong, So-Young Lee.

  Most eukaryotic cells have mitochondrial networks that can change in shape, distribution, and size depending on cellular metabolic demands and environments. Mitochondrial quality control is critical for various mitochondrial functions including energy production, redox homeostasis, intracellular calcium handling, cell differentiation, proliferation, and cell death. Quality control mechanisms within mitochondria consist of antioxidant defenses, protein quality control, DNA damage repair systems, mitochondrial fusion and fission, mitophagy, and mitochondrial biogenesis. Defects in mitochondrial quality control and disruption of mitochondrial homeostasis are common characteristics of various kidney cell types under hyperglycemic conditions. Such defects contribute to diabetes-induced pathologies in renal tubular cells, podocytes, endothelial cells, and immune cells. In this review, we focus on the roles of mitochondrial quality control in diabetic kidney disease pathogenesis and discuss current research evidence and future directions.

Keywords:  Diabetic kidney disease; Endothelial cells; Immune cells; Mitochondrial quality control; Podocytes; Renal tubular cells

DOI:  https://doi.org/10.23876/j.krcp.22.233
Aging Cell. 2023 Jul 09. e13920

NAD metabolism: Role in senescence regulation and aging.

Claudia Christiano Silva Chini, Heidi Soares Cordeiro, Ngan Le Kim Tran, Eduardo Nunes Chini.

  The geroscience hypothesis proposes that addressing the biology of aging could directly prevent the onset or mitigate the severity of multiple chronic diseases. Understanding the interplay between key aspects of the biological hallmarks of aging is essential in delivering the promises of the geroscience hypothesis. Notably, the nucleotide nicotinamide adenine dinucleotide (NAD) interfaces with several biological hallmarks of aging, including cellular senescence, and changes in NAD metabolism have been shown to be involved in the aging process. The relationship between NAD metabolism and cellular senescence appears to be complex. On the one hand, the accumulation of DNA damage and mitochondrial dysfunction induced by low NAD+ can promote the development of senescence. On the other hand, the low NAD+ state that occurs during aging may inhibit SASP development as this secretory phenotype and the development of cellular senescence are both highly metabolically demanding. However, to date, the impact of NAD+ metabolism on the progression of the cellular senescence phenotype has not been fully characterized. Therefore, to explore the implications of NAD metabolism and NAD replacement therapies, it is essential to consider their interactions with other hallmarks of aging, including cellular senescence. We propose that a comprehensive understanding of the interplay between NAD boosting strategies and senolytic agents is necessary to advance the field.

Keywords:  NAD+ metabolism; SASP; aging; nicotinamide adenine dinucleotide; senescence

DOI:  https://doi.org/10.1111/acel.13920
J Vis Exp. 2023 06 23.

High-Resolution Respirometry to Assess Mitochondrial Function in Human Spermatozoa.

Pilar Irigoyen, Rossana Sapiro, Adriana Cassina.

Semen quality is often studied by routine semen analysis, which is descriptive and often inconclusive. Male infertility is associated with altered sperm mitochondrial activity, so the measurement of sperm mitochondrial function is an indicator of sperm quality. High-resolution respirometry is a method of measuring the oxygen consumption of cells or tissues in a closed-chamber system. This technique can be implemented to measure respiration in human sperm and provides information about the quality and integrity of the sperm mitochondria. High-resolution respirometry allows the cells to move freely, which is an a priori advantage in the case of sperm. This technique can be applied with intact or permeabilized spermatozoa and allows for the study of intact sperm mitochondrial function and the activity of individual respiratory chain complexes. The high-resolution oxygraph instrument uses sensors to measure the oxygen concentration coupled with sensitive software to calculate the oxygen consumption. The data are used to calculate respiratory indices based on the oxygen consumption ratios. Consequently, the indices are the proportions of two oxygen consumption rates and are internally normalized to the cell number or protein mass. The respiratory indices are an indicator of sperm mitochondrial function and dysfunction.

DOI: https://doi.org/10.3791/65493
J Biol Chem. 2023 Jul 08. pii: S0021-9258(23)02003-3. [Epub ahead of print] 104975

NAD metabolism modulates inflammation and mitochondria function in diabetic kidney disease.

Komuraiah Myakala, Xiaoxin X Wang, Nataliia V Shults, Ewa Krawczyk, Bryce A Jones, Xiaoping Yang, Avi Z Rosenberg, Brandon Ginley, Pinaki Sarder, Leonid Brodsky, Yura Jang, Chan Hyun Na, Yue Qi, Xu Zhang, Udayan Guha, Ci Wu, Shivani Bansal, Junfeng Ma, Amrita Cheema, Chris Albanese, Matthew D Hirschey, Teruhiko Yoshida, Jeffrey B Kopp, Julia Panov, Moshe Levi.

Diabetes mellitus is the leading cause of cardiovascular and renal disease in the United -States. In spite of the beneficial interventions available for patients with diabetes, there remains a need for additional therapeutic targets and therapies in diabetic kidney disease (DKD). Inflammation and oxidative stress are increasingly recognized as important causes of renal diseases. Inflammation is closely associated with mitochondrial damage. The molecular connection between inflammation and mitochondrial metabolism remains to be elucidated. Recently, nicotinamide adenine nucleotide (NAD+) metabolism has been found to regulate immune function and inflammation. In the present studies we tested the hypothesis that enhancing NAD metabolism could prevent inflammation in and progression of DKD. We found that treatment of db/db mice with type 2 diabetes with nicotinamide riboside (NR) prevented several manifestations of kidney dysfunction (i.e., albuminuria, increased urinary kidney injury marker-1 (KIM1) excretion and pathologic changes). These effects were associated with decreased inflammation, at least in part via inhibiting the activation of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling pathway. An antagonist of the serum stimulator of interferon genes (STING) and whole-body STING deletion in diabetic mice showed similar renoprotection. Further analysis found that NR increased SIRT3 activity and improved mitochondrial function, which led to decreased mitochondrial DNA damage, a trigger for mitochondrial DNA leakage which activates the cGAS-STING pathway. Overall, these data show that NR supplementation boosted NAD metabolism to augment mitochondrial function, reducing inflammation and thereby preventing progression of diabetic kidney disease.

DOI: https://doi.org/10.1016/j.jbc.2023.104975
Cell Rep. 2023 Jul 07. pii: S2211-1247(23)00746-5. [Epub ahead of print]42(7): 112735

Increased mitochondrial free Ca2+ during ischemia is suppressed, but not eliminated by, germline deletion of the mitochondrial Ca2+ uniporter.

Courtney E Petersen, Junhui Sun, Kavisha Silva, Anna Kosmach, Robert S Balaban, Elizabeth Murphy.

  Mitochondrial Ca2+ overload is proposed to regulate cell death via opening of the mitochondrial permeability transition pore. It is hypothesized that inhibition of the mitochondrial Ca2+ uniporter (MCU) will prevent Ca2+ accumulation during ischemia/reperfusion and thereby reduce cell death. To address this, we evaluate mitochondrial Ca2+ in ex-vivo-perfused hearts from germline MCU-knockout (KO) and wild-type (WT) mice using transmural spectroscopy. Matrix Ca2+ levels are measured with a genetically encoded, red fluorescent Ca2+ indicator (R-GECO1) using an adeno-associated viral vector (AAV9) for delivery. Due to the pH sensitivity of R-GECO1 and the known fall in pH during ischemia, hearts are glycogen depleted to decrease the ischemic fall in pH. At 20 min of ischemia, there is significantly less mitochondrial Ca2+ in MCU-KO hearts compared with MCU-WT controls. However, an increase in mitochondrial Ca2+ is present in MCU-KO hearts, suggesting that mitochondrial Ca2+ overload during ischemia is not solely dependent on MCU.

Keywords:  CP: Developmental biology; MCU; calcium; cardioprotection; ischemia-reperfusion; mitochondria

DOI:  https://doi.org/10.1016/j.celrep.2023.112735
Cell Rep. 2023 Jul 11. pii: S2211-1247(23)00787-8. [Epub ahead of print]42(7): 112776

Mitofusin-2 in nucleus accumbens D2-MSNs regulates social dominance and neuronal function.

Sriparna Ghosal, Elias Gebara, Eva Ramos-Fernández, Alessandro Chioino, Jocelyn Grosse, Isabelle Guillot de Suduiraut, Olivia Zanoletti, Bernard Schneider, Antonio Zorzano, Simone Astori, Carmen Sandi.

  The nucleus accumbens (NAc) is a brain hub regulating motivated behaviors, including social competitiveness. Mitochondrial function in the NAc links anxiety with social competitiveness, and the mitochondrial fusion protein mitofusin 2 (Mfn2) in NAc neurons regulates anxiety-related behaviors. However, it remains unexplored whether accumbal Mfn2 levels also affect social behavior and whether Mfn2 actions in the emotional and social domain are driven by distinct cell types. Here, we found that subordinate-prone highly anxious rats show decreased accumbal Mfn2 levels and that Mfn2 overexpression promotes dominant behavior. In mice, selective Mfn2 downregulation in NAc dopamine D2 receptor-expressing medium spiny neurons (D2-MSNs) induced social subordination, accompanied by decreased accumbal mitochondrial functions and decreased excitability in D2-MSNs. Instead, D1-MSN-targeted Mfn2 downregulation affected competitive ability only transiently and likely because of an increase in anxiety-like behaviors. Our results assign dissociable cell-type specific roles to Mfn2 in the NAc in modulating social dominance and anxiety.

Keywords:  CP: Neuroscience; anxiety; medium spiny neurons; mitochondria; mitofusin 2; motivation; nucleus accumbens; social competition; social dominance; tube test

DOI:  https://doi.org/10.1016/j.celrep.2023.112776
Autophagy. 2023 Jul 13. 1-17

Tethering ATG16L1 or LC3 induces targeted autophagic degradation of protein aggregates and mitochondria.

Ligang Mei, Xiaorong Chen, Fujing Wei, Xue Huang, Lu Liu, Jia Yao, Jing Chen, Xunguang Luo, Zhuolin Wang, Aimin Yang.

  Proteolysis-targeting chimeras (PROTACs) based on the ubiquitin-proteasome system have made great progress in the field of drug discovery. There is mounting evidence that the accumulation of aggregation-prone proteins or malfunctioning organelles is associated with the occurrence of various age-related neurodegenerative disorders and cancers. However, PROTACs are inefficient for the degradation of such large targets due to the narrow entrance channel of the proteasome. Macroautophagy (hereafter referred to as autophagy) is known as a self-degradative process involved in the degradation of bulk cytoplasmic components or specific cargoes that are sequestered into autophagosomes. In the present study, we report the development of a generalizable strategy for the targeted degradation of large targets. Our results suggested that tethering large target models to phagophore-associated ATG16L1 or LC3 induced targeted autophagic degradation of the large target models. Furthermore, we successfully applied this autophagy-targeting degradation strategy to the targeted degradation of HTT65Q aggregates and mitochondria. Specifically, chimeras consisting of polyQ-binding peptide 1 (QBP) and ATG16L1-binding peptide (ABP) or LC3-interacting region (LIR) induced targeted autophagic degradation of pathogenic HTT65Q aggregates; and the chimeras consisting of mitochondria-targeting sequence (MTS) and ABP or LIR promoted targeted autophagic degradation of dysfunctional mitochondria, hence ameliorating mitochondrial dysfunction in a Parkinson disease cell model and protecting cells from apoptosis induced by the mitochondrial stress agent FCCP. Therefore, this study provides a new strategy for the selective proteolysis of large targets and enrich the toolkit for autophagy-targeting degradation.Abbreviations: ABP: ATG16L1-binding peptide; ATG16L1: autophagy related 16 like 1; ATTEC: autophagy-tethering compound; AUTAC: autophagy-targeting chimera; AUTOTAC: autophagy-targeting chimera; Baf A1: bafilomycin A1; BCL2: BCL2 apoptosis regulator; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CPP: cell-penetrating peptide; CQ: chloroquine phosphate; DAPI: 4',6-diamidino-2-phenylindole; DCM: dichloromethane; DMF: N,N-dimethylformamide; DMSO: dimethyl sulfoxide; EBSS: Earle's balanced salt solution; FCCP: carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone; FITC: fluorescein-5-isothiocyanate; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; HEK293: human embryonic kidney 293; HEK293T: human embryonic kidney 293T; HPLC: high-performance liquid chromatography; HRP: horseradish peroxidase; HTT: huntingtin; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFF: mitochondrial fission factor; MTS: mitochondria-targeting sequence; NBR1: NBR1 autophagy cargo receptor; NLRX1: NLR family member X1; OPTN: optineurin; P2A: self-cleaving 2A peptide; PB1: Phox and Bem1p; PBS: phosphate-buffered saline; PE: phosphatidylethanolamine; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; PROTACs: proteolysis-targeting chimeras; QBP: polyQ-binding peptide 1; SBP: streptavidin-binding peptide; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SPATA33: spermatogenesis associated 33; TIMM23: translocase of inner mitochondrial membrane 23; TMEM59: transmembrane protein 59; TOMM20: translocase of outer mitochondrial membrane 20; UBA: ubiquitin-associated; WT: wild type.

Keywords:  ATG16L1; HTT65Q aggregates; LC3; autophagy-targeting degradation; mitochondria; proteolysis-targeting chimeras

DOI:  https://doi.org/10.1080/15548627.2023.2234797
Nat Metab. 2023 Jul 10.

TCA cycle deficiency in multiple sclerosis.

Swadha Mishra, Fabian den Brave, Thomas Becker.

DOI: https://doi.org/10.1038/s42255-023-00840-9
EMBO J. 2023 Jul 10. e114415

Cell fragmentation in mouse preimplantation embryos induced by ectopic activation of the polar body extrusion pathway.

Diane Pelzer, Ludmilla de Plater, Peta Bradbury, Adrien Eichmuller, Anne Bourdais, Guillaume Halet, Jean-Léon Maître.

  Cell fragmentation is commonly observed in human preimplantation embryos and is associated with poor prognosis during assisted reproductive technology (ART) procedures. However, the mechanisms leading to cell fragmentation remain largely unknown. Here, light sheet microscopy imaging of mouse embryos reveals that inefficient chromosome separation due to spindle defects, caused by dysfunctional molecular motors Myo1c or dynein, leads to fragmentation during mitosis. Extended exposure of the cell cortex to chromosomes locally triggers actomyosin contractility and pinches off cell fragments. This process is reminiscent of meiosis, during which small GTPase-mediated signals from chromosomes coordinate polar body extrusion (PBE) by actomyosin contraction. By interfering with the signals driving PBE, we find that this meiotic signaling pathway remains active during cleavage stages and is both required and sufficient to trigger fragmentation. Together, we find that fragmentation happens in mitosis after ectopic activation of actomyosin contractility by signals emanating from DNA, similar to those observed during meiosis. Our study uncovers the mechanisms underlying fragmentation in preimplantation embryos and, more generally, offers insight into the regulation of mitosis during the maternal-zygotic transition.

Keywords:  cytoskeleton; meiosis; mitosis; morphogenesis; preimplantation development

DOI:  https://doi.org/10.15252/embj.2023114415